Showing papers in "Journal of Testing and Evaluation in 1993"
TL;DR: In this article, the authors used two-dimensional plane strain finite element analyses to develop J and CTOD estimation strategies appropriate for application to both shallow and deep crack SE(B) specimens.
Abstract: Fracture toughness values determined using shallow cracked single edge notch bend. SE(B), specimens of structural thickness are useful for structural integrity assessments. However, testing standards have not yet incorporated formulas that permit evaluation of J and CTOD for shallow cracks from experimentally measured quantities (i.e., load, crack mouth opening displacement (CMOD), and load line displacement (LLD)). Results from two-dimensional plane strain finite element analyses are used to develop J and CTOD estimation strategies appropriate for application to both shallow and deep crack SE(B) specimens. Crack depth to specimen width (a/W) ratios between 0.05 and 0.70 are modeled using Ramberg-Osgood strain hardening exponents (n) between 4 and 50. The estimation formulas divide J and CTOD into small scale yielding (SSY) and large scale yielding (LSY) components. For each case, the SSY component is determined by the linear elastic stress intensity factor. Kf. The formulas differ in evaluation of the LSY component. The techniques considered include: estimating J or CTOD from plastic work based on load line displacement (Apl∣CMOD), from the area under a load versus plastic crack mouth opening displacement diagram (Apl∣CMOD), and from the plastic component of crack mouth opening displacement (CMODpl). Apl∣CMOD provides the most accurate J estimation possible. The finite element results for all conditions investigated fall within 9% of the following formula. J = K 2 ( 1 − v 2 ) F + η J − C B b A p l ∣ CMOD where η J − C = 3.785 − 3.101 a W + 2.018 ( a W ) 2 The insensitivity of ηJ−C to strain hardening permits J estimation for any material with equal accuracy. Further, estimating J from CMOD rather than LLD eliminates the need to measure LLD, thus simphfying the test procedure. Alternate estimates of J and CTOD from measured plastic areas have equivalent accuracy to this formula; however, the η coefficients in these equations depend on the strain hardening coefficient. CTOD estimates based on scalar proportionality of CTODlsy, and CMODpl, such as that used in ASTM E 1290, Test Method for Crack-Tip Opening Displacement (CTOD) Fracture Toughness Measurement, are highly inaccurate especially for materials with considerable strain hardening.
119 citations
TL;DR: In this article, the authors developed a new instrumented Charpy impact testing system, which is called CAI (Computer Aided instrumentedCharpy Impact testing) system, using the CAI system, dynamic fracture toughness parameters such as Kd, Jd, Tmat, and various absorbed energies can be obtained from the load-deflection curve of a single precracked specimen for both ductile and brittle materials.
Abstract: Instrumented Charpy impact test has been widely used as a simple method for semi-empirically evaluating material impact toughness. The authors have developed a new instrumented Charpy impact testing system, which is called CAI (Computer Aided instrumented Charpy Impact testing) system. Using the CAI system, dynamic fracture toughness parameters such as Kd, Jd, Tmat, and various absorbed energies can be obtained from the load-deflection curve of a single precracked specimen for both ductile and brittle materials. It has been already put into practical use in Japan. This paper introduces the details of the toughness evaluation procedures in the CAI system.
58 citations
TL;DR: In this paper, a double cantilever beam specimen is described, which is made of oriented strandbaard (OSB) and has a concave taper; two contoured beams sandwich a wood laminate having the test bondline at its center, which improves the accuracy and reproducibility of the test results with adhesively bonded wood joints.
Abstract: The strain energy release rate and associated param eters are useful measures of adhesive band quality. A properly con toured double cantilever beam specimen excels in measuring these properties. However, previous specimen designs presented experi mental difficulties resulting in possible bias and poor reproducibility. A new composite specimen is described that overcomes these prob lems. The specimen is made of oriented strandbaard (OSB) and has a concave taper; two contoured beams sandwich a wood laminate having the test bondline at its center. Unlike previous specimen de signs, this new specimen allows bonding of the test joint under normal conditions and produces a linear relationship between specimen com pliance and crack length. These changes improve the accuracy and reproducibility of the test results with adhesively bonded wood joints. This report describes how the new specimen was developed and how to experimentally determine the compliance and crack-length rela tionship used to calculate the strain energy release rate of an adhesive joint. Furthermore, the reproducibility of two sets of specimens and the use of the method to analyze differences in actual joint quality are shown and discussed.
30 citations
TL;DR: In this paper, a miniaturized disk-bend test (MDBT) has been successfully used to evaluate the mechanical properties of a variety of materials, using specimens 3 mm in diameter.
Abstract: A recently-developed miniaturized disk-bend test (MDBT) has been successfully used to evaluate the mechanical properties of a variety of materials, using specimens 3 mm in diameter. The load is applied either by a solid ball (the ball-on-ring (BOR) mode), or by a hollow cylinder (the ring-on-ring (ROR) mode). We have reproduced the yield stresses of ordered intermetallic compounds and the fracture toughnesses of several ceramics using analytical solutions to the equations of elasticity theory. Despite this success there are several curious features involved in the analysis of data, for example, in previous tests conducted in the BOR mode correct values of the yield stress were obtained using the equations appropriate to clamped specimens, whether or not they were actually clamped in the test fixture. We show that this is ubiquitous to tests in the BOR mode, and does not arise because of frictional constraints at the supporting ring. We have also completed a thorough evaluation of testing in the ROR mode, in which the yield stresses of cold-rolled or annealed AISI type 302 stainless steel were measured using various combinations of specimen thickness and radii of the loading and supporting rings, and compared to those of tensile specimens machined from the same material. The most accurate and reproducible measurements of the yield strength were obtained for specific combinations of specimen thickness and geometry of the apparatus. We describe these conditions and demonstrate that they provide values that are always within 10% of the tensile results. The errors induced by potential misalignments in the MDBT are also discussed, and are shown to cause no more than a 5% deviation in the measured yield stress.
30 citations
TL;DR: In this article, an analysis of the rolling contact fatigue process of case-hardened gear material by means of elasticity and fracture mechanics theory has been made; the stress intensity range [Delta]k and equation for crack growth da/dN = c(Delta)k was put forward to calculate their fatigue life and strength in this work.
Abstract: An analysis of the rolling contact fatigue process of case-hardened gear material by means of elasticity and fracture mechanics theory has been made; the stress intensity range [Delta]k and equation for crack growth da/dN = c([Delta]k) was put forward to calculate their fatigue life and strength in this work. The results show that the calculated data are in good agreement with the experimental ones for compound-treated, sprayed, and carbonitrided specimens. The relative errors of logarithm of cycle number are all less than 5%.
20 citations
TL;DR: The traditional concept of measurement traceability in the United States has focussed on an unbroken hierarchial pathway of measurement compatisons to national standards also ingrained in tradition is the tendency to focus on the audit trail rather than on a quality measurement assurance program in which there is sufficient accuracy to accomplish the intended purpose as discussed by the authors.
Abstract: The traditional concept of measurement traceability in the United States has focussed on an unbroken hierarchial pathway of measurement compatisons to national standards Also ingrained in tradition is the tendency to focus on the audit trail rather than on a quality measurement assurance program in which there is sufficient accuracy to accomplish the intended purpose. Evolutionary changes in the U.S. concept of traceability and the forces producing them will be reviewed. Specific examples are used to illustrate the traditional approach to traceability as well as options that might be exercised in the future.
17 citations
TL;DR: In this paper, a fiber optic chemical sensor was developed for measurement of pH in groundwater, which consists of a porous polymeric film immobilized with pH indicator, housed in a porous probe.
Abstract: A fiber optic chemical sensor was developed for measurement of pH in groundwater. The sensor consists of a porous polymeric film immobilized with pH indicator, housed in a porous probe. The optical spectral characteristics of the sensor showed very good sensitivity to changes in the pH levels tested when visible light (380 to 780 nm) was used. The sensor/probe system was tested in a laboratory environmental chamber and showed very good stability and reversibility under various confining pressures and flow rates.
17 citations
TL;DR: In this paper, the hybird behavior of surfacetreated mica and hardwood chemithermomechanical pulp (CTMP) in PVC composites was investigated, and the effect exerted by the concentration of reinforcements, composition of hybrid as well as the treatment of CTMP, on the mechanical properties of the hybrid composites were evaluated.
Abstract: In the present study, the hybird behavior of surfacetreated mica and hardwood chemithermomechanical pulp (CTMP) in PVC composites was investigated. In order to improve the compatibility of wood fibers with PVC and surface-coated mica, CTMP was subjected to different surface modifications by pretreating the fibers with maleic anhydride (MA), a mixture of MA and Na-silicate, and with an inocyanate (PMPPIC). The effect exerted by the concentration of reinforcements, composition of hybrid as well as the treatment of CTMP, on the mechanical properties of the hybrid composites were evaluated. In general, these properties improved compared to those of uncoated CTMP/mica-filled composites. Moreover, PMPPIC treatment renked best followed by MA — and MA + silicat treatments. The optimal concentrations of reinforcements and their compositions, which provided superior properties, varied according to the nature of the trestment of CTMP and of the individual mechanical properties themselves.
13 citations
TL;DR: In this article, an ultrasonic method and stage for real contact area (RCA) measurement on steel flat parts with technological surface layer is described. But the measurement can be taken during the process of surface deformation as well as for the surfaces already deformed.
Abstract: The paper contains a description of an ultrasonic method and stage for real contact area (RCA) measurement on steel flat parts with technological surface layer The stage allows measurement of RCA of test surface in contact with a rigid flat counterface The measurement can be taken during the process of surface deformation as well as for the surfaces already deformed
13 citations
TL;DR: In this paper, a simple Si9N4 material fracturing with transgranular crack propagation and a SiC-platelet measured by four different methods: single edge V-notched beam (SEVNB), single edge precracked beam, indentation fracture (IF), and chevron-notch beam (CNB).
Abstract: The validity of Kk determinations by various techniques usually employed and compared with each other is discussed in detail for two ceramic materials. They are a simple Si9N4 material fracturing with transgranular crack propagation and a Si9N4-25vol% SiC-platelet measured by four different methods: single-edge V-notched beam (SEVNB), single-edge precracked beam (SEPS), indentation fracture (IF), and chevron-notched beam (CNB). It is generally recognized that, in platelet composites, Kk values can be reliability obtained only by procedures adopting notched specimens in which the wake-zone of precracking is mechanically removed (SEVNB or renotched SEPB). In the present investigation the CNB method, in which the wake contribution to fracture resistance is generally small but not negligible, was also found to give stress-intensity factors at maximum load whose value was almost coincident with the KIc determined by SEVNB method. Using stereological concepts, fractographic observations, and acoustic emission (AE) experiments, the microstructural conditions for negligible wake-contribution during the subcritical stable crack extension in the CNB experiment were worked out and applied to rationalize the behavior of the present composite. Apparent toughness values markedly higher than the “true” Kk of the composite were measured both by the standard SEPB and IF method. Such a discrepancy is considered due, in the former case, mainly to traction forces between the precracked surfaces while, in the latter, to an insufficient account of the residual stress field associated with the indentation.
13 citations
TL;DR: In this article, a room-temperature experimental program was conducted on AISI type 316 stainless steel to determine the effect of wall thickness on the cyclic deformation behavior and fatigue life of thin wall, tubular, axial-torsional fatigue specimens.
Abstract: A room-temperature experimental program was conducted on AISI type 316 stainless steel to determine the effect of wall thickness on the cyclic deformation behavior and fatigue life of thin-wall, tubular, axial-torsional fatigue specimens. The following experimental variables were examined in this study: the depth of the surface work-hardened layer produced in specimen machining, and the effects of strain range and axial-torsional strain phasing. Tubular fatigue specimens were fabricated with wall thicknesses of 1.5, 2.0, and 2.5 mm. One as-fabricated specimen from each wall thickness was sectioned for microstructural examination and microhardness measurement. A specimen of each wall thickness was tested at each of three conditions - high strain range in-phase, low strain range in-phase, and low strain range out-of-phase - for a total of nine axial-torsional fatigue experiments. The machining-induced work-hardened zone, as a percentage of the gage section material, was found to have a minimal effect on both deformation behavior and fatigue life. Also, little or no variation in fatigue life or deformation behavior as a function of wall thickness was observed. Out-of-phase fatigue tests displayed shorter fatigue lives and more cyclic hardening than in-phase tests.
TL;DR: In this paper, the authors analyzed the sensitivity of two water leak tests, one requiring that a condom be filled with 300 mL of water and then examined visually for leakage, and the other requiring that the condom be not rolled, but merely placed in a horizontal position and examined.
Abstract: As part of quality assurance testing, latex condoms are often screened for pinholes using water leak tests. This report analyzes the seasitivity of two similar tests, both requiring that a condom be filled with 300 mL of water and then examined visually for leakage. One test, a Food and Drug Administration protocol, specifies that the condom be filled vertically, the open end pinched off, and then rolled horizontally on a towel. The second test, developed by the American Society for Testing and Materials, is the same, except the condom is not rolled, merely placed in a horizontal position and examined. Detectability of a defect is dependent on the pressure developed within the condom, wettability of the condom surface by the water, thickness, and expansion of the condom. Three brands and nine different models were studied to determine the range of values for these variables and the sensitivity of the tests were then calculated. Sensitivity (minimum hole size detectable) varies from approximately 100 μm radius to 3 μm radius. Note that the smallest defect observable is larger than the HIV virus.
TL;DR: In this article, a simple mechanical strain extensometer for high-temperature tensile testing of ceramic materials is described, which uses the lever-arm concept to proportionally reproduce the displacements of fiducial gage marks defined on a specimen.
Abstract: Design and development of a simple mechanical strain extensometer for high-temperature tensile testing of ceramic materials are described. The extensometer uses the lever-arm concept to proportionally reproduce the displacements of fiducial gage marks defined on a specimen. Various potential errors in strain measurement associated with the kinematics of this mechanical extensometer are analyzed and estimated. The extensometer exhibits a resolution of 5 microstrain (μɛ) and good long-term stability under moderate changes of ambient temperature. Limited results of simple isothermal creep tests on silicon nitride tensile specimens are presented to demonstrate the effectiveness of the device.
TL;DR: In this paper, a new technique for ultrasonic NDE of a sub-half-wavelength layer (given its thickness) using only the time-domain information was reported, and a satisfactory compatison between the measured values and the nominal value was observed.
Abstract: The purpose of this paper is to report a new technique for ultrasonic NDE of the wavespeed of a sub-half-wavelength layer (given its thickness) using only the time-domain information. The new technique was applied to aluminum plates with h λ ranging from 0.082 to 2.0 where h and λ are the plate thickness and the nominal wavelength, respectively. A satisfactory compatison between the measured values and the nominal value was observed.
TL;DR: The results of a systematic program undertaken to evaluate potential substitute materials for asbestoe-free gaskets used in power plant turbines are reviewed in this article, where three commercially available materials were subjected to a series of tests reflecting the requirements of a good gasket material for turbine applications.
Abstract: The results of a systematic program undertaken to evaluate potential substitute materials for asbestoe-free gaskets used in power plant turbines are reviewed. Thirty-three commercially available materials were subjected to a series of tests reflecting the requirements of a good gasket material for turbine applications. The results identified flexible graphite as the only material to meet or exceed the properties of asbestos gaskets. One limitation of flexible graphite uncovered in the program, however, is its relatively high stress relaxation behavior especially at temperatures above 650°F (343°C). Ten-thousand-hour stress relaxation tests were conducted in the temperature range of 500 to 850°F (260 to 454°C) to determine the usable temperature limit of flexible graphite. The effects of joint flexibility and reloading were also evaluated at high temperatures.
TL;DR: In this article, the authors explored the possibility of creating a new family of ultra-lightweight conductive shield materials using metallized microballoons as a conductive filler material.
Abstract: The need for lightweight, formable materials that can conduct elasticity and shield against electromagnetic interference (EMI) is widespread. Applications ranging from modeled cases for terrestrial electronics to shielding systems for metallize can benefit from such tailorable, lightweight conductive materials. This paper explores the possibility of creating a new family of ultra-lightweight conductive shield materials using metallized microballoons as a conductive filler material. The conductive costings investigated include gold, silver, and aluminum on ceramic microballoons in an epoxy matrix. Factors influencing the electrical conductivity are discussed, and the shielding performance is tested using X-band microwave transmission measurements and anechoic shielding effectiveness testing. Variables available that have the potential to allow application specific tailoring of the shielding material are described. Initial findings are discussed and performance is related to the microballoon volume fraction and costing materials. Results indicate that shield densities significantly below 1.0 g/cm2 are possible, with electrical surface resistivities approaching these of common metals.
TL;DR: The ASCOR (automated stress corrosion ring) test was developed to test aluminum alloys according to ASTM G 44 and using direct stressing as in ASTMG 49 as discussed by the authors.
Abstract: Alternate immersion stress corrosion testing according to ASTM G 44, Practice for Alternate Immersion Stress Corrosion Testing in 3.5% Sodium Chloride Solution, has proves to be representative for alumimum alloys in natural environments resembling the actual eavironmental conditions for aircraft. A simple automated stress corrosion testing method called the ASCOR (automated stress corrosion ring) test was developed to test aluminum alloys according to ASTM G 44 and using direct stressing as in ASTM G 49. Recommended Practice for Preparation and Use of Direct Tension Stress Corrosion Test Specimens. The method involves testing cylindrical or pin-loaded flat tension test specimens in a loading sing provided with strain gages to measure the load. Initiation of a stress corrosion crack (SCC) results in a small load decrease. During the test the load is measured periodically and stored in a data acquisition system controlled by a personal computer. A specific load decrease is used as the criterion for SCC initiation. The main advantages of the method are that a large number of specimens can be tested simultaneously in a climate chamber and that SCC initiation lives can be determined according to a clearly defined criterion without time consuming and subjective inspections, and without disturbing the test procedure.
TL;DR: In this article, a numerical simulation of the Marshall test is performed using a plane-stress finite element analysis with triaxial test determined properties as input parameters, and a constitutive plasticity model based on the Drucker-Prager yield condition is used to describe the elasto-plastic behavior of the specimen.
Abstract: The Marshall test is one of the most common methods used for mix design and quality control of asphalt concrete mixtures. However, this method is empirical in nature and does not provide fundamental engineering properties. Fundamental engineering properties provide a basis for rational analysis and design of asphalt concrete pavements. The triaxial test method described in this paper allows engineering properties such as internal angle of friction, [phi], cohesion, c, and elastic modulus, E, to be determined. The method of specimen preparation and the triaxial test setup are briefly described. A numerical simulation of the Marshall test is performed using a plane-stress finite element analysis with triaxial test determined properties as input parameters. A constitutive plasticity model based on the Drucker-Prager yield condition is used to describe the elasto-plastic behavior of the specimen. Analysis shows that the model very well describes the deformation progression before failure and can predict experimental Marshall stability value very closely. There is some underprediction of the Marshall flow, probably due to the idealization of an elastic-perfectly-plastic stress-strain relationship for asphalt concrete.
TL;DR: In this article, a laboratory scale attribution test has been designed to simulate particle-particle and particle-wall attrition forces which are similar to those experienced in commercial moving bed units, using two concentric rotating drums to induce particle breakage.
Abstract: A laboratory scale attribution test has been designed to simulate particle-particle and particle-wall attrition forces which are similar to those experienced in commercial moving bed units. The modified drum test uses two concentric rotating drums to induce particle breakage. Using this test, the distribution of particle shapes and sizes produced by catalyst attrition in a moving bed unit have been successfully duplicated.
TL;DR: The current interest in Bt and microbial insect control agents has been heightened by the recent development of significant resistance to chemical insecticides in a number of target insect species.
Abstract: During the past twenty years, a number of technological advancements have been made in the development of microbial pesticides for use in agricultural and forest insect control programs. The microbial pesticide currently used for the majority of these applications has been Bacillus thuringiensis (Bt) var. kurstaki. This organism has proven itself to be a valuable tool for the control of lepidopterous insects on vegetables, cotton, soybean, and in hardwood and coniferous forests. The expansion of Bt from the original vegetable crop applications to field crops and forest insect control programs has occurred along with significant advances in technology involving the culture, mass production, formulation, and application of this unique microbe. The current interest in Bt and microbial insect control agents has been heightened by the recent development of significant resistance to chemical insecticides in a number of target insect species. Additional advances in Bt formulation and application are foreseen for the next decade. These advancements should lead so further improvements in efficacy and increased usage of Bt preparations in agriculture and forestry.
TL;DR: In this paper, the influence of different compaction methods on the resulted density distributions of cylindrical specimens using a laboratory twin-probe nuclear density gage was examined, and the effect of compaction in layers was also examined.
Abstract: Cylindrical specimens are commonly used in laboratory testing of asphaltic paving mixtures. This paper describes a study that examined the influence of different compaction methods on the resulted density distributions of cylindrical specimens using a laboratory twin-probe nuclear density gage. Two common sizes of 102 mm (4 in.) cylindrical specimens, namely 64-mm (2.5-in.) high Marshall-size specimens, and 200-mm (7.87-in.) high triaxial test specimens, were considered in the test program. Four compaction methods were studied: drop-hammer compaction, kneading compactions, single-plunger compression, and double-plunger compression. In the case of 200-mm-tall specimens, the effect of compaction in layers was also examined. Test results show that, except for the kneading compaction method, the other three methods could all produce 64-mm-tall Marshall-size specimens of relatively uniform density distributions with density variation within 0.05 g/cm3. For 200-mm-tall specimens, only the double-plunger compression method was able to produce specimens with density distribution of similar uniformity.
TL;DR: In this article, the authors presented experimental results obtained in the evaluation of defects commonly found in graphite based composite structures, such as delamination, fiber breakage, and misaligned fibers.
Abstract: Acoustic Impact Technique (AIT), commonly known as “coin-tapping,” has been applied by previous investigators as a nondestructive evaluation technique to study disbonds in composite honeycomb structures. The experimental configuration adopted by previous investigators was somewhat restricted. In this study, a different approach to AIT is developed. This was done to overcome the experimental constraints encountered in the previous approaches. This paper presents experimental results obtained in the evaluation of defects commonly found in graphite based composite structures, such as delamination, fiber breakage, and misaligned fibers. The experimental approach adopted in this work has two main features. Primarily, the force-time history of the specimen's response to a low magnitude input pulse in different regions of the specimen is compared. Secondly, an Acoustic Emission (AE) wide band sensor was used in conjunction with the conventional acoustic impact technique. The combination of the AE sensor and AIT enabled the study of the material interaction with stress waves generated in the vicinity of the tapped region. Gross defects such as delaminations were identified through the change in the pulse width of the force input, while defects such as fiber breakage and misaligned fibers were successfully identified using AIT in conjunction with AE.
TL;DR: In this paper, the authors present the results of a laboratory study conducted to examine the water-induced damage of compacted and loose asphalt-aggregate mixtures from Riyadh, Saudi Arabia.
Abstract: This paper presents the results of a laboratory study conducted to examine the water-induced damage of compacted and loose asphalt-aggregate mixtures from Riyadh, Saudi Arabia. One asphalt cement and two typical aggregate sources (A and B) were used to prepare asphalt mixtures. Test methods used included the Marshall stability ratio, the wet-dry indirect tensile test (Lottman). and coating and stripping tests of uncompacted mixtures (ASTM D 1664, Test Method for Coating and Stripping of Bitumen-Aggregate Mixtures, and ASTM D 3625. Test Method for Effect of Water on Bituminous-Coated Aggregate-Quick Field Test). The test results have shown superior performance of mixtures prepared from Source A aggregate in comparison with Source B Differences in physical properties of the fine fraction between the two sources appear to be responsible for the noted difference in behavior However, mixtures with water susceptible aggregate (Source B) have exhibited improved performance when natural sand. used routinely in combination with crushed sand, is reduced or eliminated. The partial replacement of the crushed limestone filler by cement or lime had positive effects on performance of water-susceptible mixtures. Distinct improvements in 24-h Marshall stability were exhibited when 2% hydrated lime was added. Based on the results, the test methods deployed in this study appear to do a reasonable job in detecting moisture-susceptible pavement mixtures and in evaluating the relative effectiveness of additives in minimizing water damage potential.
TL;DR: In this paper, strain gages were used to study wave propagation in a single chain assembly of disks, and they were compared with those obtained using the optical technique of photoelasticity for both static and dynamic problems.
Abstract: The application of strain gages for the determination of static and dynamic contact loads in granular particles is demonstrated. For experimental convenience, the granular particles are simulated by circular disks fabricated from Homalite-100, a brittle polyester material. Stress field equations in the vicinity of the contact points are carefully evaluated to optimize the relative position of strain gages. The results obtained from strain gages were compared with those obtained using the optical technique of photoelasticity for both static and dynamic problems. Finally, as an example, strain gages are used to study wave propagation in a single chain assembly of disks.
TL;DR: Moire interferometry has been used for strain measurement in the materials testing laboratory as discussed by the authors with a measurement uncertainty of less than 0.1% corresponding to an accuracy of better than 1 μm m.
Abstract: The search for an adequate reference strain measuring technique for use in the materials testing laboratory has spanned several decades. Early methods relied on properly calibrated extensometers. Two examples are Tuckerman's Optical Strain Gage and Bergqvist's highly refined inductive and strain gage based extensometers. Length standards were used to calibrate these devices Initially, mechanical displacement mechanisms were used as extensometer checking devices, but with the advent of lasers, the Michelson interferometer has become a dominant displacement measuring tool Advances in stabilizing hardware and electronic detectors have led to the availability of Michelson systems with a resolution better than 5 nm. Microelectronics manufacturing techniques have been used to replicate entire Michelson systems on a silicon chip Advances in detector technology have also led to interferometric linear encoders with resolutions commensurate to classical interferometers. New techniques are being developed that can report strain and do not require initial calibration by displacement measuring instruments Moire interferometry, using a reference grating frequency of 2400 lines mm, has many valuable traits for providing laboratory strain measurements traceable to the National Institute for Standards and Technology (NIST). Experience with strain calibration by more indicates a measurement uncertainty of less than 0.1% corresponding to an accuracy of better than 1 μm m. Bonded metallic electrical resistance strain gages possess essentially limitless resolution, but accuracy must be established. When properly calibrated, bonded strain gages operating within their elastic range could serve as Class A extensometers. This paper reviews some of the more interesting approaches from the past, analyzes some current methods being investigated, and comments on possibilities for the future concerning the difficult task of finding a suitable calibration technique for use with strain measuring devices.
TL;DR: In this paper, a suggested methodology for the accurate and precise fabrication of Iosipescu shear test specimens is presented as verification of the methodology and dimensional data and the associated error from specimens fabricated are presented as well.
Abstract: The experimental measurement of the shear modulus and shear strength has been of special interest to the materials and composites community for a number years. In recent years, the Iosipescu shear test method has become popular and widely used. The most widely used test fixture is the Modified Wyoming test fixture which requires a specific and accurately fabricated specimen. To date, the methodology to fabricate and inspect these specimens has been left to the discretion of the individual investigators. This technical note presents a suggested methodology for the accurate and precise fabrication of Iosipescu shear test specimens. Dimensional data and the associated error from specimens fabricated are presented as verification of the methodology.
TL;DR: In this article, beryllium-copper (Be-Cu) spring materials with tensile strength in the range of 70 to 145 ksi were subjected to cyclic loading in air and salt water environments.
Abstract: Fine gage, 0.006-in. d(0.15-mm) thick, beryllium-copper (Be-Cu) spring materials with tensile strength in the range of 70 to 145 ksi were subjected to cyclic loading in air and salt water environments. Plain and notched (center hole) hour glass specimens were subjected to sinusoidal loading with R = (minimum/maximum) stress = 0.1 at cyclic frequencies of 50 Hz in air and 1 Hz in salt water. Fatigue life was typically from 10[sup 4] to 10[sup 6] cycles with crack initiation as the dominant fatigue process. The excellence fatigue performance of Be-Cu alloys in salt water is well-known, however, current findings demonstrate 10 to 37% reduction in fatigue strength of unnotched specimens in this environment for a life of 3 x 10[sup 5] cycles. This strength degradation is attributed to the use of a lower cyclic frequency for present than for previous tests, i.e., 1 versus about 20 Hz. There was no effect of salt water on crack initiation in notched specimens. The ratios of the fatigue strengths, namely (cold-rolled/annealed) and (aged/annealed), for plain and notched specimens tested in air, decreased from 2 to about 1.4 as fatigue life increased from 10[sup 4] to 10[sup 6] cycles. This effect is attributed tomore » cyclic hardening of the annealed material. The fatigue stress concentration factor, K[sub f] = (plain/notched) fatigue strength, increased by about 30% as fatigue cycles increased from 10[sup 4] to 10[sup 6]. The ranking of K[sub f] values of the various material conditions from highest to lowest was: cold-rolled, aged, and annealed.« less
TL;DR: In this paper, the superplastic flow characteristics of advanced aluminum alloys such as the low-density aluminum-lithium alloys and the high-temperature intermetallics (processed by rapid solidification, mechanically alloying, powder metallurgy techniques).
Abstract: Special test equipment is required in order to determine the superplastic flow characteristics of advanced aluminum alloys such as the low-density aluminum-lithium alloys and the high-temperature intermetallics (processed by rapid solidification, mechanically alloying, powder metallurgy techniques). The superplastic flow characteristics under optimum conditions of strain race and temperature are necessary as input data to the computer process model weed to predict optimum pressure-time cycles for the SPF process. Most published tensile flow stress data for superplastic deformation was developed under constant crosshead speeds and at atmospheric pressure. In order to establish accurate flow characteristics, testing must be conducted: (1) at a closely controlled temperature, (2) at a controlled constant true strain rate, and (3) under hydrostatic pressure (to prevent cavitation). This paper discusses the design and development of a test system with these capabilities and also highlights typical results for three aluminum-lithium alloys.
TL;DR: In this paper, the influence of temperature, detergent type, and labric finish on bacterial survival and strength retention and clongation in fabrics were investigated, and the results showed that fabric finish did not have any significant effect on the bacterial survival but did influence both strength retention, and breaking clochation.
Abstract: The influence of temperature, detergent type, and labric finish on bacterial survival and strength retention and clongation in fabrics were investigated in this study. Previous research has shown that temperature is a critical factor in the removal, redeposition, and destruction of microorganisms in the laundering process. The results showed that fabric finish did not have any significant effect on bacterial survival but did influence both strength retention and breaking clongation. Temperature significantly affected bacterial survival and breaking strength and clongation. The addition of a detergent, especially a phosphate detergent, in the laundering process is important in diminishing bacterial survival on fabrics.
TL;DR: In this article, the effect of abrasion on the compressional properties of different woves textile fabrics was investigated using an Accelerator under wet and damp conditions and measured via mass loss.
Abstract: This paper is concerned with the effect of abrasion on the compressional properties of different woves textile fabrics. The abrasive wear was induced using an Accelerator under wet and damp conditions and measured via mass loss. The compressional properties, i.e., compression and compressibility, were determined under comparable experimental conditions on an Instron Tensile Tester. Changes in the compressional properties of the fabrics caused by increments of pressure in the Instron were noted. The relationship between the compressional properties and such physical properties as mass, thickness, density, and specific volume of the fabrics before abrasion is also reported. The damp-abraded fabrics showed higher percentage increase or decrease difference in fabric compressional properties at given incremeats of pressure than the wet-abraded fabrics when compared to the unabraded fabrics.