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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.

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.

ISTA Procedure 2C and two options in NMFCC Item 181, stacked vibration and compression and vibration in separate tests, were compared to determine the equivalency of common U.S. furniture packaging performance tests. Containers constructed of two different corrugated fiberboard specifications were evaluated; Box A: a 32 lb/in. (5.6 kN/m) ECT rated board with a basis weight combination of 35HP/26/35HP, and Box B: a 200 psi (1378.95 kPa) Mullen rated board with a basis weight combination of 42/26/42. Ten corrugated fiberboard containers of each board type were tested following each of the test protocols. After testing, the contents were removed and the residual compression force at failure and deflection at failure of the containers were measured. These data were compared to the compression force and deflection at failure of control samples for the two board grades tested. Results showed that Item 181 Method A produced significantly different residual compression force at failure when compared to Item 181 Method B and Procedure 2C for both boxes. Item 181 Method B and Procedure 2C were not significantly different. Also, the two boxes showed significantly different residual compression force at failure results for each of the test protocols studied. The percent change in compression force at failure based on control samples, however, was not significantly different between the boxes studied.

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.

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 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.

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.

Thermal output from two different strain gage types was analyzed over a temperature range from 20–500°C. The influence of applied loads was also examined. The strain gages were attached to the specimens in three different configurations. Thermal output was efficiently compensated for using a quarter-bridge configuration. Relative large errors were found using half-bridge configurations. The obtained thermal output values, with and without application of load, are discussed.

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.

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.

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.

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.

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.

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.

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.

The influence of aging of four cosmetic formulations on the mechanical properties of plastic packaging is studied. Four thermoplastic materials in the form of bottles were used: polyethylene, polypropylene, polyethylene terephthalate, and polyethylene terephthalate glycol copolymer. Bottles were filled with cosmetic formulations and put into a steam room at 42°C for 15 days, 1 month, 2 months, and 3 months. Periodically, bottles were emptied, and mechanical properties and performances (tensile test, compression, and under-pressure tests) were studied as well as the wall thickness, the glass transition temperature (Tg), the crystallinity, and the kinetic sorption by Fourier transform infrared spectrometry. A significant change of mechanical properties was observed after the sorption of cosmetic components into the materials: this change depending on the type of material (especially for polyethylene and polypropylene) and on the cosmetic formulation. These changes must be minimized, particularly in the light of reducing packaging weight. This work leads to a new optimization methodology permitting the anticipation of packaging design.

Effects of the number and spacing between staples on withdrawal and lateral resistance of stapled joints were investigated for selected wood and wood-based materials. Galvanized staples with legs that were 1.59 mm in diameter (16-gage wire) and 38 mm (1.5-in.) in length, and had chisel-end points, were used to construct the joints. Spacings between staples of 3.18 mm (1/8-in.) and 6.35 mm(1/4-in.) were tested. One, two, four, or eight staples were used to fasten the joint members that were of the following materials: Eastern cottonwood (Populus deltoides), red oak (Quercus falcata), yellow poplar (Liriodendron tulipifera), sweetgum (Liquidambar styraciflua), medium density fiberboard (MDF), and oriented strandboard (OSB). Direct withdrawal and lateral resistances of the joints were evaluated. Results indicated that, on the average, joints with higher density members provided the most resistance to withdrawal and lateral loads. Number of staples positively affected the joint resistance for all materials for both spacings, however, the relationship was not linear for most materials. General linear regression models, using material type and spacing as indicator variables, were developed to predict the withdrawal and lateral resistances.

To develop guidelines for using C-ring specimens for evaluating the fracture strength of ceramics in tubular form, a series of finite-element analysis (FEA) calculations was performed. These calculations focused on the ranges of specimen dimensions and loading distributions required to maintain a uniaxial stress state within the C-ring specimen under diametral loading. Results of the FEA calculations indicated that the degree of uniaxiality of the C-ring stress state could be described completely by a combination of the width-to-thickness ratio (b/t) and the inner radius-to-outer radius ratio (ri/ro). It was also found that a reasonably wide range of geometries can be used with accuracy to extract fracture strength design data, provided b/t does not get too large or ri/ro too low. Given the potential statistical distribution of flaws in most ceramics, there is also cause for concern when b/t → 0 or ri/ro → 1 as this implies a small sample of flaws in the critical tensile stress region. Calculations also indicated that the uniaxiality of the C-ring stress state followed the expected 1/v dependence so that the behaviors of different materials can be surmised easily from the current results calculated for v = 0.155. As expected, and in contrast to O-ring specimens, the loading distribution between the C-ring surface and platum do not seem to have any effect on the stress state.

Center hole tension specimens with similar shapes but different sizes were tested under constant and variable amplitude loads. Fatigue degradation due to burrs was found to be small and/or negligible for relatively large holes with diameters such as 10 and 5 mm, but was marked for smaller holes with diameters of 2 and 1 mm. Finite-element analysis shows that peak stress at a semicircular arc-shaped burr increases as the hole becomes smaller, if the same thickness and the same heights of the burrs are assumed. It is indicated that careful deburring is particularly necessary for small holes to prevent fatigue degradation.

Tube hydroforming has been receiving increasing attention, particularly for making automotive components. In this process, tubular metal pats are formed within a die cavity by forcing pressurized fluid inside so that the part expands into its final shape in a die. Process control requires an improved knowledge of mechanical properties in the transverse direction of tubular products. Several laboratory tests have been used to evaluate tube properties. One test method that has been used for zirconium alloy cladding tubes in the nuclear industry is the ring test, in which an expansion force is applied from inside the ring by separating two die inserts. In the present work, this test method is adapted to determine the hoop stress-strain curve of tubular materials. The new protocol allows measurement of the tensile properties without altering those properties in specimen preparation, which occurs using the conventional flattened strip tensile test. This paper presents the new test and data analysis procedure, along with typical data for a commercial steel hydroforming tube.

This study presents experiments and analytical methods to capture and quantify the directional and spatial aggregate distributions in hot mix asphalt (HMA). The quantifying parameters were obtained by processing and analyzing images of HMA sections. An experimental technique in which HMA sections were treated with hydrofluoric acid was developed in order to improve the contrast between aggregates and asphalt prior to capturing an image. The developed methods were used to analyze the aggregate distribution in mixes compacted in the laboratory using the Superpave gyratory compactor (SGC) under different compaction variables, and in the field using different compaction patterns. The field cores exhibited similar aggregate distributions irrespective of the compaction pattern, whereas the angle of gyration and specimen height in the SGC were found to influence significantly the aggregate distribution. Laboratory specimens compacted to a height close to that of field cores, and using an angle of gyration of 1.25°, were better in simulating the aggregate distribution in the field.

An apparatus in the direct shear mode has been developed to conduct soil-soil and soil-solid material interface tests in the undrained condition. Evaluation of the apparatus showed that all the requirements for simulating the undrained condition of shear are satisfied. The interface test results show that the adhesion factor α increases with the surface roughness of the solid material. In the case of the normally consolidated state, α is practically independent of the undrained shear strength of the clay for a given surface. For the overconsolidated state, α depends on the undrained shear strength and the overconsolidation ratio for smooth surfaces but for rough surfaces, α is independent of both undrained shear strength and overconsolidation ratio.

In this study, a series of bearing capacity tests were carried out on a model ground composed of aluminum rods in order to investigate the initiation and development of shear bands during loading. This paper describes the test apparatus, the methods of testing and data treatment, and some of the test results. Two types of model grounds were prepared depending upon whether the aluminum rods used were single-diameter or two different diameters. During the loading test, by utilizing both front and back of the test apparatus, detailed observations were made on the global deformation of the model ground, on the translational and rotational movements of selected aluminum rods, and on the change of void ratio. It is shown that, in the case of the single-diameter aluminum rods, the slip surface was observed and that dilatancy behavior was noted at the boundary. In the case of the aluminum rods with two different diameters, discontinuous shear bands defining a so-called plastic flow zone were observed, which were initiated at the bottom corners of the footing and extended diagonally downwards. The rotational behavior of the rods differed inside and outside the plastic flow zone, particularly near the boundaries.

Gaskets based on polytetrafluoroethylene (PTFE) are used extensively in bolted flanged connections, especially in difficult chemical process plant applications where blowouts due to excessive bolt load loss are of major concem. The determination of their service temperatures requires the characterization of their short- and long-term creep relaxation resistance. An experiment-alanalytical procedure has been developed to determine a recommended service temperature for PTFE-based gaskets. Based on an improved version of the Hot Blowout Test (HOBT) in which thermal cycling has been incorporated, the procedure quantifies the short-term hot relaxation resistance, and the margin of safety against an in-service blowout. The improved HOBT test provides an excellent tool for the selection of blowout-resistant PTFE gaskets for difficult service. Currently, the procedure estimates the cooldown load loss due to the thermal contraction difference between the gasket and the flange, based on a rough estimate of the gasket thickness and the coefficient of thermal expansion and their vanation with temperature. The proposed procedure provides not only a better estimation of the gasket thickness but also accounts for thermal ratcheting and the temperature lag between flange and bolts.

Polyvinyl chloride (PVC) pipes were weathered naturally for periods of up to two years. The effect of weathering on the mechanical properties was investigated by compressing unnotched and radially notched ring specimens in a parallel-plate test. Disregarding the scatter existing among the test results, the general trend indicates deteriorating fracture properties due to exposure. The application of fracture mechanics concepts, explicitly the J-integral value, to the test results helps to reveal the susceptibility of weathered PVC pipe material to brittle fracture compared to its as-received condition.

Manufacturing operations such as die cutting and slitting of sheet materials result in wear of the tooling. A new method for measuring the abrasive properties of paper and other sheet materials is proposed. The method continuously monitors the force required for penetrating a sheet sample as multiple punches are made with a needle. Abrasive wear caused by the sheet sample changes the geometry of the needle, and consequently changes the penetration force. The trend of the force is used as a measure of the abrasivity of the sheet sample. Several sheet paper samples were tested using this method with two different needle geometries. In all cases, the magnitude of the force decreased with an increasing number of punches. The rate of change of force depends on the type of paper and the initial geometry of the needle.

Use of the single-edge precracked beam (SEPB) specimen with the “bridge indentation” method is one of the new ASTM standard test methods for the determination of fracture toughness of advanced ceramics. In support of this effort, the effects of several test parameters on the fracture toughness values were established. The effects of the residual stress due to the indent, the alignment in three- and four-point bending, and the crack front straightness on the fracture toughness values were determined using aluminum nitride specimens. The results show that indent loads should be kept below 100 N (10 kg), and the crack plane angle should be less than 5° in order to prevent artificially high fracture toughness values. Crack front straightness requirements can be less stringent than generally accepted.

An empirical expression for computing the dynamic yield stress, σyd, from the general yield load, PGY, of dynamic tear (DT) specimens has been derived by comparing the results from instrumented drop-weight/impact tests of DT and Charpy V-notch (CVN) specimens of AISI 308 weld and AISI 316 stainless steels. This is based on the following assumptions: the functional expression relating σyd to PGY is the same for both DT and CVN specimens except for a dimensionless proportionality constant: and σyd from both the specimens has the same value. Plastic η-factors obtained by analyzing instrumented DT test results are also presented. The work reported earlier by the authors based on instrumented CVN and precracked Charpy specimen test results showed the dependence of the plastic η-factor on the crack aspect ratio; the present results indicate that the plastic η-factor shows an additional specimen size dependence. However, the new estimates based on the larger size specimens are only slightly larger than the lower-bound estimates reported earlier, but much below the upper-bound curve reported at the same place. Similar size dependence has been reported in the literature.

The present paper reports the accuracy of the J estimation equations for three typical homogeneous fracture toughness testing specimens: M(T), C(T), and SE(B) specimens, based on systematic 2D FE analyses. A wide range of crack lengths is considered, except for C(T) specimens where only deep cracks are considered, a/W = 0.45 to 0.7. By carefully selecting the properties of the materials in the analysis, particular emphasis is placed on the sensitivity of such equations to the strain hardening as well as the type of stress strain curve, such as continuously hardening materials or materials with Luders strain. Two different J estimation schemes are considered, one based on load-load line displacement records and the other on load-crack mouth opening displacement (CMOD) records. For all cases considered, the J estimation based on load-CMOD records gives more accurate results, compared to those based on load-load line displacement records. Moreover, the J estimation is not sensitive to the material's strain hardening and to the type of the stress strain curve, except for shallow-cracked M(T) specimens with a/W

Iosipescu specimens were developed to examine the shear properties of isotropic materials. In the past decade, there has been much effort made to analyze this specimen configuration for measuring anisotropic materials, particularly laminated and woven composites. Some authors have used notch angles ranging from 90 to 110° in these materials and other authors have performed finite element analysis (FEA) to determine the notch angle and depth with the most uniform shear stress zone based on the elastic moduli. The object of this study was to verify the preferred angle of woven fiber composites through the use of stress pattern analysis by thermal emission (SPATE), which is a technique that can image the hydrostatic stress state in a material under load. SPATE images were collected for various specimens at different notch angles (90, 100, and 110°) and different weave lay ups. Mean load was held constant while the SPATE image was collected but later increased to examine the stress state of the Iosipescu specimens at high loads. The results indicate that for a plain woven carbon fiber/epoxy resin composite, the 100° notched specimen is the best specimen of the three conditions examined due to the delay in occurrence of damage and the large size of the pure shear zone.

In the present paper, the effect of a skew insert in a double-cantilever beam specimen in evaluating Mode I delamination fracture energy (GIc) of unidirectional laminated composites is investigated numerically. A delamination growth analysis incorporating the finite element method is utilized to calculate variation of load-displacement-delamination length for a prescribed GIc as delamination propagates along the specimen. In order to evaluate the values of GIc as a function of delamination length, the calculated data were treated as experimental data and processed using two ASTM standard test data reduction methods. These are the modified beam theory and the compliance calibration methods. It is found that the skew front moves progressively to form a thumb-nail curved front during a few millimeters of growth. Part of this growth occurs within the specimen, not visible from the specimen edges where the delamination lengths were recorded during a test. It also is found that the difference between delamination lengths measured at each side of the specimen can have a significant effect on the calculated GIc. To eliminate this error in an actual test, it is suggested that the larger delamination length be used for data processing.

The growth of cracks is related to the existence of a plastic zone at the crack tip, the formation and growth of which are accompanied by an energy dissipation. The estimation of this energy is generally made by global measures. In our study, we have used microhardness measurements at the crack tip for estimating energy. The results obtained are more accurate near the crack tip than those estimated by other methods.

The test method detailed in ASTM Standard Test Method for Shear Testing of Thin Aluminum Sheet Alloy Products (B 831) approximates the conditions of pure shear. The newly proposed test regime removes the rigid body rotation associated with pure shear and hence creates a simple shear deformation. The test also makes available an additional volume of empirical data by facilitating the measurement of both shear stress and strain throughout the test. The proposed test procedure was used to analyze the directionality of simple shear deformation in an aerospace 2024-T3 aluminum alloy. The shear yield strength determined using the newly proposed method was found to be approximately half of the uniaxial yield strength. The orthotropic response in shear was seen to differ from that exhibited during uniaxial testing. The stress-strain response in simple shear also illustrated the effect of the deformation restrictions through the appearance of serrated yielding.