The Experts below are selected from a list of 44832 Experts worldwide ranked by ideXlab platform
Akihisa Inoue - One of the best experts on this subject based on the ideXlab platform.
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viscous flow in sliding shear Band formed during tensile deformation of hypoeutectic zr based metallic glass
Intermetallics, 2011Co-Authors: Yoshihiko Yokoyama, Hitoo Tokunaga, A R Yavari, Masahiro Yamada, Tohru Yamasaki, Kazutaka Fujita, Akihisa InoueAbstract:Abstract The Zr 70 Ni 16 Cu 6 Al 8 bulk metallic glass (BMG) was tested in tension mode using high-speed imaging in order to monitor the viscous flow inside a sliding shear Band. Assuming the shear Band Thickness to be 15 nm, we estimated the shear viscosity to be ∼3.8 × 10 3 Pa s. The apparent temperature in the shear Band was estimated to reach approximately 852 K on the basis of the relationship between the viscosity and the strain rate in the supercooled liquid region and was found to be considerably lower than the melting temperature (1293 K).
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Viscous flow in sliding shear Band formed during tensile deformation of hypoeutectic Zr-based metallic glass
Intermetallics, 2011Co-Authors: Yoshihiko Yokoyama, Hitoo Tokunaga, A R Yavari, Masahiro Yamada, Tohru Yamasaki, Kazutaka Fujita, Akihisa InoueAbstract:The Zr(70)Ni(16)Cu(6)Al(8) bulk metallic glass (BMG) was tested in tension mode using high-speed imaging in order to monitor the viscous flow inside a sliding shear Band. Assuming the shear Band Thickness to be 15 nm, we estimated the shear viscosity to be similar to 3.8 x 10(3) Pa s. The apparent temperature in the shear Band was estimated to reach approximately 852 K on the basis of the relationship between the viscosity and the strain rate in the supercooled liquid region and was found to be considerably lower than the melting temperature (1293 K). (C) 2011 Published by Elsevier Ltd.
A R Yavari - One of the best experts on this subject based on the ideXlab platform.
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viscous flow in sliding shear Band formed during tensile deformation of hypoeutectic zr based metallic glass
Intermetallics, 2011Co-Authors: Yoshihiko Yokoyama, Hitoo Tokunaga, A R Yavari, Masahiro Yamada, Tohru Yamasaki, Kazutaka Fujita, Akihisa InoueAbstract:Abstract The Zr 70 Ni 16 Cu 6 Al 8 bulk metallic glass (BMG) was tested in tension mode using high-speed imaging in order to monitor the viscous flow inside a sliding shear Band. Assuming the shear Band Thickness to be 15 nm, we estimated the shear viscosity to be ∼3.8 × 10 3 Pa s. The apparent temperature in the shear Band was estimated to reach approximately 852 K on the basis of the relationship between the viscosity and the strain rate in the supercooled liquid region and was found to be considerably lower than the melting temperature (1293 K).
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Viscous flow in sliding shear Band formed during tensile deformation of hypoeutectic Zr-based metallic glass
Intermetallics, 2011Co-Authors: Yoshihiko Yokoyama, Hitoo Tokunaga, A R Yavari, Masahiro Yamada, Tohru Yamasaki, Kazutaka Fujita, Akihisa InoueAbstract:The Zr(70)Ni(16)Cu(6)Al(8) bulk metallic glass (BMG) was tested in tension mode using high-speed imaging in order to monitor the viscous flow inside a sliding shear Band. Assuming the shear Band Thickness to be 15 nm, we estimated the shear viscosity to be similar to 3.8 x 10(3) Pa s. The apparent temperature in the shear Band was estimated to reach approximately 852 K on the basis of the relationship between the viscosity and the strain rate in the supercooled liquid region and was found to be considerably lower than the melting temperature (1293 K). (C) 2011 Published by Elsevier Ltd.
Yoshihiko Yokoyama - One of the best experts on this subject based on the ideXlab platform.
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viscous flow in sliding shear Band formed during tensile deformation of hypoeutectic zr based metallic glass
Intermetallics, 2011Co-Authors: Yoshihiko Yokoyama, Hitoo Tokunaga, A R Yavari, Masahiro Yamada, Tohru Yamasaki, Kazutaka Fujita, Akihisa InoueAbstract:Abstract The Zr 70 Ni 16 Cu 6 Al 8 bulk metallic glass (BMG) was tested in tension mode using high-speed imaging in order to monitor the viscous flow inside a sliding shear Band. Assuming the shear Band Thickness to be 15 nm, we estimated the shear viscosity to be ∼3.8 × 10 3 Pa s. The apparent temperature in the shear Band was estimated to reach approximately 852 K on the basis of the relationship between the viscosity and the strain rate in the supercooled liquid region and was found to be considerably lower than the melting temperature (1293 K).
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Viscous flow in sliding shear Band formed during tensile deformation of hypoeutectic Zr-based metallic glass
Intermetallics, 2011Co-Authors: Yoshihiko Yokoyama, Hitoo Tokunaga, A R Yavari, Masahiro Yamada, Tohru Yamasaki, Kazutaka Fujita, Akihisa InoueAbstract:The Zr(70)Ni(16)Cu(6)Al(8) bulk metallic glass (BMG) was tested in tension mode using high-speed imaging in order to monitor the viscous flow inside a sliding shear Band. Assuming the shear Band Thickness to be 15 nm, we estimated the shear viscosity to be similar to 3.8 x 10(3) Pa s. The apparent temperature in the shear Band was estimated to reach approximately 852 K on the basis of the relationship between the viscosity and the strain rate in the supercooled liquid region and was found to be considerably lower than the melting temperature (1293 K). (C) 2011 Published by Elsevier Ltd.
Jean Sulem - One of the best experts on this subject based on the ideXlab platform.
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The importance of Thermo-Hydro-Mechanical couplings and microstructure to strain localization in 3D continua with application to seismic faults. Part II: Numerical implementation and post-bifurcation analysis
Journal of the Mechanics and Physics of Solids, 2018Co-Authors: Hadrien Rattez, Ioannis Stefanou, Jean Sulem, Manolis Veveakis, Thomas PouletAbstract:In this paper, we study the phenomenon of localization of deformation in fault gouges during seismic slip. This process is of key importance to understand frictional heating and energy budget during an earthquake. A infinite layer of fault gouge is modeled as a Cosserat continuum taking into account Thermo-Hydro-Mechanical (THM) couplings. The theoretical aspects of the problem are presented in the companion paper (Rattez et al., 2017a), together with a linear stability analysis to determine the conditions of localization and estimate the shear Band Thickness. In this Part II of the study, we investigate the post-bifurcation evolution of the system by integrating the full system of non linear equations using Finite Elements. The problem is formulated in the framework of Cosserat theory. It enables to introduce information about the microstructure of the material in the constitutive equations and to regularize the mathematical problem in the post-localization regime. We emphasize the influence of the microstructure and of the softening law on the material response and the strain localization process. The weakening effect of pore fluid thermal pressurization induced by shear heating is examined and quantified. It enhances the weakening process and contributes to the narrowing of shear Band Thickness. Comparisons with the linear analysis exhibit that when the perturbed field of shear deformation dominates, the estimation of the shear Band Thickness obtained from linear stability analysis differs from the one obtained from the finite element computations, demonstrating the importance of post-localization numerical simulations.
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The importance of Thermo-Hydro-Mechanical couplings and microstructure to strain localization in 3D continua with application to seismic faults. Part II: Numerical implementation and post-bifurcation analysis
Journal of the Mechanics and Physics of Solids, 2018Co-Authors: Hadrien Rattez, Ioannis Stefanou, Jean Sulem, Manolis Veveakis, Thomas PouletAbstract:Abstract In this paper we study the phenomenon of localization of deformation in fault gouges during seismic slip. This process is of key importance to understand frictional heating and energy budget during an earthquake. A infinite layer of fault gouge is modeled as a Cosserat continuum taking into account Thermo-Hydro-Mechanical (THM) couplings. The theoretical aspects of the problem are presented in the companion paper (Rattez et al., 2017a), together with a linear stability analysis to determine the conditions of localization and estimate the shear Band Thickness. In this Part II of the study, we investigate the post-bifurcation evolution of the system by integrating numerically the full system of non-linear equations using the method of Finite Elements. The problem is formulated in the framework of Cosserat theory. It enables to introduce information about the microstructure of the material in the constitutive equations and to regularize the mathematical problem in the post-localization regime. We emphasize the influence of the size of the microstructure and of the softening law on the material response and the strain localization process. The weakening effect of pore fluid thermal pressurization induced by shear heating is examined and quantified. It enhances the weakening process and contributes to the narrowing of shear Band Thickness. Moreover, due to THM couplings an apparent rate-dependency is observed, even for rate-independent material behavior. Finally, comparisons show that when the perturbed field of shear deformation dominates, the estimation of the shear Band Thickness obtained from linear stability analysis differs from the one obtained from the finite element computations, demonstrating the importance of post-localization numerical simulations.
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Strain Localization with Rate Dependent Models Versus Cosserat Continuum: An Illustrative Example
Springer Series in Geomechanics and Geoengineering, 2017Co-Authors: Ioannis Stefanou, Jean SulemAbstract:A simple example of adiabatic shearing of a rock layer under constant shear stress is considered in order to investigate and juxtapose two different modeling frameworks concerning strain localization and shear Band Thickness. The first framework is the Cauchy continuum with a rate dependent constitutive law (viscoplasticity). The second modeling framework is Cosserat elastoplasticity. Cosserat continuum is a special case of higher order continua. It is shown that the conditions for shear Band triggering have a similar mathematical form, even though the starting point is different from a physical point of view.
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Chemically induced compaction Bands: Triggering conditions and Band Thickness
Journal of Geophysical Research: Solid Earth, 2014Co-Authors: Ioannis Stefanou, Jean SulemAbstract:During compaction Band formation, various mechanisms can be involved at different scales. Mechanical and chemical degradation of the solid skeleton and grain damage are important factors that may trigger instabilities in the form of compaction Bands. Here we explore the conditions of compaction Band formation in quartz- and carbonate-based geomaterials by considering the effect of chemical dissolution and grain breakage. As the stresses/deformations evolve, the grains of the material break, leading to an increase of their specific surface. Consequently, their dissolution is accelerated and chemical softening is triggered. By accounting for (a) the mass diffusion of the system, (b) a macroscopic failure criterion with dissolution softening, and (c) the reaction kinetics at the microlevel, a model is proposed and the conditions for compaction instabilities are investigated. Distinguishing the microscale (grain level) from the macrolevel (representative elementary volume) and considering the heterogeneous microstructure of the representative elementary volume, it is possible to discuss the Thickness and periodicity of compaction Bands. Two case studies are investigated. The first one concerns a sandstone rock reservoir which is water flooded and the second one a carbonate rock in which CO2 is injected for storage. It is shown that compaction Band instabilities are possible in both cases.
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Chemically induced compaction Bands: Triggering conditions and Band Thickness
Journal of Geophysical Research : Solid Earth, 2014Co-Authors: Ioannis Stefanou, Jean SulemAbstract:During compaction Band formation various mechanisms can be involved at different scales. Mechanical and chemical degradation of the solid skeleton and grain damage are important factors that may trigger instabilities in the form of compaction Bands. Here we explore the conditions of compaction Band formation in quartz- and carbonate-based geomaterials by considering the effect of chemical dissolution and grain breakage. As the stresses/deformations evolve, the grains of the material break leading to an increase of their specific surface. Consequently, their dissolution is accelerated and chemical softening is triggered. By accounting for (a) the mass diffusion of the system, (b) a macroscopic failure criterion with dissolution softening and (c) the reaction kinetics at the micro level, a model is proposed and the conditions for compaction instabilities are investigated. Distinguishing the micro-scale (grain level) from the macro-level (Representative Elementary Volume) and considering the heterogeneous microstructure of the REV it is possible to discuss the Thickness and periodicity of compaction Bands. Two case studies are investigated. The first one concerns a sandstone rock reservoir which is water flooded and the second one a carbonate rock in which CO2 is injected for storage. It is shown that compaction Band instabilities are possible in both cases.
James A Elliott - One of the best experts on this subject based on the ideXlab platform.
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asymptotic limits on tablet coating variability based on cap to Band Thickness distributions a discrete element model dem study
Chemical Engineering Science, 2017Co-Authors: Chunlei Pei, James A ElliottAbstract:Abstract The uniformity of the coating Thickness distribution is an important quality metric in the manufacture of pharmaceutical tablets during the spray coating process. An investigation of the asymptotic limits of coating Thickness variability of tablets of different shapes was carried out based on their cap-to-Band coating Thickness distributions. A theoretical analysis shows that the cap-to-Band coating Thickness ratio is expected to be equal to the cap-to-Band area ratio projected onto the spray direction divided by the actual cap-to-Band surface area ratio. When the cap-to-Band projected area ratio is larger (or smaller) than the cap-to-Band surface area ratio, the mean coating Thickness on the cap is larger (or smaller) than that on the Band. To verify this, the dynamics of tablets in a rotating pan was modelled using discrete element method (DEM) simulations, while an image analysis technique based on the output of DEM simulations was applied to model the spray coating process and analyse the cap-to-Band coating Thickness ratio. A ray-tracing sampling method was further used to obtain the cap-to-Band sample ratio. It was also found that a smaller spray angle with respect to the horizontal direction can decrease or even invert the cap-to-Band coating Thickness ratio, leading to a larger coating Thickness on the Band than the cap. Nevertheless, an asymptotic value of cap-to-Band relative standard deviation can be reached once the cap-to-Band coating Thickness ratio becomes constant during the coating process. This asymptotic limit is within the range predicted based on the cap-to-Band projected area ratio and surface area ratio.
