Showing papers on "Slip (materials science) published in 2014"
TL;DR: In this paper, the influence of changes in crystallographic texture on the Hall-Petch (H-P) relationship for an Mg alloy was investigated, and the texture variations were facilitated by changing the uniaxial tensile loading orientation with respect to the normal direction of the rolled Mg plate.
294 citations
TL;DR: A fully printed fingerprint-like three-axis tactile force and temperature sensor for artificial skin applications and strain engineering enables the strain distribution to be detected upon applying a slip/friction force is demonstrated.
Abstract: A three-axis tactile force sensor that determines the touch and slip/friction force may advance artificial skin and robotic applications by fully imitating human skin. The ability to detect slip/friction and tactile forces simultaneously allows unknown objects to be held in robotic applications. However, the functionalities of flexible devices have been limited to a tactile force in one direction due to difficulties fabricating devices on flexible substrates. Here we demonstrate a fully printed fingerprint-like three-axis tactile force and temperature sensor for artificial skin applications. To achieve economic macroscale devices, these sensors are fabricated and integrated using only printing methods. Strain engineering enables the strain distribution to be detected upon applying a slip/friction force. By reading the strain difference at four integrated force sensors for a pixel, both the tactile and slip/friction forces can be analyzed simultaneously. As a proof of concept, the high sensitivity and selectivity for both force and temperature are demonstrated using a 3×3 array artificial skin that senses tactile, slip/friction, and temperature. Multifunctional sensing components for a flexible device are important advances for both practical applications and basic research in flexible electronics.
258 citations
TL;DR: In this article, the effect of slip transfer on heterogeneous deformation of polycrystals has been a topic of recurring interest, as this process can either lead to the nucleation of damage, or prevent nucleations of damage.
Abstract: The effect of slip transfer on heterogeneous deformation of polycrystals has been a topic of recurring interest, as this process can either lead to the nucleation of damage, or prevent nucleation of damage. This paper examines recent experimental characterization of slip transfer in tantalum, TiAl, and Ti alloys. The methods used to analyze and assess evidence for the occurrence of slip transfer are discussed. Comparisons between a characterized and simulated patch of microstructure are used to illustrate synergy that leads to new insights that cannot arise with either approach alone.
251 citations
TL;DR: The interaction between slip bands and grain boundaries in commercial-purity titanium was examined using cross-correlation-based electron backscatter diffraction in this article, where three types of interactions were observed: blocked slip band with stress concentration, slip transfer, and no stress concentration.
249 citations
TL;DR: In this article, the behavior of the nanofluid was investigated for three different nanoparticles in the water-base fluid, namely copper, alumina and titania, and it was shown that a dual solution exists for negative values of the unsteadiness parameter A and, as it increases, the skin friction Cfr grows but the heat transfer rate Nur takes a decreasing trend.
212 citations
TL;DR: In this paper, a modified two-component four-equation nonhomogeneous equilibrium model was employed for nanofluids, which fully accounted for the effect of the nanoparticle volume fraction distribution.
204 citations
TL;DR: In this paper, the reliability of infinite slopes in the presence of spatially variable shear strength parameters that increase linearly with depth was studied and the results indicated that the mean trend of the shears strength parameters has a significant influence on clay slope reliability.
189 citations
TL;DR: The agreement between model and data across numerous independent measures provides evidence for slip avalanches of STZs as the elementary mechanism of inhomogeneous deformation in metallic glasses.
Abstract: For the first time in metallic glasses, we extract both the exponents and scaling functions that describe the nature, statistics, and dynamics of slip events during slow deformation, according to a simple mean field model We model the slips as avalanches of rearrangements of atoms in coupled shear transformation zones (STZs) Using high temporal resolution measurements, we find the predicted, different statistics and dynamics for small and large slips thereby excluding self-organized criticality The agreement between model and data across numerous independent measures provides evidence for slip avalanches of STZs as the elementary mechanism of inhomogeneous deformation in metallic glasses
188 citations
TL;DR: It is found that smooth megathrusts that produce great earthquakes tend to be weaker and therefore dissipate less heat than geometrically rough megath Rusts that slip mainly by creeping.
Abstract: Subduction faults, called megathrusts, can generate large and hazardous earthquakes. The mode of slip and seismicity of a megathrust is controlled by the structural complexity of the fault zone. However, the relative strength of a megathrust based on the mode of slip is far from clear. The fault strength affects surface heat flow by frictional heating during slip. We model heat-flow data for a number of subduction zones to determine the fault strength. We find that smooth megathrusts that produce great earthquakes tend to be weaker and therefore dissipate less heat than geometrically rough megathrusts that slip mainly by creeping.
178 citations
TL;DR: Molecular dynamics simulation results show that hydrodynamics applies in this circumstance, even at length scales down to nanometers, however, corrections to the slip boundary condition and apparent viscosity of nanoconfined flow must be included to make quantitative predictions.
Abstract: Fast slip flow was identified for water inside the interlayer gallery between graphene layers or carbon nanotubes. We report here that this significant flow rate enhancement (over two orders) breaks down with the presence of chemical functionalization and relaxation of nanoconfinement in graphene oxides. Molecular dynamics simulation results show that hydrodynamics applies in this circumstance, even at length scales down to nanometers. However, corrections to the slip boundary condition and apparent viscosity of nanoconfined flow must be included to make quantitative predictions. These results were discussed with the structural characteristics of liquid water and hydrogen-bond networks.
174 citations
TL;DR: Comprehensive seismic data from subduction zone forearcs exhibiting recurring slow earthquakes is compiled and it is shown that the average ratio of compressional (P)-wave velocity to shear (S-wave velocity) of the overlying forearc crust ranges between 1.6 and 2.0 and is linearly related to the average recurrence time of slow earthquakes.
Abstract: Seismic data from subduction zones that exhibit slow earthquakes reveal that the ratio of compressional-wave to shear-wave velocity of the overriding forearc crust is linearly related to the average recurrence time of slow earthquakes and that this may be associated with quartz enrichment within the forearc crust. Pascal Audet and Roland Burgmann present a compilation of seismic data from subduction zones that exhibit recurring slow earthquakes, and show that the ratio of compressional- to shear-wave seismic velocity (vP/vS) of the overlying forearc crust is linearly related to the average recurrence time of slow earthquakes. They propose that variable silica enrichment from slab-derived fluids and upward mineralization in quartz veins can explain the range of observed vP/vS values, and that the strong temperature dependence of healing and permeability reduction in silica-rich fault gouge can explain the reduction in tremor recurrence time with progressive silica enrichment. Seismic and geodetic observations in subduction zone forearcs indicate that slow earthquakes, including episodic tremor and slip, recur at intervals of less than six months to more than two years1,2. In Cascadia, slow slip is segmented along strike3 and tremor data show a gradation from large, infrequent slip episodes to small, frequent slip events with increasing depth of the plate interface4. Observations5,6,7 and models8,9 of slow slip and tremor require the presence of near-lithostatic pore-fluid pressures in slow-earthquake source regions; however, direct evidence of factors controlling the variability in recurrence times is elusive. Here we compile seismic data from subduction zone forearcs exhibiting recurring slow earthquakes and show that the average ratio of compressional (P)-wave velocity to shear (S)-wave velocity (vP/vS) of the overlying forearc crust ranges between 1.6 and 2.0 and is linearly related to the average recurrence time of slow earthquakes. In northern Cascadia, forearc vP/vS values decrease with increasing depth of the plate interface and with decreasing tremor-episode recurrence intervals. Low vP/vS values require a large addition of quartz in a mostly mafic forearc environment10,11. We propose that silica enrichment varying from 5 per cent to 15 per cent by volume from slab-derived fluids and upward mineralization in quartz veins12 can explain the range of observed vP/vS values as well as the downdip decrease in vP/vS. The solubility of silica depends on temperature13, and deposition prevails near the base of the forearc crust11. We further propose that the strong temperature dependence of healing and permeability reduction in silica-rich fault gouge via dissolution–precipitation creep14 can explain the reduction in tremor recurrence time with progressive silica enrichment. Lower gouge permeability at higher temperatures leads to faster fluid overpressure development and low effective fault-normal stress, and therefore shorter recurrence times. Our results also agree with numerical models of slip stabilization under fault zone dilatancy strengthening15 caused by decreasing fluid pressure as pore space increases. This implies that temperature-dependent silica deposition, permeability reduction and fluid overpressure development control dilatancy and slow-earthquake behaviour.
TL;DR: In this paper, a correlation between the structural maturity of the fault and the ratio of deep slip to surface slip that occurs on localized zones of surface rupture has been found, which implies that geologic measurements of surface slip along structurally immature faults are likely to significantly underestimate the true slip at depth in large earthquakes.
TL;DR: Water can provide an interfacial slip layer between EGaIn and other surfaces, which allows the metal to flow smoothly through capillaries and across surfaces without sticking, and provides new opportunities to control and actuate liquid metal plugs in microchannels.
Abstract: Eutectic gallium indium (EGaIn) is a promising liquid metal for a variety of electrical and optical applications that take advantage of its soft and fluid properties. The presence of a rapidly forming oxide skin on the surface of the metal causes it to stick to many surfaces, which limits the ability to easily reconfigure its shape on demand. This paper shows that water can provide an interfacial slip layer between EGaIn and other surfaces, which allows the metal to flow smoothly through capillaries and across surfaces without sticking. Rheological and surface characterization shows that the presence of water also changes the chemical composition of the oxide skin and weakens its mechanical strength, although not enough to allow the metal to flow freely in microchannels without the slip layer. The slip layer provides new opportunities to control and actuate liquid metal plugs in microchannels—including the use of continuous electrowetting—enabling new possibilities for shape reconfigurable electronics, se...
TL;DR: In this paper, the authors present an updated national-scale model for active faulting in New Zealand, summarize the current understanding of fault kinematics in 15 tectonic domains, and undertake some brief kinematic analysis including comparison of fault slip rates with GPS velocities.
Abstract: Active fault traces are a surface expression of permanent deformation that accommodates the motion within and between adjacent tectonic plates. We present an updated national-scale model for active faulting in New Zealand, summarize the current understanding of fault kinematics in 15 tectonic domains, and undertake some brief kinematic analysis including comparison of fault slip rates with GPS velocities. The model contains 635 simplified faults with tabulated parameters of their attitude (dip and dip-direction) and kinematics (sense of movement and rake of slip vector), net slip rate and a quality code. Fault density and slip rates are, as expected, highest along the central plate boundary zone, but the model is undoubtedly incomplete, particularly in rapidly eroding mountainous areas and submarine areas with limited data. The active fault data presented are of value to a range of kinematic, active fault and seismic hazard studies.
TL;DR: In this paper, a multiscale model for anisotropic, elasto-plastic, rate and temperature-sensitive deformation of polycrystalline aggregates to large plastic strains is presented.
Abstract: We present a multiscale model for anisotropic, elasto-plastic, rate- and temperature-sensitive deformation of polycrystalline aggregates to large plastic strains. The model accounts for a dislocation-based hardening law for multiple slip modes and links a single-crystal to a polycrystalline response using a crystal plasticity finite element based homogenization. It is capable of predicting local stress and strain fields based on evolving microstructure including the explicit evolution of dislocation density and crystallographic grain reorientation. We apply the model to simulate monotonic mechanical response of a hexagonal close-packed metal, zirconium (Zr), and a body-centered cubic metal, niobium (Nb), and study the texture evolution and deformation mechanisms in a two-phase Zr/Nb layered composite under severe plastic deformation. The model predicts well the texture in both co-deforming phases to very large plastic strains. In addition, it offers insights into the active slip systems underlying texture evolution, indicating that the observed textures develop by a combination of prismatic, pyramidal, and anomalous basal slip in Zr and primarily {110}〈111〉 slip and secondly {112}〈111〉 slip in Nb.
TL;DR: In this paper, the formation and slip of pyramidal dislocations in hexagonal close-packed (hcp) crystals is investigated. But the formation mechanism, dissociation, core structure and slip features are still poorly characterized.
TL;DR: In this paper, discrete dislocation dynamics simulations are used to extract latent hardening parameters coupling different slip systems, and to assess the validity of two existing constitutive models linking slip system strength to dislocation densities on all slip systems.
TL;DR: In this paper, the results were discussed with respect to the texture evolution during multiple twinning in conjunction with continuous dynamic recrystallization at room temperature, showing exceptionally high formability, even though basal and prismatic slip were initially inhibited due to the loading orientation of the deformation geometry.
TL;DR: In this article, a slip velocity boundary condition for the filtered velocity field is obtained from the derivation of the LES equations using a differential filter, and a dynamic procedure for the local slip length is additionally formulated making the slip velocity wall model free of any a priori specified coefficients.
Abstract: Wall models for large-eddy simulation (LES) are a necessity to remove the prohibitive resolution requirements of near-wall turbulence in high Reynolds turbulent flows. Traditional wall models often rely on assumptions about the local state of the boundary layer (e.g., logarithmic velocity profiles) and require a priori prescription of tunable model coefficients. In the present study, a slip velocity boundary condition for the filtered velocity field is obtained from the derivation of the LES equations using a differential filter. A dynamic procedure for the local slip length is additionally formulated making the slip velocity wall model free of any a priori specified coefficients. The accuracy of the dynamic slip velocity wall model is tested in a series of turbulent channel flows at varying Reynolds numbers and in the LES of a National Advisory Committee for Aeronautics (NACA) 4412 airfoil at near-stall conditions. The wall-modeled simulations are able to accurately predict mean flow characteristics, including the formation of a trailing-edge separation bubble in NACA 4412 configuration. The validation cases demonstrate the effectiveness of this wall-modeling approach in both attached and separated flow regimes.
TL;DR: In this paper, a multiscale physically based constitutive law for predicting the mechanical response and texture evolution of body-centered cubic (BCC) metals as a function of strain-rate and temperature is presented.
TL;DR: It is found that the (0111)/<1101> slip system has the lowest shear strength (consistent with previous experimental studies) and that this slip leads to a unique plastic deformation before failure in which a boron-carbon bond between neighboring icosahedral clusters breaks to form a carbon lone pair on the C within the icosahedron.
Abstract: Boron carbide (B_4C) is very hard, but its applications are hindered by stress-induced amorphous band formation. To explain this behavior, we used density function theory (Perdew-Burke-Ernzerhof flavor) to examine the response to shear along 11 plausible slip systems. We found that the (011 ¯ 1 ¯ )/⟨1 ¯ 101⟩ slip system has the lowest shear strength (consistent with previous experimental studies) and that this slip leads to a unique plastic deformation before failure in which a boron-carbon bond between neighboring icosahedral clusters breaks to form a carbon lone pair (Lewis base) on the C within the icosahedron. Further shear then leads this Lewis base C to form a new bond with the Lewis acidic B in the middle of a CBC chain. This then initiates destruction of this icosahedron. The result is the amorphous structure observed experimentally. We suggest how this insight could be used to strengthen B_4C.
TL;DR: In this article, the authors applied a matched filter technique to continuous seismograms recorded near the source region and identified multiple sequences of earthquake migrations at speeds of 2-10 km/d, both along strike and downdip on the fault plane, updip of the main shock area.
Abstract: To obtain a precise record of the foreshock sequence before the 2014 Iquique, Chile Mw 8.1 earthquake, we applied a matched filter technique to continuous seismograms recorded near the source region. We newly detected about 10 times the number of seismic events listed in the routinely constructed earthquake catalog and identified multiple sequences of earthquake migrations at speeds of 2–10 km/d, both along strike and downdip on the fault plane, updip of the main shock area. In addition, we found out repeating earthquakes from the newly detected events, likely indicating aseismic slip along the plate boundary fault during the foreshock sequence. These observations suggest the occurrence of multiple slow-slip events updip of the main shock area. The final slow-slip event migrated toward the main shock nucleation point. We interpret that several parts of the plate boundary fault perhaps experienced slow slip, causing stress loading on the prospective largest slip patch of the main shock rupture.
TL;DR: In this paper, an experimental and microstructural study of the frictional properties of simulated fault gouges prepared from natural limestone (96% CaCO3) and pure calcite is presented.
Abstract: We report an experimental and microstructural study of the frictional properties of simulated fault gouges prepared from natural limestone (96 % CaCO3) and pure calcite. Our experiments consisted of direct shear tests performed, under dry and wet conditions, at an effective normal stress of 50 MPa, at 18–150 °C and sliding velocities of 0.1–10 μm/s. Wet experiments used a pore water pressure of 10 MPa. Wet gouges typically showed a lower steady-state frictional strength (μ = 0.6) than dry gouges (μ = 0.7–0.8), particularly in the case of the pure calcite samples. All runs showed a transition from stable velocity strengthening to (potentially) unstable velocity weakening slip above 80–100 °C. All recovered samples showed patchy, mirror-like surfaces marking boundary shear planes. Optical study of sections cut normal to the shear plane and parallel to the shear direction showed both boundary and inclined shear bands, characterized by extreme grain comminution and a crystallographic preferred orientation. Cross-sections of boundary shears, cut normal to the shear direction using focused ion beam—SEM, from pure calcite gouges sheared at 18 and 150 °C, revealed dense arrays of rounded, ~0.3 μm-sized particles in the shear band core. Transmission electron microscopy showed that these particles consist of 5–20 nm sized calcite nanocrystals. All samples showed evidence for cataclasis and crystal plasticity. Comparing our results with previous models for gouge friction, we suggest that frictional behaviour was controlled by competition between crystal plastic and granular flow processes active in the shear bands, with water facilitating pressure solution, subcritical cracking and intergranular lubrication. Our data have important implications for the depth of the seismogenic zone in tectonically active limestone terrains. Contrary to recent claims, our data also demonstrate that nanocrystalline mirror-like slip surfaces in calcite(-rich) faults are not necessarily indicative of seismic slip rates.
TL;DR: This work is intended as an entry-level review for researchers moving into the field of interfacial slip, and as an indication of outstanding problems that need to be addressed for the field to reach full maturity.
TL;DR: In this paper, the authors conducted a dynamic numerical analysis of a fault parallel to a tabular ore deposit and showed that the maximum dynamic shear displacement increment induced by stope extraction is significantly affected by the friction angle of the fault, as well as mining depth and position of fault with respect to the orebody.
TL;DR: In this paper, a modified two-component, four-equation, nonhomogeneous equilibrium model was employed for the alumina/water nanofluid, which fully accounted for the effect of the nanoparticle volume fraction distribution.
TL;DR: In this paper, the effect of joint length on the shear behavior of rough rock joints using PFC2D was investigated and it was found that the mobilisation of different sized asperities at different scales resulted in the observed scale effect.
TL;DR: In this paper, the role of the twinning/detwinning process in cyclic plastic deformation of Mg alloys was investigated in both strain-controlled and stress-controlled cyclic tension compression experiments.
TL;DR: A series of microstructurally-differing, large-grained, notched, polycrystal BCC ferritic steel bend test samples have been analyzed to extract the experimentally observed sites of fatigue crack nucleation together with the number of cycles to cause crack formation.
TL;DR: In this paper, the authors explore the links between porefluid pressure and locking patterns at the subduction interface ruptured during the magnitude 8.8 Chile earthquake in 2010 and conclude that variations in pore fluid pressure at the plate interface control the degree of interseismic locking and therefore the slip distribution of large earthquake ruptures.
Abstract: Large subduction-zone earthquakes are thought to occur where the down-going and overriding tectonic plates are strongly locked. Analysis of geodetic and seismic data collected in the decade before the 2010 Chile earthquake shows that variations in pore-fluid pressure correlate with the degree of plate-interface locking, and may therefore control earthquake rupture. Constraints on the potential size and recurrence time of strong subduction-zone earthquakes come from the degree of locking between the down-going and overriding plates, in the period between large earthquakes. In many cases, this interseismic locking degree correlates with slip during large earthquakes1,2,3,4 or is attributed to variations in fluid content at the plate interface5. Here we use geodetic and seismological data to explore the links between pore-fluid pressure and locking patterns at the subduction interface ruptured during the magnitude 8.8 Chile earthquake in 2010. High-resolution three-dimensional seismic tomography reveals variations in the ratio of seismic P- to S-wave velocities (Vp/Vs) along the length of the subduction-zone interface. High Vp/Vs domains, interpreted as zones of elevated pore-fluid pressure, correlate spatially with parts of the plate interface that are poorly locked and slip aseismically. In contrast, low Vp/Vs domains, interpreted as zones of lower pore-fluid pressure, correlate with locked parts of the plate interface, where unstable slip and earthquakes occur. Variations in pore-fluid pressure are caused by the subduction and dehydration of a hydrothermally altered oceanic fracture zone. We conclude that variations in pore-fluid pressure at the plate interface control the degree of interseismic locking and therefore the slip distribution of large earthquake ruptures.