reference

NBS

PUBLICATIONS

A 11 ID 2 L3DaflS

/Institute (or Materials Science and Ena QC100 .1156 NO.86-3434 1986 V19 C.1 NBS-P

I institute tor Materials Science and Eng ineeri ng

NONDESTRUCTIVE

EVACUATION

NBSIR 86-3434

U.S. Department of Commerce

National Bureau of Standards

- QC

100

• U 5 6

88-3434

1987

o «

O

o

Technical Activities

1986

o o
One of several possible models of the liquid jet break-up process that takes place during the production of rapidly solidified metal powders

by the inert gas atomization of liquid metal. Process models of this kind constitute an important part of the knowledge base which is needed in the development of an automated materials processing

facility. See the report, “Sensors for Metal Powder Atomization

Systems,” by S.D. Ridder, F.S. Biancaniello, H.G. Semerjian and

G.E. Mattingly.
N3S

RESEARCH

:r »Bt INFORMATION

Sfc CENTER

t aeP Lsb „

Afe12~

CLlioo

Institute for Materials Science and Engineering

fio.S

NONDESTRUCTIVE

EVALUATION

H.T. Yolken, Chief

L. Mordfin, Deputy

NBSIR 86-3434

U.S. Department of Commerce

National Bureau of Standards

Technical Activities

1986

TECHNICAL ACTIVITIES

Certain commercial equipment, instruments, or materials are identified in this report in order to adequately specify the

experimental procedure. In no case does such identification

imply recommendation or endorsement by the National Bureau of

Standards, nor does it imply that the materials or equipment

identified is necessarily the best available for the purpose.

iii
TECHNICAL ACTIVITIES

Table of Contents

Introduction 1

I. NDE FOR CERAMIC AND METAL POWDER PRODUCTION AND CONSOLIDATION

Nondestructive Evaluation of Alumina Materials with Small Angle

Neutron Scattering (SANS) 4

- K. A. Hardman -Rhyne and N. F. Berk

Near- Surface Characterization of Ceramics by Thermal Waves 5

- G. S. White, L. J. Inglehart and E. H. LeGal LaSalle

Characterization of Ceramics by Ultrasonics 7

- G. V. Blessing and M. P. Jones

Sensors for Metal Powder Atomization Systems 10

- S. D. Ridder, F. S. Biancaniello , H. G. Semerjian, and

G. E. Mattingly

II. NDE FOR BULK METAL PROCESSING

Sensors for Steel Process Control 13

- F. A. Mauer, S. J. Norton, A. H. Kahn, and H. N. G. Wadley

In-Process Ultrasonic Monitoring of Texture in Manufacturing of

Aluminum Product 16

-A. V. Clark, G. V. Blessing, R. B. Thompson, J. F. Smith and

A. Govado

Magnetic Method for Nondestructive Evaluation 19

- L. J. Swartzendruber

Ultrasonic and Optical NDE of Surface Roughness 20

- D. G. Eitzen, G. V. Blessing, T. V. Vorburger, D. E. Gilsinn

and E. C. Teague

III. NDE FOR COMPOSITES AND INTERFACES

Cure Monitoring in Epoxy Resin Composites 26

- F. I. Mopsik, B. M. Fanconi , F. W. Wang, and R. E. Lowry

Interface Effects on Phase Velocities and Attenuation in

Composite Materials

- S. K. Datta and H. M. Ledbetter

IV
Internal Strain (Residual Stress) in Composite Materials 30

- H. M. Ledbetter

Measurement of Flow Birefringence at Microwave Frequencies 32

- A. K. Gaigalas

Guided Interface Waves 34

- E. Krasicka, J. A. Simmons, and H. N. G. Wadley

IV. NDE STANDARDS AND METHODS

Eddy Current Coil Characterization 39

- T. E. Capobianco and F. R. Fickett

Measurement Methods, Calibration Procedures, and Standards

for Quantitative Eddy Current NDE 41

- J. C. Moulder, P. J. Shull, B. A. Auld, and S. Jefferies

Development of Leak Standards and Calibration Facilities at NBS 43

- C. D. Ehrlich and C. R. Tilford

Radiographic Image Quality Evaluation at Very Low and

Very High Energies 46

- R. C. Placious

Standard Test Methods for Characterizing Performance of

Thermal Imaging Systems 47

- J . Cohen

Thermal Waves Visualized by Holographic Interferometry 48

- G. H. Kaufman and C. M. Vest

Theoretical Investigation of Acoustic and Thermal Wave

Scattering 49

- R. D. Mountain

Determination of Green's Functions and Their Application to

Acoustic Emission and Ultrasonics 49

- N. N. Hsu

Performance Assessment of Fluorescence Measurements 53

- K. L. Eckerle, J. J. Hsia, C. L. Chang, and K. D. Mielenz

Military Standards for Nondestructive Evaluation 53

- L. Mordfin

NDE of Shipping Casks for Spent Nuclear Fuel 55

- D. G. Eitzen, R. C. Placious, L. J. Swartzendruber and

L. Mordfin

v
APPENDICES

A. NDE Seminars at NBS 58

B. Invited Talks by ONDE Staff 58

C. Publications 59

D. Awards and Appointments 64

E. Principal Investigators 66

r
INTRODUCTION

This report provides brief reviews of the technical activities of

nondestructive evaluation (NDE) that were carried out by or for the National

Bureau of Standards (NBS) NDE Program in fiscal year 1986 (October 1, 1985

through September 30, 1986). Collectively, these technical activities

constitute the Bureau's NDE Program, which is managed programmatically and

administered on a Bureau-wide basis by Office of Nondestructive Evaluation

(ONDE)

During the last several years quantitative NDE has been applied by

industry to the measurement of material properties and characteristics such

as residual stress, texture, and various other microstructural features.

Such applications have been receiving increased attention because of the

nationwide effort to raise the quality of manufactured products. Clearly,

the ability to monitor important material properties and characteristics

during a manufacturing process can often be used to guide or to control the

process and, thus, to help avoid the manufacture of subquality products or materials. In response to these developments, the Bureau's NDE Program has

for a number of years sponsored work on the application of NDE to the

measurement of materials properties and characteristics and more recently

has placed major emphasis on such measurements in regard to on-line

monitoring and process control in manufacturing.

Traditionally, the most common application of NDE is the

characterization of cracks, voids, inclusions, and other kinds of flaws in

materials, components, assemblies, and structures. This usage of NDE is the

basis of modern in-service inspection procedures as applied, for example, to

aircraft, bridges, pipelines, and pressure vessels. Recognizing that NDE

measurements for in-service inspection must be reproducible and

quantitative, a key component of the NBS NDE Program is providing

traceability for NDE measurements to national measurement standards. To

this end, research must be carried out to achieve an adequate understanding

of the physical basis of the NDE measurement techniques and procedures that

require standardization. Furthermore, the results of the Bureau's research

and development work on NDE measurements must be applied to several specific

and meaningful problems in order to demonstrate the validity of the results

and to help disseminate them to the user communities. Thus it is possible

to think of the NDE Program as comprising three type of activities:

research, standardization, and applications.

The reviews in this annual report are arranged in the following major

areas that reflect the four major activity areas of: (1) NDE for Metal and

Ceramic Powder Production and Consolidation, (2) NDE for Bulk Metal

Processing, (3) NDE for Composites and Interfaces, and (4) NDE Standards and

Methods. Each of these sections is preceded by an introduction.

Reports such as this one have been issued on an annual basis since 1978

and are commonly referred to as the "NBS NDE Annual Reports." A parallel

series of reports, also issued annually, presents bibliographies and

abstracts for the Bureau's technical reports and publications on NDE and its

supporting technologies. The purpose of both of these report series is to serve as an introduction to the Bureau's NDE Program. Many readers will
want further details on specific aspects of the work or its outputs, and

such inquiries are welcomed and encouraged, both by the principal NDE

investigators (whose names and affiliations precede each of the articles in

the report) and by ONDE. Either can be addressed in care of NBS

Gaithersburg, Maryland 20899, or reached by telephone via (301) 975-2000.

Requests for further information and suggestions regarding the Program

always receive prompt and careful attention.

2
NDE FOR CERAMIC AND METAL POWDER PRODUCTION AND CONSOLIDATION

This activity is broadly concerned with developing approaches, sensors, and

procedures for nondestructively determining those properties of ceramic and

metal powders, and of consolidated materials, that relate to the quality and

performance of the materials and manufactured parts. The emphasis is on those

measurements which can be made during the manufacturing process to sense the

properties of the product during critical stages of its formation and to

provide the data required to control the process to optimize quality and

productivity. This activity includes: a study of pore size and distribution

in alumina powder materials by small angle neutron scattering (SANS); near- surface characterization of ceramics by thermal waves ; determining the

elasticity of ceramic samples by measuring sound velocities; and investigation

of appropriate sensors for metal atomization powder systems. Although all of

these projects are aimed at developing sensors for the manufacturing process,

the project on metal powders represents the most complete approach to this

end. It involves the development of a process model, the investigation of a variety of sensors, the study of their performance in an actual inert gas/

metal atomization facility, and ultimately the use of an expert system in

process control. This project is viewed as a model system to obtain

experience and insight on how to approach the complete problem of process

sensing and control.

SANS differs from other Nondestructive Evaluation methods in that it requires

a highly specialized facility and certainly is not a candidate for use in the

manufacturing environment. However, SANS provides the scientific

understanding required to develop NDE methods, based on ultrasonic and AC

impedance, which may be used in process monitoring and in-service inspection.

The determination of elastic properties of ceramics by ultrasonics, and

surface properties by thermal waves, has potential for process sensing and inservice inspection.

Representative Accomplishments:

o SANS measurements have shown that detailed information on particle size,

size distribution, and shape can be obtained on undensified Al2 03 powder.

Measurements on a compacted sample and analysis of the data yield particle

volume fractions and porosities averaged over a one cubic centimeter

volume. However, the current theory and analytical techniques which were derived on the assumption of small polydispersivity must be extended to

deal with strongly polydisperse systems and coherent inter-particle interference effects (multiple scattering)

o A study of the porosity of alumina specimens has revealed that thermal

waves propagated through a specimen are more sensitive to changes in

porosity and less affected by surface roughness and optical absorption

variations than thermal waves detected on the front (irradiated) surface.

Other measurements have been made which suggest the effect caused by

inclusions that may have been introduced in the ball-milling of the powder

or in the firing of the sample.

3
o Measurements of Young's modulus and Poisson's ratio by ultrasonic

longitudinal and shear velocities in green-state (unsintered) ceramic

compacts were used to study the effect of a naturally occurring flaw

(calcination) on the elasticity of the sample at three stages of

processing. Samples made from hard agglomerates resulted in low modulus

compacts with a reduced strength compared with samples made from normal,

spray-dried powder. A first step toward in-process monitoring was taken by

measuring sound velocities in the powder during compaction. A patent

disclosure was filed for this in situ sensor technique which is sensitive

to the quantity of binder in the powder, excess moisture, and the rate of

compaction

o Initial work on metal powder atomization was focused on developing a sensing system capable of measuring particle size in real time. To this

end, an atomization system for preliminary fluid flow studies with

surrogate fluids, such as water and low melting-point alloys, was constructed. The apparatus is being used as a model system to establish an understanding of liquid- gas interactions in the atomization process, to

study optimum geometry and jet velocity, and how these variables can be

used to control droplet formation. Several laser scattering techniques

have been investigated for measuring particle size, number of particles per

unit volume, and velocity, although final evaluation awaits tests with

metal particles.

Nondestructive Evaluation of Alumina Materials with Small Angle Neutron

Scattering (SANS)

K. A. Hardman-Rhyne and N. F. Berk

Reactor Radiation Division

Institute for Materials Science and Engineering

It is well known that stress failure of ceramics is strongly related to pore

size and distribution, which depends on the early processing history. To

investigate this correlation we have performed SANS measurements on two

sequences of powder densification, both originating from the same undensified

Alumina (Al2 03 ) powder material. In sequence (1) 500g of 99.99% pure powder

was spray-dried with PVA and glycerol additives to form weakly agglomerated

("normal") material, which was then uniaxially compacted to the green state

and subsequently heat treated to 1000° to form the "bisque." In sequence (?)

the normally agglomerated powder was densified at 1000°C to form solid

("calcinated") agglomerates, and this powder was then taken through the green

and bisque states. The two sequences thus differed only in the nature of

powder agglomeration.

SANS measurements were performed on the undensified powder and the two

processing sequences, at several incident neutron wavelengths in the range of

0.5 to 1.0 nm. Scattering intensities were measured as a function of wave- vector Q (proportional to scattering angle). We have shown that particle si:u

and surface area information can be obtained from analysis of the shape : these intensities at small and at large Q [1,2]. The wavelength dependi tu i characteristic of strong multiple scattering ("beam broadening") which is

interpreted as being produced by the powder particles in the powder sample,

and from the pores of the undensified green compact and the densified

4
material. Analysis of these data give a particle volume fraction of 0.2 and

porosities of approximately 0.47 for the compacted samples. Our analysis

gives values of specific void area in the narrow range 6-7 m

2 /gm, somewhat

smaller than gas absorption results for the normal green compact (20 m

2 /gm)

but closer to the range of some determinations by mercury porosity (10-

15 m

2 /gm). The analysis of size statistics from these experiments is

incomplete, but we have determined that the porosity is strongly polydisperse

in the densified samples, with AR/R > 1.0, where R is the radius of the void

and AR = (<R2 >-<R>2 )* . This apparently reflects a substantial

polydispersivity in the original powder, which we estimate to be AR/R = 1.0.

Significantly, the SANS data from the two processing sequences were

qualitatively and quantitatively similar. Thus, the nature of the powder

agglomeration seems to have little effect on porosity, although it may affect

the "framework" microstructure to which the current measurements are insensitive. We also performed SANS measurements on densified samples, heat

treated near but just below the sintering temperature. We find significantly

less beam broadening, indicating a substantial reduction in porosity.

The current theory and analytical techniques were derived on the assumption of

relatively small polydispersivity. Accurate determination of size

distribution characteristics from strongly polydisperse systems and the

inclusion of coherent inter-particle interference effects into the theory are important problems that we plan to study in FY87.

References

1. N. F. Berk and K. A. Hardman - Rhyne , "Characterization of Alumina Powder

Using Multiple Small Angle Neutron Scattering. I: Theory," J. Appl. Cryst. 18, 467-472 (1985).

2. K.A. Hardman-Rhyne and N. F. Berk, "Characterization of Alumina Powser

Using Multiple Small Angle Neutron Scattering. II: Experiment," J. Appl.

Cryst. 18, 473-479 (1985).

Near-Surface Characterization of Ceramics by Thermal Waves

G. S. White, L. J. Inglehart1

, and E. H. LeGal LaSalle2 Ceramics Division

Institute for Materials Science and Engineering

1 Guest Scientist, The Johns Hopkins University

2 Guest Scientist, Ecole Superieure de Physique et de Chemie Industrielles

Paris

Thermal wave techniques are being evaluated as a possible NDE method to study

ceramics because the types of defects of interest, e.g., pores, cracks,

inclusions, etc., provide discontinuities in thermal properties to which

thermal wave methods are sensitive. The work this year includes construction

of a mirage detection system, study of thermal wave interactions in insulating

materials, [1] continuation of the study of alumina, and investigation of

polishing damage in vitreous silica.

5
The study of porosity in alumina specimens has continued with the mirage

system instead of the photoacoustic cell used previously. Front and rear surface alternating temperature measurements were made while the specimens were heated from the front surface. Comparison with preliminary theoretical

work indicates that measurements of the thermal wave propagated through the

bulk of the material are more sensitive to changes in porosity and are less

affected by surface roughness and optical absorption variations than

measurements made on the front (irradiated) surface of the specimen.

Thermal wave measurements of an alumina specimen have been made which suggest

the presence of inclusions or specimen contamination [3]

Comparison with

optical and electron microscopy and x-ray analysis has shown that the regions

of the specimen in which strong thermal wave signals are present are contaminated with K, Cl, Fe, Si, and other elements. The contamination may

have occurred as a result of the ball-milling of the powder or the firing of

the specimen. These defects averaged about 30 fim in size and were in welllocalized regions of the specimen.

Measurements have been made on optically polished vitreous silica to determine

if residual damage exists which can be detected with thermal waves. Polishing

scratches were detected on some specimens investigated by the photoacoustic

technique. However, measurements made with the mirage technique have resulted

in other signals which cannot be correlated with optical features.

Future plans include continuing the efforts to measure porosity, to detect

residual polishing damage, and to examine the problem of crack detection in

poorly conducting samples, e.g., alumina and glass. While cracks have been

observed in highly conducting ceramics such as SiC, preliminary experiments

suggest that in silica they are difficult to detect thermally even when clear

optically

References

1. L. J. Inglehart and E. H. LeGal LaSalle, "Photo thermal Investigation of

Vitreous Silica," presented at the American Physical Society March

Meeting, March 30 to April 5, 1986, Las Vegas, Nevada.

2. L. J. Inglehart, J. Jaarinen, P. K. Kuo, E. H. LeGal LaSalle, "Probing

Through the Gas-Solid Interface with Thermal Waves: A Study of the

Temperature Distribution in the Gas and in the Solid," to appear in Review

of Progress in Quantative Nondestructive Evaluation 6 . August 18-22, 1986 , LaJolla, California.

3. L. J. Inglehart, E. H. LeGal LaSalle, and G. S. White, "Investigation of

Pressed Al2 03 Disks Using the Mirage Effect," presented at the American

Ceramic Society Annual Meeting, April 28 to May 1, 1986, Chicago,

Illinois

6
Characterization of Ceramics bv Ultrasonics

G. V. Blessing

Automated Production Technology Division

Center for Manufacturing Engineering

M. P. Jones

Ceramics Division and Johns Hopkins University

Institute for Materials Science and Engineering

Since the latter stages of ceramic processing are energy intensive, the

development of techniques for early process fault detection, especially those

suited to on-line applications, are important. This research focuses on those

material parameters which are candidates for quality control in the early

processing stages.

The initial choice for a process-sensing variable is the material sound speed,

a dynamic elasticity parameter. To this end, to make precise measurements of

the shear and longitudinal sound velocities in fragile green- state

(unsintered) ceramic compacts, dry coupling techniques using elastomers were

developed. These techniques [1] were used in studying the effect of a naturally occurring flaw type- -calcination or burning off of binder resulting

in hard agglomerates- -on the elasticity of samples at three stages of

processing: in the compacted green state, after partial sintering in the

bisque state, and after complete sintering in the dense state. Samples made

from normal spray- dried powder were compared with calcined samples made from

the hard agglomerates, which were conjectured to act as elastically uncoupled

particles that would result in low modulus compacts. This was observed to be

the case for the green and bisque samples, but not for the dense samples,

reinforcing the need for fault detection in the early stages of a process.

Subsequent fracture tests revealed a reduction in strength for the dense

samples

A first step toward in-process monitoring was then taken by measuring sound

velocities in the powder during compaction [2,3]. Figure 1 illustrates the

arrangement of transducers used on die shafts acting to couple the pulses of

ultrasound into the powder samples. A patent disclosure has been filed for

this in- situ sensor technique that is sensitive to a reduction of binder in

the powder, the presence of excess moisture, and the rate of compaction.

Figure 2 shows the result of monitoring Young's modulus in-situ on a normal

powder sample, over a wide range of compaction pressures.

Future plans call for ultrasonically delineating porosity from calcination

(especially in the green state)

correlating the ultrasonic results with other

nondestructive and destructive tests, and determining whether the sample

surface structure as measured ultrasonically is a valid parameter for process

control

7
References

1. M. P. Jones, G. V. Blessing, and C. R. Robbins, "Dry-Coupled Ultrasonic

Elesticity Measurements of Sintered Ceramics and Their Green States,"

Materials Evaluation 44, 859-862 (1986).

2 . M. P. Jones and G. V. Blessing, "Real-Time Ultrasonic Nondestructive

Evaluation of Green State Ceramic Powders During Compaction," NDT

Communications, 2, 5, accepted for publication.

3. M. P. Jones and G. V. Blessing, "Ultrasonic Evaluation of Spray-Dried

Ceramic Powders During Compaction," 2nd International Symposium on Nondestructive Characterizations of Materials, July 21-23, 1986, Montreal,

Canada, accepted for publication.

8
Young’s

Modulus

(GPa)

Figure 1. Illustration of die shafts with ultrasonic transducers for sound

speed measurements in sample powders during compaction.

Figure 2. Young's modulus as a function of the applied pressure for normal

and calcined sample powders during compaction.

9
Sensors for Metal Powder Atomization Systems

S. D. Ridder and F. S. Biancaniello

Metallurgy Division

Institute for Materials Science and Engineering

H. G. Semerjian and G. E. Mattingly

Chemical Process Metrology Division

Center for Chemical Engineering

Many of the current "advanced" powder metal products owe their improved

mechanical properties to particular microstructural features obtained by rapid

solidification. Previous work in our laboratories has shown that the type of

solidification microstructure seen in metal powders is strongly dependent on droplet size prior to solidification [1]. These studies showed that droplet

undercooling and, therefore, solidification velocity increases as droplet size

decreases. It then becomes important to monitor and control the particle size

produced during metal atomization in order to obtain the particular

microstructures that are desired.

Our work on metal powder atomization has focused on developing a sensing

system capable of measuring particle size in real time and using this

information in a process feedback loop that would continuously control the

particle size being produced. The approach taken to realize this device

centers on a joint effort between the Institute for Materials Science and

Engineering and the Center for Chemical Engineering, with specific goals in

three separate disciplines. (1) Droplet formation will be studied using high

speed photography with an emphasis on optimizing the geometry of the

atomization hardware. Process variables will be monitored to determine how

particle size varies with gas jet geometry and velocity, metal flow rate, and

type of atomizing as used. (2) Particle size sensing techniques will be

evaluated and an appropriate device for metal powder measurement will be

procured and installed in the Metallurgy Division's inert gas atomization

system. (3) The atomization system will be modified for process feedback

control, for example, by updating the high pressure gas system to allow

computer control of gas pressure. The feedback loop used will depend on results of 1 and 2 above.

This year's accomplishments include the construction of an atomization system

to be used in preliminary fluid flow studies, with surrogate fluids

substituting for high temperature, molten metal, and high pressure inert gas

systems. The surrogate fluids chosen are water and low melting point alloys;

air and other gases can be used for the inert gas. These surrogate systems

will allow initial parameterization and will establish an understanding of the

liquid-gas interactions. The apparatus is currently being used to determine

aspiration pressures developed in the gas jet impingement zone as a func: ion

of gas pressure and the metal stream delivery nozzle geometry. When comp 1

this information will determine not only the optimum geometry and jet

velocity, but how these variables can be used to control droplet formation

This apparatus is also being used to photograph the aspiration and a tom it .-it ioi of water. These investigations will determine what photographic equipm< nt techniques will best show the droplet formation sequence in the model

10
and later in the actual inert gas atomization system. Several point

techniques based on laser scattering have been evaluated for measuring

particle size distribution and velocity [2]. The third technique provides a direct measurement of the particle size distribution, since it is a single

particle measurement technique. It has the added advantage that it also

provides simultaneous measurement of particle velocity.

The study to understand the fundamental phenomena that control the powder

characteristics will continue next year in the small transparent tank system.

Conditions will be modified so as to approach the actual parameters in the

real system. It is expected that these studies will be transferred to the

inert gas atomization system.

References

1. S. D. Ridder and D. Schechtman, "Microstructure of Supercooled Submicro

meter Aluminum- Copper Alloy Powder," in Rapidly Solidified Powders

Aluminum Alloys, ed. by M. E. Fine and E. A. Starke, Jr., ASTM STP 890,

Philadelphia, pp. 252-259 (1985).

2. C. Presser, A. K. Gupta, R. J. Santoro, and H. G. Semerjian, "Velocity and

Droplet Size Measurements in a Fuel Spray," AIAA-86-0297 , paper presented

at the AIAA 24th Aerospace Sciences Meeting, January 1986, Reno, Nevada.

11
NDE FOR BULK METAL PROCESSING

The goal of this activity in the Nondestructive Evaluation Program is to

develop generic approaches, sensors and procedures for quantitative NDE of

metals during processing. The emphasis is on measurements that can be made on the production line to improve process control rather than developing

inspection techniques for post-manufacturing inspection.

Current efforts in this activity include: the development of NDE temperature

sensors based on ultrasonic and eddy current techniques for determining the

internal temperature distribution in hot metal objects; developing an inprocess ultrasonic monitor for metal grain texture in manufacturing of

aluminum products; research on the use of magnetic NDE methods to determine

material properties; and determining the feasibility of utilizing ultrasonic

and optical techniques for on-line monitoring of metal surface roughness during machining. There have been several noteworthy accomplishments in this

activity during the past year.

o Today, many of the complex processes that make up the processing of steel

rely upon intermittent and often inaccurate measurement of surface temperature rather than upon the quantity of fundamental import - the internal

temperature distribution. In a joint research effort at NBS involving NBS

researchers and research associates from The American Iron and Steel

Institute, advances have been made on utilizing ultrasonic tomography to

determine internal temperature distribution and liquid- solid interface

position in solidifying metal bodies.

o During manufacture, the determination of internal temperature distribution

in thin extruded aluminum sections for process control has been a trouble- some problem for the aluminum industry. In a joint effort between NBS and

the Aluminum Association, both theoretical and experimental results have

shown that a multifrequency eddy current measurement approach in the

100 kHz to 1 MHz range appears likely to provide an NDE temperature sensor

for process control.

o A critical part of the manufacturing process for about two billion pounds

of aluminum beverage cans produced annually is control of texture or preferred orientation of the grains. In order to develop an on-line NDE sensor and save an estimated $40 million annually in the United States,

researchers at NBS, Iowa State University, and Alcoa have demonstrated that an ultrasonic technique can monitor texture quickly. Ultrasonic results

obtained with noncontacting electromagnetic transducers were compared to a reference technique utilizing neutron diffraction and qualitative agreement was obtained. Work is now progressing to seek quantitative agreement.

o The determination of surface roughness during machining of bulk metal part

is desirable for both quality control of the finished product and for con- trol of the cutting or grinding process. An ultrasonic sensor has been

developed for on-line monitoring of surface finish during machining of

metal parts. The sensor is noncontacting and utilizes the liquid stream < : cutting- cooling solution as a means to couple the ultrasonic signal to the

metal

12
Sensors for Steel Process Control

F. A. Mauer, S. J. Norton, A. H. Kahn, and H. N. G. Wadley

Metallurgy Division

Institute for Materials Science and Engineering

Today, many of the complex processes that make up the processing of steel rely

upon intermittent, often inaccurate measurements of surface temperature rather

than the quantity of fundamental import the internal temperature distribution.

By utilizing the internal temperature distribution, modern continuous casters

can be controlled to produce optimal material quality commensurate with

maximum casting speed and elimination of breakouts. The benefits of an internal temperature sensor have been estimated as equivalent to over $200M

annually for the domestic industry. Such sensors also have important

applications in reheat furnaces and continuous annealing operations.

The research reported here is aimed at establishing the feasibility of an ultrasonic tomographic approach to the measurement of internal temperature.

The approach is based upon the strong effect of temperature upon the velocity

of ultrasound. For example, a 1°C temperature change at 1000 °C causes a

1 -part- in- 10* velocity change for AISI 304 stainless steel, well within the

scope of today's laboratory instrumentation.

This year's research has progressed on three fronts: application of the

tomographic approach to solidifying bodies, evaluation of a subsurface

temperature gradient sensor, and feasibility studies of an eddy current

approach for thin strip. Progress with each is more fully discussed below.

Internal Temperature Distribution of Solidifying Bodies- -The presence of a liquid domain within a cooling body introduces complications to the

tomographic algorithms used for solidified bodies because of a discontinuous

change in velocity upon melting. It is, therefore, necessary to map the

interface between solid and liquid regions, as well as to determine the

temperature distribution. Several measurement strategies have been identified

for this including: shear wave transmission tomography (molten metal does not

transmit shear waves) , longitudinal wave transmission tomography using an iterative method to locate the solid- liquid interface, and reflection

tomography combined with one of the above. The utilization of simplifying

assumptions, such as uniform liquid temperature and symmetric heat flow

coupled with these modified measurement methods, shows promise of adequately

measuring internal temperature in solidifying bodies.

To experimentally evaluate these various approaches a fully automated 10

channel sensor has been designed, constructed, and is presently undergoing

evaluation. The sensor is based upon measuring the times of flight (TOFs) of

two orthogonal sets of five collinear rays propagating over a cross-sectional

slice of a nominally 6-in. square metal bar. The capability also exists of

simultaneously recording fan-beam TOF values at all ten receivers from each

source. Thus, up to 100 measurements can be made in the time taken to scan

the ultrasonic source over two faces of the bar (about 25 seconds presently)

In the present arrangement an 800-mJ laser pulse is used as a noncontact

ultrasonic source. It is scanned across the bar faces using a system of

13
moving mirrors. Ultrasonic signals at each receiver point are detected with

piezoelectric transducers attached to conical AISI 304 stainless steel buffer

rods (the design of noncontacting EMAT arrays to replace this contact approach

has been completed)

Initial experiments are underway with solidifying aluminum. This system shows some of the physical features expected for solidifying steel, but at lower

temperatures. Aluminum also offers the opportunity of systematically studying

"mushy zone" effects by using Al-Si alloys of varying silicon contents. We

expect to proceed to steel solidification studies by the end of 1986, and to

evaluate, at the high temperatures of solidifying steel, the performance of

high temperature EMAT arrays destined to replace the contact receivers in the

current sensor design.

Subsurface Temperature Gradient Sensor- -The steel industry today makes heavy

use of thermal modeling to predict internal temperature distributions at

various stages of processing. These models have grown in sophistication to

the point where, if accurate heat transfer coefficients are known, the

internal temperature can be predicted to within a few degrees everywhere.

Unfortunately, the rate of heat flow through a steel surface is a highly

variable quantity and only poor estimates of heat transfer coefficients exist

for most processes of interest. However, if the temperature of the hot

surface and the subsurface gradient were measured, then the heat transfer

coefficient is determined and it becomes possible to calculate the temperature

everywhere within simple shapes.

A proposed method of measuring the near surface temperature gradient is to

observe surface-wave velocity dispersion. Surface (Rayleigh) waves are inhomogeneous waves whose displacement amplitude decays exponentially with

depth. Thus, high frequency surface waves sample the elastic constants of the

surface, while low frequency waves sample the constants of both the surface

and interior. If a gradient in modulus/density exists (due to a temperature

gradient), dispersion is observed. If the dispersion data (velocity values at

specific wavelengths) can be inverted to determine the depth dependence of the

modulus/density , then the subsurface temperature gradient can be deduced and

the heat transfer coefficient effectively defined.

To evaluate this potentially important approach, we have modeled the

propagation of surface waves in inhomogeneous media and are in the process of

exploring the sensitivity of Rayleigh wave dispersion to temperature gradient

Eddy Current Temperature Sensor- -Noncontact ultrasonic approaches to internal

temperature measurement currently utilize EMATs with magnetic fields of

between 0.2-0. 8 T. These fields are up to ten times stronger than the fields

currently envisaged for the containment of solidifying steel in prototype

electromagnetic thin strip continuous casters. These sensors are thus 1 i W- ! v to significantly perturb the process of interest and contravene the first rule

for successful sensing. Temperature and solidification sensors for this

application might more promisingly be developed based upon electrical

conductivity distribution measurement; a measurement which can be tackl< <1 with

less intrusive methodologies.

14
This approach also has use in other metal processing areas and is being

explored at NBS for temperature profiling purposes during the extrusion of

aluminum. The latter application is being addressed in a cooperative program

initiated in June with the Aluminum Association, and many of the conclusions

of this work are expected to be directly relevant to the steel problem.

The eddy current approach to measuring temperature profiles in metallic

materials is based on prior knowledge, for a given alloy, of the monotonic

increase of electrical resistivity with temperature. The depth of penetration

of an AC magnetic field (and the accompanying eddy currents) decreases with

increasing frequency. Since impedance measurements utilize varying frequencies, they sense average resistivities over varying depths. By analyzing

multi -frequency measurements, it is possible to obtain a reconstruction of the

resistivity profile and thereby the temperature profile. To implement this

approach, we have set up a computer-controlled impedance analyzer capable of

performing measurements at hundreds of frequencies in a minute. Figure 1 shows examples of measured impedance plane data from (a) a solid brass rod and

(b) a brass rod with a copper core demonstrating the changes associated with a nonuniform conductivity profile. The measured impedances will be used as input data for constructing the resistivity profiles.

START i 000.000 Hz STOP 100 000.000 Hz START i 000.000 "Hz STOP 100 000.000 Hz

Figure 1. Impedance plane plots of measured data taken on (a) a solid brass

rod of 1/4 in. diameter, shown on the left; and (b) a brass rod of the same diameter with a copper core shown on the right. The horizontal axes give the

real parts of the impedances; the vertical axes give the imaginary parts.

15
Another approach to eddy current determination of temperature profiles depends

upon measurement of the resistivity and resistivity gradient at the surface of

the test material. This, in turn, determines the temperature and the near- surface temperature gradient for a given alloy. With this information it is

possible to obtain the solution to the heat flow equations and to calculate

the entire temperature profile. This method depends on high frequency

(100 kHz to 1 MHz) impedance measurements, a range readily accessible with the

newly acquired instrumentation. A theoretical approach based on the JWKB

(Jeffrey, Wentzel, Kramers, Brillouin) approximation has been developed for

obtaining the resistivity and resistivity gradient from the high frequency

data, and is presently being used to evaluate the approach.

In-Process Ultrasonic Monitoring of Texture in Manufacturing of Aluminum

Product

A. V. Clark

Fracture and Deformation Division

Institute for Materials Science and Engineering

G. V. Blessing

Automated Production Technology Division

Center for Manufacturing Engineering

R. B. Thompson and J. F. Smith

Ames Laboratory

Iowa State University

A. Govado

Aluminum Corporation of America

It has been estimated that the U.S. aluminum industry produces about two

billion pounds of material for can manufacture annually. A crucial part of

the manufacturing process is control of texture or preferred orientation of

the aggregate of single crystals making up the rolled sheets from which cans

are made. Proper texture is essential in providing the mechanical properties

needed to mechanically form the cans. If better process controls than current

ones could be implemented, an estimated savings of about two cents per pound

or $40 million annually could be effected.

Currently, texture is characterized after an intermediate hot-rolling step

a temperature measurement. A high degree of cube texture is desirable at this

point in the manufacturing process, i.e., the cubic single crystals should

have one of their axes aligned in the rolling direction. In some cases, temperature measurement is inadequate, and rejection of the material occurs win n it is later discovered that the rolled sheet cannot be successfully deep-drawn

to can shape

The need for a better process control monitor to evaluate texture has led in a consideration of ultrasonic velocity techniques because ultrasonics has the

potential for real-time texture measurement. In contrast, other techniques

such as x-ray or neutron diffraction pole figures cannot be made in real ; i . and could require samples to be taken off line to a radiation source.

16
Recent theoretical advances at NBS and elsewhere have shown that velocities of

bulk and surface acoustic waves in rolled aluminum sheet are related to three

of the orientation distribution coefficients (ODC) which occur in the

expression for the orientation distribution function [1,2,3]. This function

gives the probability that a single crystal has a certain orientation relative

to the rolling direction.

In the current program, tests on two aluminum alloys were performed. First, a proof of concepts test was performed on 5052, a common alloy having a cube

texture. The purposes of this study were to determine which orientation

distribution coefficient can be used to characterize cube texture and to

determine precision and ease of measurement of various ultrasonic systems for

texture characterization. The ODC were measured using shear-horizontal (SH) waves at normal incidence, guided wave modes which were SH and Lamb waves, and

Rayleigh surface waves. Contacting piezoelectric and noncontacting electromagnetic acoustic transducers (EMATs) were used.

As an example we show the angular variation of the guided SH waves in

Figure 1 . Here EMATs were used to transmit and receive SH waves propagating

in the plane of the plate at different angles ip to the rolling direction. The

difference in velocity AV(V>) is given by [2]

AVsh (V0 = AW4 4 0 cos2 2ip (1)

where A is a constant and WA A

is an ODC. The maximum in the velocity along

the rolling and transverse directions shown in Figure 1 indicates cube texture; all other common aluminum textures give a minimum in these directions

[4].

A neutron scattering pole figure made using the same specimen is shown in

Figure 2. It shows a high degree of cube texture, in qualitative agreement

with ultrasonic results. A computer program is being written to obtain the

ODC from pole figures to compare with ultrasonic results. From our ultrasonic

studies, we concluded: the ODC, WA 4

, is easily measured with both SH and

Lamb waves and appears to characterize cube texture well. Measurements were easier to make and somewhat more repeatable with EMATs.

A similar series of measurements were next performed on specimens of 3004

aluminum alloy which are used in can manufacture. Specimens had different

hot-rolling temperatures and hence different amounts of cube texture. The

ultrasonic techniques described above were used to characterize texture in

these specimens after cooling to room temperature.

We found that two of the ODC were relatively insensitive to rolling

temperature. However, the values of WA ^ 0 measured with both SH and Lamb waves increased with decreasing exit temperature, in agreement with metallurgical

considerations. The correlation of W4 A

with exit temperature is promising

for the use of ultrasonics. Probably only W4 A

is necessary to discriminate

between acceptable and unacceptable texture. To ascertain this, a larger

database from additional specimens needs to be examined and quantitative

comparison made between ultrasonics and neutron diffraction pole figures which

can be considered as an accurate reference technique. In addition,

comparisons should be made with deep-drawing tests. We hope to address these

problems in the near future.

17
20

i//, degrees

Figure 1. Angular variation of guided SH wave in rolled aluminum alloy plate.

Open circles are data; solid line is theoretical value based on fitting

equation (1) to data at 0 = 0° , 45°. Minimum at 45° indicates cube texture.

Figure 2. Neutron diffraction pole figure for rolled aluminum aLloy pj.it t rolling direction is at top of figure. Solid lines are contours of intci

greater than that for random crystallite orientation; dashed lines arc contours with intensities less than random. Pole figure shows specimen ;

have cube texture

18
In summary, we have identified a key step in aluminum can production where

ultrasonics can be used as a process control monitor, namely, texture

measurement after hot-rolling. We have examined two alloys having texture

with various ultrasonic techniques and identified two techniques which appear

the most promising: measurement of angular variation of SH0 -and S 0 -modes. An

SH0 -wave is a plate wave moving parallel to the surface of the plate; the

atoms are excited and moving perpendicular to the propagation direction and in

the plane of the plate. An S 0 -wave is a plate wave moving parallel to the

surface of the plate; the atoms are excited and moving perpedicular to the

propogation direction and perpendicular to the plane of the plate. S Q -waves are the lowest order Lamb waves and have long wavelengths. Both the SH0 -and

the S Q -modes are measures of the ODC, WA 4

, which characterized cube texture

well. Furthermore, for 3004 alloy sheet, values of W4A0 increased as exit

temperatures decreased. This result, in qualitative agreement with metallurgical considerations, is a necessary condition for the use of in-process

ultrasonic texture monitoring.

References

1. C. M. Sayers, J. Phys . D: Appl. Phys . .15, 2157 (1982).

2. R. B. Thompson, S. S. Lee, J. F. Smith, Rev. Prog, in Quant. NDE 3B

D. 0. Thompson and 0. E. Chimenti, eds . , 1311 (Plenum Press, New York,

1984).

3. P. P. DelSanto and A. V. Clark, to be published in Proc . 2nd Int. Symp . on Nondest. Char, of Materials (1986).

4. D. R. Allen, R. Langman, C. M. Sayers, Ultrasonics 23., 215 (1985).

Magnetic Method for Nondestructive Evaluation

Lydon J . Swartzendruber

Metallurgy Division

Institute for Materials Science and Engineering

A variety of magnetic methods are available for nondestructive evaluation of

metals, both of defects and material properties. A number of these, such as magnetic flux leakage, magnetic particle inspection, and eddy-current testing,

are widely used in industry, primarily for the detection of defects. Some

other methods have been used on a limited scale but still require development

to make them more reliable and more widely applicable. These include:

Barkhausen noise, magnetoacoustic emission, magnetomechnical damping, and AC

magne tome try . Finally, magnetic property measurements, including saturation

magnetization, coercivity, and initial permeability, contain a wealth of

information concerning material properties that have barely begun to be

exploited.

To date, this project has been primarily focused on magnetic leakage field

methods, especially the magnetic particle method, and on Barkhausen noise

measurements. However, further progress in the use of magnetic methods,

especially as applied to the measurement of material properties, will depend

on improving our understanding of how the measurement of magnetic properties

19
correlates with material parameters such as alloy composition, heat treatment,

stress states, etc. It is clear that a multivariate approach will be

required. That is, two or more magnetic properties can be expected to yield

useful information, such as grain size, where a single property measurement

would give such information only under very restricted conditions. To this

end, we have been expanding our ability to perform magnetic measurements, both

for nondestructive evaluation and for other purposes. During the present

year, a vibrating sample magnetometer has been put into operation and is in

the process of being computerized. Also, a unique automated ac susceptibility

apparatus has been developed. The latter instrument allows the measurement of

initial magnetic susceptibility over a frequency range of 20 Hz to 100 kHz. A

unique feature is the ability to measure both the real and the imaginary parts

of the susceptibility over a wide temperature range. Initial studies are expected to center on the correlation of ac susceptibility, coercive force,

and Barkhausen noise with the microstructure of iron-carbon alloys.

Work has continued in cooperation with the American Society for Testing and

Materials (ASTM) Committee E7 and the Standards Subgroup of the Joint Services

Technical Coordinating Group on Nondestructive Inspection (JTCG-NDI) on improvement of magnetic particle inspection standards. A major problem with

both the ASTM standard (ASTM E709) and with the new military standard

(MIL- STD- 1949) is the tool steel test ring currently used to verify magnetic

particle performance. A recent test held by members of ASTM Subcommittee

E7.03, Society of Automotive Engineers (SAE) Committee K, and the American

Society for Nondestructive Testing (ASNT) Aerospace Committee revealed a wide

variation in the performance of such rings. An attempt is being made to

select a steel and a heat treatment with will reduce the variability in performance of the test rings. Further, even when such variability is reduced to

acceptable levels, the currently specified test ring does not do an adequate

job of testing the ability of particles to detect narrow cracks. The design

of a new test device is being explored at NBS

Ultrasonic and Optical NDE of Surface Roughness

D. G. Eitzen and G. V. Blessing

Automated Production Technology Division

Center for Manufacturing Engineering

T. V. Vorburger, D. E. Gilsinn, and E. C. Teague

Precision Engineering Division

Center for Manufacturing Engineering

This report covers research into ultrasonic and optical NDE techniques for : ho

measurement of surface roughness. The wavelengths of the probing radiation

for the two techniques differ by over two orders of magnitude. For the opt . .1 research we are using the HeNe laser wavelength of 0.6328 ^zm; for the ultrasonic research, the wavelength is 40 to 1500 /zm. Since the ratios of

roughness height and spacing to incident wavelength are important paramet< r- affecting the scattering phenomena, the two techniques are complementary; tli.it is, the resolution limit of the ultrasonic technique and the range of tin- optical technique are about the same, approximately 0.5 /zm . The present

emphasis of the ultrasonic work is the development and demonstration of

real-time in-situ tool - condition monitor for a computerized numerical eery;

20
(CNC) machining center work station. The present emphasis of the optical work

is the development and demonstration of an instrument to measure surface

finish in a final inspection work station. Both work stations are in the NBS

Automated Manufacturing Research Facility (AMRF)

Ultrasonic Characterization of Surface Roughness- -The goal of the ultrasonic

portion of the project is to develop and demonstrate new ultrasonic techniques

and tools for monitoring and characterizing surfaces, primarily for in-process

control of materials/part processing. Coupling of the ultrasonic pulse to the

surface can be by immersion, by air, or by a laminar stream of liquid

(squirter) . The principle used is that the roughness of a surface affects the

scattering of ultrasonic waves incident on the surface. The problem is to

evaluate the surface based on the scattered energy. The surface is

intrinsically important as a feature of the part or material and also as a parameter directly related to the process. For example, in unattended

machining the surface finish reflects tool condition (worn or broken tool) and can be used as an automatic tool management strategy [1].

The emphasis in FY85 was on measurements on flat stationary surfaces and on

the basic technique. The current work emphasizes the development of a demonstration system for in-process control of tool condition and improvements in

the robustness of the techniques.

A new nozzle for squirter coupling of ultrasound patented by Martin-Marietta

was evaluated. Its use significantly decreases the signal variations and

signal drop out which sometimes occur with other systems. A flexible extension was fitted to such a nozzle to permit the transducer/nozzle to be located

remotely from the work piece surface. By proper choice of the tubing

material, the extension acts as a waveguide and remarkably good ultrasonic

back-scattered signals can be obtained from a surface even with a severely

bent extension. The system has been used to obtain ultrasonic back- scattered

signals from round parts rotating with a surface speed of over 300 m/s, a surface speed range common in turning parts. The system worked well with the

three coolant/cutting fluids so far tested as the couplant stream. The

resolution obtained using the peak amplitude of back- scattered ultrasound to

monitor the surface of rapidly rotating parts was better than 3 jzm. Signal

processing techniques are expected to significantly improve this resolution.

Peak- amplitude signals which were collected in real time from a rotating part

with two roughnesses differing by 9 jum are shown in Figure 1 [2].

Some preliminary results show very interesting capabilities using higher

frequencies (15 to 40 MHz) and focused transducers. On static parts a resolution of better than 0.5 nm in the roughness average Ra has been

achieved. Focusing appears to lead to a profilometry capability. The surface

topography of a l-;um sinusoidal surface has been mapped in a preliminary

measurement indicating the possibility of developing real-time in-situ

capability for profilometry rather than only a spatial area average.

Preliminary work has also made use of non- specular scattering by aligning the

transducer (or stream) for non-normal incidence. In this case, a perfectly

smooth surface gives zero signal and the signal amplitude increases with

increasing roughness as opposed to the back- scattered signal which decreases

with increasing roughness. This relationship suggests a ratio method for

enhanced resolution.

21
00

r

i 90 h

00

Q.

<

O=c

70 h

iM

4 0

r

LU

cc: iU r £0

1 0

-

0

U.L XJ.J...X..L .LL. . .L-.I-J...J.,..|..1.I._|..J_ I I . I 0 25 50 75 100 125 150 175 2 00

TIME

Figure 1. Peak-to-peak back-scattered ultrasonic amplitude from a rotating

part with two surfaces differing by 9 /xm Ra

.

Optical Measurement of Surface Roughness - -During FY86 we also made progress on both the fundamental and applied aspects of our research into optical

measurements of surface roughness. On the fundamental side we developed a computer code to describe the fully three-dimensional optical scattering

distribution from rough surfaces. The code assumes a simple phase screen approximation to characterize the outgoing scattered wave. It uses as input

information a 512 x 512 square array of surface data points to describe the

topography z(x,y) of a surface in three dimensions, and it yields an angular

distribution of 87 x 87 points spaced over both the polar and azimuthal angles

of the hemisphere. Preliminary resuits for the scattering from a rough

surface are shown in Figure 2. The incident light is assumed to be incidt n: from the right hand side descending in the sin0g , z plane at a polar angle : 54°. The resulting scattering pattern shows a strong specular peak with

relative intensity equal to one and a weaker diffuse scattering distribu; ion

Because the original surface is significantly rougher along the sin©.,

direction, most of the scattering takes place along that direction and v< i little scattering is observed in the <f> s direction out of the plane of

incidence. Comparisons with scattering data obtained with the- NBS d< velo-,..

DALLAS optical scattering instrument [3] will test the accuracy of th< calculation .

22
Figure 2. Calculated light intensity scattered from a rough surface, shown as an angular distribution (in arbitrary units) over a hemisphere. 9 S and <f> s are

the polar and azimuthal scattering angles, respectively.

In the applied part of the optical research, we have been developing two

surface roughness inspection instruments, one for automated inspection of

surfaces for the AMRF and one for monitoring the roughness of fairly smooth

components with airfoil shapes that are difficult to inspect. For the latter

project, data have been taken as a function of proximity to the leading edge

of the airfoil and, hence, as a function of surface curvature. We are cur- rently analyzing the correlation between three variables: rms roughness aver- age as measured by a stylus, diffuseness of optical scattering as measured by

the optical instrument, and surface curvature.

Similar work was done using experimental results from the DALLAS instrument.

Figure 3 shows the empirical relationship between the roughness average Ra of

a set of hand lapped parts, as measured by a stylus, and the width of the

optical scattering distribution in terms of the variance o

2 expressed in

(degrees) 2

23
Figure 3. Roughness average Ra measured by a stylus instrument plotted versus

the variance o

z of the optical scattering intensity pattern along the polar

scattering angle 9. The variance is expressed in units of (degrees) 2

. These

data were taken for a set of hand lapped, stainless steel surfaces. The

parameters of the best fit straight line are also shown.

References

1. G. V. Blessing and D. G. Eitzen, Invention Disclosure, December 1985.

2. G. V. Blessing and D. G. Eitzen, Ultrasonic Sensing of Surface Roughness,

Proceedings (17-19 Nov. 1986 IEEE Ultrasonic Symposium, Williamsburg, VA

3. T. V. Vorburger, E. C. Teague, F. E. Scire, M. J. McLay, and

D. G. Gilsinn, "Surface Roughness Studies with DALLAS - Detector Array f Laser Light Angular Scattering," J. Research of NBS 89, 3 (1984).

24
NDE FOR COMPOSITES AND INTERFACES

The goal of this activity is to develop generic approaches, sensors and

procedures for quantitative NDE of composites and interfaces. As in the two

previous activities, the emphasis is on measurements that can be made during

the manufacturing process to sense the properties of the product during critical stages of its formation and to provide the data required to control the

process to optimize quality and productivity. Since the knowledge base on composites characterization is far from complete, we expect that a portion of

this activity will be concerned with relating important composite

characteristics with performance and then developing NDE monitoring methods.

This activity includes: determining the feasibility of utilizing fluorescent

spectroscopy, dielectric measurements, and microwave techniques to monitor the

processing of polymer matrix composites; applying ultrasonic and acoustic

emission techniques to improve the understanding of, and the ability to monitor, interfaces; and utilizing x-ray diffraction techniques to increase the

understanding of residual stress in composites. Noteworthy accomplishments in

this activity include:

o Research demonstrated the applicability of two complementary nondestructive

evaluation techniques for cure monitoring and process control of epoxy

resin composites. One technique combines the sensitivity of the

fluorescence intensity of some organic dyes to local viscosity with

embedded optical fibers. During the past year refractive index effects were quantified so that appropriate optical systems could be selected. The

second technique is based on dielectric measurements utilizing embedded

electrodes. Research during the past year demonstrated the use of conductivity and dielectric loss mechanisms to follow the cure of several

different resins.

o In order to monitor the processing of composites with nondestructive

evaluation sensors, the effects of residual stress, which greatly affect

the mechanical behavior of composites, must be understood. To this end,

aluminum reinforced with silicon carbide particles was studied both experimentally and theoretically. Quantitative stress levels were obtained and

the results show that the matrix is in hydrostatic tension and the

particles are in compression.

o Interfaces in composites have a major effect on material properties. In

order to gain more knowledge about interfaces and to develop nondestructive

evaluation techniques for characterizing them, a theoretical study was com- pleted for interface effects on ultrasonic phase velocity and attenuation

in composite materials. A wave scattering approach was used to calculate

attenuation from the scattering cross section of a single particle. The

results suggest possible use of ultrasonic waves to study and characterize

interfaces in composite materials.

o A theoretical and experimental study using guided interface ultrasonic

waves (Stoneley waves) to study metal matrix composite interfaces was initiated. Near agreement between theory and experiment was obtained for a model system and the nondestructive evaluation technique might prove useful

for detecting poor quality interfaces.

25
Cure Monitoring In Epoxv Resin Composites

F. I. Mopsik, B. M. Fanconi , F. W. Wang, and R. E. Lowry

Polymers Division

Institute for Materials Science and Engineering

The need for process control in the production of epoxy resin-based composites

has stimulated investigations into the use of fluorescence and electrical

measurements for monitoring cure reactions. This need has become more pressing as the use of composites offers important advantages in strength and

weight as well as potential savings in fabrication costs.

With the development of suitable techniques, reported last year, the current

work on electrical measurements has explored the use of conductivity and

dielectric loss mechanisms to follow cure of several systems. The

fluorescence technique combines the sensitivity of the fluorescence intensity

of some organic dyes to local viscosity and optical fibers, as a means of

probing the interior of a thick specimen.

During the past year, fluorescence experiments were conducted to investigate

factors that may affect or limit the usefulness of optic fibers in cure monitoring systems. One factor investigated was the effect of the difference

in the refractive indices of the optic fiber and surrounding medium. In order

for a glass fiber to operate as a waveguide, the refractive index of the glass

must be higher than that of the surrounding material. The penetration depth

of the evanescent wave and the efficiency of the waveguide to collect the

fluorescent light depend on the refractive index difference. In addition, the

refractive index of the resin system is expected to change during cure as a result of changes in density and chemistry. To explore the degree to which

the observed fluorescence is affected, experiments were conducted using dyes

dissolved in mixtures of two solvents having different refractive indices.

All experiments were carried out using a setup that simulated the arrangement

envisaged for real-time cure monitoring of composites. Laser light of

501.7 nm was focused onto one end of a glass fiber of approximately 100 /im

diameter. The glass fiber, 1.47 refractive index, was immersed in mixtures of

propanol-1 and o- dichlorobenzene containing the dye rhodamine-B. The light

exiting the other end of the fiber was focussed onto the entrance slit of a double 0.25-m monochromator and the intensity monitored as a function of

frequency using photon counting electronics.

The fluorescence intensity as a function of the refractive index of the

solvent mixture is shown in Figure 1. The intensity of the fluorescence from

a solution whose refractive index is lower than that of the fiber is about

1000 times greater than the intensity from a solution whose refractive index

is higher than that of the fiber. The refractive index range of the

transition is rather narrow, about 0.05. This suggests that as long as the

refractive index of the waveguide is higher than that of the curing resin !>v at least this amount there should be little effect on the measured intens i t

caused by small changes in the refractive index during cure. The residual

intensity observed where the medium refractive indices substantially ex< . <<l-. that of the fiber is attributed to emission excited by light which escapes :!.< fiber at the air/fiber/solution interface.

26
In future work on the fluorescence technique, optical fibers will be used to

probe consolidation and fiber wetting in polymer matrix composites.

The electrical measurements were carried out on three different resins cured

with imidazole, and one of them was also cured with a diamine curing agent.

All three resins showed similar behavior with the imidazole curing agent and

one of them was intensively studied at a cure temperature of 55 °C for

comparison with other techniques. The frequency used for conductance

measurements was 50 Hz

A normal cure curve for conductance is shown by the upper curve of Figure 2

The leveling off of the conductance, at long times after the main cure, is

associated with a loss mechanism, as shown in the last year's report, and

slowly evolves with the resin. The data obtained by isothermal differential

scanning calorimetry (DSC) and ultrasonic measurements on the same systems

showed very similar times to cure. In contrast, the viscosity data show a rapid rise earlier than the conductance data and become impossible to obtain

while the cure is still progressing.

REFRACTIVE INDEX DF SOLUTION

Figure 1. Fluorescence intensity transmitted in optic fiber immersed in

solvent mixtures.

In addition to studying a full cure cycle on freshly prepared resin, mixed

resin was allowed to age at room temperature prior to cure for increasing

periods of time. The aged material was then cured at 55°C with the results

shown as the lower curves in Figure 2. The time shifts, needed to superimpose

the curves, defined a new cure curve at room temperature whose time scale

extrapolated well from higher temperature data. These results agree with

aprevious conjecture that a simple conductivity measurement can be used to

monitor the state of a mixed resin system prior to cure; this would be useful

in defining the processing conditions (time, temperature) required to achieve

a predetermined degree of cure.

27
I • 1 1 1 1 1 I I 1 I L 0 100 200 300 400 500

> 1 1 1 . ,, i 1 i i j i 0 100 200 300 400

CURE TIME (min)

Figure 2. Conductance at 55°C for epoxy - imidazole resin.

The measurements of the system using a diamine curing agent show some new features not found in the same resin cured by imidazole. The conductance as a function of time, Figure 3, shows a rapid decrease with time as the resin

gels, but at about the time the resin has hardened the conductance increases

and goes through a maximum. The loss spectrum is typical of a dipolar loss

mechanism that extends to frequencies below the lowest frequency used. The

appearance of this loss is clearly due to the lower conductance level of the

resin system using the amine curing agent. Other measurements, including

ultrasonics and DSC, show that this loss process occurs after the resin has

set

Figure 3. Conductance at 45 °C for epoxy - diamine resin.

28
Interface Effects on Phase Velocities and Attenuation In Composite Materials

S. K. Datta

Department of Mechanical Engineering

University of Colorado

H. M. Ledbetter

Fracture and Deformation Division

Institute for Materials Science and Engineering

Strength and mechanical behavior of composites depend strongly on the

properties of interfaces between the reinforcing phase and the matrix.

Interface characteristics are affected by both thermomechanical processing and

by mechanical- load history. Although strong interface bonds promote high

strength, for some specialized applications we may seek weak interfaces to

enhanc e damp ing

The present study examines the dependence of overall elastic moduli and

attenuation on the presence of an interface transition layer. We do not

assume a sharp discontinuity of elastic properties between the reinforcing

phase and the matrix (as would exist for perfect bonding) . Instead, we consider the effect of a thin transition layer through which properties change

continuously. We consider wave propagation through a composite of a random

distribution of spherical particles with interface transition layers in a homogeneous matrix. Using a wave - scattering approach, we derive effective

phase velocities of plane longitudinal and plane shear waves. We have

presented long -wave length approximate results, and have derived expressions

for both phase velocities and attenuation [1-4]. The latter is calculated

from the scattering cross section of a single particle. We also derived the

frequency dependence of the scattering cross section [3,4]. The results

suggest possible uses of ultrasonic waves to study and characterize interfaces

in composite materials.

References

I. S. K. Datta and H. M. Ledbetter, "Effect of Interface Properties on Wave

Propagation in a Medium with Inclusions," in Mechanics of Material

Interfaces . eds . A. P. S. Selvaduai and G. Z. Voyiadjis, pp . 131-142

(Elsevier, New York, 1986).

2. S. K. Datta and H. M. Ledbetter, "Ultrasonic Characterization of Material

Properties of Composite Materials," to appear in Proceedings of the 10th

U.S. National Congress on Applied Mechanics (ASME, New York, 1987).

3. S. K. Datta and H. M. Ledbetter, "Interface Effects on Attenuation and

Phase Velocities in Metal Matrix Composites," presented at Review of

Progress in Quantitative NDE , LaJolla, California 1986.

4. S. K. Datta and H. M. Ledbetter, "Ultrasonic-Velocity Studies in Metal

Matrix Composites: Measurement and Modeling," presented at the

Conference on Nondestructive Testing and Evaluation of Advanced Materials

and Composites, Colorado Springs, August 19-21, 1986.

29
Internal Strain (Residual Stress') In Composite Materials

H. M. Ledbetter

Fracture and Deformation Division

Institute for Materials Science and Engineering

Internal strain, or residual stress, interferes with many materials uses. Its

detection, explanation, measurement, and control present many problems to

materials scientists and engineers. This is especially true for multiphase

materials which are prone to internal stress. This is the case because the

phases possess different thermal expansivities and temperature change induces

stress through incompatible strains. Even small temperature changes may cause large stresses. As an example, consider SiC particles embedded in an Ai-alloy

matrix. The temperature decrease , AT, required to cause a hydrostatic tensile

stress equal to the AJ?-alloy yield strength, a

y , 274 MPa, is

AT = o

y /3Bm

(ccm -qp

) = 64 K (1)

where B denotes bulk modulus, a is the coefficient of linear thermal

expansion, superscript m matrix, and superscript P particle. Here, we use the

ambient- temperature physical properties:

B

m = 74.9 GPa , aF = 3.3-10- 6 K

_1

, and a

m = 22.5-10" 6 K' 1

Many methods exist for studying internal stress including x-ray diffraction,

ultrasonics, Barkhausen noise, and photoelasticity. By far, the most widely

used of these methods is x-ray diffraction. Our experimental studies use a standard commercial x-ray diffractometer, without modification. We use a sin2

V> method, in modern version [1], to account correctly for e 13 strains. We are currently studying reinforced metal-matrix composites, especially SiC

p /Ai?

and SiC f /A>e.

Our approach has been to try to combine measurements with modeling. So far, our modeling consists mainly of elastic sphere- in-hole calculations. The calculations provide an essential background for guiding the measurements and

their interpretation. We hope to extend the modeling to an Eshelby- inclusion

approach and include plasticity.

Here, we summarize results on SiC

p /Ai with details published elsewhere [ 2 , 3 ]

. Equation (1) shows that cooling only 64 K below the material's consolidation

temperature (where good interfaces form) causes a matrix tensile stress equal

ling the yield strength, 274 MPa. Further cooling might workharden the material and increase the stress. Table 1 summarizes the measurements with a and

c denoting unit-cell dimensions, V volume, e strain, and a stress. These

results represent average macroscopic stresses. Transformation to local polar

co-ordinates suggests stresses up to 419 MPa.

30
_ _ » -

- W

y vA = - - -
Measurement of Flow Birefringence at Microwave Frequencies

A. K. Gaigalas

Chemical Process Metrology Division

Center for Chemical Engineering

The object of the project is to develop microwave sensors to monitor polymer

properties of flowing, molten thermoplastic polymers. The sensors would be

mounted at right angles in the wall of a flow channel and detect the small

differences in dielectric constant induced by flow at the boundary. The

difference would reflect molecular size distribution and extent of

crossbinding

The thrust of the work this year has been to design and fabricate a microwave

sensor with sufficient sensitivity to detect the small dielectric differences.

A hairpin line was selected because theoretical consideration showed that its

propagation characteristics are very sensitive to the properties of the material on top of the line. The hairpin line consists of a repetitive sequence

of conductor strips each in the shape of a hairpin. The conductors are laid on top of a thin dielectric substrate. The adjacent conductors couple with

each other via field lines which extend into the material above the hairpin

line. The detailed description of the propagation of energy along the hairpin

line requires specific calculation of the coupling of adjacent lines. The

present model assumes that all the lines are equally spaced and that the thin

conductor model can be used to calculate the coupling of adjacent lines.

Based on this model we designed a hairpin line and had it fabricated commer- cially with dimensions shown in Figure 1. Examination of the fabricated line

under a microscope showed that the lines and line spacings were very uniform

and that the actual line looked very much like the pattern in Figure 1 . The

hairpin line was connected to a 50 fi strip line via a tapered strip line. The

impedance of the hairpin line was estimated by using the model and care was taken to match the impedance to a 50 ft line. The tests of this set-up proved

to be negative, since no signal was transmitted through the line.

Work was undertaken to explain this negative result. Three transmission lines were fabricated on 0.032-in. material. They were a meander, hairpin and comb

lines. The results of the transmission measurements are shown in Figure 2. As expected, the meander line shows no band pass properties. The comb lino is

supposed to have a wide band pass and this is reflected in the transmission

data (the reason for the existence of the two peaks is not clear yet). The

hairpin line was designed to operate at 2000 MHz with a bandwidth of a few

hundred megahertz. The data show that the model does not predict the bandwidth properly. The transmission peak of the hairpin line is near 2000 MHbut the amplitude is too low by an order of magnitude.

32
HAIRPIN LINE

(625 lines/inch)

Figure 1. Cross-sectional view of the hairpin line which was fabricated for

the preliminary tests.

Figure 2. Results of transmission measurements on various lines. V(t) is

proportionate to the power transmitted through the line and V(r) is

proportionate to the power transmitted through a reference branch of the

circuit

33
Further work is needed to upgrade the model for predicting hairpin line

behavior. It was noted that hairpin lines used in commercial integrated

microwave circuits do not have equally-spaced conductors. The conductors of

the same hairpin are widely spaced while the conductors of adjacent hairpins

are much closer. An upgraded model of the hairpin line will provide for different conductor spacing and a more realistic calculation of the coupling of

adjacent lines. The model will be checked with a small number of lines

(approximately 40 per conductor) etched on 0.032 material.

Guided Interface Waves

E. Krasicka, J. A. Simmons, and H. N. G. Wadley

Metallurgy Division

Institute for Materials Science and Engineering

The performance of advanced metal matrix composites is dependent upon the

properties at the metal-reinforcement interface. Of particular import are the

interface adhesion and local elastic properties. It seems reasonable to hope

that characterization of interfaces might be possible through the use of

interface elastic waves. The existence of interface waves at the planar

interface between two media of differing elastic constants/densities was first

predicted by Stoneley [1] and later observed in seismograms following major

earthquakes. It has since been shown that very restrictive conditions must be

met by the two media in contact if the wavevector (or velocity) of the

interface wave is to be a purely real number so that non- attenuating

propagation occurs [2],

For most material couples, the restrictive rules are not exactly met, but

modes still exist wherein the wavevector of the interface wave is found to be

complex [3]. Thus, the interface wave suffers attenuation (at a rate

determined by the magnitude of the imaginary component) as it propagates. The

physical mechanism of attenuation is the radiation of elastic energy away from

the interface. If the attenuation is not too great, these interface waves may

still be used to characterize the interface region provided the relationships

between velocity and local elastic properties can be established.

Our first year's effort in this area has focused upon a combined theoretical/

experimental study for testing these concepts using guided interface wave propagation in a model system consisting of a stainless steel rod shrinkfitted into an aluminum matrix. The normal modes of a cylindrical rod in an infinite matrix, including interface modes, is obtained from matching

displacement and traction conditions at the interface. The condition for such

modes is the vanishing of a determinant which depends on the phase velocity of the modes. Complex values of the velocity can also cause the determinant to

vanish, and those velocities lying in the correct complex half plane,

correspond to leaky normal modes whose amplitude decays exponentially with

distance from the driven end of the rod.

The form of the determinant for radial modes (those whose displacement <h |

• i only on radius and longitudinal distance along the cylinder) is well-known

(c.f. [3]). However, accurate computer codes for determining such mode;, m.iv not exist.

34
We have developed new, accurate algorithms for calculating modified Bessel

functions over the large complex parameter range needed for normal mode

determination in the cylindrical geometry, and modified the asymptotic form of

the determinant so that it remains analytic and of limited dynamic range

throughout this region. Rouches's theorem for analytic functions then permits

calculating the number of zeros inside a box- shaped region by use of an adaptive integration scheme. Combined with Newton's method for obtaining roots

and several search routines, the phase velocity for all useful ordinary and

leaky radial modes has been mapped out over a range of frequency and cylinder

geometry for a sample consisting of a stainless steel rod encased by an alumi- num matrix. The phase velocity depends on a curvature frequency parameter

(f.R) which is valid for all fiber radii and applied frequencies down to the

atomic scale until the elastic hypothesis no longer applies. Two leaky radial

interface modes have been theoretically predicted for a steel rod embedded in an aluminum matrix. In one case the mode appears to be an attenuated shear

wave concentrated in the aluminum. Its damping increases rapidly with

increasing curvature so that, at curvatures where the velocity deviates significantly from the shear velocity, the mode is undetectable by ultrasonic

means (assuming that the measurable attenuation range is - 80db)

This wave was calculated and measured [3] for a cylindrical aluminum steel

interface at 10 MHz for R = 8.75 mm.

The model sample was composed of a 3.2-mm radius 316 stainless steel rod

embedded in a 2024 aluminum alloy cylinder. The rod was attached to the

aluminum by shrink fitting. This process created a good cylindrical interface

between the two materials. Interface waves were generated by the conversion

of surface waves propagated along the rod, although many other methods and

techniques were investigated. The interface wave velocities measured as a function of frequency for the model sample are compared with the theoretical

solution in Figure 1 for frequencies of 1 , 3, 6, 11 and 15 MHz. The accuracy

of measurements was 30 m/s. Excellent agreement with theory was observed.

The other results (triangles) shown in Figure 2 were obtained on a cast-metal

matrixcomposite model which contained a number of rods of radius 1.195 mm

spaced4 mm apart in an aluminum matrix. In this cast sample there are small

flaws at the interface (Figure 2) . These separations at the interfaces are thought to be the origin of the slight deviation of the experimental results

from the theoretical predictions at higher frequencies. A much larger

deviation from the predicted behavior occurs at low frequency when the wave- length becomes comparable with the spacing between the fiber-model rods and

interaction occurs between neighboring interfaces.

35
Figure 1. There is good agreement between theory curves and experiment for a good interface obtained by a shrink fit (circles) . As expected, a poor

interface (triangles) results in deviation between theory and experiment.

Figure 2. Cast metal matrix composite model. Visible interfaces between

aluminum and steel.

In conclusion, very good agreement was obtained between the measured and i retically predicted interface velocities in the aluminum steel model mati-i

Deviations from theory may serve to characterize the quality of the in:<-rfa

We are now examining the displacement wavefields of these waves as a pn . : to addressing the inverse (elastic constants determination) problem.

36

Attenuation/dB

[mm

MHz]-
This work has been performed with partial support from the Office of Naval

Research

References

1. R. Stoneley, Proc . Roy. Soc . (London) 106 . 416 (1927).

2. T. E. Owen, Prog. Appl, Mat. Res. 61 . 69 (1964).

3. D. A. Lee and D. M. Corbly, "Use of Interface Waves for Nondestructive

Testing" IEEE Trans, on Sonic and Ultra. SU-24 . 206 (1977).

4. E. Krasicka, J. A. Simmons, and H. N. G. Wadley, presented at Review of

Quantitative NDE, San Diego, August 1986.

37
NDE STANDARDS AND METHODS

When the Nondestructive Evaluation Program was established at the National

Bureau of Standards in 1975, its goal was to upgrade the reliability and the

reproducibility of those NDE methods that are widely used in American industry. The approach was research that would provide a scientific understanding

of the NDE methods, and permit the development of measurement standards and a system of traceability for NDE measurements. The principal use of NDE at that

time (and even today) was for in-service inspection.

Considerable progress toward this goal was achieved over the past decade and,

accordingly, the Program's objectives have been broadened. Major programmatic

activities are now directed toward developments in NDE which will facilitate

its use in metal processing, manufacturing, and other production processes.

Nevertheless, the original goal of the Program is still very valid. Based on continued need and importance, the development of measurement standards and a system of traceability for NDE measurements is still one of the Program's four

basic activities and, indeed, it is the central activity through which the

others are related.

The objective of the NDE Standards and Methods activity is to provide the

scientific understanding of NDE measurement methods, and to develop, maintain,

and disseminate effective standards for NDE measurements which are traceable

to national standards. In FY 1986, projects to develop new and improved

measurement standards were carried out for eddy currents, x-ray radiography,

leak testing, thermography, and fluorescent liquid penetrants. Work to

develop new and improved measurement techniques was carried out for eddy

currents, thermal waves, and acoustic methods, and a new effort on real-time

radiology was initiated in collaboration with Iowa State University. Many

significant accomplishments were recorded. A few examples are listed here:

o New prototype standards for evaluating eddy current probes were developed.

One of these is an unflawed metal artifact which contains regions of

different, but well characterized, conductivity. This standard will

probably lead to a simple, fieldworthy technique for qualifying probes.

Another artifact forms the basis for a laboratory procedure for calibrating

probes. This artifact, which incorporates a radially symmetric, artificial

defect in a plate, produces an impedance change in a probe. The magnetic

field strength of the probe per unit current- -which must be known in order

to assess flaw sizes- -may be calculated from the impedance change.

o New standards have been developed for measuring the quality of radiograph i <- images produced at very low and very high x-ray energies. These standard' are being evaluated in the public sector and are expected to supplement

standard developed previously for moderate energy levels. These stand,.:'’

permit the various parameters involved in the radiographic process to be- assessed in terms of their individual influences on image quality.

o The framework for an NBS calibration service for leak measurements was established. Construction and verification of a primary leak standard v. r< completed, and robust procedures for characterizing transfer standard'

called "calibrated leaks") were developed. A special test service was initiated for helium diffusion leaks in the range of 10 8 to

38
10’ 11 mol/s (2 x 10’ A to 2 x 10’ 7 atm- cm3 /s) . Announcement of a formal

calibration service awaits completion of detailed quality control

documentation

In the brief, project reports that follow, two reports are included on projects that were supported by other agencies. These, it will be noted, are very closely related to the objectives of the NDE Standards and Methods

activity

Eddy Current Coil Characterization

T. E. Capobianco and F. R. Fickett

Electromagnetic Technology Division

Center for Electronics and Electrical Engineering

The major goal of this program is the investigation of methods for characterization of eddy current test coils. Three approaches are under investigation.

The first is the determination of electrical parameters, including a study of

known defective coils; the second is the application of magnetic field mapping

techniques to the various coils and probes; and the third is the investigation

of the use of artifact standards coupled with precision electronic measurements for coil evaluation. A secondary goal is an investigation of the

application of high sensitivity flux detection using superconducting quantum

interference devices (SQUIDs) to flaw detection problems.

Last year we developed the basic systems for the various measurements now

being used for probe evaluation. Foremost among these were the electrical

parameter characterization and field mapping instrumentation. Last year's

results led us in the relatively new direction of some unique artifact standards. Last year's work also convinced us that, for probes of importance to

commercial NDE, the SQUID field mapping system was not superior to one based

on a sensitive lock-in amplifier which is much easier to operate.

Our studies on electrical parameter characterization have encompassed a number

of different coil systems and made use of a large number of commercial coils,

both good and defective, acquired as a result of our interactions with various

military organizations. The major study was on the variation of electrical

parameters among ostensibly identical probes [1]. This work is directly tied

to our effort to develop a military standard for eddy current probes [2], The

main outcome of this work is a field test method for probe characterization

that uses unflawed metal artifact standards of varying resistivity. Work has

also been completed on our studies of differential - coil eddy current probes

[3].

Further development of field mapping instrumentation has been completed

including a software system that gives an informative display of the field

configuration of the coil. A sample plot is shown in Figure 1. Field plots

have been made on a large number of commercial coils and on several specialty

coils developed in the laboratory, and these results were related to

electrical and mechanical probe parameters [4]

A SQUID-based system for flaw detection-at-a-distance studies is under

construction. The concept is based on our earlier work using the SQUID for

field mapping [5] and in conventional flaw detection configurations [6].

39
In a cooperative venture with the Fracture and Deformation Division, we have

jointly developed and produced a number of uniform field probes for use in

their flaw detection studies. We have characterized these probes both by

measuring electrical parameters and by making three-dimensional field maps

[7]. These probes were then successfully used in flaw detection

experiments [8].

#A5 5/14/06

Tangential File: TN514A5 Axial File: AX514A5

Figure 1. Field map of commercial bolt-hole probe showing magnitude and

direction of field across probe face.

References

1. T. E. Capobianco, "Parameters Affecting Eddy Current Probe Sensitivity,"

to be presented at 1986 Fall ASNT Conference.

2. T. E. Capobianco and F. R. Fickett, "A Proposed Military Standard for

Commercial Eddy Current Probes Based on Performance Characterization,"

presented at 35th Defense Conference on NDT.

3. T. E. Capobianco and Kun Yu, "The Effect of Pickup Coil Spacing on Differential Eddy Current Probe Sensitivity," presented at Review of

Progress in Quantitative Nondestructive Evaluation, LaJolla, California

1986.

4. T. E. Capobianco, "Field Mapping and Performance Characterization of

Commercial Eddy Current Probes," presented at Review of Progress in

Quantitative Nondestructive Evaluation, LaJolla, California 1986

40
5. F. R. Fickett and T. E. Capobianco, "Magnetic Field Mapping with a SQUID

Device," Review of Progress in Quantitative Nondestructive Evaluation , Vol. 4 (Plenum, New York, 1985), p. 401.

6. T. E. Capobianco, J. C. Moulder, and F. R. Fickett, "Flaw Detection with a Magnetic Field Gradiometer , " 15th Symposium on Nondestructive Evaluation

(NTIAC, San Antonio, 1986), p. 15.

7. P. J. Shull, T. E. Capobianco, and J. C. Moulder, "Design and

Characterization of Uniform Field Eddy Current Probes," presented at

Review of Progress in Quantitative Nondestructive Evaluation, LaJolla,

California (1986).

8. J. C. Moulder, P. J. Shull, and T. E. Capobianco, "Uniform Field Eddy

Current Probe: Experiments and Inversion for Realistic Flaws," presented

at Review of Progress in Quantitative Nondestructive Evaluation, LaJolla,

California (1986).

Measurement Methods. Calibration Procedures, and Standards for Quantitative

Eddy Current NDE

J. C. Moulder and P. J. Shull

Fracture and Deformation Division

Institute for Materials Science and Engineering

B. A. Auld and S. Jefferies

Edward L. Ginzton Laboratory

Stanford University

The major objective of this program is the development of measurement methods,

calibration procedures, and standards for quantitative eddy current NDE.

Experimental measurements at NBS Boulder are carried out in close

collaboration with theoretical studies at Stanford University.

In the past we compared experimental eddy current measurements with the

predictions of theoretical models of the interaction of nonuniform probe

fields with surface -connected cracks [1,2]. This year we extended these

studies to reflection probes. Eddy current reflection probes are two-port

devices with an excitation coil surrounding a pair of oppositely phased pickup

coils. A general AZ theory for this type of probe was developed at Stanford

last year for application to new types of electromagnetic robotic proximity

sensors [3]. In our study this year, this theory was applied to the characterization of surface flaws. A special air-core eddy-current reflection probe

was constructed at NBS Boulder and used to obtain flaw signals for a number of

rectangular- shaped EDM notches in aluminum. An automatic network analyzer was used to measure flaw signals as the probe was scanned over the length of the

flaw. Experimental results showed excellent agreement with theoretical

predictions [4]

Last year, we devised a new calibration method for uniform- field eddy current

(UFEC) probes that consists of measuring the impedance change AZ induced in

the probe by a cylindrical recess in the surface of a specimen of known

41
conductivity. From this measurement, the magnetic field strength per unit

current H/I can be deduced, a quantity that enters into any calculation of

flaw signals for the probe. This year, we tested this method more thoroughly

and have identified some difficulties in applying the method to lowconductivity materials like titanium. The equation relating AZ to H/I is

AZ = i(H/I) 2 (2/a) (Ad/6 2

) (1)

where a is conductivity, 6 is skin depth, A is surface area, and d is depth of

the cylinder. Equation (1) was derived in the limit of small skin depth (d/6 > 2) using Slater's microwave perturbation theory applied to a smooth depression in a perfect conductor. When using low conductivity materials, it is

necessary to make the cylinder relatively deep in order to exceed the skin

depth, but this in turn invalidates the assumption of a smooth depression in

the surface. Measurements on a series of recesses in titanium have shown that

Eq.(l) underestimates the field strength by a factor of two. Further studies

are underway using air core probes, for which H/I can be accurately

calculated, in order to verify this finding.

A new project was begun this year with funding from the Air Force to evaluate

the use of uniform field eddy current probes to characterize surface-connected

flaws. Our colleagues in the Electromagnetic Technology Division have collaborated with us in designing and characterizing the probes for this work [5],

and an extensive series of flaw measurements were made in order to evaluate

the reliability of the method in determining flaw sizes [6].

References

1. B. A. Auld, S. Jefferies, J. C. Moulder, and J. C. Gerlitz, "SemiElliptical Surface Flaw EC Interaction and Inversions: Theory," Review of

Progress in Quantitative NDE . Vol. 5 (Plenum, New York, 1986), p. 383.

2. J. C. Moulder, J. C. Gerlitz, B. A. Auld, and S. Jefferies,

"Semi-Elliptical Surface Flaw EC Interaction and Inversions: Experiment,"

Review of Progress in Quantitative NDE . Vol. 5 (Plenum, New York, 1986),

p. 395.

3. B. A. Auld, J. Kenney, and T. Lookabaugh, "Electromagnetic Sensor Arrays -- Theoretical Studies," Review of Progress in Quantitative NDE . Vol. 5 (Plenum, New York, 1986), p. 681.

4. J. C. Moulder, P. J. Shull, B. A. Auld, S. Jefferies, and S. Ayter, "Eddv

Current Reflection Probes: Theory and Experiment," presented at Review <>! Progress in Quantitative NDE, LaJolla, California (1986).

5. P. J. Shull, T. E. Capobianco, and J. C. Moulder, "Design and

Characterization of Uniform Field Eddy Current Probes," presented at

Review of Progress in Quantitative NDE, LaJolla, California (1986).

6. J. C. Moulder, P. J. Shull, and T. E. Capobianco, "Uniform Field Eddy

Current Probe: Experiments and Inversion for Realistic Flaws," presented

at Review of Progress in Quantitative NDE, LaJolla, California (I486)

42
Development of Leak Standards and Calibration Facilities at NBS

C. D. Ehrlich and C. R. Tilford

Temperature and Pressure Division

Center for Basic Standards

A leak standards project was initiated at NBS in response to industry

requirements for both improved leak measurement accuracy and, in some cases,

legal traceability to a recognized standards authority. The project objectives were to develop a primary leak standard, characterize transfer leaks,

and provide a publicly accessible leak calibration service. We have met the

first two of these objectives on a limited basis, and are establishing a special test service* for helium diffusion leaks in the range 10' 8 to

10" 11 mol/s (2 x 10' 4 to 2 x 10" 7 atm-cm3 /s @ 0°C)

The capabilities of the NBS primary leak standard were explored extensively

this year, particularly in the low flow rate regime of 10" 9 to 10" 12 mol/s for

helium. A schematic diagram of this standard is presented in Figure 1. The

pressure indication "P" in the vacuum chamber, caused by gas flow from the

leak, is matched by flow from the flowmeter. The flow rate is then measured

using the flowmeter. A new bellows flowmeter has been used extensively and

compared with the original piston flowmeter whenever possible. Performance

has been evaluated for the two flowmeters; this information is being prepared

for publication in an archival journal [1]; a summary error budget is given in

Table 1. A new vacuum chamber was added to the system this year, as were sev- eral residual gas analyzers (RGAs) . The RGAs are used to measure not only the

total pressure "P" in the vacuum chamber, but also the partial pressure of the

gas of interest, avoiding background gas complications. The stability and

repeatability of these RGAs are also under investigation.

The results of initial transfer leak characterizations and comparisons with

Sandia National Laboratories were published [2]. Considerable effort was devoted to developing and measuring fixed- reservoir helium permeation leaks,

which have been found to have superior stability over other types of artifacts. A leak comparator system, which will be used to perform the majority

of the customer special tests, has been used extensively to measure both the

temperature and pressure response characteristics of permeation leaks.

The first two special test reports were issued for NBS-owned fixed- reservoir

helium permeation leaks, based on measurements performed on the primary leak

standard over a six-month interval. These artifacts were subsequently used in

the evaluation of nuclear fuel shipment casks. The comparison program with

the Primary Standards Laboratory at Sandia is continuing with a 10’ 12 mol/s

range helium permeation leak. A leak measurement workshop at Sandia provided

a forum for presenting some of the earlier comparison data, as well as for

discussing the topic of the most appropriate leak rate units for high accuracy

work [ 3 ]

Future plans for the leak standards project include completing the

documentation required for calibration service status, extending the capabilities to lower (and possibly higher) values of leak rate and including other

* A special test service involves a measurement or calibration method which

is still being perfected and for which all the quality control documentation

has yet to be completed.

43
gases in the transfer leak characterization program. Long-range plans include

the development of a second primary standard of a different type, as well as investigations into novel measurement techniques.

The support of Richard Hyland, Fred Long, and Donald Martin in this work is

gratefully acknowledged.

References

1. K. E. McCulloh, C. R. Tilford, C. D. Ehrlich, and F. G. Long, "Low Range

Flowmeter for Use with Vacuum and Leak Standards," in preparation for J

Va. Sci. Technol. A.

2. R. Hyland, C. D. Ehrlich, C. R. Tilford, and S. Thornberg, "Transfer Leak

Studies and Comparison of Primary Leak Standards at NBS and SNL, " J . Vac

Sci. Technol. A . vol. 4, p. 334 (1986).

3.

C. D. Ehrlich, "A Note on Flow Rate and Leak Rate Units," J. Vac. Sci.

Technol. A . Vol. 4, 2384 (Sept. /Oct. 1986).

Figure 1. Schematic diagram of the NBS primary leak standard.
Table 1. Measurement uncertainties of the piston flowmeter (in percent),

uncertainties of the bellows flowmeter are the same except at the lowest

tabulated flowrate, where they are marginally smaller. Random errors are evaluated at three times the standard deviations or maximum observed

deviations

Flow Rate (mol/s) and Piston Size

10' 6 to 10' 9 lO-io 10' 11

1 inch 1 cm 1 cm

SP 1 /P 1 Systematic

Random

0.50

0.01

0.50

0.01

0.52

0.10

5 ( AV ) /AV Area Systematic

Length Systematic

0.001

0.10

0.001

0.10

0.001

0.10

ST1 /T1 Systematic

Random

0.003

0.01

0.003

0.01

0.003

0.01

8 (At) /At Random 0.01 0.10 0.10

V2 6P Systematic 0.20 1.30 1.30

AV P x

v, £1

AV

Systematic 0.006 0.04 0.04

Leakage Systematic 0.01 0.06 0.06

Systematic

(Linear Sum)

0.82 2.00 2.02

Random

(RMS Sum)

0.02 0.10 0.14

Total 0.84 2.10 2.16

The

45
Radiographic Image Quality Evaluation At Very Low And Very High Eneraies

R. C. Placious

Ionizing Radiation Division

Center for Radiation Research

The measurement of image quality is a basic concern of industrial users of

radiographic or radiologic imaging equipment because image quality relates

directly to detection sensitivity for flaws or other discontinuities. A

recently developed national standard (ASTM E 746 and NBS SRM 1844) permits

each aspect of a total radiography system to be evaluated in terms of its

effect on image quality. However, this standard was developed for use at

200 kV and cannot be applied at very low kilovoltage, such as is commonly used

in composite material inspections, or in the megavoltage region, which is

required for the inspection of thick-walled materials such as pressure vessels

or armor plate. NBS is remedying this deficiency by developing suitable

testing devices and formulating techniques for their evaluation.

At 30 kV, image quality is strongly dependent on the spectrum (beam quality)

of the x-ray source. For field use, the desired spectrum is achieved by filtering the x-ray beam and then adjusting the voltage until the half-value lay- er (HVL) in a given material is a specified thickness. The harder portion of

the spectrum (the high-energy end) is least affected by the filtration and is

similar for all users. For our purposes, 1100 aluminum alloy was specified

for both filtration and HVL. Outside laboratories (DuPont and Fuji) confirmed

this prescription for beam quality. The proposed image quality device was modeled after SRM 1844 except that, because of the low energies involved, lucite is used for the image quality indicators (IQI) and the absorber. Note

that while the voltage adjustment is made with aluminum the image quality indicator is fabricated from lucite. The principal laboratories participating

in the round-robin evaluation of this device according to our protocol are Agfa Gevaert, DuPont, Eastman Kodak, Fuji, McDonnell -Douglas , and Monsanto.

Over the past two years a test device and an associated standard for measuring

image quality at very high energies were developed and tested. On the basis

of over 500 tests it is clear that the proposed device and standard does

indeed detect small changes in image quality and can be used to evaluate the

effect of film type and other parameters on image quality. The draft document, written by Dan Polansky and R. C. Placious, was reviewed by a task fore,

of outside specialists in high-energy radiography and, following several suggested changes, will be submitted for ASTM peer review and acceptance. Tin

outside laboratories cooperating in this work on a high-energy image quality

standard include Combustion Engineering, Babcock & Wilcox, X-Ray Industrie .. and Lynchburg Foundry.

In a related activity, we have supplied several other laboratories with bean

attenuation data in copper at 5Q kV intervals from 50 to 300 kV The ohjer

tive is a means for voltage calibration for users of x-ray equipment. Coj ; is a logical material to use for this because of ready availability in big.', purity form and convenient thicknesses. Furthermore, the attenuation <-r<>

46
sections for copper in this energy range vary over a factor of 20 or so, which

causes the normalized attenuation curves to have different slopes for each of

these energies. We are now awaiting attenuation measurements in copper by our collaborating laboratories, which include Lawrence - Livermore , Monsanto, Agfa,

Eastman Kodak, and X-Ray Industries.

Standard Test Methods for Characterizing Performance of Thermal Imaging

Systems

J . Cohen

Radiometric Physics Division

Center for Radiation Research

Infrared thermography is the process whereby the thermal radiation from an object, invisible to the unaided eye, is remotely detected and rendered into a visible image of varying contrast. All motion, mechanical and electronic,

generates heat; excessive or imbalanced heating and hot spots in an equipment,

device, or facility generally forebodes failure. Thus, for decades, industry

has routinely used thermography for nondestructive evaluation in a wide

variety of applications; e.g., monitoring electrical transformers, motors,

bearings, and tube furnaces, and for testing printed circuit boards. Further,

subsurface defects, such as corrosion pits and delamination, may be investigated with the aid of an external heat source. Notwithstanding, the past few

years have been witness to an explosive growth in new and sophisticated applications of thermography, brought about, on the one hand, by newly available

digitized imagers with data storage, computational, and temperature measurement capabilities, and new emphases on automation, quality assurance, and

reliability, on the other. Thus, thermography is now being successfully used

for design verification, quality assurance testing, in-process monitoring and

control, and accurate temperature determinations.

These new, important roles of thermography underscore the vital importance of

standards for characterizing the performance of thermal imagers. Performance

standards make possible instrumental calibration, monitoring, and intercomparisons at the marketplace and in the laboratory; further, the data may serve as

a guide to experimental design and feasibility studies.

The objective of this project is to develop new standard test methods for

characterizing performance of thermal imaging systems. Three performance mea- sures, which are those of greatest value to the user, are to be addressed

sequentially. These are (1) minimum resolvable temperature difference (MRTD)

(2) minimum detectable temperature difference (MDTD) , and (3) noise equivalent

temperature difference (NEAT). MRTD and MDTD relate to imagery, while NEAT is a measure of the temperature sensitivity of the instrument.

Thus far, standards work on this project has dealt solely with MRTD, which is a measure of the compound system- observer ability to spatially resolve temperature differences in a standard test pattern (target) by observing its display

on a monochrome video monitor; hence, it relates to the capacity to distinguish details in imagery. Figure 1 depicts examples of standard blackbody bar

targets of specified geometry and temperature. With fixed TB <T, MRTD is the

threshold AT=T-TB at which the observer can just distinguish the four bars.

47
Plainly, MRTD is a function of the linear period of the bars and the observa

tion distance. Details of the test method for measuring MRTD of thermal

imaging systems used for NDT work are given in a new draft standard which is

currently in the ASTM approval process and early adoption is expected.

Figure 1. Targets used for MRTD determinations. The target is a periodic 4-

bar chart of aspect ratio (width

length) 1:7. T is the temperature of a bar,

Tb is the background temperature , and T>TB

.

Thermal Waves Visualized by Holographic Interferometry

G. H. Kaufmann and C. M. Vest

Dept, of Mechanical Engineering and Applied Mechanics

The University of Michigan

A technique was developed for using optical holographic interferometry to

investigate the propagation of long thermal waves through metal ob}ccts.

These waves were created when the surfaces of thin aluminum plates were subjected to a slowly modulated heat source. In this manner surface deformations

large enough to be observed by holographic interferometry were induced. A

stroboscopic technique was used to visualize the radial propagation of the

thermal wave. Predicted variations of fringe properties, such as visibility

and density, were verified experimentally. The measured out-of-plane deflections agree quite well with the analytical thermoelastic solution.

A scheme for detection of large flaws, based on this combined technique, was also developed. Preliminary results showed that flaw detection can b< improved when thermal waves, rather than unmodulated heating, are us< >1 in

48
holographic nondestructive testing. Increasing the modulation frequency is

desirable. However, as frequency is increased, either more intense heating or increased interferometric sensitivity is required. From the perspective of

thermal waves, the technique is interesting in that it produces an analog

whole -field output which is conceptually equivalent to parallel processing of

the entire image rather than to forming it by point-by-point scanning.

Theoretical Investigation of Acoustic and Thermal Wave Scattering

R. D. Mountain

Thermophysics Division

Center for Chemical Engineering

A spatial moment representation of acoustic wave scattering was previously

developed for both transient and steady state conditions. This formulation,

which employs the Born approximation, provides a clear way of understanding

how information on the size and shape of isolated scatterers is contained in

scattered acoustic signals. During the past year, this formulation was used

to help understand the reasons for the apparent success of "engineering"

approaches, which use the Born approximation for acoustic wavelengths and

scatterer dimensions for which it is known to be inapplicable.

The utility of the moment formulation for the acoustic case encouraged an attempt to make a similar formulation for the thermal wave case. Two physical

situations were examined for which analytical solutions exist. These were the

scattering of a thermal wave by a horizontal, penny- shaped crack, and the

reflection of a thermal wave by a layer under the surface to which the thermal

input is applied. While an expansion in powers of the frequency of the source can be made, the desired information on the position, shape, etc., of the scatterer is not easily extracted in this way. This is due in large part to the

critical damping of the input signal. It appears that the moment approach to

thermal waves is not likely to be a useful one.

Determination of Green's Functions and Their Application to Acoustic Emission

and Ultrasonics

N. N. Hsu

Automated Production Technology Division

Center for Manufacturing Engineering

Common to both acoustic emission and ultrasonics, the central theory in need

is an accurate quantitative description of the generation, propagation,

interaction with boundaries, and detection of the transient stress waves in a solid. Our approach has been based upon the concept of a generalized Green's

function representation. Our objective is to determine the Green's functions

of a solid of arbitrary shape and material properties, either theoretically or experimentally, or both if possible. Once the Green's function is known for a particular specimen, general test results can be predicted by simple integration. Numerical simulation of acoustic emission and ultrasonic tests then can

be carried out to provide insight or to help interpret the test results.

49
Last year we reported the formulation and development of procedures for the

experimental determination of Green's function. The concept involves two

novel ideas: (1) the theoretical formulation of a probing waveform which

facilitates the deconvolution process; (2) the design and construction of a system, a transducer pair together with high speed digital to analog

conversion and power amplifier, which introduces a mechanical pulse of

specified waveform and detects the propagated transient wave without loss of

fidelity. Feasibility test results were encouraging.

This year we made progress in improving the design and computational procedure

for the experimental determination of the Green's functions. The computational algorithm has been successfully transferred from the main NBS computer

to local laboratory minicomputers. Consequently, experimentally acquired data can be processed in the laboratory without tedious digital data transfer.

Recently we annotated and made portable our computer program to compute a large number of the Green's functions for an infinite plate [1], The program

now runs on IBM PC or compatibles rather efficiently. It is made available to

the public mainly for its possible use for acoustic emission transducer

calibrations. However, we have found many practical applications of the

theoretically computed Green's functions in the development of various

techniques related to ultrasonic testing of materials. We summarize these

applications

(1) Ultrasonic Receiver Calibration- -Development of Hi-Fi Transducers - -The

ability to properly characterize and calibrate transducers provides the only means to compare, select, and develop new transducers. The computed Green's

function serves as an ideal reference standard.

(2) Impact-Echo Technique for Flaw Detection- -A point-source point-receiver

pulse -echo technique to locate flaws within hardened concrete was developed .it NBS [2]. A large concrete slab was cast with a known internal flaw. Steel

balls of selected sizes were dropped onto the slab as a point impact source and an NBS conical displacement transducer was used as a point-receiver. Tin

numerical convolution of impact force-time history and the Green's function

(G33) were used to help interpret experimental signals. This impact-echo

technique with the help of the plate Green's function should be useful for

testing massive or high loss composite materials.

(3) Novel UT Measurement Technique -- Self Calibration of Thickness

Measurement- -Shear Wave Speed Without Using a Shear Transducer - -The normal

displacement at one point due to point impact at another point has succc.s i v» sharp arrivals which correspond to reflected and mode-converted rays. The

time intervals between various arrivals provide the time - of -

1 ight

information from which either path length or wave speeds can be derived. Sh

in Figure 1 is a simulated time record. It is generated by using the Gre«-n':

function (G33) assuming the source and the detector are separated one plat*

thickness apart. As shown in the figure, the arrivals of reflected waves I’

- PS, P

A

, etc., all can be detected. The corresponding wave speeds of inten

can then be computed by solving simple geometric ray path problems. Note t! the arrivals of various rays have different peak amplitudes. The numerical

simulation based upon Green's function computation thus provides an ea.-.v method to optimize the test configuration for specific applications.

50
(4) Modeling for Optical/Thermal Sources of Ultrasound and Distributed

Receivers - -The Green's functions provide a basic tool for evaluating point and

distributed thermo -mechanical sources and point and distributed receivers.

For distributed sources and receivers the input or output must be integrated

over the area of distribution to obtain a prediction of test results. This

extension of the application of Green's functions has been formulated and will

be compared with measurements using a distributed receiver in the form of a circular aperture capacitance receiver (Breckenridge , NBS) and with

measurements of displacement at a point due to a laser source distributed over an annular ring on the surface of a plate [3], For point laser generation of

ultrasound, the Green's functions for a normal source or dipole source are directly applicable. Buried normal force and dipole sources were simulated by

a laser pulse incident on the bottom of a small slot in a plate with and

without an oil drop. Normal displacement off epicenter was detected using an interferometer. The theoretical results obtained by convolving the appropriate Green's function with the assumed source-time compare well with the

measured displacement- time history shown in Figure 2 [4]

G33 X-1.0 SURFACE

so

60

40

30

20

R

\

P

2 PS

A

p4

A >\ P

3 S

p s'

\

S

2

1

-20

-30

04 OB 12 lfl 2A 2jB

me

Figure 1. Simulated displacement versus time record for point impact

generated transient. Detector and source are on the same side of the plate at one thickness apart.

51
Figure 2. Comparison of experimental displacement waveforms at x = 0.5h to

theoretical predictions of wave propagation theory. (a) Horizontal dipole

with step- like time dependence; (b) Normal force with pulse- like time

dependence

References

1. N. N. Hsu, "Dynamic Green's Functions of an Infinite Plate - A Computer

Program," NBSIR 85-3234, August 1985. Available from NTIS as PB86 - 143856/A

2. N. J. Carino, M. Sansalone, and N. N. Hsu, "A Point Source-Point Receiver.

Pulse-Echo Technique for Flaw Detection in Concrete," ACI Journal . 199-208, March-April 1986.

3. P. Cielo, F. Nadeau and M. Lamontagne , "Laser Generation of Convergent

Acoustic Waves for Materials Inspection," Ultrasonics . 55-61, March L'H .

4. D. A. Hutchins, K. Kundren, R. P. Young, and N. N. Hsu, "Laser Simul.it ion

of Buried Acoustic Emission Sources," J. Acoustic Emission, to be

published

52
Performance Assessment of Fluorescence Measurements

K. L. Eckerle, J. J. Hsia, C. L. Chang, and K. D. Mielenz

Radiometric Physics Division

Center for Radiation Research

Surface discontinuities in solid materials can be detected by nondestructive

evaluation using fluorescent liquid penetrants. The objective of this project

is the performance assessment of fluorescence measurements made on these

penetrants. This is possible since quantitative measurements may be made of

fluorescence brightness by using instruments simulating human eye

responsivity . Our approach has been to develop hardware and software for a reference spectrofluorimeter . This spectrofluorimeter is a two -monochromator

instrument which allows mathematical simulation of various spectral

distributions for sources, detection systems, and human eye response.

Work this year included the development and study of novel material samples

which could serve as transfer standards for fluorescence measurements. The

preliminary method of production is described elsewhere [1]. The samples were sintered mixtures of inorganic phosphors and polytetrafluorethylene resin.

Four samples, in colors blue, green, yellow, and orange, were manufactured.

Preliminary studies on these samples were performed for stability of emission

spectra to ultraviolet light exposure, uniformity, temperature, and

concentration. All measured spectra were corrected for the relative spectral

responsivity of the detection system. Only two, the yellow and the blue, that can be excited with wavelengths near 365 nm, are suitable for possible use for

performance assessment of fluorescence measurements.

We have suggested standardizing ultraviolet irradiance meters for testing

irradiance levels and fading. A definition of relative response of these

ultraviolet meters would be a step toward standardization. To this end,

Jack Hsia has initiated coordination efforts of ASTM Committee E-7, UV meter

manufacturers, international subcommittee on UV meters (with its chairman at

BAM in Germany) , and the NBS

References

1. V. R. Weidner, R. Mavrodineanu, and K. L. Eckerle, "Sintered Mixtures

of Phosphors in Polytetraf luorethylene Resin for Fluorescence Standards,"

App . Opt. 25 . 832 (1986).

Military Standards for Nondestructive Evaluation

L. Mordfin

Office of Nondestructive Evaluation

Institute for Materials Science and Engineering

Under a long-term contract with the Army Materials Technology Laboratory,

engineers and scientists in the NDE Program have been developing new and

improved military standards for NDE. Among the project's accomplishments

since its inception were completion of two documents which were approved

following full tri-service coordination in the Department of Defense and by

relevant industrial contractors.

53
Glossary of Terms and Definitions for Acoustic Emission Testing

Procedures, MIL-STD-1945 (developed by D. G. Eitzen, Automated Production

Technology Division, Center for Manufacturing Engineering) .

Inspection, Magnetic Particle, MIL-STD-1949 (developed by L. J.

Swartzendruber , Metallurgy Division, Institute for Materials Science and

Engineering)

During the past year E. H. Eisenhower (Office of Radiation Measurement, Center

for Radiation Research) completed a third draft glossary of terms for radiography. This draft is now undergoing the third and final DOD coordination.

Twelve master radiographs - -which will be used to produce test patterns for

evaluating the visual acuity of radiographic interpreters - -were developed by

R. C. Placious (Ionizing Radiation Division, Center for Radiation Research).

The total set, which will comprise 76 patterns, is scheduled to be completed

during the coming year.

A procedural document for the primary calibration of acoustic emission (AE)

transducers, which was developed by D. G. Eitzen and F. R. Breckenridge

(Automated Production Technology Division) , was approved by ASTM as Standard

Method E 1106-86. This is now being used by Eitzen and Breckenridge to

formulate a military standard for the secondary calibration of AE transducers.

A field calibration document, which will include an exposition of N. N. Hsu's

award-winning pencil source, is being developed jointly by NBS and the

Physical Acoustics Corporation.

T. E. Capobianco and F. R. Fickett (Electromagnetic Technology Division,

Center for Electronics and Electrical Engineering) are developing a standard

practice, suitable for use in the field, for qualifying eddy current coils. A preliminary version of the standard was presented at the 35th Defense

Conference on Nondestructive Testing in October 1986.

The first draft of a proposed standard on NDE of corrosion of ammunition was prepared by A. C. Fraker and A. W. Ruff (Metallurgy Division, Institute for

Materials Science and Engineering) . The draft was coordinated through DOD and

revisions are now in progress.

54
NDE of Shipping Casks for Spent Nuclear Fuel

D. G. Eitzen, Automated Production Technology Division

Center for Manufacturing Engineering

R. C. Placious, Ionizing Radiation Division

Center for Radiation Research

L. J. Swartzendruber , Metallurgy Division

Institute for Materials Science and Engineering

L. Mordfin, Office of Nondestructive Evaluation

Institute for Materials Science and Engineering

When spent fuel from nuclear reactors must be transported by rail or truck,

Federal regulations require that it be enclosed in shipping casks that satisfy

a number of stringent requirements. A new design configuration that is

presently under consideration for such casks consists of metal cylinders

approximately 17 ft. (5 m) long, 8 ft. (2.5 m) in diameter, with 14-in.

(35 -cm) thick walls. The casks are to be fabricated by casting with one integrally closed end. The materials being considered for this application

are austenitic steel, ferritic steel, and nodular cast iron.

The thick walls are needed in order to absorb most of the radiation emitted by

the contents. A much more demanding requirement is that the casks be capable

of withstanding severe transportation accidents without a breach of the cask

walls that would permit the escape of any radiation or radioactive fluid. In

order to satisfy this requirement, it is necessary that the casks be inspectable to the extent that no potentially critical flaw in the cask walls may go

undetected.

The National Bureau of Standards conducted a study for the Sandia National

Laboratories to evaluate the inspectability of the casks. The study showed

that current NDE technology is adequate for inspecting the casks provided that

the inspection personnel are well trained in their respective methods and that

they are experienced with the equipment and their specific techniques and have

been properly qualified in this application.

The capabilities of many NDE techniques were evaluated in the study. These

techniques were based upon all of the principal NDE methods in use today. For

most of these methods the precise characteristics of the cask material are largely irrelevant, although certain general properties (e.g., magnetic versus non-magnetic) are important. For the ultrasonic methods, however, detailed

specifications of the cask material are critical, mainly because they

determine whether the ultrasonic beam can satisfactorily penetrate the thick

sections of the cask.

Generally speaking, wrought ferritic steels do not pose significant obstacles

to ultrasonic inspection. Austenitic steels, on the other hand, and

particularly cast austenitic steels, are usually difficult, if not impossible,

for ultrasonic NDE, particularly in large thicknesses, because of the large,

anisotropic grain structure in the material. This problem can be alleviated,

to some extent, by certain thermo -mechanical treatments. The ultrasonic

55
inspectability of nodular cast iron can range from impossible to very good

depending upon the size, distribution and shape of the nodules, the grain

structure, and the general cleanliness of the material. The key points are that the cask materials should be selected on the basis of a careful test

program, and that the processing of the material and the manufacture of the

casks should be rigorously controlled in order that it be satisfactorily

inspectable by ultrasonic techniques.

Two general approaches are available for ultrasonic inspections of casks, one based upon conventional ultrasonic techniques and one upon advanced

techniques. Conventional techniques (e.g., amplitude -based, manual, pulseecho contact scanning in several directions) can reliably detect all

discontinuties having reflectivities equivalent to that of a 10-mm (0.4-in.)

flat-bottomed hole. While this does not mean that such techniques can detect

every 10-mm flaw, they do serve as a general measure of the quality of the

material. If a given quality level can be shown, say by mechanical tests on sample casks, to be acceptable, then such ultrasonic inspections can evaluate

the acceptability of the casks relative to the given quality level.

Advanced ultrasonic inspection techniques (e.g., Amplituden und Laufzeit -Or ts

Kurven, amplitude and transit-time dynamic curves (ALOK) , synthetic aperature

focusing technique (SAFT)) have been developed in recent years which employ

transducer arrays or synthetic arrays and provide images of flaws. It is

believed that a system based on one of these techniques can be developed that

could reliably detect and evaluate critical cask flaws provided that

inspectability is designed into the casks.

Radiology, like ultrasonics, is capable of detecting flaws in the interior of

cask walls. Both film techniques and electronic imaging techniques are available today which can provide a high level of flaw detectability in this

application. With properly selected equipment, very small cracks can be

located if they are oriented parallel to the x-ray beam (perpendicular to the

cask wall) . The sensitivity is not as good for internal planar flaws oriented

perpendicular to the x-ray beam (parallel to the cask wall). Substantially

greater sensitivity in the thickness direction is obtainable by radiation

gauging.

Surface methods of NDE are widely used in the casting industry because the

most severe types of common casting imperfections are usually visible at the

surface. Visual inspection is recommended for all castings and, when carried

out by trained inspectors with knowledge of casting procedures and defect:;, i: highly reliable except for very fine (hairline) cracks.

Magnetic particle inspection and liquid penetrant inspection are both capable

of detecting extremely fine surface flaws under the proper conditions and wit!;

qualified personnel and inspection materials. Magnetic particle inspection i only useful for ferromagnetic materials, such as ferritic steel and nodular

cast iron, but not austenitic steel. Excellent sensitivity could be obtai on cast ferritic steel, or on nodular iron having well-controlled nodule size

at the surface and good surface finish.

Liquid penetrant inspection may be used on magnetic or non-magnetir matt i i

• and is at least as sensitive as magnetic particle inspection on clean Si faces. Cracks filled with oxide, oil, grease, or even water make the ; • <>:

56
penetrants difficult, whereas these contaminants do not usually affect

magnetic particle inspection.

If a higher level of detectability is needed for surface flaws the eddy

current method merits consideration. Used properly, eddy current techniques

can detect minute surface flaws in austenitic steel. The high permeability of

ferrite would be expected to cause problems with the other cask materials but, even so, the eddy current method would undoubtedly provide a higher level of

reliability in the detection of surface cracks than either magnetic particle

or liquid penetrant inspection. The principal deterrent to the use of the

eddy current method here is that it has not been widely used in the casting

industry. Therefore, its application to cast casks would require some preparatory development work and specialized training.

57
APPENDICES

A. NDE SEMINARS AT NBS

Dr. Richard L. Weaver . University of Illinois, Urbana, IL

"Acoustic Emission Source Characterization by Means of Diffuse Waves:

Theory and Experiment"

October 10, 1985

Professor Paul Hoeller . Fraunhofer- Institute fur zerstdrungsfreie

Prufverfahren, Saarbrucken, F.R. Germany

"Acoustic Emission Source Indentification by Signal Processing: Recent

Progress in Nondestructive Structure and Stress Analysis"

October 23, 1985

Dr. Ferevdoun Faridian . University College, London, England

"Acoustic Microscopy"

October 24, 1985

NDE Poster Session

December 4, 1985

Dr. Emanuel Segal . Technion- Israel Institute of Technology, Haifa, Israel

"NDE of Composites Using Computerized Tomography"

March 25, 1986

Dr. Spencer Bush . Review & Synthesis Associates, Richland, WA

"Ultrasonic Reliability: Some Recent Results"

September 16, 1986

B. INVITED TALKS BY ONDE STAFF

"Summary and Conclusions of Workshop," H.T. Yolken, A National Forum on the

Future of Automated Materials Processing in U.S. Industry -- The Role of

Sensors, Santa Barbara, California, December 17, 1985.

"Optical NDE at NBS," G. Birnbaum, Society of Photo-Optical Instrumentation

Engineering, Los Angeles, California, January 23, 1986.

"The Role of NDE Sensors in Automated Materials Processing," H.T. Yolken,

Texas A&M University, College Station, Texas, February 5, 1986.

"The Role of NDE Sensors in Automated Materials Processing," H.T. Yolken.

University of Houston, Department of Mechanical Engineering, Houston, T< Februrary 6, 1986.

"International Standards for Nondestructive Testing: What, Why and How,"

L. Mordfin, Cleveland Section, American Society for Nondestructive Test in,

Brecksville, Ohio, March 17, 1986.

58
"Ferromagnetic Nondestructive Evaluation for Production and Inspection,"

H.T. Yolken, Second National Seminar on Non-Destructive Evaluation of

Ferromagnetic Materials, Houston, Texas, March 19, 1986.

"Optical Methods in NDE , " G. Birnbaum, NBS Analytical Chemistry/Materials

Science Workshop, Gaithersburg, Maryland, April 18, 1986.

"The Role of Nondestructive Evaluation Sensors in the Automated Processing of

Ceramics," H.T. Yolken, American Ceramic Society, Chicago, Illinois,

April 29, 1986.

"Summary and Conclusions of a National Forum on the Future of Automated

Materials Processing in the U.S.--The Role of Sensors," H.T. Yolken, A

National Forum on the Future of Automated Materials Processing in the U.S.--

The Roles of Process Models, Artificial Intelligence and Computer Integration,

Gaithersburg, Maryland, May 19, 1986.

C. PUBLICATIONS

Following is a partial listing of NBS reports and publications on NDE and

related topics that have been issued since last year's Technical Activities

report was prepared. A more complete compilation will be presented in ONDE's

annual bibliography with abstracts.

B.A. Auld, S. Jefferies, J.C. Moulder and J.C. Gerlitz, "Semi-Elliptical

Surface Flaw EC Interaction and Inversion: Theory," Review of Progress in

Quantitative Nondestructive Evaluation 5A . pp. 383-393 (1986).

M. Baum, "Surface Roughness Monitor for Advanced Manufacturing Developed," NBS

Research Reports. NBS SP 680-5 . p. 9 (May 1986).

N. F. Berk and K.A. Hardman - Rhyne , "Characterization of Alumina Powder Using

Multiple Small Angle Neutron Scattering. I: Theory," J. Appl. Crvst. 18 . pp. 467-472 (1985).

N.F. Berk and K.A. Hardman - Rhyne , "The Phase Shift and Multiple Scattering in

Small Angle Neutron Scattering: Application to Beam Broadening from

Ceramics," Phvsica 136b . pp . 218-222 (1986).

Y. Berlinsky, M. Rosen, J.A. Simmons and H.N.G. Wadley, "Acoustic Emission:

An NDE Technique for Characterizing the Martensitic Transformation," Review of

Progress in Quantitative Nondestructive Evaluation 5B . pp . 1345-1354 (1986).

G. Birnbaum, ed. , "Office of Nondestructive Evaluation, Technical Activities

1985," NBSIR 85-3187, 225 pp . (Nov. 1985).

G. Birnbaum, G.S. White and C.M. Vest, "Laser Generated and Detected

Ultrasound and Holographic Methods," Pressure Vessel and Piping Technology, A

Decade of Progress - 1985 . pp . 661-669 (ASME, 1985).

59
P.J. Blau and B.R. Lawn, eds . , Microindentation Techniques in Materials

Science and Engineering . ASTM STP 889, 300 pp (1986).

T.E. Capobianco, F.R. Fickett and J.C. Moulder, "Mapping of Eddy Current Probe

Fields," Review of Progress in Quantitative Nondestructive Evaluation 5A . pp

705-711 (1986).

T.E. Capobianco, J.C. Moulder and F.R. Fickett, "Flaw Detection with a Magnetic Field Gradiometer , " Proc . 15th Symposium on Nondestructive

Evaluation , pp. 15-20 (NTIAC, 1985).

A . S . Carasso and N.N. Hsu, "L ® Error Bounds in Partial Deconvolution of the

Inverse Gaussian Pulse," SIAM J. Appl. Math. 45, No. 6 (Dec. 1985).

N.J. Carino, M. Sansalone and N.N. Hsu, "A Point Source - Point Receiver,

Pulse-Echo Technique for Flaw Detection in Concrete," J. Amer. Concrete

Institute . pp . 199-208 (Mar. -Apr. 1986).

Y.-W. Cheng, "Fitness-for-Service Criteria for Assessing the Significance of

Fatigue Cracks in Offshore Structures," NBS TN 1088, 72 pp . (Aug. 1985).

A.V. Clark, Jr. and J.C. Moulder, "Ultrasonic Determination of PrincipalStress Differences for a Slightly Anisotropic Residual Stress Specimen," Proc

15th Svmp. on Nondestructive Evaluation , pp . 260-270 (NTIAC, 1985).

A.V. Clark, Jr. and J.C. Moulder, "Absolute Ultrasonic Determination of

Stresses in Aluminum Alloys," Review of Progress in Quantitative

Nondestructive Evaluation 5B . pp . 1449-1459 (1986).

A.V. Clark, Jr., J.C. Moulder, R.E. Trevisan, T.A. Siewert and R.B. Mignogna,

"Ultrasonic Techniques for Residual Stress Measurement in Thin Welded Aluminum

Plates," Review of Proeress in Quantitative Nondestructive Evaluation 5B . pp

1461-1472 (1986).

S.K. Datta and H.M. Ledbetter, "Effect of Interface Properties on Wave

Propagation in a Medium with Inclusions," Mechanics of Material Interfaces . A. P.S. Selvadurai and G.Z. Voyiadjis, eds., pp . 131-142 (Elsevier, N.Y.,

1986).

S.K. Datta and H.M. Ledbetter, "Waves, Microstructures and Effective -Medium

Approximation," Mechanics of Dislocations , pp . 213-223 (ASM, 1985).

P.P. Delsanto and A.V. Clark, Jr., "Rayleigh Wave Propagation in Deformed

Orthotropic Materials," Review of Progress in Quantitative Nondestm. -i i vc Evaluation 5B . pp . 1407-1414 (1986).

B. E. Droney, F.A. Mauer, S.J. Norton and H.N.G. Wadley, "Ultrasonic Sensors :<> Measure Internal Temperature Distribution," Review of Progress in

Quanititative Nondestructive Evaluation 5A . pp . 643-650 (1986).

C. D. Ehrlich, "A Note on Flow Rate and Leak Rate Units," J . Vac . Sc

. Terhn < A 4, No. 5 (Sept. /Oct., 1986).

60
B.M. Fanconi, F.W. Wang, D. Hunston and F. Mopsik, "Cure Monitoring for

Polymer Matrix Composites," Materials Characterization for Systems Performance

and Reliability . J.W. McCauley and V. Weiss, eds . , pp . 275-291 (Plenum, 1986).

S.E. Fick, N.N. Hsu and T.M. Proctor, "The Design and Calibration of a Novel

Piezoelectric Point Contact High Fidelity Ultrasonic Transducer," Proc . 11th

World Conf. on Nondestructive Testing , pp . 891-893 (ASNT, 1985).

J.T. Fong, "Analysis of Sectioning Data of PVRC 251-J for Estimating Flaw

Fabrication Reliability," NDE Reliability Through Round-Robin Testing . J.T. Fong, L. Mordfin, O.F. Hedden and S.H. Bush, eds. (ASME, 1986).

J.T. Fong, "A Summary and Update of the 1983 ASME -ASNT- PVRC Portland

Symposium," NDE Reliability Through Round-Robin Testing , J. T. Fong,

L. Mordfin, O.F. Hedden and S.H. Bush, eds. (ASME, 1986).

J.T. Fong and J.J. Filliben, "A Data Analysis Methodology as Applied to the

PVRC Round-Robin NDE Test Program," NDE Reliability Through Round-Robin

Testing . J.T. Fong, L. Mordfin, O.F. Hedden and S.H. Bush, eds. (ASME, 1986).

J. T. Fong, L. Mordfin, O.F. Hedden and S.H. Bush, eds., NDE Reliability

Through Round-Robin Testing . NDE-Vol. 1, 292 p (ASME, 1986).

D.A. Garrett, et al, "Neutron Radiography," Section 12 in Nondestructive

Testing Handbook. 2nd Edit.. Vol. 3. Radiography and Radiation Testing . L.E. Bryant and P. Mclntire , eds., pp . 532-563 (ASNT, 1985).

K. A. Hardman- Rhyne , K.G. Frase and N.F. Berk, "Applications of Multiple Small

Angle Neutron Scattering to Studies of Ceramics Processing," Phvsica 136b . pp

218-222 (1986).

K.A. Hardman-Rhyne and N.F. Berk, "Characterization of Alumina Powder Using

Multiple Small Angle Neutron Scattering. II: Experiment," J. Appl. Crvst. 18 . pp. 473-479 (1985)

K.A. Hardman-Rhyne and N.F. Berk, "Ceramic Material Characterization Using

Small Angle Neutron Scattering Techniques," Materials Characterization for

Systems Performance and Reliability . J.W. McCauley and V. Weiss, eds., pp 257-

269 (Plenum, N.Y., 1986).

D.A. Hill, "Radio Propagation in a Coal Seam and the Inverse Problem," Proc

1985 Inti. Symp , on Antennas and EM Theory , pp . 422-427 (1985).

N.N. Hsu, "Dynamic Green's Functions of an Infinite Plate - A Computer

Program," NBSIR 85-3234, 66 pp (Nov. 1985).

D. Hunston, R. Dehl and W.-L. Wu, "Polymer Composites -- Challenges and

Research Trends," Mechanical Engineering 108 . No. 3, pp . 52-56 (March 1986).

R.W. Hyland, C.D. Ehrlich, C.R. Tilford and S. Thornberg, "Transfer Leak

Studies and Comparisons of Primary Leak Standards at the National Bureau of

Standards and Sandia National Laboratories," J. Vac. Sci. Technol. A 4, No. 3,

pp . 334-337 (May/June 1986).

61
R.W. Hyland and C.R. Tilford, "Zero Stability and Calibration Results for a Group of Capacitance Diaphragm Gages," J. Vac. Sci. Technol. A 3, p. 1731

(1985).

M.P. Jones and G.V. Blessing, "Real-Time Ultrasonic Nondestructive Evaluation

of Green State Ceramic Powders During Compaction," Nondestructive Testing

Communication 2, No. 5 (1986).

M.P. Jones, G.V. Blessing and C.R. Robbins, "Ultrasonic Elasticity Study of

Sintered Ceramics and Their Green States," Proc . 1985 Ultrasonics Symposium

(IEEE, 1985).

M.P. Jones, G.V. Blessing and C.R. Robbins, "Dry-Coupled Ultrasonic Elasticity

Measurements of Sintered Ceramics and Their Green States," Materials

Evaluation 44, pp . 859-862 (June 1986).

A.H. Kahn, K.R. Long, S. Ryckebusch, T. Hsieh and L.R. Testardi,

"Determination of Electrical Conductivity Profiles from Frequency-Sweep Eddy

Current Measurement," Review of Progress of Quantitative Nondestructive

Evaluation 5B . pp . 1383-1391 (1986).

C.P. Kirk and D. Nyyssonen, "Modeling the Optical Microscope Images of Thick

Layers for the Purpose of Linewidth Measurement," Optical Microlithography . Proc. SPIE 538 . pp . 179-187 (1985).

H.M. Ledbetter, M.W. Austin and J.E. Callanan, "Internal Friction and Dynamic

Young Modulus of a Bituminous Coal," Physical Methods for Fossil Fuel

Characterization , pp . 127-133 (ACS, 1985).

H.M. Ledbetter and S.K. Datta, "Effective Wave Speeds in a SiC-ParticleReinforced A2. Composite, J. Acoust. Soc , Amer. 79, pp . 239-248 (1986).

H.M. Ledbetter, Ming Lei and M.W. Austin, "Young Modulus and Internal Friction

of a Fiber-Reinforced Composite," J. Appl. Phys . 59 . pp . 1972-1976 (1986).

M. Linzer, ed. , Ultrasonic Imaging 8 (Academic Press, 1986).

L. Mordfin, "Nondestructive Evaluation," Chapter 30 in Materials and

Processes . 3rd Edition, J.F. Young and R.S. Shane, eds

, pp . 1495-1519 (Marcel

Dekker , 1985)

L. Mordfin, ed. , "NDE Publications: 1983," NBSIR 86-3396, 27 pp . (April

1986)

L. Mordfin, "Residual Stresses: Nondestructive Evaluation," Encyclopedia of Materials Science and EnEineering . pp . 4188-4194 (Pergamon, 1986).

Tinh Nguyen, "Thermal-Wave Imaging of the Microstructure and Corrosion of

Cold-Rolled Steel under Protective Coatings," I&EC Product Research a nd

Development 24 . p. 496-500 (Amer. Chemical Soc., Dec. 1985).

62
Tinh Nguyen and E. Byrd, "Reflection/Absorption Fourier Transform Infrared

Spectroscopy of Degradation of Coatings on Steel," Proc. Svmp . Polymeric

Materials Sci. Engrg. 53 . pp . 568-573 (Am. Chem. Soc., 1985).

Tinh Nguyen and M. McKnight, "Nondestructive Early Detection of Corrosion and

Delamination Under Protective Coatings Using Thermal-Wave Microscopy," NBSIR

85-3187 (Oct. 1985).

D. Nyyssonen, "Focused-Beam vs. Conventional Bright-Field Scanning Microscopy

for Integrated Circuit Metrology," Micron and Submicron IC Metrology. Proc.

SPIE 565. pp. 102-107 (1985).

D. Nyyssonen and M.T. Postek, "SEM-Based System for Calibration of Linewidth

SRMs for the IC Industry," Micron and Submicron IC Metrology, Proc. SPIE 565 . pp. 180-186 (1985).

R. L. Parker, J.R. Manning and N.C. Peterson, "Application of Pulse -Echo

Ultrasonics to Locate the Solid/Liquid Interface During Solidification and

Melting of Steel and Other Metals," J. Appl. Phvs . 58 . No. 11, pp . 4150-4164

(1985).

H.J. Prask and C.S. Choi, "Sub-Surface Residual Stress Measurements by Means

of Neutron Diffraction: Aluminum, Steel and Depleted Uranium," Materials

Characterization for Systems Performence and Reliability . J.W. McCauley and

V. Weiss, eds., pp . 535-546 (Plenum, 1986).

C. Presser, A.K. Gupta, R.J. Santoro and H.G. Semerjian, "Velocity and Droplet

Size Measurements in a Fuel Spray," AIAA Paper 86-0297 (Jan. 1986).

S. I. Rokhlin, K. Lewis, K.F. Graff and Laszlo Adler, "Application of Spectral

Analysis Technique for the Study of Curing Reactions in Epoxy Resins," Review

of Progress in Quantitative Nondestructive Evaluation 5B . pp . 1047-1053

(1986) .

R.E. Schramm and T.A. Siewert, "Sizing Planar Flaws in Weldments Using LowFrequency EMATs , " Review of Progress in Quantitative Nondestructive Evaluation

5B , pp. 1705-1712 (1986).

R.E. Schramm and T.A. Siewert, "Production and Sizing of Uniform TwoDimensional Flaws in Welds for NDE Calibration, Materials Evaluation 44,

pp. 1136-1138 (Aug. 1986).

J.A. Simmons, "Deconvolution for Acoustic Emission," Review of Progress in

Quantitative Nondestructive Evaluation 5A . pp. 727-735 (1986).

L.J. Swartzendruber , "Magnetic Nondestructive Evaluation," Encyclopedia of

Materials Science and Engineering , pp . 2694-2698 (Pergamon, 1986).

E. C. Teague, T.V. Vorburger and G. Birnbaum, "Optical Nondestructive

Evaluation," Encyclopedia of Materials Science and Engineering , pp . 3312-3316

(Pergamon, 1986) .

63
T.V. Vorburger, D.E. Gilsinn, F.E. Scire, M.J. McLay, C.H.W. Giauque and

E.C. Teague, "Optical Measurement of the Roughness of Sinusoidal Surfaces,"

Wear 109 (1986) .

T.V. Vorburger, M.J. McLay, F.E. Scire, D.E. Gilsinn, C.H.W. Giauque and E.C.

Teague, "Surface Roughness Studies for Wind Tunnel Models Used in High

Reynolds Number Testing," J . Aircraft 23 . p. 56 (1986).

H.N.G. Wadley, "Acoustic Emission: Nature's Ultrasound," Review of Progress

in Quantitative Nondestructive Evaluation 5 A . pp . 271-293 (1986).

V.R. Weidner, R. Mavrodineanu and K.L. Eckerle, "Sintered Mixtures of

Phosphors in Polytetrafluorethylene Resin for Fluorescence Standards," Applied

Optics 25, No. 6, p. 832-833 (1986).

H.T. Yolken and R. Mehrabian, eds . , "A National Forum on The Future of

Automated Materials Processing in U.S. Industry -- The Role of Sensors," NBSIR

86-3341, 76 pp . (May 1986).

M. Young, "The Scratch Standard is Only a Cosmetic Standard," Laser

Focus /Electro -Op tics . pp . 138-140 (Nov. 1985).

D. AWARDS AND APPOINTMENTS

Department of Commerce Bronze Medals

The Bronze Medal Award is the highest honorary recognition available for

Bureau presentation. Recipients during FY 1986 included Dr. Norman F. Berk of

the Reactor Radiation Division and Dr. Kay A. Hardman -Rhyne of the Ceramics

Division, who collaborated in the theoretical and experimental development of

small-angle neutron scattering (SANS) as a reference measurement technique' for

nondestructive evaluation. Another recipient was Dr. Richard J, Fields of th< Fracture and Deformation Division, who used the SANS technique to characte i i : <• low levels of distributed creep damage in metal specimens that had been

exposed to elevated temperatures for extended periods while under load.

Dr. Ronald F. Fleming of the Center for Analytical Chemistry was similarly

honored for his significant contributions to the establishment of neutron

depth profiling, another new materials characterization technique.

William Blum Award

This prestigious award of The Electrochemical Society was presented :

Dr. Ugo Bertocci of the Metallurgy Division for his research into the

relationship between electrochemical noise and electrode processes, notably

the initiation of pitting corrosion in metals.

64
Wason Medal

Dr. Nicholas J. Carino of the Center for Building Technology was awarded the

Wason Medal for Materials Research by the American Concrete Institute in

recognition of his significant contributions to the nondestructive testing of

concrete and, particularly, the development of a pulse -echo technique for

detecting flaws within concrete structures.

ASME Fellow

Dr. Jeffrey T. Fong of the Center for Applied Mathematics was elected a Fellow

of the American Society of Mechanical Engineers. Dr. Fong, who recently

edited a volume on NDE Reliability through Round-Robin Testing, was also named

the new chairman of the 14 , 000 -member ASME Pressure Vessel and Piping

Division.

ASM Fellow

Dr. John R. Manning . Metallurgy Division, was named a Fellow of the American

Society for Metals. Manning heads the Metallurgical Processing Group at NBS

and is responsible for administering a major segment of the NDE Program's

activity on rapidly solidified metal powder processing.

Dr. Lorretta J. Inglehart . a contract scientist in the Ceramics Division, was awarded a Fulbright Scholarship for study and lecturing in France.

Dr. Gerald V. Blessing of the Center for Manufacturing Engineering was named

international program chairman for the November 1986 meeting of the Institute

for Electrical and Electronics Engineers.

Dr, Donald G, Eitzen of the Center for Manufacturing Engineering was elected

the new chairman of the subcommittee on acoustic NDT methods (TC 135/SC 3) in

the International Organization for Standardization.

Dr. Theodore V, Vorburger of the Center for Manufacturing Engineering was elected chairman of Committee B46 on Classification and Designation of Surface

Qualities in the American Society of Mechanical Engineers. During March 1986,

Dr. Vorburger surved as a specialist for the World Bank Chinese University

Development Project, lecturing and consulting at Chongquing University on optical inspection methods.

Dr, Klaus D. Mielenz of the Center for Radiation Research was appointed

director of Division 2 on Physical Measurement of Light and Radiation in the

International Commission on Illumination.

Dr , Jack J . Hsia of the Center for Radiation Research was elected to the board

of directors of the Inter- Society Color Council.

65
E. PRINCIPAL INVESTIGATORS

Berk, Norman F. Small-angle neutron scattering

Condensed matter theory

Berlinsky, Yoram Acoustic emission

Wave propagation and instrumentation

Biancaniello, Francis S. Metals processing

Blessing, Gerald V. Ultrasonics

Experimental physical acoustics

Breckenridge, Franklin R. Acoustic emission and transducers

Transducer calibration

Capobianco, Thomas E. Eddy current NDE

Electromagnetic technology

Clark, Alfred V. Ultrasonics and eddy currents

Mechanical properties

Clough, Roger B. Acoustic emission

Mechanical Properties

Cohen, Julius Thermography

Fourier optics

Droney, Bernard Steel processing sensors Metallurgy

Eckerle, Kenneth L. Fluorescence

Spectrophotometry

Ehrlich, Charles D. Calibrated leaks and leak detection

Surface physics

Eitzen, Donald G. Acoustic emission

Engineering mechanics

Fanconi, Bruno M. Optical wave guide techniques

Polymer science

Fick, Steven E. Specialized measurement

Electrical Engineering

Fickett, Frederick R. Electromagnetic methods

Solid state physics, superconductivity,

and magnetism

Gaigalas, Adolfas K. Chemical process metrology

Sensors

66
Gilsinn, David E. Surface Metrology

Hardman-Rhyne, Kay A. Small-angle neutron scattering

Ceramics

Hsia, Jack J. Spectrophotometry

Spectrophotometry and thermal radiation

properties

Hsu, Nelson N. Acoustic emission and ultrasonics

Experimental solid mechanics

Huns ton, Donald L. Ultrasonics

Polymer science

Inglehart, Lorretta Thermal waves

Physics

Jones, Martin P. Ultrasonics

Materials

Kahn, Arnold H. Eddy currents

Solid state physics

Krasicka, Eva Ultrasonics

Physics

LaSalle, E.H. Legal Thermal Waves

Physics

Ledbetter, Hassel M. Elastic properties and internal friction

Physcial properties of solids

Linzer, Melvin Ultrasound instrumentation

Signal processing

Lowry, Robert E. Polymer characterization

Dielectrics

Mattingly, George E. Fluid Diagnostics

Fluid Dynamics

Mauer, Floyd D. Ultrasonic temperature sensing

Ultrasonic measurement

Mielenz, Klaus D. Flourescence

Optical instrumentation and optics

Mopsik, Frederick I. Electrical measurements

Dielectrics

Moulder, John C. Eddy current; ultrasonics using EMATS

Materials Research

67
Mountain, Raymond Acoustic scattering

Statistical physics

Norton, Stephen J. Ultrasonic imaging

Inverse modeling

Nguyen, Tinh Thermal wave imaging and infrared thermography

Corrosion under coatings

Placious, Robert C. Radiological imaging

Radiation physics

Prask, Henry J. Neutron diffraction

Residual stress

Proctor, Thomas M. Acoustic emission, transducers

Transducer calibrations and design

Ridder, Steven D. Metals processing

Metallurgy

Robbins, Carl R. Ceramic powder preparation and

characterization

X-ray diffraction

Semerjian, Hratch G. Particle sizing

Laser Light Scattering

Shull, Peter J. Eddy currents

Simmons, John A. Defects and elastic propagation; materials

characterization

Applied mathematics and theoretical mechanics

Swartzendruber , Lydon A. Surface methods

Physical metallurgy

Teague, E. Clayton Non-contacting optical measurements of surface

roughness

Surface metrology and physics

Tilford, Charles R. Leak and pressure standards

Vacuum technology

Vorburger, Theodore V. Optical scattering techniques

Surface roughness measurement

Wadley, Haydn N. G. Acoustic emission

Fracture and deformation

Wang, Francis W. Fluorescence spectroscopy

Polymer characterization

White, Grady S. Thermal waves Mechanical properties of brittle materials

68
NBS-114A irev. 2.80

3. Publication Date

JANUARY 1987

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

86-3434

2. Performing Organ. Report No.

4. TITLE AND SUBTITLE

Office of Nondestructive Evaluation, Technical Activities, 1986

5

- OBS®. Yolken

6. PERFORMING ORGANIZATION (If joint or other than NBS. see instructions)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8 . Type of Report & Period Covered

9.

SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. Stote, ZIP)

National Bureau of Standards

Rt. 270 & Quince Orchard Road

Gaithersburg, Maryland 20899

10.

SUPPLEMENTARY NOTES

3) Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bi bliography or literature survey, mention it here)

A review of the Nondestructive Evaluation Program at NBS, for fiscal year 1986, is

presented in this annual report.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) acoustic emission; eddy currents; leak testing; magnetics; neutrons; nondestructive

evaluation; optics; penetrants; radiography; standards; thermal testing; ultrasonics

13. AVAILABILITY

C] Unlimited

| | For Official Distribution. Do Not Release to NTIS

| Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

[X] Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

77

15. Price

$13.95

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