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A disadvantage of metal matrix composites (MMCs) is their assumed brittleness, which results in a low KIc. A possible way to make aluminum MMCs tougher is to heat treat them. In this investigation the influence of three different heat treatments on the KIc of AA6061 and AA6061 with 20 vol% Al2O3 is investigated. Special attention is paid to the set of requirements needed to obtain a valid KIc, as in some studies these are given little attention. In MMC material, the specimen geometry is governed by the delivered shape, which increases the risk of obtaining KQ instead of KIc values. It proves to be possible to obtain valid KIc data for the MMC using the standard disk-shaped compact tension geometry. The KIc of the MMC is around 21 MPa √m and the influence of the heat treatments on the KIc seems to be very small. The reduction in KIc by the addition of 20 vol% Al2O3 particles to AA6061 is moderate, in view of the KIc of the matrix material, which on average is 27 MPa √m.

There are many test methods to measure the impact resistance of fiber-reinforced concrete that are complicated, time consuming, and expensive. A practical test method has been developed to measure the impact resistance of high-strength fiber-reinforced concrete (HSFRC). The equipment developed can also be used for testing aggregate impact values by simply changing the base plate of the machine. A machine was developed to measure the surface abrasion resistance of HSFRC. Testing fiber-reinforced concrete for surface abrasion resistance was found to be extremely difficult if realistic and practical results were desired. In this study the influence of silica fume on the properties of HSFRC was investigated by using silica fume at two different percentages and with three different hooked-end fibers, namely, 30/0.50, 60/0.80, and 50/0.60 length/diameter (mm/mm). Fibers were added to concrete in three different percentages of 0.5, 1.0, and 2.0% by volume of concrete. The results show that including fibers in high-strength concrete improves impact resistance, surface abrasion, and splitting tensile strength. Due to copyright restrictions, the access to the publisher version (published version) of this article is only available via subscription. You may click URI (with DOI: 10.1520/JTE12166) and have access to the Publisher Version of this article through the publisher web site or online databases, if your Library or institution has subscription to the related journal or publication.

This paper describes development of an automated technology to quantify surface segregation seen during construction of hot mix asphalt concrete pavements. Segregation manifested on the surface produces nonuniform surface macrotecture. A laser-based system was used for detection of nonuniform surface macrotexture caused by segregation. Two segregated test sections and a control test section were tested to evaluate the laser texture method. Laser texture data were gathered from three sites, and sand patch and nuclear density tests were performed at 25 ft (7.62 m) intervals along three sections. In addition to the above, visual surveys were performed to confirm the measurements. Based on the test results, it was found that the nuclear density test could not be used to detect surface segregation but it could be used as a confirmation test. Test results from the control section were used to establish a correlation between the sand patch tests and the laser texture data.

This paper describes the development of a fracture test for determining the fracture energy of asphalt concrete. The test will be used in combination with numerical analysis and field studies to obtain a better understanding of the mechanisms of reflective cracking in asphalt concrete overlays. A review of the literature revealed that a single-edge notched beam (SE(B)) test specimen was the most promising fracture test for the objectives of the reflective cracking study. Existing servohydraulic testing equipment was modified to perform the SE(B) test along with new loading fixtures, sensors, data collection, and analysis procedures. Preliminary tests were conducted to develop test procedures, to obtain a better understanding of crack-front characteristics, to investigate test repeatability, to examine variations of fracture energy with temperature, and to investigate mixed-mode fracture. The results from the tests follow expected trends and test variability appears to be within a range typical for asphalt concrete fracture testing.

The objective of this paper is to examine the variation of shear strength with respect to suction and develop a simple method for prediction of suction from shear strength data. The measured values of total suction and the shear strength of the soils are used to predict a fitting parameter that defines the nonlinear variation of suction with shear strength. The equation proposed by Vanapalli and Fredlund isused. The parameter is estimated for two types of soils, red soil and black cotton soil, available in the state of Karnataka, using measured values of total suction and unconfined compressive strength by nonlinear regression analysis. The nonlinear equations developed between suction and unconfined shear strength are useful in unsaturated soil engineering practice.

Implosion of vaporous cavities is exothermal, thereby heating the cavitating liquid. In vibratory cavitation erosion (VCE) tests the erosion rate increases with test liquid temperature. In order to obtain the erosive properties of a given material at a given temperature, it is necessary to control the test liquid temperature. The prevailing ASTM standard specifies cooling of the test liquid, and allows a maximal temperature rise of 4°C during the VCE test. However, cooling alone does not ensure the required uniformity of test liquid temperature near the specimen. In order to obtain a uniform test liquid temperature near the specimen during VCE tests, a thermal control system is recommended. This system consists of three subsystems for cooling, heating, and mixing the test liquid. Correct location of the temperature sensor and operation of the thermal control system improve the thermal control appreciably. This control method was used during 24 VCE tests with water as a test liquid. The average temperature rise in these tests was 1.5°C during the transient stage and 0.2°C during steady state operation.

The objective of this research was to investigate the stripping problem in bituminous mixtures using both conventional and image processing techniques (IPT). Partial factorial combinations of asphalt mixture slabs were fabricated. A Marshall mold was modified to produce slabs of 300 mm × 300 mm × 60 mm. The mixtures were prepared using different combinations: two types of aggregates (limestone and valley gravel), two asphalt penetration grades (80/100 and 60/70), three types of additives (lime, cement, and a mixture of lime and cement), and one aggregate gradation (average of ASTM boundaries). The slabs were exposed to one of four environmental conditioning techniques: wet-dry (W-D), freezing-thawing (F-T), water immersion (I), and surface bonding (S-B). Eighty-one slabs were prepared, 19 were tested without conditioning (control slabs), and the rest were exposed to different weathering conditioning. Four cores were prepared from each slab, two for the indirect tensile strength test and the others for the Marshall stability test. A normal-based camera was used to map the surfaces of the control and conditioned slabs as well as cross-sections generated from cores tested under the indirect tensile strength test. The Silicon Video Image Processing (SVIP) software was used to digitize images for the surfaces of slabs and cores. Images were analyzed to prepare statistical parameters, intensity diagrams, and histograms for intensities based on two approaches: area-based analysis and line-based analysis. Results of the analysis indicated that 1) conventional and image processing techniques proved that surface bonding increased stability and tensile strength for conditioned slabs more than for unconditioned slabs; 2) IPT predicted stripping in limestone mixtures with AC 80/100 using the retained intensity concept and this result agreed with that of retained Marshall stability (RMS); however, it did not consistently predict the stripping potential of mixtures consisting of valley gravel due to the tone intensity effect of aggregate; 3) lime additive demonstrated the best indirect tensile strength and Marshall stability; however, the additive mix consisting of lime and cement exhibited reduction in water damage for mixtures with AC 60/70; 4) slab mixtures resisted weather conditioning more than conventional cylindrical Marshall specimens; and 5) an area-based analysis scheme using peaks, not averages of intensities, was more reliable in predicting stripping than the line-based analysis, and it was more reliable for core cross-sections than slab surfaces.

Tensile stress-strain properties in the hoop direction were obtained for 100-mm diameter SiC/SiC ceramic matrix composite cylinders using ring specimens machined form the cylinder ends. The cylinders were fabricated from 2D balanced SiC fabric with several material variants, including wall thickness (6,8, and 12 plies), SiC fiber type (Sylramic, Sylramic-iBN, Hi-Nicalon, and Hi-Nicalon S), fiber sizing type, and matrix type (full CVI SiC, and partial CVI SiC plus slurry cast + melt-infiltrated SiC-Si). Fiber ply splices existed in all the hoops. Tensile hoop measurements are made at room temperature and 1200 C using hydrostatic ring test facilities. The failure mode of the hoops, determined through microstructural examination, is presented. The hoop properties are compared with in-plane data measured on flat panels using same material variants, but containing no splices.

Differential expansion and contraction between the top and bottom of a concrete slab results in curling. Curling affects slab stresses and deflections and is an important component of any mechanistic-empirical design procedure for concrete pavements. Although some curling is caused by temperature and moisture gradients that fluctuate daily, a significant portion of the curling can be attributed to the combined effects of nonlinear “built-in” temperature gradients, irreversible shrinkage, and creep, which can be represented by an effective built-in temperature difference (EBITD). A procedure for estimating EBITD of in situ slabs using a falling-weight deflectometer and a finite-element program is presented. This procedure was used to estimate EBITD for instrumented slabs at Palmdale and Ukiah, California. Differences in restraints (from adjacent slabs, shoulder, base friction) and variability in concrete material properties resulted in EBITDs ranging from -5°C to greater than -30°C.

C-ring specimen geometries are used to ascertain Weibull parameters for spatially distributed flaw populations in ceramic gun barrels. A review of previously published results used to compute effective areas and effective volumes for this test specimen geometry is presented along with deficiencies associated with these computations. In addition, the results of the numerical analyses presented utilizing finite-element analysis and component level reliability algorithms clearly indicate that geometric constraints called out in the current ASTM standard for C-ring testing must be revised.

The monitoring of fatigue crack initiation and propagation in cruciform joints is very complex and time consuming. The amount of technical information generated by a single fatigue test can vary from a terse noting of the cycles to the point till the specimen breaks, to a continuous observation of crack lengths. A wide variety of experimental methods are available to study the changes in bulk properties taking place in a test specimen (with simple geometry) while it is subjected to alternating stresses. However, in many fatigue test situations (for instance, in cruciform joints), it is very difficult to monitor the changes due to multiple possible crack initiation points. In this paper, a method has been developed to monitor the crack initiation for cruciform joints with different geometry by resistance-type strain gages. Also, the application of a relatively new, thin-film bondable transducer, commercially available under the name ‘crack propagation gage,’ was evaluated for fatigue crack propagation tests for cruciform joints at room temperature. Additionally, the strain gage and the crack propagation gage instrumentation system can be used for direct test machine control, permitting completely automated fatigue crack growth testing.

Analytical protocols are presented for the determination of experimentally realizable relatively “simple” loading functions, consisting of concentrated loads that mimic actual quasistatic and/or dynamic more complicated loadings, to produce similar nearly equal equivalent deflection patterns. These computational simulations in essence represent a series of virtual experiments. Two protocols are formulated for the determination of equivalent loads. The first consists of “lumped loads” and in the second, Galerkin's method is used to determine the system of equivalent concentrated loads. The accuracy of the protocol is examined and shown that the simulation error can be made negligible with a manageable finite number of equivalent concentrated loads.

Significant differences occur in Rockwell B hardness (HRB) tests depending on whether the 1.588 mm diameter ball indenter that is used is made of steel or of tungsten carbide (WC). It is important to study and assess the effect of different indenter materials on the HRB tests since the Rockwell hardness test method standards, published by ASTM International and the International Organization for Standardization, now permit the use of either steel or tungsten carbide ball indenters. In this paper, finite-element analysis (FEA) is used to simulate the HRB indentation process using steel and WC ball indenters on the same test materials under the same testing conditions. The influence of the deformable steel and WC indenters on the HRB tests is analyzed by comparing their FEA results with those of a simulated nondeformable rigid indenter. The contact pressure, stress, strain, and deformations of both the indenters and the tested materials during the loading and unloading period are analyzed. The FEA simulation results show that the HRB difference between steel and WC ball indenters is about 0.4 HRB for 40–78 HRB levels, but increases to 0.56 HRB at the 23 HRB level. The FEA simulation results agree with experimental HRB results.

A standard method for the determination of the shear strength of a polymeric foam is a lap shear geometry. The accuracy and validity of this test was evaluated by means of finite-element modeling. Model results show that the shear stress is not constant over the length of the sample, with shear peaks at the ends, so that the average shear stress in the sample can be quite different than the maximum shear stress experienced. Normal stresses are also present at the sample ends giving rise to a combined stress field. Experimental results for a polymeric foam bonded to steel edge plates show that the measured shear strength can vary significantly with the sample geometry (length). Maintaining a minimum length/thickness ratio, as specified in the ASTM C 273 standard, does not necessarily result in a sample with the most uniform shear field, and therefore the most accurate measure of the true shear strength.

This paper presents the development of a test system to evaluate the ignition susceptibility of several common plastics in nitrogen trifluoride (NF3) as compared to gaseous oxygen. A test system was developed to allow for measurement of the autogenous ignition temperature (AIT) in both gaseous oxygen and NF3. The autogenous ignition temperatures of Kel-F® 81 PCTFE, Neoflon® PCTFE5, Teflon® PTFE, Nylon 101, PVDF, and PVC were determined in gaseous NF3 and in gaseous oxygen.

Roofing systems are exposed to wind pressures and thermal stresses. Through a North American roofing consortium (Special Interest Group for Dynamic Evaluation of Roofing Systems—SIGDERS) the National Research Council Canada fabricated a facility to evaluate roof assemblies under simultaneous wind and thermal effects. The overall objective of this paper is to present the commissioning process of the facility based on experimental investigations that were carried out on a single-ply roofing system with a PVC membrane. For this study, roofing system responses were measured under simulated simultaneous wind and heat/cold conditions. A systematic attempt also was made to quantify the system response and to characterize the membrane properties. This was performed on a cold-conditioned system as well as by subjecting the membrane samples to the same cold-conditioning program in a laboratory freezer. Membrane samples were characterized by mechanical and chemical methods. Comparison of laboratory-conditioned membranes and wind-tested systems revealed the effects of cold conditioning and wind loading. Neither the wind uplift nor the mechanical properties (tensile breaking strength, elongation at break, tear strength, and seam strength) nor the chemical properties (glass transition temperature and weight loss) were affected by the selected cold conditioning. Based on these findings, directives for further studies are presented for this ongoing project.

The fracture toughness of laser beam welded ferritic steel has been measured in the ductile-to-brittle transition regime using precracked bend specimens. The precracked welded specimens showed a complex fracture behavior, which involves crack path deviation. It was found that the large scatter of the cleavage fracture toughness and its temperature dependence can be characterized by the Master Curve Method (MCM). The results promote the validity of Engineering Lower Bound Method (ELBM) to derive lower bound toughness of laser beam welded steel. To enable a successful application of the Methods, it was necessary to add fracture toughness data censoring to the method, which takes into account the phenomenon of crack path deviation. The application of the censoring criterion requires additional fracture surface investigations, which can be performed easily using a conventional low magnification light microscope.

Experimental results showed that ASTM D 638 Type IV flat tension specimens, made of a Nylon-11 matrix containing a large volume concentration of Nd-Fe-B particulates, failed at a location where the straight gage section of the specimen ends and the curved transition region begins. The stress distribution in this specimen was analyzed using the finite-element method, and it was found that there is a stress concentration at this location. The stress distributions in tension specimens with both single- and double-arc transition regions were analyzed and stress concentration factors were calculated. A linear relationship between the magnitude of the stress concentration factor and the ratio of the width in the gage section and the arc radius of the transition region is identified. This study shows that it is possible to reduce the magnitude of the stress concentration factor for the ASTM D 638 Type IV flat tension specimen by redesigning the specimen geometry without changing its overall size.

ASTM standards are widely used to determine the plastic strain ratio r to characterize the normal anisotropy and the planar anisotropy of sheet metal. The values determined by mechanical testing are quoted at a strain of 15%. These are used for comparing two techniques of measuring the plastic strain ratio or the anisotropy of two materials. The present work reports the variation in the plastic strain ratio of prestrained material. The r values of biaxially prestrained steel sheet have been investigated using the ASTM as well as the magnetostrictive methods of measurement. An error analysis on the mechanical measurements has been performed to examine the agreement between the different definitions of the plastic strain ratio (rr, rint, rt, and rmx1) and the accuracy (based on coefficient of variation), in view of the need to measure the plastic strain ratio at low strain levels. Various means to ensure accuracy in measurement are described. Plastic strain ratio of sheet deformed to different biaxial prestrains has also been characterized using the magnetostrictive method (Modul r test). It is found that the difference between the r values determined using the ASTM and the Modul r methods changes with strain and strain path. The nominal difference between the two methods was found to be comparatively consistent over strain paths ranging from plane strain to equibiaxial tension. The Modul r values for prestrains along these strain paths investigated were found to be relatively consistent and hence usable. For prestrain along the strain path β = −0.45 (negative minor strain regime), the nominal difference was considerable. In view of the above, it is not appropriate to measure rapidly the r value of the material in the negative minor strain regime, in particular using magnetostrictive means, and to correct it using the “systematic error” between the two techniques. This restricts the usability of the Modul r test in measuring the plastic strain ratio of deformed sheet metal, particularly after a prestrain in the negative minor strain region.

The rate of mass loss in vibratory cavitation erosion tests varies with time. As a consequence, this process is treated empirically. It is suggested by the author that the cumulative mass loss-time curve test results can be represented accurately by the Weibull cumulative distribution function. This model was verified for 26 tests of nine metals. Among these metals is Ni 200, which is a standard reference material for erosion tests. This model allows treating the results of vibratory cavitation erosion tests analytically, thereby obtaining invaluable information from the test data.

The test surface of a specimen for cavitation erosion testing is prepared by several machining operations. These operations induce alterations on the surface and in the material beneath it, thereby forming an affected material zone. The properties of this zone affect the mechanical and metallurgical properties of the material. As a consequence the erosive properties are affected too, but are not easily detected on the cumulative erosion-time curves. The cumulative erosion-time curves of Ni 200 erosion tests were modeled by the Weibull cumulative distribution function. The equivalent Weibull plot consists of two intersecting straight lines, thereby providing a bimodal plot with a decreasing slope. Each line describes a different erosion mode. The first mode, from test onset to the intersection point, describes the erosion process of the specimen's boundary layer. Since this layer is removed by means of the erosion process, it is designated as the erosive boundary layer. The second mode, from the intersection point onwards, describes the erosion process of the homogeneous material. Analysis of the Weibull plots of Ni 200 erosion tests enables determination of the erosive boundary layer thickness and erosion time; it further facilitates the evaluation of the erosive boundary layer effect on the entire erosion process. The Weibull method enables construction of plots describing the erosion process of an ideal specimen, with an erosive boundary layer of 1 μm thickness. Plots of this kind may be used to characterize Ni 200 and to compare erosion properties of various materials.

The effects of strain rate and temperature on the mechanical behavior of a magnesium alloy (ZC71) and its corresponding composite reinforced with SiC particles are investigated. The experimental procedures of testing at high strain rate and different temperatures are described. The tensile stress-strain responses of both the base and the reinforced materials were found to depend on the applied strain rate (0.003 ≤ έ ≤ 700 s−1), the test temperature (−150 ≤ T ≤ 200°C) and the presence of reinforcement. Comparative results are presented in terms of the main mechanical parameters, and quantitative conclusions are obtained of the influence of temperature and strain rate, using quasistatic and dynamic tests, on the mechanical behavior of these materials.

Fatigue crack growth behavior of through-the-thickness cracks emanating from the notch root in an aluminum alloy was investigated with particular emphasis on the evaluation of crack closure and its effects on fatigue crack growth rate. The tests were performed on SE(T) specimens both under constant amplitude (CA) and spectrum (modified FALSTAFF) loads. The near-tip strain measurement method was used for crack closure estimation in the short and long crack ranges. An attempt was also made to determine the crack closure value corresponding to the crack-tip shielding through fractographic analysis. In CA fatigue loading, short cracks grew faster than long cracks under the same nominal applied SIF range, ?K, and also grew below the threshold SIF range, ?Kth, for long cracks. The crack closure level gradually increased in the short crack range and was observed to stabilize at a crack length of about 0.5 mm. The discrepancy in the observed crack growth rates between long and short cracks was attributed partly to the difference in crack closure levels. The fatigue crack growth rates of short cracks under modified FALSTAFF loading were observed to be rather scattered, and the crack closure level was found to gradually increase and stabilize within a larger scatter band. These observations are explained on the basis of likely effects of several high-peak overloads present in the applied spectrum load. In the long crack range, the crack closure value obtained by the near-tip strain measurement method appears to provide an upper-bound value, whereas that obtained through fractographic analysis provides a slightly lower estimate, which may be considered as a lower-bound fatigue crack closure value.

We measured the shear strength of wood by the asymmetric four-point bending test using notched beam specimens of Todomatsu (Japanese fir, Abies sachalinensis Fr. Schmidt). The notches were cut on both longitudinal-tangential (LT) planes along the neutral axis, and the load was applied asymmetrically on the longitudinal-radial plane to obtain the shear strength of the LT plane. In the tests, the notch depth and span-to-thickness ratio, which was defined as span/depth ratio, varied and the influence of specimen configuration was examined. Independently of the bending tests, block shear and Iosipescu shear tests were performed and the shear strengths obtained were compared with those obtained by the bending tests. When the specimen had a proper configuration, the value of shear strength was stable over a wide span/depth ratio range and was close to that obtained by the Iosipescu shear test. Hence, we think that the asymmetric four-point bending test using a notched beam specimen is promising for evaluating the realistic shear strength of wood.

The Hveem stabilometer is used by several states to obtain materials characteristics for designing pavements. This paper presents equations that relate the Hveem stabilometer R-value and S-value with the elastic modulus. It is shown that the elastic modulus is dependent on the following: the R- or S-value, the exudation pressure, the overconsolidation ratio, the Poisson's ratio, and the angle of internal friction of the material. It is also shown how the compaction pressure might affect the calculation if the material is time-dependent or viscoelastic. An example problem is provided to show how to calculate the elastic modulus using these pertinent factors. Typical laboratory test data are also presented to demonstrate the relationship between the R-value and the elastic modulus for three different highway soil materials. It is shown that the exudation pressure is indicative of the moisture content of the test samples. The R-value and elastic modulus are shown to be quite sensitive to the moisture content.

Acoustic Emission (AE) has been used to detect onset of ductile tearing in instrumented Charpy impact tests to enable determination of dynamic ductile tearing initiation toughness using a single specimen method. An AE based method was developed whereby a conventional instrumented impact tester is instrumented with a commercial broadband acoustic emission sensor mounted on the anvil. The results obtained using the new AE based method were compared to the results obtained by other researchers using specially developed AE sensors located inside the tup. Tests using both AE and direct measurement of the load-line displacement during the instrumented Charpy testing were conducted simultaneously on a conventional ship grade steel. V-notched and fatigue precracked test pieces were tested in the temperature range +23°C to −80°C. The results obtained with AE monitoring were compared to those obtained using the optical Direct Displacement Interferometric Strip (DDIS) method developed by the authors. Good correlation was found between the initiation fracture toughness determined at 0.2 mm blunting and crack extension, J0.2, by the multispecimen Ductile-Brittle Transition (DBT) method and those derived from single specimens applying AE and the new interferometric method to detect ductile fracture initiation. Fast Fourier Transformation (FFT) was applied to analyze the AE signals. The results showed that the different phases of AE and fracture modes could be distinguished based on characteristic frequency and time variance.

In the past some studies have been carried out to investigate the melt strength of polymers with the purpose of comparing the results obtained with different materials and at different temperatures. In those experimental activities, once that the testing instrument had been chosen, the polymers were considered the object of the investigation and the attention was rarely focused on the testing geometry. The present work, instead, intends to analyze the influence that the geometry of the extrusion die has on the melt strength of polymers. In particular, attention is focused on the analysis of the differences produced on the melt strength of a material, when the extruded filament is subjected, via the use of two different dies specifically designed, to two distinct temperature profiles along the stretching axis. This investigation highlights that the testing geometry chosen for an experimental activity based on melt tension tests, via haul-off measurements, plays a fundamental role in the correct interpretation of the results. In fact it is demonstrated that the correct choice of the extrusion die allows one to obtain results much more similar to the real processing type that, using melt tension tests, has to be analyzed.

Thermal power stations that use pulverized coal as fuel generate large quantities of fly ash, resulting in environmental and disposal problems. Increasing demand for power leads to a greater use of coal and hence a further increase in the quantity of fly ash. These problems can be solved if the fly ash is put to use in an environmentally friendly way. Among the various uses for fly ash, the most massive and effective use is in geotechnical engineering applications. The study of fly ash and its interaction with soil is a must towards this goal. In the present investigation, an attempt has been made to study the engineering properties of fly ash—black cotton (BC) soil mixes with special reference to their use as sub-base materials in pavement construction. The study aims to understand the effect of fly ash on the California bearing ratio (CBR) of BC soil. The CBR variation is observed to depend upon the particle size distribution and pozzolanic nature of fly ash. The study indicates that addition of fly ash increases the CBR of BC soil significantly.

The technique proposed here adopts short-term stress relaxation testing (SRT) to determine the metallurgical life of 1CrMoV large rotor steel. SRT has been performed at two temperature levels of 550°C and 600°C, on samples taken from the core region of a large rotor. At 550°C, five initial prestrains ranging from 0.2–1.0% strain were applied, while at 600°C, the specimens were relaxed from 0.6% and 0.8% prestrains. All test durations were kept between 4 to 5 h. To validate the results, a few conventional creep tests have been conducted at same temperature levels and at different stresses. The initial data, stress versus time, were converted into stress versus inelastic strain rate and the creep life was predicted with the help of the Monkman-Grant relationship (ˊes × tr) = C), where the value of the constant C is taken from experimental creep data. The comparison of creep life, predicted through SRT, with the actual creep data revealed that they were agreeing extremely well at higher test temperature, i.e. 600°C. The computed SRT data have delivered higher activation energy (600 kJ mol−1) than conventional creep testing (344 kJ mol−1). Detailed SEM and TEM studies revealed that degradation and/or development of microstructures had taken place and was commensurable to long-term creep exposure. Therefore, the methodology has the capacity to assess the inherent creep strength of any material.

In testing the mechanical behavior of rubbers, the incompressibility assumption is used to predict the deformed cross section under loading and thereby to calculate the true stress. There are, however, cases where rubbers can undergo considerable volumetric deformation in large strain experiments. Microstructural investigation through a scanning electron microscope was carried out on a void-filled natural rubber specimen to clarify the effect of voids on the compressibility feature. The microstructure of the natural rubber was observed qualitatively and quantitatively in uniaxial tension and compared to the microstructure in the underformed condition. The existence of the compressibility feature in the void-filled rubber was confirmed from a microstructural viewpoint. The findings indicate the necessity of accurate measurement of the deformed cross section in mechanical tests to obtain the true stress. To this end, an experimental setup capable of measuring the deformed cross section of the rubber specimens subjected to large uniaxial compression is proposed. To do this, the accuracy of laser beams is used for measurement of distance and a mechanical jig is developed to synchronize the movement of the laser transducer with the vertical crosshead of the load cell of a computer-controlled servohydraulic testing machine. Thus the constraints associated with conventional strain gages in measuring large strains are overcome. Finally, two natural rubber specimens and one high damping rubber specimen were tested in the proposed setup to display the adequacy of the developed device in measuring lateral deformation of rubber-like highly deformable solids in large strain uniaxial testing.

Three common ASTM methods (calorimetry, hot-wire, and laser-flash) for determining the thermal conductivity of refractory ceramics were compared using a commonly available bulk material having a microstructure sufficient for all three methods of analysis. Experimental measurements were made between 20–1200°C on a fine-grained, 94 % pure aluminum oxide using each technique. Results from the hot-wire and laser-flash methods were found to be similar and in line with theoretical and literature values. Values obtained by the calorimetry method were found to be lower than those of the other two methods, with a greater deviation at lower temperatures than at higher temperatures.

The wave-in-a-tube method allows for the estimation of material properties of gel-like, viscoelastic materials utilizing only a pair of matched ultrasonic pressure transducers. To employ this technique, a sample tube must be manufactured that (1) has an inside diameter that fits snugly around the element of the transducers being utilized, (2) is as long as the specimen size will allow given the diameter required, and (3) is made of a low-density, solid material. After construction of the container, the sample to be measured is placed in the tube with a pressure transducer fitted into each end with large air pockets eliminated. An ultrasonic pulse is sent through the sample, and the resulting waveform is analyzed per the Reynolds wave-in-a-bar method, yielding the magnitude of the complex moduli.

Some inaccuracies are possible during the near-surface residual stress measurement of textured material by X-ray diffraction using the standard multiexposure technique. Diffraction intensities depend on factors like inclination of the sample, the rotation of the beam, and the position of detectors. Low intensity due to texture can result in increased percentage error observed stress values. Anisotropy of elastic constants in textured materials can further increase the errors in measured stress. In the present study, the effect of texture on residual stress has been studied for seamless Ti-3wt%Al-2Vwt% tubes, in pilgered and annealed conditions, by superimposing the residual stress measurements on the pole figure obtained by texture measurement. A general approach has been developed for accurate determination of the stress tensor in textured material. This consists of the selection of inclinations giving rise to high intensity peak, the selection of rotation angles symmetric to the pole figure to get similar intensity from both the detectors (where this is not possible one detector with low intensity is shut off), and the calculation of the bulk X-ray elastic constants using the single crystal elastic data and texture. Cold worked Ti-3wt%Al-2Vwt% tubes had the highest stress along the rolling direction and that is compressive in nature. The principal residual stresses in the pilgered tubes were along the rolling and transverse directions, and annealing leads to reduction and reorientation of the stresses.

As part of the National Cooperative Highway Research Program Project 4–19(2), a series of uncompacted voids tests was performed using the ASTM Test Methods for Uncompacted Void Content of Fine Aggregates, C 1252, and the Virginia Department of Transportation VTM-5 test devices. Comparisons between the uncompacted voids measured by the two devices were made by using five different measurement methods on each of six different fine aggregates. The effects of test procedure and/or device, and their interactions with particle size on the measurement of uncompacted voids were also examined. As expected, the findings indicate that the graded sample of ASTM C 1252, Method A produces a significantly lower result for uncompacted void content than do the other four methods. However, the five test methods are significantly correlated. Furthermore, while there appears to be an interaction between test device and particle size, this effect is negated when the graded sample of ASTM C 1252, Method A is used.

Specially designed facilities for creep testing of ultrahigh-temperature alloys are presented. Ohmic heating is chosen for easy access to the sample, quickly attainable heating and cooling rates, and simplicity in design and operation. Strain is measured with a video extensometer by means of the software SuperCreep. SuperCreep allows fast and automated analysis of creep curves. For short but precise representations of creep curves, Bezier splines are used. Creep tests on pure Pt, Pt-10 wt% Rh, and the oxide dispersion strengthened Pt-base alloys Pt DPH and Pt-10 wt% Rh DPH between 1200 and 1600°C have proven the reliability of the equipment. Stationary creep rates follow the Norton power law. Stress exponents, activation energies, and pre-exponential factors are given for the four alloys investigated.

To prevent the adsorption impediment of H2S in the trace sulfur analyzer approved by ASTM D 4045, a specially prepared pure ceramic tube has been advanced to be the only usable reactor for hydrogenolysis procedure. However, a conventional ceramic tube becomes usable by inhibiting the H2S adsorption on the basic impurities by a substitute adsorption of CO2 that can be introduced continuously with H2 in the ceramic reactor. Applying the OxyHydro procedure to reduce the carbon deposit in the analysis of kerosene, a large overestimation error occurred in the determination of a single ppb of sulfur even using the specially prepared pure ceramic tube. The overestimation error was completely eliminated by the continuous introduction of CO2 with H2, even using conventional ceramic reactors. By following procedures to suppress noise from the system, the original limit of detection of 25 ppb sulfur for the analyzer was improved to 0.3 ppb.

Different biaxial flexure test geometries were investigated to determine the most reliable test for evaluating the strength of float glass specimens before and after enameling. The enameled and unenameled samples were tested using the ring-on-ring (ROR) and ball-on-ring (BOR) strength tests. The strengths of each sample set were analyzed using a conventional two-parameter Weibull analysis. For direct comparison of the data, combined Weibull moduli were calculated for the unenameled tin side, unenameled air side, and enameled tin side data sets. The principle of independent action (PIA) was assumed to be the appropriate fracture criterion and the data were scaled to determine if discrepancies existed between the different testing methodologies. The scale parameters (σo) were also calculated for the different test geometries. The results showed that there were no statistical differences between the scaled data. Based on the results it was concluded that the ROR test geometry was the better choice compared to the BOR test geometry because of the larger stressed area. The use of a concentric support ring was also found to be more desirable than a ring on equally spaced balls because of the stress concentrations at the support balls, which can lead to problems.

Dynamic tensile-splitting experiments were conducted on brittle polyester disks, manufactured from Homalite ®-100, to photoelastically visualize stress field development in the specimens and, ultimately, specimen fracture. A Split Hopkinson Pressure Bar (SHPB) was used to load the specimen dynamically and record load data as a function of time. Images of the stress field were captured with high-speed photography and interpreted using photoelastic analysis. The experiments determined that the specimens reached an equilibrium state relatively quickly, and remained in equilibrium until fracture. Fracture began with in-plane cracks forming on either side of the specimen. Transverse cracks emanated from the in-plane cracks, then propagated across the specimen mid-plane at velocities up to 60% of the shear wave velocity in the material. Contact loads calculated from photoelasticity agreed favorably with SHPB results. These experiments also allowed for the determination of the dynamic splitting strength of the Homalite ®-100 as a function of strain rate. The dynamic splitting strength of the material increased with the increasing strain rate, reaching a maximum value of about twice the static splitting strength.

Regression analyses were performed to study the correlation between the permanent deformation characteristics of hot mix asphalt (HMA) mixtures and their aggregate geometric irregularities. Permanent deformation of HMA mixtures was characterized by permanent strain, creep modulus, and slope of the creep curve from unconfined repeated load deformation tests. The fine aggregate angularity (FAA) test was used to characterize fine aggregates while coarse aggregates were characterized with either the particle index (PI) test, the modified National Aggregate Association flow test (modified NAA), or image analysis. Regression analyses indicate strong correlation between the permanent deformation characteristics of HMA mixtures and the aggregate geometric irregularities. Use of imaging indices for characterizing coarse aggregates gives better coefficients of determination than do other coarse aggregate characteristics such as PI and modified NAA. The imaging indices have major potential in evaluating aggregate geometric irregularities for engineering analysis.

The round double beam loaded in eccentric compression has been shown to produce usable data when determining the fracture properties of materials with a relatively large characteristic length. In order to reduce these data, the geometry calibration factor must be known for the combination of specimen geometry and loading technique. Numerical simulations using the boundary element method have been used to determine the geometry calibration factor for a round double beam with a length to diameter ratio of 2:1 loaded in eccentric compression. The factor was determined by compliance calibration and direct calculation of stress intensities. Recognizing that laboratory test specimens will not have exactly the same geometry as the simulated specimen, geometry calibration factors have been determined for variations in the base geometry as well.

Asphalt binders used in asphalt concrete roadway pavements experience aging during construction and subsequently during their service lives. Aging is the combined effect of the evaporation of volatile compounds and the chemical reaction of residual compounds with oxygen. This aging affects the rheological properties of asphalt binders. The SuperpaveTM testing and specification system uses two laboratory procedures for aging of binders prior to measuring their rheological properties, namely the rolling thin film oven (RTFO) and the pressure aging vessel (PAV). These two procedures are used to simulate the aging that takes place during construction and during service, respectively. This paper examines whether the SuperpaveTM prescribed sequence of binder aging procedures (i.e., the RTFO followed by the PAV) is necessary, or whether similar binder rheological properties are obtained using the PAV procedure only. For this purpose, three binders were tested, namely an unmodified PG 64-28, an SBS polymer-modified binder of the same grade, and an SBS polymer-modified PG 76-28. The low temperature and fatigue rheological properties were measured by a bending beam rheometer (BBR) and a dynamic shear rheometer (DSR), respectively. The findings of the study suggest that, with a few exceptions, the rheological properties measured after aging with the RTFO followed by PAV are significantly different than those obtained after PAV aging only.

The fatigue strength and the fracture mechanisms of ion-nitrided steel were investigated using three types of specimens-annealed specimens, nitrided specimens, and specimens from which the surface layer was removed (surface-removed specimens). The latter specimens' surface layers were removed after nitriding, reducing their radius by 0.1 mm. The fatigue limit of the nitrided specimens was higher than that of the annealed specimens, but was almost the same as that of the surface-removed specimens. This is related to the hardness distribution of the specimens. In the case of the nitrided specimen, the maximum hardness was recorded at the surface and decreased gradually toward the center of the specimen. The estimated strength deduced from the hardness of that specimen is higher than the measured fatigue limit within a depth of 0.1 mm from the surface. At internal depths of more than 0.1 mm from the surface, the estimated strength is expected to be lower than the fatigue limit. Accordingly, the fatigue limit and strength of the nitrided specimens are determined by the internal properties of the materials, and thus the fatigue limit and strength of the nitrided specimens are not decreased even if the surface layer is removed. In the case of the nitrided specimens, the cracks were difficult to observe from the surface because the crack initiations occurred internally. Since removing the surface layers facilitates observing the cracks on the surface, the initiation mechanism of internal cracking can be evaluated by observing surface crack initiation. In the case of the surface-removed specimens, many cracks initiated and propagated along the needle-shaped precipitates of Fe 4 N and finally these cracks coalesced with each other. From the observation of the fracture surfaces, a similar mechanism is assumed to be operating internally in the nitrided specimens.

Tribological behavior of surfaces can be enhanced significantly by the presence of very small scale (nanometric) surface textures. Indirect surface texturing is a recently developed process by which a surface texture can be produced through differential wear of the constituents of a bimaterial surface. To enable rapid and low-cost investigation of material pairs that may be used to form such bimaterial surfaces, a specimen and test procedure have been developed and are described in this paper. The specimen allows the extremes of behavior that can be experienced during use of an indirectly textured surface to be assessed. The procedure is demonstrated using steel and titanium carbide (TiC) bimaterial samples that are found to develop a surface step, corresponding to texture development on a treated surface, even following extreme wear by grinding.

Components of commercial nuclear reactors are subjected to neutron bombardments that can modify their mechanical properties. Prediction of in-service and post-service behaviors generally requires irradiation in so-called “test reactors” as well as subsequent mechanical testing in specialized hot cell facilities. However, the use of these research facilities is becoming more problematic, in particular due to increasing costs and decreasing availability. One way of partially mitigating these problems is to complement the empirical approach by developing tools for numerical simulation of irradiation effects in materials. The development of such tools is clearly an ambitious task that will require a long-term international collaborative effort. In this paper, we present an outline of the Reactor for Virtual Experiments (REVE) project, a collaborative European and American effort aimed at developing quantitative simulations of irradiation effects in materials. The first demonstration phase of REVE will target embrittlement of reactor pressure vessel (RPV) steels, since the effects and mechanisms of irradiation damage in this material are relatively well understood and many modeling tools have been developed or are under development in this field. As for any experiment, the input variables of the REVE simulation will be the neutron spectrum, time and temperature of irradiation, the alloy composition (e.g., Cu, Ni, Mn, and C contents) and microstructure and the unirradiated mechanical properties. The simulations will predict the irradiation-induced increases of yield stress and Charpy transition temperature as well as the decrease of toughness due to the concomitant evolution of the microstructure.

The influence of the material parameters, strain hardening, and strain-rate hardening on the plastic instability of textured zinc sheets tested in uniaxial tension was investigated. The experimental instability strains are observed to be in accord with those evaluated from the analytical expressions involving the material parameters. The crystallite orientation distribution function obtained from the pole figure data is used in conjunction with a plasticity model to predict the anisotropy parameters (R and P) and subsequently the width strains in longitudinal and transverse zinc sheets. While the experimental R and P values matched well with those predicted for basal slip, the predicted width strains beyond uniform deformation are observed to be higher than the experimental values.

This paper introduces a staged compression-immersion-direct shear test carried out in order to deal with compressive settlement phenomena of compacted crushed mudstone during staged filling and due to immersion from the viewpoints of not only deformation but also shear strength deterioration. The test apparatus and procedure are described, and as an example, compacted crushed Kobe mudstone samples are tested. It is shown that as expected, the crushed Kobe mudstone samples compacted with 95% degree of compaction exhibit larger compressive settlement than those compacted with 100% degree of compaction during staged loading, and that only the former samples show additional compression due to immersion. Shear strength decreases due to immersion being accompanied with volume decrease, and the shear strength decrease and volume change are larger in the samples compacted with 95% degree of compaction. It is also indicative that the shear strength of the aggregate itself has a significant influence on the shear strength of its compacted samples.

A numerical investigation of sharp indentation of thin films and ribbons has been conducted using the finite element method. For a wide variety of material behavior, the critical ratio of indentation depth to thin film thickness is determined for the case of indentation of thin films or ribbons perfectly clamped on hard substrates. The critical ratio is defined as the ratio at which the indentation response can no longer be considered closely acceptable to the corresponding response at indentation of bulk materials. The indentation parameters investigated are hardness (average contact pressure), the size of the contact area between indenter and material, and the initial unloading slope of the indentation load-indentation depth curve. The implications of the results for material characterization of thin films and ribbons by indentation are discussed in some detail.

The round double beam loaded in tension, RDB(T), or wedging, RDB(W), is part of standard test methods for measuring the fracture toughness of aluminum (ASTM E 1307), cemented carbides (ASTM B 644), and rock. When the combination RDB(T) or RDB(W) is used with materials with a relatively large characteristic length, which is defined as the square of the ratio of fracture toughness to tensile strength, the crack tends to depart from the intended fracture plane rendering the data unusable. Loading the RDB in eccentric compression, RDB(B), has been investigated as an acceptable loading alternative in such cases. Tests of over 100 RDB(B) specimens made from different concrete mixtures using three specimen sizes all produced usable data. In addition, the fracture toughness values obtained from RDB(B) tests are consistent with values obtained from RDB(W) tests. The test equipment, test procedures, and data reduction method are all described in detail for the RDB(B).

An instrumental attachment and testing method was developed on a QTest™ tensile tester to evaluate leather compressibility. Six types of leather including pig, deer, cow, emu, goat, and alligator, were tested in terms of compressive modulus, linearity, energy, resilience, and thickness. A linear function was proposed to characterize the relationship between logarithmic stress and strain. This enabled calculation of all initial compressive moduli for these leather samples. The instrumental obtained data helped comparison of the compressive properties among the leather samples.

Modifications need to be made to standard test procedures to determine the actual properties of thin-walled ductile iron castings. A series of experiments was performed on test bars to examine the effects of surface finish, elongation measurement techniques, and the amount of material removed during grinding. A paired t-test was used to show that strength and ductility increased as a result of removing the as-received (as-cast) surface. This is attributed to inaccuracies in measuring the cross section area of the rough surface as well as an actual increase in strain through removal of surface effects. A nontraditional method of measuring elongation (to retain the fracture surface) was compared to the standard ASTM method. The nontraditional method was found to be a conservative measure of elongation that is highly correlated with plastic strain as measured by the stress-strain curve. The amount of surface removed during grinding was found not to affect the mechanical properties with the exception of hardness, a surface measurement. It is suggested that thin-walled castings be tested in the condition the casting will be used, i.e., if the casting will be used with the as-cast surface, testing with the as cast surface will accurately reproduce the decrease in strain caused by the surface effects. If the casting will be ground before use, any amount of surface can be removed to make the testing convenient.