Showing papers on "Strain rate published in 2014"
1,265 citations
TL;DR: The Global Strain Rate Model (GSRM v.2.1) as mentioned in this paper is a new global model of plate motions and strain rates in plate boundary zones constrained by horizontal geodetic velocities.
Abstract: We present a new global model of plate motions and strain rates in plate boundary zones constrained by horizontal geodetic velocities. This Global Strain Rate Model (GSRM v.2.1) is a vast improvement over its predecessor both in terms of amount of data input as in an increase in spatial model resolution by factor of ∼2.5 in areas with dense data coverage. We determined 6739 velocities from time series of (mostly) continuous GPS measurements; i.e., by far the largest global velocity solution to date. We transformed 15,772 velocities from 233 (mostly) published studies onto our core solution to obtain 22,511 velocities in the same reference frame. Care is taken to not use velocities from stations (or time periods) that are affected by transient phenomena; i.e., this data set consists of velocities best representing the interseismic plate velocity. About 14% of the Earth is allowed to deform in 145,086 deforming grid cells (0.25° longitude by 0.2° latitude in dimension). The remainder of the Earth's surface is modeled as rigid spherical caps representing 50 tectonic plates. For 36 plates we present new GPS-derived angular velocities. For all the plates that can be compared with the most recent geologic plate motion model, we find that the difference in angular velocity is significant. The rigid-body rotations are used as boundary conditions in the strain rate calculations. The strain rate field is modeled using the Haines and Holt method, which uses splines to obtain an self-consistent interpolated velocity gradient tensor field, from which strain rates, vorticity rates, and expected velocities are derived. We also present expected faulting orientations in areas with significant vorticity, and update the no-net rotation reference frame associated with our global velocity gradient field. Finally, we present a global map of recurrence times for Mw=7.5 characteristic earthquakes.
608 citations
TL;DR: In this article, a split Hopkinson pressure bar testing system is used in conjunction with a load inversion device to perform the high strain rate tension experiments on flat smooth, notched and central hole tensile specimens extracted from advanced high strength steel sheets.
285 citations
TL;DR: In this paper, the steady state flow behavior of the FeCoNiCrMn high-entropy alloy at temperatures ranging from 1023 to 1123 K was systematically characterized, and it was found that the stress exponent (i.e., the reciprocal of strain-rate sensitivity) was dependent on the applied strain rate.
260 citations
03 Jan 2014-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the authors investigated the hot compressive deformation behaviors of a typical Ni-based superalloy over wide ranges of forming temperature and strain rate and developed processing maps to optimize the hot working processing.
Abstract: The hot compressive deformation behaviors of a typical Ni-based superalloy are investigated over wide ranges of forming temperature and strain rate. Based on the experimental data, the efficiencies of power dissipation and instability parameters are evaluated and processing maps are developed to optimize the hot working processing. The microstructures of the studied Ni-based superalloy are analyzed to correlate with the processing maps. It can be found that the flow stress is sensitive to the forming temperature and strain rate. With the increase of forming temperature or the decrease of strain rate, the flow stress significantly decreases. The changes of instability domains may be related to the adiabatic shear bands and the evolution of δ phase(Ni 3 Nb) during the hot formation. Three optimum hot deformation domains for different forming processes (ingot cogging, conventional die forging and isothermal die forging) are identified, which are validated by the microstructural features and adiabatic shear bands. The optimum window for the ingot cogging processing is identified as the temperature range of 1010–1040 °C and strain rate range of 0.1–1 s −1 . The temperature range of 980–1040 °C and strain rate range of 0.01–0.1 s −1 can be selected for the conventional die forging. Additionally, the optimum hot working domain for the isothermal die forging is 1010–1040 °C and near/below 0.001 s −1 .
221 citations
TL;DR: In this paper, a two-stage constitutive model was developed to predict the flow stress of a typical nickel-based superalloy with high forming temperature and low strain rate.
208 citations
TL;DR: In this article, the time-resolved strain and temperature profiles of magnetron-sputtered pseudoelastic TiNi films of 20μm thickness were investigated during tensile stress cycling for different strain rates.
200 citations
TL;DR: In this paper, a triaxial unloading test was conducted on twenty-seven marble specimens with initial confining pressures of 20, 30 and 40 MPa and unloading rates of 0.1, 1.0 and 10 MPa/s.
190 citations
TL;DR: In this paper, the effects of grain size on the rate-dependent thermomechanical responses of polycrystalline superelastic NiTi (with an average grain size from 10 to 90nm) under both monotonic and cyclic tensile loading-unloading were investigated.
183 citations
TL;DR: In this article, the authors investigated the high-temperature deformation behaviors of a typical Ni-based superalloy under the strain rate of 0.001-1.s−1 and temperature of 920-1040°C.
160 citations
TL;DR: In this paper, the hot tensile deformation behaviors and fracture characteristics of a typical Ni-based superalloy are studied by uniaxial tensile tests under the deformation temperature range of 920-1040°C and strain rate range of 0.01-0.001 s −1.
TL;DR: This work quantifies the connection between rate dependent mechanical behavior and kinetics of breaking and reattachment of temporary cross-links in a three-dimensional finite strain constitutive model using a physically based and quantitatively predicted model.
Abstract: Recent experiments have shown that hydrogels with enhanced toughness can be synthesized by incorporating self-healing physical cross-links in a chemically cross-linked gel network. These gels exhibit rate dependent mechanical behavior, suggesting that improved mechanical properties are closely tied to the breaking and reattaching of temporary cross-links in the gel network. In this work, the connection between rate dependent mechanical behavior and kinetics of breaking and reattachment of temporary cross-links is quantified using a three-dimensional finite strain constitutive model. The parameters of the model are fitted using relaxation and constant strain rate tests in uniaxial tension of a model dual-cross-link gel. The stress versus time curves of more complex strain histories, involving loading followed by unloading at different rates, is successfully and quantitatively predicted by our model. Such modeling strategy combining physically based kinetics and three-dimensional large strain mechanics shows great promise for quantitative modeling of soft biological tissues and synthetic counterparts containing dynamic bonds.
TL;DR: A microstructural model of the axonal cytoskeleton is presented to quantitatively elucidate the interaction between microtubules and tau proteins under mechanical loading and identifies a characteristic length scale for load transfer that depends on microStructural properties.
TL;DR: In this paper, the authors used four constitutive models, namely, Johnson-Cook, Fields-Backofen (FB), Khan-Huang-Liang (KHL), and Mechanical Threshold Stress (MTS), to predict the flow behavior of Ti-6Al-4V alloy sheet.
TL;DR: In this paper, a power law with high apparent stress exponents of 6−13 and high apparent activation energies of 510−680 kJ/kJ/mol−1 was derived.
TL;DR: In this article, a constitutive model is proposed to predict the stress-strain response of an AA5xxx alloy over the studied strain rate and temperature ranges, and the developed model is also calibrated for another AA5754-O, to evaluate the capability of a developed model in capturing transition from negative to positive strain rate sensitivity.
TL;DR: The results show diminished bone toughness at increasing strain rates as cracks penetrate through the osteons at higher strain rates instead of deflecting at the cement lines, which is a prime toughening mechanism in bone at low strain rates.
TL;DR: In this paper, the effect of strain rate (in the domain of 0.001 to 10 s−1) on dynamic recrystallization (DRX) kinetics in a nitrogen-enhanced 316L(N) stainless steel during high temperature [≥1123k (≥850k)] deformation is reported.
Abstract: In this paper, the effect of strain rate (in the domain of 0.001 to 10 s−1) on dynamic recrystallization (DRX) kinetics in a nitrogen-enhanced 316L(N) austenitic stainless steel during high temperature [≥1123 K (≥850 °C)] deformation is reported. In the low strain rate domain (i.e., <0.1 s−1), the DRX is predominantly governed by higher growth of DRX grains resulting in a higher DRX fraction and larger DRX grain size. On the other hand, DRX at higher strain rates (i.e., ≥1 s−1) is mainly controlled by higher nucleation resulting in higher DRX fraction with a finer grain size. In the intermediate strain rate regime of 0.1 s−1, sluggish kinetics of DRX is observed since neither the nucleation nor the growth of DRX grains is predominant. The annealing twinning event, which may accelerates the DRX kinetics, is also observed to occur more frequently during the low and high strain rate deformations.
TL;DR: In this article, an artificial neural network (ANN) model was developed to predict the flow stress of a Ti600 titanium alloy by a Gleeble 1500D thermo-mechanical test simulator over the temperature range from 760 to 920 °C and strain rate range from 0.01 to 10 ǫ s −1.
TL;DR: In this article, the effects of deformation temperature and strain rate on the hot tensile deformation behaviors and fracture characteristics are discussed in detail, and the Arrhenius-type constitutive model is developed to predict the peak stress under the tested deformation condition.
TL;DR: In this paper, the tensile fracture behavior of the Ti-6Al-4V alloy was examined with scanning electron microscope (SEM) over the range of magnifications.
TL;DR: In this article, the effect of temperature and strain rate on tensile properties of hexagonal boron nitride (h-BN) nanosheets has been investigated.
Abstract: The effect of temperature and strain rate on mechanical properties remains an open topic in research of hexagonal boron nitride (h-BN) nanosheets. To examine these fundamental issues we have performed molecular dynamics simulations to record the stress–strain curves in tensile tests and measure Young's modulus, fracture strength and fracture strain in armchair and zigzag directions. Comparing the results obtained at different temperatures and strain rates we have quantified the effects of the two factors on the tensile properties of the h-BN nanosheets. The influence of crystal orientation is also examined in the present study. It is found that the h-BN nanosheets are basically an anisotropic material whose tensile properties vary substantially with temperature and strain rate. In particular, a yielding platform is observed for the h-BN nanomaterial at relatively low temperature.
TL;DR: In this article, a scenario describing SIC was proposed, assuming that SIC corresponds to the successive appearance of crystallite populations whose nucleation and growth depend on the local network density.
Abstract: Strain-induced crystallization (SIC) of natural rubber (NR) is characterized during a cyclic deformation at room temperature and low strain rate (∼10–3 s–1) using in situ wide angle X-rays scattering (WAXS) measurements. The crystallinity index (CI) and average size of the crystallites in the three main directions are measured during loading and unloading. A scenario describing SIC is then proposed, assuming that SIC corresponds to the successive appearance of crystallite populations whose nucleation and growth depend on the local network density. From this scenario, a methodology, coupling experimental observations and thermodynamic description is developed to determine the distribution of the network chain density associated with the size of a corresponding crystallite population. Finally, complex cyclic tests are performed. They suggest the existence of a memory effect in the chains involved in crystallization, which eases the nucleation process of the crystallites.
26 Mar 2014-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the hot deformation behavior of superaustenitic stainless steel S32654 was studied in the temperature range of 950-1200°C and strain rate range of 0.001-10−s −1 employing hot compression tests.
Abstract: The hot deformation behavior of superaustenitic stainless steel S32654 was studied in the temperature range of 950–1200 °C and strain rate range of 0.001–10 s −1 employing hot compression tests. The results show that peak stress increases with decreasing of temperature and increasing of strain rate. The apparent activation energy of this alloy is about 469 kJ/mol. The processing maps for hot working were developed on the basis of flow stress data and the dynamic materials model. It is found that the features of the maps obtained in the strain range of 0.2–1.0 are fundamentally similar, indicating that the strain does not have a significant influence on processing map. The maps exhibited two domains. The first domain occurs in the strain rate range of 0.01–0.4 s −1 and temperature range of 1030–1150 °C with a peak efficiency of about 49%, which is considered as the optimum window for hot working. The microstructure observations of the specimens deformed in this domain showed the full dynamic recrystallization (DRX) structure with finer and more homogeneous grain sizes. The second domain occurs at the temperatures higher than 1160 °C and strain rates lower than 0.1 s −1 with a peak efficiency of about 41%, the microstructure observations in this domain also indicated the typical DRX structure accompanied with grain growth. A instability domain occurs at temperatures below 1175 °C and strain rate above 0.1 s −1 .
TL;DR: In this article, the authors investigate the mechanical properties of silicene under uniaxial tensile deformation by using molecular dynamics simulations, and they find that the fracture strength and fracture strain of silicon are much higher than those of bulk silicon.
Abstract: Silicene, a graphene-like two-dimensional silicon, has attracted great attention due to its fascinating electronic properties similar to graphene and its compatibility with existing semiconducting technology. So far, the effects of temperature and strain rate on its mechanical properties remain unexplored. We investigate the mechanical properties of silicene under uniaxial tensile deformation by using molecular dynamics simulations. We find that the fracture strength and fracture strain of silicene are much higher than those of bulk silicon, though the Young's modulus of silicene is lower than that of bulk silicon. An increase in temperature decreases the fracture strength and fracture strain of silicene significantly, while an increase in strain rate enhances them slightly. The fracture process of silicene is also studied and brittle fracture behavior is observed in the simulations.
TL;DR: In this paper, the mechanical properties of Iβ crystalline cellulose were studied using molecular dynamics simulation, and the deformation and failure modes associated with these properties and the relationships between the material's response to tension and the evolution of the crystal structure were analyzed.
Abstract: The mechanical properties of Iβ crystalline cellulose are studied using molecular dynamics simulation. A model Iβ crystal is deformed in the three orthogonal directions at three different strain rates. The stress–strain behaviors for each case are analyzed and then used to calculate mechanical properties. The results show that the elastic modulus, Poisson’s ratio, yield stress and strain, and ultimate stress and strain are highly anisotropic. In addition, while the properties that describe the elastic behavior of the material are independent of strain rate, the yield and ultimate properties increase with increasing strain rate. The deformation and failure modes associated with these properties and the relationships between the material’s response to tension and the evolution of the crystal structure are analyzed.
TL;DR: The constitutive response of a commercial magnesium alloy rolled sheet (AZ31B-O) is studied based on room temperature tensile and compressive tests at strain rates ranging from 10−3 to 103 s−1 to capture the rate sensitivity of the sigmoidal stress–strain response.
Abstract: The constitutive response of a commercial magnesium alloy rolled sheet (AZ31B-O) is studied based on room temperature tensile and compressive tests at strain rates ranging from 10 −3 to 10 3 s −1 . Because of its strong basal texture, this alloy exhibits a significant tension–compression asymmetry (strength differential) that is manifest further in terms of rather different strain rate sensitivity under tensile versus compressive loading. Under tensile loading, this alloy exhibits conventional positive strain rate sensitivity. Under compressive loading, the flow stress is initially rate insensitive until twinning is exhausted after which slip processes are activated, and conventional rate sensitivity is recovered. The material exhibits rather mild in-plane anisotropy in terms of strength, but strong transverse anisotropy ( r -value), and a high degree of variation in the measured r -values along the different sheet orientations which is indicative of a higher degree of anisotropy than that observed based solely upon the variation in stresses. This rather complex behaviour is attributed to the strong basal texture, and the different deformation mechanisms being activated as the orientation and sign of applied loading are varied. A new constitutive equation is proposed to model the measured compressive behaviour that captures the rate sensitivity of the sigmoidal stress–strain response. The measured tensile stress–strain response is fit to the Zerilli–Armstrong hcp material model.
TL;DR: In this paper, an extensive literature review identifies the deformation parameters important to weld strength: interface strain, strain rate, normal contact stress, temperature and shear, and the film theory of bonding is used to derive a model that quantifies the relevance of these parameters to the weld strength.
TL;DR: In this paper, a model of concurrent lithiation and rate-sensitive plasticity is developed for amorphous LixSi thin films, and the results have direct ramifications concerning the rate-capabilities of silicon electrodes: faster charging rates (i.e., strain rates) result in larger stresses and hence larger driving forces for fracture.
TL;DR: In this article, the dynamic recovery was the main softening mechanism along with the dynamic recrystallization in the local area within the deformation temperature range of 300-450°C and strain rate range of 0.01-10−s−1.