Showing papers on "Ultimate tensile strength published in 1993"
TL;DR: In this paper, the properties of nylon 6-clay hybrids, such as molecular composites of nylon and silicate layers of montmorillonite and saponite, NCH's and NCHP's, respectively, have been synthesized.
Abstract: Various nylon 6-clay hybrids, such as molecular composites of nylon 6 and silicate layers of montmorillonite and saponite, NCH's and NCHP's, respectively, have been synthesized. To estimate the mechanical properties of these hybrids, tensile, flexural, impact, and heat distortion tests were carried out. NCH was found superior in strength and modulus and comparable in impact strength to nylon 6. The heat distortion temperature (HDT) of NCH (montmorillonite: 4.7 wt. %) was 152 °C, which was 87 °C higher than that of nylon 6. In NCHP, saponite had a smaller effect on the increase of these mechanical properties. The modulus and HDT of NCH and NCHP increased with an increase in the amount of clay minerals. It was found that these properties were well described by the contribution of the constrained region calculated from the storage and loss modulus at the glass transition temperature. According to the mixing law on elastic modulus, the following expression was obtained between the modulus E at 120 °C and the fraction of the constrained region C, En = Ecn = C, where the values of n and Ec (modulus of the constrained region) were 0.685 and 1.02 GPa, respectively.
2,492 citations
TL;DR: In this paper, the authors examined strength and toughness properties of concrete in which different amounts of rubber-tire particles of several sizes were used as aggregate, and the concrete mixtures exhibited lower compressive and splitting-tensile strength than did normal concrete.
Abstract: Accumulations of worn‐out automobile tires create fire and health hazards. As a possible solution to the problem of scrap‐tire disposal, an experimental study was conducted to examine the potential of using tire chips and crumb rubber as aggregate in portland‐cement concrete. This paper examines strength and toughness properties of concrete in which different amounts of rubber‐tire particles of several sizes were used as aggregate. The concrete mixtures exhibited lower compressive and splitting‐tensile strength than did normal concrete. However, these mixtures did not demonstrate brittle failure, but rather a ductile, plastic failure, and had the ability to absorb a large amount of plastic energy under compressive and tensile loads. A mathematical model is used to describe the effects of rubber aggregate on the compressive and tensile strength reduction of concrete.
680 citations
TL;DR: The variations in mechanical properties around the equine radius, which occur in close association with the different collagen fibre orientations, provide maximal safety factors in terms of ultimate stress, yet contribute to greater bending of the bone as it is loaded during locomotion, and thus lower safety factors through the higher strains this engenders.
Abstract: Mechanical test specimens were prepared from the cranial and caudal cortices of radii from eight horses. These were subjected to destructive tests in either tension or compression. The ultimate stress, elastic modulus and energy absorbed to failure were calculated in either mode of loading. Analysis was performed on the specimens following mechanical testing to determine their density, mineral content, mineral density distribution and histological type. A novel technique was applied to sections from each specimen to quantify the predominant collagen fibre orientation of the bone near the plane of fracture. The collagen map for each bone studied was in agreement with the previously observed pattern of longitudinal orientation in the cranial cortex and more oblique to transverse collagen in the caudal cortex. Bone from the cranial cortex had a significantly higher ultimate tensile stress (UTS) than that from the caudal cortex (160 MPa vs 104 MPa; P < 0.001) though this trend was reversed in compression, the caudal cortex becoming relatively stronger (185 MPa vs 217 MPa; P < 0.01). Bone from the cranial cortex was significantly stiffer than that from the caudal cortex both in tension (22 GPa vs 15 GPa; P < 0.001) and compression (19 GPa vs 15 GPa; P < 0.01). Of all the histo-compositional variables studied, collagen fibre orientation was most closely correlated with mechanical properties, accounting for 71% of variation in ultimate tensile stress and 58% of variation in the elastic modulus. Mineral density and porosity were the only other variables to show any significant correlation with either UTS or elastic modulus. The variations in mechanical properties around the equine radius, which occur in close association with the different collagen fibre orientations, provide maximal safety factors in terms of ultimate stress, yet contribute to greater bending of the bone as it is loaded during locomotion, and thus lower safety factors through the higher strains this engenders.
180 citations
TL;DR: In this paper, the buckling and rotation techniques are used to measure tensile and compressive strain in polysilicon thin-film structures, which can be easily measured using an array with different beam lengths.
Abstract: New stress-measurement devices for measuring both tensile and compressive strain in single structures have been realized. The investigation is concentrated on the development of two techniques: (i) buckling and (ii) rotation. The buckling technique is based on the buckling of a beam when exceeding a critical strain level. Therefore, an array with different beam lengths is required. The rotation technique, on the other hand, converts the extension or contraction of the material into a rotation, which can be easily measured. These structures have been modelled, simulated, and tested experimentally, using thin polysilicon films. Both techniques have been shown to be promising methods for simple and accurate on-chip thin-film strain measurements.
176 citations
TL;DR: In this paper, the authors measured the Butt tensile strength of a joint that bonds two stainless steel rods together with an unfilled epoxy adhesive (Epon 828/T-403).
170 citations
Journal Article•
TL;DR: The information obtained from microscopical studies of fractured surfaces indicates that some adhesives may, under optimal conditions, obtain a bond strength sufficient to fracture the dentine.
169 citations
TL;DR: In this paper, the authors showed that collagen fibres do not need to be continuous to reinforce the annulus fibrosus, and that 15mm-wide samples of annulus retain about 44% of their in situ stiffness and strength when stretched vertically.
Abstract: Part I of this study showed that collagen fibres do need not need to be continuous to reinforce the annulus fibrosus, and that 15-mm-wide samples of annulus retain about 44% of their in situ stiffness and strength when stretched vertically. Part II investigated the ultimate tensile strength (UTS) and fatigue life of such samples. Vertical slices, 5 mm thick and 30 mm wide, were cut from the anterior and posterior margins of the annulus and adjacent vertebral bodies. Each slice was divided sagittally to obtain a matched pair of specimens. The bony ends of each specimen were secured in a materials testing machine so that the annulus could be stretched vertically, as occurs during bending movements of the spine in life. One of each pair of specimens was stretched to failure to obtain its UTS; the other was cyclically loaded at some fraction of the UTS until failure occurred. Tensile failure started with the hyaline cartilage end-plate being stripped off the underlying bone and ended with the most peripheral annular fibres pulling out of the matrix. The estimated in situ strength in the vertical direction was 3.9 MPa for the anterior annulus and 8.6 MPa for the posterior annulus. Fatigue failure could occur in less than 10000 cycles if the tensile force exceeded 45% of the UTS. The results explain why radial fissures often fail to penetrate the peripheral annulus. When compared with in vivo measurements of spinal loading, they suggest that repetitive forward bending movements could cause fatigue failure of the posterior annulus.
167 citations
TL;DR: It was deduced that the variation of failure mode of 200 microns-HAC with time could not be accounted for by the attack of body fluid alone; the degradation must be a synergetic adverse result of residual stress in the HAC and the attack in body fluid.
Abstract: Plasma-sprayed hydroxyapatite coated (HAC) 50 and 200 microns thick on Ti-6Al-4V cylinders was transcortically implanted in the femora of canines to evaluate in detail the effect of coating thickness on the pushout shear strength and failure mode examined under scanning electron microscope after the periods of 4, 6, 8, and 12 weeks. The HAC coating exhibited higher shear strength at 50 microns than at 200 microns. Its failure mode was conclusively at or near the HAC-bone interface, and the slight attack of body fluid had not degraded the implant to the extent that failure occurred at the HAC-Ti alloy interface after 12 weeks of observation. For 200 microns-HAC, failure was found at the HAC-bond interface, inside the HAC lamellar splat layer and at the HAC-Ti alloy substrate interface, depending on the period of implantation. It was also deduced that the variation of failure mode of 200 microns-HAC with time could not be accounted for by the attack of body fluid alone; the degradation must be a synergetic adverse result of residual stress in the HAC and the attack of body fluid.
167 citations
TL;DR: The results imply that if no stress is applied to the autograft in the case of augmentative reconstruction of the knee ligament, the graft strength decreases remarkably.
Abstract: Mechanical properties of the stress-shielded patellar tendon were studied in the rabbit knee. Stress shielding was accomplished by stretching a stainless-steel wire installed between the patella and tibial tubercle and thus, releasing the tension in the patellar tendon completely. Tensile tests were carried out on the specimens obtained from the patellar tendons which were exposed to the stress shielding for 1 to 6 weeks. The stress shielding changed the mechanical properties of the patellar tendon significantly: it decreased the tangent modulus and tensile strength to 9 percent of the control values after 3 weeks. There was a 131 percent increase in the cross-sectional area and a 15 percent decrease in the tendinous length. Remarkable changes were also observed in the structural properties: for example, the maximum load of the bone-tendon complex decreased to 20 percent of the control value after 3 weeks. Histological studies showed that the stress shielding increased the number of fibroblasts and decreased the longitudinally aligned collagen bundles. These results imply that if no stress is applied to the autograft in the case of augmentative reconstruction of the knee ligament, the graft strength decreases remarkably.
164 citations
TL;DR: In this article, the influence of cyclic loading frequency on the tensile fatigue life of a woven-carbon-fiber/SiC-matrix composite was examined at room temperature.
Abstract: The influence of cyclic loading frequency on the tensile fatigue life of a woven-carbon-fiber/SiC-matrix composite was examined at room temperature. Tension-tension fatigue experiments were conducted under load control, at sinusoidal frequencies of 1, 10, and 50 Hz. Using a stress ratio ([sigma][sub min]/[sigma][sub max]) of 0.1, specimens were subjected to maximum fatigue stresses of 310 to 405 MPa. There were two key findings: (1) the fatigue life and extent of modulus decay were influenced by loading frequency and (2) the post-fatigue monotonic tensile strength increased after fatigue loading. For loading frequencies of 1 and 10 Hz, the fatigue limit (defined at 1 [times] 10[sup 6] cycles) was approximately 335 MPa, which is over 80% of the initial monotonic strength of the composite; at 50 Hz, the fatigue limit was below 310 MPa. During 1- and 10-Hz fatigue at a maximum stress of 335 MPa, the modulus exhibited an initially rapid decrease, followed by a partial recovery; at 50 Hz, and the same stress limits, the modulus exhibited an initially rapid decrease, followed by a partial recovery; at 50 Hz, and the same stress limits, the modulus continually decayed. The residual strength of the composite increased by approximately 20% after 1more » [times] 10[sup 6] fatigue cycles at 1 or 10 Hz under a peak stress of 335 MPa. The increase in strength is attributed in part to a decrease in the stress concentrations present near the crossover points of the 0[degree] and 90[degree] fiber bundles.« less
149 citations
TL;DR: In this article, the impact properties of Fibre Metal Laminates in comparison with other high-performance aerospace structural materials are investigated. But the results demonstrate the superior behaviour of GLARE 3 compared with the other materials.
TL;DR: In this paper, Young's modulus, 73 GPa, Poisson's ratio, 0.25, tensile strength, −14 MPa, unconfined compressive strength, 262 MPa; fracture toughness, 1-3 MPa m½ cohesion, 66 MPa.
Abstract: Laboratory measurements of rock deformation in the brittle regime provide constraints on the response of rocks to stress. These values are essential parameters in tectonic models of near-surface deformation because they influence both the stress state and the conditions for predicting the types and occurrences of brittle structures such as joints and faults. However, additional parameters must be included before the laboratory values can be used to construct brittle strength envelopes for near-surface materials. The properties of basaltic rock masses provide a more precise estimate of the strengths of basaltic lava flows on the terrestrial planets than other, more widely used approaches (intact rock or frictional strength of a through-going surface). Rock mass strength is defined by three parameters including unconfined compressive strength of intact basalt and two others related to the degree of fracturing of the material. Experimental results for elevated temperature extend the applicability of these parameters to the near-surface environment of Venus. Representative values of strength parameters for intact basalt at ambient temperature (20°C)and negligible confining pressure are: Young's modulus, 73 GPa; Poisson's ratio, 0.25; tensile strength, −14 MPa; unconfined compressive strength, 262 MPa; fracture toughness, 1–3 MPa m½ cohesion, 66 MPa; and coefficient of friction, 0.6. At elevated temperature (∼450°C) and zero confining pressure, reference values for the strength of intact basalt are: Young's modulus, 57 GPa; Poisson's ratio, 0.25; unconfined compressive strength, 210 MPa; and fracture toughness, 2–2.8 MPa m½. Corresponding values for a basaltic rock mass that incorporate the weakening effects of scale (but not elevated temperature) are: Deformation modulus, 5–50 GPa; Poisson's ratio, 0.3; tensile strength, −0.2 to −2 MPa; uniaxial compressive strength, 12–63 MPa; cohesion, 0.5–6 MPa. Values of tensile and cohesive strength for the basaltic rock mass are approximately one to two orders of magnitude lower than corresponding values for intact basalt. Temperatures comparable to those at the Venus surface may slightly increase the deformation modulus but decrease the compressive strength of the rock mass. Brittle strength envelopes for the rock mass as a function of depth are typically stronger in both extension and compression than conventional envelopes that assume a simple frictional strength. These results indicate that the strengths of basaltic rocks on planetary surfaces and in the shallow subsurface are significantly different from strength values commonly used in tectonic modeling studies which assume properties of either intact rock samples or single planar shear surfaces.
TL;DR: In this paper, a shape memory TiNi fiber reinforced/Al metal matrix composite (SM-MMC) was proposed to improve the tensile properties such as stiffness and yield strength.
Abstract: A design concept of shape memory TiNi fiber reinforced/Al metal matrix composite (SM-MMC) was proposed. Mechanical tensile properties such as stiffness and yield strength, were improved by the strengthening mechanisms: back stress in the Al matrix induced by stiffness of TiNi fibers and the compressive stress in the matrix caused by shape memory shrinkage of TiNi fibers. Damping capacity of the composite was also increased. These results suggest that this composite with prestrain can be applicable and is suitable for machinery, especially engine components where the material becomes stronger at higher temperatures owing to the shape memory effect
TL;DR: In this paper, the effect of compatibilization of blends of polypropylene (PP) with a thermotropic liquid-crystalline polymer (LCP) was considered in an attempt to improve the mechanical properties obtained by blending alone.
TL;DR: In this article, the effect of randomly distributed fiber reinforcement on the response of cemented sand to load was evaluated in triaxial static compression, cyclic compression, and splitting tension tests.
Abstract: Triaxial static compression, cyclic compression, and splitting tension tests were performed to evaluate the effect of randomly distributed fiber reinforcement on the response of cemented sand to load. Test results indicated that fiber reinforcement significantly increases the compressive and splitting tensile strength of cemented sand. An increase in the compressive and tensile strength was found to be more pronounced at higher fiber contents and longer fiber lengths. Peak strength envelopes in compression indicated that both the friction angle and cohesion intercept of cemented sand were increased as a result of fiber inclusion. Inclusion of fibers also contributed to increased brittleness index of cemented sand while increasing its total energy absorption capacity. Fiber reinforcement also affected the response of cemented sand to cyclic load by significantly increasing the number of cycles, and the magnitude of cyclic strain needed to reach failure.
TL;DR: In this paper, a method of measuring the mechanical strength of thin films is described, where miniature arrays of four tensile specimens, each 0.25 mm wide, 1 mm long, and 2.2 μm thick, are prepared using deposition, patterning, and etching processes common to the semiconductor industry.
Abstract: A new method of measuring the mechanical strength of thin films is described. We prepare miniature arrays of four tensile specimens, each 0.25 mm wide, 1 mm long, and 2.2 μm thick, using deposition, patterning, and etching processes common to the semiconductor industry. Each array of four specimens is carried on and protected by a rectangular silicon frame. Thirty-six such specimens are produced on a single wafer. After a specimen frame is mounted, its vertical sides are severed without damaging the specimens. The load is applied by micrometers through a special tension spring. Tensile properties of a 2.2 μm thick Ti–Al–Ti film were determined.
TL;DR: Low-d diameter, dehydrothermal-cyanamide crosslinked fibers have greater tensile strength and a more rapid degradation rate than medium-diameter, glutaraldehyde cross linked fibers, and are therefore more suitable for use in a degradable ligament reconstruction device.
Abstract: Collagen fibers used in a scaffolding device for ligament reconstruction must be thin, strong, and degradable. The purpose of this study was to determine the effects of fiber diameter (20, 50, or 90 microns), crosslinking agent (uncrosslinked, dehydrothermal-cyanamide, or glutaraldehyde), and hydration on the initial mechanical properties, biocompatibility, and subcutaneous degradation rates of fibers extruded from an acidic dispersion of insoluble type I collagen. The wet tensile strength of extruded collagen fibers was significantly improved by decreasing the fiber diameter. Low-diameter, crosslinked fibers had wet tensile strengths ranging from 75-110 MPa. In contrast, high diameter fibers had wet strength values of about 30 MPa. The degradation rate of the implanted fibers, in contrast, was not significantly prolonged by changing the initial fiber diameter. This result is important because prolonged degradation of the fibers can lead to implant encapsulation instead of neoligament formation. By minimizing the diameter, fiber strength can be increased without prolonging the fiber degradation rate. Low-diameter, dehydrothermal-cyanamide crosslinked fibers have greater tensile strength and a more rapid degradation rate than medium-diameter, glutaraldehyde crosslinked fibers, and are therefore more suitable for use in a degradable ligament reconstruction device.
TL;DR: In this paper, a simple geometrical model is proposed to predict the failure strain as a function of the reinforcement content, aspect ratio and strain to failure of the unreinforced matrix.
Abstract: The formation of cavities in commercially pure aluminium composites, made by both powder and casting routes and reinforced with alumina (short fibres, angular particles and spherical particles), has been monitored using periodic density measurements during tensile testing and microstructural examinations. Stable cavities always form well before final failure, usually adjacent to the reinforcement, particularly when it is elongated in the loading direction and has a relatively flat surface normal to the stress axis. Sharp corners are not favoured cavitation sites and cavities can form at spherical particles, although the incidence is somewhat less than for angular particles. Cavitation occurred earlier for higher reinforcement contents and with powder-route, as opposed to cast, material, although the void contents and composite strains at failure were similar. A simple geometrical model is proposed, allowing prediction of the failure strain as a function of the reinforcement content, aspect ratio and strain to failure of the unreinforced matrix. The data presented are in good agreement with predictions from this model.
TL;DR: In this paper, a high-speed framing camera was used to record the gross deformation and cracking during the fracture process in split tensile concrete specimens at strain rates of 10 to the power -7/sec to 10 to power 2/sec in a low speed material test machine and in a 50.8mm diameter Split Hopkinson Pressure Bar (SHPB).
Abstract: Splitting tensile concrete specimens were tested at strain rates of 10 to the power -7/sec to 10 to the power 2/sec in a low speed material test machine and in a 50.8-mm diameter Split Hopkinson Pressure Bar (SHPB). A comprehensive finite element method (FEM) analysis was conducted on the same test speciments. A high-speed framing camera was used to record the gross deformation and cracking during the fracture process in the SHPB tests. In addition, an ultra high speed image converter camera with equivalent framing rates of 10,000 to 1,000,000 frames per sec was used to record some of the early crack formations during the fracture process in the SHPB tests. Results of tensile strength versus strain rate are presented and compared with compressive strength at similar strain rates. These same tensile data are compared with strength data obtained using a fracture mechanics model. Computer generated crack patterns are presented and compared to experimentally observed crack patterns in the fracture of concrete at high strain rates.
TL;DR: In this paper, the authors studied tensile instabilities for an elastic-plastic bar with rectangular cross-section, using a full three-dimensional numerical analysis, based on the simplest flow theory of plasticity, but also the effect of yield surface curvature and the effect on ductile failure mechanisms are considered in a few computations.
Journal Article•
TL;DR: It can be concluded that in the 21st century the ultrafine compact-filled composite resins may be the materials of choice for restoring posterior cavities.
Abstract: Human enamel and dentin should be used as the physiologic standards with which to compare composite resins, especially in the posterior region. The intrinsic surface roughness of composite resins must be equal to or lower than the surface roughness of human enamel on enamel-to-enamel occlusal contact areas (Ra = 0.64 microns). Roughness determines the biologic strength of composite resins. The nanoindentation hardness value of the filler particles (2.91 to 8.84 GPa) must not be higher than that of the hydroxyapatite crystals of human enamel (3.39 GPa). Composite resins intended for posterior use should have a Young's modulus at least equal to, and preferably higher than, that of dentin (18.500 MPa). The compressive strength of enamel (384 MPa) and dentin (297 MPa) and the fracture strength of a natural tooth (molar = 305 MPa; premolar = 248 MPa) offer excellent mechanical standards to select the optimal strength for posterior composite resins. The in vivo occlusal contact area wear rate of composite resins must be comparable to the attritional enamel wear rate (about 39 microns/y) in molars. Differential wear between enamel and composite resin on the same tooth is a new criterion for visualizing and quantifying the wear resistance of composite resins in a biologic way. Posterior resins must have a radiographic opacity that is slightly in excess of that of human enamel (198% Al). Based on these standard criteria, it can be concluded that in the 21st century the ultrafine compact-filled composite resins may be the materials of choice for restoring posterior cavities.
TL;DR: In this paper, the authors investigated the microstructure of tungsten thin films by cross-sectional transmission electron microscopy and showed that high-pressure conditions resulted in dendritic-like film growth, which brought about complete relaxation of internal stresses.
Abstract: Tungsten thin films were deposited on glass substrates by direct‐current planar magnetron sputtering. The induced thickness‐averaged film stress within the plane of the film was determined with the bending‐beam technique and changed from compressive to tensile on increasing working‐gas pressure. The microstructure of these films was investigated by cross‐sectional transmission electron microscopy. Compressively stressed films consisted of tightly packed columnar grains, whereas in films with a maximum value for the tensile stress the onset of a void network surrounding the columnar grains was observed. High‐pressure conditions resulted in dendritic‐like film growth, which brought about complete relaxation of internal stresses. The α phase was predominantly found in films under compression, while an increasing amount of β‐W coincided with the transition to the tensile stress regime. Special attention was focused on stress‐depth dependence and the development of two overlapping line profiles in x‐ray diffra...
TL;DR: In this article, the effect of plant age on tensile strength, tensile modulus and toughness of sisal fibre became very much less at 100 °C as compared to 30 °C.
Abstract: Sisal fibres extracted from the leaves of Agava sisalana plants 3, 5, 7 and 9 years old were tested at different temperatures for tensile strength, elongation, toughness and modulus. The tensile strength, modulus and toughness values of sisal fibre decreased with increase in temperature. The effect of plant age on tensile strength, tensile modulus and toughness of sisal fibre became very much less at 100 °C as compared to 30 °C. Fractured fibres were observed by using a scanning electron microscope. The ends of fibres fractured at elevated temperature showed a failure similar to that of inorganic fibres. Elongation values at all temperatures increased with age. Elongated capillaries were observed in fibres fractured at 80 and 100 °C, due to the removal of moisture and volatiles originally present in the fibres. The fibrils are clearly observed in the form of hollow cylinders. Fractured surfaces are composed of brittle as well as ductile phases. The ductile portion increased with the increase of temperature.
TL;DR: In this article, a modified laser spallation technique for measuring the tensile strength of planar interfaces, using a Doppler displacement interferometer, is presented. But the method is limited to planar surfaces.
Abstract: Part I of this paper presents the modified laser spallation technique for measuring the tensile strength of planar interfaces, using a Doppler displacement interferometer. In this technique, a laser‐produced compressive stress pulse in the substrate, reflecting from the coating’s free surface pulls the interface in tension and leads to its failure if the tensile amplitude is high enough. The current technique is an improvement over the previous one, since the interface stress is determined directly by recording the coating or substrate free‐surface velocities using a laser displacement interferometer. The recorded surface velocity is related to the interface stress via an elastic wave equation simulation. The process of coating spallation is investigated, and the effect of the stress pulse profile and the coating and substrate characteristics on the interface tensile stress is studied using the simulation. Several interface stress charts are given for wider applicability of the modified technique.
TL;DR: The current knowledge on the microstructure, sintering and creep properties of the nanostructured oxides TiO 2, Y 2 o 3 and zRo 2 synthesized by gas condensation is summarized in this article.
TL;DR: In this article, the tensile strength of interfaces between 3-μm-thick coatings of Sn, Sb, Cu, Nb, Al, and Cr on a PG substrate was measured in units of MPa to be 18.53, 5.99, 15.46, 41.16, 16.53 and 15.47, respectively.
Abstract: Part II of this series presents applications of the modified laser spallation technique to several interface systems. For metal/pyrolytic graphite (PG) interfaces, the tensile strength of interfaces between 3‐μm‐thick coatings of Sn, Sb, Cu, Nb, Al, and Cr on a PG substrate were measured in units of MPa to be 18.53, 5.99, 15.46, 41.16, 16.53, and 15.47, respectively. It was found that the interface fracture mechanisms depend on the elastic‐plastic properties of the coatings, but are independent of the interface strength. Interface strength between diamond, SnO2, and Nb coatings on polycrystalline alumina substrates were measured to be ≳140, 320, and 280 MPa, respectively. It is shown that the brittle fracture takes place at the interface upon spalling even if the plastic deformation exists within the coatings.
TL;DR: In this paper, three-dimensional impact experiments were conducted on 20 cm-sized blocks of Bedford limestone and San Marcos gabbro and the resulting tensile stresses in the range of ∼11 to 160 MPa were employed to induce dynamic tensile failure in Bedford limestone.
Abstract: Planar impact experiments were employed to induce dynamic tensile failure in Bedford limestone. Rock discs were impacted with aluminum and polymethyl methacralate flyer plates at velocities of 10 to 25 m/s. This resulted in tensile stresses in the range of ∼11 to 160 MPa. Tensile stress durations of 0.5 and 1.3 μs induced microcrack growth which in many experiments were insufficient to cause complete spalling of the samples. Ultrasonic P and S wave velocities of recovered targets were compared to the velocities prior to impact. Velocity reduction, and by inference microcrack production, occurred in samples subjected to stresses above 35 MPa in the 1.3-μs PMMA experiments and 60 MPa in the 0.5-μs aluminum experiments. Apparent fracture toughnesses of 2.4 and 2.5 MPa m^(1/2) are computed for the 1.3- and 0.5-μs experiments. These are a factor of ∼2 to 6 greater than quasi-static determinations. Three-dimensional impact experiments were conducted on 20 cm-sized blocks of Bedford limestone and San Marcos gabbro. Compressional wave velocity deficits up to 50–60% were observed in the vicinity of the crater. These damage levels correspond to O'Connell and Budiansky damage parameters of 0.4 as compared to the unshocked rock. The damage decreases as ∼r^(−1.5) from the crater indicating a dependence on the magnitude and duration of the tensile pulse. Using the observed variation in damage with tensile stress from the one-dimensional experiments, and estimates of the variation of peak dynamic tensile stress and tensile stress duration with distance from an impact on an elastic half-space, the observed dependence of damage with radius in the three-dimensional experiments are theoretically predicted and compare favorably to experimental data.
TL;DR: In this paper, the authors used multilinear regression analysis for initial prediction of the elastic and plastic strain amplitudes at 10 6 and 10 4 reversals to failure respectively from uniaxial tensile data.
TL;DR: In this article, the effect of relative humidity and temperature on tensile strength of two types of protein-based [corn zein (CZ) and wheat gluten (WG)] and two kinds of cellulosic [methylcellulose (MC) and hydroxypropyl cellulose (HPC)] hydrophilic edible films was investigated.
Abstract: The effect of relative humidity and temperature on tensile strength of two types of protein-based [corn zein (CZ) and wheat gluten (WG)] and two types of cellulosic [methylcellulose (MC) and hydroxypropyl cellulose (HPC)] hydrophilic edible films was investigated. A central composite response surface design was used. Studied ranges of relative humidity and temperature were 23 to 75% and 5 to 45° C, respectively. For all four types of films, tensile strength (TS) decreased with relative humidity and increased with temperature. Ranges of mean tensile strength values among the nine different combinations of the two variables were 5.7 to 23.6 MPa, 2.7 to 21.4 MPa, 61.9 to 104.4 MPa, and 11.1 to 35.0 MPa for CZ, WG, MC, and HPC, respectively. A second-order polynomial model was fitted to the data with least squares regression. A regression model linear in relative humidity and quadratic in temperature showed a very good fit to tensile strength data of CZ (R2 = 0.93) and MC (R2 = 0.98) films. A regression equation linear with respect to both relative humidity and temperature satisfactorily fitted (R2 = 0.75) TS data of HPC films. A best fitted model for TS data of WG films, that included relative humidity and temperature, the square of temperature, and the cross-product of the two variables, had a poor fit (R2 = 0.67).
TL;DR: In this article, a progressive failure model for tensile loading is extended for laminated composites under uniaxial compressive loading, which is capable of predicting the extent of failure.
Abstract: A progressive failure model that was developed earlier for tensile loading is extended for laminated composites under uniaxial compressive loading. This model is capable of predicting the extent of...