National Educators' 

Workshop: Update 91 

Standard Experiments in Engineering 

Materials Science and Technology 

(NASA-CP-3151) NATIONAL EDUCATORS' N92-3026: 

WORKSHOP: UPDATE 1991. STANDARD --THRU-- 

EXPERIMENTS IN ENGINEERING N92-30291 

MATERIALS SCIENCE AND TECHNOLOGY Uncl as 

(NASA) 369 p 
NASA Conference Publication 3151 

Standard Experiments in Engineering 

Materials Science and Technolo& 

Compiled by 

James E. Gardner 

NASA Langley Research Center 

Hampton, Virginia 

James A. Jacobs 

Norfolk State University 

Norfolk, Virginia 

James 0. Stiegler 

Oak Ridge National Laboratory 

Martin Marietta Energy Systems, Inc. 

Oak Ridge, Tennessee 

Proceedings of a workshop sponsored jointly by the 

United States Department of Energy, the Norfolk State 

University, the National Institute of Standards & 

Technology, and the National Aeronautics and 

Space Administration, and held in 

Oak Ridge, Tennessee 

November 12-14, 199 1 

National Aeronautics and 

Space Administration 

Off ice of Management 

Scientific and Technical 

Information Program 

PREFACE 

NEW:Update 91 was held November 12-14, 1991, at Oak Ridge National Laboratory (ORTJL) in Oak 

Ridge, Tennessee. As with previous workshops, the theme was strengthening materials education. 

Participants witnessed demonstrations of experiments, discussed issues of materials science and 

engineering (MS&E) with people from education, industry, government, and technical societies, heard 

about new MS&E developments, and toured state-of-the-art ORNL laboratories. For the first time, 

concurrent sessions were held in order to accommodate all of the demonstrations of experiments. Faculty 

in attendance represented community colleges, smaller colleges, and major universities. Some were the 

only materials educators on their campus, while others were from well established MS&E programs. 

NEW:Update 91 marked the sixth annual National Educators' W0rkshop:Update. Eighty participants, 

including first time attendees and those who attended previous New:Updates, aided in evaluating nearly 

thirty-three experiments that were presented before the group. Additional updating information relating 

to materials science, engineering and technology was also presented. Mini plenary scssions involvcd 

structural ceramics, ASTM standard terminology for experiments and testing, and methods of assessing 

national laboratories, as well as materials and the environment. Special interest sessions with panel 

discussions focused on pre-college materials education and attracting minorities and females into technical 

fields. 

The experiments in this publication can serve as a valuable guide to faculty who are intereslcd in useful 

activities for their students. The material was the result of years of research aimed at better methods of 

teaching materials science, engineering and technology. The experiments were developed by facully, 

scientists, and engineers throughout the United States. There is a blend of experiments on new materials 

and traditional materials. Uses of computers in MS&E, experimental design, and a variety of low cost 

experiments were among the demonstrations presented. Transparency masters of technical pr~~sentalions 

are also included. 

An extensive peer review process of experiments was followed. After submission of abstracts, sclcctcd 

authors were notified of their acceptance and given the format for submission of experirncnts. 

Experiments were reviewed by a panel of specialists through the cooperation of the Materials Education 

Council. Authors received comments from the panel prior to NEW:Update 91, allowing them lo nlake 

neccssary adjustments prior to demonstrating their experiments. 

Comments from workshop participants provided additional feedback which authors used lo rnakc final 

revisions for this publication. 

Videotapes were made of the workshop by Westinghouse Environmental Management Company of Ohio. 

As with previous NEW:Updates, critiques were made of the workshop to provide continuing improvement 

of this activity. 

The Materials Education Council of the United States was represented again and will publish sclccted 

experiments in the Jollrnal of Materials Education. 

NEW:Update 91, and the '86, '87, '88, '89 and '90 workshops are, to our knowledge, the only national 

workshops or gatherings for materials educators that have a focus on the full range of issues on strategies 

for better tzaching about the full complement of materials. Recognizing the problem of motivaling young 

people to pursue careers in MSE, we have included exemplary pre-university activities such as Adventures 

in Science, ASM International Education Foundation's Career Outreach Program, Engineers for Education, 

and several programs run through high schools. 

111 

PRECEDING PAGE BSAiNK NOT FiLMED 
Through the workshops we have learned about ORNL Out Reach Programs, an NSF funded project to 

develop modules for pre-college materials education, and lhe Materials Science Technology Project at 

Richland High School (Richland, Washington) that has received support from Battelle PNL (Pacific 

Northwest Laboratory). An experiment was presented from the National Science Foundation and AT&T 

supported program at Science School in Newark, New Jersey. 

NEW:U@ate 91, with its diversity of faculty, industry, and government MSE participants, served as a 

forum for both formal and informal issues facing MSE education that ranged from the challenges of 

keeping faculty and students abreast of new technology to ideas to insure that materials scientists, 

engineers andl technicians maintain the proper respect for the environment in the pursuit of their objectives. 

NEW:Ulpdale 91 resulted from considerable cooperative efforts by individuals in government, education, 

and industry. The workshop's goal is to maintain the network of participants and to continue to collect 

these ideas and resources to bring them together in a comprehensive manual of standard experiments in 

materials science, engineering and technology. 

W hope that the experiments presented in this publication will assist you in teaching about materials 

science, engineering and technology. We would like to have your comments on their value and means 

of improving them. Please send comments to James A. Jacobs, School of Technology, Norfolk State 

University, FJorfolk, Virginia 23504. 

We express our appreciation to all those who helped to keep this series of workshops viable. 

The use of' trademarks or manufacturers' names in this publication does not constitute 

endorsement, either expressed or implied, by the National Aeronautics and Space 

Administra.tion. 

Workshop Co-Directors Liaisons 

James 0. Stiegler James E. Gardner, NASA-LARC 

Metals and Ceramics Division Margaret Gilson, ASM International 

Oak Ridge National Laboratory Robert Berrettini, Materials Education Council 

Irene Ways, Battelle-Pacific Northwest Laboratories 

James A. Jacobs 

Professor of Engineering Technology Director's Assistant 

Norfolk State University Diana P. LaClaire 

Norfolk State University 

ittee Members 

Seth Bates, San Jose State Univ. Carl Metzloff, Erie Community College 

William Callister, Materials Div., ASEE John W. Patterson, Iowa State Univ. 

Milton Ferguson, Norfolk State University Heidi Ries, Norfolk State University 

James Garclner, NASA-LARC David Rupert, Martin Marietta Energy Systems,Inc. 

Jonice Harris, NIST F. Xavier Spiegel, Loyola College 

William Winn, Department of Energy 
CONTENTS 

PAGE, 

... PREFACE.. .................................................................................................................................... 11 1 

..' PLANNING COMMITTEE MEMBERS AND REVIEWERS. ............................................... vi I i 

STRUCTURAL CERAMICS ................................................................................................... 1 

Douglas F. Craig -- Oak Ridge National Laboratory, 

Martin Marietta Energy Systems, Inc. 

TEMPERED GLASS AND THERMAL SHOCK OF CERAMIC MATERIALS .................. 45 

L. Roy Bunnell -- Battelle-Pacific Northwest Laboratories 

ELEMENTARY METALLOGRAPHY.. ................................................................................... 5 5 

Sayyed M. Kazem -- Purdue University 

CE IC PROCESSING: EXPERIMENTAL DESIGN AND OPTIMIZATION ................ 65 

Martin W. Weiser, David N. Lauben, and Philip Madrid -- 

University of New Mexico 

INIPAeT TESTING OF WELDED SAMYLES ....................................................................... 97 

Calvin D. Lundeen -- University of the Pacific 

COMPOSITE COLUMN OF COMMON MATERIALS ........................................................ 103 

Richard J. Greet -- University of Southern Colorado 

Cu-Zn BINARY PHASE DIAGRAM AND DIFFUSION COUPLES .................................... 109 

Robert A. McCoy -- Youngstown State University 

DESIGNING, ENGINEERING, AND TESTING WOOD STRUCTURES. ........................... 1 19 

Thomas M. Gorman -- University of Idaho 

COMPUTER VISION IN MICROSTRUCTURAL ANALYSIS ............................................. 129 

M. N. Srinivasan, W. Massarweh, and C. L. Hough -- Texas A&M University 

EXPERIMENTS WITH THE LOW MELTING INDIUM-BISMUTH ALLOY SYSTEM.. 141 

Richard P. Krepski -- Intermet Technology 

A SENIOR UFACTURING LABORATORY FOR DETERMINING INJECTION 

MOLDING PROCESS CAPABILITY ..................................................................................... 149 

Jerry L. Wickman and David Plocinski -- Ball State University 
L~OWLTORY EXPERIMENTS FROM THE TOY STORE ............................................... 159 

]HI. T. McClelland -- Arizona State University 

DIELEC1TRIC BEHAVIOR OF SEMICONDUCTORS AT 

MICRO'gAVE FREQUENCIES .............................................................................................. 169 

J. N. Dahiya -- Southeast Missouri State University 

Be-Cu PRECIPITATION DENING EXPERIMENT.. ...................................................... 187 

Richard L. Cowan -- Ohio Northern University 

ASTM - TERMINOLOGY FOR EXPERIMENTS AND TESTING ...................................... 195 

Richard R. Strehlow -- Oak Ridge National Laboratory, Martin Marietta 

Energy Systems, Inc. 

BRE-COILLEGE MATERIALS EDUCATION ......................................................................... 21 1 

Kenneth H. Eckelmeyer - Sandia National Laboratories 

L. Roy Bunnell - Battelle-Pacific Northwest Laboratories 

Linda L. Horton - ORNL, Martin Marietta Energy Systems, Inc. 

Richard P. Krepski -- Intermet Technology 

Robert Berrettini -- Materials Education Council 

A~lys Whitaker -- ASM International 

SOURCES OF SUPPORT FOR ENGINEERING EDUCATION ........................................... 217 

William Gamble -- American Society for Engineering Education 

DETERIJIINING SIGNIFICANT MATERIAL PROPERTIES, 

A DISCDVERY APPROACH ............................................................................................ 221 

Alan K. Karplus -- Western New England College 

MECULANISM OF SLIP & TWINNING ........................................................................... 233 

h4ansur Rastani -- North Carolina A&T State University 

THE MICROSCOPIC WORLD: A DEMONSTRATION OF ELECTRON 

MIICRClSCOPY FOR YOUNGER STUDENTS .................................................................... 245 

Linda L. Horton -- Oak Ridge National Laboratory, Martin Marietta 

Energy Systems, Inc. 

AN AUTOMATED SYSTEM FOR CREEP TESTING and FIVE EXPERIMENTS 

IN WiTERIALS SCIENCE FOR LESS THAN $10.00 ....................................................... 25 1 

E;. Xavier Spiegel and Bernard J. Weigman - Loyola College 
ATTRACTING AND RETAINING MINORITIES AND WOMEN 

IN TECHNICAL STUDIES.. .................................................................................................. 267 

Heidi R. Ries -- Norfolk State University 

Jonice Harris -- National Institute of Standards and Technology 

Jenifer A. T. Taylor -- NYS College of Ceramics at Alfred University 

Albert L. McHenry -- Arizona State University 

Larry Mattix -- Norfolk State University 

MATERIALS AND THE ENVIRONMENT.. .......................................................................... 275 

Linda S. Farmer -- Westinghouse Environmental Management Company ctf Ohio 

ISOTROPIC THIN-WALLED PRESSURE VESSEL EXPERIMENT .................................. 289 

Nancy L. Denton and Vernon S. Hillsman -- Purdue University 

STRESS-STRAIN CHARACTERISTICS OF RUBBER-LIKE MATERIALS: 

EXPERIMENT AND ANALYSIS.. ......................................................................................... 299 

David J. Allen -- Northeastern University 

DEMONSTRATION OF MAGNETIC DOMAIN BOUNDARY MOVEMENT USING AN 

EASILY ASSEMBLED VIDEOCAM-MICROSCOPE SYSTEM.. ................................ 3 07 

John W. Patterson -- Iowa State University 

AN EXPERIMENT ON THE USE OF DISPOSABLE PLASTICS AS A 

REINFORCEMENT IN CONCRETE BEAMS.. ................................................................... 3 13 

Mostafiz R. Chowdhury -- East Carolina University 

STRUCTURE, PROCESSING AND PROPERTIES OF POTATOES .................................... 329 

Isabel K. Lloyd, Kimberly R. Kolos, Edmond C. Menegaux, Huy Luo, 

Richard H. McCuen, and Thomas M. Regan -- University of Maryland 

COMPUTER INTEGRATED LAB TESTING.. ....................................................................... 3 6 2 

Charles C. Dahl -- Ventura College 

MECHANICAL PROPERTIES OF BRITTLE MATERIAL. .................................................. 3 67 

L. R. Cornwell -- Texas A&M University 

INTRODUCTORY EAT-TRANSFER and HEAT-TREATING OF MATERIALS.. .......... 375 

Edward L. Widener -- Purdue University 

MEASURING THE SURFACE TENSION OF SOAP BUBBLES and 

R/IEASURING THE WEIBULL MODULUS OF MICROSCOPE SLIDES .......................... 389 

Carl D. Sorensen -- Brigham Young University 

vii 
REVIEWERS FOR NEW:Update 91 

Else Breval 

Senior Res,earch Associate 

Materials Research Laboratory 

The Pennsylvania State University 

Witold Brostow 

Professor of Materials Science 

University of North Texas 

Wenwu Cao 

Research Associate 

Materials Research Laboratory 

The Pennsylvania State University 

E. K. Graham 

Professor of Geophysics 

Materials Research Laboratory 

The Pennsylvania State University 

Girish Harshe 

Postdoctoral Fellow 

Materials Research Laboratory 

The Pennsylvania State University 

Bruce E. Ehox 

Associate Professor of Materials Science 

Materials :Research Laboratory 

The Pennsylvania State University 

R. I. A. Malek 

Research Associate 

Materials Research Laboratory 

The Pennsylvania State University 

Gary Messing 

Professor of Materials Science 

The Pennsylvania State University 

Rustum Roy 

Evan Pugh Professor of the Solid State 

Materials Research Laboratory 

The Pennsylvania State University 

Clayton 0. Ruud 

Professor of Industrial Engineering 

The Pennsylvania State University 

Earle Ryba 

Associate Professor of Metallurgy 

The Pennsylvania State University 

Skikanth Varanasi 

Research Associate 

Materials Research Laboratory 

The Pennsylvania State University 

Technical notebooks were prepared by 

NASA MNGLEY RESEARCH CENTER 

Video taping is being provided by 

WESTINGHOUSE ENVIRONMENTAL GEMENT COMPANY OF OHIO 

Announcements of the workshop were printed by 

ASM INTERNATIONAL 

. . . Vlll 
-____-_____________------------------------------------------------ -__-__-____________------------------------------------------------ 

NATIONAL EDUCATORS' WORKSH0P:Update 91 

Oak Ridge National Laboratory 

Martin Marietta Energy Systems, Inc. 

Oak Ridge, Tennessee 

November 12 - 14, 1991 

Final Participants List __-_C-__-__--_-____---------------------------_---_------------------ ____--_____--_--___-------------------------------------------------- 

Edward Aebischer Robert Berrettini 

Martin Marietta Energy System, Inc. Pennsylvania State University 

Oak Ridge National Laboratory 110 Materials Research Laboratory 

P. 0. Box 2008 University Park, PA 16802 

Oak Ridge, TN 37831 814-865-1643 

615-574-0762 

Douglas Bowling 

Nicholas 0. Akinkuoye University of Cincinnati 

Iowa State University 498 Rhodes Hall 

217 I. Edt Building No. 2 Cincinnati, OH 45221 

Arnes, IA 50011 5 13-556-7759 

5 15-294-9805 

L. Roy Bunnell 

David J. Allen Battelle-Pacific Northwest Laboratories 

Northeastern University Battelle Blvd., P. 0. Box 999 

120 Snell Engineering Center Richland, WA 99352 

Boston, MA 02115 509-376-2799 

617-437-2500 

Susan Cable 

Stanton Apple New Hampshire Technical College 

Corley Room 247 194 Wight Street 

Arkansas Tech. University Berlin, NH 03570 

Russellville, AK 72801 603-752-1 113 

501-968-0629 

Mostafiz R. Chowdhury 

Seth P. Bates East Carolina University 

San Jose State University 325 Rawl 

One Washington Square Greenville, NC 27858-4353 

San Jose, CA 95192-0061 919-757-6707 

408-924-3227 

Lorenzo Copeland 

Chris Berndt Westinghouse Environmental Management 

Materials Science & Engineering Company 

State University of New York P.O. Box 398704 

Stony Brook, NY 11794-2275 Cincinnati, OH 45239 

516-632-8507 
Richard L. Cowan 

Ohio Northern University 

Ada, OH 45810 

419-634-7520 

Douglas F. Craig 

Oak Ridge National Laboratory 

Mart.in Marietta Energy Systems, Inc. 

P. 0. Box 2008 

Oak Ridge, TN 37831 

615-574-9181 

Jeffrey Csernica 

Bucknell University 

Department of Chemical Engineering 

Lewisburg, PA 17837 

717-524-1257 

Jai N. Dahiya 

Physics Department 

Southeast Missouri State University 

One University Plaza 

Cape Girardeau, MO 63701 

314-651-2390 

Charles C. Dahl 

Ventura College 

4667 Telegraph Road 

Ventura, CA 93003 

805-654-6400 

Kenneth 13. Eckelmeyer 

Sandia National Laboratories 

Albuquerque, NM 8718.5-5800 

505-845-8680 

Lincla Farmer 

Wes tinghouse Environmental 

Management Company of Ohio 

P. 0. Box 398704 

Cincinnati, OH 45239-8704 

5 13-738-6747 

Carlos M. Ferregut 

The University of Texas at El Paso 

Department of Civil Engineering 

El Paso, TX 79968 

915-747-5464 

William Gamble 

American Society for Engineering 

Education 

Suite 200 

Eleven Dupont Circle 

Washington, DC 20036 

202-293-7080 

James E. Gardner 

National Aeronautics and Space 

Administration 

LARC 

11 Ames Road MS 118 

Hampton, VA 23665 

804-864-6005 

Thomas Gorman 

University of Idaho 

Department of Forest Products 

Moscow, ID 83843 

208-885-7402 

Richard Greet 

University of Southern Colorado 

2200 Bonforte Boulevard 

Pueblo, CO 81001 

719-549-2884 

Jonice Harris 

Materials Bldg. 223, Room B226 

National Institute of Standards & 

Technology 

Gaithersburg, MD 20899 

301-975-6007 

Antonio Harrison 

Norfolk State University 

2401 Corprew Avenue 

Norfolk, VA 23504 

804-683-8109 
John C. Hibberd 

Millersville University 

Millersville, PA 17551 

717-872-3326 

Vernon S. Hillsman 

School of Technology 

Purdue University 

145 Knoy Hall 

West Lafayette, IN 47907 

317-494-75 17 

Linda L. Horton 

Oak Ridge National Laboratory 

Martin Marietta Energy Systems, Inc. 

P. 0. Box 2008 

Oak Ridge, TN 37831 

615-574-5081 

Emil H. Isaacson 

University District of Columbia 

39 Great Pines Court 

Rockville, MD 20850 

202-282-7426 

James A. Jacobs 

Norfolk State University 

2401 Corprew Avenue 

Norfolk, VA 23504 

804-683-8109 

Jeffrey E. Jones 

Cuesta College 

230 Wagon Wheel Way 

Arroyo Grande, CA 93420 

805-546-3274 

Alan K. Karplus 

Western New England College 

1215 Wilbraham Road 

Springfield, MA 011 19 

4 13 -782- 1220 

Sayyed M. Kazem 

Purdue University 

Knoy Hall 

West Lafayette, IN 47907 

3 17-494-7528 

Thomas F. Kilduff 

Thomas Nelson Community College 

504 Brafferton Circle 

Hampton, VA 23663 

804-85 1-0272 

Richard P. Krepski 

Intermet Technology 

116 Long Road 

Georgetown, PA 15043 

412-573-7754 

David N. Lauben 

University of New Mexico 

Mech. Engr. Dept. 

Albuquerque, NM 8713 1 

505-277-283 1 

Leonard Leath 

Laney College 

900 Fallon Street 

Oakland, CA 94607 

510-464-3453 

Joy S. Lee 

Oak Ridge National Laboratory 

Martin Marietta Energy Systems, Inc. 

P. 0. Box 2008 

Oak Ridge, TN 37831-6263 

615-574-9918 

Ping Liu 

School of Technology 

Eastern Illinois University 

Charleston, IL 61920 

217-581-6267 
Isabel Lloyd 

University of Maryland 

College Park, NID 20742-2115 

301-405-5221 

Calvin Lundeen 

University of the Pacific 

1502 'Valencia Avenue 

Stockton, CA 95211 

209-946-215 1 

Alan Lynam 

Delaware Technology & Community 

College 

124 Osage Lane 

Newark, DE 19711 

302-453-3772 

Phillip Madrid 

University of New Mexico 

Albuquerque, NM 87131 

505-277-283 1 

Kenneth L. Matthews, Jr. 

San Joaquin Delta College 

5 15 1 Pacific Avenue 

Stockron, CA 95207 

209-474-5298 

Larry Mattix 

Norfolk State University 

2401 Corprew Avenue 

Norfolk, VA 23504 

304-683-25 11 

Jack IIVlauer 

Mechanical/Manufacturing Engineering 

Technology 

Pe1lis:sippi State Technical Community 

College 

10915 Hardin Valley Road 

P.O. Box 22990 

Knoxville, TN 37933-0990 

H. T. McClelland 

Arizona State University 

Tempe, AZ 85287-6706 

602-965-6584 

Robert A. McCoy 

Youngstown State University 

Youngstown, OH 44555 

216-742-1736 

Albert L. McHenry 

Arizona State University 

Tempe, AZ 85207-6706 

David Morrison 

Clarkson University 

Potsdam, NY 13699 

3 15-268-6585 

Herbert Newman 

Mohawk Valley Community College 

1101 Sherman Drive 

Utica, NY 13501 

Patrick Pandolfi 

Pasadena City College 

Pasadena, CA 91109 

818-585-7123 

John W. Patterson 

Iowa State University 

110 Engineering Annex 

Arnes, IA 50011 

5 15-294-7562 

Mansur Rastani 

North Carolina A&T State University 

111 Price Hall 

Greensboro, NC 2741 1 

919-334-7585 

xii 
Bonnie S. Reesor 

Oak Ridge National Laboratory 

Martin Marietta Energy Systems, Inc. 

P. 0. Box 2008 

Oak Ridge, TN 37831-6263 

615-574-5984 

Heidi R. Ries 

Norfolk State University 

2401 Corprew Avenue 

Norfolk, VA 23504 

804-683-8020 

Thomas Roberts 

Milwaukee Area Technical College 

700 W. State Street 

Milwaukee, WI 53233 

414-278-6891 

William Ross 

Muskegon Community College 

221 S. Quarterline 

Muskegon, MI 49442 

616-777-0367 

Robert Scott 

Mechanical/Manufacturing Engineering 

Technology 

Bellissippi State Technical Community 

College 

10915 Hardin Valley Road 

P.O. Box 22990 

Knoxville, TN 37933-0990 

Howard L. Schmidt 

Rock Valley College 

3301 N. Mulford 

Rockford, IL 61111 

815-654-5510 

Carl Sorensen 

Brigham Young University 

435 CTB 

Mfg. Engr. & Engr. Technology Dept. 

Provo, UT 84602 

801-378-6397 

Xavier Spiegel 

Loyola College 

4501 N. Charles Street 

Baltimore, MD 21210 

410-617-2515 

Malur N. Srinivasan 

Texas A&M University 

College Station, TX 77843-3123 

409-845-1417 

James 0. Stiegler 

Oak Ridge National Laboratory 

Martin Marietta Energy Systems, Hnc. 

P. 0. Box 2008 

Oak Ridge, TN 37831-6132 

615-574-4065 

Richard R. Strehlow 

Martin Marietta Energy Systems 

Oak Ridge National Laboratory 

P. 0. Box 2008 

Oak Ridge, TN 37831-6088 

615-574-4956 

Jenifer A. T. Taylor 

New Uork State College of Ceramics at 

Alfred University 

Alfred, NY 14802 

607-871-2190 

Monroe Thompson 

Westinghouse Environmental Management 

Company of Ohio 

P. 0. Box 398704 

Cincinnati, OH 45239-8704 

5 13-738-605 1 

Dev Venugopalan 

University of Wisconsin-Milwau kee 

3200 N. Cramer Street, P.O.Box 784 

Milwaukee, WI 53201 

414-229-5691 

. . . Xlll 
Jeff Wag~ner 

Westinghouse Environmental Management 

Compan:y of Ohio 

P. 0. Box 398704 

Cincinnati, OH 45239-8704 

5 13-738-6084 

William I. Winn 

U. S. Department of Energy Site Office 

P. 0. Box 398705 

Cincinnati, OH 45239 

513-738-6155 

Tom Wagner 

Westinghouse Environmental Management 

Compan:y of Ohio 

P. 0. Box 398704 

Cincinnati, OW 45239-8704 

5 13-738-6084 

Margaret Weeks 

Corning (2ommunity College 

M/P/T Division 

Corning, NY 14830 

607-962-9243 

Martin W. Weiser 

Universit:~ of New Mexico 

Albuquerque, NM 87131 

505-277-283 1 

Arlys Whitaker 

ASM International 

State Route 81 

Materials Park, OW 44073 

800-336-5 152 

Jerry L. TNickman 

Ball State University 

College of Applied Sciences and 

Technology 

Muncie, IN 47306-0255 

317-235-5641 

Charles W. Wright 

Mechanical/Manufacturing Engineering 

Technology 

Pellissippi State Technical Community 

College 

10915 Hardin Valley Road 

P.O. Box 22990 

Knoxville, TN 37933-0990 

David Yang 

University of Tennessee at Martin 

108 Ramer Street 

Martin, TN 38237 

901-587-7389 

her Zaza 

Alabama A&M University 

Department of Industrial Technology 

Normal, AL 35816 

205-85 1-5589 

Edward L. Widener 

Purdue University 

boy Hail- Room 119 

West Lafayette, IN 47907 

3 17-494-'7521 

xiv 
Douglas F. Craig 

Oak Ridge National Laboratory 

Martin Marietta Energy Systems, Inc. 

P. O. Box 2008 

Oak Ridge, Tennessee 37831 

Telephone 615-574-9181 

N92-30264 

NATIONAL EDUCATORS' WORKSHOP 

NEW: Update 91 

Douglas F. Craig 

Oak Ridge National Laboratory 

November 12-1 4,1991 

3 

PRECEDING PAGE BLANK NOT FlbMEe) 
PERSPECTIVES ON WHERE MATERIALS 

ARE GOING 

MATERIALS SCIENCE AND ENGINEERING FOR THE 1990~~ 

MAINTAINING COMPETITIVENESS IN THE AGE OF MATERIALS. 

National Research Council, National Academy Press, Washington 

D.C. -8989 

M. F. Ashby, "TECHNOLOGY OF THE 1990s: ADVANCED MATERIALS 

AND PREDICTIVE DESIGN", Phil. Trans. R. Soc. Lond. A 322, 

393-407 (1 987) 

E. L. Langer, "EVOLUTION OF ADVANCED MATERIALS IN A CHANGING 

WORLD", International Conference on Evolution of Advanced Materials, 

AIMIASM, Milano Italy, May 31-June 2,1989 
IMPACT OF MATERIALS 

IN -1982, DAMAGES DUE TO MATERIAL FAILURE W EWE GREATER 

THAN $200 BILLION ANNUALLY - THIS APPROACHES THE ANNUAL 

FEDERAL DEFICIT. (M. Cohen in Advanced Materials Research, 

NASINAE, 1987) 

COMPETITIVENESS AND QUALITY OF LIFE IN THIS DECADE AND 

21st CENTURY WILL DEPEND UPON ADVANCES IN MATERIALS. 

(paraphrase of R. Chianelli, MRS Bulletin, August, 1990) 

LEADERS IN MATERIALS TECHNOLOGY WILL DOMlNATE THlE 

MARKETPLACE IN THE 21st CENTURY. (Panel discussion at int'l 

Symp. Basic Technologies for Future Industries, Kobe, Japan, March 

1989) 

COMMODITY METALS AND PLASTICS HAVE PASSED 

DEMAND PEAK AND USAGE IS DECLINING 

COMMODITY PLASTICS 

STAINLESS STE 

SUPERALLOYS 

SPECIALTY METALS 

ENG. PLASTICS 

ADVANCED PMCs 

STRUCTURAL 

CERAMICS 

HEAVY RAPID GROWTH 

R&D 

GROWTH 

GROWTH malturing=GDP < GDP 
THERE IS A CHANGE IN BASIC MATERIAL USE 

SUBSTITUTION OF ONE MATERIAL FOR ANOTHER HAS SLOWED 

WE. GROWTH OF DEMAND FOR PARTICULAR MATERIALS 

DESIGN CHANGES WAVE INCREASED THE EFFICIENCY OF 

MAlrERlALS USE 

SATURATION OF MARKETS WHICH WERE PREVIOUSLY EXPANDING 

HAS OCCURRED 

LOW MATERIALS CONTENT IN PRODUCTS FOR NEW MARKETS, 

PARlTLY BECAUSE OF THE COST OF HIGHER PERFORMANCE 

MATERIALS 
MARKET DEMAND IS NOW LIGHTER, STRONGER, MORE 

DURABLE MATERIALS 

Desired Characteristic Aero. Auto Bio Chem. Elec. Energy Metal Teie. 

Light 1 strong 

High temp resist. 

Corrosion resist. 

Efficient processing 

Near-net-shape 

Prediction of life 

Prediction of propertie 

Materials data bases 

(Materials Science and Engineering for the 1990s) 
MODERN MATERIALS 50X HIGHER 

GTH-TO-DENSITY RATIO THAN CAST IRON 

Aramid & 

Wood, Bronze Cast 

1800 1900 2000 

YEAR 
MODERN MATERIALS ENABLE HIGHER 

ENGINE OPERATING TEMPERATURES 

Air-cooled 

1900 1940 1980 

YEAR 
ERlALS ENABLED EXPONENTIAL INCREASE 

N CUTTING TOOL SPEED 

1900 

YEAR 
THE PORTFOLIO OF ADVANCED MATERIALS 
STRUCTURAL CERAMICS ARE LEADING 

CANDIDATES FOR MANY APPLICATIONS 

Based primarily 

CERAMICS on natural raw 

materials of clay 

Inorganic, nonmetallic and silicates 

 material:^ processed 

ADVANCED* 

Include artificial 

raw materials, 

exhibit specialized 

properties, require 

more sophisticated 

processing 
THE APPEAL OF STRUCTURAL CERAMICS IS EASY TO 

UNDERSTAND 

High temp resist. 

Corrosion resist. 

Efficient processing 

Prediction of life 

Prediction of properties 

Light with compressive strength > or = metals 

Withstand extreme temperatures 

Chemicaily inert, hard, abrasion resistzsnt 

BUT REALiZING THESE PROPERTIES 

REQUIRES A LEVEL OF MICROSTRUCTURAL 

AND CHEMICAL PERFECTION FAR BEYOND 

THAT OF TRADITIONAL CERAMICS 
STRUCTURAL CERAMICS ARE A 

RESULT OF A FEW KEY DEVELOPMENTS 

TRADITIONAL + DEVELOPMENT = ADVANCED 

MATERlFaLS 

ANALYSIS 

PROCESSING 

PREPARATION 

MICROSCOPY 

PROCESSING 

I & PROPERTIES 
SOPHISTICATED MICROSCOPY ALLOWS DETERMINATION OF MlCROSTRUCTUREE 

ORIGiNRL ;i;-";",f?aI 

BUCK AND WHITE PHOTOG2AFld 
MECHANICAL PROPERTIES CAN BE DETERMINED AT THE MICROSTRUCTURAL 

LEVEL 

18 ORIGINAL PAGE 

BLACK AND WHITE PHOTOGRAPCI 
TENSILE TESTER-SPECIALIZED EQUIPMENT FOR DETERMINING CERAMIC 

MECHANICAL PROPERTIES 

19 QR~GA~XP bjy-l -fm 1 4r9sL :-,4u,-- 

BLACK AND WH!T% PHOTOGgBIPH 
TENSILE TESTER-FULL VIEW 

;;RlGlNAL P,4GE 

BLACK AND WHlTE PHOTOGRAPH 
ADVANCES IN CERAMICS BE BASED ON ATOMISTIC 

MODELING, TAILORED MICROSTRUCTURE AND 

SOPHISTICATED PROCESSING 

MICROSTRUCTURE TAILORING & NOVEL 

COMPOSITE DESIGN ADDRESS INHERENT BRITTLENESS 

OF CERAMICS 

COMPARED TO METALS WITH TYPICAL FRACTURE TOUGHNESS OF 15-200 
0 .- 

IS: 
Q 

E: aE 

m 

=I 

Q 

a!. 

0) 

2& 

cn 

E 

3 
ORIGINAL PAGE 

BLACK AND WHITE PH018GRAPH 
ORNL-PHOTO 71 04-88R 

FIBER-REINFORCED CERAMIC COMPOSIITES 

HAVE BEEN FABRICATED USING A FORCED 

CHEMICAL VAPOR INFILTRATION PROCIESS 

GRAPHITE 

HOLDER- 

-FIBROUS 

PREFORM 

INFILTRATED 

COMPOSITE J '-WATER COOLED 

SURFACE 

REACTANT 

GASES 

<\F;;,y:\:qy- I.,#. *...- P.461F 

BLACK ARG %/ii'TE PHOTCGRAPW 
EXPERIMENTAL RESULTS SHOW MODIFICATION OF MATRIX/ WHISKER 

INTERFACE IMPROVES COMPOSITE TOUGHNESS 

t 

STRESS 

STRAIN- 
TOUGH, CONTINUOUS-FIBER CERAMIC COMPOSITE 

ORIGIN/\L PAGE 

BUCK AND WHlTE PHOTOGRAPH 

OWIGIPJAL PAGE 

BLACK AND WWBTE PI-101iOGRAPH 
I". Q"-3 * " 6.B" .>Q", 4L iPF+CE 

BUCK AND VVhlTE PHOTOGRAPH 
QRjCIR&L PA2E 

BLACK AND WHITE PHOTOGRAPH 
MICROWAVE SlNTERlNG HAS SIGNIFICANT IMPLICATIONS 

FOR NEW MATERIALS APPLlGATlONS 

TEMPERATURE (06) 

0 

- Zr%-8& 9b\82G3 

Accelerated Kinetics: 

- Sintering occurs at lower 

temperatures 

Significant Potential Benefits 

- Lower temperature processing 

- Finer microstructures 

- BeRer mechanical properties 

Advanced Materials Applications: 

- Composites from incompatible 

materials 

- Self-lubricating high-temperature 

bearings 

- Electrical materials 

- Engine componerlls 

1100 IXX) 1300 (400 

TEMPERATURE 
MICROWAVE FACILIN FOR DENS1 WING CERAMICS 

MICROSTRUCTURE MODIFICATION SIGNIFICANTLY 

IMPROVES CREEP RESISTANCE 

TIME (h) 


el--* 7 : ' * g -7 - p(#&ji .,, \;,- F, ,bK 

SLACK AND WHITE PHQTOGRAPh 
EmENDED VEHlCLE TESTING OF VALVE TRAIN COMPOI\BEINTS 

SUMMARY 

SPECIALIZED, TECHNOLOGY-INTENSIVE, HIGH-VALUE-ADDED 

ADVANCED CERAMICS ARE MOVING TOWARD COMMERCIALOZA610NATION 

TO FILL THE DEMAND FOR LIGHTER, STRONGER, MORE 

CORROSION RESISTANT MATERlALS 

ADVANCEMENTS WILL RELY MORE AND MORE ON PROCESSING 

AND MODELING FROM THE ATOMIC SCALE UP WHlCH IS MADE 

POSSlBLE BY ADVANCED ANALYTIC, COMPUTER, AND PROCESSING 

TECHNIQUES 

SPECIALIZED PROPERTIES AND HIGHER COST WILL PROVIDE E38TH 

NEW OPPORTUNITIES AND CHALLENGES TO DESIGNERS AND 

END-USERS 

* MORE RIGOROUS DEFINITION OF COMPONENT REQUIRIEMENTS 

* COMPONENT REDESIGN TO ACCOMMODATE BRITTLE BEHAVIOR 

* SYSTEM REDESIGN TO MAKE FULL USE OF NEW MATERIALS 

CLOSER COUPLING BETWEEN DESIGNERS AND MATERIALS 

DEVELOPERS 

TEMPERED GLASS 

AND 

THE L SHOCK OF CE MIC MATERIALS 

L. Roy Bunnell 

Battelle-Pacific Northwest Laboratories 

Battelle Boulevard 

P. 0. Box 999 

Richland, Washington 99352 

Telephone 509-376-2799 

TEMPERED GLASS 

L. Roy Bunnell 

Pacific Northwest Laboratory*, Richland, WA 

WEU WODS: glass, tempering, annealing 

PREREQUISITE KNOWLEDGE: This material could be taught as a demonstration to a 

typical student of materials science, at the high school level or above. More depth can be 

provided by having students actually temper and anneal the glass, but this requires more 

equipment and time. This writeup contains a simplified method for making tempered glass which 

uses minimal equipment. 

: (Demonstration version) Automobile side whdows, 

obtained from an auto wrecking yard; spring-loaded center punch; polyethylene bag large enough 

to hold a window; two polarizing filters; overhead projector. For the laboratory version, use all of 

the above plus the following: @rexa* brand borosilicate glass rod, about 6 mm diameter; torch 

burning oxygen-acetylene or oxygen-natural gas or propane; water-filled bucket of 20-1 capacity; 

side-cutter pliers. 

PROCEDURE: First, introduce the concept that glass is a very strong material, state that 

tensile strengths greater than 6.9 GPa have been measured on fresh surfaces free from all 

damage. Surface damage, including that resulting from the corrosive action of water, creates tiny 

defects that reduce the useful strength to a tiny fraction (0.2%) of this value. By using a spedal 

property of glass--the dependence of its density on its cooling rate--glass can be toughened to 

make it more durable and its fracture may be controlled so that dangerous shards are not 

produced. This process is called tempering. 

Glass, like all other ceramic materials, is brittle, meaning that it will fracture at a very low 

strain, usually 0.01 to 0.1 percent. Like all other ceramics, failure usually starts at the surface, 

and this surface is very easy to damage by contact with other hard materials or even by 

atmospheric attack. Since the surface is easy to damage and failure begins at the surface, a 

process is required which makes the surface less sensitive to incidental damage. This is done by 

placing that surface in compression. A thermal process for accomplishing this is the sulbject of 

this experiment. 

As shown in Figure 1, the density of a typical glass is dependent on its cooling rate. At 

high cooling rates, the glass structure becomes rigid at a density corresponding to that usually 

seen at high temperature. At lower cooling rates, there is more time for the glass structure to 

adjust so that the final density is higher. If a piece of glass is heated to a temperature above 

* Pacific Northwest Laboratory is operated by Battelle Memorial Institute for the U. S. 

Department of Energy under Contract DE-AC06-76RLO 1830. 

* * Made by Corning Glass Works. 
point A on the curve shown and suddenly quenched, the surfaces will cool first and become rigid 

at the low density corresponding to that temperature. The inner glass will cool more slowly and 

.will reach a geater density, which means that it will pull inward on the outer glass, placing it in 

compression. The inner glass is placed in tension to balance the compression, but it is shielded 

from hcidental damage by the outer glass. Since the surface glass is in compression, it will 

withstand quite a lot of bending strain before it is placed in tension, as is required to breakit. The 

bcidental hlpacts in everyday use are resisted far better by such glass, which is called tempered 

glass. The nnechanism for tempering glass is much different than that used for tempering steel, 

and it may be productive to discuss the difference to avoid confusion. 

In the manufacture of tempered glass for the side and rear windows of automobiles and 

for sEdhg glass doors, the glass is heated above point A, then cooled rapidly by an array of air 

jets blowing on both of its faces. Demonstrate this using a piece of car side window glass 

obtahed from a wrecking yard for about $10. With a strong light behind the piece of tempered 

@ass, place a polarizing filter on both sides of the glass. By rotating one of the filters, the pattern 

left by the air jets can be seen. Some students may recall seeing similar patterns through 

polarkkg sun glasses in light reflected from back windows of cars. Polarized light is rotated 

dzferentjy passing through stressed glass than it is through unstressed glass. Demonstrate the 

toughness of the glass by supporting it between two short pieces of wood, then standing on it. It 

will support your weight easily, though you may want to resist the temptation to jump on it to 

make a point. Note: Just in case the glass should break. place it inside the plastic ba~ so that 

Ask the students why, if tempered glass is so strong, it is not used in windshields. The 

answer is th,at when it breaks, it fractures into very small, roughly equiaxed pieces. A rock flipped 

up by the ear ahead could leave you trying to drive using an opaque windshield! This fracture 

characteristic is an hportant safety feature, in that tempered glass is relatively safe when broken. 

It does not fracture into long, knifelike shards such as seen in ordinary glass. 

Someone may ask how tempered glass may be broken, say in an escape situation if 

needed. Enlergency personnel--policemen, ambulance drivers, etc.--routinely carry spring-loaded 

center punches for just such emergencies. This kind of punch generates large shock forces, 

enough to make indentations in steel, with enough force to overcome the compressive stress in our 

tempered glass window. Once the outer glass is damaged by a large enough force, the force 

equsbrium is disrupted and the entire piece of glass destroys itself. Demonstrate this by first 

placing the car window in a plastic bag, then using the center punch to damage the glass through 

a small hole in the bag. The window will fail with a loud noise, and the pieces can be seen to be 

small and not very dangerous. 

In a dass permitting more depth in this subject, students may temper glass for themselves. 

By heating a Pjrex rod in a suitably hot gas flame, droplets can be formed and allowed to fall into 

a bucket of water to quench them. Such a quenching method is poorly controlled, so the size of 

the droplets is critical; small droplets will experience less tempering than desired and large 

droplets may fracture when quenched. Use caution during - this operation, both with molten dass 

and with Less obviouslv hot dass that has been set aside. Tempering can be demonstrated by first 

gasping the, droplet in the palm of the hand, then cutting the protruding "tail" off, using a pair of 
side-cutting pliers. Use safetv dasses or close eves during this o~eration. The droplet will 

detonate, and will be easily felt by the student. Upon opening the hand, the glass will be hund as 

tiny grains. 

These droplets may be annealed by heating them in a furnace to 500 C, then lettbg them 

furnace cool. If the tail is now cut off the droplet, there will be no dramatic fracture as before; 

the stresses have been relieved by the annealing process. 

SAMPLE DATA SHEETS: Not Applicable. 

INSTRUGTOR NOmS:-Students should be closely supervised during the temperhg and 

resting of the glass droplets. 

REFERENCE: Ggery, W. D., H. K. Bowen, D. R. Uhhann, Introduction to Ceramics, 

2nd Edition, John Wiley & Sons, 1976, Ch. 16. 

SOURCES OF SUPPLIES: Pyrex rod and polarized plastic sheets can be obtakied from 

any scientific supply house, and a suitable torch from any supplier of welding supplies. 

Alternately, school shop facilities could be borrowed. 
. Relationship between temperature and volume for a typical glass. Rapid cooling results 

in a higher volume (lower density) than obtained with slower cooling, because more time is 

avadilable for structural rearrangement in the glass. 
THERMAL SHOCK OF CERAMIC MATERIALS 

L. Roy Bunnell 

Pacific Northwest ~aborator~*, Ri chl and, WA 

KEY WORDS: thermal shock, Young's modul us, thermal expansion coefficient 

PREREQUISITE KNOWLEDGE: This demonstration is suitable for students in 

materials science at the high school or college levels. The studeabts should 

understand elementary mechanics concepts, such as Young's Modul us of El asti ci ty . 

OBJECTIVES: To demonstrate the concept of thermal shock in ceramic 

materi a1 s, and to illustrate the pertinent factors of materi a1 s selection. 

EQUIPMENT AND SUPPLIES: Furnace capable of control led temperatures up to 

500°C; aluminum oxide rod or 2-hole thermocouple insulator, approx. 3 mrrn diameter 

x 10 cm long; water; tongs; black or blue ink. 

PROCEDURE: Thermal shock is a mechanism often leading to the failure of 

ceramic materials. Many uses for ceramics involve high temperatures, and if the 

temperature of a ceramic is rapidly changed failure may occur. Thermal shock 

failures may occur during rapid cooling or during rapid heating. As an example, 

consider rapid cooling, which is easier to visualize. If a ceramic material is 

cooled suddenly, the surface material will approach the temperature of the cooler 

environment. In doing so, it will experience thermal contraction. Since the 

underlying material is still hot, the skin material is stretched and so 

experiences tensile stress. If the resulting strain is high enough (0.01% to 

0.1% for most ceramics), the ceramic will fail from the surface and cracks will 

propagate inward. Even if these cracks do not cause immediate failure, "che 

ceramic will be severely weakened and may fail from mechanical over1 oad of forces 

it would normally withstand. 

After distributing aluminum oxide rods to the students urge them to 

manipulate and bend the rods with their hands. Soon, popping sounds will be 

heard in the classroom. These sounds demonsrate how a brittle material fails 

without warning, with no permanent strain, and at a low-strain value. Next, 

place about ten of the rods into a stainless steel beaker or a small metal pan 

and heat to 500°C in a suitable furnace. Remove the container from the furnace 

and quickly quench the rods in a bucket of water, then dry them overnight at 

about 100°C. The following day, dip the rods in ink, which acts as a crude dye 

penetrant to make any cracking visible. Wipe excess ink from the rods, handl ing 

carefully to avoid breaking. Again, urge the students to bend the rods and note 

that the rods are much weaker than before. Also, note from the partial 

penetration of the ink that the cracks do not extend into the centers of the 

rods. This is because the cracks start at the surface in a tensile stress area, 

but propagate into regions of lower stress until they stop. When a quench is 

performed at lower temperatures (down to about 300°C) crack density is lower and 

crack length is shorter. A quench temperature that is lower still will not 

* Pacific Northwest Laboratory is operated by Battelle Memorial Institute for the U. S. Depaflment of 

Energy under Contract DE-AC06-76RLO 1830. 
result in any detectable damage. This temperature is not a constant, but is a 

function of both configuration and material. 

When comparing different ceramics for thermal shock appl icati ons, it is 

common to use a figure of merit or index of thermal shock performance. This is 

a number (ratio) that is useful for both choosing materials and for visualizing 

the thermal shock process. Since the index should be high for a thermal shock 

resistant ceramic, its numerator should contain properties that are numerically 

large when good thermal shock performance is exhibited by a material. Tensile 

strength (S) and thermal conductivity (K) are therefore placed in the numerator, 

the former for obvious reasons and the latter because a high value of thermal 

conductivity tends to decrease thermal gradients, other factors being equal. The 

denominator of the thermal shock index is composed of the thermal expansion 

coefficient (A) and the Young's modulus of elasticity (E) . The thermal expansion 

-is resporlsible for the failure-causing strain, so it should be as small as 

possible. The el astic modulus is a measure of the stress resulting from a given 

strain, :so it should be a low value for good thermal shock performance. 

Combining these factors, 

Thermal Shock Index (TSI) = SK 

A E 

where the units of measurement should be consistent within a given comparison. 

In the case of common glasses, all of the properties except thermal expansion 

fall into a relatively narrow. range. By choosing a glass with low thermal 

expansion, thermal shock failure can be avoided in most cases. See, for example, 

the index values for soda-l ime glass, borosil icate glass, and fused silica in 

Tabl e I. Note the 1 arge difference between the thermal shock indices of a1 uminum 

oxide and graphite. This difference is backed by experience; it is extremely 

difficult to cause graphite to fail by thermal shock, principally because its 

Young" modulus is so low and its thermal conductivity is high. 

SAMFIE DATA SHEETS: If students quench specimens from a series of 

temperatures, data sheets might be constructed to record crack frequency as a 

function of quench temperature. Alternately, ceramic rods might be broken in 3- 

point bending on a testing machine, and the bending strength plotted as a 

function of quench temperature. 

INS-TRUCTOR NOTES: Provided above in Procedure. Follow usual safety 

precautions to avoid burns. 

REFERENCES: Kingery, W. D., H. K. Bowen, D. R. Uhlmann, Introduction to 

Ceramics, Second Edition, John Wiley & Sons, New York, 1979, Ch. 16. 

SOURCES OF SUPPLIES: The alumina should be >95% dense, but can be of any 

purity greater than 95%. One supplier is Coors Ceramics, Golden, CO. 
Table I. Thermal Shock Index for Some Common Ceramic Materials 

K, (I) A, 0~6-1, 

Materi a1 W/cm- OC S, MPa x 10- E, GPa TS 1 

Soda-lime-silica 2E-2 68(') 9.2 69 2.1 

glass 

Borosilicate glass 2E-2 6 8 3.3 6 3 6.5 

Fused SiO, 6E-2 6 8 0.6 72 94 

Aluminum Oxide 3E- 1 204 5.4 344 3 3 

Thermal conductivity and expansion coefficients from Thermo~hvsi cal 

Pro~erties of Matter, Y. S. Touloukian, ed., Plenum Press, New York, B970. 

Because glass tensile strength is so dependent on surface condition, a 

single "reasonable" value was chosen for all glass strengths. 

(3) Values are typical of nuclear-grade graphite, from Industrial Gra~hi te 

Ensineering, Union Carbide Corp., 1959. 

ELEMENTARY METALLOG 

Sayyed M. Kazem 

MET Department 

Purdue University 

Knoy Hall - Room 119 

West Lafayette, Indiana 47907 

Telephone 3 17-494-7528 

55 

PRECEDiNG PAGE BLANIi a0.T FJLMEB 

ELEMENTARY METALLOG 

Sayyed M. Kazem 

MET Department, Purdue University 

West Lafayette, Indiana 47907 

Materials and Processes I (MET 141) with two one-hour lectures and one Wo-hour 

laboratory is offered to freshmen by the Mechanical En ineering Department at Purdue 

University. This elementary course, required for MET~CIMT majors, is an elective for other 

majors (IT and AT) and is also a prerequisite for other process courses (casting, welding and 

metallurgy). The goal of MET 141 is to broaden the technical background of students who 

have not yet had any college science courses. Hence, applied physics, chemistry and 

mathematics are included, and quantitative problem-solving is involved. The course outline 

consists of (1) General Inspection; (2) Properties - Physical, Chemical and Mechanical; (3) 

Processes and Selection - Metallic, Ceramcs and Plastics. The goal of the laboratory is to 

re inforce and supplement the lecture material. There are eight experiments: (I) General 

Materials Inspection; (2) Hardness; (3) Toughness; (4) Polymers; (5) Steel Heat Treatments; 

(6) Aluminum Alloy Heat Treatments; (7) Metallography; (8) Recycling. Each lab section has 

up to 24 students. Depending on the type of the experiment and the available evipment, 

some experiments may split the students into subgroups (A and B). In the metallography 

experiment, there should be a maximum of 12 students in each group for alternate weeks.' 

In an elementary metallography experiment, the objectives are: (1) Introduce the 

vocabulary and establish outlook; (2) Make qualitative observations and quantitative 

measurements; (3) Demonstrate the proper use of equipment; (4) Review basic :mathematics 

and science. 

BACKGROUND 

Metallography, a branch of physical metallurgy, is the study of the constitr~tion and 

structure of metals and alloys. When a molten metal starts to solidify, small nuclei or seeds at 

various locations and orientations are formed. On each seed the neighboring atoms attach 

themselves in an orderly manner and grow continuously at different orientations, until 

confronted by neighbors. Each dendritic growth is roughly spherical, separated from its 

neighbors by definite boundaries, and is called a "grain" or "crystal." The average diameter, 

called "grain size," is a function of nucleation rate, growth, later heat-treatment, etc. The 

grains of a pure metal have the same lattice but different orientation of their crystal axes. 

When two grains of two different orientations come in contact, the " rain boundary" is really a 

zone of mismatch2. Since these border atoms (along grain boundary5 are packed less densely 

(have fewer neighbors) they possess more energy than those others within the griain. Also, 

other atoms diffuse more easily along the boundaries than in the grain proper. This indicates 

that atoms along the boundaries are less tightly held, more reactive and energetic3. Eqosed to 

corrosives or etchants, the grain boundary dissolves more than does the grain roper. The 

etched boundary then appears as a groove (in an otherwise flat surface) and t e rnicrostmcture 

reveals black lines.4 

B 
It has been shown that most of the complex "polycrystallines" have intersections of any 

three grain boundaries at angles of 120 (see Fig. 1). Ideally, the grain structure of pure metals 

approimates the tri-corners (shown in Fig. 2.)4. Grains can be described as macroscopic or 

~croscopic. 

Grain 1 / ------i Grain 3 

Grain 2 \ 

Figure 1 Three grains at angles of 

120° to each other. 

Figure 2 bficrograph of vacuum-deposited 

alu~num film, 0.5 pm at 26,000 x. 

B/LACROSCOPIC AND MICROSCOPIC SAMPLES 

A. Qualitative E~aminationl39~ 

Macrophotography is appropriate when the grains of a s ecimen are visible to the 

naked eye or with a diametral magnification up to 50x. Examp P es of macroexamination 

include: (1) surface grains (mottling) on a cast-brass doorknob polished by normal use; (2) 

large size cirystals (spangles) on galvanized steel-sheets; (3) aluminum grains on light-poles, 

visible from the road; (4) columnar crystals at broken edges of cast-iron; (5) ice crystals at 

fractured ends of Popsicles" . 

Preparation of samples for macroexamination is usually sim le, involving less polishing 

and larger areas, for gross problems. Specimens may be burned of /' by acetylene torch, 

ed by hacksaw, then sectioned by cutter (water-cooled). After burrs are removed, the 

sample surface is laned by belt-sanders and smoothed by table grinders (water-cooled). 

Polishing is done t: y coarse 40-150 grits of emery paper. Frictional heating and structural 

distortions should be avoided. 

After surface cleaning by water, the sample is etched. Use a 10% solution of nitric acid 

(HN03) for steel structure; a 50% water solution of hydrochloric acid (HCl) or 25% solution 

of itric acid may reveal the flow-lines in forged steel and quench-cracks from heat treating. 

Mter deep etching is complete, the sample is rinsed in hot water, dipped in benzene or 

acetone, and dried in warm air-blast. When a dry surface is coated wth printer's ink, an 

impression may be transferred to art paper. Simple macrographs may even be produced by 

pencil rubbings or photographs. 

Unprocessed specimens may be examined. For example, a tensile or bending specimen 

may show ductile necking and cup-cone fracture, whereas a brittle piece may have glassysmooth fracture without necking. 
B. Quantitative Examination 

Specimens are examined and evaluated by metallurgical microscopes and reflected light 

(50-2000x). Specimen preparation is critical, since small areas are inspected and measured, 

with statistical interpretation of data. Samples are cut and smoothed as before; however, 

flame cutting and frictional heating are risky. A thin section is cut off (water-cooled) and 

mounted in "buttons" of thermoset plastic (phenolic Bakelite " , or acrylic Lucite ") about oneinch diameter and half-inch thickness. The sample surface is carefully flattened by ai wet-belt 

sander, which leaves arallel scratches. The sample is always washed (in soapy water) and 

then rotated (900) be ore P each subsequent grind or polish. Exactly 2.54 cm equals an inch. 

Polished sam les are examined by microscopes for defects which require repolishing. 

Ideally, a mirror-sur i! ace (scratch-free at 1000x) is achieved before etching. The polishers are 

usually fine emery (or diamond paste). The etchant is a weaker acid or base solution; 

conservative practice is to under-etch, then to re-etch as desired. This flushes away itbe last 

layer of "distorted atoms". 

C. Grain Size, Grain Size Number and Grain Boundary Area7B8 

Since grain size and grain bounda area of a metal are important, the American 

Society for Testing and Materials (AS+ has established reference nets with grain size 

numbers for comparison. When observed at 100x, the ASTM grain size number (n) can be 

determined from the ASTM grain size equation N = 2"-l, where N is the number of grains per 

in2. If N' is the number of grains per in2 for other than 100x, say (50x), then multipky N' by 

(100/50)2 to obtain N; then use the ASTM grain size equation. 

There are three methods to estimate grain size and determine the ASTM grain size 

number: (1) Planimeter (Jeffries) method; (2) Intercept Methods; (3) Comparison Method. 

(1) Planimeter Method: A circle or rectangle of known area (usually 5006) 

inscribed on a micrograph, or ground-glass screen of the metallograph, of known 

magnification. The magnification should be such to give at least 50 grains in the inscribed 

area. The number of grains counted within the area is added to one-half of those grains 

intersected by the boundary. The number of grains per given magnification is 

calculated readily. For a reasonable average a minimum o sentative fields should 

be tried. From known magnification, the ASW grain size can be deternined. 

This method works well with equiaxed grains; otherwise, count should be made on 

three mutually perpendicular planes determined by the longitudinal, transverse and normal 

conditions. 

(2) Intercept Methods: The intercepts, more convenient than the planimeter 

method, are reco ended for structures which depart from uniform equiaxed structures. The 

procedure may be done by hand or by machines. There are two common methods: al) Lineal 

and b) Circular. 

a) Lineal Intercept (Heyn) Method: The grain size can be estimated by counting on a 

photomicrograph (or ground-glass screen or specimen itself) the number of grains intercepted 

by one or more straight lines. Grains intersected by the end of the line count as half grains. 

For a reasonable average, counts must be made on at least three different lines. The length of 

the line, divided by the average number of grains intersected by it, gives the average intercept 

length (or grain diameter). 
b) Circular Intercept Methods: These are favored7, because circular arrays 

automatically compensate for non-equiured shapes of grains. This procedure avoids 

ovemeigltiting local portions of the sample's field and eliminates ambiguous intersections at 

straight-line ends. The manual routine is effective for grain estimation in quality control. A 

circular method is slightly biased, overvaluing the mean-intercept distance for samples with 

few intersections, but bias fades fast as intersections increase. There are two co 

procedures: i) Monocircle, and ii) Tri-circle. 

The single-circle procedure is reco ended when grain-size variation is large, and high 

precision is not required. Draw a circle of know circumference (100,200, or 25h) and 

count the intersected grain-boundaries. Different circles can be dram at different locations. 

Select the magnification to yield no less than 35 counts per circle. 

The three-circle procedure draws concentric and equally spaced circles, whose total 

circunaference is 500 mm. Subsequent steps are the same as above. 

The grain boundary area4$: In the circular intercept method, after the circle is dram 

on a photo-micrograph, the number of points of intersections per unit length of test line PL 

can be determined. If S is the boundary area per unit volume (say in2/in3), and L is the 

sum of lengths of linear eatures per Y unit test area (say in/in2) then Sv = 2PL an 8 LA = 5 PL. 

(3) Comparison Method: After the sample is prepared, the image of the 

~crcastmcture projected at lOOx (or its photograph at 100x) is compared with a series of graded 

standards (grain size charts) indexed in. four categories. Plates I, 11, 111, IV are available from 

ASTM Headquarters, 1916 Racestreet, Philadelphia, PA 19103. By direct comparison of the 

 specimen"^ microstructure with the appropriate photomicrograph of a standard grain size, one 

can select the standard photomicrograph (or interpolate between two) which most nearly 

.matches the specimen. If a specimen has two different grain-sizes, it is reported in terms of 

two numkrs, designating the approximate percent of each size. 

EQUIPMENT AND SUPPLIES 

A. Units in the Materials Laboratory of the MET Dept. 

1. Equipment: 

Cut-off wheel, deburring wheel, mounting press, belt sanders, grinding wheels, 

polishing wheels, metallographic microscopes, ventilation hood, desiccator, 

planimeter ruler, compass. 

2. Supplies: 

Metal samples (raw, polished), polishing powders (aluminum 0.3 and 0.05 

micron), ethanol, acetone, coating oil, distilled water, water glass, swab (Q-tipm); 

etchants. 

B. Notes 

The equipment and supplies are well maintained. 

Students operate equipment and handle supplies properly and cautiously 

(under instructor's supervision). 

3) The space for the above equipment and supplies is about 300-400 ft.2 (30- 

40m2). 

6. Alternatives: 

1) Using smaller portable equipment may occupy one-quarter of normal 

space. 
2) Visiting the metallography laboratory of a metallurgy or materials 

department may involve a brief walk-through or an extensive show-andtell. 

3) The last resort is obtaining a film on metallography, to elucidate proper techniques. 

PROCEDURE 

A. Observation 

1. The instructor gives an overview of metallography terms, realms, ;and 

uses. Then, students get a show-and-tell session, which may be folilowed 

by practice from sample-cutting to etching. Different students perform 

the tasks, while others watch. Under the supervision of the instructor, a 

student may be asked to cut the sample, another to debur, and a tlhird to 

mount it; other students observe, while the instructor comments on their 

safety and technique. All students take notes. 

2. Students observe commercial samples having microscopic grain, such as 

brass door-knobs and galvanized steel-plates. Full-size (lx) photographs, impressions, or prints of these metals are also exhibited. Students 

estimate grain size and grainslarea using standard charts (I-Iexagonajl or 

McQuaid-Ehn). 

3. Microphotographs of some alloys, with large or small magnificatio~ns, are 

exhibited. Students then calculate actual grain-size number from counts 

of grains (number per square inch). 

4. Micrographs of non-metallic ceramics and polymers are also exhibited. 

Some 2-D (Optical) and 3-D (Scanning Electron Microscope) views are 

compared and contrasted. Metal powders (P/M) are identified by size 

and shape, with 3-D photos. 

B. Measurements 

1. During observation and experimentation, each student makes free-hand 

sketches of equipment. Then, students sketch samples they polished, as 

observed under the microscope. They are asked to record magnification, 

identify different regions, and label phases. 

2. Photographs of different samples and various magnifications are handed 

to the students to determine grain concentration (grains/in2) or ASTM 

grain-size number by: a) line intercepts, and b) planimeter. 3. Commercial samples (brass doorknob and galvanized plate) are given to 

students to identify grain/in2 and to practice solving the formula for 

grain-size number (at lx). 

C. Rewort 

Each student prepares a report which consists of 

1. A brief theory of metallography. 

2. Basic procedures of sample preparation and sketch of a sample observed under microscope. 3. Sample calculations for grain size and ASTM grain size number. 

4. Answers to questions. 

5. Conclusions. 
Sample Calculations 

Consider the photo (lob). 

1. Using a) lineal and b) circular intercept methods, determine i) number of 

grainslarea at 100x (grainslin2, grainsIcm2) ; ii) ASTM grain size number; (iii) 

grain size (average diameter);and c) Check the above values, by planimeter 

method. 

2. Assuming d) magnification of 50x, and e) magnification of 200x, calculate 

"ASTM" grain size number in each case (at 100x). 

3. Using the circular method determine f) PL, g) SV, and h) LA for the photo 

shown. 

Solution: 

1 . a. Draw lines L1 to Lq 

at random. Measure 

lengths, and count 

the boundaryintercepts, bl to b4. 

Grains i> N=- 2 at 1 OOx 

in 

El =E2 =L3 = E4 = 3.13 in=7.95 cm 

bl = 7, b2 = 8, bq = 7 boundaries 

N=:L~(~; - 1)2 =4.01-- Grains Grains 

4 in -0.621 - cm 2 

ii) From N = 2"-', where n = ASTM Grain size number, 

InN In4.01 n=-+I=-+1= 3.0 at lOOx 

In 2 In 2 
Area 1 in 2 cm 2 iii) --- - - 0.23-- = 1.49--, at lOOx 

Grain N gran Pm 

Actud area = (L)~ 5 in 2 =2.3x10- -=1.48~10 -4 cm2 

grain N 100 Pan grain 

Average size = 0.54 x loW2 in = 1.37 x cm 

b. Circular Intercept Method: Determine the circumference C and the boundary 

intercepts b. 

C = 9.84 in; b=21 at lOOx 

b-1 Grains grains 

= 4.48 = 0. 694---'2" 

m cm 

Similarly, n = 3.15; and d = 5-33 x = 1.35 x cm 

A = Area = 7.694 in2; Grains = 27 

Grains - 27 Grains Grains grains i) N=-- = 3.51-T-- = 0.544---T 

Area 7.694 in in 2 cm 

ii) n=2.81; (iii) d = 5.34 x in = 1.35 x cm 
REFERENCES 

Widener, EL., "Materials Laboratory," MET Department Manual, Purdue University, 

Kinko's Copies, West Lafayette, IN, 1991. 

Jacobs, J.A., and Kilduff, T.F., "Engineering Materials Technology," Prentice Hall, 

Englewood Cliffs, NJ, 1985. 

VanVlack, L.H., "A Textbook of Materials Technology," Addison-Wesley, Reading, 

P\;2A, 1973. 

Brick, R.M., et al, "Structure and Properties of Engineering Materials," McGraw-Hill, 

New York, 1977. 

"Metals Handbook," 9th ed., Vol. 9, "Metallography and Microstructures," American 

Se~ciety for Metals, Metals Park, OH, 1985. 

Reed-Will, R.E., "Physical Metallur Principles," Van Nostrand, Princeton, NJ, 1964. 

Annual Book of ASTM Standards 685) Section 3, Volume 03.03, "Metallography; 

Nondestructive Testing," ASTM, Race Street, Philadelphia, PA, 1985. 

Avner, S.H., "Introduction to Physical Metallurgy," 2nd ed., McGraw-Hill, New York, 

1974. 
MBiC PROCESSING: EXPERIMENTAL 

DESIGN AND OPTBMIZATION 

Martin W. Weiser 

David N. Lauben 

Philip Madrid 

Mecfianical Engineering Department 

University of New Mexico 

P. 0. Box 999 

Albuquerque, New Mexico 87131 

Telephone 505-277-253 1 

Ceramic Processing: Experirnen~l Design and Optimization 

Martin W. Weiser, David N. Lauben, and Philip Madrid 

Mechanical Engineering Department 

University of New Mexico 

Albuquerque, NM 87131 

Keywords 

Ceramics, experimental design, Taguchi, optimization, slip casting, clay, four-point bend testing 

Objectives 

1. To gain some insight into the processing of ceramics and how green processing can affect the 

properties of ceramics. 

2. To investigate the technique of slip casting as one of the methods used to fabricate cermics. 

3. To learn how heat treatment time and temperature contribute to the properties of cermics: 

o Density, 

@ Strength, @ Effect of under and over firing. 

4. To experience some of the problems inherent in mechanically testing brittle materials and to lean 

about the statistical nature of the strength of ceramics and other brittle materials. 

5. To investigate orthogonal arrays as tools to examine the effect of many experimental pxmeters 

using a minimum number of experiments. 

6. To recognize appropriate uses for clay based ceramics developed by the slip casting process. 

7. To measure several different properties important to ceramic use and optimize them for a given 

application. 

Equipment and Supplies 

1. Three acrylic molds for slip casting bars as shown in Figure 1. 

2. Six plaster bats for slip casting the bars as described in appendix B. 

3. A programmable furnace capable of 1200°C with a minimum hearth size of one square foot and 

height of three inches. It is possible to use a furnace with a smaller hearth size or that is not 

programmable but this will require more firing(s) andlor more supervision. 

4. Approximately two kilograms each of an earthenware clay such as redart* and a moderate stonewae 

clay such as goldart*. Other materials may be substituted for the earthenware and stonewxe clays to 

change the experimental results for variety andlor a different firing temperature. Suggested 

replacements are ball clay or kaolin for the stoneware clay and fluxes such as feldspar or talc for the 

This work was supported in part by a grant from the University of New Mexico Teaching 

Allocation Subcommittee. * Cedar Heights Clay but available from most local ceramic suppliers. 
ewenwxe clay. Replacing one or more of the clays will require the relative amounts of the 

conqponemts to be adjusted. 

5. A minimum of three 500 ml wide mouth bottles for mixing the slips. 

6, A 50 to 200 ml buret for adding the dispersant solution. 

7. 50 rnl of a polymeric dispersant such as the Daxad series of sodium salts of polyacrylic acid (PM) 

or polymethylacrylic acid (PMAA)+ or onium salts of PAA or PMAA.* 

8. Approxinnately one kilogram of coarse grog if this parameter is to be varied. 

General Bxkground 

This laboratosy experiment is designed to familiarize students with some of the processing techniques and 

propeaies of ceramics. This is necessary since advanced ceramics have been proposed for a wide variety 

of applications, many of which were unheard of just twenty years ago. This results from factors that 

include: realization of how diverse ceramic properties are, the desire to operate equipment in more 

extreme conditiions, and improved reliability stemming from better processing and materials design. This 

experiment will describe some of the properties of ceramics and investigate the processing and properties 

of a relatively simple ceramic, structural clay. 

Cermics are a broad class of materials that exhibit diverse properties. They are most conmonly divided 

into several chemical groups that include the oxides (A1203, SiO,, MgO, etc.), nitrides (AIN, Si3N,, BN, 

etc.), cxbides (Sic, B,C, Tic, etc.), halides (NaCl, KCl, LiF, etc.) and many other inorganic compounds. Some common applications are window and container glass which are amorphous solid solutions 

of SiO,, CaO, Na,O and other oxides, sharpening stones composed of alumina (A1203) or silicon carbide 

(Sic) md transducers that are used in nearly all forms of electro-acoustic (speakers) equipment based upon 

BaTiO, and related materials. Of great economic importance are ceramics used as refractories to contain 

molten metals or glasses (silica-SiO,, mullite-3A1203@2Si02, and zirconia-ZrO,), and as sensors (c-ZrO,). 

More recent ag~plications are in thermal engines (A1203, Sic, Si,N,, and MoSi,), fiber optics (SiO, and 

phosphide glasses), and superconductors (YBa2Cu30,). The previous discussion shows that ceramics ae 

very impodant products in both everyday life and for the production of other materials. 

There are four primary properties that come to mind when ceramics are discussed; resistance to high 

temperature, corrosion resistance, high hardness, and brittleness. The first three of these properties are 

normally assets, while the last is generally considered detrimental for most applications (grinding and 

polishing media are an exception). It is the first three properties that are currently driving the 

investigation of the use of ceramics for applications such as thermal engines while the fourth presents 

mmy of the m,ajor obstacles to more widespread use. 

Mmy of the problems with brittleness in ceramics can be overcome by the use of ceramic matrix 

composites anclior use of improved processing techniques. Ceramic composites attack the brittleness 

problem directly by making the material more difficult to fracture (toughening) while irnproved processing 

techniques aMernpt to eliminate the pre-existing flaws that are normally the initiation site for fracture. 

Toughening methods currently in use include: fiber or whisker reinforcement to bridge cracks, particle 

reinforcement .to deflect cracks, and transformation toughening to push cracks closed. Each of these 

Daad 37LN and 30, W.R. Grace & Co. 

Dxvan C and 821-A, R.T. Vanderbilt Company, Inc. 
techniques has both advantages and disadvantages, but the use of any of them makes the cermic more 

difficult to fabricate. 

A significant amount of research has been done recently that has focussed on improved cermic processing 

techniques after it was recognized that removing the strength limiting flaws during the latea- stages of 

fabrication was a difficult process. Several approaches have been investigated including both colloidal 

routes to improve consolidation of powders such as pressure filtration and chemical routes to form the 

ceramic in situ such as chemical vapor infiltration. There have been notable successes in both xeas with 

selected materials but no single technique has emerged as the ultimate method for ceramic fabrication. 

Experimental Background 

This experiment uses an inexpensive, easily processed ceramic to illustrate some of the principles of' 

ceramic fabrication and mechanical properties. Unfortunately, this material has a complex chemical and 

phase structure. Detailed analysis of the processing kinetics and resultant microstructure would be 

difficult for the ceramic examined in this laboratory, especially for a course of this depth. However, 

certain trends or correlations can still be observed and explained based on general principles of cermic 

science. Several simpler systems could have been used for this experiment, but they were 1eie87er too 

expensive, toxic, difficult to process, required too high a heat treatment temperature, or a ctombination of 

these factors. 

The processing of ceramics can be broken down into two major steps: the formation of the green body and 

the heat treatment to form the final product. The term green body comes from the early ponerqr indushq 

and denotes the ceramic in a consolidated, friable state prior to heat treatment. The green body is 

normally formed by one of four methods. These are packing individual ceramic powder parhicles toge&er 

by dry pressing, extrusion of a plastic body, injection molding, and slip casting. Heat treat,ment of 

ceramics is also known as firing which is also a vestige from pottery. It is carried out at high 

temperatures (800 to 2500°C) in a furnace that is often designed to allow a controlled atmosphere 

surrounding the sample. 

The specimens for this experiment are to be processed by slip casting. Slip casting involves the 

production of a liquid slurry or slip from the dry components and pouring the slip into molds where it 

solidifies. The slip is made by adding the ceramic powder to a liquid solvent which lubricaltes and 

disperses the powder particles. The most common solvent is water, but a number of alcohols and organic 

solvents have been used in specialized cases. The dispersion of the powder particles in the solvent 

depends strongly on the nature of the particlelsolvent interface and the electrostatic forces bemeen the 

particles. The interface and electrostatic forces can be modified by changing the pH (acidiQ/alkaliinityp of 

the solvent andlor the addition of dispersants and binders that bond to the particles. These dispersms are 

normally organic molecules that are related to the surfactants found in detergents. One of tibe principle 

reasons for controlling the interfacial behavior of the particles is to allow the slip to be highly concentrated 

while having a reasonable viscosity. This is often referred to as a high solids loading of the slip. The 

high solids loading makes it easier to form a homogeneous green body with fewer voids. 

A typical slip casting mold is designed to draw the water out of the slip through one or more mold 

surfaces. Porous plaster bats are often used to draw the water out of the slip by capillary action. Since 

plaster is easily fabricated and quite effective at holding water, it is one of the rnost commonily used 
materials for this process. However, technologies based upon a permeable membrane are also used that 

permit the water to be either pressed or sucked out of the slip. 

This experiment uses an acrylic mold to contain the slip in the vertical plane. The mold is placed on top 

sf a plaster bat to support the slip and remove water as shown in Figure 1. This geometry results in 

unidirectional water flow in the forming green body through the bottom of the sample. This yields more 

uniform samples than slip casting in a mold cavity in which the water is drawn off in more than one 

direction. After the green body is solid enough to hold its shape, the acrylic mold is removed and the 

sample is dried further in air. Nearly all the remaining water which is not chemically bonded to the 

cermic powder can be removed by oven drying the sample at about 80°C. At this point the green body 

is quite porous and still contains a considerable amount of chemical water and the dispersants. The 

samples are weak and must be handled with care prior to firing. 

Figure 1 The mold and plaster bat used to slip cast the ceramic samples. 

During the firing operation several different phenomena occur. The first of these is that the chemically 

bonded water is driven off in the 100-400°C range. This water is part of the crystal structure of the 

cermic powders such as kaolinite (A12(Si205)(OH),). Kaolinite typically decomposes into alumina (A120,) 

and silica (SiO,) when the water is driven off. This reaction is irreversible except under extreme 

conditions. The next step in the process is for the particles to begin sintering together, allowing the 

system to reduce its internal surface energy. Sintering is a diffusion controlled process where the rate 

exponentially increases with temperature. In some ceramics, materials are included that form low melting 
liquids that can greatly enhance the diffusion and sintering rates. These materials are normially referred to 

as fluxes. These liquids may be absorbed by the bulk of the material which is known as trmsient liquid 

phase sintering or they may remain in the ceramic component as glasses or second phases upon cooling. 

The firing temperatures of the clays are frequently cited in terms of a pyrometric cone rather thm a 

specific temperature. Pyrometric cones are used because they integrate the effect of temperature over time 

on a standard ceramic composition. The pyrometric cone gives a better representation of the cowaplex 

reactions occurring during ceramic firing than would a simple measure of the temperature. Pyrometric 

cones are narrow triangular pyramids of a tightly controlled ceramic composition. They are normally 1.5 

to 3 inches tall and are fired in the same fkrnace as the product being processed. The cones are placed 

with their long axis at an 8" angle from vertical and allowed to deform under the influence of gravity 

during the firing as the material softens under the combined effects of temperature and time: at 

temperature. 

The pyrometric cone gives a visual measure of the firing process since the tip of the cone will faill over as 

it deforms. A firing is said to have achieved a certain pyrometric cone if the cone with hail number bends 

so the that tip of the cone is at one-half of the original cone height. Normally a series of three or more 

cones are used to allow the progress of the firing to be followed. The cones are numbered from 040 at 

the lowest firing temperatures to 50 with the highest firing temperatures. A leading zero, i.e. 06 or 810, 

is the equivalent of a negative sign before the other digits. Typical terra cotta is fired at cone 010 to 04, 

stoneware at cone 6 to 10, artistic porcelain at cone 10 to 15, and industrial porcelain such as spxfl-kglugs 

at approximately cone 20. Pyrometric cones have been fired using various carefully contrcllled tirnetemperature profiles (heating rates of 1 or 5"CImin followed by a moderate quench) to determine the 

temperature equivalent. 

Experimental Materials 

Two different types of pottery clay are used in this experiment because they are readily available, 

inexpensive, non-toxic, and can be fired at temperatures of less than 1200°C. This is a significantly Bower 

temperature than required for most of the advanced ceramics and is within the capabilities of mmy 

furnaces that are available in materials processing laboratories. The redart clay contains a relatively large 

fraction of fluxes and can be fired at temperatures below 1200°C. The goldart clay contains less flux md 

as a result is more refractory. The compositions and properties of the clays that are to be used in this 

experiment are summarized in Table I. 

The compositions are supplied in terms of their oxide equivalents even though the elements are not 

necessarily distributed in this fashion. Most of the material will be present as various types of silicates 

such as kaolinite, illite, silica, and ferrous oxides. Kaolinite is a sheet silicate with a chemical 

composition of Al,(Si2O5)(OH), which can be contaminated with most of the other elements. It forms Lhe 

basis of most clays and is present in the form of small platelike particles that contribute significmtly to the 

plasticity of the clay. Illite is one of the principal fluxes in this system and is normally morphous with a 

composition of A12~xMgxK,~x,(Si,~55,,A10,5+Y05)(OH,). The variables x and y in this formula indicate that the 

composition is variable and depends upon the relative abundance of the three cations, K+l? l~Ig+~, and

AP3. The chemical formula of silica is SiO, which is normally present as a-quartz. The ferrous oxides 

are FeO, Fe203, and Fe304 which either form small particles or are included as part of the strucbre of one 

of the other components. 
Table I Nominal Composition ad Properties of the Clays Used in this Experiment 

Colnposition (wt%) 

Silica (SiO,) 

Alumina (Al,03) 

Iron Oxide (Fe203) 

Titania (TiO,) 

Magnesia (MgO) 

Calcia (CaO) 

Soda (Na,O) 

Potassia (K,O) 

Sulfur (S) 

Redart 

64.27 

16.41 

7.04 

1.06 

1.55 

0.23 

0.40 

4.07 

Goldart 

56.72 

27.30 

1.42 

1.75 

0.42 

0.22 

0.16 

1.87 

0.12 

Loss on Ignition 4.92 10.03 

Standard Firing Cone 04 6 

Std. Cone Temp @ 1 "Clmin 1060°C 1230°C 

Fired Shrinkage (-Alllo) 

Cone 05 

Cone 1 

Cone 3 

Cone 10 

Absorption (wt% W,O) 

Cone 05 

Cone 1 

Cone 3 

Cone 10 

From Data Sheets supplied by Cedar Heights Clay 

Exmination of the composition data shows that redart contains significantly more of the fluxes (FqO,, 

MgO, Na,O, and K20) and less Al,03 than the goldart. This difference in composition reduces the firing 

temperature redart clay. The ferrous oxides result in the reddish color of both the green and fired clay 

body. The clays exhibit similar firing shrinkages and amounts of porosity (percent water absorption) at 

the lowest firing temperatures listed (A05). However, the goldart remains significantly more porous at 

intermediate tenlperatures (A1) and only achieves nearly completely closed porosity at much higher 

remperamres (810). It should also be noted that the goldart clay contains more organic matter as indicated 

by the higher loss on ignition. 

Processing Parameters 

There are a multitude of different parameters that affect the properties of a ceramic. Some of these are of 

an intrinsic nature and depend upon the type of ceramic material used. However, the vast majority of the 

pzameters are process related and may be controlled by the experimentalist. The properties of ceramics 
are probably more dependent on the processing than most other classes of materials. The following list 

sumarizes many of the different parameters and how they affect the processing and properties. 

Composition - Clay based ceramics are composed of three primary types of oxides: refractories, glass 

formers, and fluxes along with reinforcements. 

s Refractory components such as Al,O, and Cr203 have high melting temperatures and increase the 

firing temperature of the clay body. r Glass Forrners such as SiO, and B,O, form a vitreous (glassy) matrix which holds the more 

refractory particles together. 

Fluxes such as Li,O, Na,O, K,O, MgO, CaO, and FeO, enter the glass network and assist in 

dissolving the refractory elements into the glassy matrix. As a result the fluxes lower the melting 

temperature of the glass and the firing temperature of the body. o Reinforcements can be added to the material in order to modify the properties. In clay based 

ceramics the most common are granules of previously fired clay ranging from 20 psn to 2 m in 

diameter known as grog. Grog is added to control drying shrinkage and improve the drying rate 

Different types of particles, fibers, and flakes are added to other ceramics in order to modify the 

properties by forming a composite. The most common purpose is to improve the mechmical 

properties, particularly the fracture toughness. 

In this experiment the composition of the body is controlled by altering the proportions of the different 

clays. The use of a higher fraction of the refractory clay should increase the necessary firing temperahre 

but the effect is rarely linear. In addition, this should increase the strength of the product if the sarnples 

are fired to the same fraction of theoretical density since the crystalline phases that incorporate the 

refractory oxides are stronger than the vitreous phases based upon silica. 

Green Processing - The green processing technique employed will have a dramatic effect on the 

properties since many of the strength limiting flaws are introduced during this step. 

Dry Pressing is very fast and efficient but there is a tendency for the particles to bridge voids md 

leave large pores behind. In addition the shapes that can be dry pressed are limited (due to the need 

to uniformly distribute the pressing stresses. 

Extrusion of a plastic (moist and easily deformed) ceramic material is a good method to produce 

pieces of uniform cross section. However, the process is limited to producing parts with a uniform 

cross section and only certain ceramic materials can be formed into a plastic suspension. @ Injection Molding incorporates the ceramic powder into a polymeric base that is molded under 

pressure to the desired shape. This is an expensive process and there is normally a large mount of 

polymer that must be removed during the later stages of processing by either burning it out or 

converting it into a desirable ceramic phase. @ Slip Casting is very useful for producing high quality parts with complex shapes. Proper dispersion 

of the ceramic powder virtually insures that no large voids will be formed and complex shapes can 

be made with properly designed molds. 

Slip Casting - The properties of the slip cast part are strongly dependent upon the nature of the slip that is 

used to cast the parts. A well dispersed slip with a high solids loading normally results in a high densiv, 

homogeneous green body. 

Solvent choice influences the viscosity of the slip, the ability to disperse the ceramic particles, land 

the ability to dry the green body. Water is the most frequently used solvent because it disperses 

oxides fairly well, has a low viscosity, and is easy to remove from the green body. 
Slip pH has a strong effect on the dispersion of the powder particles. The primq force that 

prevents I;he particles from flocculating (clumping together) is electrostatic repulsion between particle 

surfaces. The pH of the slip influences the surface charge of the particles with flocculation 

occurring when the surface charge approaches zero (the isoelectric point). However, extreme pH's 

@igk or low) can increase flocculation due to the high ionic strength of the slip. 

Dispersants are frequently added to the slip to modify the electrostatic repulsion between particles 

and allow either the solids loading of the slip to be increased or the viscosity to be decreased. They 

work by binding to the particle surfaces and preventing the particles from approaching each other 

too closely. Too much dispersant will increase the viscosity of the slip since most dispersants are 

mode rat el:^ high molecular weight linear polymers. This experiment utilizes one of the salts of 

either polyacrylic or polymethylacrylic acid as a dispersant. 

Binders and plasticizers are sometimes added to the slip to increase the strength of the green body. 

These are normally low molecular weight polymers that can be induced to cross-link after the green 

body is dried. 

Firing - The firing process removes the organics and chemically bonded water from the ceramic compact 

md fuses the particles together into a solid mass. In addition, it may result in densification and the 

elimination of p'ores. 

Temperature of firing normally refers to the maximum temperature during the firing process. The 

firing temperature must be high enough to cause the particles to fuse together and densify if desired. 

But it must be low enough to prevent sagging due to high temperature creep and grain growth, 

paflicularly abnormal grain growth where a few grains become much larger than the rest. Optimal 

firing of rnany ceramics is accomplished by a complex combination of ramps and holds at various 

ternperah~res in order to promote different reactions or diffusion mechanisms at different points in 

the firing process. 

Time normally refers to the hold time at the maximum firing temperature. It must be long enough 

for the particles to fuse together and densify but short enough to prevent creep and grain growth. (P Rmp Rate is the rate at which the furnace is heated and cooled from one temperature to another. 

Too high a ramp rate can cause a variety of problems such as uneven heating causing thermal 

stresses, trapping of gases that evolve as the organics break down, and thermal shock as phase 

trmsitions occur. Too slow a ramp rate wastes energy and may favor diffusion processes during 

sintering that lead to undesirable results. A number of different ramp rates are frequently employed 

over different temperature ranges to optimize the process in these temperature ranges. Clay based 

cermics are susceptible to cracking due to the a to B quartz transition at 573°C and the evolution of 

chemical water at 100 to 250°C. Consequently, low ramp rates are typical in these temperature 

ranges, particularly for large sections. 

Errpesimenahl Design and Response 

This laboratory experiment is intended to simulate the development process for ceramic materials that 

might be employed in commercial or industrial use. Specimen testing is intended to demonstrate that by 

altering the parameters associated with ceramic processing, the properties are directly affected. Four 

dissimilar parameters, each having a significant effect on the property characteristics, are studied in the 

laboratorgr. These parameters should be preselected from those listed in Table 11. Also in this table is 

listed the range for each parameter. These ranges are judged suitable for this experiment based on their 

feasibility and whether they would prove to have a significant bearing toward the results. 
Table 11 Possible Settings of the Experimental Parameters 

Parameters 

Composition (wt % refractory clay) 

Inclusions (wt % of total clay) 

Dispersant type 

Dispersant concentration by volume 

Peak firing temperature (AT from mean) 

Peak firing time 

Ramp rate 

Range or Tvpe of Se:aing 

0 to 100% 

0 to 20% 

Na-PAA, Na-PMAA, NH,-PPa4?. 

0 to 2% 

-100 to iooOe 

0 to 8 hrs 

1 to 10°C/min 

Each parameter selected for study will be allowed to take on three specific values from within these 

ranges. These settings are referred to as levels for the designed experiment. The precise levels for each 

parmeter will be selected so that they will have the potential for influencing the system response. The 

specific parameter as well as the values for the parameter levels should be selected by the course . 

instructor(s) prior to the beginning of the experiment. The nomenclature used to describe each of the 

parameters and levels will be selected by the class during the first laboratory lecture. 

The effect of each of the chosen parameters on the quality of the product will be examined through the use 

of the additivity theory and Taguchi's signal-to-noise method. These techniques allow the relative effects 

of each of the parameters to be evaluated and the combination of the parameters that will result in an 

optimal product to be predicted. 

The measured result of the experiment is referred to as the response. The objective of this experimental 

process is to determine how the optimal response may be obtained. If multiple responses are exmined, as 

is the case with this experiment, the overall optimal response of the system may not be the ol?kimal 

situation for any of the individual responses. This is where engineering judgement is needed. This 

experiment is designed to allow evaluation of the individual responses listed in Table 111. 

Table III Plausible Individual Measured Responses 

Strength as measured by maximum bending stress 

Final mass density 

Fractional porosity 

Deformation during firing (sagging) 

Firing shrinkage 

Optimizing the overall performance of the product may involve maximizing one response such as strenga 

while minimizing another. The student will be called upon to decide what the optimal performance of the 

product is based upon those responses that are measured and to determine how the overall performance 

can be optimized. 

In this experiment we intend to investigate the effect of four of the eight different parameters listed in 

Table I1 at three levels each. If all of the possible combinations of four parameters at three levels each 

were investigated employing the traditional scientific method, a total of 81 different experimej~ts (3" or 

test conditions would have to be conducted. In addition, testing only a single specimen from1 each 

experiment would not yield information on the repeatability of the experiment or the effect of noises 

associated with the different parameters. Conducting several replications (several tests of the same 
experiment) !lvould soon make the total number of tests to be conducted prohibitive. This problem is 

circumvenkd by using the method of orthogonal arrays to allow the effects of each of the parameters to be 

asceaained with a minimum number of experiments. In this laboratony experiment an L9 orthogonal array 

will be used ,which allows four parameters to be tested at three levels each, using only 9 test conditions. 

A number of specimens can then be fabricated under each test condition to gain statistical information 

about the product without requiring an inordinate amount of work. 

'Table BV shows the L9 orLhogonal array that will be used in this laboramry experiment. Once the four 

!pxmeterrs a.nd each of their three levels to be investigated are selected they will be randomly assigned as 

pameters A, B, 6, and D. The random assigment of the actual parameters to the colum of the 

o&ogcsnal arays helps insure that the investigator does not unduly influence the outcome of the 

experiment. It also dramatically lowers the probabilitg: that exactly the same set of experiments will be 

conducted in the lab in the near future. A number of samples will be tested for some of the responses and 

as such the indicated response in the table will be the average of all of the individual responses. The 

streng~ and density responses are such responses while the sagging response will only be measured once 

since measurement of it is mutually exclusive of measurement of most of the other responses. 

Table IV The L9 Orthogonal Array and Sample Responses 

Levels for each Parameter Responses 

- Em - ABCD Strength Density Deformation 

Through the (data reduction process associated with the Taguchi method the effect of each parameter on 

each of the nrleasured responses is found along with an optimal combination of parameter levels for each 

response. Two examples of this method of data reduction are provided in Appendix A. If the condition 

for a pmiculx response is not one of the original nine experimental conditions, a confirming experiment 

must be conducted. The confirming experiment will be based upon the combination of parameters that 

predict the optimal response. 
Procedure 

1. Determine which parameters are to be explored in this experiment and the three values of each 

parameter to be investigated. Assign a level (1, 2, or 3) to each of the different values in either 

ascending or descending order if possible. 

2. Randomly assign each of the different parameters to one of the columns in the orthogonal array (A, 

B, C, or D). 

3. Translate the combinations of parameters and levels in the L9 orthogonal array into the actual 

experiments to be conducted. Assign the experiments to the different laboratory groups in as 

random a fashion as possible to minimize bias introduced by different investigators wir;hout 

causing excessive duplication of effort. 

4. Slip cast the samples using the following procedure. 

a. Fill a buret with dispersant solution of the appropriate pH and dispersant concentration as 

determined by the experimental condition. 

b. Weigh out a 300 gram batch of the clay(s). Make sure that the proper amount of each 

of the different clays is used. Mix the dry ingredients until they appear homogeneous 

to the naked eye. 

c. Measure 50 ml of the dispersant solution into a 500 ml wide mouth bottle. 

d. Slowly add the clay mixture to the dispersant solution while stirring. The goal is a slip with a 

viscosity of = 100 to 1000 cp (consistency between glycerol and honey) so it will probably be 

necessary to add more dispersant solution. 

e. Once all of the clay has been added shake the bottle vigorously for a couple of minutes to 

break up any agglomerates and thoroughly mix the materials. It will probably be necessary to 

add more dispersant during this process as the liquid completely wets the powder. 

f. Record the total amount of dispersant fluid used in order to calculate the solids loading of the 

slip. 

g. Prepare a plexiglass mold by coating the interior surfaces with a thin layer of petroleum jelly, 

h. Clean a plaster bat thoroughly and scrap the surface flat using the aluminum straight edge. 

i. Slip cast seven samples for each experimental condition in the plexiglass molds on the clean 

plaster bat. Fill each of the slots to the top edge and keep filling them for about BO minutes 

by continually adding more slip. Allowing the slip level to drop too low will create voids in 

the center of the sample. 

j. Dry the specimens on the plaster bat for about 24 hrs. 

k. Oven dry the specimens at = 80°C for an additional 24 hrs. This ensures that all of the 

physical water has been removed from the powder compact. 

1. Trim and grind the specimens using 150 to 240 grit sandpaper to obtain a rectangular shape. 

m. Carefully engrave the end of the bars with a sharp object such as a pin or X-acto knife so that 

they can be identified after firing. Store the specimens in a labeled jar taking care not to 

break them. They are very fragile at this time. 

5. Fire the specimens using the peak time, peak temperature, and ramp rates defined by t!he parameter 

levels of the orthogonal array. Dust the bottom shelf of the furnace with refractory clay to prevent 

the bars from sticking to it and place all but one specimen on edge in a neat row. Set the remaining 

bar across the two point support (three inches apart with a minimum of one inch clearance to the 

shelf) for measurement of deformation during firing. 

6. Test the strength of the relatively straight bars using the four point bend fixture in the lload frame. 

Record the maximum strength data of all bars from a single test condition on a single sheet of 

plotting paper. 

7. Measure the density of the specimens using Archimedes' method. 
8. Conduct the confirming experiment(s) if required. 

We have conducted this experiment during the Spring and Fall 1991 semesters in a class of approximately 

30 Mechanica.1 Engineering seniors. The experiment requires approximately three three-hour laboratory 

periods to conduct. The laboratory periods are spread over three weeks to allow time for processing steps 

such as drying and firing of the samples. During the Spring semester the clay body composition, pH of 

the slip, the firing temperature, and the firing duration were varied. During the Fall semester the firing 

duration was replaced by the inclusion of different fractions of grog (prefired clay granules) and the 

ranges of the other variables were modified based upon our experience during the Spring semester. We 

will present the results from the Fall 1991 semester here. 

The parameters and their levels for the experiment that was conducted are presented in Table V. The 

slips were dispersed with Daxad 305 and ammonium hydroxide to achieve the desired pH. The furnace 

was heated and cooled at S°C/min and held at temperature for 1 hr. The top and bottom surfaces of the 

sample bars vvere ground flat and approximately parallel on a 180 grit belt grinder lubricated with flowing 

water prior to mechanical testing and the broken bars were then used to measure the density of the sample 

via ~rchimedes'method. However, the results of the density measurements are not presented here due to 

space limitations. 

Table V Parameters and Levels for the Fall 1991 Ceramics Experiment 

Parameter Variable 

Levels 

- 1 - 2 - 3 

A Fraction Redart Clay 0.60 0.80 1 .00 

B Fraction Grog 0.00 0.10 0.20 

C pH of Dispersant 7 10 12 

D Firing Temperature ("C) 1050 1100 1150 

The flexural strength as measured in four point bending is presented in Table VI for each of the different 

experiments. The Taguchi signal-to-noise ratio, q, was calculated using the more is better criterion as 

presented in appendix A. The particular combination of parameter levels used for each experiment can be 

found by inserting the values given in Table V into the definition of the L9 orthogonal array given in 

Table IV. 

Based upon these results the effect of each of the different parameters at each of the different levels was 

calculated foir both the flexural strength and q. The results of these calculations are shown in Table VII 

and plotted later in Figure 2. 

The optimum condition was assumed to be the maximum strength and it is always desired to achieve the 

maximum value of the Taguchi signal-to-noise ratio, q. The maximum flexural strength was predicted to 
Table VI Flexural Strength (MPa) of the Ceramic Bars 

Experiment Replication 

1234567 

1 2.83 1.98 2.41 3.02 3.35 2.59 

2 3.56 3.11 2.98 3.24 3.34 3.87 2.97 

3 3.43 3.01 3.53 3.37 3.93 

4 8.74 8.11 8.18 8.23 8.67 7.13 6.92 

5 2.55 2.37 2.06 2.19 2.06 2.53 2.19 

6 3.54 3.61 3.40 3.80 4.54 

7 6.71 3.77 5.39 7.03 7.55 5.27 5.44 

8 6.59 5.47 6.94 6.50 6.48 6.69 6.42 

9 3.52 3.21 3.12 3.25 3.24 3.24 2.82 

Mean 

2.70 

3.30 

3.45 

8.00 

2.80 

3.78 

5.88 

6.44 

3.20 

Overall Mean 4.34 11.84 

Table VII Parameter Effects for the Flexural Strength and 7 

Parameter Flexural Strength (MPa) Taguchi 7 (dB) 

1 2 3 1 2 3 

A -139 0:3 5 0,8 4 -2: 1 0.3 1 120 

B 1.19 -0.33 -0.86 1.81 -0.69 -1. IL2 

C -0.30 0.50 -0.47 0.09 0.92 -1.01 

D -1.61 -0.20 1.63 -3.38 0.30 3.08 

be 8.50 MPa for experimental condition A3BlC,D3 and the maximum 7 was predicted to be 119.45 dB for 

the same experimental condition. This confirming experiment was performed along with A,B,GI,D, which 

was predicted to have both the second best flexural strength and 7. The results of these confirming 

experiments are presented in Table VIII. 

Table VIII Flexural Strength (MPa) for the Confirming Experimenb 

Condition Replication Mean SIN 

1234567 

C,D3 9.78 8.68 8.48 6.87 8.5811.14 4.51 8.30 17.32 

A~BICID~ 8.31 8.83 9.18 9.27 9.71 7.94 9.90 9.02 19.03 

Discussion 

The experiment was performed rather smoothly and there were a couple of mild surprises that helped 

make this a real experiment rather than a cut anddried exercise.Examination of the data in Table VI shows 

that there was some variability in the flexural strength of the samples as is expected in brittle materials 

where the strength is often controlled by flaws. However, the variability was not so great as to render the 

data useless for explaining how changing the parameters can affect the strength. 
The effects of the parameters are shown in Table VII and Figure 2 where it is seen that the firing 

temperamre had the greatest effect upon the strength followed by the two different material composition 

factors. This is more or less as expected since sintering is a diffusional process and the rate of diffusion 

increases exponentially with increasing temperature. The first surprise to the students is that the strength 

is nearly a linear function of the firing temperature which does not agree with the diffusional nature of the 

sintering process. This can be explained based upon the competition between densification and grain 

growlh that occurs during sintering. Brittle materials with larger grains typically exhibit lower strengths 

than similar materials with smaller grains since the size of the largest flaw in the material normally scales 

wih the grain size. However, no microscopy was performed to check this theory. 

Fraction Redart Fraction Grog Dispersant pH Firing Temperature 

4 1 

-4 e-L I I I t I t I I I I I 

0.60 0.80 1 .00 0.00 0.10 0.20 7 10 12 1050 1100 1150 

IFsaction Redart Fraction Grog Dispersant pH Firing Temperature 

Figure 2 The parameter effects for the flexural strength and the Taguchi signal-to-noise ratio, q. 

The oher surprise was that the confirming experiment that was predicted to have the largest flexural 

strength and optimum Taguchi signal-to-noise ratio did not have the best values. However, it did have a 

higher strength and a good value of q compared to the nine original experiments. The second confirming 

experiment, which was predicted to have the second best strength and q, resulted in the best values 

obtained during the course of this investigation. This indicates that there were interactions between the 

parameters ha.t are not accounted for in the Taguchi Experimental Method. It might also be possible to 

explain this result based upon the inconsistent processing since the flexural strength for the first 
confirming experiment had the greatest variabiliv of all of the experiments performed even ljhough the 

Taguchi signal-to-noise ratio predicted that it would have relatively small variabiliv. It would probably be 

a wise idea to remn the experiment to check this hypothesis. 

The values obtained for both the flexural strength and y for the second confirming experimenlt agreed 

reasonably well with the predicted values for the first confirming experimena&. In addition, the conditions 

for the hivo experiments only vxied in the least significant experimental parmeter. This finding is in 

good agreement with the fact &at the effects from the least significant parmeters should not really be 

used to make predictions since they often fall below the level of the noise in the system. Thiis can be 

tested by performing analysis of variance (ANOVA), however, this was not done in this case. It also 

points out the fact that it is normally a good idea to perform the experiment that is predicted to have the 

second and possibly the third best response in order to find the true optimum response of the system. 

'This experiment is a very good hands on introduction to ceramic processing and properties along with he 

Taguchi Method of Experimental Design. The results agree fairly well with theory so they can be 

explained to all but the most introducto~ Materials Science classes. However, the system is not so well 

behaved that there are no surprises. This property is very useful as a tool to acquaint the student with the 

fact that real experiments rarely go exactly as planned. In addition, there are a wide variety of pxmeters 

that can be easily varied so that exactly the same experiment is never performed twice. This prevents the 

students from using a file to write up the results and keeps the instructor interested since there will always 

be something that is a little bit different from the last time the experiment was performed. 

References 

1 M.S. Phadke, , Prentice Hall, NJ 1989,. 

2 W.D. Kingery, H.K. Bowen, and D.R. Uhlmmn, Introduction to Ceramics, 3"d Edition, John Wiley 

& Sons, New York 1976- 

3 P. Boch, "Ceramic Processes: Powders in Suspensions - Slip Casting", J. Mater. Educ.,, 6 131 365- 

97 (1984). 

4 6. Taguchi, Jikken Keikakuho, Vol. 1 and 2, 3"d Edition (in Japanese), Mmzen, Tokyo Japan, 1977 

and 1978 English Translation: 6. Taguchi, System of Experimental Design, VoE. 1 amT 2, ed.by D. 

Clausing, UNIPUBIKraus International Publications, New York, 1987. 

5 P.J. Ross, , McGraw Hill, 1988. 

6 L. Panchula and J.W. Patterson, "Demonstration of a Simple Screening Strategy for Multifactor 

Experiments in Engineering", in National Educators Workshop: Standard Experiments in Materials, 

Science. & Technoloyy , ed. by J. A. Jacobs and J. Harris, National Institute for Science and 

Technology, Gaithersberg , MD 1990 . 
Appendix A Taguchi Method Design of Experiments 

Introduction 

The traditional method of investigating the effect of multi-factor or multi-parameter system response is to 

systematically vary each parameter while simultaneously holding all others constant. This method is very 

useful for exlploring how a single parameter influences the response. However, it becomes time intensive 

and costly when many parameters and/or many different parameter settings are investigated. For example, 

malysis of a four parameter system with three levels for each parameter requires 81 different experiments 

(39. Conduicting every possible combination for a given set of parameters and levels is referred to as a 

full facmorial experiment. If one considers that each experiment should be performed a number of times to 

verify that ale results are reproducible it is seen that hundreds of experiments may be needed to fully 

investigate this relatively simple system. 

marakhlly there are alternative strategies available that dramatically decrease the required nuder of 

experiments. The most familiar of these, and the method associated with certain laboratory experiments 

(of this course, is the orthogonal array. With orthogonal arrays, as well as other alternative test strategies, 

it is comon for the volume of information concerning a particular physical relationship to be reduced 

somewhat. However, provided certain stipulations are met, the data can still be highly informative. The 

odogonal array is an ordered test sequence that permits statistical comparisons of test results on a partial 

factorial basis. Its chief advantage is that it allows the experimenter to rapidly determine what factors are 

critical and to what degree. 

(Orthogonal '4rrays 

Ohogonal asrays were first conceived by Jacques Wadamard, a French mathematician, in 1897. His 

purpose was to develop an optimal mathematical system that would allow accurate evaluation of that 

system" results without a full factorial arrangement. However, it was Genichi Taguchi, a Japanese 

expert in quality control and assurance, who incorporated these arrays into the manufacturing and 

design engineering realm. Taguchi also developed a method (to be discussed later in this appendix) that 

accurately accounts for the statistical variability of the experimental results. 

The use of or~ogonal arrays decreases the number of required experiments to the minimum dictated by 

the degrees of freedom present in the system. To demonstrate how degrees of freedom are evaluated, it is 

helghii to make a comparative analogy with an important concept of materials science: the Gibbs Phase 

Rule for phase equilibria. The Gibbs Phase Rule is expressed as P + F = C + 2, where P is the number 

of phases, F is the number of degrees of freedom, C is the number of components, and "2" is the number 

of default degrees of freedom corresponding to pressure and temperature. The number of degrees of 

freedom in designed experiments is generated in a similar manner. In orthogonal arrays it is a function of 

the number of different parameters and the number of different levels that each parameter is allowed. The 

nuder of degrees of freedom for a system that obeys this criteria is given by 

where DF is the number of degrees of freedom, F is the number of different factors, V is the number of 

different values that each factor can have, and the "1 " accounts for the mean of all of the responses. 
Application of equation A.1 to our system of four different parameters with three levels for each yields 

nine degrees of freedom, nearly an order of magnitude fewer experiments than the tradition~al approach. 

In fact, the number of degrees of freedom of a Taguchi experimental system is closely related to the 

number of equations required to solve a set of linear equations containing N unknowns. 

Taguchi differentiates experimental factors into two categories: those that the experimenter can comrol md 

those that are beyond control. The first of these are known as parameters while the latter are known as 

noises. As discussed below, the parameters can be assigned several levels. The noises normally assume a 

random value governed by an appropriate distribution function. However, for experimental pueposes they 

are sometimes intentionally introduced to the system in a controlled manner as parameters. Using 

Taguchi's nomenclature, equation A. 1 can be rewritten as 

where P and L are the number of parameters and levels, respectively 

The similarity of the orthogonal array to a set of linear equations brings forth the first criteria for 

applicability which is: the effect on the response from each system parameter must be additive. Strictly 

speaking, this means that orthogonal arrays cannot be expected to produce perfect results when the 

parameters interact with one another. The problem with parameter interaction is that it produces a 

response that is not equivalent to the sum of the individual parameter influences. Typically, parmeters 

have small interactions which allow a nearly linear relationship between the responses of an individual 

parameter and the overall system. 

The non-additive interactions between parameters are classified as synergistic when the paralneters 

compliment each other to improve the response, and anti-synergistic when the parameters conflict with 

each other and diminish the response. It turns out that synergistic interactions present fewer problems 

than anti-synergistic interactions in the analysis. Unfortunately, the parameters in most systems interact to 

some extent and designed experiments will not yield perfectly conclusive results. However, for a vast 

majority of systems the interactions are not overwhelming. In these situations these arrays can be used to 

optimize the system, especially when measures are taken to minimize interactions between parameters. 

Orthogonal arrays are based upon the assignment of each of the parameters to one axis in an orthogonal ndimensional coordinate system. Everyone is familiar with orthogonal coordinate systems of 2 or 3 

dimensions, normally referred to as cartesian coordinate systems. Features of these lower dimensional 

systems can be generalized into higher order, n-dimensional versions. In these multidimensional 

coordinate systems, the system response to a given set of values of the parameters can be ploltted as a 

point in the n-dimensional space. It follows that each point in space corresponds to a given set of 

conditions of the n parameters and is in fact given by a unique combination of the parameters. 

A slight complication of designed experiments is that orthogonal arrays only exist for a select number of 

test conditions. This does tend to limit the usefulness of this method to particular parameter and level 

combinations. It is possible to use dummy arguments to supplement the parameters and/or levels present, 

thereby allowing arbitrary quantities of either to be examined. However, there are two disadvantages 

involved with the use of dummy arguments. The first is that more experiments must be performed ~lhan 

dictated by the degrees of freedom of the system. The extra experiments allow the array to remain 

orthogonal with balanced interactions among the parameters. The second is that the set of experiments 

may be more sensitive to the effects of some parameters than to others due to the arrangement of the 
dummy uguments. The number of parameters and levels included in some of the more comon 

oaogonal arrays are given in the table below. 

Table A.I Nomenclature of Orthogonal Arrays 

Combinations Required 

Parameters Levels Possible Ex~eriments 

From M.S. Phadke[ll 

The simplest odogonal array that results in fewer experiments than the full factorial approach is the L4 

which uses three parameters at two levels each. The LA array is shown in Table A.11 where each sf the 

three pxmeters are labeled A, B, and C. .It is also noted that in this table each parameter is set at two 

levels Babeled 1 or 2. This array will be used as an example to illustrate the various principles and 

calculations that are performed with designed experiments. 

Table A.II The L4 Orthogonal Array 

Parameters 

E3.P - A - B - C Response 

1 1 1 1 Y 1 

2 1 2 2 Y2 

3 2 1 2 Y3 

4 2 2 1 Y4 

The U asray employs four experiments to determine the levels of four unknowns. These unknowns are 

the overall mean level of the response and the effect of each of the three parameters on the response. The 

overall mean level of the response is simply the mean of the four different responses. 

Finding the effect of each parameter on the response is slightly more difficult. The effect of setting 

pxmeter A to level 1 is found by finding the mean of the response for all experiments where parameter 

,A was set to level 1 and subtracting the overall mean of the responses. In the L4 array parameter A is set 

to level 1 in experiments 1 and 2 so this effect is given by 
where a, is used to denote the effect of parameter A at level 1 on the response. The effect of parameter A 

at level 2 is found in a similar manner such that 

Using the same reasoning, the effects of the other parameters are found in a similar fashion. For 

example, the effect for b, would require the responses generated by the first and third experiments. This 

process can be extended to larger arrays. Equation A.6 shows this relationship in its general form. The 

effect of any particular parameter level is found by subtracting the overall mean from the mean of the 

responses where the parameter of interest has that desired level. In this equation the effect of parameter Q 

at level m is desired, and there are n experiments where parameter Q was set to level m. 

Examination of equations A.4 and A.5 reveals that a, = - a,. In fact one of the results of the 

orthogonality of the arrays is that the sum of the effects of different levels for each parameter must equal 

zero regardless of the number of levels involved such that 

As part of this type of experimentation it is frequently necessary or desirable to conduct more than one 

test per condition. Conducting multiple tests, known as experimental replications, insures that the 

statistical variability of the testing process is reduced. It also insures that the result of the experiment is 

repeatable. If the response for a given condition has a high degree of variability this usually means that 

the response is susceptible to outside factors. These factors are referred to as noises in the system. 

Reducing the level of noise is almost always beneficial for the process. In manufacturing situations, it 

may be more desirable to reduce the noise in the system than to achieve the absolute optimal response. 

An additional concern is that systematic errors may occur that can distort the results. The most common 

type of systematic error is for one of the measuring systems, such as a thermocouple, to drift resulting in 

recording different values for the same phenomena. The normal solution to this problem is randomization 

of the experimental process so that the drift does not affect one parameter more than another. Another 

common solution is to periodically run a calibration experiment to check for drift. Phadke['] states that 

systematic errors are normally not as large a problem as simple set up errors, particularly with the small 

number of experiments required in a Taguchi style experiment. As such he recommends that the 

experiments be run in order and that the most difficult parameters to change be placed on the left hand 

side of the array (parameter A & B). This is because the left hand parameters in most orthogonal arrays 

will have to be changed less frequently during the course of experimentation than the others. If this 

technique is employed, it is a good idea to run calibration experiments to check for systematic errors, 
pafliculxly if the experimental process is long and drawn out. A commor. technique is to rerun the first 

experiment after the end of the main experimental process. 

Signal-to Noise Ratios 

The signal-to-noise ratio, SIN, is frequently used to combine optimization of the response with reduction 

of the vxiabiliity due to noise. The term SIN originated in the area of electronic circuit design where it 

was desirable to maximize the output of an amplifier for a given power input while minimizing the mount 

of noise introdiuced into the signal. It is obvious that the optimal result is an infinite SIN due to a 

combination of' the output going towards infinity and the noises going to zero. A further result of the 

electronic origin of the SIN is that the values are normally converted to decibels, dB 

SIN = 181og (signal-to-noise $nction) A. 8 

where the exact form of the signal-to-noise@nction depends upon both the nature of the response to be 

optimized and the nature of the noises. An additional advantage of this formulation is that values for the 

extreme cases are converted to more manageable numbers. Signal-to-noise ratios approaching infinity (a 

good system) yield much smaller, more tightly grouped numbers using this transformation while in very 

noisy systems (SIN * O), the transformation results in more widely spread numbers. 

The signal-to-noisefinction for any given set of replicated measurements can be evaluated in the general 

sense as a coartbination of two factors: mean value of a desired response and variability about that mean. 

These factors are accounted for in the relationship 

where p is the mean value of the response and a is the standard deviation of the response for the 

populafon. lit is readily seen that larger values of the mean or smaller values of the standard deviation 

will result in 21 larger SIN. This is a typical case of more-is-better where the desire is to maximize the 

response of the system while minimizing the noise. 

The signal-to-noise evaluation is designed so that it is always desirable to get the most positive value. 

'This makes practical sense if the response is viewed from the standpoint of a ratio of desired output to 

undesirable signal randomness. For this reason it is sometimes necessary to modify the formulation of the 

signal-to-noise function or the logarithmic transformation from the most obvious form. 

Taguchi introduced the concept of a parabolic loss function which is closely related to the signal-to-noise 

ratio in that it states that a part or process that is not right on target leads to an additional, avoidable cost. 

This Taguchi loss function, L(y), for a given part or process step is 

where y is the measured response, T is the target value, k is the cost of deviation from the target. 
Modification of the Taguchi loss function to account for an entire experimental run or a production run 

yields 

where 17 is the loss function for a series of identical experiments, a: is the population vxiance, and gn, is 

the population mean for the responses. The population mean and variance, p, and a;, are normally 

approximated by the mean and variance for a sample of the population, y and s;. The lioss due to either 

producing parts that are off target (T-y) or with variability a; is easily seen and quantified using this 

equation. In addition, the Taguchi loss function is normally easier to compute and assig~ls a cost to having 

a process off target that is easier for management to understand than the signal-to-noise ratio. 

Optimization Formulas 

The most commonly desired form of optimization is when a particular target value of the response is 

desired which is known as nominal-is-better (NB). An example of this would be the ~ickness of a 

coating. There is normally some parameter, such as coating time, that can be adjusted to force the mean 

to the target value while only scaling the variance by a similar amount. If the mean must be scaled by a 

factor a, ie. T = ah, manipulation of equation A. 11 allows the following simplifications when the second 

and larger order terms are eliminated 

where is the mean response of the experimental runs and s: is the sample variance of the series. 

In other processes the smallest response is desired, known as less-is-better (LB). An example of a less-isbetter process is the number of defects in a coating operation such as painting. In this case, the Taguchi 

loss function or practical signal-to-noise function in dB is 

where the sample size is n and the negative sign is used so that a larger value of 7 is always better 

In producing a wire it may be desirable to maximize the tensile strength so more-is-better (MB) is the 

desired response. This yields 

where the reciprocal of the response is used to avoid maximizing the variance as well as the mean. 

Responses from the signal-to-noise method are evaluated in the same manner as that of the simple mem. 

Equations A.3 through A.7 are just as valid for the signal-to-noise principle as they are for responses 
developed using a statistical average. The y values are now assumed to be generated by the appropriate 

equations for 7 listed above and are assumed to be in decibels rather than having the same dimensions or 

units of the physical properties they evaluate. Taguchi's signal-to-noise ratio has the added feature of 

evaluating consistency among a series of replications as well as how close the system output is to the 

desired output. Simply put, the signal-to-noise method requires both optimum magnitude (high, low, or 

nominal) md consistent results to yield the best response. As a result it is strongly recommended that one 

of the varimts of Taguchi's signal-to-noise ratio be used to optimize the system rather than only the 

response. The disadvantage of having to perform each experiment more than once is more than 

compensated for by the knowledge gained about the quality of the response. 

Compuhtional Procedure 

Once the overall mean for all the responses and the effects of each parameter have been calculated the 

system can be optimized to predict which level of each parameter will give the best result. The general 

equation for the: model used to evaluate a predicted response has the form 

yPed = + C para. efi + C interahon e8 + error 

The terms on the right side of this equation,are, from left to right, the overall mean, the summation of all 

of the parmeter effects, the summation of any interaction effects between the parameters, and any 

statistical error anributed to differences in the measured response between the statistical sample and its 

population. 

Parameter interactions are present when two or more parameters interact to cause a different net effect 

ahm if both pameter effects were evaluated as separate entities and then summed together. Much of the 

time interactions are regarded as an undesirable part of experimental testing, especially in partial factorial 

experirnentation.This is because it is difficult for them to be properly identified without conducting an 

additional series of designed experiments or several different confirming experiments. A common 

example of a p,arameter interaction is when two reactive chemicals are introduced as parameters in a 

production process. If the chemicals were to be evaluated onan individual basis, one chemical without the 

other, the response could be radically different than if both were evaluated together. 

Error invades experimentation from numerous sources that are either in or out of the experimenter's 

control. One source of error stems from inaccuracies in the measurement of some physical quantity. 

Error like this might be based on inconsistency of testing done by the experimenter(s) or using poorly 

calibrated measuring equipment. With careful control of the process and the related measurement 

melihods, this type of error may be significantly reduced, if not eliminated. A source of error less easily 

ecanhro~led may result from the random behavior of a tested material based on its flaws or microstructural 

difkrences. 

Because the method used in this experiment is not designed to account for such things as interactive 

parmeters or statistical error, those respective terms in equation A.15 are not taken into account. This 

results in a equation for the predicted response being 

Ypred = Y + C para. efi 
For a three parameter system the predicted response can be expressed as 

where the last three terms in this equation represent the desired effects of these parameterz;. For instmce, 

if the largest possible mean response is desired, the predicted response is found by taking the most 

positive level for each parameter and adding this to the mean. If the smallest possible mean response is 

desired, the predicted response is found by taking the most negative level of each parameter and adding 

it to the mean. For the Taguchi signal-to-noise response the most positive parameter effects are 

always desired to optimize conditions. If the experiment defined by the predicted parameter levels has not 

already been conducted, it is then necessary to conduct this experiment to confirm that this is indeed the 

largest response. If the prediction and the confirming experiment do not agree, there is a strong indication 

that the parameters interact and that Taguchi's method may not give accurate results. ho&er 

complication that can arise is that several conditions may generate similar predictions, which is more 

common in higher order arrays. In both cases it will be necessary to conduct more than one confirming 

experiment utilizing the best few sets of levels to determine which results in the one optimal response. 

Often times it is convenient to show the relative effect for each parameter by means of a line chart. These 

charts graphically represent the relationship each parameter level has on the response. Typically two 

things are inferred by these types of graphs: the relative magnitude of effects between parameters ;and the 

trend of effects for the various levels within any given parameter. Both pieces of informat:ion can be 

extremely useful for optimization purposes. 

Another way of demonstrating the relative effect each parameter setting has on the response is the use of a 

Pareto diagram. This diagram is a simple bar graph that arranges categories of influence in descending 

order. The specific categories considered in this chart depend on the situation analyzed. The intent of 

these charts is to graphically demonstrate how some parameters have significant influences on the results, 

while others are relatively insignificant. In a majority of designed experiments the numbel- of pameters 

having a major role in the outcome is considerably smaller than the others. This is referred to in quality 

engineering circles as separating the vital few from the trivial many. For experiments conducted in the 

laboratory the objective of using Pareto diagrams is to compare and contrast the optimum of parmeter 

levels affecting the response(s). 

Two examples follow showing how this data reduction process is carried out. The first example is a 

system that includes three parameters at two levels each to demonstrate the fundamental principles of this 

experimental process. A designed experiment of this size is listed in Table A.1 as the L4 ofiogonal 

array. The second example involves an L9 orthogonal array with four parameters at three levels each, to 

show how the technique can be extended to a more complicated system. 

Example 1 

The orthogonal array and the fictitious experimental results for this example are shown in Table A.III. 

Each experiment has been carried out repeatedly to improve the quality of the responses. These results 

are shown as the five test replications to the right of the test matrix. The mean response, q, and the 

variance (square of the standard deviation) for each experimental condition are then tabulated to the right 

of the raw data. This example assumes that the test objective is to minimize the response (LB). For 

example, the measured response might be the density of a manufactured part or experimental specimen. 
Table A.III Results from an L4 Designed Experiment 

Or~ogonal 

'Matrix Experimental Replications 

ExoLI El C 1 2345 Mean 22 

1 1 1 1 13.9 12,8 1<5 15.1 13.4 13.94 0.81 -22.90 

2 1 2 2 14.4 11.8 13.2 13.4 12.9 13.14 0.88 -22.39 

3 2 1 2 19.4 18.5 14.9 15.3 17.6 17.14 3.89 -24.73 

4 2 2 1 9.3 10.4 12.6 12.4 11.4 11.22 1.92 -21.05 

Overall Means 13.86 1.88 -22.77 

The Taguchi signal-to-noise ratio was calculated via equation A. 13. In this case all of the signal-to-noise 

values are negative so the largest and most desirable 7 is that which is least negative. The variance is 

provided as an indication of the combined noises within the system. A couple points of interest should be 

observed. First, based on the mean and the signal-to-noise responses, the fourth experimental condition is 

the best of the four test conditions. This suggests that the random noises of this experimental condition 

are low enough to give the lowest overall response even though they are not the lowest observed. Also, 

the sequence of experimental conditions, from best to worse, is the same for both methods. This is one 

indication that the experiment is probably "on track". If the two methods produced sequences that were 

drastically different there would be some reason for concern. 

The next step in this process is to find the effect each parameter has on the response. To do this the mean 

for all the individual responses corresponding to each particular parameter level must be calculated. The 

overall mean is then subtracted from each of these values as shown in equation A.6. For instance the first 

two experimental conditions both have parameter A set to level 1. By first finding the mean of these two 

responses and subtracting the overall response mean, the effect a, is found to be 

The value of a, is found by a corresponding computation where the levels of the A parameter are set to 

level 2. 

It should be noted that for a two level system the effect on the parameter of the first level is always the 

negative of the second. The effects of each level on each of the parameters for all three responses (mean, 

q, md variance) are calculated in a similar manner and are tabulated in Table A.IV. 

The system is optimized by selecting the parameter combination yielding a response that is closest to the 

desired. In this example the mean is to be minimized so the level of each parameter with the most 

negative effect is used to determine the optimal predicted mean. The best combination is when level 1 is 

used for parameters A and C and level 2 is used for parameter B. This combination is denoted as A,B,C, 

and yields a predicted response of 10.58 which is calculated as shown in equation A.17. Since this 

combination was not used as one of the original four experiments it is necessary to conduct a confirming 
Table A.IV Example L4 Array Parameter Effects on System Responses 

Parameter A Parameter B Parameter C 

Mean a, = -0.32 bl = 1.68 c, = -1.28 

a, = 0.32 b, = -1.68 c, = 1.2!8 

7 a, = 0.123 bl = -1.047 c, = 0.7'93 

a, = -0.123 b2 = 1.047 c2 = -0.793 

Variance a, = -1.04 b, = 0.47 cl = 0.85 

a, = 1.04 bz = -0.47 c, = -0.85 

experiment. An additional point is that parameter B had the greatest effect on the mean followed by C 

and A. 

A similar analysis can be conducted for the other two responses. The variance of the system will be 

minimized (less noisy) under condition AlB2& with an expected value of -0.48. This experiment Was 

conducted with a result of 0.88 indicating that there are either strong interactions between the pameters 

that affect the level of noise or large random noises entered the experiments. In addition, it is impossible 

for the variance to be less than zero. The signal to noise ratio is maximized for condition A,B2G, with a 

predicted value of -20.81. This is the same combination that was predicted to minimize the: mean, which 

is comforting. 

The relative effect of the different parameters on the responses can be shown by generating a Pareto 

diagram based on the reduced data. The relative effects are found by taking the difference between the 

maximum and minimum effect of each individual parameter. Table A.V gives the difference betvveen the 

maximum and minimum level for each parameter and the percentage that each parameter contributes 

toward the total effect. 

Table A.V Relative Parameter Effects for Example 1 

Mean Response Signal-to-Noise Noise 

a, - a, = 0.64 (9.8%) a, - a, = 0.246 (6.3%) a, - a, = 2.04 (43.6%) 

bl - b, = 3.36 (51.2%) bl - b2 = 2.094 (53.3%) bl - C, = 0.94 (20.1 %) 

C, - C, = 2.56 (39.0%) C, - C, = 1.586 (40.4%) c1 - C, = 1.70 (36.3%) 

The percents are plotted as a bar chart to create the Pareto diagram for the system. The Pareto diagram 

for this system is shown in Figure A.1. It is seen that significance of each parameter depends upon 

response considered. As stated above parameter B is the most important in determining the mean and 

signal-to-noise ratio while A is the most important in determining the noise. 

Example 2 

This example uses an L9 orthogonal array to explore the effect of four parameters at three levels on the 

measured response. Multiple test runs were conducted in this example but only the final response for each 

experimental condition is shown in Table A.VI. This example assumes that the response is some&ing 

which is to be maximized, such as strength. 
Mean Noise 

Measured Response 

Figure A.1 Pareto diagram of the responses of example 1. 

Table A.VI Results from an L9 Designed Experiment 

Parameter level combinations Mean 

Em - A - B - C - D Res~onse 

Overall Mean 575 

As in the previous example, the first step in this process is to find the effect that each parameter level has 

on the response. The first three experimental conditions were all conducted with parameter A set to 

level 1. The effect of level 1 on parameter A is found in the same way as in the previous example 

Corresponding computations are made for parameter A at levels 2 and 3 which are shown below. 
The effect of each of the different levels on each of the parameters is calculated in a similar manner and 

is tabulated in Table A.VII. 

Table A.VII Example L9 Array Parameter Effects on System Response 

Parameter A Parameter B Parameter C Parameter D 

The maximum predicted strength is found by using the maximum value of the effect for each of the four 

parameters. The combination of parameter levels that maximizes the response is A,B,C,D, ~vith a 

predicted value of 831.67. This condition is not one of the original nine combinations that were tested so 

a confirming experiment is required. The parameter that had the greatest bearing on the response was 

parameter D, followed by C, A, and B in descending order of importance. The effect that each pameter 

had upon the strength is shown in Figure A.2 as a line plot. 

Parameter A Parameter B Parameter C Parameter D 

Figure A.2 The parameter effects from example 2. 
Am additional observation is that some parameters have levels that are much more beneficial to the desired 

system response than others. The effects of parameters C and D show this behavior such that one of the 

levels is Barge and positive while the other two are moderate and negative. This type of behavior indicates 

&at the proper range of levels for these parameters was not chosen for the experiment to truly optimize 

alae performance of the system since all of the beneficial effects occurred for one of the levels. It is then 

necessary to conduct either the entire experiment or an experiment based upon another orthogonal array 

using new levels for these parameters. The next experiment should use a range of levels for the 

pxmeters 'hat had very skewed effects that explores the values of the levels around the optimum from 

the first experiment in more detail. 

The use of orthogonal arrays of designed experiments is a powerful tool for efficiently investigating the 

effect of a number of parameters on the response of a system. The method dramatically decreases the 

number of experiments that must be performed in comparison with the classical scientific experimental 

approach. However, there are a number of difficulties that can arise which limit the usefulness of the 

method. The biggest of these is that systems of orthogonal arrays rely on the response of the system 

being determined by addition of the individual effects of each parameter. Interaction of the parameters 

invalidates this assumption and means that the predicted response will not be accurate. If the interactions 

are weak (a common occurrence) this simply lowers the precision of the prediction. However, if the 

interactions are strong the entire system will be invalidated. As with all powerful analysis tools the 

engineer or scientist must apply a good deal of knowledge and common sense to design a set of 

experiments that attempts to minimize parameter interactions and use good judgement in interpreting the 

results. 
Appendix B Plaster Bats 

Plaster bats are frequently used to cast ceramic slurries because they are inexpensive, easily shaped, and 

reasonably efficient. Plaster is composed of fine needles of hydrated calcium sulfate (gypsurn) containing 

a continuous network of submicrometer pores. It is these pores that wick the water or other solvent out sf 

the ceramic slurry during slip casting. Unfortunately, these pores become clogged with fine cermic 

particles, salts, and organics from the slurry which necessitates periodic replacement of the bat. 

Plaster bats can be cast into nearly any shape in order to make a mold for slip casting a cermic slurry. 

We use flat bats with an impervious mold placed on its top surface to contain the slurry. The geometry is 

simpler to work with, and results in unidirectional casting and fewer voids and less residual stress in the 

green body. 

Procedure 

1. Coat the inside surfaces of the bat mold with a thin layer of petroleum jelly to prevent the plaster 

from sticking to the mold. We use a sheet of glass for the bottom of the mold and a 15 by 20 cnn 

wood rectangle 4 cm tall held together by nails for the sides of the mold. 

2. Separately measure 1 g of dry plaster-of-parishnd 0.61 ml of water (use a graduated cylinder and 

not a beaker) for each one cm3 of plaster to be cast. This allows for some waste and the water may 

need to be adjusted based upon the relative humidity (less in more humid climates than 

Albuquerque). 

3. Add the plaster to the water in a flexible bucket while stirring and breaking up the lumps. The best 

tool for stirring is your hand. The only drawback to this method is that the plaster can tend to dry 

the skin so application of hand lotion after washing is suggested. 

4. Pour the plaster slurry into the mold and vibrate to fill the corners of the mold and to bring the air 

bubbles to the surface. Wipe the excess plaster out of the bucket and allow the rest to harden. Bt 

can be broken away from the bucket followed by washing. Putting unhardened plaster down the 

drain is not recommended since it tends to set in the pipes. 

5. Level the top surface of plaster bat with a straightedge. We use a piece of aluminum sheet 5 by 25 

by 0.2 cm. 

6. When the bat has hardened enough to keep its shape (approximately 30 to 90 minutes) remove it 

from the mold. Then scrape the top and bottom surfaces smooth and flat using the straightedge ad 

gently bevel all of the corners to keep them from breaking off. 

7. Allow the bat to air dry for two to four days to remove most of the excess water. The rest of the 

water can be removed by drying in a low temperature oven (< 90°C). Do not heat the plaster bat 

above 100°C since this may result in partial dehydration of the plaster accompanied by cracking md 

sometimes explosive fracture. Plaster particles should be kept out of the ceramic body to avoid 

fracture of the ceramic body during firing. 

After use the plaster bat can be renewed by scrubbing the surface and redrying. If the surface becomes 

pitted, it is most easily flattened by soaking in water for a few minutes to soften it and scrapping with the 

straightedge. The bats will probably have to be retired after five to ten uses depending upon the hardness 

of the water and the dispersants used. 

"1 Pottery Plaster available from most ceramics supply companies. 

95 
IMPACT TESTING OF WELDED SAMPLES 

Calvin D. Lundeen 

University of the Pacific 

1502 Valencia Avenue 

Stockton, California 9521 1 

Telephone 209-946-215 1 
N92-30268 

IMPACT TESTING OF WELDED SAMPLES 

Calvin D. Lundeen 

University of the Pacific, Stockton, CA 

KEY WORDS: impact testing, arc welding, engineering, welding practice, 

weld quality. 

PREREQUISITE KNOWLEDGE: This laboratory is intended for engineering 

students with very little welding experience. Prior to attempting this 

laboratory the students should learn how to strike an arc and practice 

welding on a plate. 

To demonstrate how welding practice and joint design 

affect the performance of the joint. To demonstrate the importanlce of 

weld inspection to ensure quality welds. 

: 1) A Shielded Metal Arc Welder (SMA'W), 

which is capable of supplying at least 120 amps DC current; 2) a 

supply of E6010 electrodes; 3) a spot light; 4) a pendulum impact 

tester (Charpy type); 5) 1 cm (optional 3/8 in nominal) square, hot 

rolled 1020 steel; 4) cut-off saw; 6) grinder; 7) plate fixture 

constructed as per instructions in this write-up; 8) wire brush; 9) 

helmet with filter plate designed for SMAW welding; 10) gloves; 

11) protective clothing including apron, long pants, shirt, and closed 

toed shoes, preferably work boots. 

: During the experiment the students will practice welding 

bars together that will later be tested for impact strength. Begin by 

explaining the safety precautions necessary for shielded metal arc 

welding (SMAW). No more than two students should be in the 

designated welding area at a time. All should wear protective shields, 

clothing, as if they were welding. Illuminate the weld site with the 

spot light. Both students should watch the instructor demonstrate 

welding metal and finally the students should take turns welding samples 

together. 

Each student should prepare and test six samples with a welded length 

of 55 mm, and approximate cross-section of 1 cm square. One of the 

samples may be an uncut bar, as shown in the sample data. Each of the 

remaining samples should be prepared from two 28 mm lengths. The 
lengths should be sanded to remove any oxide coating . The students 

should prepare square, single-bevel, and double bevel groves in the 

samples. If the student has a solid bar control sample, only one square 

joint sample should be prepared. Otherwise two samples should be 

prepared of all samples. The square grove and uncut samples require no 

additional preparation before welding. Groves for good weld 

penetration should be ground or milled on a length in each of the 

samples. Figure 1 illustrates the different welds used. 

Square Weld 

Si ngl e-Bevel We1 d 

Double-Bevel We1 d 

Figure I. Welds tested for impact. The bevels should be at 

approximately 45" from the horizontal. The flat area should be 

approximately 2 mm. 

Once the samples are prepared, they are fitted into a clamping fixture 

shown in Figure 2. The purpose of the fixture is to space the bars at 

6 mrn (114 in ) intervals and to ensure that the gap between samples 

prior to welding is approximately 3 mm (118 in). At these intervals, a 

studenqt can move the stick from one joint to another without breaking 

the arc. Where the fixture touches the samples it should be aluminum 

to aid removal of heat and so that the samples will not bond to the 

fixture. Heavy gauge steel can be placed over the aluminum sides to 

protect them from inadvertent damage. When the samples are prepared, 

the samples are welded as described earlier. 
I 

Figure 2. Clamp fixture. This fixture will hold the bars at the 

appropriate spacing for welding. There are only two critical 

dimensions, the 6 mm spacing of the samples, and the 3 mm separation 

distance between each half. 

After all of the samples have been welded, they should be visually 

inspected. Because the welding will be of generally low quality, we 

will test welds that would normally be rejected. For this laboratory, a 

poor weld is a weld that does not fuse completely at one of the 

interfaces; a fair weld has large porosity but good interface with base 

metal; a moderate weld' has a good interface with the base metal and a 

small amount of porosity in the center of the weld. Good and excellent 

welds show no visible defects. Excellent welds have a uniform weld 

surface with little splatter. Once the samples have been welded, 

categorized by type and quality. They should be ground to 55 mm. 

Each of the samples should be tested in an impact test machine as 

would unnotched Charpy samples (ASTM Standard E 23). The weld is 

positioned so that the striking edge of the impact hammer is centered 

on the weld. For this laboratory experiment, the surface requirements given 

in the standard do not need to be met. 
SAMPLE DATA SHEETS: 

Sample :W Weld Quality Groove Type Impact Energy 

B Fair Square 30 J (22 ft Ib) 

A Poor Single Bevel 20 J (15 ft Ib) 

C Fair Single Bevel 45 J (33 ft Ib) 

E Moderate Double Bevel 83 J (61 ft Ib) 

D Poor Double Bevel 26 J (19 ft Ib) 

Solid Bar 332 J (245 ft Ib) 

INSTRUCTOR NOTES: When the data from several groups is combined, 

the benefits of bevelling, particularly double bevelling, become apparent. 

The differences in weld quality account for the differences in impact 

energies. The experiment can be repeated with heat treatment after 

welding to illustrate effects of heat treatment. This is best done after 

the students can weld at the moderate or good level as defined in the 

lab. The experiment has been designed so the materials are widely 

available. The experiment could be repeated using other 

material/'electrode combinations. This laboratory has been focused 

toward the engineer with limited welding experience. As a result, we 

have not found it necessary to clean and grind the samples just prior to 

testing . 

: American Society of Metals, 

Weldina Brazing. and Solderinq, Ninth Edition, 1978, p. 57, 60, 69, 76, 

85, 95. 

: The 1020 steel is available from any steel 

supplier. The aluminum for the plate fixture can be obtained from most 

metals suppliers or as scrap. E6010 electrodes for arc welding are 

available at any welding supplier. 
COMPOSITE COLUMN OF COMMON TER:IALS 

&chard J. Greet 

University of Southern Colorado 

2200 Bonforte Boulevard 

Pueblo, Colorado 81001 
Richard Greet 

University of Southern Colorado 

Pueblo, Colorado 81001 

KEY WORDS: composite, shear failure, buckling, hoop stress, 

exothermic reaction. 

PRERESUISITE KNBWLEDGE: This experiment can be used as a 

demonstration to students at the high school level or above. A 

knowledge of strength of materials principles is necessary to 

analyze the modes of failure observed. 

OBZECTIVES: To demonstrate that a composite column of familiar materials, namely aluminum soda-pop cans and Plaster of Paris, 

exhibits behavior different than the constituent parts tested 

separately. To observe failure in shear of a weak material loaded 

in compression, failure by buckling of a thin walled container, and 

failure by hoop stress rupture of the composite of both materials, 

EQUIPMENT AND SUPPLIES: 1) Aluminum soda-pop cans and 

Plaster of Paris; 2) Compression test machine, preferably with an 

X-Y plotter for recording force and deflection. 

SAMPLE PREPARATIONS: The tops of soda-pop cans are scored 

with a razor knife. After a few scorings, the circular top plate 

can be cleanly removed, leaving a wide-mouth container. 

Plaster of Paris is prepared by measuring two cups of powder 

into one cup of water for each can to be filled. This amount will 

more than fill a 12-92 soda-pop can. When the powder is first 

added to the liquid, the consistency of the mixture is thin. For 

reproducible results, it is recommended that more powder not be 

added, but rather that the mixture be stirred for 3-5 minutes until 

it thickens to the consistency of heavy cream. This mixture is 

then poured into a soda-pop can with the top removed. 

If students are preparing their own samples, they will note 

that after five to ten minutes, the filled cans are very warm to 

touch. This is a demonstration that Plaster of Paris, like 

concrete, does not set up by drying, but rather by an exothermic 

hydration reaction between the powder and the water. A total cure 

time of two or more days is recommended. 

After the Plaster of Paris has set, the top and bottom layers 

of the can are removed by cutting with a fine tooth blade on a 

radial arm or other shop saw that can produce cylinders approximately 90 mm (3-4 inches) in height, with flat, square4 off ends. 

The soft aluminum and Plaster of Paris can easily be cut with a 

wood working blade. It is especially necessary to remove the 

dished bottom of the can. Otherwise, the bottom region of the 

LUJ PR~~:CED!~;~,"G FAGS BL&.Tl:C :,tbi 
filled can will undergo local deformation before the bulk of the 

composite deforms. For some samples, a saw cut is made along the 

length of the can, and the aluminum skin is peeled off, leaving a 

Plaster of Paris cylinder. 

TESTING PROCEDURE: Three compression tests are run. A 

cylinder of Plaster of Paris is tested. An empty soda-pop can is 

tested, and a composite cylinder of Plaster of Paris surrounded by 

the aluminum soda-pop can skin is tested. For safety, tests are 

conducted with controlled strain-rate, rather than increasing load. 

Rates are slow, typically 0.1-0.2 mm (0.005 inch) per second to a 

total of 5-10 mm (0.2-0.3 inches) of compression. The test machine 

should be able to record forces to 20 kN (4500 lbf). 

TYPICAL RESULTS: The modes of failure are quite reproducible. 

Numerical values vary from sample to sample. 

Core Materiad Alone: A Plaster of Paris cylinder cast in a sodapop can will have a diameter of approximately 65 mm. This sample 

can be loaded to approximately 20 kN, deforming about 1% under this 

load, It then fails suddenly by cracking, with the load sharply 

decreasing in a controlled strain-rate test. Examination of the 

broken sample usually shows cone shaped end pieces, and several 

wedge shaped fracture pieces, indicating that the material failed 

on planes of maximum shear.. 

Empty Can Alone: An aluminum soda-pop can is approximately 0.1 mm 

in thickness. With slow constant strain-rate loading, it can be 

loaded up to about 1 kN (200 lbf), at which point it snaps into a 

complex Suckling mode of failure, with some regions of the surface 

buckling outward and some buckling inward. 

Core-Skin Composite: The maximum force that the composite c~lumn 

can maintain appears to be about the same as the core material 

alone, suggesting that the plaster is cracking inside the aluminum 

skin, However, unlike with the core material alone, the force does 

not decrease, Sut is maintained at a nearly constant value to 3-4% 

strain as the aluminum skin prevents the core from crumbling. With 

the plaster core, the skin can no longer buckle. Instead, at 3-4% 

strain, the skin catastrophically fails by a longitudinal rupture 

as the hoop stress builds up to exceed the skin tensile strength. 

At this point, the force on the composite drops to a very low 

value, 

INSTRUCTOR NBTES: The clearest results of these tests appear 

to be the visualization of the different modes of failure. Student 

interest can be enhanced by having them try to predict what will 

happen before the tests are done. While not readily compared to 

theoretical predictions, quantitative stress calculations do 

emphasize to students the need to work with stress rather than 

forces for making comparisons. The failure force for the plaster 

is approximately 20 times greater than that for the aluminum shell. 

However,, the area of the plaster is approximately 200 times greater 

than the aluminum, so that the aluminum is sustaining 10 times more 
stress just before buckling than the plaster is before it fails in 

shear. 

~ariaticns suggested for this experiment have included1 reinforcement with perhaps toothpicks, soda straws, string or other 

fibers. The behavior of steel soup cans might be compared with the 

aluminum cans used here. It has also been pointed out that for 

more consistent results, the curing of the plaster--tempera.ture 

profile and final density--should be documented in more detail. 
Cu-Zn BINARY P SE DIAG 

DIFFUSION COUPLES 

Robert A. McCoy 

Materials Engineering Department 

Youngstown State University 

Youngstown, Ohio 44555 

Telephone 216-742- 1736 

$RECEDEF!G PAGE B%RN;I: NO"B'$iif,p9q9.$Q 

109 
Cu-Zn BINARY PHASE DIAGRAM AND DIFFUSION COUPLES 

Robert A. McCoy, Professor 

Materials Engineering 

Youngstown State University 

Youngstown, Ohio 44555 

KEY WORDS: Phase diagram, diffusion, diffusion couple, diffusion rate. 

PREREQUISITE KNOWLEDGE: This experiment could be performed by students 

taking an introductory-level materials science course. 

OBJECTIVES: 

1. To learn what information a binary phase diagram can yield. 

2. To learn how to construct and heat treat a simple diffusion 

couple. 

3. To learn how to prepare a metallographic sample. 

4. To learn how to operate a metallograph. 

5. To learn how to correlate phases found in the diffusion couple 

with phases predicted by the phase diagram. 

6. To learn how diffusion couples held at various temperatures could 

be used to construct a phase diagram. 

7. To learn the relation between the thickness of an intermetallic 

phase layer and the diffusion time. 

8. To learn the effect of one species of atoms diffusing faster than 

another species in a diffusion couple. 

EQUIPMENT AND SUPPLIES: 

1. Three copper rods (99.9+% purity), about 1.27 cm (0.5 inch) in 

diameter and 4 to 5 cm in length. 

About 4009 of mossy zinc (99+% purity). 

Three Pyrex test tubes, about 2.5 cm in diameter and 20 cm in 

length. 

One stainless steel test tube holder. 

One ceramic crucible, at least 200 ml capacity. 

Appropriate safety equipment such as a face shield, heat-resistant 

gloves, and tongs to handle the crucible and test tubes containing 

600°C molten zinc. 

One furnace capable of maintaining 600°C and with a chamber at 

least 21 cm tall. 

Standard metallographic sample preparation equipment. 

Etchant consisting of 20 ml NHqOH, 40 ml water, and 5 ml Hz02 

(3%). 

10. iight metallograph with a Polaroid camera attached. 

PRECEDING PAGE B\fPK PJOT FlLMBD 
PROCEDURE: 

1. Weigh out 4009 of mossy zinc and place it in the ceramic crucible.* 

2. Place the crucible in a 600°C furnance and hold for about a halfhour until all the zinc is molten. 

3. Clean the surfaces of the three copper rods using 120 grit paper. 

4. Center one copper rod in the bottom of each test tube. 

5. Place the test tube holder containing the three test tubes with 

the copper rods in the same furnace as the crucible for about 5 

minutes to preheat the copper and to ensure the dryness of the 

copper and the glass. 

6. Carefully remove both the crucible and the test tube rack from the 

furnace using the appropriate gloves, face shield, and tongs. 

Reset the furnace to 400°C. 

7. Quickly skim aside the oxide residue floating on the molten zinc 

and pour the zinc in equal proportions into each test tube to 

about 6 cm of height, completely covering the copper rods with 

molten Zn. 

8. Immediately return the test tube rack containing the samples to 

the furnace (now set at 400°C). 

9. After holding at 400°C for 1 day, 4 days, and 9 days respectively, 

remove each sample from the furnace and quench in water. Be careful as the glass tube will crack as it is quenching. 

10. Engrave identifying codes on the top and bottom parts of each 

diffusion couple. 

1 Using a cutoff wheel or saw, cut transversely each diffusion 

couple in half. 

12, Prepare metallographically the cut surface of one of the two 

halves of each diffusion couple, starting with 120-grit paper and 

working progressively through a 1-vm abrasive polish. 

13. Etch the polished surfaces using the etchant described in the 

previous section. When mixing and applying the etchant, use 

gloves and eye protection. It will take only a few seconds of 

swabbing this etchant on the sample to etch it, as seen by the 

zinc portion of the diffusion couple turning a gray color. 

14. View each sample under the light metallograph at magnifications 

varying from 50x to 500x. Find regions where there are no gaps 

between the Zn jacket and the Cu core. Identify the 6, y, and E 

phase layers in each of the three diffusion couples and take 

Polaroid photos at 50x similar to those shown in Figure 1. 

15. In order to more easily measure the width of the relatively 

narrow 6-layer, additional photos at 500x should be taken of each 

of the diffusion couples (see Figure 2). 

16. From the photos, measure the average width of B and Y layers for 

each diffusion couple as shown in Table 1. Find a simple mathematical relationship between the layer width versus the diffusion 

time for both the 6 and Y layers. 

17. Observe the location of the phase layers relative to the original 

Cu-Zn interface. 

18. Observe the location of holes or voids in the microstructure of 

the diffusion couples. 

*' Add flux if desired. 
SAMPLE DATA SHEETS: 

TABLE 1. INTERMETALLIC PHASE LAYER WIDTHS 

Time player width (mm) Ratio of P-layer Y-layer width (mm) Ratio of Y-layer 

(days) (from photos at width to width (from photos at width to width 

500x ) at 1 day 50x ) at 1 day 

INSTRUCTOR NOTES: The instructor should provide each student with a 

copy of the Cu-Zn phase diagram. Across the phase diagram at 40O0C, the 

student should draw a horizontal line (as shown in Figure 3) to determine the 

chemical composition (wt. % Zn) of each phase at the various phase interfaces. 

These chemical compositions indicate the solubility limits of Zn in each 

phase. Emphasize that the layers of intermetallic phases seen in the 

diffusion couples should have composition ranges predicted by the phase 

diagram at 400°C and not at room temperature since the water quench locks in 

the 400°C microstructure. Figure 3 is also useful to explain how diffusion 

couple experiments could be used to construct a phase diagram. Several 

diffusion couples of the same two metals could be held at different 

temperatures for a period of time, quenched, and then analyzed as to the 

chemical composition of the phases at the layer interfaces. After collecting 

the solubility limits of the phases at the different temperatures, the phase 

diagram could be constructed. 

An approximate composition profile of the diffusion couple, as shown in 

Figure 4, is easy to construct from the information obtained from Figure 3 if 

one assumes that the chemical composition varies linearly as one moves across 

each single phase region. Together, Figures 3 and 4 are helpful in explaining 

why the chemical composition changes abruptly across each phase interface as 

well as why there are no regions consisting of a mixture of two phases in the 

diffusion couple even though such regions appear to exist in the phase 

diagram. 

Depending upon the student level, the instructor could explain how Fickus 

Second Law of Diffusion predicts that the width of each phase layer varies 

with the square root of the diffusion time when the diffusion temperature is 

held constant. This relationship is easy for the student to deduce when using 

the diffusion times of 1 day, 4 days, and 9 days since the relative thickness 

of a particular layer is found to be approximately in a simple 1:2:3 ratio as 

shown in Table 1. 
The student should be informed that the Zn atom diffuses much faster than 

the Cu atom. This fact can be used to explain why the intermetallic phases 

all form on the Cu side of the original Cu-Zn interface. It also can explain 

the formation of voids in the Y and E phases since the Zn atoms are moving in 

toward the center of the couple faster than Cu atoms are moving out toward the 

Zn jacket. This phenomenon is called the Kirkendall effect. 

One of many applications of the principles learned from this experiment 

involves the manufacturing process to form wire of the superconductor Nb3Sn 

(see page 604 of reference 1). In this process, a composite consisting of 

niobium ,wire imbedded in a copper matrix is plated with tin. When heated, the 

tin diffuses through the copper and reacts with the niobium to produce the 

Nb3Sn superconductor in the form of wire. 

Another application of diffusion principles involves the carburizing of 

steel to form a hard, high-carbon case around a softer, low-carbon core (see 

pages 386-387 of reference 2). If the amount of carbon present at the surface 

of the steel and the carburizing temperature are both held constant, then the 

depth of the resulting hardened case is found to vary as the square root of 

the carburizing time. 

Still another application is the explanation of a premature failure of 

integrated circuits called the "purple plague" (see page 133 of reference 2). 

It is called the "purple plague" because of the surface discoloration that 

accompanies the failure. This failure occurs at the interface where gold wire 

leads are welded to aluminum terminals of the integrated circuit. During the 

operation of the integrated circuit, the A1 atoms diffuse faster across the 

interface than the Au atoms. The resulting formation of voids at this 

interface due to the Kirkendall effect can eventually cause the electrical 

connection t o f a i l . 

REFERENCES: 

1. D.R. Askeland, The Science and Engineering of Materials, 2nd 

Edition, PWS-Kent Publishing Co., 1989, pp. 131-133, 385-387, 604. 

2. F,N. Rhines, Phase Diagrams in Metallurgy, McGraw-Hill Book Co., 

1956, pp. 107-109. 

SOURCE OF SUPPLIES: 

The mossy zinc can be readily obtained from most any chemical supply 

company for less than $25 for a 1-kg jar. To buy the copper rod, contact 

your local metal supply house. A standard mill-size rod 12 feet long and 

11'2-inch diameter of 99.9+% copper should cost about $50. 
Figure 1. Single-phase layers in the Cu-Zn diffusion couples held at 400° C 

for (a) 1 day, (b) 4 days, (c) 9 days. Mag. 50x. 

ORiGBNAL PAGE 

BLACK AND WHITE PHOTOGRAP
Figure 2. Growth of the p-layer in the Cu-Zn diffusion couples held at 

40Q0 C for (a) 1 days, (b) 4 days, (c) 9 days. Mag. 500x. 

116 
Figure 3. Correlation between the Cu-Zn phase diagram showing 

equilibrium phases at 400° C and the single-phase layers 

formed in the Cu-Zn diffusion held at 400° C for 9 days. 

Adapted from page 108 of reference 1. 
Figure 4. Composition profile of the Cu-Zn diffusion 

couple held at 400~~ for 9 days. 
DESIGNING, ENGINEERING, AND TESTING 

WOOD STRUCTU 

Thomas M. Gorman 

Department of Forest Products 

University of Idaho 

Moscow, Idaho 83843 

Telephone 208-885-7402 

DESIGNING, ENGINEERING, AND TESTING WOOD STRUCTUmS 

Thomas M. Gorman, Ph.D. 

University of Idaho, Moscow, ID 

KEY WORDS: wood, design, factor of safety, engineering economy, duration of load, 

stress, tension, compression, bending, deflection 

PREREOUISITE KNOWDGE: This material could be taught to a typical student of 

materials science, at the high school level or above. 

OBJECTIVES: To introduce basic structural engineering concepts in a clear, simple manner 

while actively involving students. This project emphasizes the fact that a good design uses materials 

efficiently . 

Q 

The test structure (Figure 1) can be easily assembled, has various design optiolns, and can be 

reused year after year. Even when the structure is loaded until it collapses, only one or two pieces 

usually break, leaving the remaining pieces intact and reusable. 

Groups of students are asked to use their intuition to choose different pieces with various 

cross-sectional areas for the structure, which will span a distance of 0.9 m (3 ft). Their goal is Its 

support at least 23 kg (50 lb) at a minimum cost. 

EOUIPMENT AND SUPPLIES: This list includes materials for three demonstration models 

plus enough material for three student groups to complete any design that they choose. 

Superstructure 

About 5.5 m (18 ft) of Southern Pine or Douglas-fir nominal 2 x 4 (38 x 89 mm). If another type 

of wood is used, you may have to adjust the target load value. The ideal structure should 

comfortably support the target load. Cut wood to sizes and drill the holes as indicated in Figure 2. 

Make pieces as clear (free of knots) and straight grained (grain parallel to length of piece) as 

possible. 

32 red pieces 

32 blue pieces 

32 green pieces 

60 yellow pieces 

Frame, supports and platform 

e Nine 19 mm x 51 mm x 305 mm (314 in x 2 in x 12 in) pieces of wood with slots as shown in 

Figure 5a 

Six 6.4 mm x 25.4 mm x 254 mm (114 in x 1 in x 10 in) pieces of wood 

Two 216 mm (8-1/2 in) pieces of nominal 2 x 4s (38 mm x 89 mm) with a 3.2 mmi (118 in) 

lengthwise groove. 

One 457 mm x 305 mm x 19 mm (18 in x 12 in x 3/4 in) piece of plywood with holes drilled in 

each corner 

* Figures 1--8 are grouped according to experimental sequence. 

121 

PREd"EDiNG PAGE ELWNE"; a";QT Fjkpd~~ 
Hardw~re 

3.2 man $118 in) diameter threaded rod--total of 9 m (30 ft) cut to 305 mm (12 in) lengths 

* 60 wing nuts 

120 hex nuts 

120 washers 

Three nails, approximately 4 mm in diameter (10-penny) 

@ Agpmoximately 6 m (20 ft) of 1.0 mm diameter (18-gauge) copper or bronze wire 

10lheir 

* Spray paint or marking pens (four colors for marking wood) 

Nylon cord (4.6 m to 5.5 m (15-18 ft) length, 3.1 mm (118 in) diameter) 

* Carpet or pad to protect floor 

@ Weights (bricks or suitable dense objects of equal, known weight) 

Safety glasses for each student 

PROCEDURE: The structures to be built have interchangeable pieces of varying size and 

cost. There are four types of pieces of equal length with varying cross-sectional dimensions, 

referbed to in units. Each unit equals 1.6 mm (1116 in). Thus, a 114 in x 1 in piece is 4 x 16 units. 

Fictitious do:ilar values are assigned to each piece based on the amount of wood used and are color 

coded for easy identification (Figure 3). 

Before the actual classroom activity, prepare three models for demonstration, using the 

model in Figure 4. Make sure to place a washer between each wooden piece and the hex and wing 

nuts on the rods. Once the structure is assembled, attach wire supports diagonally to the wing nuts 

at each end of the rods as shown in Figure 4. These supports prevent the structure from collapsing 

sideways. 

The loading frame is necessary to prevent lateral buckling, or twisting, of the top pieces. 

The frame is designed to rest on the top pieces of wood that have been spaced 229 mm (9 in) apart 

by the hex nuts on the threaded rods. Make sure that this measurement is accurate. Three frames 

are needed with slots of different widths to match the three possible widths of the top cross pieces 

(see Figures 5a and 5b). The loading heads are made from nine 19 mm x 51 mm x 305 mm (314 in 

I( 2 in x 12 in) wood pieces with 1 inch slots cut as shown in Figure 5a. The braces are made from 

six 6.4 mrn x 25.4 x 254 mm (114 in x 1 in x 10 in) wood pieces. Three nails--approximately 4 

mm in diameter (10-penny)--serve as loading frame pins. 

The ""sugr economy" model is made with all yellow pieces (the weakest ones, 2 x 6 units) 

for a total cost of $14. The second model is made with all red pieces (the strongest ones, 4 x 16 

units); it loolts very sturdy, but its cost is a formidable $116. The third model (combination of 

blue, green, and yellow) costs $32 and is the most efficient design. This "ideal" model is kept out 

of view until all the students' structures are tested. It would be a good idea to pretest your ideal 

model to make sure that it supports the 23 kg (50 lb) load. If it doesn't, you could adjust the targetload value. 

Explain the challenge--to design and build an efficient structure capable of supporting 23 kg 

(50 Ib) at a nainimum cost. As an example, bring out the red structure (the strongest) and load it to 
46 kg (100 lb). No visible signs of stress on the structure will be evident. The students are told 

that the structures could be built without red pieces and still support 23 kg (50 lb), but they can use 

the red pieces if they'd like. You might want to put an upper limit on the total dollar cost for each 

structure to prevent students from being overly conservative in their design. 

The class is divided into groups, and each group receives a supply of lumber and materids. 

Students are encouraged to use their intuition and discuss their design within their group before 

proceeding to build it. They should take about 15 minutes to complete their design. After 

everyone has assembled their structures, begin testing (Figure 6). By adding loads in small, 4.5 kg 

(10 lb) increments, students can see problems developing before catastrophic failure. 

Add weights one at a time; be prepared for a sudden collapse of the structure. Green pieces 

(5 x 6 units), when used as top members, will break well below the target load. Blue pieces (2 x 116 

units), as side compression members, should break or show considerable buckling at the target load. 

Wear safety glasses. Make sure that the students also wear safety glasses and stay several feet away 

from the structure. Continue adding weight until the structure collapses or the optimal weight is 

reached. It will become obvious to the students that the way a piece performs dependls on where the 

piece is placed in the structure. Students will mentally revise their designs as they watch their 

structures contort and buckle under the heavy load. 

In some cases, the bowed structures actually hold the 23 kg (50 lb) load, but students will 

realize that they wouldn't want to be driving across a structure of that design! This illustrates the 

concept that maximum allowable deflection is sometimes the limiting factor in engineering design. 

Sometimes the structure will hold the load initially, but suddenly will come crashing down 

before the next weight is added. This unexpected phenomenon shows that the length of time a 

structure is loaded affects how it behaves. This illustrates the concept of duration of 1,oad. 

After each group's structure is tested, load the "super economy" yellow structure (2 x 6 unit 

pieces) which, when tested, doesn't support even a 4.5 kg (10 lb) load. Next, unveil the so-called 

"idea1"design and show that it will indeed support the 23 kg (50 lb) load, without shc~wing too 

many signs of impending failure. As a grand finale, load the red structure (the strongest). You can 

keep adding weight until the structure shows signs of stress, or for a dramatic effect, continue 

adding weight until it crashes to the floor as the load exceeds 69 kg (150 lb). 

On the blackboard, record the cost of each structure and the load it held before it collapsed. 

These test results give you the opportunity to compare the safety, cost, and design efficiency of each 

structure. The structures that support a higher load are the safest, while the ones that support at 

least 23 kg (50 lb) for the lowest cost are the most efficient. Occasionally, variability in wood 

performance shows up when similar designs perform differently. 

Another concept that may be discussed during this demonstration is the factor of safety. You 

may explain that the factor of safety chosen for a given situation depends on many variables, 

including the duration and frequency of the applied load, the variability in performance of the 

structure, and the consequences of a failure (would it be life threatening?). 
Both the size (cross-sectional area) and shape of a piece of wood affects its performance 

when it is subjected to stress. By designing wisely, you can use less wood and still have a strong, 

reliable structure. 

SAMPLE DATA SWEET: 

INSTRUCTOR NOTES: As a way to begin analyzing what happens to the structures, have 

the students pick up individual pieces and try to bend, compress, and pull them in tension with their 

hands. Because of their different dimensions, each piece responds differently to the forces. By 

comparing what happens to the individual pieces with the performance of the structures, the students 

can begin to identify forces causing the structures to deform. All pieces for this experiment are 

made from clear wood (free of knots or other defects) and are very strong in tension. A small 

cross-sectionail area can withstand very high loads. Try to pull apart a yellow piece (2 x 6 units) by 

pulling the ends away from one another. Next, try pushing in on the ends of the same yellow piece. 

When a piece is loaded in compression, it tends to buckle. The load at which it begins to buckle is 

controlled by the narrowest cross-sectional dimension. Compare the effects of compression on the 

blue (2 x 16 units) and green (5 x 6 units) pieces, which have nearly identical cross-sectional areas. 

The blue piece buckles more easily than the green piece because it has the narrowest critical 

dimension. In compression, then, a square cross-sectional area makes the most efficient use of 

material. 

Now compare bending the blue piece (2 x 16 units) in the two ways shown in Figure 7. The 

most imgorbint dimension of bending is depth. The deeper the piece, the stiffer it is and harder it is 

to bend, This is because stiffness is directly proportional to the cube of the depth and only linearly 

proportionall to the width. 

VJhen a student-built structure is supporting a load, the forces distributed to each piece 

depend on its location within the structure (Figure 8). As discussed at the beginning of the 

demonstration, red pieces are more than adequate (but not necessary) to support the maximum 

predetermined load. A discussion of engineering principles applied to wood design provides the 

clues students need to choose pieces adequate for building a structure that meets its design criteria 

with a minimum amount of wood (or cost). 
FOR FURTHER READING: Hoadley, R. B. 1980. Understanding Wood. The Taunton 

Press, Newtown, CT. 

McCarthy, M., and T. Gorman. 1990. Building excitement in the classroom. The Science 

Teacher 57(5):43-49. 

USDA Forest Service. 1987. Wood Handbook. USDA Agri. Handbk. 72 (rev.) &/ladison, WI. 

SOURCES OF SUPPLIES: All materials for this demonstration are commonly available in 

home centers, hardware stores, andlor building supply outlets. 

Figure 1. Assembled structure, resting on 

support blocks, with loading frame and 

wire cross bracing in place. (Photo 

courtesy of USDA Forest Products 

Laboratory) 

118 

(RED) 

25.4- 

t 

114 

(BLUE) 

0 

I 

D4 (GREEN) 

6 4mm(1/4") 3Zmm (1~") 79mm(5/16") 3 2mm(l/~"E 

Thick Thick Thick Thick 

Figure 2. The dimensions of the red, blue, 

green, and yellow sections of wood. 

(Drawing courtesy of USDAl d;orest 

Products Laboratory) 

RED BLUE GREEN YRLOW 

price/ 

piece g8 864 84 8 I 

UNITS 4x16 2x16 5 x6 2 x 6 

UNIT = 1.6mm ( 1/16 in) 

Figure 3. Cross-sectional view of the four 

types of pieces to be used in the 

structure. All are 508 mm (20 in) 

long. (Drawing courtesy of NSDA 

Forest Products Laboratory) 
wooden cross mete 

Figure 4. A schematic of the completed structure. The upper and lower comers have been enlarged 

to show their construction. (Drawing courtesy of The Science Teacher/May 1990) 
3 each 3 each 3each 

4 y4 mm( DEEP 

b229 mrn-4 b 229 md SLOT 

(9" 1 (9") 

6.4mm ( 1/4") wide slots 7.9rnrn (5/16") wid rlotr 3.2 rnm ( l/8") wide slots 

Figures 5a and 5b. The dimension of the loading heads for the loading frame are shown on the top. 

The assembly of the loading frame is shown below. (Drawing courtesy of USDA Forest 

Products Laboratory) 

Figure 6. Testing the structure. In the first photo, one group's structure is loaded as the rest of the 

class looks on. (Note that everyone is wearing safety glasses) Next, side sections begin to 

buckle just before structural collapse. The structure supported 32 kg (70 lb) before it gave 

way. (Photos courtesy of USDA Forest Products Laboratory) 

B?'+>',?" 

127 ~.Jp.t~;:!~,~& pfip .+arrE 

BLACK AND WHlTE FidijTOGRApW 
Figure 7. Bending a member in two different ways. The orientation with narrower depth is easier 

to bend. (Drarving counesy of USDA Forest Products Laboratory) 

Figuire 8. An exaggerated illustration of the structure shows how different members are 

subjected tc~ different types of forces. The compression sections become shorter, the tension 

sections become longer, and the zero force sections remain essentially the same. (Drawing counesy 

of USDA Forest Products Laboratory) 
COMPUTER VLSlION IN 

MIICROSTRUCTU L ANALHISIS 

Department of Mechanical Engineering 

Texas A&M University 

College Station, Texas 77843-3123 

Telephone 409-845-14 17 
COMPUTER VISION IN MICROSTRUCTURAL mALYSIS 

M.N. Srinivasan, W. Massarweh, C.L.Hough 

Department of Mechanical Engineering 

Texas A&M University, College Station, TX 

KEY WORDS: computer, microstructure, solidification, c:asting, 

aluminum, cooling rate. 

PREREOUISITE KNOWLEDGE: This material could be demonsticated to 

a high school level materials science student, but would be more 

useful to a student at the college freshman level or above. This 

experiment is intended to convey to the student that properties are 

a consequenceof the microstructure and,therefore, characterization 

of microstructure is very important. 

OBJECTIVES: To demonstrate that the microstructure of 

engineered materials is affected by the processing conditions in 

manufacture, and that it is possible to characterize the 

microstructure using image analysis with a computer. 

EOUIPMENT AND SUPPLIES: 1) Laboratory heating or melting 

furnace, 2) molding sand and mold boxes, 3) aluminum-7% silicon 

alloy ingot, 4) stepped bar pattern, 5) chromel-alumel ther~nocouple 

and indicator, 6) metallographic sample preparation facil.ity, 7) 

personal computer with accessories as detailed in the paper. 

PROCEDURE: The principle of computer vision will first be 

introduced followed by the description of the system developed at 

Texas A&M University. This in turn will be followed by the 

description of the experiment to obtain differences in 

microstructure and the characterization of the microstructure using 

computer vision. 

The phenomenal advances in the computer and microelectronics 

industry have made computer vision within the affordable range of 

budget strapped users. A decent system could be assembled fo:r under 

$10,000 and the prices are still falling. In this paper, we will 

introduce one such system and its application in microstructural 

analysis. 

The application of computer vision in microstructural arlalysis 

varies in degree of sophistication from simple determination of 

phase ratio, up to sophisticated grain size and morphology 

analysis. For the sake of simplicity, we will suffice with the 

introduction of phase ratio determination as a simple but effective 

method for introducing imaging analysis methods in material science 

laboratory education. 
The microcomputer image acquisition and analysis system used 

in this experiment consists of two main modules: the optical 

module, and the image and analysis module. 

Thle optical module consists of a Nikon MeasureScope 20 

microscope equipped with the proper optical elements and lighting 

fixture. The microscope was also fitted with a lightweight black 

and white CCD (coupled charged device) camera. Depending on the 

specimen to be studied, the proper magnification and lighting 

method could be determined by trial and error. 

The image acquisition and analysis module is based around a 10 

P/1Hz AT-compatible 286 microcomputer, 1 Mbyte random access memory, 

and 40 Mbyte harddisk. A color monitoris optional. The computer is 

equipped with a (PCVISION) frame grabber and image analysis board. 

This board is capable of storing 2 images with a 512x512 

resolution, in addition to the capability of on-board image 

manipulation. The captured and processed images are displayed on 

a B&W TV monitor connected to the image board. 

The control and analysis software runs under DOS (disk 

operating system) and is composed of two different components. 

First, a menu driven softwarecomponentisused to grab, filter,and 

perform some basic measurements on the images, and finally store 

them in the image data base. With the system also comes a 

subsoutine library containing functions that ease the manipulation 

of images. Using those subroutines, the user can construct 

functions tailored specifically for a particular application. 

A typical digital image is composed of a collection of image 

element-s, each known as a pixel, which represents the average light 

intensity over a discrete portion of the total image. Both spatial 

resolution and light intensity resolution of the image depend on 

the hardware used, but a 512x512 pixel image with 256 gray level 

represents an average reasonably priced system. 

Phase Determination Procedure: 

As a first step, a digitized image of the specimen in question 

needs to be acquired by the computer. This could be obtained 

direct1.y through the camera mounted on the microscope from a 

metallographically prepared specimen. If a direct image is not 

feasible, a digitized image could be obtained from a still 

photograph scanned through a digitizer. It is very important in 

both options to preserve the contrast between the different phases 

in question. Weak contrast between the different phases will 

increases the difficulty of subsequent phase discrimination steps. 

To obtain phase discrimination in the image, it is crucial to 

map each phase in a different gray level intensity zone. Under 

ideal conditions, and if the contrast in the original image is 

good, a simple transformation of the image to a binary black and 
white by simplethresholdingwill suffice,see Figure 1. Thresholding 

is a simple operation whereby pixels with a value above a preset 

threshold are assigned a binary value of 1 (or white). If a pixel's 

intensity value is below the threshold it is assigned a value of 0 

(or black), as shown in Figure 2. 

In many cases, the image quality is not superior, or contrast 

between the phases in weak. In such cases, a number of alternatives 

can be used to improve the quality of the picture. In conditions 

where the imagesare noisy, a number of filtering methods could be 

used to obtain a better separation between the phases in the image, 

Such filters include convolution operators like smoothing, 

sharpening, or averaging filters. Other filters include 

morphological filters like dilation and erosion operators. The 

majority of those filters are included as part of basic: image 

processing package. 

Even in cases where phase discrimination exists but with 

minimal difference in the intensity, area measurements beeom& 

sensitive to the choice of a cutoff threshold value. In such 

situationsa method called histogram stretching is used to t?nhamce 

the contrast as shown in Figure 1. 

In the case of a binary phase material where a threshslded 

binary image is obtained, phase fraction determination can be 

obtained by calculating the fractions of black and white areas, A 

simple program that tests the image pixel by pixel keeping account 

of pixel count, then calculating the fraction will perform this 

task. 

Experiment Example: 

An experiment to determine the effect of section thickness 

(cooling or solidification rate) on microstructure of Al-7%Si was 

performed by senior level undergraduate students at Texas A&M 

University. 

A stepped bar pattern was used to make a composite casting of 

different thicknesses. The cooling curve in each section of the 

stepped bar, as the casting solidified, was recorded using a 

chromel-alumel thermocouple connected to a digital temperature 

readout. In Figure 3 the cooling curves thus obtained are shown, 

Each section of the casting was then metallographically polished 

and etched to reveal the microstructure. The percentage of alpha 

phase in each section was then determined using the image analysis 

procedure described earlier and was plotted against the casting 

thickness, as shown in Figure 4. It is seen that the percentage 

alpha decreases with increase in section thickness (or decrease in 

cooling rate). This implies that the amount of eutectic (in the 

interdendritic regions of alpha) follows the reverse trend. Since 

the eutectic contains brittle beta phase, it follows that the 

strength of the aluminum-7% silicon casting decreases with increase 

in section thickness. In Figure 5 is shown a typical 
photomicrograph with alpha (white) and alpha plus beta (dark) 

phases. The percentage alpha measured by the lineal analysis method 

for this case was about 65%, which compares favorably with the 

value of 67.5 % shown in Figure 4. 

REFERENCE: Flemings, M.C., Solidification Processimq, McGrawWill, 1974, pp 134-172. 

SOURCES OF SUPPLIES: The casting materials, equipment and 

supplies can be obtained from companies listed in .the Thomas 

Register. The personal computer (PC-AT) can be purchased from any 

reliable source. For details of the image analysis system, please 

contact the authors. 

CONCLUDING REMARKS: The casting experiment has been chosen 

merely to demonstrate the need and capability to characzterize the 

microstructure. Image analysis can be useful for any engineered 

product, manufactured by processes like forging, rolling, welding, 

etc. 

ACKNOWLEDGEMENT: 

The experiments were performed by Brian Br~~hum, Brian 

Bidigare, Rafael Alvarez and Paul Bowers under the direction of the 

authors. The authors would like to thank these four former students 

for their dedicated work. 
Qurs 1 Image histogram stre 
Figure 2 Threshold selection in image histogram. 
Figure 3 Casting cooling curves 


EXPERIMENTS WITH THE LOW MELTING 

INDIUM-BISMUTH ALLOY SYSTEM 

Richard P. Krepski 

Interrnet Technology 

116 Long Road 

Georgetown, Pennsylvania 15043 

Telephone 412-573-7754 
Richard P. Krepski 

fntermet Technology, Georgetown. PA 

-andGeneva College, Seaver Falls, PA 

@ 1991 Iaterzet Technology 

KEY WOR3S: indium-bismuth alloy, phase diagram, izteraetalllc 

compounds, oxidation, solidification, casting, heavy netal 

toxicity, wetting behavior 

PREREQUISITE KMOWLEDGE: The primary audience for this 

material is the junior high school or middle school scle~ce studezt 

having no previous familiarity with the material, other thaz: some 

knowledge of temperature and the concepts of atoz, element, 

compounds, and chemical reactions. The unit can be adapted tc use 

at a more advanced level, as a means of exploring the %easing a'f 

the equilibrium phase diagram. 

OSJECTIVES: The alloy system indium-bismuth has several 

features that make it useful for participatory demonstrations at 

the pre-college level. Near the eutectic composition, the liquidns 

is well below the boiling point of water, allowlng simple, n:l~imal 

hazard casting experiments. Such phenomena as metal oxidati.~?, 

formation of intermetallic compound crystals, and aE unusual voluze 

increase during solidification could all be directly observed. 

A key concept for students to absorb is that properties of a.n alloy 

[melting point, mechanical behavior) nay aot correlate with sicple 

interpolation of properties of the pure components. Discussior of 

other low melting metals and alloys leads to consideration of 

environmental and toxicity issues, as well as providing some 

historical context. Wetting behavior can also be explored. 

EQUIPMENT AND SUPPLIES: I) Small pellets of pure Ixdlum azd 

bismuth, along with 100 gram samples of pre-alloy with 34 and 60 

wt.k Bi; 2) A hot plate or other modest heat source; 

Temperature measurement capability in the range 50 - 

preferably a thermocouple with digital readout; 4) Stainless steel 

cups; 5) Plastic spatula; 6) Glass Slide; 7) Plastic funnel; 8) 

Various clay media for mold making; 9) Eye protection for all 

students, and gloves for students involved with melting; 10) 

Mineral sample showing crystal facets. 

PROCEDURE: 

1. Have a volunteer inspect the sample of pure indium (very soft 

and ductile - can be dented by a fingernail). We will then 

* 

Development of this experlnent was supported by a grant arovided 

by the National Science Foundation Small Business Innovation 

Research Program. 
explore mechanical behavior of pure bismuth and the two alloys Sy 

I~nocking samples inside plastic bags on a table top. {First 

explain what is meant by weight percent azd "alloy".) Tke 50 wt.X 

bism~th alloy is very brittle and shatters like glass; the 34 wt.% 

bisxut!i alloy is very tough and is unaffected. The sure Sismuth Is 

hard and! brittle, but not to the extent of the bismuth-rick alloy. 

Caution: Pass these samples around inside slastic bags; small 

chips of fractured metal could otherwise get on students' 

fingers and get rubbed into eyes. 

Lead the students in a guided discussion of the possible 

reasons for these differences in mechanical behavior. Point out 

that the 60 wt. k bismuth alloy shows very flat surfaces where it 

breaks. This is a reflection of the crystal structure of the 

material - the way the atoms line up in orderly patterns when the 

zeta1 solidifies. This alloy is mostly an extremely brittle fnSi 

compound, and its fracture surface displays the planes of these 

crystals. Compare this to a highly "faceted" crystalline mi2eral 

like amethyst of fluorite. The other alloy is tough (difficult to 

crack) because it is a fine combination of two kinds of crystals - 

indium (with dissolved bismuth) and the falrly tough In 51 cmpound. 

Which alloy would the students choose tc make a part fr&? 

2. lrltroduce the periodic table and look up the crystal 

structures of indium and bAsmuth - no need to get into detail 

unless the kids ask. Also look up nelting points. Bismuth melts 0 at 271°C, Indium at 157 C.. .what temperature do they think the 

alloys will melt at? A logical gness would be to plot nelting 

temperature versus composition and just draw a straight line 

between the two endpoints. 

Melt the 60 wt. k bismuth alloy chunk in a stainless cup on a 

hotplate and measure temperature with thermccouple. It should go 

liquid at about 105~~. Why is melting point lower than for eltker 

pure material? Basically, the two different atoms have a hard time 

fitting together into a solid crystal structure. 

Caution: Do not let the metal temperature get too xuch above 

0 120 C, as this increases the burn hazard. All students should 

have protective eyewear. Students handling temperatcre 

measurement should wear gloves. 

While waiting for alloy to zelt: We have been using 

the word "metal". What are some metals in the room, and what makes 

a metal a metal? Students might say strength, or ability to bend 

like a wire, or shininess. Point out an electric wire and ask if 

there is metal in it and what it does. As another clue, discuss 

how a thermocouple measures temperature. When two different metal 

wires are joined together to make a circuit and the two junctions 

are at different temperatures, electrons will flow from one metal 

to the other - we can measure this effect, the magnitude of which 

depends on the temperature difference between the two junctions. 

This reinforces the notion of electrons freely flowing in a metal, 
because of the way the atoms are bonded together. This Is really 

what makes a zeta1 a metal. 

Students should be able to make five key observations as we 

melt and re-solidify the metal in the stainless steel cup: 

A. Cool the cup by imaersing it In water ... we should be able 

to see the expansion in the solid as it forms or, the ox:tsid?e 

of the cup. This is very unusual, and is due to the very =pen 

crystal structure. What other common material becomes less 

dense (expands) when it solidifies?? Eave a glass of Icewater 

available, to show solid ice floating ic liquid water. What 

would happen if ice was more dense than water? Ice in lakes 

and oceans would sink to the bottom and take a much longer 

time to melt in the spring - something to think about! 

B. On cooling, we will be able to see the higher melting 

crystals (InBi) forming first in the middle of the sample. 

When the alloy is partially solid, tip the cup to shift the 

liquid and expose the solid crystals. 

C. We should also note that the alloy is slushy over a range 

of temperatures - it doesn't just freeze at a single 

temperature like water or pure indiun or bismctk. This is 

typical of many alloys. 

D. When the alloy is molten we should be able to see an oxide 

skin forming on the melt snrface as it reacts with the 

air ... discuss how nature would like to co2vert this metal into 

an oxide, and how melting allows this to happec faster. Note 

also that a protective chromium oxide steel on the staxnless 

steel cup is actually what makes it "stair,less". The oxide 

film is so thin that we can't see it. If the steel surface Is 

scratched, chro~ium from the steel quickly reacts with the air 

to "heal" the protective film. 

E. Using the glass slide, we can demonstrate that the liqnid 

metal wets glass. This is unusual and relates to one 

practical use for indium-containing alloys - soldering of 

nonmetals. 

3. Second melting experiment with 34 wt. X bismuth: 3epeat tke 

procedure above. In this case, the alloy melts and resolidifies at 

a temperature of about i'zOc. This is the lowest melting 

composition. Note also that there is little or no range of 

slushiness - the alloy changes from solid to liquid and back again 

at constant temperature. Go back to our aap of melting point 

versus composition and plot the data we have generated for the two 

alloys. Is this what we expected? 

4. The fact that the 34 wt. % bismuth alloy melts below the 

boiling point of water enables us to perfora some simple casting 

experiments - we don't have to worry about boiling water when we 

cast into a wet medium like clay, and the low melting point in 
general reduces the hazard from molten aetal. Still, students and 

teachers need to have a healthy respect for the hot alloy, and wear 

eye and hand protection. To eliminate the risk of overheating the 

metal, it might be suitable to switch to a double Sciler 

configuration wlth the stainless steel cup sitting in a larger 

vessel of boiling water. 

This is a "guided discovery" sectlo- of the experixent, in 

which students should decide what approaches to take. Among the 

issues that should be addressed are: 

A. What pattern can be used for the castlng? A student's 

fingertip works well - the fingerprint can be precisely 

replicated because the alloy expands as it solidifies. 

3 B. What mold material works best and why? PlayDob or its 

equivalent forms nicely and does ~ot softe- or melt when in 

contact with the molten metal. 

C,. What is the effect of casting xetal temperature on casting 

quality? 

D, How can we avoid trapping air and the oxide that floats on 

top of the molten metal? The funnel can be used as a neans of 

feeding the melt into the aold. 

Students would probably like to keep these castings. However, 

the c~st of indium is on the order of $200/lS! There are Low 

melting alloys that are very inexpensive, bxt these contain toxic 

heavy metals like lead and cadmium. 

INSTRUCTOR NOTES: This experisent is ?art of a xore extensive 

program dealirg with low melting point metals. It is important to 

start the presentation with something physical that grabs the 

students' attention. In this case, an encapsulated nerccry globule 

is passed around. This is an object of fascination, acd one that 

not too many young students have seen because of mercury's 

environmental problems. The simple mercury toy provides a possible 

basis for discussion of surface tension and wetting behavior, past 

and present uses, and toxicity problems. After the casti-g 

e~rperlrnent, we pursue a sinilar theme talking about lead. One 

interesting approach is to state that every student has passed 

within a few feet of several pounds of lead that day - can they 

guess where it was? Surprisingly, even college students ca~'t 

identify the lead-acid car battery without a number of hints. 

Besides t~~ricity, another theme that links these aaterials together 

is wetting behavior and soldering. Mercury doesn't wet glass; lead 

alloy solders wet copper, but orly in conjunction with a flux; 

indium alloys wet just about anything. 

Note that this write-up contains a good deal of information 

that may not be used in a given presentation. It is important to 

go in the direction that student input leads, and to be flexible. 

Structuring the presentation as a lecture, especially at the 
beginning, will trigger a glazed-over ercpression on most faces. 15 

that happens, quickly shift to something more hands-on and 

interactive. 

The indium-bismuth experiment can be adapted for --- -=e at more 

advanced levels. In the college classroox, it can be used to 

reinforce the concept of phase diagrams. Crystal stru~+--~e L adiagrams or models and actual microstructures with microhardness 

indents can be used. For senior high school students, a 

challenging follow-up exercise would be to start with the measured 

weight percent compositions of tbe two lntermedlate compou~?_ds in 

the Indium-Bismuth system (64 and 48 weight !% bismuth), and develop 

the calculation to convert to atomic percents. We find the two 

compositions are exactly 50 at.%Bi and 33.3 at.XSi, corresponding 

to InBi and In 9i and suggesting that the two compounds for3 fairly 2 simple structures. This calculation requires concepts of atcmlc 

weight and Avogadro's number. To appreciate magnitudes, we can 

calculate the "gram-atomic weight" of 22 pound (10 Kg) bowling 

balls. If each bowling ball was an atom, a gram-atom of each 

would weigh the saxe as planet Earth - 6 x 20*' grams. In 

comparison, the weight of the same number of carbzn atoms Is 12 

grams! To promote student reading and considerations of ethics, 

have older students read Kurt Vonnegut's Cat's Cradle, in which a 

scientist develops a new crystal form of ice that melts at high 

temperature, with disastrous consequences! This is a nightmarish 

example of a scientist out of touch with the world and his 

professional responsibilities. Follow up with a class disccsslcn 

of these Issues. 

This experiment is also being adapted for in-service trainin 4 

of teachers, who are provided experimental materials to use in 

their classes. Secause of alloy cost, the unit is abridged to use 

only enough indium alloy to cast one student finger at a time. 

Melting is accomplished by the double-boiler approach to avoid the 

risk of overheating metal. 

Details of this full program and other materials science 

modules developed by Intermet Technology are provided in the 

project report to the National Science Foundation Small Business 

Innovation Research program. 

SOURCES OF SUPPLIES: Indium alloys were obtained from Indium 

Corp. of America. They are very expensive! A digital thermocouple 

is nice but not necessary - ours was obtained from Marlin 

Manufacturing in Pittsburgh for $120. Intermet Technology 

eventually plans to put together experimental packages and support 

literature for use in both teacher in-service and "scientist in the 

classroom" programs. 
A SENIOR MANUFACTURING LAB0 

FOR DETERMINING INJECTION MOLDING 

PROCESS CAPABIILITU 

Jerry L. Wichan 

David Plocinsk 

College of Applied Sciences and Technology 

Department of Industry and Technology 

Ball State University 

Muncie, Indiana 47306-0255 

Telephone 3 17-285-5641 
A Sedor Manufactuhg Laboratory 

For Determlnhg Injection Moldjing 

Process Capab*ty 

Jerry L. Wickrnan Ph.D. 

David Plocinski 

Department of Industry and Technology 

Ball State University 

KEY WORDS: process capability, quality 

control, statistical process control, 

parametric study, control charts. 

PREREQUISITE KNOWLEDGE: This 

subject material is directed at an upper 

level undergraduatelgraduate student in an 

Engineering or Engineering Technology 

program. It is assumed that the student has 

a thorough understanding of the process 

and quality control. The format of this 

laboratory does not follow that 

recommended because of the nature of 

process capability and that of the Sandretto 

injection molding equipment and tooling. 

This laboratory is instead developed to be 

used as a point of departure for determining process capability for any process 

in either a quality control laboratory or a 

manufacturing environment where control 

charts, process capability, and experimental or product design are considered 

important topics. 

OBJECTIVES: To demonstrate the typical 

procedure by which one can determine 

process capability. To demonstrate the 

development of control charts. To statistically show the areas through which 

processing variation can enter into the 

manufacturing process. 

EQUIPMENT AND SUPPLIES: A 

laboratory size injection molder (Sandretto, 

Spectrum 60) with an ASTM test bar 

fixture in place with associated machine 

instrumentation. Datflyte Model 862 with 

an associated statistics package for generating pareto analysis, control charts, 

process capability indices, and mmsuring 

equipment interfaced with an appropriate 

software package, Monsanto .ABS materids and a hopper dryer for matellds 

control. 

Introduction 

Spiring (1991) has indicated that 

interest in process capability is growing, 

due partly to the changing philosophy In 

quality control. Motivational f.ools such as 

slogans about doing things right the first 

time and building a better quality product 

are lost if there is little or no analytical 

study of the process and the product. 

World wide competition is forcing everyone (not just the U.S.) to look at how 

variation in the process and product can be 

reduced, and how all personnel from design through manufacturing can be involvd 

in the overall effort of reducing vanation. 

Process capability has lbeen defined 

as the range over which the output of a 

process varies or the actual process spread 

(6 a). Process capability ties both the 

product and process together. Process 

capability and the associated indices have 

the potential to positively impact product 

design, setting of tolerances or specifications, vendor quality surveys, communication with suppliers, machine allocation 

and others. Process capability makes it 

possible to quantify what the process is 
capal~le of doing, which determines if the 

product cars be made to current or revised, 

possibly tighter specifications. 

The %lollowing paper is divided into 

three subsections which lead to determining the process capability of the 

injection machine. It should be noted that 

dthough i~njection molding is a generic 

process, determining process capability 

from one !machine to the next may vary 

cowsiderabrly . 

Saindretts hjection PressIMaterials 

The machine utilized in the 

capability study was a Sandretto model 

Spectrum 60 screw injection molder 

capable of' a 3.17 ounce shot weight and 

66 ton clamp capacity. The Sandretto 

was a new purchase and is considered to 

be a state of the art machine. Principal 

operation is at a control panel where 

virtudliy dl processing characteristics are 

accessed a.nd manipulated via a 

microprocessor. Processing characteristics 

can lbe seen in either tabular or graphical 

formats, 

Injection molding is a process of 

molding solid plastic objects. It involves 

forcing molten plastic into a closed cooled 

mold where the plastic solidifies to a 

usable product upon closing. 

Pzrameters were set according to 

manufacturers' data sheets of the material 

(Morasanto Cycolac ABS grade 280) being 

used. These parameters included; drying 

time, drying teqerature, barrel temperature, nozzle temperature, injection speed, 

and screw plasticizing speed (RPM's). 

Control C:lhas(s 

To determine process capability it 

is assumed that a robust quality control 

program has been in place and is working. 

Control charts are being used and have 

been succlessful at removing most if not all 

assignable error. Juran (1980) states that a 

control chart is a graphic camparison of 

process performance data to computed 

"control limits" drawn as limit lines on the 

chart. The process performance data 

usually consist of rational subgroups 

sampled and plotted sequentially. Process 

variations are traceable to two kinds of 

causes: (1) random, i.e., due solely to 

chance; and (2) assignable, i.e., due to 

specific "findable" causes (Juran 1980). 

Only random causes of variation should 

exist because this represents the minimum 

amount of variation present (ff rt 3 a) in 

the process. The process is then said to be 

in a state of statistical process control. The 

actual process spread is 6 a which represents the width of the interval that contains 

99.73 % of the population. 

Different types of control charts 

exist for both attribute and variable 

process data. Bothe (1991) states that 

current accepted practices for determining 

process capability are defined for only 

variable data. This capability study used X 

and R charts before determining process 

capability. 

Process Gapalssty 

Many different indices exist for 

measuring process capability (Cp, Cr, 

Cpk). Bothe (1991) contends that this 

knowledge is extremely useful for shop 

personnel in determining what machines 

should be scheduled to run what parts and 

for monitoring process improvements by 

seeing these capability indices increase 

over time. Worthy (1991) indicates that 

the Japanese use process capability as a 

design tool to make sure that the intended 

design can be made to specifications. He 

also contends that in the U.S. we design 

the product without regard to whether or 

not manufacturing is capable of producing 

the part. 

Control charts use rational subgroups with upper and lower control limits 
calculated from the subgroups. Tolerances 

should not be used with control charts; 

tolerances are for individual items and are 

typically set independent of the process 

and may not relate well to process control 

chart averages. Process capability and the 

associated indices work with individual 

items and thus work well with tolerances. 

One of three situations exists relative to 

process capability and tolerances where 6 

a equals the process capability and U - L 

equals the difference between upper and 

lower tolerances. 

1. 6 a < U - L (Figure 1) This represents the most desired relationship. The 

process is in control and the tolerance is 

greater than the process capability. Even if 

there is a shift in the process average, no 

nonconforming products are likely to be 

produced since the parts may be considered out of control but conform to 

specified tolerances. 

2. 6 a = U - L (Figure 2) Process 

capability is equal to the tolerance. As 

long as this situation holds, no nonconforming product will be produced. As 

soon as the process shifts up or down, 

nonconforming product will be produced. 

Either processing variation must be 

reduced or tolerances must be increased. 

3. 6 a > TJ - L (Figure 3) This is the 

most undesirable of the three scenarios. 

Nonconforming product from both 

extremes of the normal distribution may 

occur. If a process shift occurs large 

quantities of nonconforming product may 

result (Besterfield 1990). 

Various capability indices exist, 

thereby inviting comparisons among processes with different quality variables and 

promoting similar inferences regardless of 

the product or quality characteristic 

measured (Spiring 199 1). 

Cp - Capability index. A minirrburn value 

of 1.33 is re~ognized as a defacto 

standard. 

Where: Cp = U - L/6 a 

If Cp = 1.00 then scenario $2 from 

above. 

If Cp > 1.00 then scenarao #1 from 

above. 

If Cp < 1.00 then scenario #3 from 

above. 

Cr - Capability ratio. The defacto smdxd 

for a Cr is 0.75. 

Where: Cr = 6 a/U - IL, 

Cpk - This is used to determine if the 

process is centered on the target or 

nominal value. A minimum value of 1.00 

is recommended. 

Where: Cpk = Z (Min)/3 

Z (U) = U - X/a 

Z (L) = X - L/a 

Rocess Capability 1Procedu~~e 

The Sandretto was progl-ammd to 

print out thirty different process parameters 

following each shot (Table 1). Each data 

sheet and corresponding part were label& 

to maintain traceability characteristics. 

Subsequent development of X and R 

control charts followed using select 

processing variables. 

The design of the process capability 

experiment included but was not limit& 

to: 

1. Selection of a suitable rr~olding 

tool. 

Will the product have subsquent 

use , i.e., materials characterization, 

etc. .? 

Would the tool be suibbble for 

control charts and process 

capability studies? (Figure 4) 

(ASTM D647-90). 

2. Design fixture for impact disc. 

Measuring tools available 
Data collection (DataMyte) 

Statistics and software used (SPCII) 

Traceability features 

Environmental soaking of fmture 

and related tooling 

Develop and build fixture. 

Develop Iskikawa diagrams of 

process.(Figures 5 & 6) 

A. Processing parameters. 

B. Machine components. 

C. Material handling. 

Selection of material. 

Determine Sandretto settings based 

on material selection and study. 

A. Barrel heats. 

B. Mold closing. 

C. Mold opening. 

D. Hydraulic ejection. 

E. Injection. 

F. Plasticizing. 

Determine if process is in control 

through the use of X and R 

charts. (Figure 7) 

A control chart distinguishes 

between random and assignable 

causes of variation through its 

choice of control limits. These are 

calculated from the laws of 

probability in such a way that 

highly improbable random 

variations are presumed to be due 

not to random causes, but to 

assignable causes (Juran 1980). If 

points on the graph exceed the 

established control limits, chances 

are that assignable causes entered 

the process and the process should 

be investigated. Injection molding 

Hydraulic Pressure points one and 

five are "out of control". These two 

points should be investigated. 

However the remaining points are 

within our control limits signifying 

that only random causes are present 

and the process should be left 

alone. Each point on a control chart 

represents a test of hypothesis, but 

the chart simplifies the calculations 

and presents a graphic method for 

doing hypothesis testing 

continuously (Juran 1980). 

8. Determine process capability for 

select processing characteristics. 

Conclusions 

This study was initially conceived 

in and intended to be used in an applied 

quality control class with an associated 

laboratory. Various aspects of this study 

have already been incorporated into the 

applied quality course and other "non 

quality control" classes. Determining 

process capability is an excellent tool for 

integrating undergraduatelgraduate students 

from electronics to manufacturing, 

inclusive of the design and mechanical 

options. The applied study reinforces those 

manufacturing concepts of the quality 

philosophy, metrology and statistics as 

discussed in the classroom. The impact of 

slight or even dramatic changes in 

personnel, machines, materials and 

methods can be graphically determined by 

using control chart theory and applications. 

The students need to be aware of this 

cause and effect taking place in virtually 

any manufacturing environment. Process 

capability encourages the synthesis of 

design of experiments, metrology, 

statistics, fnture design and use, materials 

characterization, bench marking, defect 

concentration analysis, sampling, and 

process variation to name a few. This 

study represents a benchmark for future 

studies scheduled at regular intervals to 

determine changes in processing 

parameters and subsequent changes to 

process capability. 

Recommendations 

Even though we have only begun 

this series of studies it is clear that process 
capability can be done on virtually any 

piece of industrial equipment available. 

The benefits far outweigh the time invested 

from both the students and faculty 

members standpoint. As with any scientific 

study my recommendations are: * Have a good understanding of 

statistical process control for all 

students and faculty involved. 

* Provide adequate time for 

development of study. 

* Select equipment with process 

capability in mind. 

Vonsider larger picture of process 

control with process capability 

being a smaller entity, i.e., spinoffs 

to other courses. 

* Additional work with identifying 

and reducing sources of variation. 

Personnel Machine 

Materials Methods * Incorporation of various types of 

measuring instruments. 

* Industry cooperation. 

References 

ASTM - D647, Design of Molds for Test 

Specimens of Plastic Molding Materials, 

1990 Annual Book of ASTM Standards, 

Philadelphia, PA. 

Besterfield, Dale H. Quality Control, 

Prentice Hall, Englewood Cliffs, NJ, 

1990. 

Bothe, Davis R. A Capability Study for 

an Entire Product. ASQC Annual Quality 

Proceedings. Milwaukee, WI. May 1991. 

Juran and Gryna, Quality Planning and 

Analysis, McGraw-Hill, Inc., NY, 1980. 

Spiring, Fred A. The Cpm Index, Quality 

Progress, February 199 1. 

Worthy, Ford S. Japan's Smart Secret 

Weapon, Fortune, August 12, 1991. 

L L 

Desirable Undesirable 

but No Wane 

FIGURE1.6o < U-L 
I 7 I/ L 

S.QliZSIM Out of cmm( 

and Wan# 

FIGURE 2. 6 0 = U - L 

L 

In Contml Out d Control 

and ware .nd wme 

FIGURE3.60 > U-L 

/-'---. 

\ / 

A 

37 

( 

FIGURE 4. ASTM Test Pitun 
FIGURE 6. Iskikawa Diagram of Processing Characteristics 

CYCLE DWELL -~ INJECTION VELOCITY ----- -- -- 

DOSE POSITION 

\ CHANGE OVER POS. 

OPENING PRESSURE CHANGE CONSENT 

STAGE Ill END POS STAGE I PRESSURE 

NOZZLE TEMP. STAGE II END POS. STAGE II PRESSURE 

ZONE D TEMP. STAGE I END POS. STAGE Ill PRESSURE 

ZONE C TEMP. INJECTION DELAY 

PLASTICIZING 

FINAL 

PRODUCT 

SCREW RPM'S 

BACK PRESSURE 
IBcRa)P I 2 I 4 5 6 7 8 0 

UCL llll 11111~ 111310: 11t3.I0? 111312 1113.12 1111lg 11. 111312 LC1 11014% 1101.4% 1101455 1101455 1101.455 1101.4% 1101.455 1101.4% 11131455 YVN 1118.2(a 11111403 1105.W 1105.m0 lPE*J.BU, llC6m) tlM.iW llOd.@YJ Ile7.W WWCf 1O.OW 15Cm 12.MO B.oLW 10.WO RINMR~~? m IES 8 OW 5 am 13.m 11.000 RS IES NO YES IES rtS IFS 

Uti 

2am 

15.(XW 

f tam5.D* 

FIGURE 7. x and R Chart of Sample Hydraulic Pressure Data 
LABOMTORY EXPERIMENTS FROM THE TOY 

Department of Manufacturing and Industrial Technology 

Arizona State University 

Tempe, Arizona 85287-6706 

Telephone 602-965-6584 

STORE 
LABORATORY EXPERIMENTS FROM THE TOY STORE 

by 

H.T. McClelland 

Department of Manufacturing and Industrial Technology 

Arizona State University 

Tempe, AZ 85287-6706 

KEY WORDS: Elasticity, plasticity, strain rate 

dependence, extrusion. 

PREREQUISITE KNOWLEDGE: This material could be taught 

to a typical student of materials science or manufacturing 

at the high school level or above. 

OBJECTIVES: To qualitatively demonstrate the concepts 

of elasticity, plasticity, and the strain rate and 

temperature dependence of the mechanical properties of 

engineering materials. 

To qualitatively demonstrate the basics of extrusion 

including material flow, strain rate dependence of defects, 

lubrication effects, and the making of hollow shapes by 

extrusion. The two parts may be two separate experiments 

done at different times when the respective subjects arle 

covered. 

To demonstrate the importance of qualitative 

observations and the amount of information which can be 

gathered without quantitative measurements. 

EQUIPMENT AND SUPPLIES: 1) One or more containers 

(eggs) of formable putty (Silly PuttyTM, Nutty PuttyTM, 

etc.); 2) one or more clay extrusion presses (made by PlayDohTM, Fun DoughTM, etc.) ; 3) ice and a bowl; and 4) a low 

power heat source (depending on the ambient temperature, 

this may not be required). 

PROCEDURE: Part 1 of this experiment involves allowing 

the students to manipulate the formable putty to illustrate 

the definitions and concepts of the mechanical properties of 

materials. Figure 1 contains a picture of the putty ant3 

normal packaging container. 

While the students are unwrapping the putty, the 

definitions of elasticity (recoverable deformation) and 

plasticity (non-recoverable deformation) can be reviewed. 

1) The students may form the putty into a smooth ball 

and bounce the ball on a rigid surface from a height of 

about 10 ern and note the general height of the rebound and 

the lack of permanent deformation. The amount of 

deformation can be quantified by using a measuring stick. 
The ball may then be placed in the bowl of ice and 

cooled. It will be noticed that the ball flattens on the 

bottom illustrating creep. 

After the putty is cold, it can be reformed into a ball 

and bounced again from the same 10 cm height and the amount 

of rebound noted. The rebound height will be higher than 

when warm indicating an increase in hardness with decreasing 

temperature. 

2. The putty can then be formed into a cylinder. The 

students pull the putty slowly lengthwise and note the 

extensive plastic deformation (Figure 2). This is a graphic 

demonstration of the concept of ductility. A note should be 

made of the relative amount of force needed to pull the 

cy l iaader . Reforming the cylinder and quickly pulling it may 

result in some plastic deformation and a sharp break if the 

room temperature is below about 24 C (Figure 3). If it is 

sumer without good air conditioning, the faster pulling 

will still give extensive plastic deformation. 

Forming a cylinder and cooling it in the ice will give 

a better visualization. Slow pulling will give extensive 

plastic deformation (ductile) and fast pulling will result 

in a sharp break (brittle). The amount of force necessary 

to pull the cylinder should be greater than that needed for 

the \farmer conditions. 

The audience at the initial presentation of this paper 

suggested two other experiments along these lines. The 

first involved cooling the putty in liquid nitrogen and 

hitting it with a hammer when it was cold. The ball will 

shatter further illustrating the temperature dependence of 

deformation. The second suggestion was to also use torsion 

for the ductile-brittle versus rate of deformation 

experiment. This illustrates that the method of deformation 

does not change the material's reactions in these matters. 

3. A relatively short cylinder can be formed (height 

about twice the diameter). Placing the cylinder upright on 

a flat surface and gently deforming it in the length 

direction with the flat of the hand will illustrate the 

concept of barreling common in upset forging. The material 

next to the hand and next to the table will expand less than 

the center material due to the friction between the putty 

and hand and the putty and the table. 

4. The students should be given time to try other 

experiments with the putty. It has been observed that most 

students will play with the putty for quite awhile on their 

own. 

Part 2 of this experiment involves the use of a clay 

extrusion press such as the Play-~oh~~ Fun Factory or the 

Fun ~ough~~ Super Play Shop. As seen in Figure 4, the press 

comes with a variety of die shapes all of which have 
approximately the same cross-sectional area and thus the 

same extrusion ratio. The presses come with two containers 

of different color clay. 

1. The students may take one color of clay and extrude 

it through different die shapes noting the relative amount 

of force needed. In general, more force is required for 

those dies with the larger amounts of surface area (many small holes versus a few large holes). This indicates the 

effect of friction. 

2. The students should extrude clay using the tube die 

(bridge or spider die) and make hollow tubes (Figure 5). 

This is a concept which is difficult for students to 

understand in lecture. The addition of a little water to 

the die prevents rewelding of the two halves demonstrating 

the effect of surface contamination. (It has been noticed 

that the ~lay-~oh~~ spider die works better than the other 

brands). 

3. Using one of the dies, the students should slowly 

extrude a shape. A second shape should be extruded using 

much greater speed. The first shape should have a smooth 

surface and the second should be irregular due to "speed 

crackingN", common extrusion problem. his can also be 

done on the same extrusion as illustrated in Figure 6. A 

careful application of a small amount of water to the inside 

die face and the front (die side) of the clay can be used to 

increase the extrusion speed without the speed cracking 

showing the effects of lubrication. (Note: This may be a 

little tricky since the water will dissolve the clay if too 

much is used. Oil may be used but may also react adversely 

and may be more difficult to separate afterwards). 

4. Two experiments may be performed to demonstrate the 

material movement. In the first, two colors of clay are 

placed side-by-side with the intersection parallel to the 

extrusion axis. Extruding through a single hole die shows 

that the two colors maintain their respective positions. 

Placing the two colors so that the intersection is 

perpendicular to the extrusion axis and extruding 

demonstrates that the back color moves faster and moves 

inside the front color. The extruded shape can then be cut 

to show the extent of the movement. The amount of each 

color in a cross-section varies along the length of the 

extrusion as shown in Figure 7. Similar movement can also 

be demonstrated using the multi-small hole wspaghettivv die. 

5. The students should then be allowed to experiment 

with the equipment. 
SAlvIPLE DATA SHEETS: 

Putty: 1. Rebound height warm 

Rebound height cold 

Observations: 

2. Relative amount of force cold 

Relative amount of force warm 

Observations (include description of 

fracture surface) 

3. Sketch cylinder before and after deforming 

4. Descriptions and observations 

Extrusion: 

1. Die Shape Relative amount of force 

2. Observations 

3. Observations and sketches 

4. Sketch before and after for both cases 

5. Descriptions and observations 

INSTRUCTOR NOTES: The relative measurements should be 

made into a numerical form such as 1 (low), 2(moderate), and 

3 (hi.gh). The students will generally tend to play with the 

equipment for a fair amount of time after the designated 

experiments are over. Some of their documented observations 

may be included in future experiments. 

SOURCES OF SUPPLIES: The putty and the extrusion press 

can be obtained in most large toy stores (before Christmas 

is a good time to find them though both of these are usually 

available all year). It generally requires two putty eggs 

per student to give enough material to work with. These 

cost about $3-$4 per egg. The extrusion presses are less 

than $10. These are all 1990-1991 prices in the Phoenix, AZ 

area, All of these should last a number of years except 

that new clay may be required every year. The clay costs 

about $4 per 4 pack. (The clay becomes mixed and thus a 

generic off color. The mixing experiments require separate 

colors) . The measuring stick, if used, may be any available 

rulkr or may be made by the students out a piece of paper 

with regularly spaced lines drawn on it. 
Figure 1: Formable putty and packaging. 

The amount shown is from two eggs. 

Figure 2: Deformed putty which underwent a 

large amount of ductile plastic deformation. 
Figure 3: The fracture surface of the putty 

after brittle, high-rate deformation. 

Figure 4: Extrusion press showing die 

selection and packaging, 

OF{iGINPiE PAGE 

BLACK AND WHITE PHOTOGRAPH 
Figure 5: Hollow tube extruded from the 

Fun Factory. 

Figure 6: Rectangular shape extruded at 

slow then fast rates showing the transition 

to speed cracking. 

111 u'^4L. , 

BLACK Aka Wl-d;'i"E P;4f$TGGRAPH 
Figure 7: Shape extruded from two color 

dough arranged front-to-back in the press 

demonstrating the movement of the rear 

(lighter) color into the center of the 

front (darker) color. 
DIELECTRIC BE 

AT MICROWAVE FREQUENCIES 

Physics Department 

Southeast Missouri State University 

One University Plaza 

Cape Girardeau, Missouri 63701 

Telephone 3 14-65 1-2390 

DIELECTRIC BEHAVIOR OF SEMICONDUCTORS 

AT MICROWAVE FREQUENCIES 

J. N. Dahiya Physi cs Department 

Southeast Missouri State University 

KEY WORDS 

Semi conductors; frequency shift; Q-change; die1 ectric re1 a,xatl"sn, 

mi crowave resonant signal . 

OBJECTIVES 

1. To learn about the components of a microwave spectrometer. 

2. To learn to operate the spectrometer. 

3. To understand the shape of the signal and record data in terms 

of frequency shifts and Q-changes. 

4. To understand the dielectric properties of semiconductors: 

germanium and silicon. 

SUMMARY 

A cylindrical microwave resonant cavity in TEOll mode is used to 

study the dielectric relaxation in germanium and silicon. The 

samples of these semiconductors are used to perturb the electric 

field in the cavity and Sl ater's perturbation equations are used 

to calculate the real and imaginary parts of the dielectric 

constant. The dielectric loss of germanium and si 1 icon is 

studied at different temperatures and Debye's equations are used 

to cal cul ate the re1 axation time at these temperatures. 

INTRODUCTION 

A number of experiments have been performed to investigate the 

dielectric properties of sol ids, 1 iquids and gases at various 

frequencies (ref. 1-6). The present experiment is to study the 

dielectric relaxation mechanism in germanium and si 1 icon. 
The microwave resonant technique has been used by several 

investigators in the past and it has become a standard technique 

to study the di el ectri c behavior i n various compounds of 

interest. Wong and Roberts (ref. 7) used a cylindrical cavity in 

TMOIO mode to study the dielectric properties of solids and 

l iquid!~. Dahiya et al. (ref. 8-10) used a microwave resonant 

cavity to study dielectric relaxation mechanism in various polar and non polar compounds. 

It has proven to be a very interesting experiment to find the 

die1 ectric response of a material near a phase transition region, 

i . e, , goi ng from an ordered to a disordered phase. From 

rneasuriements of the static dielectric constant of compounds as a 

function of the temperature, important conclusions concerning molecular freedom may be drawn. The dielectric response of a 

polar liquid shows a large change at the freezing point. A 

typical example is that of water as studied by Dahiya et al. 

(ref. 8). The drop in the dielectric constant of water at the 

freezing point is caused by the partial or complete loss of 

rotational pol ari zati on (freedom to reorient) , whi l e the 

el ectroni c and vibrational pol ari zati ons remain re1 ati vel y 

unchanged. 

In the present investigation, dielectric behavior of 

semiconductors, germani um and si l icon were studied at different 

temperatures. The sample under investigation was placed along the vertical axis of the cavity. The sample was taken in a 

capillary tube and the thermocouple leads were inserted into the 

capillary tube to make a fine contact with the sample. The 

sample was then cooled by flushing cold nitrogen gas around the 

cavity and desired temperature was obtained. The temperature was 

then allowed to vary in small steps and frequency shifts and Qchanges were recorded. 

EQUIPMENT CONFIGURATION AND THEORY 

The block diagram of the microwave spectrometer used in this 

investigation is shown in Figure 1 that shows all the components needed to study the die1 ectri c re1 axation mechani sm. The source 

of the microwaves was a 2K25 tunable klystron made by Western 

Electric. The frequency produced by the klystron varies between 

8.8 to 11.0 GWz. The klystron was powered by a Wewlett Packard 

7B5A power supply. The microwaves produced by the klystron were 

guided by waveguides in the x-band of frequency. The signal 

reaching the directional coupler was divided into two parts. A 

part of this signal reaches the microwave resonant cavity via an 
attenuator and a wavemeter. The attenuator was used to adjust the right amount of microwave power for the sample being studied, 

The function of the wavemeter is to determine the exact frequency of the klystron by tuning it to the resonant frequency of the 

klystron. 

The next important device in this operation is a crystal detector 

which is used for the radio frequency wave. Crystal detectors 

have wide use in the microwave field because of their sensitivity and simp1 ici ty. They are used as "video detectors" to provide either a dc output when unmodulated microwave energy is applied, 

or a low frequency ac output when the microwave signal is 

modulated. The essential parts of a crystal detector are a 

semiconducting wafer and a metal "whisker" which contacts Lhe 

wafer. In the present experiment two such crystal detectors were 

used, one of which was installed in the reflectometer to provide dc output when the klystron modulated signal is reflected from 

the resonant cavity. Another crystal detector was mounted in a 

directional coupler to mix the modulated klystron signal with the 

nth harmonic waves from the standard frequency mu1 ti pl i er. 

The purpose of modulating the microwave signal was as follows, 

The unmodulated signal from the klystron gives a very narrow 

frequency interval as shown in the microwave power vs frequency 

curve in Figure 2a. With a signal like that it is very difYicult 

to measure the shifts in frequencies and the Q-changes of the 

signal . An osci l l oscope horizontal sawtooth sweep voltage was 

applied to the repeller of the klystron. This voltage was 

derived from the time base of a Tektronix model 533A dual channel 

oscilloscope that sweeps the klystron over the range of 

frequencies desired whi l e simultaneously a chopper signal of 31 

kHz was impressed upon the klystron repeller electrode to produce 

an ac signal of that frequency at the detector. The modulated 

signal is shown in Figure 2b and Figure 2c shows the reflected 

power absorption by the resonant cavity. As shown in Figures 3a 

and 3b, the power absorption by the cavity was modulated to give 

a differential display of the resonance profile in the form of a 

butterfly. Figures 3c and 3d show the modulated signal before 

the sample under investigation was introduced into the cavity and 

after the sample had been introduced respectively. The resonance 

frequency shifted and the width of the signal changed as seen in 

Figure 3d. The modulated signal was amp1 i fied by a pre-amp1 i fier 

and displayed on the oscilloscope. 

Through the Webster 640P5158 directional coupler, a part of the 

microwave signal was mixed with a standard frequency obtained 
from a Hewlett Packard 612A UHF signal generator. A Kenwood R1000 radio receiver was used to detect the frequency difference 

between the klystron resonant frequency and the standard 

frequency source. The resulting frequency difference yielded two 

markers which were displayed on the oscilloscope. These markers 

were used to record the frequency shifts and the Q-changes of the 

resonant signal as the cavity was loaded with the sample under i nvestigation. 

A cylindrical cavity in the TEOll mode was designed. A long 

copper coil was wrapped around the cavity and the cavity placed 

in a thermal bath. As the sample under investigation is 

introduced into the cavity it perturbs the electric field of the 

cavity and as a result of that the resonant frequency shifts and 

the Q of the cavity changes. The frequency shifts and Q-changes 

sf the signal are related to the real and imaginary parts of the 

dielectric constant through the Sl ater's perturbation equations 

as follows. (ref. 8) 

1 I gs . Zdv and A(-) = el1 

Q IZ*Za dV 

where 2 is the field of the unperturbed cavity. Ea is the 

microwave field as applied to the cavity and E, is the field of 

the sample itself, and v and V are the volumes of the sample and 

cavity respectively. 

The signal Q-change is further related to the width of the signal 

by 

where f, is the resonant frequency of the system and W is the 

frequlency separation in Hertz of the resonance half-power PO^ M&S. 
The real and imaginary parts of the dielectric constant ~"nd C" 

are further related to the relaxation time (T) using DebyeVs 

equations (ref. 11) as follows. 

where o = 2nfo. and E, is the value of the dielectric 

permittivity for a static field. 

PROCEDURE 

The sample under investigation was taken in a fine capillary 

tube. A thermocouple was inserted into the tube to make a fine 

contact with the sample inside the tube, The capillary tube was 

then inserted into the microwave resonant cavity along the 

symmetry axis of the cavity to ensure a sizeable perturbation of 

the microwave resonant signal. The thermocouple was insertfed 

into the capillary tube to ensure it was making a fine cont.act 

with the sample inside that tube. The initial readings of the 

temperature, and microwave frequency were recorded. The cavity 

was then cooled to the desired temperature by circulating cold 

nitrogen gas through the copper tube wrapped around the cavity. 

The system was then allowed to warm and the readings were taken 

by adjusting the markers on the center and left and right peaks 

of the microwave resonant signal. These readings were taken at 

an interval of 1°C till the desired temperature of the system was 

achieved. At each reading, sufficient time was allowed to elapse 

so that the sample and resonant cavity came to thermal 

equi l i bri um. 

RESULTS AND CONCLUSION 

The frequency shifts and the width changes of the microwave 

resonant signal for the semiconductors germanium and silicon were 

calculated by using Slater's perturbation equations 1 and 2 in a 

computer program written for microwave spectroscopy studies. As 

seen from these equations, the frequency shifts and the width 

changes are related to the real and the imaginary parts of ,the 

complex dielectric constant. Figures 4 and 5 show the behavior 

of Q-changes of the signal (b(l/Q)) and frequency shifts (bf/f,) 

as a function of temperature. As seen in Figure 5, the frequency 

shift increases with temperature with its minimum value at 

84.8 K. Smakula et al. (Ref. 12) studied the dielectric behavior 

of this semiconductor at very low temperature and it seemed to 
have another minimum around 4 K. Figure 4 shows a similar 

behavior of the Q-change with a minimum value around 84.8 K and a 

maximum value around 196 K and it decreases as the temperature 

increases up to 300 K. The low temperature studies of this 

material indicate another maximum around 10 K as shown by Smakula 

et al. (Ref. 12). Figures 6 and 7 show- behavior of Q-change and 

the frequency shift for silicon between 70 K and 300 K. The 

re1 axition times for these semi conductors were cal cul ated using 

equation 4 and were of the order of 10- lI-10-l~ set. 

The bound electrons and the free carriers in a semiconductor 

material account for the dielectric permittivity and the 

conductivity of the materi a1 . The bound electrons in the 

semiconductor can be categorized as the core electrons of the 

materi a1 s, the valence electrons, and the electrons from the 

impurity atoms. The valence electrons and the core electrons 

have excitations in the infrared frequency regions. The 

permittivity of these electrons may not have any imaginary term 

and these electrons do not show any temperature dependence at 

very 1 ow temperature. However, the impurity electrons vary with 

temperature and thus affect the complex permittivity or the 

die1 ectri c constant of the materi a1 . 

In khi s i nvesti gati on, a mi crowave spectrometer was assembl ed to 

study the dielectric re1 axati on in various compounds of interest. 

The spectrometer was designed to study these behaviors at very 

low temperatures. The technique was very successful in 

monitoring the dielectric behavior of germani um and si l i con. The 

main emphasis of this research was to create an advanced physics 

laboratory experiment in which undergraduate students were 

involved to design the spectrometer piece by piece. The 

spectrometer was then used as a tool to study the dielectric 

behavior of various polar and nonpolar compounds. Semiconductors 

germanium and si l icon were chosen for their dielectric behavior 

at low temperatures. The cooling system used in the microwave 

spectrometer was also designed by undergraduate students and was 

very ed-fi ci ent. 

The main purpose of this experiment was to understand the 

function of each component of the microwave spectrometer and to 

use it. as a technique to monitor the dielectric behavior in 

semicc~nductors germanium and silicon at low temperatures. The 

detai l ed resul ts of the dielectric re1 axati on in these 

semiconductors will be presented elsewhere as a continuation of 

this experiment. 
REFERENCES 

I. Baynham, A. C., Gibson, A. F., and Granville, J. W.: On the 

Di el ectri c Constant of Germani um at Mi crowave Frequencies. 

Proc. Phys. Soc., 75, 1960, p. 306. 

2. Lurio, A,, and Stern, E.: Measurements of the Dielectric 

Constant of BaTi03 Single Crystals in the Paraelectric 

Region at X-band. J. Appl . Phys., 3l, 1960, p. 1805. 

3. Nishioka, A., and Takeuchi, M.: Dielectric Property of 

Triglycine Sulphate Single Crystal in the 9,000 Mc/s 

Region. J. Phys. Soc. Japan, 14, 1959, p. 971. 

4. Surber, W. H., and Crouch, G. E.: Dielectric Measurement 

Methods for Sol ids at Microwave Frequencies. J. Appl . Phys., 19, 1948, p. 430. 

5. Grant, E. H., Buchanan, T. J., and Cook, H. F. : Diel~!ctr.ii c 

Behavior of Water at Microwave Frequencies. J. Chem. 

Phys., 26, 1957, p. 156. 

6. Birnbaum, G., Kryder, S. J., and Lyons, J.: Microwave 

Measurements of the Dielectric Properties of Gases. J. 

Appl. Phys:, 22, 1951, p. 95. 

7. Wong, K. H., and Roberts, J.A.: Microwave Properties of 

Liquids and Solids Using a Resonant Microwave Cavity as a 

Probe. 3. Appl. Phys., , 1974, p. 2452. 

8. Dahiya, J. N., Jani, S. K. and Roberts, 3. A.: Phase 

Transition Studies in Polar and Non-Polar Liquids at 

Mi crowave Frequencies. J. Chem. Phys. , 1981, p. 

3609. 

9. Jani, S. K., Dahiya, J. N. and Roberts, J. A,: Dielectric 

Changes in Hyal uronate Sol uti ons at Mi crowave Frequencies 

as a Function of Concentration, System pH and Temperature. 

Bioplymers, 19, 1980, p. 931. 

10. Dahiya, J. N., and Freeman, R. W.: Computer Interfacing of 

a Microwave Resonant Cavity for Temperature Measurements 

During Dielectric Re1 axation. Computers in Physics, 

Jui/Aug. 1989, p. 49. 
11. Debye, P. Plar Molecules (Chemical Catalog, New York), 1929, 

Chapter 5. 

12. Smakula, A., Skribanowitz, N., and Szorc, A.: Dielectric 

Properties of Semiconductors at Low Temperatures. J. 

Appl . Phys., 43/21, 1972, p. 508. 
POWER I SUPPLY 1 

n PRINTER 

FREQUENCY 

MARKERS 
. ~ 

2. (a) Klystron mode shape (unmodulated width). 

(b) Klystron mode shape (modulated width). 

(c) Reflected power absorption by cavity. 
3. (a) Enlarged drawing for power absorption by the cavity. 

(b) First derivative of resonance absorption. 

(c) Resonance absorption signal (unperturbed). 

(d) Resonant frequency shift and width change due to 

insertion of the sample into the cavity. 

181 
ARBITRARY UNITS 

A.-r.-rANr\aM 

Q,OsONQ,QsoNa 

m 

a 

A 

d 

0 

d 

a 

es 

4 

8\3 

A 

a 

M 

C911 a) 

G3 

mmia 

a 

4. Microwave loss A(l/Q) as a function of temperature for a 

sample of semi conductor germani urn. 
ARBITRARY UN 

5. Frequency shift Af/fo as a function of temperature for a 

sample of semi conductor germani urn. 

183 
A TRARY UNITS 

6. Microwave loss A(l/Q) as a function of temperature for a 

sampl e of semi conductor si l i con. 

184 
TRARY UNITS 

7. Frequency shift hf/fo as a function of temperature for a 

sample of semi conductor si 1 icon. 

185 
CIPITATION ENING EXPERIMENT 

Richard L. Cowan 

Department of Mechanical Engineering 

Ohio Northern University 

Ada, Ohio 45810 

Telephone 4 19-634-7520 

PWECEDiNG PAGE BLANK NO% RUihiMED 

187 
Be-Cu PRECIPITATION HARDENING EXPERIMENT 

Richard L. Cowan 

Ohio Northern University 

Ada, Ohio 

KEY WORDS: precipitation, aging, hardening, solution annealing, 

super saturation, beryllium-copper alloys 

PRWEQUISITE KNOWLEDGE: The student performing this experiment 

should have a knowledge of binary phase diagrams. 

OBJECTIVES: The objectives of this experiment are: to give the 

student a hands-on approach to changing materials properties 

through heat treatment of a specimen; to quantify the amount of 

strengthening obtained in the specimen; to encourage the student 

to speculate about the structural changes that have occurred in 

the material to cause the changes in strength. 

EQUIPMENT AND SUPPLIES: 1) small furnace with capability of 

maintaining a temperature of 500 C +/- 5' C. (If solution anneal 

is to be done in the same furnace, temperature capability should 

be 800 C); 2) hardness tester with a range of 60 - 350 Brinell 

hardness; 3) small (1 gallon) water quench tank; 4) tongs to 

handle hot specimens; 5) insulated glove; 6) conversion chart 

for R, and R, to Brinell hardness (not needed if you have ~rinell 

tester) 7) a Cu-Be phase diagram for the 0 - 10% Be region (see 

Fig. 1) 8) several (9) 2.5 cm diameter x 1 cm thick specimens of 

Cu - 1.8 Be or Cu - 2.0 Be. 

PROCEDURE: Precipitation hardening depends upon the controlled 

precipitation of a constituent from a supersaturated solid 

solution. The precipitation rate depends upon the treatment 

temperature. As the temperature approaches the solvus line for 

the alloy of interest the faster the reaction will be.[ll 

The students are provided with approximately ten solutionannealed disks of Cu - 1.8 Be and they develop a hardness vs. 

aging time graph at a specific temperature (e., 400 C). 

~nstructions to the students are as follows: 

 quip the hardness tester to take readings on the 

Rockwell B scale (100 kg load - 1/16" ball penetrator). 

Check the reading of the tester with the standard 

block. 

BREEDING PAGE BLANK NOT FOEMED 3 
2. Take three hardness readings on each disk. Average the 

readings on each disk and record them. 

3. Check the furnace temperature. It should be at the 

temperature specified for your group. 

4. Place the disks in the furnace near the center. Orient 

them so there will be easy access to remove them 

individually. 

5. At the following times specified, remove the disks and 

quench them immediately: 2, 4, 6, 8, 10, 20, 30, 45, 

1 hr., overnight. 

6. Measure the hardness of the aged specimens and record 

the values. 

7. Plot the Brine11 hardness vs. log of time in seconds 

for the specimens. (If the hardness readings for the 

solutionized disks vary more than + 3 points Rockwell 

B, plot hardness increase vs. aging time.) 

The students follow the above procedure to obtain their 

data, They are then required to do the following in the 

discussion of the experimental results. 

1. Relate the micro-structural changes that are occurring 

in the specimen as it is solution annealed and 

quenched, reheated and quenched repeatedly to the Be-Cu 

phase diagram. 

2. Explain why the hardness of the specimen is increasing. 

Relate this change in hardness to the micro-structure. 

3. What would you expect the aging curve to look like if 

the aging temperature was 50" lower? 

4- 50" higher? 

5. Explain answers to 3. and 4. based upon the phase 

diagram. 

6. Did overaging occur for any of the specimens? If it 

did, explain what happened. 

7. Sketch how you would expect the micro-structure to 

appear for a hardened material prior to over-aging. 

8. Same as 7 except after over-aging. 

9. Sketch the micro-structure if the material had cooled 

under equilibrium conditions from the solutionizing 

temperature. 
10. For 9, would the material be harder or softer than if 

it was quenched? 

11. Comment on 7, 8, 9, and 10. 

12. At what temperature do you think the material was 

solutionized? 

LE DATE SWEETS: Self-Evident 

INSTRUCTOR NOTES: Specimens can be cut from round, square, or 

other available bar stock. They should be solution annealed at 

approximately 750 C. They may begin to melt if you heat them to 

850 C, At 700 C the disks will not solutionize in a reasonable 

amount of time. 

Samples that have been cut approximately one centimeter thick 

will solutionize in 20-30 minutes at 750 C. They should be 

removed from the furnace and immediately quenched and agitated in 

water. Specimens solutionized in this manner will have an 

approximate hardness of 40 Rockwell B. 

Take hardness readings after solutionizing, and then group 

disks by hardness range so that you minimize initial hardness 

spread for the students. One group of 6 or 7 samples may be in 

the range of Rockwell B 40-45; another group in the range of 

Rockwell B 35-40. 

Aging times are cumulative so that the students do not need 

a separate disk for each aging time. Students should be told to 

take hardness readings on one side only. After a few cycles 

through solution annealing and aging, the disks can be faced in a 

lathe and the sequence can start again. This can be continued 

until there is no longer enough material to grasp in the lathe 

collets or chuck. 

Whenever the material is machined the machine 

operator must take precautions to avoid 

breathing any dust generated. The material 

should be machined wet, or in a hood, or the 

operator should wear a mask. 

No harmful oxides are generated at the aging 

temperatures. The oxides that form on the 

surface are copper oxides, 

Different groups of students can age their specimens at 

different temperatures. Then when they compare results they can 

see the shift in the aging curve. 

Best control of properties is obtained when the speci~ciens 

are aged at 350 C. But, it takes over two hours to obtain 

maximum strength and most lab schedules are not long enough to 
permit using this temperature. Temperatures used to aging are 

400 C, 450 C, 500 C, and 550 C. 

Metallography is not an appropriate addition to this experiment 

because the precipitates that increase the hardness cannot be 

seen in an optical microscope. 

REP CES: Askeland, D. R. The Science and Engineerins of 

Hater-, Alternate Edition, PWS Engineering, 1985, pp 215; pp 

251. 

MetalsHandbook, Volume 8, AmericanSociety forMetals, 8thEdition, 

Sept.1973. 

SOmCES OF SUPPLIES: Cu-1.8 Be bar stock from Brush-Wellman, 

Inc,, 19876 St. Clair Ave., Cleveland, OH 44110. The material, 

solution annealed or as drawn, costs $10.50 to $15.00 per pound. 
Or Atomic Percentage Bery Illurn 

Weight Percentage Beryllium 

Figure 1. Cu-Be Phase Diagram [2] . 

ASTM = TERMINOLOGY FOR EXPERIMENTS 

AND TESTING 

Richard R. Strehlow 

ASTM Committee on Terminology 

Oak Ridge National Laboratory 

Martin Marietta Energy Systems, Inc. 

P. 0. Box 2008 

Oak Ridge, Tennessee 37831-6263 

Telephone 6 15-574-4956 
Richard A. Strehlow 

Oak Ridge National Laboratow * 

Ghaiman, ASTM Committee on Terminoloa 

The materials produced by modern teclnnolo&sts are stunning and exciting. 

Every one of them is, however, associated kth a Ifamily of immate~alis--a11 the 

concepts of substance, process, and purpose. It is concepts that are essential to 

transfer knowledge. It is concepts that are the stultF of ter~nolom. 

Terminology is standardized today by companies, standards orgaliaiizations, 

ends, and other groups. Siqly desc~bed, it is the pre-negotiation of the 

meanings of terms. Terminology has become a key issue in businesses, and 

ter~nology knowledge is essential in understanding the modern world. 

The fundamental objective in terminology standardization is to decrease 

adiguity in interpreting, understanding, and using language and to explain 

meanings of technical terms do those who are not conversant writh dhenl, It is a 

key element in infomation ret~eval and database desi~. 

Tbs 98 minute introcluGtory workshop introduces the concepts of terminolom and 

methods of its standardization. Exer&ses are used along with the preseretatisn to 

rapidly survey and expel.lience several aspects of contemporary termnno8ogy, 

Some of the questions to be addressed include, as examples: 

mat is a tern and what constituks a satisfactory desnition statement? 

How does teminolom relate to deE~tion of data elements in dabbases'? 

* Wow does ASTM manage kminolom in a 35,000 member organization? 

mat is the role of standard teminolo@es in the process of explanation." 

* Now can terminolo@es be exchanged between diEerent cound~es ~th different 

languages? 

Tlhe objectives of the workshop are to enhance termindo@cal awareness and to 

demonstrate the usefulness of ASTM source mate~als for both 1iaboraI;ory and 

classroom teaching. 

* Operated Boy Martin Marietta Enere~gr Systems, Ine., under U. S. Department of 

Enerm contract DE-AG05-840R21400 














"Science in Action": An Interdisciplinary Science Education Program 

L. k. Horton 

Metals and Ceramics Divdsiom, Oak Ridge National Labesratony" 

Oak Ridge, 73-4 37831-6118 

Science in Action is an education outreach program for pre-collegiate students. It is based on [he concep!. 

that, in order to interest students in science, they must see science and scientists at work. The program 

encompasses the full range of scientific disciplines - the core sciences, engineering and matl~ematics. A 

unique aspect of the program is the involvement and support of scientists and engineers re~~resenting local 

professional societies, industries, businesses, and academic institutions. 

The first "Science in Action" program took place during National Engineers7 Week in 2990; the second 

expanded program at the same time in 1991. "Science in Action" is part sf the annual WKmeC 

conference in Knoxville, 724. The WAmeC conference is a week-long technical conference sponsored by 

a consortium of local professional/technid societies. The theme for the past several years has focussecl oil 

"competitiveness." Since the education of our young people is an essential part of "being competitive," tLhe 

educational program was a natural outgrowth of the conference. 

For the 1990 program, "Science in Action" was a hvo-day program specifically targeted to rnlddle school 

students and was held in a multi-story building, the Candy Factory, at the World's Fair Site in downtown 

Knoxville. We wanted to reach students before they made the fatal decision to drop out of the advanccd 

mathematics curriculum in high school. On each day of the program, 6 middle schools were invited to 

bring 40 students and teachers. Although only 5 of the schools were able to attend on the scheduled days, 

because of the enthusiasm for the program, the attendance on the first day neared 300 and on thc second 

about 250. The middle school teachers and administrators were thrilled that someone was finally having a 

special program for them .... they were really appreciative. 

In 1991, "Science in Action" expanded to bur days and moved to the 'Fennessee Valley Authority (WA) 

Towers, also located in downtown Knoxville. The move permitted consolidation of the progsam on a single 

floor of the building. However, because of the size of the auditorium in the WA Towers, actendance was 

limited to about 200 students each day. The first day was devoted to elemenkargr school students. Smal: 

groups (5 students and a teacher - a "car load") were invited from the elementary schools in the 

surrounding cities and counties. Over 30 schools were able to participate. The second and third dqs 

followed the 1990 middle school format (although we reduced the number of students invited Gom each 

school to 30); nine middle schools participated. fie final day involved small groups of 8 to 10 students 

from the 15 high schools. For this program, we did noh design the program for the top few students in %he 

school; these students have many opportunities to visit Oak Ridge National Laboratories and other local 

technical businesses. Instead, we specifically targeted students who are interested in science but are not 

currently considering it as a career. The program emphasized the broad range of potential carcers En 

science and engineering-related fields. 

The goal of the presentations is to be highly interactive. We want the students to have some '"hands on" 

experiences and to leave with a good feeling about science and engineering. To present a broad spcctrum 

of role models, scientists and engineers were involved as presenters, guides, and exhibitors. Paesentathons 

for "Science in Action" followed the format: Keynote Presentation followed by Small Group iFgresentalio~;s 

PRE=DEB14l.,'G PAGE BLANK NOT FibMED 
and visits to the Mibit area. In 1990, the exlhibits were available for the students to visit before the 

program and during lunch. In 1991, the program was modified so that a visit to the exhibits was considered 

one of the smalll group presentations. The keynote was the only presentation given to the group as a 

whole. After the keynote, the group split into the individual school groups for the remainder of the 

program. The groups cycled through the balance of the presentations; each presentation was given to each 

school group. '[n order to allow maximum participation and have appropriate presentations for the age of 

the students, there was a different set of presentations on each day. 

Ke~note Presentations: The keynote presentation in 1990 was "Creatures of the Night" by a local 

veterinarian. The presentation focussed on animal science and environmental science (the habitats of all 

animals). Live owls and opossums were an integral part of this program; the students were able to actually 

touch the animals. 

For 1991, the keynote varied with the age group of the students. '"aptor Tales" was presented by the 

Clinch River R.aptor Center to the elementary and one group of middle school students. This program 

informed the sltudents of the value of raptors and their place in our environment. Live raptors were a 

major part of the program; the birds were handled by middle school age children who work at the Raptor 

Center. The second middle school keynote was "Fun with Chemistry," an introduction to chemistry given by 

a professor from Tennessee Technological University, Cooke~1Be. "Fun with Materials," an introduction to 

materials science and engineering, was the keynote presentation for the high school students. (Detailed 

description can be found under the small group presentations.) 

1990 Small Gr~up Presentations: The small-group presentations covered a wide range of topics. Two of 

the most popular were "Fun with Materials" and the "Magic of Chemistry in Today's World." The "Magic 

of Chemj~stq Today's World" was an interactive demonstration of chemical reactions -- all performed 

with chemicals that could be obtained in supermarkets. The "Fun vvlth Materials" presentation is an 

adaptation of the original presentation by Bob Pond, an emeritus Johns Hopbns professor who is known 

throughout the United States for his "Fun with Metals" presentations. The students learned about the 

p roperties of rnaterials and how materials scientists modify the properties for specific applications. N1 

participants left with an aluminum "coin" that showed the crystal structure of the metal. A lucky few were 

able to catch some melt-spun tin as it left a round cake pan spun by a drill. The tin was melted inside of a 

foot-long glass dropper by a standard home worhhop propane torch; students operated the drill. 

In "'The Microscopic World," the students were able to operate a real scanning electron microscope (SEM) 

(courtesy of alae Metals and Ceramics Division, Oak Ridge National Laboratory). In the SEM, they were 

able to view insects, fractured surfaces of metals, diamond films, a human hair, and an integrated circuit. 

They also saw the "creatures they swam with in the pond last summer" in a life-sciences optical microscope 

demonstration. Two top-of-the-line metallographic microscopes were also part of this popular presentation. 

The presentations focussed on what we learn from microscopy and how this information is used in scientific 

and engineerimg investigations. 

The noisiest presentation was "Neat Stuff with Humans." Presented by the Institute of Industrial 

Engineers, the presentation included a robot, a demonstration of bow to design an effective assembly line 

(the students assembled ball point pens with a variety of approaches), and the impact of excessive noise on 

the quality of production (students attempted to communicate data while the group provided background 

noise). 

In 'XRadibn, It's Only Natural," students learned about the occurrence of radiation in our natural 

environment, how radiation is detected, and how it is used. "Fun with Figures" focussed on mathematics 
and how it can be fun, with various mathematical tricks and short cuts. "A Hitch-Hikers Tour of the Solar 

System" consisted of a slide show from various space explorations. 

1991 Small Group Presentations: In 1991, we repeated several of the 1990 presentations. For the 

elementary students, "Fun with Materials" and "Fun with Rocks and Minerals9' were prese:nted. "Fun with 

Rocks and Minerals" explored the history of the earth through rocks and fossils. The stlldents hammered! 

on rocks to learn about the difference in hardness and left the demnstration with their own personal 

fossil. 

The middle school presentations included "Fun with Materials," "Statistics," "Electricity and Magnetism," and 

"Ceramics Processing." The statistics presentation introduced basic mathematical concepts related to 

statistics. The electricity and magnetism presentation included hands on demonstrations. Ceramics 

Processing focussed on modern methods of processing ceramics. It involved a microwave oven for heating 

ceramics and a demonstration of how chemistry is used to process ceramic powders. A magnet was floated 

over a high temperature ceramic superconductor and a number of high tech ceramic car parts and a space 

shuttle tile were on display. 

For the high school students, the small group presentations were "Electricity and Magnetism" and 

"Radiation: It's Only Natural" (presented in 1990). Both of these presentations were elevated to the high 

school level and stressed possible careers in these important fields. 

Exhibits: In addition to the presentations, there were exhibits from a number of technical sodeties and 

local facilities. In 1990, the students visited these exhibits prior to the beginning of the pi-ogram and during 

lunch. In 1991, due to the interest in the exhibits and the positive interactions between the students and 

the people manning the exhibits, a visit to the exhibit area was made an official "small group presentation." 

Each of the student groups was assigned a period of time for visiting the exhibits. 

A variety of exhibits was on display each year. The University of Tennessee (UT) student chapter of 

ASM International had a display that included shape-memory alloys. In 1990, the biomedical engineers 

exhibited medical equipment such as a blood pump (demonstrated with a full-scale model of the circulatory 

system) and a number of other biomedical devices. This was a very popular exhibit; we were dkmaye~d 

when this group could not schedule an exhibit for 1991. 

In 1990, there were wooden models of various types of structures in the display sponsored by the civil 

engineering group. This exhibit was considerably expanded for 1991 to include numerous examples of civil 

engineering including road and bridge materials. The American Nuclear Society had an exhibit of how 

radioactive materials are used in our lives every day. 

In 1990, the High Temperature Materials Laboratory from ORNL had a light-box display that highlighted 

various materials developments for high temperature environments. For 1991, the numbelr of light boxes 

was reduced and the exhibit expanded to include a superconductor demonstration and a dlisplay of car parts 

fabricated from ceramics. 

The National Organization for the Professional Advancement of Black Chemists and Chernical Engineers 

(NOBCChE) sponsored a computer game that tested knowledge of the contributions by bliack scientists and 

engineers. In 1990, they also had a number of drawings by local school children that focussed on the 

theme of environmental protection. In 1991, there was a working model of a refrigeration cycle. 
One of the higlllights of the 1998 exlaibits was an infrared camera provided by AkCOA Infrared photos 

were taken of each of the students. The application of this technology in manufacturing was discussed 

durrng thc exhilbit. ALCOA also provided an ehibit on aluminum recycling. 

In 1991, the mih;roscopy small group presentation became part of the exhibit area. Due to logistic 

difficulties and expense, the scanning electron microscope was not part of the exhibit. The pond water 

miciroscopy and optic metallographic instruments were retained and were a great success. 

For the upper level students in 1998, the Information Sciences group had an exhibit that described how 

information science is used in engineering and technology. Oak Ridge Associated Universities (OW) 

also sponsored an eAibit on its programs for high school and college students. 

The co-organizers of "'Science in Action" are Linda Horton, ASM International, and Julie Watts, 

Association for Women in Science. Both Horton and Watts are also staff members at Oak Ridge National 

Laboratory ((ORNL), a facility operated for the Department of Energy by Martin Marietta Energy Systems 

(MMES). In 1990, the program was held at the East 'Fennessee Discovery Center (ETDC), located at the 

Woirld9s Fair site in downtown boxville. A pizza lunch was provided for all participants, presenters, 

guides, and ehibihors. For 1991, the program was moved to the TVA Tower office buildings, a more 

con-savenient location. Also, while the students enjoyed the pizza, serving it presented logistic nightmares. In 

1991, bag lunches were provided. 

The success of this program is the result of the cooperation and integration of the local technical and 

professional soc:ieties. Obviously, those involved also have the full support of their employers. In addition 

to support Gomi ORNL, MMES, WA, ALCOA, and the ETDC, many other groups contribute to the 

program. A partial list of these includes OW, Carl Zeiss, Inc., International Scientific Instruments, Inc., 

UT, Science Applications International Corporation, Grumman Aerospace, Pizza Hut, Dillard Paper 

Company, Pellissippi State Community College, and California State Polytechnic University. Professional 

socaeagr involvexslent also included the Institute of Industrial Engineers, the Wealth Physics Society, 

NBBCChE, the Project Management Institute, the Arnerican Nuclear Society, the Tennessee Society of 

Prolessional Engineers, and the herican Society of Civil Engineers. 

The support of employers is surprisingly easy to obtain. Representatives of local businesses serve on the 

Board of Directors of WAneC. In addition, education activities have the unqualified support of both 

Mvin Trivelpiece, the Director of ORNIL; Clyde Hopkins, the President of MMES; Richard Ray, the 

Manager of MCOA; and Jon Veigel, the President of OW. Most importantly, however, eveqone 

involved is interested in promoting science education in our schools. All are volunteers who use a 

tremendous wurnber of hours of their personal time on behalf of "Science in Action." 

a: Research sponsored by the Division of Materials Sciences, U.S. Department of Energy, 

under contract :DE-AC05-840W21400 with Martin Marietta Energy Systems, Inc. 
SOURCES OF SUPPORT FOR ENGINEERING 

EDUCATION 

William Gamble 

American Society for Engineering Education 

Suite 200 

Eleven Dupont Circle 

Washington, DC 20036 

Telephone 202-293-7080 
ASEE FELLOWSHIP PROGRAMS 

Bill Gamble 

ABSTRACT 

* Helen Carr Fellowship Program-As a way of addressing the lack 

of engineering faculty role models at the HBECs, the 

Historically Black Engineering College Committee(WBECC) 

instituted the awarding of yearly fellowships to 

African-American faculty members or students in pursuit of the 

doctoral degree.Upon completion of the doctoral degree 

requirements, a fellow is committed to return to one of the 

WBEC institutions. 

* ONT Postdoctoral Fellowship Program-The Office of Naval 

Technology (ONT) sponsors a Postdoctoral Fellowship Progx:am at 

a number of Naval R&D centers and laboratories. The prcigram 

is designed to significantly increase the involvement 05 

creative and highly trained scientists and engineers frola 

academia and industry in scientific and technical areas of 

interest and relevance to the Navy. 

* U.S. Navy-ASEE Summer Faculty Research Program-The U.S. NawASEE Summer Faculty Research Program provides science amdl 

engineering faculty members from colleges and uni~ersit~ies 

the opportunity to participate in research at Navy 

laboratories for a ten week period during the summer break,, 

Participants work with professional peers in the Navy 

laboratories on research task of mutual interest. 

+ U.S. Navy Graduate ello ow ship Program-As a means of increasing 

the supply of U.S. citizens trained in disciplines of science 

and engineering critical to the U.S. Navy, the Off ice of Naval 

Research(0NR) plans to award as many as 50 new three-year 

fellowships to recent outstanding graduates to support study 

and research leading to doctoral degrees in specified 

disciplines. 

* WISE Program-Fifteen students will be selected in nationwide 

competition to spend 10 weeks in the summer of 19992 in 

Washington, DC learning how engineers contribute to publie 

policy decisions on complex technological matters. 

* NASA Summer Faculty Fellowship Program-In a series of 

collaborations between NASA research and development centers 

and nearby universities, engineering and science faculty 

members spend ten of eleven weeks working with professl.onal 

peers on research. 

PRECEDING PAGE BLANK NOWFILMED 
ASEE FELLOWSH P PROGRAMS 

For more inlormation contacl: 

AEE-Projects Office 

Eleven Dupont Circle, Suite 200 

Washington, DC 20036 
DETE IINING SIGNIFICANT MATERIAL 

PROPERTIES, A DISCOVERY APPROACH 

West ern New England College 

1215 Wilbraham Road 

Springfield, Massachusetts 01 119 

Telephone 413-782-1220 
Determining Significant Material Properties, A Discovery Approach 

Alan K. Karplus 

Western New England College, Springfield, MA 

KEY WORDS: plastics, recycling, mechanical properties, tensile 

test, statistical design of experiments 

PREREQUISITE KNOWLEDGE: The experiment itself can be informative 

for persons of any age past elementary school, and even for some 

in elementary school. The preparation of the plastic samples is 

readily accomplished by persons with reasonable dexterity in the 

cutting of paper designs. The completion of the statistical 

Design of Experiments which uses Yatesf Method requires basic 

math (addition and subtraction). Interpretive work requires 

plotting of data and making observations. Knowledge of 

statistical methods would be helpful. 

OBJECTIVES: The purpose of this experiment is to acquaint 

students with the seven classes of recyclable plastics, and 

provide hands-on learning about the response of these plastics to 

mechanical tensile loading. 

EQUIPXENT AND SUPPLIES: 1) recyclable class 1 - PETE plastic 

container such as a Sprite, Coca-Cola, or Pepsi 2 liter bottle 

large enough to make 8 samples (other recyclable plastic 

containers with recycle codes are listed in Appendix A and for 

more discussion on plastics and their properties see Smith, 

Askeland and callister [1,2,3] ); 2) sample templates* which 

follow the American Society for Testing and Materials [4] 

specification Part 35 D638-80 type IV style (or equivalent); 3) a 

utility knife for scribing out the samples; 4) a 'magic' marker 

to label the samples; 5) a data sheet as laid out in Appendlix @ 

for a) sample preparation, b) data tally, and c) descriptive 

comments; 6) a tensile testing machine with a) grips suitable to 

hold the thin 0.5mm +/- 20% (0.020 in. +/- 20%) samples, b) 

position control to specify stretch or deformation rates of 500 

rnm/min. (20 in/min.) and 50 mm/min. (2 in. /min. ), and c) a inethod 

of recording the maximum first load held by the sample (see data 

sheet) which could be taken from a load versus deformation graph 

prepared while each specimen is testediand 7) Normal Probability 

paper available from a stationary store. 

PROCEDURE: The procedure requires making samples from recyclable 

plastic containers, pulling the samples apart, and evaluating the 

test results to determine if the variables of specimen 

orientation, specimen cross-section via throat width, and rate of 

stretch or "pulling-apartf are singly or jointly important. This 

involves a visual/descriptive review of the samples as well as 

the data collected. 

Step I: Procure a recyclable 2 liter green Sprite PETE 

bottle and label the x-axis that is parallel to the base of the 

PRECEDlNG PAGE BLANK NW FILMED 
bottle and follows around the froundness\ and the y-axis which 

is perpendicular to the base and which is coincident with the 

long axis of the bottle as shown in Appendix B - Figure B1. 

Step 11: Devise a way to obtain four 6.25 mm (114 in.) wide 

throat and four 12.5 mm (112 in.) wide throat samples so that 

half the 6.25 mm(114 in.) wide throat samples have their long 

axis parallel to the x-axis and half parallel to the y-axis as 

shown in Appendix B; Figure B1 - Bottle, Figure B2 - Bottle Sheet 

for 'layoutf and the specimen geometry in Figure B3 - Specimen. 

The ends of the bottle can be removed with a pair of scissors by 

first carefully piercing the bottle just below the expanded neck, 

cutting around the bottle, cutting along the long seam parallel 

to the long axis of the bottle, and cutting off the base just 6 

mm. (114 inch) above the base. Check the data sheet in Appendix 

C which designates the 6.25 mm (114 in.) wide throat samples 

with a uu-tt, and the 12.5 mm (112 in.) wide throat samples with a M+VU - and the long sample axis parallel to x-axis as tl-l\ and 

paralllel to y-axis as uu+lt. 

Once the layout is complete and the specimens have been 

locatec3, (see Figure B2), use the correct template set and clamp 

the plastic between the template plates. Secure the template set 

with C.-clamps. Next, with the utility knife gently scribe 

several times around the specimen until the template set with the 

plastic inside can be released from the bottle sheet. A template 

set can be made by contouring two 6.25 nun. (1/4 in.) thick steel 

plates to a 'dog-bonef shape following the American Society for 

Testing and Materials [4] specification Part 35 D638-80 type IV 

style, The type IV style will need to have a modified width for 

the 12.5 mm (1/2 in.) wide throat specimens. (Careful cutting 

could eliminate the use of the steel template set. However, 

extreme care must be exercised to avoid stray cuts into the 

throat area which can weaken the specimen.) 

Step 111: Label specimens as shown in Figure B3 to 

correspond with the run numbers in the Appendix C data table. 

Measure the thickness of each specimen in the vicinity of the 

middle of the throat area. Record the findings on the data sheet 

in the proper space. Check the variation in the thickness of the 

specimens. The thickness should be uniform across all specimens 

so that throat width is representative of specimen cross-section 

area. 

Step IV: Evaluation of the specimens under load can now 

begin. Be sure you are working with someone who is familiar with 

the operation of a tensile test machine in position control so 

that a stretch rate of 50 mm/min.(2 incheslmin.) can be set. Now 

run the first four specimens (numbers 1 -4) where the third 

factor, factor (c) , of stretch (deformation) rate has been 

assigned a I--" in the data table. As these tests are run it is 

important to record on the data sheet in the proper column && 

first maximum load reached by each specimen. The first maximum 
load reached is the highest load reading obtained usually within 

the first 12.5mm (half-inch) of deformation. Be sure to pl-ace 

the specimens in the tensile testing machine so that the numbers 

on the specimen ends are positioned the same way for each run so 

that after fracture the ends can be lined-up for comparison. 

After the first four specimens have been tested, change the 

deformation rate to 500 mm/min. (20 inches/ min.) needed for the 

"+" value for the third factor. Be sure to record the first 

maximum load reached by each of these last four specimens. (An 

enhancement of the experiment is to obtain a recording of load 

against deformation for each tested specimen. If a scaled and 

labeled graph of load against deformation has been made during 

the test for each sample the first maximum load can be read from 

the graph.) 

Step V-A: After the tensile tests are complete take a close 

look at the failed specimens. Align the specimens using the 

numbers on the bulb ends of each specimen (see Figure B3) and 

have all the top bulbs at the same level. The changes in 

elongation of each sample can be seen. Notice how the plastic 

"curled upf! The wide throat specimens curled more than the 

narrow throat specimens. What can be said about the rate of 

stretch? How does the idea of the faster the stretching, the 

more brittle type failure and the lower the elongation express 

your observations? Express what you have discovered via a sketch 

and words. 

Step V-B: Turn to the first maximum load held by each 

specimen recorded on the data sheet. A three factor, two level 

factorial Design Of Experiments procedure [5,6] is an efficient 

way to identify significant effects of the three factors of (a] 

specimen orientation, (b) cross-section area via throat width, 

and (c) stretch rate, and evaluate their interactions. The 

single, two, and three factor effect interactions can be assessed 

with the eight tests just completed. 

To illustrate the Yatesf Method a catapult intuitive clutcorne 

experiment influenced by three factors is shown in Appendix: D. 

The three factors are: (a) thickness of elastic, (b) type of 

binding post cross-section, and (c) load on the elastic. E:lastic 

stretch is measured to determine the impact of the three factor 

effects. Elastic thickness (a) and applied load (c) are found to 

be the major factors effects. There are no significant second 

and third order effects, and the cross-section of the binding 

post is unimportant. The same methodology is applied to the test 

results of the 2 liter, green PETE bottle with the three factor 

effects of: a) specimen orientation, b) cross-sectional area as 

given by the throat width and, c) rate of stretch, with your 

measurements of the first maximum load. 

COMMENTS ON FINDINGS : 

I. In the case of the green PETE bottle evaluated with the 
first maximum load; factor effects of specimen orientation and 

throat width were found to be significant based on a Yatesf 

Method analysis and a normal probability paper plot. Significant 

failure features seen from the specimens are: 1) all specimens 

curled about the load application axis, 2) the wide throat 

specimens curled less at the low stretch rate and wound up tight 

at the high stretch rate, 3) total specimen elongation in the xdirection was minimal in contrast to the elongation of 25 mm 

(one inch) or more in the y-direction, and 4) all of the fracture 

surfaces appeared to be fbrittlef with glass-like conchoidal 

features. 

11, For a series of specimens cut from a white, opaque, 

HDPE, 32 02. Ricotta cheese container evaluated with the first 

maximum load, the effects of specimen width and loading rate were 

found to be significant in contrast to the other effects. 

However when evaluated with specimen elongation at fracture, all 

first, second and third order factor effects based on specimen 

orientation, throat width, and stretch rate appeared not to be 

significant based on a Yatesf Method analysis and a normal 

probability paper plot. The specimens exhibited failure features 

as follows: 1) the specimens aligned with the x-axis tend to a) 

show necking and stringy fingers at the failure surface at the 

low stretch rate, and b) minimal necking with cleaner cleavage at 

the high stretch rate; 2) the samples oriented with the length of 

the container (y-axis) broke cleanly if the specimen elongated, 

and if the specimen did not elongate appreciably the fracture 

surface was fibrous. 

111. You now have the opportunity to collect different 

recyclable containers, make test specimens, run tests and compare 

findinlgs. Alternative methods to the Yatesf algorithm which 

address the Design of Experiments are found in Lochner (7) and 

Roy (8) , and may be of interest. Enjoy! 

1. Smith, William F., Principles of Materials Science and 

Engineering, 2nd edition, Mccraw- ill Publishing Company, N. Y. , N.V., 1990. 

2. Askeland, Donald R., The science and Engineering of 

Materials, 2nd edition, PWS-KENT Publishing Company, Boston, MA, 

1989. 

3. Callister, William D., Materials Science and Engineering, An 

~ntrod.uction, 2nd edition, John Wiley and Sons, Inc., N.Y., N.Y., 

1991. 

4. Amberican Society for Testing and Materials, Part 35, 

Plastilcs - General Test Methods; Nomenclature, D638-80 Standard 

Test Method for Tensile Properties of Plastics, American Society 

for Testing and Materials, Philadelphia, PA. 1981. 
5. Hogg, Robert V. and Ledolter, Johannes, Engineering 

Statistics, Macmillan Publishing Company, NY, NU, 1987. 

6. Miller, Irwin, and Freund, John E., Probability and 

Statistics for Engineers, 3rd edition, Prentice-Hall Inc. 

Englewood Cliffs, NJ, 1977. 

7. Lochner, Robert H., and Matar, Joseph H., Designing For 

Quality, American Society for Quality Control, ASQC Press, 

Milwaukee, WI, 1990. 

8. Roy, Rantit, A Primer on the Taguchi Methods, Competitive 

Manufacturing Series, Vannostrand Reinhold, NU, NY, 1990. 

APPENDIX A: Plastics Recycling Codes, Symbols, and Samples 

Code Symbol and material/ sample containers 

1 PETE polyethylene terephthalate 

carbonated beverages, cooking oil, peanut 

butter, boil in bag foods 

2 HDPE high-density polyethylene 

milk, juice and water jugs; trash cans, 

laundry detergents, auto oil, dishwasher 

soaps 

3 V or PVC polyvinyl chloride 

transparent bottles, cooking oil, mouth3wash, 

household cleaners 

4 LDPE low-density polyethylene 

plastic bags, garbage bags, sandwich bags, 

shrink wrap films, yogurt containers 

5 PP polypropylene 

food containers and lids, screw caps, tubs 

6 PS polystyrene 

brittle yogurt containers, sour cream, cottage 

cheese, table ware, plates, 'styrofoaml items 

7 OTHER multiresin and others not listed above: 

microwave packages, multilayer bottles 
APPENDIX 83: SPECIMEN PREPARATION 

Figure B3 Figure B2 

2-liter PETE 

bottk 

- 

W - width 25 mm (1 in.) Specimen 

OL - overall length 125 mm (5 in.) 

GL - gage length 25 mm (1 in.) 

T - throat: thin 6.25 mm (114 in.) wide 12.5 mm (112 in.) 

t - thickness 0.5 mm (0.02 in.) 
APPENDIX C: Specimen Data Sheet 

Specimen Type Team of Testers 

Source of specimens 

Place of Testing Date of Test 

Temperature of Test Facility ~umidity in Test Facilitv 

Factors1 

effects 

Run a b c 

Yatesf ~ethod~ 

First 

Thick- Max. 

ness load columns Factor 

in. lbs. (1) (2) (3) rank PP effect 

mean 

'Factor effects: 

(a) sample orientation: '-I means along x-axis 

I+' means along y-axis 

/L\ LL-- - 

~UI ~11ruat width: 6.25 mrn (114 in) is \--I 

12,50 mm (1/2 in) is \-kt 

Comments 

C: 

ac 

bc 

abc 

'see Appendix D for explanation 

(c) stretch rate: is for 50 mm/sec ( 2 in/min) 

\+' is for 500 rnm/sec (20 in/rninj 
APPENDIX P: Catapult Exercise 

Three factors impacting the operation of a catapult product 

delivery device are considered for a three factor, two level, 

factorial Design of Experiments exercise using Yatess Method. 

Tlrae three factors, each with two levels I--' and /++", are: factor 

(a) : same length elastic band widths (thin and wide), factor (b) : 

major support post cross-section (round and square), and factor 

[c): applied load (12 oz. and 24 oz.). A sketch of the catapult 

is shown in Figure Dl. 

Eight runs are made as delineated in data Table Dl, below. 

The elongation of the rubber band under load is measured. The 

factors are listed in Table Dl and the application of the Yatesf 

Method is explained below Table Dl. The column labeled rank is 

the seque!nce of column (3) ranked in order from high to low value 

while PP refers to plot position for the Normal Probability paper 

plot and is given by 100 times the ratio of rank minus one-half, 

divided by seven. The last column in the table relates the 

factor effect to the value in column (3). On Normal Probability 

paper you can see graphicallythat the first and second ranked items 

are outstanding in contrast to the others which plot about zero. 

This observation provides for the result that the effect of the 

elastic band width (a) and the load applied (c) are the 

significant factors in the experiment, while the other effects 

are not considered as significant. 

Measured Length-;-1 

Figure Dl Catapult 
Table Dl Data and Yatesf Method for Catapult 

F'actors' Yates'Alqorithm 

Measured 

Length columns2 Factor 

abc in. (1) (2 (3) rank ~~beffect 

1 - - - 5.375 17.375 36.375 100.00 - --- mean 

8+++ 20.000 7.750 0.625 -0.25 2 21.4 abc 

 actor effects: 

(a) elastic band width: means thin No. 19 elastic 

means wide No. 33 elastic 

(b) post cross-section: round post is 

square post is \+I 

(c) load: \-I means 12 oz. load applied \+' means 24 oz. load applied 

'F'rom the measured length column: 

add 5.375 to 12.000 to get 17.375, the 1st entry 

add 5.750 to 13.250 to get 19.000, the 2nd entry 

add 12.125 to 19.250 to get 31.375, the 3rd entry 

add 12.250 to 20.000 to get 32.250, the 4th entry 

subtract from 12.000, 5.375 to find 6.625, the 5th entry 

subtract from 13.250, 5.750 to find 7.500, the 6th entry 

subtract from 19.250, 12.125 to find 7.125, the 7th entry and 

subtract from 20.000, 12.250 to find 7.750, the 8th entry 

to complete column (1). Next, use column (1) as data and compute 

column (2). Repeat the process for column (3) with data in 

column (2). The column (3) values are used to assess the factor 

effects for this two level, three factor, factorial design. 

3~~ or Plot position for row 4 with the rank of 4 is 100 times 

rank minus one-half (4 - 0.5 = 3.5) divided by 7 to get 

50.0 percent. 
MECHANISM OF SLIP & TWINNING 

Department of Manufacturing Systems 

North Carolina A&T State University 

11 1 Price Hall 

Greensboro, North Carolina 27411 

Telephone 9 19-334-7555 

P@fiD!NQ PAGE 8Uf:K NOT FFLMED 

233 
Mechanism of Slip and g 

Mansur Rastani, Ph.d., P.E., C.Mfg.E. 

Dept of Manufacturing Systems 

NC A&T State University 

Kewords: deformation behavior of materials, mechanism of plastic 

deformation, slip bands, twin bands, ductile failure, intergranular fra~zture, 

shear failure, slip planes, crystal deformation, dislocations in ceramics. 

Prereauisite Knowledge: elementary knowledge of: metal structure, 

specimen preparation, measurement of mechanical properties of materials, 

examination of microstructure of a polished surface with a metallurgical 

microscope. 

Clbiectives: To demonstrate the mechanisms of deformation in bcc, fcc, and 

hcp-structure metals and alloys and in some ceramics as well. To exanline 

the deformed microstructures (slip lines and twin boundaries) in different 

grains of metallic and ceramic specimens. To study visually the deformed 

macrostructure (slip and twin bands) of metals and alloys. 

Backmound: Two of the most important mechanisms of plastic defamation 

are slip and twinning. Slip, which is the principal one, can be considered as a 

result of a distorted boundary, a line imperfection called dislocation, between 

two perfect regions of a space lattice, figure 1. Two types of dislocation 

segments are identified: edge dislocation, which causes axial strains in the 

space lattice, figure 2 ; and screw dislocation which causes the lattice to 

experience shear strains and to distort through a helical path, figure 3. The 

passage of a dislocation through a crystal results in the relative motioin of one 

part of the crystal past the other part; this process is called slip. Figure 4-a 

shows a slip resulting from the movement (right to left) of a pure edge 

dislocation, and figure 4-b shows a slip resulting from the movement (front to 

back) of a pure screw dislocation tlmough a simple cubic lattice. Slip occurs 

on the planes of the densest pack of atoms and in the direction of least distance 

between atoms. For example, in a face-centered-cubic (fcc) lattice, slip occurs 

on the four planes of ABC type, (111) planes, and in the direction of the 

diagonals of cube faces or the three sides of triangle ABC, <1i0> directions, 

figure 5. Slip planes and directions for some type of structures are shorn in 

table 1. In a monocrystalline specimen under axial loading, figure 6-a, if the 

slip plane is oriented parallel with or at a right angle to the axis of loading, 

figures 6-b and 6-c, the crystal will fail with no plastic deformation at all. 

When the orientation lies between the above two extreme cases, figure 6-4 

the fracture is preceded by an appreciable plastic deformation. The clolser in 

value the angle of slope of the slip plane is to 4507 the less load P is 

required to start the slip and the greater the plastic deformation is before the 
failure. In a polycrystalline specimen under axial loading, slip occurs first in 

grains whose slip planes are oriented at an angle of 45O with respect to the 

direction of applied force, while adjacent grains are affected by elastic 

deformation only. Surface examination of a deformed material under the 

optical microscope reveals a series of lines arising from steps on the surface 

called slip lines; this is shown in experiments number 1 and 2 for metallic 

and ceramic specimens. Also, these slip planes open up on the surface of the 

specimen as slip bands; this is shown in experiment number 3. The other 

mechanism of deformation is twinning. Twinning is the result of identical 

motions of atoms of a plurality of rows parallel to a twinning plane in the 

original lattice. The twin plane is a boundary which separates two 

orierltations that are mirror images of one another. In other words, twinning 

is folmed by a uniform shearing of atoms parallel to the twin boundary, 

figure 7. The strained part of the crystal becomes a mirror image of the zone 

free from twin crystals with respect to the twinning plane. VVhen the polished 

surface of such a material is subjected to etching , usually the regions on both 

sides of the twin boundary will be attacked differently because of a difference 

in the atomic configurations. Hence, viewed under a reflected-light 

microscope the surface will show dark and bright parallel regions (twin 

boundaries) within each grain. Similar to slip bands, twin bands could be 

viewed on the surface of the specimen. Examples of twin boundaries and 

bands are shown in experiments number 4 and 5. *inning occurs along 

with the slippage. The fraction of deformation by twinning is greater in 

hexagonal-lattice metals and in deformation occurring at great speed, as 

explosion stamping or extrusion. 

# 1: Slip hes in Metals 

Equipment: UTM, Metallurgical Microscope, Specimen Preparation Station, 

4 copper (fcc), one iron (bcc) 

PROCEDURE: 1) One side of the specimens of copper and iron is ground and 

polished. 2) Measure the hardness of one of the copper specimens. 

3) Examine the microstructures of the polished surfaces with a metallurgical 

micr~oscope. 4) Keep one of the specimens of copper in the UTM in such a way 

that the polished surface is not in contact with the grips and deform the 

specimen approximately 10 percent in compression. 5) One specimen of 

coppier is lightly etched and operation 4 is repeated to observe the change in 

deformed structures from grain to grain, figure 8.6) Fhpeat operations 4 and 

5 on iron specimen, figure 9. 7) The remaining two specimens of copper are 

defo~med 5 percent and 20 percent, respectively. 8) Examine the 

microstructures of the polished surfaces of the deformed specimens. 9) 

Measure hardness of copper specimens. Plot hardness vs percent 

defovmation for copper specimens, figure 10, and conclude why does hardness 

change as a function of percent deformation? 
Equipment: Reflected light microscope, Sodium Chloride crystal, anhydrous 

methyl alcohol, ether, blade 

PROCEDURE: 1) Cleave the sodium chloride crystal with a, single-edge razor 

blade. A slight press given to the blade placed on the crystal surface will 

bring about cleavage if the blade is properly oriented with respect to the 

cleavage planes. In sodium chloride these are (100). 2) Dip the crystal in 

anhydrous methyl alcohol and keep it there for a few seconds. 3) Take out the 

crystal, wash it in ether, and quickly dry it on a filter paper. 4) Put the 

specimen on a glass slide, mount the latter on the stage of the microscope and 

observe the etch pit patterns, figure 11. 

Equipment: Tensile specimen of mild steel, furnace, UTM 

PROCED~E:~) Select a tensile specimen of mild steel. 2) Fully anneal the 

specimen and then polish the surface. 3) Load it in tension at a rate of 0.05 

in/min. 4) Study the surface pattern just as the yield load is reached (Slip 

plane opens up on the surface as a band with an angle of 450 with respect to 

the load axis), figure 12. 

ecimen, reflected-light microscope, etching 

solution, specimen preparation station 

PROCEDURE: 1) The specimen is ground and polished to a mirror like su~rface. 

2) Wash the specimen thoroughly with water and dry it with alcohol. 

erse the specimen with polished surface upward in the etching 

solution for about 2 seconds. 4) Locate the specimen on the glass slide and 

mount the slide on the microscope stage and view it in the reflected light, 

figure 13. 

Equipment: A CPH-structure specimen such as zinc, specimen preparatjion 

station, UTM, reflected-light microscope. 

PROCEDURE: 1) Select a CPH-structure metal such as magnesium, titanium, 

or zinc. 2) Cut the specimen about 8-in long and obtain a metallograplhic 

polish on the surface. 3) Place the specimen in a tensile stress and slowl:y 

load it while viewing the surface reaction (Twin planes appear as broad 

lines). 

Table 1: Slip planes and slip directions 

for some type of structures 
b6erenws: 

1. 'I'. L. Anderson, Fracture Mechanics, CRC Press, 1991. 

2. D. A. Brandt, Metallurgy Fundamentals, Goodheart Willcox, 1985. 

3. M. Meyers, and K. Chawla, Mechanical Metallurgy, Prentice Wall, 1984. 

4. V. Masterov, Theory of Plastic Deformation, Mir Publishers, 1975. 

5. VY. 6. Moffatt, and G. W. Pearsall, The Structure and Properties of 

Materials, V.1, J. Wiley, 1964. 

6. AL. Nadai, Theory of Flow and Fracture of Solids, McGraw Hill, 1950. 

Figure 1. The lattice distortion at the boundary between 

two perfect regions in a slip. 

.f 

Compression 

Tension 

J. 

Figure 2. The regions of tension (light) and compression (dark) around 

an edge dislocation in a simple cubic lattice. 
Figure 3. (a) A simple cubic lattice before slip, (b) the lattice traces a 

helical path in a screw-dislocation slip. 

ti-i i i i i i i i LY' 

Figure 4. (a) Slip resulting from a pure edge dislocation, (b) Slip 

resulting from a pure screw dislocation. 
Figure 5. Slip planes and their directions in an fcc crystal lattice. 

Figure 6. Effect of orientation of slip plane upon character 

of deformation of monocrystals. 

Figure 7. The formation of a twin in a tetragonal lattice. 
Figure 8. Slip lines in a plastically deformed copper, 20OX. 

Figure 9. Slip lines in a plastically deformed iron, 300X. 
Figure 10. Variation of hardness vs deformation. 

Figure 11. Etch pit pattern (slip bands) in sodium chloride, 375 X. 
Figure 12. Slip band of a deformed mild steel that makes a 450 

angle with the tensile load axis. 

Figure 13. Twin boundaries as dark and bright regions within 

each grain in an a-brass specimen, 400X. 

243 
THE MICROSCOPIC WORLD: A DEMONST 

ELECTRON MICROSCOPY FOR YOUNGER STUDENTS 

Linda L. Hsrton 

Metals and Ceramics Division 

Oak Ridge National Laboratory 

Martin Marietta Energy Systems, Inc. 

P. 0. Box 2005 

Oak Ridge, Tennessee 37831 

Telephone 6 15-574-508 1 

"The submit?d mnuscript has hn 

authored by a contracts oE the V.S. Government unch contract No. DF- AC05-84QR21400. Accwdingly. the W.S. 

Govarnmnt retains B ~MTBX~IPS~V~. 

royalty-frw lii:%nse to publish w ~BP~OCIIPCB 

the published form of this contribution, or 

allow others to do so, for US. Government 

purposes.- 
TKE MICROSCOPIC WORLD: A DEMONS ON OF ELECTRON MICROSCOPY FOR 

YOUNGER STUDENTS 

L. L. Horton 

Metals and Ceramics Division, Oak Ridge National Laborato~y 

Oak Ridge, TN 3783 1-61 18 

KEU WORDS: Microscope, Scanning Electron Microscope, high magnification, scientific method 

PREREQUISIE KNOWLEDGE: This demonstration is specifically designed for elementary school 

students. The level can be easily adjusted for more advanced students with the same basic presentation. 

S: The purpose of this demonstration is to excite the students about the importance of 

scientific investigation and why they should look at the things in greater detail, extending beyond superficial 

examinations. 

EQUIPMENT AND SUPPLIES: The demonstration requires 35 mm slides of photograplls (micrographs) 

of various objects taken with a wide range of magnifications. In addition, a simple object, such as a 

baseball, needs to be prepared as an initial focus of what can be learned from looking at an object 

compared to what we can learn by taking it apart and looking at it at high magnifications. 

PROCEDURE: The focus of much of the demonstration is a slide show of electron micrographs of 

various things from the world around the students. In order to demonstrate the investigative nature of 

science, a baseball is used as an example. First, the baseball is described by the students as they see it and 

use it (color, texture, "bouncing", etc.) Then, the students are asked to examine a baseball that has been 

cut in half. Now, the students can see that the ball is composed of several different materj.als. 

After the above introduction, a slide presentation begins with high magnification micrographs of the various 

components of the baseball. Following the baseball micrographs, slides of other common items are shown 

and discussed relative to the function of the item. These range from butterflies and sequins to rsch and 

broken pencils. Figures 1 and 2 show examples of micrographs of a butterfly wing and a broken pencil. 

For older students, these simple concepts can be extended to a discussion of advanced ceramics, the 

materials used, for example, as space shuttle tiles and high temperature superconductors. The toughening 

of advanced ceramics is largely accomplished by the introduction of microscopic fibers and secondary 

phases. Micrographs show the scale of these reinforcing materials (compared to a human Jzair, for example, 

as shown in Figure 3). In addition, the importance of the atomic scale in the processing of modern 

materials is emphasized. 

The most important aspect of this demonstration is the narrative that accompanies the slides. 

Magnifications must be discussed in terms that the students can understand. For example, stating that the 

picture is a 400X magnification is not sufficient; the students can much better relate to "th.is is a picture of 

what a butterfly wing would look like if a 2 inch butterfly were enlarged to over 60 feet across!" It is 

equally important that items be photographed that are of interest to the students. The demonstration to be 

presented during the workshop is made-up of items gathered by a first grade class. 
Figure 1: 700 X scanning electron micrograph of a butterfly wing. At this enlargement, a 2 inch butterfly 

would be over 60 feet across. 

Figure 2: 20X scanning electron micrograph of a broken pencil. At this enlargement, a standard pencil 

would be over 5 inches wide. 

OHiGINAL PAGE 

 LAC^$ AKD WHITE PP(0TOGRAFt;H 
Figure 3: 2,000X scanning electron micrograph of a human hair with silicon carbide fibers deposited on it 

(small fibers are silicon carbide, large scale object is the hair). Silicon carbide fibers are used as 

reinforcements to make ceramics stronger. 

INSrnUCTOR NOTES: This demonstration is probably one that will need to be solicited from a facility 

with trained microscopists and access to scanning electron microscopes. The classroom teacher and thc 

scientist can "team" to ensure the appropriate level discussion of the material and re1evans;e of the objects 

presented relative to current classroom science curriculum. This approach provides the additional benefit 

of the involvement of a practicing scientist in the classroom. 

SOURCES OF SUPPLIES: For information about the availability of an ORNE speaker or about possiblc 

microscopists in your area, please contact Dr. Linda L. Worton, Building 4500S, MS 4118, Oak Ridge 

National Laboratory, P. O. Box 2008, Oak Ridge, TN 37831-6118, Telephone: (615) 574-5081. 

Acknowled~ement: Research sponsored by the Division of Materials Sciences, U.S. Department of Energy, 

under contract DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc. 
AN AUTOMATED SYSTEM FOR CREEP TESTING and 

FIVE EXPERIMENTS IN TERIALS SCIENCE FOR 

LESS THAN $10.00 

F. Xavier Spiegel 

Bemard J. Weigman 

Department of Electrical Engineering and Engineering Science 

Loyola College 

4501 North Charles Street 

Baltimore, Maryland 21210 

Telephone 410-617-25 15 
An Automated System for Creep Testing 

F. Xavier Spiegel and Bernard J. Weigman 

Loyola College, Baltimore, Maryland 

KEY WORDS 

Creep, Strain, Plastic Deformation, Potentiometer, A-D 

Converter, Automated Data Collection, Multiplex. 

A completely automated data collection system has been devised 

to measure, analyze and graph creep versus time using a PC, a 16 

channel multiplexed A-D converter and low friction potentiometers 

to measure length. The sampling rate for each experiment can be 

adjusted in the softwareto meet the needs of the material tested. 

Data is collected and stored on a diskette for permanent record and 

also for later data analysis on a different machine. 

INTRODUCTION 

Creep is the time dependent plastic deformation of a material 

under constant load or stress at elevated temperatures. For a 

given material, elevated temperature means at or above one half the 

absolute melting temperature. Structural materials typically creep 

at relatively high temperatures, rather large loads and typically 

over long periods of time. 1 

In this experiment 60140 solder (TinILead) is used because the 

solder will creep at room temperature, with small loads, and will 

break within a week. In fact in some specimens the solder will 

break within a day. This experiment requires that extension or 

strain be measured at regular time intervals until fracture, and 

lends itself to automated data collection. The following is a 

description of such a system. All the experiments were col~ducted 

on 60140 solder, .079 and .158 cm diameter wire, at room 

temperature. Initial length of the solder ranged from 10 cm to 100 

cm. Loads ranged from .250 to 2.00 kgme2 

EQUIPMENT MD SUPPLIES 

1. A ten turn precision potentiometer. 

2. Any PC/XT/AT IBM compatible computer with at 

least a 20 Mbyte hard disk. 

600,00 
3. A Data Translation DT2811 low cost Analog and 

Digital 1/0 board for IBM PC, PC XT and PC AT 

compatible computer systems (or the 

equivalent. The equivalent should have a 16 

channel multiplexer leading to a 12 bit A to D 

converter. The convert time is not critical. ) 

Source: Data Translation Inc., 100 Locke Dr. 

Marlboro, MA 01752-1192 tel. (508) 481-3700. 

795.00 

4. A 50 pin termination header 

Source: Industrial Computer Source, P.O. Box 

23058, San Diego, CA 92193 tel. (619) 279-0084 

part number 2M50FC. 

59.00 

AUTOmTED DATA COLLECTION SYSTEM 

.An automated data collection system was constructed using ten 

turn precision linear potentiometers as sensors (FIG.1), Data 

Translation DT2811 A to D converter board and a PC with 640K of 

memory and a 20 Mbyte hard disk (FIG.2). String was wrapped 

around the shaft of the ten turn precision linear potentiometer and 

connected to the weights at the end of the solder wire. Five volts 

were placed across the potentiometer. As the solder stretched, the 

potentiometer shaft rotated and the voltage at the wiper arm of the 

ten turn precision linear potentiometer changed. The change in the 

voltage for one centimeter stretch was measured in order to 

calibrate the ten turn precision linear potentiometer. This 

voltage was then measured with a 12 bit resolution A to D 

converter. The smallest voltage change that the ADC could measure 

was 2.44 millivolts corresponding to a smallest distance which 

could be measured of 0.037 cm. Any stretch of the wire greater 

than .037 em can be detected with the system. The stretch is 

related to the voltage measured by the ADC (1 volt = 15.27 cm). 

Thus, by measuring the voltage periodically with the ADC we kept a 

time history of the change in length of the solder wire. 

The DT2811 has 16 channels which are multiplexed to one 12 bit 

W to D converter. One channel from 0 to 15 is selected by software 

and R to D conversion is started again by software. A READY bit is 

checked in software and when the conversion is complete, the 

voltage at the wiper arm of the potentiometer is read as a 12 bit 

digital number. This number is recorded in a disk file along with 

the time that the reading was made. The program then selects the 

next channel and repeats the process until all channels are read 

for 'that time. This is repeated periodically until all of the 

solder wires break. The program is then terminated and the data in 

the disk file is analyzed. The time between readings varied, 

depending on how long it would take for the wire to break. For the 

thinner solder, readings were taken every 10 minutes.31 4r 5r 6' 
The data was analyzed using LOTUS 123. The raw data was 

imported into a LOTUS worksheet, scaled properly, converted to 

length and plotted all within LOTUS. No data was ever entered by 

hand, thus speeding up the operation and also avoiding transcribing 

errors. Data could also be conveniently archived on floppy disks 

in an easily accessed format. 

The conversion from volts to strain from a given sample is: 

6 = v/e, . 15.27 em/volt, where E = strain 

v = voltage reading in volts 

t, = original length, and 

15-27 cm/volt = conversion factor, 

The strain rate can be determined by calculating the slope of 

the strain vs. time graph. 

E = e2 - E~ / t2 - tlf where i = strain rate 

el = strain at time tl 

e2 = strain at time t2. 

Note that strain is dimensionless (sometimes reported as INPIN or 

cm/cm) and strain rate is in the dimensions of reciprocal time. 

Typical creep data is shown in graphs 1-4. Graph 1 is a plot 

of voltage vs. time and Graphs 2, 3, and 4 are plots of strain vs. 

time. strain rates taken from the slopes of Graphs 2, 3, anid 4 are 

0.003, 0,0047, and 0.0025 cm/cm.min. The data is reproducible and 

has alleviated the problem of continual observation while the 

experiment is in progress. The data is consistent with other 

observations of the same wire which were monitored every hour, but 

this automated system of monitoring has the added advantage of 

catching very closely the time of fracture, and the onset of creep. 

Since solder is wrapped in a spool the kinks are not easily removed 

and the onset of deformation is delayed while the wire is 

straightened, The wire could be pre-straightened, but the 

duplication of the straightening technique is questionable. Future 

experiments will include several techniques for straightening the 

wire before testing to determine their effect. 

ACKNOWLEDGEMENTS 

The authors would like to thank Mr. Howard Moore, Technical 

Assistant of the Physics Department at Loyola College, for his 

assistance in assembling the apparatus; and Miss Margaret Davis, 

student of the Engineering Department at Loyola College, for her 

assistance in conducting the experiments. We also wish to thank 

Mary Spiegel for typing this manuscript. 
REFERENCES 

Materials Science, Testinq, and Properties for Technicians, 

William 0. Fellers, Prentice-Hall. 

Fundamentals of Creep and Creep-Rupture in Metals, Frank 

Garofalo, Macmillan Series in Materials. 

- Interf acina, A Laboratory Approach Usinq the Microcomputer for 

Instrumentation, Data Analysis, and Control, Stephen E, 

Berenzo, Prentice-Hall 1990. 

The Industrial Computer Industrial Computer Source. 

Interfacins to the IBM Personal Computer, Lewis C. Eggebrecht, 

Howard W. Sams Inc. 

- User's Manual for DT2811. Low Cost Analoq and Diqital I10 

Board, Data Translation, Inc., 100 Locke Drive, Marlboro, MA 

01752-1192. 

- Computer Interfacinq - Rev. 5, 1989, B.J. Weigman. Loyola 

College, Baltimore, Maryland. 






FIVE EXPERIMENTS IN mTERIALS SCIENCE FOR LESS T $la>,OO 

F. Xavier Spiegel 

Loyola College, Baltimore, Maryland 

KEY WORDS 

Diffusion, Twinning, Fatigue, Acoustic Emission, Ageting. 

ABSTRACT 

Diffusion, Twinning, Fatigue, Acoustic Emission and Ageing 

can be studied using readily available materials and the h.ousehold 

oven. Each experiment can be expanded to a more extensive 

investigation of the properties of the material investigated, as 

well as other materials, and offers an opportunity for the student 

to learn about the relationship between engineering, science, 

society and politics. 

INTRODUCTION 

Simple experiments with everyday items can be used to 

familiarize students with the importance of materials and some of 

the properties which they possess. The following experiments have 

been performed by the author for over eight years with enthusiastic 

response by audiences of all ages. 

EQUIPMENT AE3D SUPPLIES 

1) Aluminum nails, 

2) United States Pennies, 

3) Metal Paper Clips. 

THE ALUMINUM NAIL 

Aluminum nails are age hardened to disperse the silicon and 

harden the aluminum. If an aluminum nail is re-heated to 600 F for 

one hour it will soften and can be bent by hand. This brief 

experiment demonstrates the movement of atoms in a material, This 

migration of atoms in a material is diffusion. In the age-hardened 

state the silicon atoms are finely dispersed, whereas in the reheated or over-aged material the silicon atoms coalesce into larger 

particles and no longer strengthen the aluminum to a useful 

hardened state.' 

THE UNITED STATES PEmP 

The U.S. penny has an interesting history; the pennies minted 

since 1982 are electroplated zinc. The present composition is 97,6% 
zinc and 2,4% copper. The copper can easily be scratched from the 

surface of the coin to reveal the zinc. Before 1982 the penny was 

35% copper and 5% zinc or 95% copper, 2,5% zinc and 2,5% tin, 

~xcept :for 1943 when the penny was zinc coated on steellO2r 31 4f 

Bn interesting experiment can be performed on all of the 

pen~lias except the 1943 version by placing them in an oven at 

350--400 F for about an hour or so. The surface of the penny will 

sequirle a heat tint that makes the coin appear golden. This heat 

tin-i can easily be removed by normal wear or by polishing, 

The pennies minted since 1982 exhibit another interesting 

2roperty when heat treated. If this penny is heated at 700 P for 

3ne hour the zinc grains will become large and can easily be 

twinned by biting on the penny or by bending it. An acoustic 

ernissiol~ will be heard when the penny is deformed. This experiment 

clearly demonstrates diffusion and grain growth, as the Bsas foundf8 

?enny will not twin because the grains are so small. Diffusion is 

causing the grain growth of the zinc and the deformation is causing 

the twinning. The twinning is causing the crackling noise heard 

1~~7herj the penwy is deformed. This crackling is called acoustic 

emission and is being extensively researched for NDE 

purpostes. 19.39415 

THE PAPER CLIP 

An ordinary metal paper clip can readily be used to 

4emo~st:rate fatigue. A fatigue failure arises from the cyclic 

laadirlg of a material at relatively small loads.' If a paper clip 

As opened so that it appears as an elongated BgSBt and is repeatedly 

ben.5 bzck and forth it will break, clearly demonstrating the 

-3he:neme:aon of fatigue, If the broken paper clip is quickly moved to 

zhe lower portion of the upper lip the paper clip appears warm, a 

result of internal friction, If the color of the region around the 

fracturro is examined a discoloration will be observed, and if the 

texture is observed the area around the fracture will be noticeably 

roughened, 

CONCLUSIONS 

As previously mentioned, these demonstrations have met with 

me5 si~1c:cess and the author" experience has been that many in the 

audj-ences have demonstrated them to others and frequently called 

the autlaor for more information or other experiments, Each of these 

experimc2nts can be expanded to be quantitative, and include other 

naterials, variation of heat treatments, different loading 

eechnlhq~~es and perhaps observations of different properties, It is 

rhe author" opinion that the equipment need not be complex and in 

fact should not be complex to interest students in the study of 

nateria ks, 
ACKNOWLEDGMENTS 

The author wishes to thank Miss Margaret Davis, engineering 

student at Loyola College, for duplicating these experiments and 

eomenting on their worth. I also wish to thank Mr, John Ross, 

friend and colleague, for his continued interest, advice a:nd moral 

support in my endeavor to understand metals. I also thank my wife 

Mary for typing this manuscript. 
REFERENCES 

11, William 0. Fellers, Materials Science, Testing, and Properties 

for Technicians, Prentice Hall 1990. 

2, Wagner, H.J., Hall, A.M., The New Coinage, Journal of Metals, 

March 1966, pp. 301-307. 

3. French, Charles F., 1991 American Guide to U.S. Coins, Simon 

& Schuster Inc., 1990. 

4. Junge, Ewald, World Coin Encyclopedia, William Morrow & 

Colrlpany Inc. , 1984. 

5. Yeoman, R. S., Current Coins of the World, 8th Edition, Western 

Pukalishing, Co. Inc., 1988. 
CTING AND RETAINING MINORITIES AND 

WOMEN IN TECHNICAL STUDIES 

Moderator - Heidi R. Ries, Norfolk State University 

Jonice Harris, National Institute of Standards 

and Technology 

Jenifer A. T. Taylor, NUS College of Ceramics at 

Alfred University 

Albert L. McHenry, Arizona State University 

Larry Mattix, Norfolk State University 
ATTRACTING AND RETAINING MINORITIES AND WOMEN IN TECHNICAL 

STUDIES: 

A Panel Discussion 

The underrepresentation of minorities and women in the 

fields of science and engineering is well-known, This fact, 

combined with current demographic trends toward increased 

minority percentages in the national population, indicates an 

impending shortage of technically-educated persons in the 

United States, Such a shortage would have a severe impact on 

our national ability to conduct research and development in 

technical fields. Therefore, in order to remain 

internationally competitive in science and engineering, it is 

imperative that increased numbers of minorities and women be 

attracted to, and retained in, technical studies, 

The purpose of this panel discussion is to explore 

possible solutions to the enrollment shortages of minorities 

and women in technical fields, while addressing the underlying 

barriers discouraging the recruitment and retention of these 

students. Currently functioning programs, such as the 

Dozoretz National Institute for Minorities in Applied Sciences 

at Norfolk State University and the educational development 

programs in the Southern Rocky Mountain region of the United 

States, will be highlighted. 
ATTRACTING AND RETAINING MINORITIES AND WOMEN IN TECHNICAL 

STUDIES: 

The Panelists 

Dr, Larry Mattix is Associate Professor of Physics and 

Director of the Dozoretz National Institute for Minorities in 

Applied Sciences at Norfolk State University in Norfolk, 

Virginia. He holds a BS in Physics from Clark-Atlanta 

University, anMS in Physics from the University of Illinois in 

Urbana, and a Ph.D. in Physics from the College of William and 

Mary, Williamsburg, VA. From 1981 through 1983, he was a 

National Research Council Post-Doctoral Fellow at the Naval 

Research Laboratory in Washington, DC. His current research 

interests include Sol-Gel preparations of ceramic materials 

including high temperature superconductors. He has directed 

the Dozoretz Institute, an honors program for science and 

engineering students, since its inception in 1986. 

Dr, Albert L. McHenry is Professor and Chair of the Department 

of Electronics and Computer Technology at Arizona State 

University, Tempe, Arizona. He holds a BS Industrial 

Technology from Southern University of Baton Rouge, Louisiana, 

an MS Technology and Ph.v. Technical Education from Arizona 

State, Dr. McHenry8s area of technical specialization is 

digital electronics. He has industrial experience with the 

Boeing Co., 3M Co., and Motorola. His current research 

interests include CAD for digital systems, implementation of 

CAI in technical subjects areas and Technology Education. Dr. 

McHenry has been actively involved in four-year technology 

programs for over 28 years and is a contributing member of 

ASEE, ETD, ETLI, and NAITTE. 

Dr, Jenifer Taylor graduated with a BS Degree in Ceramic 

Engineering in 1961 from the University of Washington in 

Seattle. She subsequently spent 20 years working with 

children; her own and other peoples', including teaching on 

several levels in public school both before and after earning 

an MS Degree in Education in 1974 from Alfred University. She 

returned to engineering, completing a Ph.D. in Ceramic 

Engineering in 1986 at Alfred University, where she has been 

employed since as faculty in the College of Ceramics. 

During that time her involvement with undergraduates has 

included serving as advisor for the student chapter of the 

Society of Women Engineers and teaching many classes. 

Observation of these students combined with her experience as 

an engineering student and as a mother of girls has led Dr. 

Taylor to a rather unique perspective on the problem of 

retaining women in technical studies. 
The Dozosetz National Institute for Minorities in Applied 

Sciences: Direct Intervention in Minority Retention. 

Larry Mattix, Norfolk State University 

After two decades of affirmative action, minorities 

have made little progress in gaining proportional 

representation in technical professions. In 31986 the 

Dozoretz National Institute for Minorities in Applied 

Sciences was established at Norfolk State University to 

address this problem. 

We believe that the sword which bars minorities from 

scientific and engineering careers is double-edged. First 

minority students do not get the information about the 

resources and opportunities available to them and simply do 

not believe that careers in science and engineering are 

attainable. Second, an exceedingly high attrition for 

minority students in science and engineers further redluees 

an already diminished pool of minority science students and 

leads to the increasing disparity in graduate and 

professional schools. Only 30% of minority students who 

start out in science and engineering graduate in those 

areas, This is less than half of the national rate for 

science and engineering students (70%). The Dozoretz 

Institute attacks these problems with emphasis on noncurricular issues like self-awareness, faculty-stuident 

interactions, mentoring, counseling, and summer experiences 

in science and engineering. 

The results after five years and two graduating cla.sses 

are promising. A retention rate of 68% (students who 

graduate in science and engineering) has been achieved. 

Ninety-three percent of the graduates have gone on to postgraduate studies in science, medicine, or engineering. 
RECRUITMENT PlrJD RETENTION OF MINORITY STUDENTS 

6 IN ENGINEERING TECHNOLOGY: 

WSTH SPECIAL EMPmGIG OF HIGPmICG WIEgD mERB@m INDIMS 

Albert L, MeHenry 

The initiation of special efforts to recruit and maintain 

minority students in the southern Rocky Mountain region is little 

more than a decade old. The region includes several major cities 

that represent minority population centers and other large 

minority populations associated with the American ~ndian reservations, mining towns, and rural farm communities. The minority 

students in these areas have been targeted for special academic 

development, 

The early development of minority recruitment programs was 

begun by motivated minority faculty members of universities and 

colleges. Their commitment led to the development of local chapters of minority professional organizations such as SHPE, AISES, 

and NSBE among others. These organizations grovide a self-help 

academic supportsystemforminorityengineering.engineering technology and science students. 

The philosophy and approach that has evolved is programmatic 

and dekrelopmental in nature. Engineering and engineering technology programs are academic areas that are at the focal point of 

the primary minority student developmental efforts. Programs 

such as PRIME, MEP, MESA, PROJECT 1000 and CIMD have become the 

established approach. 
Improving Retention of Women in Technical Studies 

Jenifer Taylor, College of Ceramics at Alfred University 

American culture is experienced differently by men and 

women. As a matter of fact, the male American culture is 

different in a number of ways from the female American 

culture. Many of these differences impact on how women feel 

about being in a technical curriculum. Educators in these 

fields, male and female, can help women feel more at ease if 

they are aware of these differences and can help all the 

students be more accepting. For example, when a woman cries 

when she gets a D on a test, it doesn- mean she isn't tough 

enough to be an engineer. It merely shows that our culture 

trains women to cry rather than swear, which is a typical male 

response to the same situation. Since men far outnumber women 

in the technical fields, the dominant culture is male. Making 

allowance for typical female behavior when it differs from 

male will increase retention of women. Simple strategies will 

be suggested. 
MATERIALS AND THE ENVIRONMENT 

Linda S. Farmer 

Manager Environmental Monitoring 

Westinghouse Environmental Management Company of Ohio 

P. 0. Box 398704 

Cincinnati, Ohio 45239-8704 

Telephone 5 13-738-6747 
AND HOW YOU CAN MAKE A D FFERENCE 

Linda S. Farmer 

Manager Environmental Monitoring 

Westinghouse Environmental Management 

Company of Ohio 

- T-E F\V 3O\V \P 
RONMENTAL CLEAN UP 

TAKES ... . 

GOVERNMENT INDUSTRY EDUCATION 

COMMUNITY MONEY AND ALL OF US 

WORKING TOGETHER 
GOVERNMENT 

STATE AND FEDERAL 

* ENVIRONMENTAL LAWS AND REGULNIONS 

* ENVIRONMENTAL PROGRAM AND [PROJECTS 

* ENVIRONMENTAL FUNDING 

* ENVIRONMENBAL EDUCATION 
nta 

RCRA 

SEPA 

CWA 

CAA 

OEPA DOE 

SDWA ARARs 

GER TEAM 
* ASSIST IN THE DEVELOPMENT OF STANDARDS 

* COMPLY WITH ESTABLISHED LAWS AND REGUL-ATIONS 

* TAKE THE ENVIRONMENT INTO CONSIDERATION 

WHEN DEVELOPING NEW PRODUCTS 

* PROMOTE CLEAN ENVIRONMENT TO EMPLOYEES 

AND IN PRODUCT ADVERTISEMENTS 

WHAT CAN THE 

EDUCAT ONAL COMMUN 

DO ...a 

RONMENTAL MATER ALS sc 

COURSES OF STUDY GEARED TOWARDS DEVELOPING 

ENVIRONMENTALLY MINDED MATERIALS EXPERTS 
- \K GLOBALLY 

ACT LOCALLY 
WHERE DOES THE 

MONEY COME FROM ... 

* UNIVERSITY GRANTS AND FUNDS 

* CORPORATION GRANTS AND FUNDS 

* GOVERNMENT GRANTS AND FUNDS 

* HISTORICALLY BLACK COLLEGES 

* WOMEN IN SCIENCE AND INDUSTRY 

* PRE-COLLEGE FUNDING 

* SCHOLARSHIPS 
WHAT VOU 

DO TODAY 

AFFECTS 

TOMORROW 
ALL 0- US B 

( 

* RE-DUCE WASTE * RE-CYCLE MATERIALS 

* RE-USABLE PRODUCTS * RE-MEDIME PROBLEM 14RIEAS 

TO HELP THE ENV RONMENT 
HSOTRBPIC THIN-WALLED PmSSURE 

VESSEL EXPERIMENT 

Nancy L. Denton 

Vernon S. Hillsman 

Purdue University 

School of Technology 

145 Knoy Hall 

West Lafayette, Indiana 47907 

Telephone 3 17-494-75 17 

289 PREOEIIIIVC; PAGE BLANK NOT FILMED 
ISOmOPIC TNIN-WALLED PRESS VESSEL EXPERIMEW 

Nancy L. Denton 

Vernon S. Hillsman 

Purdue University, West Lafayette, IN 

KEY WORDS: (thin-walled) pressure vessel, cylinder, principal stress, brass, 

Poisson's Ratio, Poisson effect, axial stress, combined loading, superposition, strain rosette, 

elastic material. 

PREREQUISITE KNOVVLEDGE: This material could be taught as presented to a 

materials science or mechanics student at the college level. The student should be familiar 

with the concepts of principal stresslstrain and the Poisson effect, which is an indication of 

the material strain transverse to applied load. Use of the linear regression function on a 

scientific calculator is expected. Previous exposure to thin walled pressure vessel theoffy is 

helpful, but not required. 

OBJECTn7ES: To investigate the stress and strain distributions on the surface of a 

thin walled cylinder subject to internal pressure and/or axial load. To relate stress and 

strain distributions to material properties and cylinder geometry. 

EOUIPMENT AND SUPIPLIES: 1) Brass tube of known Young's modulus and 

internal length, with pressure port and end treatment to facilitate internal pressure and 

axial loading, with strain rosette installed, as shown in Figure 1; 2) electromechanical test 

machine (ETM); 3) two digital strain indicators and switching unit; 4) load cell with greater 

than 9 kN capacity (minimum of 20 kN capacity recommended); 5) hydraulic pump with 

connections to tube and regulating valve, as shown in Figure 2; 6) hydraulic fluid; 7) 

pressure gage, preferably digital; 8) dial calipers; 9) scrap piece of same brass tubing, 

approximately 50 rnrn long; 10) calculator with linear regression capability. 

: Preparation: Set up hydraulic system and suspend brass tube with 

strain rosette in advance, leaving enough time to work air out of the hydraulic fluid (two 

days minimum), as shown in Figure 2. Present or review thin walled pressure vessel (PV) 

theory, including calculation and direction of hoop (circumferential) stress and longitudinal 

stress, and discuss assumptions needed for a PV to be considered thin walled. (If 

necessary, review axial stress). Review equations for calculation of principal strain from 

strain gage rosette data and conversion of principal strain to principal stress. Tell students 

the Young's modulus and internal length of the tube and the bulk modulus of elasticity of 

the hydraulic fluid. 

Experiment: Students begin by calibrating the load cell and one strain indiicator to 

read load in kiloNewtons. Next, they will complete and calibrate the strain gage rosette 

circuitry as shown in Figure 2 to permit reading of each of the three strains in units of 

microstrain for each loading. A quarter Wheatstone bridge will be used. To start the test, 

students should verify that the brass PV is affixed at top and bottom to the ETM, then 

apply a tensile axial load in increments of 4 kN up to a maximum of 16 I&. At eaich 

increment, the load and three strains will be recorded. Following the 16 kN measurements, 

all axial load must be removed. The students will next apply internal pressure in 

increments of 0.7 MPa up to a maximum pressure of 2.8 MPa, and obtain pressure and 

strain readings at each increment. Again, the loading should be removed. For the final 

loading variation, the students will apply an internal pressure of 2.8 MPa, then apply tensile 

axial load in increments of 4 kN up to 12 k;N. At each increment, the axial load, strains, 

AND pressure readings are recorded. As axial loading increases, the instructor should 
point out two significant phenomena. The more obvious of these is that the principal 

direction (changes from hoop (horizontal) to longitudinal (vertical). A second, subtle 

obsesvation is that the elongation of the tube from the axial loading actually reduces the 

internal pressure of the tube by increasing the tube's volume. The students next remove all 

loading and disconnect all wiring. The scrap of tube is then measured to obtain internal 

diameter, external diameter, and wall thickness. (All should be measured at several 

locations to establish the range of actual values). 

Data Reduction: Theoretical values required include Poisson's Ratio for the brass, 

and principal stresses and/or strains for each loading condition. (Principal directions will 

be assumed to be vertical and horizontal). The brass material properties and bulk modulus 

of elastici~ of the hydraulic fluid should be provided by the instructor or obtained from 

standard lnaterial references. The principal stresses should be calculated from equations 

for axial stress, hoop and longitudinal stress, and their combination. (Equations and 

spbols are listed in Appendix A). 

Extensive calculations are needed from the measured strains. For all loadings, 

principal ,strains must be calculated from the measured strain values. This requires initial 

calculation of shear strains. Principal strains can then be determined directly, using a 

reference axis through gage one of the rosette, or the measured strains can first be 

transformed to vertical and horizontal positions, then principal strains found. (Hopefully 

the transformed strains and principal strains will agree!) At least one principal direction 

per Iloadi~ng type should be determined to confirm that vertical and horizontal are indeed 

the principal directions. 

Using principal strains from the tensile axial load only, an empirical Poisson's Ratio 

may be obtained by performing a linear regression of the minimum and maximum principal 

strains. The resulting slope is the empirical ratio desired. This should be cornpared to the 

theoretical Poisson's Ratio for verification. The ernpirical value should be used for all 

remai~ng calculations. 

Next, all principal strains must be converted to principal stresses, using the 

theoretical Young's modulus and the empirical Poisson's Ratio. At least one pair of 

principal stresses per loading should be compared to theoretical values for verification. A 

linear regression of maximum principal stress and pressure from the pressure only loading 

can be performed to determine an equation relating hoop stress and internal pressure. 

When the theoretical hoop stress is substituted into this equation, an empirical value for 

wall thichess is obtained, which can be compared to the measured thickness. 

Far the combined pressure and axial loading, calculate the change in pressure due 

to the change in volume caused by the axial load. Compare calculated pressure change to 

measured pressure change. Note that the theoretical calculations for principal stresses for 

the combined load case assumed zero pressure drop; superposition assumes that the strains 

or stresses from the acting loads are additive, so this should allow discussion of the 

accerraq of the assumption used for the theoretical calculations. A second theoretical 

calculation of the principal stresses for the combined loading case could be completed 

based on the anticipated pressure drop due to the increase in volume. 

SdMPLE DA'HIA SHEETS: Self-evident. 

IBISTRUGTOER NOTES: This experiment was designed for students enrolled in an 

advanced strength of materials course. For additional study, a filament-wound composite 

cylinder could be included to investigate the effect of wind angle on stress/strain. 

Modeling of the vessels prior to testing could also be incorporated. 

Conversely, the experiment could be modified to be conducted as a demonstration 

for begin~ng materials or strength of materials students. Additional study could include 

on pol~nylchoride piping. To simplify the experiment and its data reduction, a two 

gage rectangular strain rosette should be mounted along principal directions (vertical and 

horizontal), thus eliminating all principal strain and direction calculations. 
Since published values for the bulk modulus of elasticity are difficult to find in 

standard reference material, and will vary widely if air is trapped in the fluid, it is advisable 

that the lab instructor should experimentally determine the bulk modulus prior to the lab 

experiment. 

WARNING: Before conductin the experiment, test the PV at maximum loadings 

to confirm that the joints are sufficient f; y strong. Use of plastic sheeting or other means 

to catch any potential leaking hydraulic fluid is advisable. 

REFERENCES: Beer, F. P., & Johnston, E. R. Jr. (1981). Mechanics of Materials. 

New York: McGraw-Hill Book Company, (pp. 62-70,293-926,325-342). Beckwith, T. G., 

Buck, N. L., & Marangoni, R. D. (1987). Mechanical Measurements (3rd ed.). Reading, 

MA: Addison-Wesley Publishing Company, (pp. 353-373). Fox & McDonald (1978) 

Introduction to Fluid Mechanics (2nd ed) New York, NY: Wiley & Sons, Inc. (pp. 610) 

Murdock, James W. PE (1976) Fluid Mechanics and its Applications USA: Houghton Mifflin Company (pp. 29-31) 

SOURCES OF SUPPLIES: Brass tubing and caps - any metal distributor. Strain 

gages and rosettes can be obtained at substantially reduced cost for educational purposes from Measurements Group, P.O. Box 27777, Raleigh, NC, 27611, (919) 355-3800. New 

pumps can cost several hundred dollars, so investigate local industry and/or scrap dealers 

as potential sources (our pump was part of scrapped airplane landing gear). Hydraulic 

system (tubing, pressure ports, pressure valve) can be purchased from any local plumbing 

supply store. 

ACKNOWLEDGEMENT: The thin walled pressure vessel experiment would not 

exist without the initial development work of George Stinchcombe, former Visiting Professor and current engineer with British Aerospace Corporation, and Jim Osborne, 

laboratory technician. Their efforts are greatly appreciated. 
APPENDIX A: SYMBOL LIST (in order of appearance on Equation List) 

t = wall thickness of tube 

d = internal diameter 

p = internal pressure 

= hoop (circumferential) stress 

OL = longitudinal stress 

OR = ratdial stress 

uA = axial stress 

IF = axial load 

A = cross-sectional area (of tube) 

c I, c2, ~3 = strain gage rosette data 

c,, xy = normal strains along X&Y reference axes (X-axis through gage 1; Y-axis through 

gage 3) 

yq = shear strain with respect to X & U reference axes 

c, and c,;, = principal strains 

7 ma = max shearing strain 

o p = principal direction(s) 

p = Poisson's Ratio 

I3 = Young's Modulus 

a/ = internal volume of the tube 

L = internal length of the tube 

B = bulk modulus of elasticity (for hydraulic fluid) 

c~_l = hoop strain 

EL = longitudinal strain 
EQUATION LIST (in order of appearance in the text) 

1. Thin PV: If t 5 

d 

m 

Pressure-Induced u H = pd 

2iStresses: 

OR = 0 (zero) 

F 

2. Axial Stress UA = A 

3. Principal Strains from Rectangular Strain Gage Rosette Data 

- 

Cx + Cy 7 max 

Emax - +- 

2 2 (34 

4. Principal Directions with respect to reference axes on rosette 
EQUATION I.JST (in order of appearance in the text) CONTINUED 

5. Poisson Ratio (for Uniaxial Stress only) 

6. Principal Stress from Principal Strain 

7. Pressure Change Due to Volume Change 
holding fixture analog pressure gage 

(0 - 10 Mpa) 

/ 

hydraulic 

re turn 

strain gage rosette 

(see detail below) 

welded 

end caps 

- Thin-walled brass cylinder 

holding fixture -* 

Figure l.(a) Thin-walled brass pressure vessel 

Figure l.(b) Orientation of 45 degree strain gage rosette 
reservoir 

universal test 

Figure 2. Schematic of test equipment 
STRESS-STRAIN C CTERISTICS OF RUBBER-LIKE 

MATEIHALS: EXPERWENT AND ANALYSIS 

David J. Allen 

School of Engineering Technology 

Northeastern University 

120 Snell Engineering Center 

Boston, Massachusetts 02115 

Telephone 6 17-437-2500 
STRESS-STRAIN CHAJXACTERISTICS OF RUBBER-LIKE MATERIALS: 

EXPERIMENT AND ANALYSIS 

David J. Allen 

School of Engineering Technology 

Northeastern University, Boston, Massachusetts 

KEY WORDS: rubber, neoprene, stress, strain, elasticity, 

tensile test, power equation. 

PREREQUISITE KEJOWLEDGE: The student should understand 

the concepts of stress and strain either previously or 

concurrently presented with experiment. 

OBJECTIVES: To demonstrated tensile testing of materials 

and the application of the concepts of stress and strain. To 

introduce a method of analysis of curvilinear data which will 

yield a mathematical relationship between stress and strain 

for many artificial rubbers and plastics. 

EQUIPMENT AND SUPPLIES: (1) No. 32 or No. 64 rubber 

(neoprene) bands; (2) Two S hooks approximately 5 cm long; (3) 

One screw eye; (4) Lumber as required; (5) mm scale; (6) 

micrometer; (7) Calibrated weights; (8) Log-log paper; (9) 

calculator. 

PROCEDURE: The students may either design their own 

testing apparatus or make one similar to the one shown in 

figure 1. If they design their own, design factors such as 

the amount of space required should be discussed, 

Students make a pair of gage marks near the middles of 

each side of a rubber band and measure the length between each 

pair of marks. These measurements are the initial unstrainied 

length, Lo. The thickness and width at each gage section is 

also made which will yield the initial cross sectional are.a, 

Ao. TWO sets of data are made from each test. 

The test is conducted by placing the specimen in the 

testing apparatus and adding incrementally calibrated weights, 

The length between the gage marks are'measured for each load, 

Optionally, the thickness and the width of the rubber band may 

be measured at each loading. The test is conducted to failure, 

Once the data is collected the students begin their 

analysis. The engineering stress may be computed from 

where a is the engineering stress and P is the load on the 

section. It is important not to forget that P is one half of 

the applied load since there are two sides of the rubber band. 

If the actual thickness, tACTUAL, and width, wACTUAL, are measured 

for each loading, the true stress can be determined from 

301 

PRECEDING PAGE BLAFiK PJOT FILMED 
where the actual cross sectional area is 

Strain is computed from 

where AL is the change in length from the original undeformed 

lengtlh to the one being computed. 

SCRNII EYE 

RUBBER BAND 

GAGE LENGTH 

S HOOK 

WEIGHTS 

I 1 

Figure 1 

'The stress and strain values are plotted on an arithmetic 

graph and a smoothed best fit curve is drawn. Typical results 

are shown in figure 2. Note that the curve is nonlinear. 

It would be useful to obtain a mathematical relationship 

between stress and strain but one is not readily apparent from 

figure 2. However, if the data are plotted on a log-log plot 

as shown in figure 3, the best-fit curve is obviously a 

straight line. 

The equation of a straight line takes the form of 

but since the graph is log-log the equation needs to be 

modified to 

lny=m-lnx+ lnb 

(6) 

or in terms of the stress-strain relationship 

lna =m.lne+lnb (7) 

which only leaves the determination of parameters m and b once 

the best-fit line is drawn. 

The slope, m, of the curve can be determined by choosing 

two arbitrary coordinates on the best-fit curve, say (€,,a,) 

and (~,,a,). The slope can now be defined as 

Once the parameter m has been computed from equation 8 

the parameter b can be determined. Reorganizing equation 7 

results in 

lnb= lna -m.lne 

(9 1 

Subskituting the arbitrary coordinates, (~,,a,) and into equation 9 allows b to be computed from 

lnb = Inax-malne, = ha,-m-lne, (10) 

The value of lnb can be evaluated two different ways in 

eqhlation 10. This gives a check of the computations. Utilizing 

the Laws of logarithms equation 7 can be written as 

lna =lnem+lnb (11) 

This is the form called the power equation. Data whose plots 
show a straight line best-fit relationship on log-log graphs 

can be represented mathematically by equation 13. Using the 

above method on the data shown in figure 3 yields 

Many materials and systems will follow a power equation and it 

is worthwhile to make a log-log plot of data points following 

a curvilinear trend on an arithmetic plot. Allen and Phalen2 

extend this approach to the artificial rubbers used in singleply roof systems. 

For a more thorough treatment true stress utilizing 

equation 2 versus strain may be analyzed. Arithmetic and loglog plots and the corresponding best-fit curves and equations 

for true stress vs. strain are compared with the engineering 

stress analysis given above. 

SELE%PLE DATA SWEETS: Self-Evident. 

INSTRUCTOR NOTES: Having the students design and build 

their own testing apparatus is a good project. The student8s 

interest and creativity is harnessed which results in a better 

appreciation of experimentation. A thorough discussion of 

factors involved in experimental design should be made without 

dampening the student" creativity. One student used rolls of 

pennies as weights and obtained good results. Ideas should be 

encouraged even though they may lead to unsatisfactory 

results. This provides a fertile ground for discussion. 

Some computer graphing and statistical programs provide 

linear regression analysis. They may use the tern vfgeometricBg 

equation rather than "powerm equation. Even if computer 

programs are available it is recommended that the student do 

the graphing and analysis by hand computations to reinforce 

the concepts introduced. The computer can be used as a check. 

This experiment also gives the students a better 

understanding and a physical "feel" of the concepts of stress 

and strain than that obtained by using a steel specimen in a 

testing machine. The large strains and applied loads are 

readily apparent. 

REFERENCES: 

(1) Giesecke, F.E., et.al., Engineering Graphics, Third 

ed., 1981, New York 

(2) Allen, D.J., and T.E. Phalen Jr.,"Stress-Strain 

Characteristics for EPDM, CSPE, and PVC for the 

Development of Stresses in Membranes Utilized as 

Single-Ply Roof Systems"",rroeeding of the 1991 

International Symposium on Roofing Technology, 1991 

SOURCES OF SUPPLY: A well stocked hardware store or home 

center can supply the materials needed for the testing 

apparatus. 
DEMONST TION OF GNETIC DOMAIN 

BOUNDARY MOVEMENT USING AN EASILY 

ASSEMBLED VIDEOCAM-MICROSCOPE SYSTEM 

John W. Patterson 

Materials Science and Engineering Department 

Iowa State University 

110 Engineering Annex 

Ames, Iowa 50011 

Telephone 5 15-294-7562 
DEMONSTRATION OF MAGNETIC DOMAIN BOUNDARY MOVEMENT 

USING AN EASILY ASSEMBLED VIDEOCAM-MICROSCOPE SYSTEM 

John W. Patterson 

Department of Materials Science and Engineering 

Iowa State University 

Ames, IA 50011 

KEY WORDS: magnetic domains, domain boundary migration, videocam microscope, 

PREREQUISITE KNOWLEDGE: Familiarity with the proper care and use of ordinary 

video equipment and such optical lenses as are found on video cameras and 

standard optical microscopes. The main concern here is to prevent damage to 

the microcsope objective lens, the videocam, and to the connectors for the 

video camera, the tv monitor or the vcr equipment used in this demonstration. 

OBJECTIVES To build and demonstrate a low cost and highly flexible t:v 

microscope facility and then use it to view the motion of magnetic domain 

boundaries as the local magnetic field is varied. The expense of an optical 

microscope and the videocam adapters sold for them is largely avoided by using 

the facility described below. 

EOUIPMENT AND SUPPLIES 

1. An inexpensive home video camera with a manually operated zoom ca.pability 

The type used by most athletic departments for making game and scrimmage 

tapes should do fine. In many high schools, colleges and universities, 

videocams are available on a checkout basis from a media resources 

department. 

2. A 10-power, 0.25 numerical aperture objective lens such as can be found on 

the optical microscopes in biology or metallographic preparation labs, 

However, new ones can be purchased from optical dealers such as Bausch and 

Lornb, Edmund's Scientific and others for about $35 to $50. 

3. A 1 rnm x 1 mm x 0.1 mm sample of magnetic bubble material (ferrimagnetic 

garnet "FMG" crystal) such as can be found in the 1991 Cenco or TEL-Atomic 

science supplies catalog for around $145.00. The specimen comes already 

mounted at the center of a brass disk for ease of handling. It is also 

convenient for attaching it to the end of a mailing-tube holder as 

described below. 

4. A small, adjustable beam flashlight (commonly called a mag-lite) for 

illuminating the sample from behind. This item can be purchased for a few 

dollars in most hardware and discount stores. 

5. A mailing-tube such as the plastic ones used to package the disposable 40ce 

syringes used by livestock veterinarians. Vets view these as throwaway 

packaging materials, which makes it easy to a obtain free supply. 
PROCEDURE: The procedure for setting up this simple but effective tv microscope fac!ility has been demonstrated nicely in an informal videotape 

produced by Dr. Dale Stille, at the University of Iowa, who originated the 

idea, The procedure outlined here was taken from Stille's videotape. He 

uses an optical bench to reduce vibration and ease positioning, but it is 

not essential. Kindly refer to Figure I. 

I, Mount the video camera on a suitable tripod, turn it on, advance the zoom 

setting to its maximum, and place it on the lab or lecture bench with the 

line of sight horizontal and about chest high. 

2. Affix the brass specimen holder to the end of the throwaway plastic tube 

and position this so that the specimen is about a foot or so from the 

videocam and directly in the line of sight. Of course the axis of the 

tube should be colinear with the line of sight of the videocam. 

3, Now mount the microscope objective lens on an appropriate stand and 

interpose it between the videocam lens and the specimen. Make sure its 

axis is colinear with the other two and that the threaded end of the 

objective is just brushing the lens of the videocam. Don't worry about the 

light that may enter the videocam lens without going through the objective. 

Attempts to block it, as with a bellows or similar arrangement, will likely 

do more harm than good. The image quality without bellows is very good. 

4, Switch on the mag-lite and lay it inside the specimen-holder tube so that 

it shines on the back of the brass specimen-holder and through the tiny FMG 

crystal, 

5. Now, gently move the specimen-holder tube toward the video camera until 

the specimen virtually touches the lens of the microscope objective. Be 

careful here; the objective is grazing the videocam lens to the rear while its 

own lens is within 1.0 mm or so of the FMG crystal specimen, so there is 

danger of damaging a lens. 

6. Everything is now ready. Peer through the viewfinder of the videocam and 

back off on the zoom to bring the specimen into sharp focus-- manual focus 

of the videocam may also help. The tiny specimen should be well 

illuminxted and should fill the entire field of view (and tv screen). 

7. To induce domain boundary migration, bring the north or south pole of a 

permanent magnet close to the specimen and watch what happens. You will 

soon discover how to achieve the best effects for your purposes. 

8. At this point you can tape a lecture demonstration for a later showing, or 

you can connect the videocam directly to a tv monitor and show the effects 

in real time as you describe what's going on. 

NOTES TO THE INSTRUCTOR 

A wide variety of quantitative experiments and demonstrations can be performed 

using the apparatus described above. The emphasis here, however, is more on 

the facility itself than on the experiments made possible once it is assembled. 
It should be noted, however, that the TEL-Atomics FMG crystals come with a coil 

located in the brass mount. When connected to a dry-cell or a 0-6v dc power 

supply, one can vary the coil current and hence the magnetizing field strength, 

H, in a controlled fashion. The number of non-oriented domains decreases 

with H, as can be observed on the tv screen, and at saturation only a single 

domain will be seen and it will be oriented with H. To plot magnetization M vs 

H curves, hysteresis loops and the like, a way must be found to monitor and 

plot M. The references by ~annerlr and Nielson3 should prove helpful 

in this regard. 

Specimens demonstrating other physical phenomena can be used in place of the 

FMG crystal. Brownian motion cells and liquid crystal specimens are two that 

come to mind but I am certain many readers will think up several of their own. 

A most intriguing-- but not yet tested-- possibilty is to use observations on 

liquid crystal specimens to simulate "phase transitions" in polymeric materials 

and even in the early stages of cosmology. For a recent article on the 

colmology angle, see the reference by Ivars peterson4. 

One final note. Some instructors prepare several holder-tubes, each with its 

own specimen and microscope objective already fixed in the proper positions 

inside. Each can be mounted as a self-contained unit, which saves alignment 

and adjustment time before each demonstration, but this means objective lenses 

remain tied up. 

ACKNOWLEDGMENTS 

It is a pleasure to acknowledge Dale Stille (rhymes with Billy), who is the 

Lecture Demonstration Coordinator for the Physics Department of the University 

of Iowa in Iowa City, Iowa 52242. Dale originated the procedures described 

above and kindly provided many helpful comments during preparation of this 

manuscript. Mr. Erv Poduska of Kirkwood Community College presented Stille's 

videotaped demonstration at the Spring 1991 meeting of the Iowa Academy of 

Science, which is what piqued my interest. 

REFERENCES 

1. B. K. Tanner et al, Physics Education ll, 356 (1976) 

2. B. K. Tanner, American Journal of Physics 48, 59 (1980) 

3. J. W. Nielson, IEEE Trans. on Magnetics MAG-12 4, 327 (1976) 

4. I. Peterson, "Cracks in the Cosmos," Science News 139, 344 [June 11 (1991) 
video cam 

Figure 1 
AN EXPERIMENT ON THE USE OF DISPOSABLE 

PLASTICS AS A REINFORCEMENT IN 

CONCRETE BEAMS 

Mostafiz R. Chowdhury 

Construction Management Department 

East Carolina University 

325 Raw1 

Greenville, North Carolina 27858 

Telephone 9 19-757-6707 
AN EXPERIMENT ON THE USE OF DISPOSABLE PLASTICS AS A 

REINFORCEMENT IN CONCRETE BEAMS 

Mostafiz R. Chowdhury, Ph.D., PE 

Assistant Professor, Construction Management Department 

East Carolina University, Greenville, North Carolina 

Kev Words: Disposable Plastics, Restressed Concrete Beam, Class Project, Computer 

Simulation 

SUMMARY 

This paper will illustrate the concept of reinforced concrete structures by the use of 

computer simulation and an inexpensive hands-on design experiment. The students in our 

Construction Management program use disposable plastics as a reinforcement to 

demonstrate their understanding of reinforced concrete and prestressed concrete beams. 

The plastics used for such an experiment vary from plastic bottles to steel reinforce:d auto 

tires. This experiment will show the extent to which plastic reinforcement increases the 

strength of a concrete beam. The procedure of using such throw-away plastics in an 

experiment to explain the interaction between the reinforcement material and concrete, and a 

comparison of the test results for using different types of waste plastics will also be 

presented in this paper. 

A computer analysis to simulate the structural response is used to compare the test 

results and to understand the analytical background of reinforced concrete design. This 

interaction of using computers to analyze structures and to relate the output results with real 

experimentation is found to be a very useful method for teaching a math-based analytical 

subject to our non-engineering students. 

OBJECTIVES 

This project was assigned to the students to achieve the following objectives: 

i> To develop a basic concept in designing, preparing, and testing concrete 

structures 

ii) to understand the role of reinforcement in reinforced concrete structures 

iii) to relate computer simulation with the actual structural response to applied 

loads 

iv) to experience prestress concrete technology 
v) to familiarize students with a systematic step by step procedure for 

executing and completing research 

vi) to involve students with a growing national concern for disposing plastic 

wastes by the use of an innovative recycling method. 

INTRODUCTION 

The Building System Design class is a three semester hour comprehensive structural 

design and analysis course. This course is designed to illustrate the concepts of structures 

and their fundamentals by using computer analyses and physical demonstrations of model 

stmctulres. The students in this class apply their understanding of structural analysis in 

designing, building, and testing model structures in practical experiments. In this class 

practic;al design problems are included to develop a general concept for different structural 

systems. The first two-thirds of the semester is devoted to explaining the force-response 

relationships of structures. A broad spectrum of structures and their interactions with loads 

are explained. A structural analysis computer program is used to analyze structural 

systems. At the end of this period the students are required to form groups to study a 

pmicu1x type of structure. Each of the groups works under the supervision of the 

instructor and presents its findings in an open forum. This study discusses a concrete 

project and presents its findings. 

Concrete is a very widely used construction material. As a material, concrete is 

stronger in compression and much weaker in tension. A material course in this respect can 

reach students about the general behavior of concrete and the practical aspects of its 

applications. A reinforced concrete design and analysis class could generally teach the 

imponilnce of the reinforcement in a concrete structure and how many rebars are required to 

provide the additional tensile strength in the concrete. Apart from these courses a concrete 

laboratory session would substantially enhance the basic understanding of concrete and its 

charac1:eristics. For construction majors, however, a laboratory session is more important. 

In our Building System Design class we have introduced a concrete project to understand 

concrete as a material and the practical aspects of its placement, testing, and preparation. 

This paper will demonstrate the extent to which disposable plastic reinforcement 

interacts with concrete and increases the tensile strength of concrete beams. Computer 

analysis is performed to analyze the structure and relate the results with actual structural 

response to applied loads. The use of such an inexpensive and abundant resource also 

acquaints students with a national growing concern for managing plastic wastes. 

The project was also designed to outline a systematic methodology to conduct and 

involve students in a research program. The final student project reports describing the 

limitations and recommendations for future study are also discussed. 

PROCEDURE 

The Building System Design class was divided into groups, consisting of two to four 

students each, to work on different projects. Each group was responsible for planning, 

managing, and executing the project in a systematic manner in order to complete the project 

on rime and achieve its objective. As a guideline to help plan their project they were asked 

to follow the six step schedule. These activities included: 
i) selection of group members 

ii) consulting previous projects and literature survey to find any related wori~s 

iii) submission of a proposal - basic preparation to complete the project - 

determining the objectives, highlighting the actions to be performed 

iv) execution of the project - determining number, size and shape of beams and 

cylinders to be prepared, preparing forms, concrete casting and slump testing 

v) testing and analysis of concrete specimens 

vi) summarizing the work done 

The students were also given the following information. 

A review of concrete structures and how they behave under the application of 1o;sds 

was provided by solving simple example problems. At this point the student had a basic 

understanding of flexural stress which results due to a bending moment induced by an 

applied load. The role of reinforcement was described by studying the computer analysis of 

an example problem. In this problem the flexural stresses due to an applied load on a 

simply supported non-reinforced concrete beam were computed for a symmetric crosssectional beam. The computed stresses due to an increment of load at regular intervals were 

monitored and compared with the flexural tensile strength of concrete. An attainmenl of the 

load carrying capacity of the beam was determined when the computed stress was found 

equal to the tensile flexural strength of concrete. Although the beam at this stage had 

reached its full tensile strength the compressive portion of the beam did not. For an 

effective use of material the additional compressive strength must be counterbalanced by 

tensile reinforcement. The amount of tensile reinforcement required to resist the ba1a:nce of 

the tensile load was also computed. This provided the students with a background on the 

necessity of reinforcement in concrete beams. 

The students were informed to keep track of the schedule and to update it regulairly. 

The project schedule for each group, reflecting their progress, was evaluated by the 

instructor and timely adjustment was made. 

Students were also informed about the ASTM (American Society of Testing Matlerials) 

testing specifications for concrete and the importance of following a specified standard in 

order to achieve a valid test result which can be verified if required. The importance of 

water in concrete and how it affects the strength of concrete was also pointed out. The 

absorption and surface moisture of aggregates were not determined but the importance of 

their consideration in the design of concrete was mentioned. An additional amount of water 

on the surface of aggregates will increase the net water content of the concrete and 

eventually decrease the strength of concrete. In this regard the importance of calculating the 

surface water in aggregates was described in order to determine the correct batch weights. 

Finally, they were provided with information about preparing a report. They were 

asked to arrange the report in five subheadings, namely; 

i) Objectives - why they were doing the project 

ii) Introduction - any prerequisites, basic information 

iii) Methodology - how they would achieve the objective (s) 
iv) Results and Finding - what they have found from the test results, interpretation 

of the results 

v) Conclusions and Recommendations - outcome, any suggestions for future 

improvement of the study 

Basic ~re~aration 

According to the proposed preliminary objectives of the study the students obtained the 

necessary materials and prepared the testing devices as required. This took a bit of 

planning and designing on their part. A few of these project plans to achieve certain 

objectives are presented below. 

a) To illustrate the concept of using tensile reinforcements in concrete beams, 

disposable plastic molds used for casting test cylinders were shredded and the strips were 

used in concrete beams as a possible reinforcement. The students had to cut strips of plastic 

of dlifferent sizes and shapes. Different sizes, types (such as perforated ones with different 

size: holes, or with jagged edges) and shapes (with broadened ends) of strips were used in 

the beams to illustrate the concept of bonding interaction between the concrete and the 

plastic strips. 

Depending upon the objective(s) the students compared the results between the plastic 

reinforced concrete versus non-reinforced concrete, and also compared concrete with 

different size plastic reinforcements. The students also used plastic strips with jagged ends 

which interlock better with the concrete than plain plastic strips. 

b) to understand the performance of different types of plastics they used plastic soda 

bottles and auto tire strips as reinforcing materials. To increase the bonding resistance of 

the plastic, the soda bottle strips were punctured. Fiberglass mesh was also used to see its 

impact in increasing the strength of concrete and in minimizing the weight of the composite 

beam. Layers of punctured polyfibers mat were also used to differentiate the effect of the 

location of reinforcement in a reinforced concrete beam. 

c) to determine the effect of the distribution of reinforcement, plastic strips were also 

placed randomly in some structures and uniformly in others. Here the uniform distribution 

was attained by maintaining equal number of strips at any cross section of the beam. The 

proportions of plastics in the concrete molds were monitored by counting the number of 

strips in each specimen. To optimize the use of plastic strips in a simply supported beam, 

plastic strips were distributed non-uniformly along the length of the beam. In this case the 

optimization referred to the maximization of load capacity for the same amount of 

reir;~forcement. A higher percentage of plastic reinforcement was used at the mid-span than 

at the rest of the body to strengthen the weaker part of the beam. 

d) to experience the prestressing concept and its behavior in concrete beams, an auto 

tire strip was used as a prestressing tendon. A custom built three-sided wooden box with 

twct holes on the shorter side walls was used to mold the prestressed beam. The tire strip 

was slipped through the holes of the box. One end of the strip was fastened to the 

supporting board by drilled bolts. The other end of the strip was connected to a fixed block 

(support) by a hook. The adjustable hook was fastened to the block by a nut and washer on 

one side and the tire strip connection on the other side. The tire was then stressed by 

tightening the hook with a wrench. The prestressed tire strip inside the beam was cut 

jagged approximately three and half inches on both ends. Figure 1 shows the prestressing 
mechanism used for this case. An identical regular (non-prestressed) tire reinforced beam 

was also prepared to compare the results between prestressed vs. non-prestressed cases. 

In all cases non-reinforced identical concrete beams were prepared to compare the 

reinforcing property of the plastic-concrete structures as opposed to the homogeneous 

concrete beams. The students had to figure out how many beams were to be prepared to 

carry out the experiment. For each of the comparisons a minimum of two specimens was 

used. Three test cylinders were prepared for each batch of concrete. 

The students first had to prepare the forms into which they would pour the concrete 

mixture. Mostly they made rectangular beams varying in dimensions from group to group. 

One group made 9 beams of dimension 3.5"x3.5"~12", while another group made bea.ms 

of 3.5"x6"x22". A 2.5"x5"x16" beam was used for the prestressed concrete beam 

project. The students learned to put motor oil in the flat areas and Vaseline in the joints to 

prevent the concrete from adhering. 

Once the number of beams and test cylinders was known they computed the required 

volume of the concrete to be prepared. A known proportion by weight for the ingredients, 

such as 1 :2:4 (1 part of cement, 2 parts of sand and 4 parts of gravel) was used to compute 

the required amount of cement, water, sand and gravel. A known water cement ratio, e.g., 

0.45, was also prescribed to determine the amount of water. 

The computation of the amount of ingredients, however, required a knowledge of the 

material's volumetric properties such as unit weight, percent of voids, and percent of water 

absorption. In absence of actual material properties students had to perform the volumetric 

testing for sand, cement and gravel. A rough estimation of unit weight was determined by 

measuring the weight of the material in a cylinder divided by its volume. An example o:F 

such testing is presented below: 

Weight of sand in a (4"x8") cylinder excluding the cylinder's weight = 5.419 Ibs 

Volume of the cylinder = (area x length) =0.05818 ft3 

Unit weight of cement = 5.41910.5818 = 93.15 lbslft3 

Plastic strips and Quality tests 

The plastic strips used in the bottom part of the beam were tested for determining their 

tensile strength. Three specimens of each of the different types of plastic strips were tested 

in a tensile testing machine. The average tensile strength for the plastic mold strips 

(polyethylene) was found to be 1,894 psi. For the plastic bottle strips the average tensile 

strength was limited to the percent of elongation of the plastic. In this case the plastic had 

elongated about two times its length before it broke and the average tensile strength was 

about 2,500 psi. The percent elongation is important since inside a concrete structure, 

plastic can not attain its full strength or rather can not elongate to its full extent due to 

limitation in the elongation of the composite structure (plastic inside the concrete). The 

contributing strength of plastic in a concrete element is controlled therefore by the 

concrete's elongation capacity. The plastic strength is limited to an equivalent strain equal to 

the cracking strain of concrete ( about 0.003 for regular concrete). 

The tensile strength for the auto tire strand was 52,112 psi. This strength was 

determined for the composite steel-mesh reinforced plastic (auto tire) using the tensile 
strength testing machine. The load at which the steel wire tended to slip out of the plastic 

was considered as the capacity of the tire strip. During prestressing the tire strand was 

stressed below such a limit to avoid any form of slippage. 

Concrete Casting and Curing 

Using the concrete mixing machine the concrete was prepared and the mixture poured 

into the molds. All beams and test cylinders were poured using standard concrete practices 

and procedures. For each batch a concrete slump test was performed to measure the 

consistency of the concrete. Slump tests were performed according to the standard ASTM 

C143 practice. The students were able to see how the curing proceeded. 

The beams and cylinders were allowed to cure (in air during the entire time) prior to 

testing. The students knew that allowing the concrete to cure for too long would increase its 

strength to the point where the strength of the plastic used would become lower relative to 

that of the concrete. This would mean that the plastic would be useless in reinforcing the 

structure, as only a material with a strength greater than the tensile strength of concrete can 

add any significant reinforcement. The students allowed a week's time for the curing to be 

complete. The students had to make their own assessments as to the readiness of the 

concrete structures. 

Concrete Testing and Analysis 

Concrete cylinders were tested in the compression testing machine to measure their 

compressive strength. The concrete beams, with and without plastic strips of different sizes 

and shapes, were tested for their flexural tension strengths. In order to test the beams 

using the compression testing machine, students had to build a specifically designed beam 

breaking platform. One such platform, as shown in Figure 2, allowed for a concentric load 

from the hydraulic machine to be applied at the mid span of a simply supported beam. The 

breaking loads for the beams were determined for each of the test objects. This load was 

used to compute the flexural strength in tension by using equation (1). 
where, 

In equation (I), M is the moment in Ibs-in due to a mid span load, P, applied to ;I beam 

of span, 1 . Sx is the section modulus for a rectangular beam (bxd). Fbt is the tensileflexural stress in the extreme bottom fiber of the beam. 

FRAmMAC, a structural analysis program was also used to analyze the beam. The 

necessity of using a computer program was more obvious when analyzing a complicated 

structure such as multi-story building frame, and non-traditional loads. A two story frame 

structure due to applied loads, for example, can be analyzed by using the computer 

program with a lesser amount of effort than by using the conventional procedure. The 

applied stresses for each member in such a structure can be computed. A successful 

application of such computer analysis in teaching the fundamental concepts of structurd 

systems was demonstrated by the author in a previous paper (Ref #I). The author has 

furthered his efforts by using an advanced computer analysis in analyzing the plastic 

reinforced beams. 

It was clear to the students that the plastic reinforced beam was not a solid 

homogeneous material like a solid steel beam. In making the beams for the project, the 

plastic was randomly distributed at the bottom - more concentration at the mid-span than the 

two ends of the beam. This was done to strengthen the most critical part of the beam i.e., 

the mid-span, which attains maximum flexural stress. This means the beam will have mre 

strength ( to an extent more stiffness) at the mid span than at the ends. Also for concrete 

beams, material properties at the top of the neutral axis differ from the bottom half. By 

realizing the non-homogeneous distribution of materials and plastic reinforcement, it was 

understood that the simple FRAMEMAC analysis, which considers a single property for 

each beam element, cannot accurately analyze such a beam. At this point the Finite 

Element (FE) analysis was introduced with very little mentioning of its analytical 

background. An FE is important for this analysis since by chiding the beam into a nu~nlxr 

of blocks with different material properties in each block the actual material nonhornogeneitv can be accounted for. A group of students was assigned to perfom the finite 

element analysis for the plastic reinforced beams. The results and the procedure for this 

project will be discussed in a different paper. 

An analysis of the prestressed concrete beam was also performed to determine the 

additional strength provided by the prestressed tendon. The mid-span load which caused 

the beams to fail was used to compute the flexural stresses for both cases. The flexural 

stress due to the applied load for both reinforced and prestressed beams was compared to 

determine such a difference. The difference in the flexural stresses between these cases is 

the additional strength tvhich is developed due to the prestressed mechanism. 

RESULTS 

The flexural strength comparison results for four groups are presented in Tables 1 to 

4. 1 "x6" size plastic soda bottle strips were used by group one as a reinforcement ma~:erial. 
Shredded plastic strips (of concrete test-cylinder molds) of different sizes were used by 

groups two and three. The length for the beams, L, and their cross-sectional dimensions, 

b for width and d for depth, are also presented in these tables. These tables also present the 

slump value and compressive strength for each batch of concrete. 

The test results show that although the strength differences are marginal, the plastic 

appears to aid in increasing the tensile strength upon reinforcement. The test shows that the 

beams that did not contain plastic were brittle and fractured completely at breaking load. 

However, those containing plastic strips maintained their original cast state at breaking load 

without a complete collapse. Figures 3 and 4 show such a nature of failure in the test beams. 

In table one it is shown that the uniform placement of plastic with holes of about 1.8" 

diameter does not increase the beam's strength over the results of a non perforated plastic 

reinforced beam. This is because the holes in this case were not effective in interlocking 

with the concrete particles to enhance the bonding with the aggregates. 

Table two shows that uniformly reinforced beams withstand an average of 8.1% 

greater tensile stress than the beams with no reinforcing. The cylinders, on the other hand, 

with uniform reinforcing broke with approximately 11.7% less stress than the cylinders 

with no reinforcing. In this case, it was also found that the plastic strips left a clean smooth 

impression on the surface of the broken cylinders when removed, showing that the strips 

did not have proper bonding with the concrete. 

Table three shows that most significant increase in the strength occurred in using the 

plastics with jagged edges, about 2.5 times more than the plain beam. It was found that the 

jagged edged plastic broke while the plain edged plastic slipped out from the concrete 

when the broken beams were bent to remove the plastic from the concrete beam. This test 

showed that the rough edges of plastic provided extra gripping to aid in bonding with the 

concrete. Also, the smaller size plastic (118") provided greater strength than the larger size 

plastic reinforcing (114"). 

Table four shows a substantial increase in the strength of prestressed beam over 

regular reinforced concrete beam. The prestressing of the beam increased the beam's 

strength by six times. The load shown in this table is the mid-span load which caused the 

beams to Pail. 

Table 1: Test result for concrete beams, with and without (shredded soda bottles) 

reinforcement 
Table 2: Test result for concrete beams with and without (shredded plastic cylinder 

mold) reinforcement 

Table 3: Test result for concrete beams with and without (shredded plastic cylinder 

mold) reinforcement 

Table 4: Test result for prestressed vs. regular reinforced concrete beams (Both 

beams were reinforced with a 0.4 square inch auto-tire strip) 
CONCLUSIONS 

The oral presennations and written reports from the students showed their enthusiastic 

involvement in the cost effective hands-on design experiment. The project was very helpful 

for the students in understanding the practical aspects of reinforced concrete beams. It 

required each student to participate in designing concrete, testing beams, and summarizing 

the test results in a systematic way. 

The project clearly showed the importance of reinforcement in a concrete beam to 

increase its flexural tensile strength. The test results also differentiated between the brittle 

and ductile nature of structural failure. Beams with no plastic failed abruptly and severed 

completely while the beams with plastic did not. The test results of concrete beams 

reinforced with plastic strips, with and without jagged edges, showed the importance of 

the bond-length of rebars in achieving the strength of concrete beams. This conclusion is 

made by am observation of the greater bonding strength of jagged edged plastic reinforced 

beams than the plain surface plastic reinforced beams. The "honeycomb" structure found in 

some of the concrete beams showed the necessity of vibrating the concrete while pouring 

into a mold. A substantial increase in strength due to prestressing shows the importance of 

prestressed beams over regular reinforced concrete beams. 

The recommendation part of the student's reports shows their interest in the project. A 

few of the recommendations include a) using much greater grade of plastic - like disposed 

auto tire to achieve the desired results, b) perforating the plastic with bigger holes 

(depending upon the maximum aggregate size) for increasing the bonding between concrete 

and the reinforcement, and c) using long strips extending the whole length of the beam. 

REFERENCES 

[l] "A 'Case Study of Incorporating Computer Analysis of Structural Systems for the Students of a 

Construction Management Program," M. R. Chowdhury, ASEE Southeastern section Annual 

Meeting, Charlotte, NC, April 9-10, 1990. 
14 2i<iGlPJfii.L pp,GE 

MLACK AND WHITE PidQTOGRAPH 

Figure 1 : A Prestressing Mechanism. 

Concrctc Beam 

iccc% ol' I'las~ic Suips 

A cross section 

Fig~~r-e 2: A customized Beam Breaking Plathnil 
ORlGlNAL PAGE 

BLACK AND WHITE PHOTOGRAPH 

Figure 3: A Brittle type Failure in a Non-Reinforced Concrete Beam. 
Figure 4: An Auto-Tire Reinforced Concrete Beam Failure. 
STRUCTURE, PROCESSING AND PROPERTIES 

OF POTATOES 

Isabel I(. Lloyd 

Kmberly R. Kolos 

Edmond 6. Menegaux 

Wuy Luo 

Richard W. McGuen 

Thomas M. Regan 

Materials and Nuclear Engineering Unit 

University of Maryland 

College Park, Maryland 20742-21 15 

Telephone 301-405-5221 
Structure, Processing and Properties of Potatoes" 

Isabel K. Lloyd, Kimberly R. Kolos, Edmond C. Menegaux, Huy Luo, 

Richard H. McCuen and Thomas M. Regan 

University of Maryland, College Park, MD 

KEYWORDS: thermodynamics, structure, properties, processing, phase change 

PREREQUISITE KNOWLEDGE: This material is intended for high school 

students in an engineering or materials science course or college freshman 

OBJECTIVES: 

General: To demonstrate the relation between processing, structure, and 

thermodynamic and physical properties. 

Specific: 

1. To show the effect of structure and structural changes on thermodynamic 

properties (specific heat) and physical properties (compressive strength). 

2. To illustrate the first law of thermodynamics. 

3. To compare boiling a potato in water with cooking it in a microwave in 

terms of the rate of structural change and the energy consumed to "process" 

the potato. 

4. To demonstrate compression testing. 

EQUIPMENT AND SUPPLIES: 

19 Idaho potatoes (large)' 

voltage meter (to measure at least 120 V) 

clamp on ammeter (0-1 5 amps) 

three wire extension cord 

standard home microwave oven 

1.27 cm (1.2 in.) diameter wooden dowel 

4 styrofoam cups (8 or 12 oz) 

digital scale (at least 1 kg capacity) 

2 5.08 cm (2 in.) C clamps 

a bucket or very large beaker 

potato peeler paring knife 

butcher knife tongs 

oven mitts 1000 rnl beaker 

calipers 3 500 rnl beakers 

300 ml ice 1 150 rnl beaker 

metal grinder 30.48 cm ruler 

three wire extension cord 

thermometer (-1 0°C-150°C) 

laboratory weights (-50 kg total) 

* Support for the development of this experiment was provided by the National Science Fo~ndation via 

the ECSEL Coalition. 

3 potatoes for each boiling or microwave test time and 1 for the specific heat tests. 
type T (copper-cons"knt thermocouple and a digital readout or low mass 

itkern~ometer (0- 1 50°C) 

hot plate (variac type power supply, so that power is continuously supplied) 

stainless steel pipe: ID=3.175 cm (I 114 in.), OD=4.123 cm (I 5/8 in.), length= 25.4 

crn (10 in.) 

rniter box, fit to cut a 3.05 cm (1.2 in.) diameter potato specimen 

Lngol's Iodine: 0.2 % iodine and 0.4 % potassium iodide in water 

compression tester (See appendix A for instructions for the compression tester. 

The general form, not the exact size, of the tester is important.) 

In this experiment, potatoes will be "processed" by cooking cylindrical 

specimens in both boiling water and the microwave. During the cooking 

processes, potatoes undergo structural changes that affect their properties. The 

specific heat of a potato is similar in both the raw and fully cooked state. 

However, it increases dramatically as the potato undergoes the phase change 

which occlsrs to yield the state we regard as cooked. The compressive strength of 

the potato changes significantly as the potato is cooked; the change in the strength 

of a potat~ca due to processing will be monitored by performing a compression test 

on sample!; cooked for different lengths of time. The changes in the cells and cell 

walls will be observed by staining the potato specimens with a solution of 

potassium iodide, and the change in the composition of the potatoes will be 

observed by noting the difference in the mass of the specimens before and after 

cooking, 

Whhat is the chemical composz'fion of a potato? 

Raw potatoes consist largely of starch (-17 weight %) and water (-80 weight 

95). Starch is a natural high polymer of glucose. The main starches in potatoes are 

arnylose (which has an average molecular weight of -100,000) and arnylopectin 

(which has an average molecular weight of -1,000,000). The chemical 

composition of potatoes varies depending upon the variety and age, as well as 

how a potato is grown, stored, and processed (Talburt and Smith, 1959, as 

indicated by Mohsenin, 1986, p.445). Because of this variance, the tests 

conducted herein will be made with the same type of potato, preferably bought a 

the store at the same time. The potatoes will be peeled, cut into specimens, and 

soaked in water. To avoid bias during the testing, samples for each test should b 

taken from several different potatoes. 

Whdat happens to a potato when if is cooked? 

The important change that takes place when a potato is cooked is the chang 

of starch granules from a group of hard, compacted starch molecules to a tender, 

swollen mass. When they begin to take in water, the granules swell and 

"gelatinize". Gelatinization is a complex process. It involves the melting of the 

starch molecules within the cells as well as their hydration and dissolution 
(Leli6ve). A chemically bonded structure similar to that of gelatin (JEIaLOTN") or 

cement is formed during the process. Since the starch molecules have a variety 

of molecular weights and since processes other than melting are occurring, 

gelatinization in a potato occurs over a range of temperatures ( roughly 58'6 to 

66°C or 137°F to 150°F (McGee, p. 175)) rather than at a single temperature like 

the melting of water. During this phase change the specific heat increases 

dramatically. When the cell walls rupture during cooking, the gelatinized starch 

is released, which is evident from the stickiness of a cooked potato. The search 

gelatinization and the rupture of the potato-cell walls decreases the compressive 

strength of potatoes. 

Now does a microwave work? 

The microwaves produced in a microwave oven create an electromagnetic 

field. Polar molecules in this field tend to align their dipole moment with the 

direction of the field. The frequencies used in microwaves provide a field that 

changes at about the same rate as it takes a water molecule to align in the field 

(Walker, p. 134). Since the field is continuously reversing with a frequency in 

the range of 1x109 to 5x1012 Hz (Walker, p. 134), the water molecules are 

constantly rotating, bumping into each other, and generating heat due to friction. 

Since potatoes consist of approximately 80% water, they cook well in the 

microwave. 

What is the First Law of Thermodynamics? 

Materials Scientists state the First Law of Thermodynamics as: Whene.ver a 

system undergoes a change in state, the change in the internal energy of the 

system is equal to the heat input to the systern minus the work output by the 

system (dU=6q-6w). Other engineers tend to state it as: During a cycle that a 

system undergoes, the cyclic integral of the heat is proportional to the cyclic 

integral of the work. In simpler terms, the First Law states that energy is 

conserved. 

What is specl;Sc heat? 

The specific heat or heat capacity of a system is the ratio of the heat added 

or withdrawn from the system to the resultant change in temperature of the 

system. At constant pressure, Cp=(6q/6T)p. We can also relate the specific heat 

to the internal energy and enthalpy of the system, Cp=(6Ul6T),=(dH/drr), . The 

specific heat of water is 4.190 kJ/kg. The average specific heat of potatoes is 

3.39 kJ/kg (Hayes, p. 65). 

Now will the compressive strength be characterized? 

A compression tester will be used to develop a stress-strain curve for 

potatoes. The tester consists of a piston that moves through a rigid sulpport. The 

specimen is placed beneath the piston, and weights are applied to the tog of the 

piston. The change in the height of the specimen will be an indication of the 

strain induced by the force of the weight. The equations that will be alsed are: 

compressive stress=F/Ao 

strain = (li-lo)/lo 

(1) 

(2) 
where F is the force applied by the weight, A, is the original area of the 

specimen, lo is the original length of the specimen and li is the length of the 

specimen after applying force F. The average strain will be found by testing 

three specimens at each cooking time. The test will be performed by applying 

stress to a specimen until it fails or until the required weight exceeds the 

available weight. 

PROCEDURE: 

Preparation: Potato corer 

Sharpen one end of the stainless steel pipe by grinding the edge to a 

thickness of about 1 mrn. Be careful to keep the circular shape of the pipe. 

Preparation: Potato specimens 

1. Peel and then rinse one potato. Using the butcher knife dice it into cubes 

which are roughly 2 mm on a side. This should yield enough potato to do 

the specific heat measurements. 

2. Peel. three Idaho potatoes (three potatoes should yield enough specimens to 

perform three compression tests, compute the mass difference after cooking 

and observe structural changes by staining). Soak the peeled potatoes in a 

bucket of water while peeling the others to prevent discoloration due to 

contact with the air. 

3. Cut into a potato using the potato corer to get a cylindrical piece of potato 

in the pipe at least 2.5 crn (0.984 in.) long (see Fig 1). 

4. Using the wooden dowel, push the specimen back out the pipe until a 

straight-cut can be made on the bottom of the potato cylinder; cut the 

bottom with the edge of the knife blade against the pipe. Use the wooden 

dowel to push the remainder of the specimen out of the pipe. 

5. Repeat steps 3 and 4 to obtain three additional 2-cm specimens. 

6. Usimg the miter box to keep the ends straight, cut four specimens, each 

wit11 a length of 2 cm (0.787 in.); they will be tested in the compression 

tester. 

7. Cut a 2-mm thick half-circle off of the top of the fourth 2-cm specimen 

(see Fig. 2); this specimen will be used to observe mass and temperature 

changes. 

8. Cut another cylinder to a length of 4 cm (1.575 in.); this specimen will be 

used to show the extent of cooking through staining. 

9. Place the five specimens in a 500-ml beaker. Fill the beaker with water so 

the potatoes are covered. 

Preparation: Initial compression tester measurements 

I. Weigh the piston and top plate; record the total mass on the worksheet. 

(Remember to add this mass to the masses placed on top of the piston.) 
2. Determine the datum points on both the left-hand and right-hand rulers 

(see Fig. 3). 

Testing: Specific heat measurements 

Safety note: Use an oven mitt ts handle the beaker of hot water. 

Note: If a low mass thermometer is used to measure temperatures instead of a 

thermocouple, take care not to puncture the styrofoam cups. 

Record the weight of 2 nested styrofoam cups (these act as your 

calorimeter) on the worksheet. 

Add approximately 30 g of the finely diced raw potatoes to the cups and 

record the total weight on the worksheet. 

Measure the temperature of the potatoes and record it on the worksheet. 

In a 150 ml beaker heat about 100 rnl of water in the microwave for 20 sec 

at full power. 

Measure the temperature of the heated water and then immediately pour 

the water into the styrofoam cup calorimeter with the potatoes. Stir the 

water and potatoes with the thermocouple or the low mass therrnorneter. 

As soon as the temperature stabilizes, record it on the worksheet. 

Weigh the calorimeter, potatoes and water; record the value. 

Carefully pour the water down the drain and throw the potatoes away. Dry 

the styrofoam cups. 

Repeat the above using 100 ml of water heated in the microwave for 30 

sec., 1 min. and 1 min. 30 sec. Fresh minced potato should be used for each 

test. 

Record the weight of the other 2 nested styrofoam cups on the worksheet. 

Add approximately 30 g of the finely diced potatoes to the cups and record 

the total weight. 

Microwave the "calorimeter" with the raw minced potatoes for 2 min. 15 

sec. Then remove it from the microwave using the oven mitt. 

In a 150 ml beaker heat about 100 ml of water in the microwave for "iin. 

45 sec. at full power. 

Measure and record the temperature of the cooked potatoes. 

Repeat steps 5-7. (Be sure to stir the potatoes to break them apart.) 

Repeat steps 10-14 using water heated in the microwave for 2 min. 

Use fresh minced potatoes for the new test. 

Testing: Boiling potatoes 

1. Fill a 1000-ml beaker with 400 ml of water, measure and record its 

temperature and place it on the hot plate. Record the time at which you 

place the beaker on the hot plate. 
2. Measure and record the input voltage from the outlet where the hot plate is 

plugged in. Measure and record the amount of current flowing to the hot 

plate. An old extension cord with the outer insulation cut away at one 

section may be used to measure the input current with the clamp on 

ammeter since the clamp on meter should only be placed around one wire. 

Safety note: Only the outer insulation should be cut away on the 

extension cord - no bare wires should be exposed. Check with an 

electrician or the electrical shop teacher. 

From the 500-ml beaker remove the specimen with the half circle cut from 

the top (this will be referred to as the notched sample), shake off the 

excess water, and record the mass of the specirnen. Then shake off the 

excess water from the other four specimens and record the total mass of 

the specimens. 

Record the temperature of the water in the beaker where the potatoes are 

stored. 

Whel~ the water on the hot plate reaches 100°C, record the tirne. Then, put 

the five potato specimens in the water (including both the notched 

specimen and the longer specimen for staining) and record the starting 

time. 

Cook; the potatoes for a specified tirne. It is recommended that the 

experiment be performed for at least three tirne intervals: 2 112 minutes, 

6 mjnutes, and 12 minutes are suggested. For each time interval, five new 

potato specimens must be used. 

At the end of the cooking time-interval, immediately remove the potatoes 

with the tongs; immediately immerse the long specirnen in a 500-ml beaker 

of ice water. 

Shake the excess water from the notched specimen and quickly record the 

mass of the marked specirnen by recording the first stable mass reading; it 

is re:commended that a balance with a digital scale be used because the 

mass of the specimen will continue to change. Once the mass is recorded, 

measure the surface temperature of the potato; use the highest 

terngserature the thermometer reaches while it is resting on the top of the 

potato against the uncut sernicircle (see Fig. 2). 

Measure the volume of water remaining in the 1000 ml beaker after the 

potatoes have been boiled. Record it on the worksheet. 

Let the potatoes (except the long specirnen in ice water), cool in air for 10 

minutes and again record the mass and temperature of the notched 

specimen. 

Perform the staining and compressive strength tests on the appropriate 

specimens. 
Testing: Microwave cooking 

1. Determine the amount of time required to cook the potatoes. 

a. Fill a 500-ml beaker with 300 rnl of water and place it in the 

microwave. 

b. Measure the voltage at the outlet with the volt meter. Then use the 

extension cord to plug in the microwave and use the clamp om ammeter to 

measure the current. Turn the microwave on for B minute and record the 

input current and voltage. 

c. Calculate the power input to the microwave by multiplying the input 

current by the input voltage. 

d. Calculate the energy input from the hot-plate by multiplying the cooking 

time by the power input. Divide the calculated hot plate energy input by 

the power input to the microwave to determine the cooking time period 

required for comparable input energy. 

Example: 

microwave: current = 9.5 A; voltage = 117.3 V 

power input = 9.5*117.3 = 11114 W 

hot plate: current = B .8 A; voltage = 11 18.6 V 

power input = 1.8*1118.6 = 213.5 W 

energy input = 2113.5 W * 720 s = 153.7 kJ 

microwave cooking time = 153.7 &JIB .I 14 KW = 138 s 

e. Choose three microwave cooking times. Use one time period for which 

the boiling time and the microwaving time are approximately equal, (For a 

microwave rated 700 W or higher energy microwave, appropriate times are 

roughly 0.5, 1 and 2.5 min.) 

2. On a sheet of paper, draw five lines 7 crn (2.75 in.) Isng, at 72" angles (See 

Fig . 4). At the end of each line, draw a circle approximately the salme size 

as the potato specimens. Label the circles according to Fig 4, where mass 

is the spot for the half- circle notched specimen, stain is for the long 

specimen, and the numbers are for the specimens to be tested in the 

compression tester. 

3. Remove the notched specimen from the 500-nml beaker, shake off the excess 

water, and record the mass of the specimen on a fresh copy of pages 2 and 3 

of the worksheet. Then shake off the excess water from the other four 

specimens and record the toea1 mass of the specimens. 

4. Record the temperature of the water in the beaker where the potatoes are 

stored. 

5. Place the potato samples in the microwave on the sheet of paper aj~slrh the 

specimens standing up. 

6. Cook a set of potatoes for each of the chosen time periods; be sure to 

measure and record the input voltage from the outlet where the microwave 
is plugged in and measure the amount of current flowing to the microwave 

for each cooking time. 

7. Remove the potatoes with the tongs and immediately immerse the long 

specimen in a 500-ml beaker of ice water. 

8. Quickly record the mass of the notched specimen by recording the first 

stablle mass reading; it is recommended that a balance with a digital scale 

be used because the mass of the specimen will continue to change. Once the 

mas:$ is recorded, measure the surface temperature of the potato; use the 

highest temperature the thermometer reaches while it is resting on the top 

of the potato against the uncut semicircle (see Fig. 2). 

9. Let the potatoes (except the long specimen in ice water), cool in air for 10 

miniutes and again record the mass and temperature of the marked 

specimen. 

10. Perform the staining and compressive strength tests on the appropriate 

specimens. 

Testing: Staining 

I. Remove the cooked potato from the ice water. 

2. Cut through the center of the specimen, leaving two small cylinders. 

3. Rinse the freshly cut ends of the cylinders in the water to remove any 

starch molecules that were knocked loose by the knife. 

4. Cover the cut ends with the potassium iodide solution and note the shape 

and color of the staining. 

Testing: Compressive strength (Requires a group of at least two) 

Clamp the compression tester to a table using the two C clamps. 

Responsibilities: 

Stuldent A: 

Measure initial diameter of each specimen 

Determine base-level elevations on both left-hand ruler and righthand ruler (see Fig. 3) 

Measure top-plate elevations (see Fig. 3) 

Student B: 

Add masses to weight stand 

Ensure masses are centered and stable 

Record all data on worksheet 

Both A & B: 

Initially align (center) piston and top plate over specimen. 

I. Student A should measure and record the initial diameter of the specimen. 
Set the potato specimen under the hole in the compression tester and 

center the small plate on top of the potato specimen. Insert the piston and 

center it over the specimen; let it rest on the small plate. Record the lefthand and right-hand top-plate elevations of the potato specimen as read 

directly from the rulers; these values will be used to calculate the initial 

length of the specimen. 

Student B should successively place masses on the piston and record the 

masses. Student A should immediately state the resulting top-plate 

elevations with Student B recording the elevations on the worksheet. Use 

the following chart as a guide to the amount of mass to use for various 

cooking times: 

Cooking Cooking Mass Maximum 

Method Time (Min) Increment (kg) Load (kg) 

Microwave less than 1 4 36 

1 or more 1 16 

Boiled less than 6 4 

6 or more 1 

4. Student B should continue to add weight to the piston until the specimen 

fails or until the maximum load of allowable mass has been reached. For 

safety reasons, Student B should make sure that the masses are centered 

and the pile of masses is stable. 

Post-lab questions: 

1. Complete all computations on the worksheet. 

2. Plot the specific heat of the potatoes against the final temperature. 

3. Calculate the average value of the specific heat for tests where the potato 

was above and below the gelatinization range. How does this value 

compare with the specific heat of water? Do you think that this is a 

meaningful comparison? Why? 

4. Why is there such a large increase in specific heat during gelatinization? 

5. Why did the mass of the cooked potatoes decrease after the potatoes 

cooled? 

6. How is heat imparted to the potatoes when they are boiled in water? 

7. Combine the stress-strain data for the three specimens cooked at the same 

temperature, and use a curve-fitting program to fit the data to a power 

model (Y = aXb where Y is the stress and X is the strain). Plot the data and 

the corresponding function. 
Graphically compare the following: 

a. Stress-strain curves for the potatoes cooked in the microwave at 

different times. 

b. Stress-strain curves for the potatoes cooked in boiling water at 

different times. 

c. Stress-strain curves for the microwaved and boiled potatoes cooked 

with the same input energy. 

d. Stress-strain curves for the microwaved and boiled potatoes cooked 

for the same time. 

Discuss the energy efficiency you obtained for microwave cooking. How 

would you account for the remaining energy? 

Disci~ss the energy efficiency you obtained for boiling the potatoes in 

water. How would you account for the remaining energy? What role does 

time play when you are considering a cooking method? 

Whic;h is more energy efficient, microwaving or boiling? If you didn't 

consider the time it took to boil the water, how would the efficiencies 

compare? Would your answer change if you added in the energy efficiency 

in the process required to produce the input energy? Would your answer 

change if you considered the time that consumers typically used to cook 

potatoes? 

What type of values for the voltage and current did your meters measure, 

rms (root mean square), average, peak or peak to peak? What is the most 

appropriate value to measure? How would the measurement errors in your 

energy measurements affect the energy efficiency calculations? 
Potato Worksheet 

The specific heat of the potatoes is calculated using the formula: 

-mhot water*cwater*(Tfinal-Thot water) 

mpotato*(Tfinal-Tpotato) 

(The specific heat of water is 4190 J/kg°C.) 

34.1 
B Boiling and Microwaving Tests 

Cooking process: ---------- 

Time for wiater to boil: 

Total mass of 5 samples: --------- 

Mass of notched sample 

before cooking: -------- 

Mass of ncstched sample ---------- 

after cooking (hot): 

Mass of notched sample 

after cooking (cool): 

Volume of water which 

evaporated during boiling: --------- 

Mass of piston and top plate: 

Time cooked: 

Input voltage: ---------- 

Input current: --------- 

Surface temperature 

before cooking: ---------- 

Surface temperature (hot) 

after cooking: ---------- 

Surface temperature (cool) 

after cooking: ---------- 

Right datum point: ------ 

Left datum point: - 

diameter diameter 
Mass differences for the notched sample: 

Mass loss (hot) = Mass before cooking - Mass after cooking = ---- ---- 

% Mass loss (hot) = (Mass loss / Mass before cooking) X 100% = 

Mass loss (cool) = Mass before cooking - Mass after cooking = ---- ---- 

% Mass loss (cool) = (Mass loss / Mass before cooking) X 100% = -------- 

Staining observations: 

Record any observations made during the staining process. If a reg.ulam: geometric 

shape was observed, record the dimensions. 

Stress-strain calculations: 

Make a chart with the following columns: 

Mass, Applied force, STRESS, true height (left), true height (right), average 

height, STRAIN. 

Use the following equations to calculate the stress applied to the potato and 

corresponding strain: 

SS: Original area of the specimen (m2) = A, = n d2 / 4 

Applied force (kN) = Mass (kg) X 9.81 m/sec2 X 1000 

STRESS (Wa) = Applied force / Original area 

STRAIN: True height (left) = Measured height (left) - Left diatum point 

True height (right) = Measured height (right) - Riglil~t datum 

point 

Average height = [True height (left) + True height (right)] / 2 

STRAIN = (average height - original height) / origi~lal height 

Energy calculations: 

Input power = Input current * Input voltage = W 

Input energy = (Input power * Cooking time in seconds) / 1000 = IkJ 
The First Law of Thermodynamics states that energy is conserved. Therefore, all 

of the energy we put into the system can be accounted for directly or as waste 

heat. The ratio of the energy we need with the energy we use is the efficiency. 

I. Microwave cooking: 

Theoretically, microwave cooking should be very efficient since microwaves are 

designed to heat up the food rather than the cooking medium. Therefore, the 

minimum energy required to cook a potato is the energy required to heat the 

potato to the final temperature, El, and the energy required for gelatinization, E2. 

a. Look at your compression test data and determine the minimum cooking 

time required to fully cook the potatoes in the microwave. Use the data 

from that test to estimate the minimum cooking energy and the energy 

efficiency. 

b. Calculate the minimum energy, E, required to cook the potatoes: 

Tf(OC) 

El = mass potatoes cooked * cpotatodT = 

i=Ti(" C) 

"3 = Enthalpy or heat of gelatinization. Since the enthalpy of 

gelatinization is not available, we will roughly estimate it by 

the latent heat of potatoes which is 258 kJ/kg. 

Ez = mass of potatoes cooked * 258 kJkg = ----- 

c. Calccllate the efficiency of the microwave cooking process for your 

samples. 

efficiency = e = minimum energy required / energy input= ----- 

2. Boiling in water: 

a. Look at your compression test data and determine the minimum cooking 

time required to fully cook the potatoes by boiling. Use the data from that 

test to estimate the minimum cooking energy and the energy efficiency. 

(Note: you must include the time it took to boil the water for a fair 

comparison with microwave cooking): 
b. Calculate the minimum energy, E, required to cook the potatoes by boiling. 

Since you must boil the water as well as cook the potatoes, you will need 

to add two more terms, E3 and E4, to E. Eg is the energy to raise the 

temperature of the water from the initial temperature to 100°C. E4 is the 

heat of vaporization used by the water which evaporates during the boiling 

process. 

Tf("C) 

El = mass potatoes cooked * cpotatodT = 

i=Ti("C) 

E2 = mass of potatoes cooked * 258 kJ/kg = 

Tf("C) 

E3 = mass water boiled * cwaterdT = 

i=Ti("C) 

(The heat capacity of water is 4190 J/kg.) 

Eq = heat of vaporization of water 

= mass water evaporated * 2254 J/kg = 

c. Calculate the efficiency of the boiling of your samples. 

efficiency = e = minimum energy required / energy input = --- -- - - 
INSTRUCTOR NOTES: 

Appendix B contains curves with sample data for all of the experiments. 

Fresh copies of pages 2 and 3 of the worksheet are required for each boiling and 

microwaving test. 

Haytowitz, D. B. and Matthew, R. H., Compositions of Foods: Vegetables and 

Vegetable Products, Agriculture Handbook 8-11, 294-297, USDA, Washington D.C., 

1984. 

Hayes, 6. D., Food Engineering Data Handbook, John Wiley and Sons, New York, 

1987. 

Hunt, R. G., "The Physics of Popping Popcorn," The Physics Teacher, 29, 230-235 

("191). 

Lelieve, J.., "Gelatinization of Crosslinked Potato Starch," StarchJStarke 37, 267- 

269 (1 985). 

McGee, H., On Food and Cooking, Macmillan Publ. Co., New York, 1984. 

Mo hsenin, N. N., Electromagnetic Radiation Properties of Foods and Agricultural 

Products, Gordon and Breach Science Publishers, New York,I 984. 

Mohsenin, N. N., Physical Properties of Plant and Animal Materials, Gordon and 

Breach Science Publishers, New York, 1986. 

Pomeranz, Y., Food Analysis: Theory and Practice, Van Nostrand Reinhold Co., New 

York, 1987. 

Talburt, W.F. and Smith O., Potato Processing, AVI Publishing Co., Westport, Conn, 

1959. 

Walker, J., "The Amateur Scientist", Sci. Amer., 256, 134-1 38 (1 987). 

SOURCE OF SUPPLIES: 

Most of the supplies are readily available in the typical high school chemistry or 

physics laboratory or the grocery store. The clamp on ammeter and voltmeter (a 

multimeter is fine) are available from an electrical supply house, including the 

Radio Shack catalog, the clamp on meter is -$50. The dowel, pipe, screws, etc. 

should be available from a home building supply store or the school shop. The 

metal necessary for the compression tester may be available in the school shop. 
APPENDIX A THE COMPRESSION TESTER 

SUPPLIES: 

1 piece of metal (steel or aluminum) 91.44 cm x 5.08 cm x 0.635 cm (36 in. x 2 In 

x 114 in.) to be cut into 3 equal pieces 

2 - 1.588 cm (518 in.) bolts, 15.24 cm (6 in.) long 

4 - 1.588 cm (518 in.) hex nuts 

4 - 1.588 cm (518 in.) flat washers 

1 - solid aluminum shaft, 2.54 cm (1 in.) diameter, 12.7 cm (5 in.) long with the 

ends squared 

1 - aluminum plate, 10.16 cm x 6.35 cm x 1.27 cm (4 in. x 2 112 in. x 112 in.) 

1 - 0.635 cm (114 in.) flat head screw, 2.54 cm (1 in.) long 

2 - 15.24 cm (6 in.) rulers 

1 - small circular plate, 5.08 cm (2 in.) diameter, 0.9525 cm (318 in.) thick (th~s 

is referred to as the top plate) 

2 - 5.08 cm (2 in.) C clamps 

drill press with 518 in. drill bit, 1 in. drill bit, 114 in. drill and No. 7 drill 

1/4-20 tap 

hacksaw 

center punch counter sink 

f i l e 

Construction of the compression tester: 

1. Cut the 91.44 cm (36 in.) piece of metal into three equal parts with the 

hacksaw. 

2. File the sharp edges using a metal file. 

3. Stack the three pieces of metal on top of one another and clamp the ends 

with the two C clamps. 

4. Draw a line lengthwise through the center of the 30.48 cm (12 in.) piece. 

Draw three perpendicular lines at 5.08 cm (2 in.), 15.24 cm (6 in.) and 

25.4 cm (10 in.) from one end of the piece. 

5. Center punch a dimple at each of the three line intersections. 

6. Drill a 1.588 cm (518 in.) hole through the clamped pieces at the 5.08 cm (2 

in.) and 25.4 cm (10 in.) intersections. 

7. Unclamp the three pieces and reclamp two of the pieces using the 1.588 cm 

(518 in.) bolts as locating pins through the two drilled 1.588 cm (518 

in.) holes, keeping the marked piece on top. 
8. Drill a 11 588 cm (518 in.) pilot hole through the clamped pieces at the 15.24 

cm (6 in.) mark. Redrill the hole with the 2.54 em (1 in.) drill bit. 

Ugaclamp the pieces. 

9. Locate the center of the 2.54 em (1 in.) solid shaft and dimple it with a 

centcx punch. Using a No. 7 drill, drill a 1.588 crn (518 in.) deep hole. 

Thread the hole using the 1/4-20 tag. 

10. Locate the center of the 10.16 cm by 6.385 cm (4 in. by 2 in.) aluminum 

plate and dimple it with the center punch. Drill a 0.635 crn (1/4 in.) 

hole through the plate and counter-sink it deep enough to make the 

head of the 0.635 cm (114 in.) flat-head screw flush with the top of 

the plate. 

I I. Place the plate on top of the shaft, insert the 0.635 cm (114-in.) flat-head 

screw through the plate into the shaft, and tighten the screw. 

12. Assemble the framework using Fig. 3 as a guide. Put the two 1.588 cm 

(518 in.) bolts through the 30.48 crn (12 in.) piece with only two holes 

and install one 1.588 crn (518 in.) nut on each bolt, leaving 9.525 cm 

(3 3,14 in.) between the nut and the head of the bolt. Install one of the 

remaining 30.48 cm (12 in.) pieces through the outside holes over the 

bolts and place two washers on each bolt. Place the remaining 30.48 

crn (112 in.) piece on the bolts, lock the assembly together with one nut 

on each bolt, and tighten all four nuts. Insert the shaft with the 

attached plate through the 2.54 crn (1 in.) hole in the center of the 

franlework. 

13. Set the small circular plate underneath the shaft. Tape two 15.24 cm (6 in.) 

rulers to the framework in such a way that the centimeter markings 

on each ruler are at the outer edges of the circular top plate. 
potato specimen \ 
Front view 

Placement of 

/ thermometer 

specimen to be weighed 

nnd proper placement for 

the thermometer during 

temperature measurements, 
MQSSeS 

ei~ht stand 

Comgression tester 

use'd to test the 

compressive strength 
/ FACE FRONT 1 

Diagram for making the 

sheet required for the 

proper placement of 

potato specimens in the 

microwave, 
APPENDDX 8 SAMPLE DATA 

T (final) OC 

Figure B1: Specific heat versus the final temperature. 
Figure B2: Stress-strain curves for boiled potatoes. 
MICROWAVED, 0.5 MIN 

Figure B3: Stress-strain curves for microwaved potatoes. 
Microwaved, 0.5 min 

Input energy = 34.51 kJ,/ 

300 Raw 

Figure B4: Stress-strain curves for potatoes cooked with input energies between 

0 kJ and 40 W. 
lnput energy = 81.53 kJ 

Microwaved, 1 rnin 

lnput energy = 66.50 kJ 

STRAIN (cWcm) 
Boiled, 12 min 

Boiled, 18 min 

Input energy = 229.78 W I 

Microwaved, 2.5 min 

________-------- 

Input energy = 1 67. I 5 k 

STRAIN (cdcm) 
Figure B7: Stress-strain curves for potatoes cooked for 2.5 minutes by different 

methods. 

Boiled, 2.5 min 

Input energy = I 67.1 5 
COMPUTER INTEG TED LAB TESTINGr 

Charles C. Dahl 

Engineering Department 

Ventura College 

4667 Telegraph Road 

Ventura, California 93003 

Telephone 805-654-6400 

Extension 1367 

361 

PRECEDIMG PAGE BLANK WOT FFILPdED 
COMPUTER INTEGRATED LABORATORY TESTING 

Charles C. Dahl 

Engineering Department, Ventura College, Ventura, Ca. 

- KEY WORDS: Engineering Materials, Test Equipment, P/C, computer, 

retrofit, laboratory, transducer, thermocouple, LVDT, Young" Modulus, temperature, pressure, Datalogger. 

PREREQUISITE KNOWLEDGE: This material is intended for the Engineering 

Materials laboratory. The course is for .second or third year engineering students with college chemistryand calculus based physics 

prerequisites. This computerized instrumentation would also be profitable for college Vocational/Technical or H.S. courses with such 

laboratories. 

OBJECTIVES: Integration of computers into the Engineering Materials 

Science Laboratory course, where existing test equipment is not computerized, is the objective of this work. This includes temperature 

vs. time for phase change experiments; pressure vs. elongation for 

stress vs. strain; beam bending; creep; or a wide variety of experiments where change can be measured by transducers, strain/resistance 

(s/r) gages or bridges, thermocouples or similar devices that produce 

a resistance or voltage change. Input from such sensors is fed 

through a Datalogger to a P/C or 386. Data is imported to a spread 

sheet program for tables, graphs and charts. 

EQUIPMENT SUPPLIES: Equipment and supplies include the following: 

1) Sensors for specific test, i, temperature thermocouple, or pressure 

transducer, or Linear Variable Differential Transformer, or S/R strain 

gages, etc. ; 2) Datalogger and related program for P/C, or storage; 3 0 

P/C; 4) Spread sheet program for the computer; 5) Any additional 

standard test equipment used without computer instrumentation for the 

specific test, such asauniversal testing machine. 6) Normal specimens 

for the test, such as a wood tensile or compression sample, material 

to undergo phase change, beam to be bent, etc. 

PROCEDURE: Lab 1) To demonstrate and produce a material phase change 

curve we shall do the following: 1) Measure temperature vs. time 

during cooling from a liquid to a solid with thermocouples connected 

to the data logger and the P/C. 2) Import the data into a spread 

sheet and produce a data table and graphs/curves of time vs-t~emperature for the cooling curves and related phase change point. 3) Discussion should interpret the curves which display the delay in cooling 

when phase change is taking place. 4) This combined with a phase 

diagram of the materials used allows the determination of the composition of the material. 

A common materials experiment is to use a lead+antimony alloy to 

demonstrate the phase change, with delayed cooling recorded at the 

phase change point of the specific composition. Here the material is 

heated to 330 O C, and the thermocouple is inserted in the liquid which 

is then allowed to cool. Assuming the same approximate temperature 

differential and conductivity of the container, the liquid will cool 
at a constant rate to the point of phase change; it will hold that 

temperature until the heat of phase change has been transferred and 

the cooling rate for the solid phas,e will be displayed. The fact that 

this data is not nomally taken or reduced by computer points out the 

difference of a conaputer integrated experiment from a conventional 

one, The student must analyze the data to be sure that it is meaningful, Materials such as antifreeze and water, with different phase 

change points may be substituted. 

Lab 2) A demonstration of the modulus of elasticity and 

related stress strain cuwe, plastic perfomance, maximum and failure 

strength is done with force measurements taken by pressure transducer 

on the ram and change in gage length measured by an LVDT attached to 

the test sample. The pressure transducer and the LVDT signals are 

fed, with the given time interval, to the data logger and then to the 

lP/C for recording. Parallel readings can be taken with an S/R strain 

gage and the WDT mounted to the same sample, both measuring displacement, Our experience is that the S/R gage glue bond to the sample is 

broken prior to the material failure in the plastic range. 

This process of recording data by sensors that are connected to a data 

logger which adds a time base, and the data logger in turn to a computer, ~iiaces the materials labs into a computer integrated mode with 

]minimum expense, maximum flexibility and in a comercial model and 

level. The sensor signals are input into a spread sheet for tabular 

records, curve generation and graph printing. The laborious process 

of hand recordings, related errors, data entering time and errors are 

.eliminated and the tabular and graph vality is enhanced. Much of the 

equipment can be shared with the physics lab for other experiments. 

CREDITS: Noise level and temperature environment research by the author 

was facilitated by Gerald Duffy of the Instrumentation Division of the 

NCEL at Port Nueneme, California. Mr Duffy introduced and set up the 

Campbell Scientific Micrologger, themocouples and microphones for the 

study. Mr Duffy has continued to give counsel for this Ventura College pro j ect , 

REFERENCIS: Elements of Material , Van Vlaek; 

lford; Enqiv joint sealants; Alu~augh, Dahl, Hoffard 

SOURCE mil SUPPLIES AND EQUIPMENT WITH COST ESTIMATE: 

Campbell Scientific: 

21% -- 21X MICROLOGGER W/40K 1845. 

ALK21X - WLKGhLINE BATTERY BASE FOR 21X INC. 

SC32A - OPTICALLY ISOLATED RS232 INTERFACE 130. 

SC25PS - RS232 RIBBON CBL W/PINS TO PINS/SK 25. 

~~208 - SUPPORT SOFTWARE 200. 

M416 -.- :LGCMNL 4 WIRE INPUT WLTIPLEXER 435. 

SDUCER MODEL 241 0-1000 PSIG 315. 
SCHLUMBERGER: 

LVDT ARC 15 

SDUCER CONDITIONER OD3 

S/R STRAIN GAGES; THERMOCOUPLE WIRE; 386 OR P/C COMPUTER. 

10/17/91 rev. 1/3/92 

COMPUTER INTEGRATED LABORATORY DIAGRAM 
MECHANICAL PROPERTIES OF BRITTLE MATERIAL 

L. R. Cornwell 

Department of Mechanical Engineering 

Texas A&M University 

College Station, Texas 77843-3 123 

Telephone 409-845-125 1 

367 

$~EcED!WG PAGE DLAhlK tJ3T hiLk4ED 
Mechanical Properties of Brittle Materials 

L.R. Cornwell and H.R. Thornton 

Department of Mechanical Engineering 

Texas A&M University 

College Station, Texas 77843-3123 

KEY WORDS: Brittle materials, bending modulus, wood, glass, 

surface cracks, fracture toughness 

PREREQUISITE KNOWLEDGE: This experiment is suitable for 

students who have been introduced to the concepts of ductiiity and 

brittleness. They should also understand the meaning of modulus of. 

elasticity. 

EQUIPMENT AND SUPPLIES: Universal testing machine such as 

Instron and MTS, bending fixture, rectangular wood specimens 

1 crn by 1 crn 15 cm, glass slides. 

INTRODUCTION 

Brittle materials are difficuit to tensile test because of gripping 

problems; they either crack in conventional grips or are crushed. 

Furthermore they may be difficult to make into tensile specimens for 

example threaded ends or of dogbone shape. To overcome the problem 

simple rectangular shapes can be used in bending (i.e., a simple beam) in 

order to obtain the modulus of rupture and the elastic modulus. The 

equipment necessary consists of a fixture for supporting the specimens 

horizontally at two points, these contact points being rollers which are free 

to rotate. The force necessary to bend the specimen is produced by tup 

attached to the crosshead of an Instron machine. 

PROCEDURE 

The specimens are rectangular in shape and are measured for width 

and thickness; the length is the distance between the two supports. The 

wood specimens we used were ash, oak and cherry and were cut along the 

grain and normal to it. Most kinds of wood are suitable for this 

experiment and will show anisotropy. Three glass slides are used with a 

single scratch in each made with a suitable instrument such as a glass 

cutter. Effort should be made to keep the depths of scratches the same. 

The three scratches will be in different directions: one transverse, one 

longitudinal and the third at an angle of 45O, and with lengths equal to the 

transverse dimensions. 

369 

PRECEDiIVG PAGE BLANK NGT FILhIED 
Each specimen is placed on the supports and subjected to a bending 

load until fracture. The Instron will record bending load against crosshead 

movement i.e., deflection in the specimen. Strictly speaking the crosshead 

rnolvement recorded will include machine deformation but since the loads 

involved are small, the deformation will be small and will not detract from the 

uti'iity of the experiment. 

The maximum fiber stress, tensile on the bottom of the specimen is 

given by the standard formula, 

where S is the stress, I the second movement of inertia, C is half 

the specimen thickness and M the bending moment, PL/4, where P is the 

load and L the distance between supports. For a rectangular bend this 

translates to, 

where b is the width and h the thickness. If P is the maximum load 

in kg and the dimensions are in meters then S is called the modulus of 

rupture in Pascals. It can be shown that the bending modulus E is given by 

where A P/A6 is the slope of the load-deflection curve. Thus the 

mo~dulus of rupture and bending modulus can be calculated and compared 

to values obtained from the literature. Some typical values are given in the 

Appendix. A sketch of the support is shown in figure 1. 

The distance between the supports is adjustable so that specimens of 

variable length L can be used. Note the smaller rollers on each support 

allow relative motion between the specimen and supports as the specimen 

begins to deflect. Otherwise frictional forces at this point would increase 

the: load. 
Note that if a fairly ductile material is tested resulting in significant 

deflection the specimen may slip off the supports. 

The purpose of the scratches on the glass is to show the influence alf 

scratch orientation on strength. For the glass specimens one specimen is 

fractured without any surface stratches. For the other specimens scratches 

are placed on the tensile surface preferably with a diamond cutter with the 

same pressure. Sharp notches stay sharp in a perfectly brittle material 

since there is no mechanism for plastic flow. To demonstrate the influence 

of orientation on fracture behavior scratches are placed transverse to, 45' 

and along the length of the glass slides. The equation governing the stress 

intensity is 

where 13 is the angle of the crack to the transverse direction and a is the 

crack depth. This relationship predicts that K, is largest when 13 = 0, i.e. for 

the tranverse crack. Thus the fracture strength will be lowest for this 

orientation. When 13 = 45", the stress intensity falls to half the transverse 

value. Strictly speaking this is only approximate since mode I1 on K,, is 

ignored so this would be a lower limit. When 13= 90, i.e. for a longitudinal 

crack K, becomes zero and this scratch should have no effect. Another 

way to think of this is the stress concentration at the side of a hole 

where a, is the stress concentration factor for a nominal stress a, applied 

at an ellipse with major axis 2a and minor axis 2b. In this case b >)a so 

that a, = a n or a stress concentration of one. 

The experimental values for an unscratched glass side approximate 

those of published values, see Table 11. The largest drop in fracture 

strength is shown by the specimen with a transverse scratch, no effect with 

the longitudinal stratch, and the 4.5' scratched specimen in between. 

In conclusion we would like to add that we tried the experiment 

described last year by Roy Bunnell on stress skin composites using paper 

reinforcement since our apparatus was ideally suited to the experiment. 

Essentially it shows that a very weak material like styrofoam can be 

strengthened considerably against bending by placing a piece of cardboard 

on the tensile side of the specimen. The demonstration was very 

convincing. 
REFERENCES 

ASM Metals I-Iandbook, Vol. 8, Ninth Edition, p. 115, 1985. 

Table I 

Typical Values For Different Woods 

Young's Modulus Gpa 

Perpendicula 

Grain 

to Grain 

Suggested values of allowable stress in construction 

along grain 3.45 - 6.9 MPa 

Table I1 

Properties of Soda Lime Glass 
Fig. 1 Sketch of three point bending fixture 

Note: 1) Hardened steel pin .1 crn diameter 

2) Steel rollers, held in place by 

rubber bands amched to hooks in side of suppoli.a 

3) Vertical supports slide in groove in base 

4) Scale approximate half size 
INTRODUCTORY HEAT-T 

AND 

HIEAT-TREATING OF TERIALS 

Edward L. Widener 

Mechanical Engineering Technology Department 

Purdue University 

Knoy Hall - Room 119 

West Lafayette, Indiana 47907 

Telephone 3 17-494-7521 

375 

PRECEDING PAGE BLAHK NOT FlLMED 
Ii\JTRC!DL'(3TCIRk' HEAT-TRANSFER 

E. L. Widener - MET, Dei>t. - * Purdue Univ. - i4. Lafayette, IN 

PREREQUISITE 'i(N0WLEDGE: Typical high-school students of physics or 

chemistry should understand basic concepts of mechanics (force, work. 

momentum. energy. veiocity. acceleration) in fundamentai units ii1.S. 

and S.I.) of basic dimensions (Length,. Mass. Tine). 

OBJECTIVES : To introduce that notorlo~~s necessity . known as 

"thermo-dynamics", in existing heat-treating experiments using 

available items. To define thermal properties of materials: visualize 

expansivity, conductivity. heat-capacity, and melting-polnt of common 

metais; remember basic values: compare commercial materials, and 

consider eiectricai/mechanicd analogs. 

EQUIPMENT & SUPPLIES: Bealters (500 to 1000 rnli or buckets 

(2-5 yaiion) for water-oil-sand quenches. Furnace. torch. or burner 

ieiectrlc or gas) for red-hot specime~s: to re-heat specimens 

(tempering or aging). Grating (expanded-metal, wire-mesh) and 

flrebrlck (supports) for a cooiing table. Piece of pipe (steel. 

plastic) about 10" long (25 cm) and 4"-Schedule 40 size (10 crn 

round); with circumferential holes (6-5) for 1/8" rods !wires) about 

6" long (say 3 rnrn X i5 cm). Coffee-pot or hot-plate, to boil water. 

- Stop-watch (or timer) and thermometers (dial or glass). longs. 

gloves. and safety glasses. 

BACKGROUND: 

In ancient Greece and Persia. heat was considered a universal 

element (earth, air, water, fire); but not until 1698 tSavery 

steam-pump) and 17i2 (Newcomen steam-engine) was heat reified to 

mechanical work.ll1 The materiais lab is a good place to demonstrate 

the dynamic process of "heat transfer", to e1ucid:ate the eiusive 

concept of "heat". and to inter-relate "heat/workienergyH. 

Rooted in Old English words (hot, hetup), heat is a fundamental 

and fascinating subject. variously defined: energy added to 

substances to raise temperature, change-state, or accelerate 

reactions; energy associated with random motion of 

atoms/ionsimolecules; energy flow from nigh temperature to low. 

Although heat is temperature nor a property of materials, it is 

prominent in properties and,processes which are temperatux-e--related: 

expansivity (a), density (7) , conductivity (0,~) . heat capacity 

viscosity (p) , melting point (t) ; and annealing, normalizing, (CP> 

quenching, tempering, stress-relieving, aging, warping, corroding, 

hysteresis, friction. 

DEFINITIONS: 

Heat (Q) is thermal-energy in transit (area under a T-S curve, a 

plot of temperature vs. entropy:) because of a temperature difference. 

Similarly, Work is mechanical-energy in transit (area under a P-V 

diagram, a plot of pressure vs. volume) because of a force 

difference. Also, Am~eracre is electrical-energy in transit, because 

of a voltage (potential difference). 

377 

PRECEOENG PAGE BHAFdK NOT FliMED 
Heat has a work-equivalent (about 779 ft-lb/'Btul but neither of 

these "path functions" are ldenticai tc Enerf~y. 2 .'poinr fi~nctjon," 

Think of a truckload of gcods, partway bet.weei-I a warekiouse and a 

shop; heat is like the shipment. SI-L~ energy is like an inventory (at 

warehouse or shop) i21. Similarly, an accountant takes t-he difference 

between "balance sheets" (field strengths) as "profit-or-lossL' (heat 

transfer. work done). 

Heat is generally measured in units of joule, calorie, or m. 

Worlc. or energy is expressed in foot x pounds ift-lb) or joules 

(newton-metre?. The U.S.A. still prefers to use the "British Thermal 

Unit" iBtuj. defined as the energy to raise a pound (Avoirdupois) of 

water (atmospheric pressure) by a Fahrenheit degree !Fa).. or absolute 

Rankine degree {Re). Think of this as the chemical energy (potential) 

In a regular, wooden. kitchen-match (abouc 3" iong). It is almost a 

kilo-joule. 

The aid metric calorie was defined as the energy to raise a gram 

iml) of water iatmospheric pressure) by a Centigrade degree (C", now 

called Ceisius) or absolute Kelvin degree iKj. Note this standard for 

5.1. (Systeme Internationale) disallows a degree mark (K0j. which 

yreciudes the convention of JakobiHawkins[3]: Water freezes at 32°F. 

Sut boiis 180 Fo higher, a useful distinction between "point" and 

"line" functions. Also note the dieticians' usage of "Calorie". which 

is a "kilo-calorie" of food (1.000-cai = Cal). 

The 3.1. unit of work, heat, and energy is the joule: i.e., force 

(newton) times distance (metre). Of course, the newton is the mass 

(kilogram) times acceleration (metre per second-squared). Note 

"force" is better defined as "time rate-of-change of momentumu: so. 

F=d(mv)\dT. Since 2.2 lb (mass) is about 1-Kilogram, and 2.54 cm is 

exactiy 1-inch, the kilo-joule is about a Btu. A newton is about a 

quarter--pounder . More precisely. a Btu = 1.055 kJ = 778.16 it-lb = 251.98 small 

cal. A calorie = 4.1868 J. A kiiogram = 2.205 lb (Av). A lb = 4.448 

N. And a Watt = J/s = 3,413 Btu/hr.[41 

Generally, hydraulic analogs are more graphic than thermal 

systems. Mechanical to thermal conversion is more efficient (up to 

10096, including friction) than thermal to mechanical. An electrical 

system is more easily and accurately measured then its thermal 

ana l og . 

Thus, electrical capacity (C+) is charge (coulombs) per voltage 

difference (CX=Q"/AE): and thermai capacity (C) is heat imput + 

temperature difference (C = Q/AT). Sometimes this is mis-named 

"heat-content." S~ecific heat-capacity is then standardized at 

constant pressure (Cp = Q/m XAT) per unit mass. So, Cw =Ah/AT) in 

terms of Enthalpy (Ah = Q/m). 

Hydraulic flow rate ((2) is cross-sectional area (pipe) times 

average-velocity (fluid), so Q = AV. Then. "pipe conductivity" could 

be expressed as C = QL/L2 X AT X At. the analog of thermal 

conductivity . Electrical conductivity (sigma)' is the inverse of resistivity. 

Use Ohm's Law (E = IR = Ampere X Ohm) and define an Ampere 

iCoulomh/second): then a = l/RL. 

Thermai conductivity (~appa) is heat input X length + (area X 

time interval X temperature difference). Thus, 

PC= $L/L,~ X AT X At. 

The classic Dulons-Petit Rule (1819) says: Specific-heat (Cp) 

times Atomic-weight (amu) is approximately constant (6.4) for solid 
elements (above 40 wt.1. The classic Wiedemann-Fr-anz Ratio says: 

'I7~ermal-conciuct ivity (IE) over Electrical-conduct ivity (a) is 

approximately constant t '7.5 X 106, J x Q / s :( Kj for metals at 

constant temperature. This constant is aiso the "Lorenz" constant (ij 

times absolute "Kelvin" degrees (t) for variable-temperature tests. 

EXPERIMENTS: Now the fun begins! 

1. Relative Quench Factor (RQF) 

A steel disk (AISI 1040. 2" dia. X k" thick) is heated red-hot 

(1650" F,, 900°C) and quenched quickly in a pail of water (70" F, 

21°C). The sizziing will stop in about 30 seconds. so the disk is not 

too hot to touch. A second disk (AISI 1080) quenched in water will 

take about 30 seconds, but has twice the carbon (0.80 W/Oi and twice 

the BCT martensite grains (Body Centered Tetragon) so the disk cracks 

badly. A third disk iAISI 1080) quenched in oil will take about 90 

seconds, make less martensite (shown by Rockwell C hardness). but has 

no cracks. Thus, the oil is a slower. safer quench; higher boiling 

point and greater viscosity are the reasons. Show students how a sore 

thumb. soaked in hot-water. becomes comfortable uniess "stirring" 

ensues; thus. heat-transfer is enhanced by "turbulence". to reduce 

the laminar boundary-layer in water. 

An aluminum disk (AA 6061. 1%" dia. X 1" thick) is heated red-hot 

(1650" F); it melts to a "pancake" in the furnace, exhibiting a Siack 

alumina coating typical of "emery paper" (used for metallograpby 

grinding). A second A1 disk is "soiutionized" (990" F, 532"1?) and 

quenched quickly in the pail of water (70°F). We can predict how long 

it takes to stop sizzling, so the disk is not too hot to hold 

(threshold of pain is 140°F, 60°C). Use RQF = Q of A1 + Q of steel, 

where Q= Cp Xfl X t: i.e., (Btu/lbiF0)times(lb/ft3)(ft3)(F")=Btu. 

Thus, RQF = (0.215) (170 X 1.77) (990 - 70) = 2 X 1 X 1 X 2 = 3. 

(0.110) (480 1.571 (1650-70) 1 3 1 3 9 

Assume a constant 70" F in a 5-gal water pail. Note how voli~mes of 

dislcs (q in cubic inches will cancel, so conversion to cu :ft is not 

needed. 

It will take the A1 disk about 4 X 30 sec = to cool. 

2. Furnace Calibration Test (FCTI 

Assume the heat-treating shop wants to check the furnace controls 

(temperature control. thermocouple, and readout) every shift. The 

"suggestion - box" brings a test proposal for $100 award: Drop 

10-disks of red-hot steel in 1-gallon water bucket and measure the 

temperature-rise, with stainless-dial thermometer. The foreman fears 

a steam explosion. Do we O.K. the test? Assume a heat-balance and 

neglect losses. 

Say Q out of steel = Q into water; where Q = Cp XFXAt : the Q 

is "absolute value" of heat; and t is final temperature of ten-cold 

disks or a warm gallon (8.33 lb). Therefore, 

0.11 (10 X 480 X 1.57/1,728) (1,650 - t) = 1.0 (8.33) (t - 70) 

SO, 0.4797 (1650 - t) =8.33 (t -70) SO, 

7.85 t = 1374.6, and 

We conclude the water won't boil, the test is simple and safe. and 
r-e 31GCi award is well deserved. Of course. the -. men 'have already :-un 

the ?;st,, a disk 3 tjme. and know it is (2.;. 3.n slsgan~ t ;> - ??. --. ~ii~ljdyilsmi c;s ;.qi-~at irr;~~ says ',! in = - i_! (jut , with tr;'iflpek-.ar?~re 

?:iff eren~:es exrjr-essed as "final-orisina1." c>(~rs weye "hot-!;oldu. 

- ., C .-. 2. .~~ecafic Heat Ca~acitv iwatel-l 

Worldly wisdom says, "a pint's a pound the world around", if it's 

wat?r. Tiiill.: is mostiy water. So, take a pint of milk and heat its 

bottom with a kitchen match (one-Btu). With no heat losses, the miik 

only heats one Fa, a visual proof for 1.z~ of H2.(3 (one Btu per pound 

per F"). No wonder water is used to quench red-hot steel and to douse 

fires. 

Next. visualize a Btu as 778 ft-lb. An 80-lb bag of "softener 

salt", 'carried up 10-steps (1 foot risers) to the mezzanine, can 

injure s worker on the ground floor (800 St-lb is badi. An 80-ib 

cannon-bai 1. dropped ~nn :/our foot (10 ft below) is worse. Holding 

your nand over a wooden match (one-Btuj gives "roast hand", but not 

"roast nilk". This is real energy! 

4. Specific Heat Caoacitv (metals) 

Get sam~ies of 5-common alloys (copper, aluminum. yellow-brass. 

piain-steel; and stainless-steel). ~ll-samples must have the same 

weight (say 5 ounces); it's good to have the same surface area (a 

challenge) but not essential. Take 5-beakers: add ice-water enough 

to cover any sample (aluminum has most volumej; but each beaker must 

have tke same volume of water. 

Mea.nwhile, the metal samples are immersed in a pan of water and 

brought to a boil. Put a thermometer in each beaker; stir and measure 

the "ice-water" temperature; a rugged dial-thermometer is good. Then, 

add a hot sample to each beaker, stir to avoid stratification, and 

read the maximum temperature rise (Ad). Compare with values of Cp 

and Y from a handbook, which snould vary directly with nf - values, 

but inversely with density. Aluminm is lightest, so Cp is largest 

(about 0.215 Btu/lbiF0). Steel and Copper have less iJp (about 0.111. 

5. Thermal Conductlvltv (metals) 

Get wire samples ;say 1/8" dia. X 6" long) of conmon metal alloys 

icopp-r, aluminum, brass: steel, sta~nless) and insert them in your 

"nspe - - holder" (4" - Sched. 40 X 10" long). having radial holes and 

a~r-passages 

Each wlre. wi 

on the outer end. looks 1 ilce 

a 'Q-tlp". Inner ends of wires 

meet at the pipe-center, like 

spokes in a wheel. A burnerflame heats the wlres simultaneously 

{at the hub). 

The wax falls off the copper. 

then aluminum - brass - and steel; 

the stainless steel stays cold. 

Measure the drop-off tlmes by 

stop-watch: compared with handbook 

values for Kqpa (thermal conductivit 

these metals should differ by halves: 

copper 1, aluminum 1/2, brass 1/4, 

steel 1/9, stainless 1/16. No wonder 

PIPE - HOLDER 
aluminum and stainless-steel are hard to weld. Compared to 

plain-steel, aiwxilnum !:onducts too fast, holds heat l[jnq, and 

tends to melt too much; stainless is slow to preheat. hard to pr~neat 

evenly. and tends to warp. 

Notice the "oxide" colors (ranging from yellow to bluej which 

correspond to temperature (430 - 640" Fl. Do not confuse with 

"hot-metal" colors; hot-rolling is "red-hot" at 1650" F: cold-roliing 

is "black-hot" below 1333" F (allotropic transformation. from FCC 

austenite to BCC ferrite). 

Throw in a "ringer" (copper-coated stainless welding-rod) and 

mystify the class, as the waxy tip stays cold indefinitely. 

6. Meltinq Points (Solder) 

Molded balls of solder (60-40 eutectic mix) and component metals 

(lead, tin) are made as "fish-line" weights (with a slot). An 

aluminum plate (say 4" did) is dented with a ball-hammer (3--dents. in 

a triangular pattern). Placed on a ring-stand and heated by 

gas-burner, the balls will melt, but the aluminum plate should not. 

First. the solder bali collapses to a pancake; next, the tin bali; 

finally. the lead ball. Shut off the flame, tap the plate, and watch 

the shimmering "puddles" as they re-freeze. First is the 1ea.d: next 

the tin: finaily the solder. 

Discuss the "eutectic-solder" (for electrical joints) wh,ich 

freezes at a definite.. lowest temperature); compare with "wiping 

solder" (for plumbing joints) which freezes over a ranqe of 

temperatures (like slush). This illustrates the 2-phase mixture of 

liquid and solid solutions, seen on a "binary phase-chart" of Pb and 

Sn. 

7. Expansivity (linear) 

A stainless coffee-pot, fitted with a plastic-lid, may have easy 

clearance (cold) but becomes difficult to remove (boiling hot). 

Compare values of linear expansivity (at) for steel ( 0.000o(a6 iFO 1 

and plastics (0.00006). Visualize expansion of a steel pipe as 6'" 

per million" (16 miles). 

Samples of A1 rod (crp = O.ooo009) easily show expansion and 

contraction. if heated in boiling water (about 140 Fa above 70" room 

temperature) and cooled on dry-ice (about 140" F below 70" F). 

Measuring can be done by a "vernier caliper" (to 0.001", called 

1-mil) or a "micrometer" (to 0.0001"). Be careful of ice-crystals on 

a cold rod, interfering with measurements. Use a machinist's cali~er 

Iwith center-screw adjusrment) like an ice-man's tongs (a "go/na go" 

gage). 

Note area expansivity (a~) is about 2 X at (210%) ; volume 

expansivity (4 is about 3 X (331?6) . When units are cancel led in 

a handbook (in2. / inz., or in3 / in3 ) . we general ly assume 

published values are linear. Nnen In doubt, find out! Remember, 

expansivity is generally measured close to room temperature. For 

red-hot steel, 6 "per million" is too little. 

CONCLUSION: 

The materials lab experiments and demonstrations can introduce 

students to thermal properties, as well as mechanical. The shock of 

"thermodynamics" is alleviated, and electrical correlations with 

thermal properties are enhanced. 
KEY WORDS: hear. wax-k. energy. entnaipy: expansion. cont;-action: 

ionduc1:ion. resistance: 'neat-capacity. hea~-transfer. 

REFERENCES: 

1. Garrison. E. G.. "A History of Engineering and Technolow: Artful 

Methods", CRC Press, Inc., 1991, p. 143. 

2. Kazem, 5. M., and Emshousen, F. W., "introduction to Heat Power: 

MET 220 Laboratory". Learning Systems,. Inc, W. Lafaystte , IN. 

3. ~~j;~b, M,,and Hawkins, ;. A., "Eiements of Heat Transfer". 

3rd ed., Wiley, N. Y., 1957. 

4. Faires. V. N., and Sirnmang, C. M., "Thermodynamics", 6th ed.. 

MacMillan, N.Y., 1978. 

EDWARD L. WIDENER 

Teaches mechanical engineering technology 

at Purdue University (since 1978) . concentrating on statics, fluid 

mechanics, materials, labs and technical 

writi *...Member ASME, ASEE, ASM, TAPPI. 

Registered P.E. in New York and 

Indi =...ABET visitor in 1983-88 ... B.S. 

M.E. from Purdue University and M.S. E.M. 

from the University of -...Taut 

evenings at ~Indianapolis and at 

Danville, IL. Worked as Mechanical 

Development Ehgineer for "Coria" collagen 

casing with Teepak Co., Continental Group 

(1976-78). Process Group Leader for 

mechanical contractor, 

Bake2-McHenry-Welch, Indianapolis, IN 

(1974-76). Project Leader for 

creped-wadding and secondary-fiber3 with 

Kimberly Clark Co., Memphis, TN 

(1968-74). Process Ekgineer for "Mmex" 

nylon with E.I. Wont Co., Richmond, VA 

(196368). Associate Bgineer for 

electro-furnace alloys with Union Carbide 

Co., Niagara Falls, NY (195240). Fuel 

Bgineer with U.S. Steel Co., Gary, IN 

(1951-52) . 
HEAT-TREATING OF MATERIALS 

Edward L. Widener - MET Dept. 

Purdue Unversity, W. Lafayette, IN 

PREREQUISITE KNOWLEDGE: Typical high-school students of math and science should 

understand basic concepts of crystals (solids) and glasses (super-cooled liquids) 

for elements (atoms) and compounds (molecules). 

OBJECTIVES: To introduce those solid-state transformations of material 

structures, known as "heat-treatmentsM.l To emphasize commercial importance of 

common processes for metals as well as non-metals. 

'L 

EQUIPMENT & SUPPLIES: Furnace, torch, or burner (electric or gas) for red-hot 

and re-heated specimens. Buckets (2-5 gallon capacity, say 9-22 litres) for 

water-oil-sand quenches. Grating (expanded-metal, wire-mesh) and firebricks 

(supports) for cooling-table. Stop-watch (or timer) and thermometer (dial or 

glass). Tongs, gloves, and safety glasses. Hammer, wrench, hack-saw, vise. 

Specimens of metals (ferrous and non-ferrous alloys) or non-metals (ceramics .and 

polymers) from ware-house or scrap-pile. 

PAUSE & PONDER: What is the best way to learn a new topic? Start with simple, 

familiar examples? Survey a broad field? Why not do both?3 First, remember the 

blacksmith's dipping red-hot steel in cold-water, because "quenching" is a quick 

way to allotropically harden carbon-steel.4 More broadly, define conventional 

heat-treating as: "controlled heating & cooling of metal allovs, to alter 

properties, in the solid state". Why order "special heats" from melting 

furnaces, needing long-term scheduling of large-tonnage orders in high-energy 

processes at high prices? Solid-state treatments are sooner performed on 

standard stock in small amounts, at market prices with fuel savings, available 

from local suppliers. 

More specifically, define "heat treating" as the controlled heating and cooling 

of metal alloys in the solid-state. Start by "solutionizing", heating above a 

critical temperature and soaking 1-hour per inch, to get a single-phase solidsolution. Then, cool at various rates to anneal (slow), normalize (medium), or 

quench (fast). "Tempering" is merely re-heating, so as to draw brittleness from 

allotropically-quenched martensite, to graphitize malleable-iron from whi.te castiron, or to age a T-6 aluminum or P/H stainless-steel fron quenched supersaturated solutions. "Hardening", the usual objective, may involve workingalloying-carburizing-coating-quenching-or tempering operation^.^ 

STEEL EXPERIMENTS: There are dozens of separate and distinct heat-treating 

operations that may be performed on steel. In this laboratory exercise, only 

four of the commonly used heat-treating operations will be performed, with 

explanations of their purpose and effects upon steel proper tie^.^ 

(a) Anneal - A part is heated to the proper temperature, where the structure 

becomes a single solid-solution of "austenite". After a suitable holding time at 

temperature, the part is slowly cooled, in hot-sand or furnace. This puts the 

steel in a condition having its lowest strength and softest properties. It is 

usually the best condition for machining - or for cold forming the material into 

parts. In slow cooling from red-hot state, austenite transforms into a 

predominately large-grain, lamellar-pearlite, micro-structure. 
(b) Normalize - Has the same austenitic-temperature as for annealing; but, 

after a suitable holding time at temperature, the part is removed from the 

furnace and allowed to cool in still-air. This operation is less costly than 

anneal, produces slightly higher strength and hardness, but often is adequate for 

machining and cold-forming. 

This heat-treatment may provide a uniform metallurgical structure, throughout the 

entire part. The slightly faster cooling of austenite from the normalizing 

temperature still produces a predominately pearlitic micro-structure; but, it is 

somewhat finer lamellar-structure, which contributes to slightly higher hardness 

and strength. 

(c) Quench or Harden - A part is also heated to the proper temperature, where 

the structure becomes a single solid-solution of austenite. It is also held at 

temperature for a suitable time, to provide a homogenous solid-solution. For 

hardening, the cooling rate is all-important. The heated part must be cooled so 

rapidly that austenite does not expel carbon, nor become pearlite, but transforms 

into a wholly new constituent called "martensite". To do this, the rate of 

cooling must exceed a critical cooling rate (CCR) at critical cooling velocity 

(CCV) . 

Martensite is an interstitial, super-saturated, solid-solution of carbon in 

tetragonal body-centered iron. The "diffusionless" transformation from 

austenite-to-martensite results in a volume expansion of 7 to 9%. It is the 

hardest and strongest condition for a given grade of steel, say 60-63 RockwellC(R,). However, in this condition it lacks toughness and is seldom used in the 

as-quenched condition. Additionally, in this hard expanded-volume condition, 

there frequently are high internal-stresses, which may result in cracking or 

shattering, depending upon the shape of the part. The next heat-treatment puts 

martensite into a suitable condition, for engineering applications. 

d) Temper or Draw - This relatively low-temperature operation reduces the 

hardness and strength of martensite, but improves toughness, for a specified 

application. Temperature is between 1350-400°~ (730-205°@2), below the eutectoid 

temperature of the "Iron-Carbon" equilibrium diagram. For each part and 

application, the exact temperature for tempering is variable to provide a 

finished part with proper combinations of hardness, strength and to~ghness.~ 

Since these changes in micro-structure are extremely difficult to evaluate, by 

viewing the changed structure, specify that structure as tempered-martensite of a 

certain Rockwell hardness. 

Laboratorv Exercise: 

Heat treat 5-samples, all of the same grade of steel (say AISI #1040). 

(a) Annealing - Heat sample to 1650°F, hold for 1-hour per inch at 

temperature, shut off furnace, and allow sample to cool in furnace, Check 

and record hardness, using R,- scale. 

(b) Mormalizing - Heat sample to 1650° F, hold for 1-hour at temperature, 

remove sample from furnace, and cool in still-air on a metal-grating. 

Check and record R,. 

(c) Hardening - Heat sample to 1650°F, hold for 1-hour at temperature. Remove 

sample quickly from furnace, plunge in cold water and agitate during the 

cooling, to get an effective quench without insulating steam bubbles. 

Check and record R,. 
(d) Tempering - After recording the hardness of quenched sample (c) ;hove, 

place in furnace and temper at 900° F. Hold for 1-hour at temperature. 

Remove from furnace and air-cool. Check and record R,. 

(e) Drawing - Heat sample to 1650°F, hold 1-hour, then quench 1" of the end. 

File off black mill-scale, watch for blue-oxide color being "drawnw to 

silvery tip, and then quench to stop re-heat. Check and record R.,., 

ALUMINUM EXPERIMENTS 

Several metal alloys (mainly non-ferrous) can be hardened and strengthened by a 

2 -step process : 

a) Solution Heat-Treating involves heating-soaking-quenching. 

b) Precipitation Hardening includes natural aging (air) or artificiallyaccelerated aging (oven). 

Wrought Al. Allovs - The "Aluminum Association" has a &-digit system to designate 

various structural materials, from #1000-7000, plus tempers (F, 0, H, W, T) 

followed by 1 or more digits. HArdening mainly involves the 2000, 6000, and 7000 

series. Cast Al. Allovs are similar, but designated with 3-digits, a decirna,l 

point, and 4th digit. 

Commonly alloyed with Aluminum are Cu, Mg and Si, whose "solid-solubilities"" are 

greater at hi-temp (vs. room). Thus, an alloy is heated to maximm-solubility, 

then quenched (rapidly cooled) to become temporarily a super-saturated solidsolution at room temperature; i.e., the solution has dissolved more alloy-element 

than normal for equilibrium conditions. Such state can be maintained (or 

prolonged) by refrigerated storage. However, if allowed to "age" naturally (at 

room temp.) or "artificially" (at oven temp.), the alloy can precipitate small 

crystals of "inter-metallic compound". Visible only by electron-microscope 

(S.E.M.), these particles act as "keys" at inter-granular boundaries and slipplanes. The product is harder and stronger. 

Select AA alloy #6061-T6 (formerly #6lS), composed of Al-Mg-Si, commercially 

heat-treated and formed into bar-stock, 1.5" dia (say 4 cm). Cut samples 

approx. 1" long (2.5 cm). Demonstrate basic processes, such as: 

a) Full Anneal - To insure all samples'start with uniform softness, preheat 

the furnace to 532OC for 1-hr; then heat samples for 1-hour, shut furnace 

off, and let samples slowly cool to room temp. (about 12-hrs inside 

furnace). Measure hardness. 

b) Normalize - Remove solutionized sample from 532OC furnace; let cool on 

grating in still-air to room temp. (about 23O~). Measure hardness. 

c) Solution Heat-Treating - Samples heated to 531OC and soaked 1-hr.; then 

fast-quenched in water to room temp., and immediately tested for ha1:dness. 

d) Natural Aging - Store quenched samples at room temp., and regularly monitor 

the increasing hardness. Check with references for ~'6061-alloy to 

estimate the optimal-aging period (6-12 months) at room temp. 

e) Artificial Aning - Three quenched samples of known hardness (from Test 'kc"') 

are reheated (tempered) to 200°C for 20-40-60 minutes; then'bquencg.B" in water 

to room temp. and measure hardness. Check ASM Metals Handbook (Ref. 5, 

Vol. 11) for optimal time, hardness and strength. Rockwell may exceed 50 

Rc . 

=:Ferrous alloys (Fe over 50 w/o) are typically used for "allotropic 

quenching"; however, consider an "alpha-beta" titanium alloy (Ti 6 Al - 4 V) for 
precipitation-hardening (solutionize at 95OOCI, quench in water, age at 540%) 

Common allotropic-metals include: Co, Cr, Mn, Ni, Sb, Sn, Ti, W, Zr. 

Always define "percentages"; e.g., w/o by weight, v/o by volume. Always 

check hardness (or strength) of fresh (as-is) specimens, to establish a "benchmark" (control standard) before heat-treatment. 

Samples are usually steel (AISI #lo10 - 1080; 4340) or aluminum (AA #6061; 

2024) sliced from 1-1/2 to 2" dia. bars (say 3-5 cm). However, scrap-metals are 

cheap and disposable: springs, paper-clips, hacksaw blades, razor blades, streetsweeper tines, pallet-straps. For typical "soaking" (1-hr per in, 2.54 cm) a 

thin specimen (l/l6", 1.5 mm) needs only 4-5 minutes (depending on reflectivity) 

to "solutionize" in the solid-state.. Surface sanding is avoided, unless microhardness (Vickers, Knoop) is tested. 

To show property differences (from various treatments), the usual tests are 

tensile-pulls or macro-dents, which require descaled ends (coupons) or surfaces 

(disks, blocks). However, consider "Mohs" scratching (sawing or filing) or a 

drop-weight (Brinell-ball through glass-tube) with Brinell-scope (20x). 

Magnetic tests are appropriate. Use a magnetized screwdriver, file-cabinet 

clip, or recipe-holder to show "ferro-magnetism" of steel, nickel, or cobalt 

specimens. Austenitic stainless-steel is usually not magnetized (contaminated 

welds may become ferro-magnetic). Black mill-scale (Fe3 04) is strongly "ferromagnetic"; so, cleanup around hot-rolling mill, heat-treating furnace, or 

blacksmifh-shop is easy. Of course, red-hot "austenite" (gamma iron) is not 

ferro-magnetic. 

With small metal-barstock, twisting tests are fast and effective. Mount a 

heat-treated bar (square or hexagonal section) in a vise, and twist 90° by wrench 

(torque-wrench is better). Note differences in "stiffness" between the annealed, 

normalized, quenched, tempered specimens. Note the 90° return-twist is stiffer 

(annealed, normalized bars) or makes cracks (quenched, tempered bars) and gives 

higher torque-readings (work-hardening). Such testing also averts descaling or 

smoothing steps. 

Tines, lying in the street (after curb-sweeping) are hi-grade spring steel. 

Fresh samples are available from maintenance shops (after brush-change). After 

heat-treating, each tine can be vise-gripped and sharply-flexed (90° to and fro) 

from vertical. A slight pull is needed, to concentrate bending at one spot (as 

metal work-hardens). Annealed tines may take 20-flexes, tempered "as-is" tines 

take 3, and quenched tines only 1/2 flex. More tests are done, in less time. 

Furnaces are often too costly, bulky, hot, slow, and unreliable. Our labs, 

for 10-20 yrs., have successfully used dual-box units (440V oven, llOV control) 

with inter-changeable base (temp. range) and bench size (2'x 2' x 3' ~learance)~ 

However, with thin samples, a gas-welding torch or bunsen-burner is adequate for 

demonstrations. Cooling in a furnace (slowest), then in air (slow), one might 

assume "sand-burial" to be moderate (slower than air). Students are surprised to 

find cold-sand (room temp.) gives a mild "quench" and more hardness than airnormalizing. So, heated sand (100-20092) is needed, to better approach a "fullanne al " 
Moreover, students are surprised, when "tool-steel" is hardened by an "airquench", because hi-alloy content slows the transformation-cooling rate and 

avoids "normalizing." 

Plastic sheets, such as poly-carbonate (G.E. Lexan) or Acrylic P19l 

(DuPont Lucite, or Rohm & Haas Plexiglas) can be "stress-relieved" at lowtemperatures (say 100-40O0C, plus 4-day slow-ceoldown). Examine a tensile-coupon 

by polariscope to check results (no colored fringes,in unstressed photoelasticity specimens). Melt-and-burn tests are also worth exploring, with common 

"ethenic" plastics .@ 

CONCLUSION: 

With multiple lab-sections and repetitious testing, the materials lab has 

the opportunity of accumulating data (for several semesters) to run linear 

regressions, get dimensionless plots, or make a statistical analysis-ofvariances. Studying trend-lines and correlation-coefficients will enhance 

comparisons : 

a) Hardening vs. softening processes. 

b) Cooling efficzency of quenchants (water, oil, sand). 

c) Carbon content of steels. 

d) Ferrous vs. nonferrous alloys. 

e) Metals vs. non-metals. 

f) Cooling efficiency of water-oil-sand quenchants. 

Virtually all materials (metals, ceramics, polymers) are being commercially 

heat-treated. Materials lab experiments can expand beyond metallurgy into 

ceramic-glass tempering, refractory curing, thermoplastics manufacturing, thermosetting, composites fabricating, repairing and maintaining. 

REFERENCES: 

I.,- Widener, E.L., "Materials Labs: MET 141 Packet #X7", Kinko's Copies, 720 

Northwestern Avenue, W. Lafayette, IN, 1991, pp,47-55. 

2.-- Lindberq Furnaces (Div.of Gen.Signal - was Sola Basic), types 5144:2/59344, 

1200°e max., 304 Hart Street, Watertown, WI (530941. 

3.,, Jacobs, J.A., and Kilduff, T.F., "Engineering Materials Technology", 

Prentice-Hall, Englewood Cliffs, N J , p. 155. 

4.-- Fellers, William O., "Materials Science, Testing, and Properties for 

Technicians", Prentice-Hall, Englewood Cliffs, NJ, p. 154 

5.,- American Society for Metals, "Metals Handbook: Ninth Edition", Publ.. by 4 

Society for Materials (ASM) International, Materials Park, OH (44073): 

Vol. I - "Properties & Selection: Irons & Steels", 1978. 

Vol. I1 - "Properties & Selection: Nonferrous Alloys", 1979. 

Vol. I11 - "Properties & Selection: Stainless, Tools & Specials", 1980. 

Vol. IV - "Heat Treating", Alban-Easterday-Zamborsky (Ed.), 1981. 

6.,, U.S. Steel, "The Making, Shaping and Treating of Steel", 9th ed., H.E. 

McGannon (Ed.), Herbick & Held, Pittsburgh, PA, 1971, Index pp.1360-1361. 

7.,- Bain, E.C., and Grossmann, M.A., "Principles of Heat Treatment", 5th ed., 

A.S.M., Materials Park, OH., 1964, p,129. 

8.-, Widener, E.L., wBurning Plastics: For Fuels or Fools", Proceedings, ASME 

Hydrocarbon-Processing Symposium (ETCE), PD-Vol 28, 1990, p.13. 
MEASURING THE SUWACE TENSION 

OF SOAP BUBBLES 

AND 

MEASURING THE WEIBULL MODULUS 

OF MICROSCOPE SLIDES 

Carl D. Sorensen 

Department of Manufacturing Engineering and Engineering Technollogy 

435 CTB 

Brigham Young University 

Provo, Utah 84602 
Measuring the Surface Tension of Soap Bubbles 

Carl D. Sorensen 

Brigham Young University, Provo, UT 84602 

Key Words 

Surface tension; surface energy; bubbles; soap films. 

Prerequisite Knowledge Required 

Students should probably have completed high school, although this is feasible for 

advanced high school students. The concepts of surface energy and surface tension should 

have been explained. 

Students should be taught how to do a force balance on a hemispherical bubble, with 

the pressure inside the bubble balanced by the surface tension force at the equator of the 

bubble. 

Objectives 

* Students will gain an understanding of surface tension. 

* Students will see that the pressure inside a small bubble is larger than that inside a large 

bubble. 

These concepts can be used to explain behavior of liquid foams as well as precipitate 

coarsening and grain growth. 

Equipment and Supplies 

Commercial soap bubble solution 

* Water colored with food coloring 

* A basketball inflation needle or hypodermic needle with the end ground off 

* Approximately two feet of clear vinyl tubing with an inside diameter of at least 1/4 in. (1/4 

inch tubing works very well for use with a ball inflation needle 

Masonite or pegboard, made into a stand as shown below 

Two six-inch machinists' rules or fine graph paper 

A small watercolor paint brush 

Syringe or eyedropper to add fluid to the manometer 

Toolmaker's microscope or fine wire or drills to measure the inside diameter of the needle 
Set up the U-tube manometer with the needle pointing down. Pour a quantity of 

colored water into the manometer. Adjust the rules so the liquid level in the tubes is at the 

same pllace on both rules. 

Dip the paintbrush into the bubble solution. Wipe the brush across the end of the 

nedle ito put a soap film in place. Periodically rub the brush against the side of the needle 

so fresh bubble solution can continue to drip down the needle. 

With an eyedropper, slowly place colored water into the manometer. Because of the 

surface tension of the soap film, you will notice a higher pressure on the needle end of the 

manometer. Continue to add water, noting the height of the fluid on each scale. 

Eve:ntually, a bubble will form at the end of the needle, and the pressure measured by 

the manometer will suddenly decrease. Record the maximum pressure indicated. Also, 

estirnatle the size of the bubble and record the pressure. 

Continue to add fluid to the manometer. The bubble will continue to grow. Record the 

bubble diameter and pressure at two or three different bubble sizes. 

When the bubble pops, repeat the procedure two to three times. Record all data on the 

data sheet. 

Empty the fluid out of the manometer. Using a drill or a toolmaker's microscope, 

measmje the hole diameter of the needle and record it on the data sheet. 

Since the soap bubble has two sides, the pressure difference between the inside and 

outside of the bubble is given by the formula 

where y is the surface tension of the soap film and r is the radius of the bubble. The 

pressure outside the bubble is atmospheric; the pressure inside the bubble is atmospheric 

plus the additional pressure of the water in the manometer tube. The additional pressure 

due to the water is given by 

wh~ere p is the density of the fluid, g is the acceleration of gravity, and Ah is the height 

dzference between the two sides of the manometer. If we consider that atmospheric 

pressure is acting on both the inside and the outside of the bubble, it is clear that AP is just 

PWate,. We can calculate Pwate, either from equation (2) or by using conversion factors: 

1 atm = 406.8 in H20 = 14.7 psi = 101.4 kPa (3) 

73-11: bubble forms on the end of the needle when the bubble has the same radius as the 

inside of the needle. The surface tension, then is calculated from 
where AP,, is the maximum pressure difference recorded. 

A second way to measure y is to make a plot of AP vs. 4/r. The slope of the line is y. 

Measure the outside diameter of the drill. Based on your calculation of y, can you 

predict the heaviest bubble that will hang on to the end of the needle? Can you think of a 

way to measure the weight of a bubble? 

Sample Data Sheets 

Inside diameter of needle: 0.052 in (1.32 mm) 

Outside diameter of needle: 0.080 in (2.03 mm) 

Surface tension from maximum pressure difference: 

Instructor Notes 

The U-tube manometer is made from masonite and vinyl tubing. A rectangular piece of 

masonite is cut; a second piece is hinged to the back to provide a stand. The tubing is 

wired in place with twist ties, other soft tie wire, or small nylon cable ties (available at 

Radio Shack or other electronics suppliers). Machinists scales or strips of fine graph 

paper are used to provide a reading for the manometer. See Figure 1 for details. 

Alternatively, a commercial manometer may be used. However, most manometers do 

not have scales as fine as a machinists rule. 
A fluid with a lower density than water could be used to give larger readings. 

However, my experience is that low density fluids are either toxic or oily, so the problems 

they cause are not worth the benefits they bring. 

The relationship between the radius of the bubble and the surface tension is found by 

considering equilibrium of a half bubble (Figure 2). The upward force is provided by the 

pressure and has a magnitude of m2AP. The downward force is provided by the inner and 

outer surfaces of the bubble; it has a magnitude of 2(2nry). Equating the two forces and 

solving for AP gives equation (1). 

Figure 1: A sketch of the U-tube manometer. Details of the tube are 

omitted from the top and side views. The stand that holds the manometer 

vertical is hinged for storage. The vinyl tube is attached to the masonite 

background with soft wire. The needle must be placed far enough away 
nr2AP 

Figure 2: The forces acting on a hemispherical soap bubble in 

equilibrium. 

References 

Boys, C.V., Soap Bubbles, Their Colors and the Forces Which Mold Them, New 

York: Dover Press, 1959. 

Cassidy, John, with David Stein, The Unbelievable Bubble Book, Palo Alto California: 

Klutz Press, 1987. 

Source of Supplies 

Supplies are readily available at hardware or discount stores. 
Measuring the Weibull Modulus of Microscope Slides 

Carl D. Sorensen 

Brigham Young University, Provo, UT 84602 

Key Words 

ics, fmture test, Weibull statistics, modulus of rupture, glass, bend test. 

Prerequisite Knowledge Required 

Students should have completed a strength of materials course, or be familiar with the 

concepts of stress, strain, bending moments, shear force, and free body diagrams. In 

addition, students should appreciate that ceramics are brittle materials that are fundmenally 

different than metals. 

Objectives 

Students will come to understand why a three-point bending test is used for ceramic 

specimens. They will learn how Weibull statistics are used to measure the strength of bittle 

materials. They will appreciate the mount of variation in the strength of brittle materials 

with a low Weibull modulus. They will understand how the modulus of rupture is used to 

represent the strength of specimens in a three-point bend test. In addition, students will learn 

that a logarithmic transformation can be used to convert an exponent into the slope of a. 

straight line. 

Equipment and Supplies 

Glass microscope slides, 25 mm by 75 mm by 1 mm (thicker slides will also work, tl~inraer 

slides are unreliable) 

* Three-point bending mechanism, which is described in the Instructors Notes 

a Materials testing machine with a compression load cell or other method of applying a 

measured force 

* Micrometer or vernier caliper for measuring the microscope slides 

* Calculator with natural logarithm function or preferably a computer spreadsheet for 

reducing the data. 

Procedure 

Each group of students is given 25 microscope slides. A representative slide is selected 

and measured to determine the width and thickness; the three-point bending fixture is 

measured to determine the separation of the outside rollers. 
Be sure you are wearing your safety glasses. Place a slide in the test fixture. Place a 

shielcl of flexible material around the fixture to catch any flying glass. Gradually increase the 

load on the slide until the slide breaks. Record the fracture load. Repeat this procedure with 

the rest of your slides. If you get extremely low or extremely high fracture loads, don't 

assume them to be in error. This is a common feature of ceramics' fracture strengths. 

Ike raw data has now been collected; the remainder of the lab consists of analyzing the 

data. Students have found it very helpful to use spreadsheets to complete this analysis, as 

nearly all the calculations are repeated for each of the slides. 

Sort the fracture forces in increasing order. Assign a survival probability to each force. 

Since: all but one of the slides survived the minimum breaking force, the probability of 

surviving that force is 24/25 or 0.96. Similarly, the probability of surviving the next lowest 

force is 0.92, and so forth. Since no slides survived the highest breaking force, the 

expe~imental probability is 0, but to avoid dividing by zero in future steps, you should use a 

value of 1x10-6 instead. 

For each fracture load, calculate the maximum tensile stress in the slide according to 

equation (1) 

where P is the applied load, d the separation between the supports, w the width of the 

slide,, and h the thickness of the slide. 

The mdulm of rupture is defined as the maximum tensile stress in the slide for a 

survival probability of 50%. The modulus of rupture can now be estimated from the data. 

Record this answer in your lab book. 

'The Weibull modulus shows up as the exponent m in equation (2) 

,where om, is the maximum tensile stress in the bend specimen, V is the volume of the 

bend specimen, and o, and V, are constants of integration. To determine the Weibull 

modulus, we must take a natural logarithm of both sides of equation (2). As we can see in 

equation (3), if we make a plot with In(@ on the horizontal axis and ln(ln(l/Ps)) on the 

vertical axis, the data should fall on a straight line with a slope of m. The intercept of the 

straight line is the term in brackets; this term is not physically useful to us. 

Transform the stress and survival probability calculated above as suggested by equation 

(3). To obtain the Weibull modulus, there are a number of ways to proceed. You could plot 

the bransformed data and fit the best straight line through by eye, then measure the slope of 
that line. You could enter the data into a calculator that perfoms linear regressions and let it 

calculate the slope for you For those who are farnilia with spreadsheets, most spread:sheers 

have functions that will automatically pedom the regression for you. However you do it, 

you should generate a plot and measure a slope. 

If your data is ideal, the plot will be finear. Hoevever, the very weak and very swcbng 

slides usually have incorrect survival probabili~es, so the tails of your graph will be 

nonlinex. It is usually best to calculate the slope based on the middle portion of your data. 
Modulus of Rupture: 16.0 ksi 

Vdeibufl Modulus: 4.5 

%or Microscope Slides 

Intercept = -50.4 

Inlsrtlr~actor Notes 

The three-point bend fixture used need not be very strong; the maximum load is less 

than 15 pounds. However, for good results the support rods must be parallel, so the fixture 

should be machined, preferably from aluminum or steel. The diameter of the support rods is 

not criitical; we have used rods ranging from 15 mrn down to 3 mm with no noticeable effect 

on the results of the experiment. Cold-rolled steel round stock need only be cut to length to 

prcavid~e adequate supports. 
When the slides break, it is not uncommon for glass to fly up to a meter. It is essential 

that guards be in place to contain the glass fragments. For cleanup, a shop vacuum provides 

a safe method of collecting the shards. 

Few materials textbooks provide any discussion of Weibull statistics; reference 1 is a 

notable exception. Because this is not in the textbooks, I have found it necessary to hand 

out the background information below. 

BACKGROUND 

Metals and most polymers are ductile materials; they readily deform plastically (or yield) 

under high loads. In contrast, ceramics are brittle materials; the first evidence of permanent 

deformation is usually fracture of the specimen. This difference causes fundamental 

differences in the behavior of the tensile strength of the materials. 

Tensile strength in ductile materials is limited by bulk properties of the material. This is 

because the material will yield locally around any microscopic flaws, preventing rapid 
fpacrure,. In contrast, strength in ceramics is determined by the microscopic flaws found in 

the speicimen, as cracks will run rapidly through the bulk of the material since no local 

yielding occurs. 

When the strength of a material is limited by flaws, standard methods of reporting the 

sirengd~ are inadequate. To obtain accurate predictions of the strength of brittle materials, 

special statistics known as Weibull statistics are used. These statistics recognize that flaws 

are likely to be evenly distributed through the specimen and that the probability of having a 

large flaw depends on the volume of the specimen. Thus, a large specimen is weaker per 

unit vojume than a small specimen. 

mibull Statistics 

Since each ceramic specimen will have a unique distribution of flaws, each specimen 

will have a unique strength. Thus, statistics are necessary to describe the strength of an 

untested specimen; we can only state the probability that a specimen will survive. 

The fundamental equation for the probability of survival of a specimen is given by 

where Ps is the probability of survival of the specimen, o0 and Vo are constants, 

cs(x,y,z) is the stress at a point (x,y,z) in the specimen, m is a constant known as the Weibull 

modulus, and the integral is evaluated over the whole specimen. Vo is the volume of a test 

specimen that is placed under tensile load; oo will be evaluated later. 
The Weibull modulus of a material is the exponent m in equation 4. Figure 3 shows the 

effect of m on the survival probability of a specimen. Note that as the Weibull modulus 

increases, there is less scatter in the breaking strength; we have more confidence that the 

specimens will survive at loads near the breaking strength. 

Uniaxial Tension 

Consider a specimen that is loaded uniformly in tension. In this case, the stress is 

uniform in the specimen, and equation (4) evaluates to 

ln(1ps) = (~rz (5) 

When we are testing a specimen, V is equal to Vo; for other parts, V will be larger or 

smaller than Vo. When V=Vo, the probability of survival can be determined: 

We can determine the probability of a specimen surviving a stress of oo by substituting 

cr, for o. FOR CASE OF UNIAXIAL TENSION, 

Ps(o=oo) = lle = 0.37 (7) 

Note that equation (6) describes a distribution with two parameters, oo and m. m is 

known as the Weibull modulus, and describes the scatter inherent in the strength of the 

material. oo determines the position of the distribution, and is related to the strength of the 

material. We normally do not consider oo to be the strength of the material, however. This 

designation is reserved for the stress that has a survival probability of 50%. 

Three-Point Bending 

We don't normally test brittle materials in tension. The stress concentration near the 

jaws of the testing machine causes failure at the jaws, rather than in the gage section. 

Instead, we load specimens in bending. There are a number of different bending tests; vve 

will use the three-point bend test. 

In the three-point bend test, a rectangular coupon is placed on two rollers spaced a 

known distance d apart. A third roll applies a load midway between the two support rolls; 

this places the specimen in bending (see Figure 4). In bending, the material above the 

neutral axis is loaded in compression, while the material below the neutral axis is in tension. 

Another commonly used bend test is the four-point bend test, where two rollers 

separated by a bit less than d are used to apply the load. The four-point bend test creates a 

more uniform stress distribution in the specimen, and thus is less sensitive to the location of 

flaws within a single specimen. Therefore, fewer specimens need be tested to obtain the 
properties of the material. However, the same infomation is available from the three-point 

bend test. We will use the three-point test because of its simplicity. 

Brittle materials generally have much higher compressive strengths than tensile strengths 

(because the cracks tend to close in uniaxial compression). Thus, we will consider only the 

 portion^ of the specimen in tension to be under load in the bend test. (Note that the material 

outside the bottom rollers is unstressed.) Unlike the tensile specimens, the stress varies with 

position in the bending specimen. Thus, before we can evaluate the integral in equation (4), 

we must determine the stress as a function of position. 

Consider a free-body diagram of half the specimen, as shown in Figure 5. The external 

loads and moments are not shown in the figure; this is left as an exercise for the reader. 

By cutting a specimen at a distance x from the right-hand roll, we can determine the 

bending moment M at any position along the length of the specimen. 

M = xP/2 (8) 

Stress in the specimen is independent of the width direction but varies in the thickness 

and length direction according to the equation of stress in pure bending (neglecting the shear 

force). 

where M is the bending moment as given by equation (8), z is the distance from the 

neutral axis, and I is the moment of inertia of the cross section of the specimen (bh3Il2 for a 

rectanslar cross section). If we substitute d/2 for x and h/2 for z in equations (8) and (9), 

we can obtain an expression for the maximum stress in the specimen. 

Pdh 3Pd 

omax =--- 81 -2wh2 
We can substitute equations (8) and (9) into equation (4) to determine the probability of 

survival for an applied load P. Solving equation (10) for P and substituting the result into 

the solved integral gives us the final expression for the probability of survival 

The stress omax that will cause the probability of survival in equation (1 1) to be 50% is 

known as the modulus of rupture; this is the strength index determined by the three-point 

bend test. 
In uniaxial tension, we found that 37% of the specimens would survive a load of oo. If 

we set om, to oo in equation (8) and assume m=10, we can determine the probability that a 

specimen will survive a bending load of o,, 

Ps(~=~o) = 0.9959 (12) 

Determinin~ the Weibull Modulus 

Consider the case of uniaxial loading as given by equation (5). ant to determine 

rn, which appears as an exponent. To eliminate exponents, we commonly take the logarithm 

of both sides 

If we make a plot with ln(o) on the horizontal axis and In(ln(l/P,)) on the vertical axis, 

the data should fall on a straight line with a slope of m. This allows us to readily determine 

the Weibull modulus. The same transformation can be applied to the bending specimen; the 

slope will remain m but the intercept will change (try it yourself to see). 

References 

1. Ashby, M.F. and D.R.H. Jones, Engineering Materials 2: An Introduction to 

Microstructures, Processing, and Design, Pergamon, 1986, pp. 169- 177. 

Source of Supplies 

Microscope slides can be obtained from any scientific equipment supplier. Micrometers 

or vernier calipers are available at machinist or industrial supply houses. Three-point bend 

iixtures are available from the manufacturers of material testing machines. 
Compilers: James E. Gardner-NASA Langley Research Center, 

Nampton, TJA; James A. Jacobs-Norfolk State Universitv. Norfolk. VA: 

NASA Langley Research Center 

Nampton, VA 23665-5225 

REPORT NUMBER 

National Aeronautics and Space Administration Washington, DC AGENCY REPORT NUMBER 

205460001; Norfolk State University, Norfolk, VA 23504; NASA CP-3151 

National Institute of Standards and Technology, Gaithersburg, 

MD 20899; United States Department of Energy, Oak Ridge, TN 

37831-6132 

11. SUPPLEMENTARY NOTES 

Supporting Organizations: ASM International; Battelle Pacific Northwest Laboratory; 

Materials Education Council - 

Unclmsifi~ed - Unlimited 

Subject Category 23 

ollection of experiments presented and demonstrated at the National Educators' 

at the Oak Ridge National Laboratory on November 12-14, 1991, in Oak Ridge, 
SPECIAL FOURXH-GLASS RAE 

POSTAOE L FEES PAW 

NASA 

Permls No. 0.27 I