bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlation Between Corrosion Behavior of Steel and Atmospheric Pollution Data
Authors: Haynie FH , Upham JB
Published: March 2009

Specimens of an enameling steel were exposed at 57 sites of the National Air Sampling Network (NASN). Weight losses for one and two years of exposure at each site were determined. Available climatic data were collected and average relative humidities and average temperatures were calculated. Average levels of pollutants were determined from collected NASN data. The pollutants of interest were gaseous sulfur dioxide, total suspended particulate, sulfate in suspended particulate, and nitrate in suspended particulate.

Multiple linear regression and nonlinear curve fitting techniques were used to analyze the relationship between corrosion behavior of this steel and the collected atmospheric data. The resulting best empirical function has the form: cor=a0te[a1sula2/RH]where cor = depth of corrosion, μm t = time, years sul = average level of sulfate in suspended particulate (μg/m3) or average level of sulfur dioxide (μg/m3) RH = average relative humidity According to statistical analysis, differences in average temperature, average total suspended particulate, and average nitrate in suspended particulate caused insignificant changes in this steel's corrosion behavior. Sulfur dioxide was a significant variable only when sulfate in suspended particulate was not included in the regression analysis. The levels of these two pollutants generally change together from site to site (exhibit a high degree of covariance). Therefore, sulfate in suspended particulate may be a substitute variable for sulfur dioxide.
Seven-Year Exposure at Point Reyes, California
Authors: Ailor WH
Published: March 2009

This report is concerned with the data obtained from the seven-year Point Reyes, California removals (second exposure). These exposed panels included 39 alloys of eight basis metals of the 1957 program.

Previous reports concerning this program may be found in the Committee B-3 reports in the ASTM Proceedings for 1959, 1961, and 1962 and in the Committee G-l report (1966 Proceedings).

A number of test panels were lost due to the work of vandals at the Point Reyes test site during the fall of 1962. A fence subsequently erected should protect panels still exposed for future years. Replacements for seven- and twenty-year panels for most alloys were exposed on 12 June 1964. The seven-year panels were removed by task group member T. J. Summerson on 6 June 1971 after a total of 2550 exposure days. The twenty-year test panels remain on the racks for subsequent removal.
Short-Term Atmospheric Corrosion of Various Copper-Base Alloys—Two- and Four-Year Results
Authors: Herman RS , Castillo AP
Published: March 2009

Corrosion data pertaining to a variety of copper-base alloys after two- and four-year exposure to natural environments at New Haven, Connecticut, Brooklyn, New York, and Daytona Beach, Florida are presented. High zinc alloys, cartridge brass alloy B36 (260) and nickel silver alloy B122 (770) experienced substantial decreases in mechanical properties due to “plug type” dezincification and pitting. In addition, the rate of attack on high zinc containing alloys was environment specific. Alloy (619), a copper-aluminum-iron alloy, displayed substantial increases in mechanical properties with time. This is attributed to a long-term low-temperature order-disorder mechanism. The degree of patination was alloy, time, and environment specific. To avoid ambiguity, it is suggested that instantaneous corrosion rate rather than changes in absolute weight loss be used as the criterion for duration of atmospheric testing of copper-base alloys.
Electrochemical Technique for Determination of the Instantaneous Rate of Atmospheric Corrosion
Authors: Kučera V , Mattsson E
Published: March 2009

The aim of this investigation was to develop a technique and equipment for the measurement of the instantaneous rate of atmospheric corrosion of metals. An electrochemical method was chosen for this purpose and a technique was developed for continuous measurement and recording of the currents generated in models of the electrochemical corrosion cells which occur on the metal surface when exposed to the atmosphere. Two types of cells were used, galvanic cells consisting of steel and copper electrodes and electrolytic cells consisting of only one type of electrode, namely, steel, zinc or copper. In the latter type of cell an external emf was applied. The cell current was found to vary between 10-10 and 10-3 A in accordance with changes in climatic conditions, the changes being at least in qualitative agreement with changes in the rate of atmospheric corrosion as earlier reported in the literature. An inexpensive electronic integrator was developed for estimation of the accumulated quantity of cell current over a certain period of time. This device integrates separately on two counters the amount of current during periods with low current and during periods with high current. A time counter also records the exposure time during which the current exceeds a chosen value. This time counter can be used to measure the time of surface wetness, that is, that part of the period of exposure when the corrosion current is of practical importance. Efforts are now being made to find the quantitative relation between the cell current and the atmospheric corrosion rate. It is believed that the technique will prove to be a useful tool for the investigation of atmospheric corrosion in the laboratory as well as on test sites out of doors and in industrial applications.
Accelerated Testing of Marine Grade Steels—A Localized Corrosion Approach
Authors: Johnston RRM , Lloyd CP
Published: March 2009

Factors affecting local cell action such as the presence of non-metallic inclusions in steel and the contribution of ohmic control (iR drop) in the electrolyte are discussed. The importance of local action in the marine environment and the poor reliability of current accelerated tests for marine grade steels are pointed out. An investigative technique, developed from earlier work, is described in which the specimen has been incorporated in the form of a horizontal rotating disk enabling solution hydrodynamics to be readily defined. The intensity of local cells is displayed in real time as a magnified contour map of the corroding specimen surface. Effects of test electrolyte composition including ionic strength and concentration of cathodic species have been studied on a model galvanic system, a steel containing sulphide inclusions, and two low-alloy marine grade steels.
Design of a Laboratory Experiment to Identify the Effects of Environmental Pollutants on Materials
Authors: Spence JW , Haynie FH
Published: March 2009

This paper describes an environmental system consisting of five exposure chambers and an experimental design for studying the effects of gaseous air pollutants [sulfur dioxide (S02), nitrogen dioxide (N02), and ozone (03)] on materials. Each chamber has the means for independent control of six environmental variables (temperature, relative humidity, etc.) as well as the unique feature of chill racks that regulate the formation of dew on the test specimens. An accelerated test is achieved by a dew-light (xenon lamp) cycle to simulate diurnal conditions. Statistical techniques (analysis of variance) were used to correct for differences in light and pollutant distribution within the chambers before initiating a statistically designed environmental experiment. To study the interactions of pollutants and other environmental variables that are likely to have significant effects on materials, a two-level factorial arrangement was selected.
Prediction of Environmental Pitting and Corrosion Rates
Authors: Shuler RN , Ailor WH
Published: March 2009

For nearly 15 years the environmental test results from long-term exposures have been handled by a computer program. Over 1 14-million bits of information representing data from more than 250 metals and alloys on test at fifteen atmospheric and two seawater locations are included in the program. Calculations are made reflecting aging changes, and changes due to the cleaning procedure and to corrosion. A printout then gives corrosion rates and mechanical property changes for each time period. Data points include 1,2,7, and 20 years for atmospheric specimens and 1, 2, 5, 10, and 20 years for seawater tests. Exposures of new alloys are made each year as phases of the continuing program along with appropriate removals of exposures from earlier series.

Since at least three data points are now on hand from some test metals, it is feasible to predict both corrosion rates and extreme pitting values for future removals. The corrosion rates and pitting data are subjected to curve fitting techniques through a computer operation. Several models were considered. However, based on earlier published studies on aluminum, we decided to begin with a least-squares fit of the cube-root pitting equation, d = kt1/3. Future work with other models may indicate improved reliability.

It is now possible to predict the 20-year corrosion rate for a marine environment and to estimate the time to perforation for a given alloy system. Actual 20-year data, when available, will be compared with these predicted values. Also included in the program is the capability to predict 10-year results when shorter-term data (1,2, and 5 years) are on hand.
Statistical Characteristics of Fatigue Damage Accumulation in Flexible Pavements
Authors: Soussou JE , Moavenzadeh F
Published: March 2009

A closed form probabilistic formulation is presented for the determination of the fatigue deterioration of flexible pavements. This formulation is based on the simple phenomenological models which use Miner's law. The expected value and variances of the measure of damage are related to the statistical characteristics of the loading patterns and materials properties. A spatial coefficient of correlation is determined for the measure of damage and is used to determine the typical size of the cracked areas. This study emphasizes the need for obtaining more complete material characterization procedures which do include measurements for spatial variabilities.
Influence of Laboratory Test Method on Fatigue Test Results for Asphaltic Concrete
Authors: Irwin LH , Gallaway BM
Published: March 2009

Fatigue characterizations obtained using three laboratory repeated-load, flexure test methods were compared. The test methods included uniaxial stress fields (beam specimens), biaxial stress fields (plate specimens), full stress reversal, and no stress reversal. In addition, specimens were sawn from field-compacted asphaltic concrete, and test results were compared with those from laboratory prepared specimens.

The degree of stress reversal and possibly the type of stress field to which the specimens were subjected were found to influence the resultant slope and intercept of the fatigue curve. The results of a comparison of fatigue characterizations obtained with laboratory and field-compacted specimens were not clear due to differences in the air void contents of the two mixtures.

An analysis to determine the minimum number of specimens required for fatigue characteristics using the beam test method suggested (but did not prove) that approximately ten specimens having 3 in. (76 mm) widths and depths should be used.
Dynamic Testing of Bituminous Mixtures for Permanent Deformation Response
Authors: Morris J , Haas RCG
Published: March 2009

Permanent deformation, fatigue, and shrinkage fracture are the three major distress mechanisms found in flexible pavements. To date, however, little quantitative information is available on the fundamental material characteristics related to load-associated permanent deformation. The response and characterization of paving materials have proven to be complex problems. This situation has retarded the development of a reliable deformation predictive technique and, consequently, a systematic pavement design process.

This paper briefly discusses available permanent deformation predictive approaches. It is indicated that current techniques are inadequate in their present form. A new approach based upon laboratory tests under simulated field conditions is advanced, and the essential operating characteristics of associated materials characterization test equipment are outlined. The apparatus, which includes a temperature-controlled triaxial test chamber, electrohydraulic systems for independent control of axial and lateral dynamic stresses, and ancilliary measuring instruments is described.

The equipment can be used to evaluate a wide variety of conditions and paving materials. The test results have been used as input data to the development of statistically based models for predicting the permanent deformation of full-depth sections at the Brampton Test Road, Ontario. Excellent agreement between measured and predicted values have been obtained.
Load-Point Compliance of the Charpy Impact Specimen
Authors: Saxton HJ , Jones AT , West AJ , Mamaros TC
Published: March 2009

To evaluate the instrumented impact test as a reliable way of collecting high strain rate, plane strain fracture toughness data, a detailed investigation of specimen mechanical performance and specimen-fixture interaction was undertaken. Finite element techniques were applied to calculate the compliance and stress intensity values for Charpy specimens subjected to both roller and pinned supporting conditions. For comparison, experimental compliances were gathered for 7075-T6 aluminum and 1018 steel Charpy specimens tested in slow and fast bending. The results indicate that both small specimen size and anvil friction can affect the interpretation of fracture load data used for KID calculations.
Dynamic Fracture Toughness Measurements of High-Strength Steels Using Precracked Charpy Specimens
Authors: Koppenaal TJ
Published: March 2009

The dynamic fracture toughness, KId, was measured in a number of ferrous alloys using precracked Charpy specimens and an instrumented impact machine. The alloys investigated included quenched and tempered steels (H-11, D6AC, and 4340), 18Ni maraging steels (grades 200, 250, and 300) and a high-temperature, stainless maraging steel (Pyromet X-15). Standard Charpy specimens were precracked in fatigue and tested at either 72°F (22°C) or -65°F (-54°C). Values of KId, were determined as a function of yield strength and microstructure, and correlations were established between KId and both the energy to initiate fracture, Wm/A, and the total energy of fracture, W/A. The instrumented, precracked Charpy test is shown to be a convenient method of determining relative fracture toughness; under proper conditions this test procedure can be used to determine the dynamic planestrain fracture toughness.
Impact Properties of Shock-Strengthened Type 316 Stainless Steel
Authors: Sheckherd JW , Kangilaski M , Bauer AA
Published: March 2009

The effect of shock strengthening on impact properties of Type 316 stainless steel at temperatures ranging from room temperature to 650°C (1202°F) was established by utilizing the instrumented Charpy impact test. It was found that the total impact energy absorbed progressively decreases with increasing shocking pressure.

The dynamic yield strength (σdy) was increased by increasing the shocking pressures for all testing temperatures. This trend is expected because the static yield strength (σsy) was also found to increase with increasing shocking pressure. However, the ratio of dynamic-yield to static-yield strengths (measure of strain-rate sensitivity) was found to decrease with increasing shocking pressure.
Instrumented Charpy Testing for Determination of the J-Integral
Authors: Iyer KR , Miclot RB
Published: March 2009

Rice's path-independent integral J of medium-strength alloys was determined under dynamic conditions by instrumented impact testing of precracked Charpy specimens. The viability of the instrumented Charpy technique for rapid and easy determination of useful fracture parameters is explained. Standard and side-notched Charpy specimens of Cr-Mo-V, H-11, and CG-27 alloys were precracked and tested. Load-displacement curves were generated for specimens with different fatigue precrack lengths. The energy for initiation of fracture in each case was determined by measuring the area under the load-displacement curve up to limit load. The value J at the onset of crack propagation, JID, was calculated from a plot of energy versus crack length. The value of JID is not affected by side notches. The slope of the energy versus crack length plot alters sufficiently to compensate for the reduction in thickness. Agreement is good between KID values calculated from JID measurements and by other methods.
A Compilation and Historical Review of Temperature Scale Differences
Authors: Hust JG
Published: March 2009

A brief review given of temperature scales, their definition, and measurement. Methods of practical temperature measurement are described. Differences between internationally accepted temperature scales are presented graphically and in tabular form; comparisons are also given for several national temperature scales. Emphasis has been placed on temperatures below 0°C, but some information on temperatures above 0°C has also been included. Suggested methods of conversion between different temperature scales are described.
Corrosion, Wear, and Erosion—An Ancient Art and a Modern Science
Authors: Kallas DH
Published: March 2009

A thorough historical review of corrosion, erosion, and wear is given along with a study of the state of the art with a view to how the interdisciplining approach is attempting to unify opinions on the mechanism of damage. This is followed by some thoughts on areas for future research and development. The paper concludes by speculating on how the knowledge gained can impact on our material resources, the environment, and the quality of life.
Erosion-Corrosion of Finned Heat Exchanger Tubes
Authors: Van der Horst JMA , Sloan CR
Published: March 2009

Converted reformer gas on the shell side of a heat exchanger was cooled by water on the tube side. In addition to hydrogen and nitrogen, the gas contained substantial quantities of CO2 and water vapor. The tubes were integral finned of C-steel. Condensate from the gas stream filled the space between fins, while CO2 from the stream dissolved into the water. Maximum gas velocity was of the order of 150 ft/s.

In the areas of highest gas velocity the fins had disappeared completely. In more or less stagnant gas areas the fins were corroded but still present, attack in intermediate areas ranging between the two extremes. The difference in corrosive attack between various areas clearly demonstrates the relatively modest effect of pure corrosion under these circumstances. On the other hand, the maximum velocity is about half the threshold velocity cited in the literature for steel. The synergistic effect of corrosion and erosion is therefore unmistakable. It may be assumed that impact of water droplets continuously removes the corrosion layer and thus accelerates the process.

The corrosive effect of CO2 at ambient temperatures is often belittled, but should not be, especially when assisted by high-velocity gas.

Incidentally, the use of finned tubing in an environment producing condensate is absurd since condensation removes any heat-transfer advantage of the fins. Recalculation in fact showed that the fins were unnecessary.
Effects of Cavitation on Materials in Field and Laboratory Conditions
Authors: Steller K , Krzysztofowicz T , Reymann Z
Published: March 2009

The behavior of certain materials exposed to cavitation, in field as well as laboratory conditions, was observed. The investigations were aimed at uncovering differences as well as singularities occurring in cavitation damage processes and determining the efficiency of comparing “cavitational resistance” of material on the basis of testing specimens under various conditions. Observations of specimen surfaces geometric structure were made together with measurements of the specimen destruction rate, microscopic observations of upper layers of material surface, and hardness measurements.
Liquid Impact Behavior of Various Nonmetallic Materials
Authors: Hammitt FG , Timm EE , Hwang JB , Huang YC
Published: March 2009

Detailed photographs of liquid jet impact against elastomeric surfaces are presented and compared with impact and also cavitation erosion resistance. Two correlations between erosion resistance and material properties are presented.
Erosion of Fused Silica by Glass Beads
Authors: Adler WF
Published: March 2009

An analytical approach to particle erosion of brittle material surfaces is being developed based on a statistical model of erosion pit nucleation and growth[1,2]. For solid-particle erosion the Hertzian theory of impact is being considered in order to introduce the kinematic and material parameters into the general statistical formulation of the erosion process. In order to minimize the number of unknown factors in the initial development of a predictive erosion theory, the particular case of spherical glass beads impacting directly on the plane surface of relatively flaw-free fused silica (Corning 7940) has been investigated.

The erosion mechanisms in fused silica have been identified for both 70- and 290-μm glass beads impacting at 61 and 91.5 m/s. The experimentally observed erosion mechanisms could be correlated with the measured erosion rates, and it was substantiated that the solid-particle erosion of fused silica could be modeled in terms of preferential pit nucleation and growth. The controlled erosion tests provided evidence for the applicability of the Hertzian relations to the impact conditions associated with solid-particle erosion.
Why Acoustic Emission—Why Not?
Authors: Schofield BH
Published: March 2009

The relative apathy of the industrial community to take advantage of the significant benefits of acoustic emission is discussed against the background of the current state of the technology. Examples of immediate applications are noted. It is suggested that developing trends necessitate timely initiation of industrial utilization and that such efforts and the experience gained therein are a prerequisite to the realization of the technical benefits of acoustic emission and the establishment of proper and adequate guidelines.
Development of Acoustic Emission Testing for the Inspection of Gas Distribution Pipelines
Authors: McElroy JW
Published: March 2009

This paper describes how a utility became interested in acoustic emission testing for the survey inspection of its buried gas pipelines. Several weld failures emphasized the need to develop inspection techniques to monitor these pipelines in order to locate weld flaws in high-stress regions to permit prompt weld repairs and assure system integrity. It was found that a weld must have a certain metallurgical flaw and must be located in a high-stress region in order to precipitate an inservice oxyacetylene weld failure in a pipeline. It was found that metallurgical flaws in high-stress regions can be located by acoustic emission tests.

This paper describes the field development of the acoustic emission testing technique and the correlation of the field results with the laboratory results. It was found that the stress levels imposed by either internal pressurization or by external loading in the field tests are sufficient to cause critical flaws to emit and be located. Then replacement or reparation of the critical flaws located in this manner would restore the integrity of the pipeline. Discussed in the paper are the other nondestructive correlations such as radiography and correlations through tension tests, hydrostatic tests, bend tests, and fatigue tests.
Detection and Location of Flaw Growth in Metallic and Composite Structures
Authors: Kelly MP , Harris DO , Pollock AA
Published: March 2009

The application of a multichannel real-time acoustic emission location system to the detection and location of structural defects in three different materials and geometries is presented. Test results from welded steel pressure vessels demonstrate that incremental crack growth during pressurization can be accurately located and assessed. Additional results from graphite-epoxy honeycomb structures indicate that acoustic emission is also a viable tool in detecting and locating impending failure in composite materials.
Acoustic Emission—A Bibliography for 1970–1972
Authors: Drouillard TF
Published: March 2009

The bibliography includes nearly all references in the literature on acoustic emission published during the three-year period, 1970 through 1972. Included in the 412 references are several for each of the associated technologies including: signature analysis, boiling detection, cavitation, leak detection, seismology, and rock mechanics. Information has also been obtained from eight abstracting and indexing services searched in compiling the bibliography. The bibliography has been arranged alphabetically by author and is cross referenced with a list of approximately 400 authors. Also included is a subject index. Technical articles listed were published in some 90 different journals and in 8 different languages.
A Decision Whose Time Has Come
Authors: Ancker-Johnson B
Published: March 2009

The United States is well along the road to becoming predominantly metric. The primary initiative in this movement comes from our industry, with current coordination in that sector by the American National Metric Council. The time has come for a well-planned, nationally-coordinated metrication program covering all sectors of our society.
The International System of Units (SI)
Authors: Graham JD
Published: March 2009

The world's dependence upon measurement is an old story in which a new chapter is being written by the introduction of SI, The International System of Units. The United States is now changing to this system.

The system is given in detail and its unique characteristics described. The units outside the system that will continue to be used are discussed. Style and manner of applying the units are detailed.

A brief discussion of the problem of converting from one system of units to another is included. Difficulties of using SI and possible remedies are also covered.
The Canadian Picture: Managing the Conversion of Standards in Canada
Authors: Spencer GH
Published: March 2009

This paper relates the Canadian experience in the establishment, through the Standards Council of Canada, of arrangements to provide standards expressed in SI on a nationally coordinated basis. Against a background of the general situation in Canada with respect to metric conversion, it describes the integration of the activities of the organizations concerned and delineates responsibilities for the conversion of standards. It provides a list of factors which influence a program for the conversion of standards and outlines a series of steps from first consideration through to the availability of standards expressed in SI. It contains an interim progress report which indicates that action toward conversion is still in an early stage; nevertheless, experience to date does highlight some observations of general application. A message in the conclusion begs for close attention.
Metrication in the Contract Tooling and Machining Industry
Authors: Darrone DW
Published: March 2009

The contract tool, die, and precision machining industry faces unique problems in the area of metrication due to its role as a supplier industry.

Although little work to metric specifications is presently being done, and a significant level of awareness exists in the industry regarding the trend toward metrication, only a very small segment of the industry has any definite plans for handling the transition.
Metrication at Vauxhall Motors Limited England
Authors: King AF
Published: March 2009

Metrication is being progressively introduced at Vauxhall Motors Limited generally in line with the recommendations of the Metrication Board set up by the British Government, and the Society of Motor Manufacturers and Traders. A Coordination Committee was given responsibility to consider all aspects and implications of the change, to determine the approach to be taken, and to allocate priorities.

Application to all new products became effective with the commencement of the 1972 model year, and non-product changes are programmed annually in accordance with internal needs and external progress.

Special attention has been given to color identification of fasteners and to the provision of personal tools and measuring instruments. The current status reported by each and every operating department within the company illustrates the wide ranging implication of this fundamental change.
Metric Conversion at General Motors Corporation
Authors: Streichert EJ
Published: March 2009

This paper attempts to describe how a large international manufacturing complex arrived at the decision to convert operations to the metric system with the subsequent issuance of general guidelines from management.

The implementations of metrication from these general guidelines is further explained with a discourse of the metric organizational structure, including channels of communication, rate of conversion, standardization procedures, and personnel training modules. Also included is a typical example of the type of investigation required to derive an internal metric interim standard.
New Method of Microscopic Inclusions Ratings for Specialty Steels in West Germany
Authors: Barteld KGH
Published: March 2009

For the determination of the microscopic degree of cleanliness, many charts and evaluation methods are in use internationally.

A summary of the best elements from the established methods used by the experts in West Germany is described. A procedure is given to the metallographer that sufficiently describes the microscopic degree of cleanliness as to shape, frequency, and size of the inclusions. The result is suitable for a statistic evaluation with modern computers.
Several Rating Methods of Nonmetallic Inclusions in Bearing Steels in Japan
Authors: Koyanagi A , Kinoshi M
Published: March 2009

The history of rating methods of nonmetallic inclusions in Japan, the background behind the adoption of the Microscopic Testing Method for the Nonmetallic Inclusions in Steel (JIS-G-0555), and the details of this original method are discussed.

To determine the relationship between the cleanliness index values obtained by this method and those obtained by the ASTM Recommended Practice for Determining the Inclusion Content of Steel (E 45-63), Method A, and the U.S.S.R. Microscopic Testing Method for Nonmetallic Inclusions in Ball and Roller Bearing Steel (GOST-801-60), the inclusion ratings of some bearing steels are examined by these three methods at the same time, and the different cleanliness indexes obtained by each method are compared.
Nonmetallic Inclusion Rating and Fatigue Properties of Ball Bearing Steels
Authors: Rousseau D , Seraphin L , Tricot R
Published: March 2009

We have had the opportunity to apply the most widely used methods of inclusion rating; and, from our experience, it appears that all metallographic methods, including the use of the quantitative television microscope, give roughly equivalent results as far as heat to heat comparison is concerned.

In this respect, the ASTM Recommended Practice for Determining Inclusion Content in Steel (E 45-63), adopted by the French Bearing Steels Quality Standard (NF A 35-565), appears to be one of the simplest and most readily achievable. Nevertheless, the addition of more precise practical rules would be useful in order to improve laboratory to laboratory reproducibility.

From the point of view of service behavior, it should be emphasized that fatigue properties do not depend upon the overall cleanliness of the steel but, mainly, upon the chemical nature of each type of inclusions. The nondetrimental effect of sulfide inclusions is now widely accepted, but the case of oxide inclusions needs to be carefully considered.

The major problem is, therefore, to afford realistic values for the permissible limits of every type of nonmetallic inclusion.
Nonmetallic Inclusions and Rolling Contact Fatigue
Authors: Böhm K , Schlicht H , Zwirlein O , Eberhard R
Published: March 2009

Rolling contact fatigue tests were carried out on an angular contact ball bearing test rig at a low unit pressure (Po = 260 kp/mm2). The results show a sound “relative correlation” between the rolling contact fatigue and the content of nonmetallic inclusions. The theory and actual knowledge of the mechanism of contact fatigue infer that the effect of nonmetallic inclusions is influenced by other material properties, material stressing, and residual stress built up from rolling contact. Hence, a definite correlation between nonmetallic inclusions and the rolling contact fatigue cannot be existent. Nevertheless, it seems to be feasible to develop a simple technique for evaluating the nonmetallic inclusions based on the relative correlation.
Relevance of Steel Cleanness and Fatigue Tests to Bearing Performance
Authors: Johnson RF , Sewell JF , Robinson JL
Published: March 2009

A collaborative program of work undertaken in England to compare bearing steels by different types of fatigue tests and to relate the results to the cleanness of the steels as measured by the standard Jernkontoret (JK) method is described. Four bearing manufacturers, their tube maker, and three steelworks cooperated, and the results were generated by six laboratories.

Two casts of one percent carbon-chromium steel were selected by JK inclusion assessments as having widely different cleanness levels. One cast met the prevailing bearing steel standards while the other cast was very inferior to these standards. Randomized samples of tube and bar were supplied from these. These samples provided specimens for all six laboratories to perform fatigue tests using rigs of the Unisteel type and material for three bearing manufacturers to produce and test bearings of the type and under conditions used for normal approval purposes.

The results were reassuring in that all tests confirmed the order of quality indicated by the inclusion counts. In the rig tests agreement between laboratories was reasonable when the fatigue lives were compared on the basis of life distribution curves. Nevertheless, some anomalies occurred; and, in the case of the bearing tests, the match was even less complete. Up to the present time, emphasis has been placed largely upon inclusions as the cause of these anomalies as well as the scatter between the results of individual specimens; but, other quality aspects should perhaps be taken more into account in establishing the true causes.
Effect of Nonmetallic Inclusions on Rolling-Contact Fatigue Life in Bearing Steels
Authors: Kinoshi M , Koyanagi A
Published: March 2009

Rolling-contact fatigue life tests were studied to evaluate the effect of nonmetallic inclusions in bearing steels similar to AISI 52100.

Fatigue tests were conducted on a test machine that was composed of a round disk specimen substituted for the housing washer of a thrust ball bearing. The specimen was loaded at 455 and 500 kg/mm2 (4.46 × 109 and 4.90 × 109 N/m2) in maximum hertzian stress, lubricated with spindle oil, and operated at room temperature.

The results of the fatigue tests showed that alumina-type inclusions were very harmful to fatigue life, but sulfide inclusions not only had no influence but increased the fatigue life in air-melted and even vacuum-melted steels. In electro-slag remelting steel, increased fatigue life indicated the possibility of effects with the exception of nonmetallic inclusions.
Influence of Melting Practice and Hot Forming on Type and Amount of Nonmetallic Inclusions in Bearing Steels
Authors: Randak A , Stanz A , Vöge H
Published: March 2009

Using cleanliness-rating numbers (sum-total-index-numbers), evaluated according to Stahl-Eisen-Prüfblatt 1570-71, the influence of melting processes, deoxidation, and hot forming on the rating number is discussed.
Quantitative Correlation Between Magnetic Perturbation Signatures and Inclusions
Authors: Barton JR
Published: March 2009

A brief description of the magnetic perturbation method is presented. Quantitative results, based on extensive experimental data, are reviewed that establish a strong correlation between magnetic signatures and inclusions and, also, fatigue crack development cycles on rod-type specimens fabricated from AISI 4340 steel. The dominant influence of “near surface” inclusions on fatigue crack development resulting in subsequent specimen fracture is established. Quantitative correlations between magnetic perturbation signatures and inclusions disclosed by metallurgical sectioning of ball bearing inner races are also presented. Endurance testing results on bearings, including several with magnetic signatures indicating inclusions, are reviewed. The significance of overall results is discussed.
Some Approaches to Assessing Failure Probabilities of Redundant Structures
Authors: McCarthy JF , Orringer O
Published: March 2009

The growing acceptance of the concept of variability in the properties of structural materials (fracture toughness of metals, differences in composite fibers, etc.), along with the inherent randomness of loading due to nature, has caused the approach of analyzing structural systems using reliability techniques to become increasingly important. Classical reliability analysis is traced from basic probability theory to the development of fiber bundle theory with its resulting features and limitations. Recent applications of reliability analysis to “weak-link” structural systems are cited. Current research in the probabilistic treatment of physically redundant structures is then discussed with emphasis on the proper definition of convolution integral limits and the problems involved in the statistical modeling of real engineering components. Recent and anticipated trends in the application of reliability techniques to analyzing redundant structures are examined, including risk analyses of current Air Force aircraft and the “wearout” approach to life expectancy. Conclusions are drawn concerning the role that risk analysis could play in modern aerospace design and in establishing structural design criteria.
Statistical Analysis of Flaw Strength Spectra of High-Modulus Fibers
Authors: Phoenix SL
Published: March 2009

A new multistage tension testing procedure is developed that enables the statistical estimation of the flaw strength spectra of high-modulus fibers. The mathematical development of the procedure assumes the compound Poisson process model in distance to represent the probabilistic aspects of flaw occurrence along the fiber. The multistage procedure is applied to commercially available boron filaments, and the results are compared with those obtained on the same filaments using the conventional single-stage tension testing procedure with the Weibull distribution as the underlying model. The experimental results illustrate the dangers of fiber strength data extrapolation.
Evaluation of an Accelerated Characterization Technique for Reliability Assessment of Adhesive Joints
Authors: Berens AP , West BS
Published: March 2009

Adhesively bonded joints were failed statically and in fatigue to test the validity of a fatigue-life assessment model. The results of the tests were in agreement with both the assumptions and the predictions of the model. In particular, the failure mode was constant for all tests and the observed static strength and fatigue lives were adequately modeled by the Weibull family of distributions with constant, but different, shape parameters over the range of test conditions considered. The predicted relationship between the shape parameters as a function of an experimentally determined material property was observed. The predicted distribution of residual strength as a function of time in the fatigue environment was verified and agreement between prediction and observation for an accelerated fatigue test was obtained.
Reliability Aspects of a Composite Bolted Scarf Joint
Authors: Reed DL , Eisenmann JR
Published: March 2009

A wing splice representative of a next-generation transport aircraft requires an extended fatigue life and the capability of disassembly and reassembly. The design, fabrication, static test, and fatigue test of both tension and compression graphite-epoxy candidates for such a splice was the objective of the research program reported here. A single-scarf bolted joint was selected as the design concept.

Test specimens were designed and fabricated to represent an upper surface and a lower surface panel containing the splice. The load spectrum was a flight-by-flight random load history including ground-air-ground loads.

The results of the fatigue testing indicate that, for this type of joint, the inherent fatigue resistance of the laminate is reflected in the joint behavior, and consequently the rate of damage accumulation is very slow under realistic fatigue loadings.
Shear Property Measurements of Adhesives in Composite Material Bonded Joints
Authors: Renton WJ , Vinson JR
Published: March 2009

A test specimen has been designed and procedures developed for determining the effective shear modulus, shear proportional limit, and ultimate shear strength for adhesive materials used in bonded lap joints between adherends of either metals or composite materials. By utilizing adhesives in their joint geometry, effects of errors from using bulk property data are avoided. Surface interaction phenomena between adhesive and adherend, surface roughness effects, etc. are automatically included.

Test data to date are presented for adherends of 1002 S-glass uniply and angleply construction, and Hysol EA951 adhesive. Effects of adhesive thickness and joint length are also presented.
Measurement of Thermal and Mechanical Properties of Graphiteepoxy Composites for Precision Applications
Authors: Freund NP
Published: March 2009

Results are reported on an investigation to evaluate the usefulness of selected graphite-epoxy composite structures for applications requiring precision tolerancing and dimensional control. GY-70/X-904 laminate composites in the double symmetric design (0/ ± 45/90)2s were tested, as well as a honey-comb design having two singly symmetric GY-70/X-904 faceplates bonded to an aluminum core.

Measurements were made to evaluate the coefficient of thermal expansion and its directional variations at 0, 45, and 90 deg to the outermost fiber orientation. Additional measurements of the coefficient included variations normal to the surface. Nondestructive testing employing holography was conducted to determine microcreep behavior.

Optical processing methods were investigated and mirrors with three types of reflector surfaces were fabricated. Environmental testing, including thermal cycling, thermal stability, humidity/vacuum effects, and temporal stability, was done on mirrors representing the various processing methods.

Data, discussion of results, and recommendations for applicable areas are given for the specific material and design types tested.
Damage Analysis in Composite Materials
Authors: Rose JL , Shelton W
Published: March 2009

Two nondestructive evaluation test methods, radiography and ultrasonics, are examined for potential use in composite material characterization programs for composite structures subjected to either fatigue damage, foreign object damage, or environmental degradation. The principal goal of the work is to introduce semiquantitative test methods for measuring the size of damage zones and for defining the characteristic flaws within the zone with emphasis being placed on developing test techniques, test philosophies, and discussions on various signal processing procedures. Sample test results are presented along with a description of selected computer simulation signal processing studies.
Kinetics of Environmental Degradation in Graphite-Epoxy Laminates
Authors: Kaelble DH , Dynes PJ , Crane LW , Maus L
Published: March 2009

A detailed study of the kinetics of environmental degradation in graphite-epoxy composites show a close correlation between analytical predictions and experimentally observed changes in interlaminar shear and fracture energy response under high moisture exposure conditions. Unaged composite specimens exhibit high interlaminar shear strength λb ⩾ 850 kg/cm2 (12 000 psi) and relatively low fracture energy Wb/A ≅ 10 to 20 kg cm/cm2 (56 to 112 lb in./in.2). Exposure to 95 percent relative humidity or water immersion at 100°C (212°F) for times t ⩾ 200 h produces a 30 to 50 percent reduction in λb accompanied by a concurrent two to fivefold increase in Wb/A and acoustic energy absorption. These property changes are shown to be irreversible and directly related to cumulative moisture degradation of the fiber-matrix interfacial bond. The magnitudes of these property changes are consistent with surface energy analysis and micromechanics predictions.
Stress Rupture of Glass-Epoxy Composites: Environmental and Stress Effects
Authors: Wu EM , Ruhmann DC
Published: March 2009

This paper is concerned with the delayed fracture of composite materials under constant stress. The results of an investigation of the combined effect of an active environment (benzene) and stress on the survival life of an E-glass reinforced epoxy composite material are presented. Through the use of an appropriate failure criterion and representative median log-time to failure values, time-dependent failure surfaces were generated from data obtained when testing in (1) air and (2) benzene for the first quadrant of the stress space. These experimental results are used to extend the current kinetic theory of rate-dependent rupture to include both anisotropic and environmental effects.
Reliability of Composite Zero-Expansion Structures for Use in Orbital Environment
Authors: Berman LD
Published: March 2009

Composite sandwich structures, composed of graphite-epoxy face sheets on aluminum honeycomb core, were found to successfully withstand 15 000 thermal cycles between -250 and 150°F (-157 and 66°C) in vacuum. Although thermal cycling induced microcracking in the face sheets, laminate flexural and tensile properties were unaffected, and the only noticeable effect was on the coefficient of thermal expansion and flatwise tensile strength of the sandwich. In addition, exposure of the structure to 95 percent relative humidity resulted in a finite change in dimensions, but no effect on the coefficient of thermal expansion.

These environmental effects were determined on composite sandwich structures selected for isotropy, uniformity of mechanical properties at temperature extremes, and balanced thermal expansion characteristics in two perpendicular directions.
Temperature Dependence of the Complex Modulus for Fiber-Reinforced Materials
Authors: Heller RA , Thakker AB , Arthur CE
Published: March 2009

To examine the time-temperature dependence of fiber-reinforced composite materials, forced vibration experiments have been conducted. After suitable statistical smoothing techniques have been applied to the raw data, the complex moduli (storage and loss moduli) of boron-epoxy and graphite-epoxy have been determined for a wide range of temperatures and frequencies. The materials are shown to exhibit an Arrhenius type of behavior.
Reducing Variability in Composite Tensile-Strength Properties
Authors: Mills GJ , Brown GG , Waterman DR
Published: March 2009

Variability in composite tension-test values limits the application of advanced composite materials to structural design loads far below the capabilities inherent to the reinforcing fibers. Failure probabilities of boron and graphite filaments on the low-strength side of the skewed distribution contribute to composite fracture initiation early in the loading cycle. Dispersion in composite test values at these low levels imposes restrictions on allowable design values to conform to the minimum in the test data population. Prestressing the prepreg materials affects a fiber strength property improvement by prebreaking the filaments at the defect sources of low load failure. Increases in “B” design allowable levels for boron and graphite-epoxy material systems are shown to relate to reductions in fiber strength dispersions accompanied by increases in the average values. Projections of composite “B” allowables to 297 ksi are made for defect-free filaments.