The Experts below are selected from a list of 53583 Experts worldwide ranked by ideXlab platform
Vikram Deshpande - One of the best experts on this subject based on the ideXlab platform.
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interfacial diffusion in high temperature deformation of composites a discrete dislocation plasticity investigation
Journal of The Mechanics and Physics of Solids, 2017Co-Authors: Siamak Soleymani Shishvan, Robert M. Mcmeeking, Tresa M. Pollock, Vikram DeshpandeAbstract:Abstract We present a discrete dislocation plasticity (DDP) framework to analyse the high temperature deformation of multi-phase materials (composites) comprising a matrix and inclusions. Deformation of the phases is by climb-assisted glide of the dislocations while the Particles can also deform due to stress-driven interfacial diffusion. The general framework is used to analyse the uniaxial tensile deformation of a composite comprising elastic Particles with dislocation plasticity only present in the matrix phase. When dislocation motion is restricted to only glide within the matrix a strong size effect of the composite strength is predicted with the strength increasing with decreasing unit cell size due to dislocations forming pile-ups against the matrix/Particle Interface. Interfacial diffusion decreases the composite strength as it enhances the elongation of the elastic Particles along the loading direction. When dislocation motion occurs by climb-assisted glide within the matrix the size effect of the strength is reduced as dislocations no longer arrange high energy pile-up structures but rather form lower energy dislocation cell networks. While interfacial diffusion again reduces the composite strength, in contrast to continuum plasticity predictions, the elongation of the Particles is almost independent of the interfacial diffusion constant. Rather, in DDP the reduction in composite strength due to interfacial diffusion is a result of changes in the dislocation structures within the matrix and the associated enhanced dislocation climb rates in the matrix.
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climb enabled discrete dislocation plasticity analysis of the deformation of a Particle reinforced composite
Journal of Applied Mechanics, 2015Co-Authors: C Ayas, Vikram Deshpande, Lcp Lisanne Dautzenberg, Mgd Marc GeersAbstract:© 2015 by ASME. The shear deformation of a composite comprising elastic Particles in a single crystal elastic-plastic matrix is analyzed using a discrete dislocation plasticity (DDP) framework wherein dislocation motion occurs via climb-assisted glide. The topology of the reinforcement is such that dislocations cannot continuously transverse the matrix by glide-only without encountering the Particles that are impenetrable to dislocations. When dislocation motion is via glide-only, the shear stress versus strain response is strongly strain hardening with the hardening rate increasing with decreasing Particle size for a fixed volume fraction of Particles. This is due to the formation of dislocation pile-ups at the Particle/matrix Interfaces. The back stresses associated with these pile-ups result in a size effect and a strong Bauschinger effect. By contrast, when dislocation climb is permitted, the dislocation pile-ups break up by forming lower energy dislocation wall structures at the Particle/matrix Interfaces. This results in a significantly reduced size effect and reduced strain hardening. In fact, with increasing climb mobility an "inverse size" effect is also predicted where the strength decreases with decreasing Particle size. Mass transport along the matrix/Particle Interface by dislocation climb causes this change in the response and also results in a reduction in the lattice rotations and density of geometrically necessary dislocations (GNDs) compared to the case where dislocation motion is by glide-only.
Eligiusz Wajnryb - One of the best experts on this subject based on the ideXlab platform.
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motion of a spherical Particle near a planar fluid fluid Interface the effect of surface incompressibility
Journal of Chemical Physics, 2010Co-Authors: Jerzy Blawzdziewicz, Maria L Ekieljezewska, Eligiusz WajnrybAbstract:Hydrodynamic coupling of a spherical Particle to an undeformable planar fluid-fluid Interface under creeping-flow conditions is discussed. The Interface can be either surfactant-free or covered with an incompressible surfactant monolayer. In the incompressible surfactant limit, a uniform surfactant concentration is maintained by Marangoni stresses associated with infinitesimal surfactant redistribution. Our detailed numerical calculations show that the effect of surface incompressibility on lateral Particle motion is accurately accounted for by the first reflection of the flow from the Interface. For small Particle-Interface distances, the remaining contributions are significant, but they are weakly affected by the surface incompressibility. We show that for small Particle-wall gaps, the transverse and lateral Particle resistance coefficients can be rescaled onto corresponding universal master curves. The scaling functions depend on a scaling variable that combines the Particle-wall gap with the viscosity ratio between fluids on both sides of the Interface. A logarithmic dependence of the contact value of the lateral resistance function on the viscosity ratio is derived. Accurate numerical calculations are performed using our Cartesian-representation method.
Reza Ebrahimi - One of the best experts on this subject based on the ideXlab platform.
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a new expression for spherical aerosol drag in slip flow regime
Journal of Aerosol Science, 2010Co-Authors: Abouzar Moshfegh, Mehrzad Shams, Goodarz Ahmadi, Reza EbrahimiAbstract:A 3D simulation study for an incompressible slip flow around a spherical aerosol Particle was performed. The full Navier–Stokes equations were solved and the velocity jump at the gas–Particle Interface was treated numerically by imposition of the slip boundary condition. Analytical solution to the Stokesian slip flow past a spherical Particle was used as a benchmark for code verification, and excellent agreement was achieved. The simulation results showed that in addition to the Knudsen number, the Reynolds number affects the slip correction factor. Thus, the Cunningham-based slip corrections must be augmented by the inclusion of the effect of Reynolds number for application to Lagrangian tracking of fine Particles. A new expression for the slip correction factor as a function of both Knudsen number and Reynolds number was developed. The Particle total drag coefficient was also correlated against Re and Kn over the range of gas–Particle relative speeds yielding the incompressible slip flow from the Stokesian regime up to the threshold of compressibility. Inclusion of gas slip on the Particle surface enhances the accuracy of Particle drag force prediction up to 40.9% in the range of 0.01
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a novel slip correction factor for spherical aerosol Particles
World Academy of Science Engineering and Technology International Journal of Mechanical Aerospace Industrial Mechatronic and Manufacturing Engineering, 2008Co-Authors: Abouzar Moshfegh, Mehrzad Shams, Goodarz Ahmadi, Reza EbrahimiAbstract:A 3D simulation study for an incompressible slip flow around a spherical aerosol Particle was performed. The full Navier-Stokes equations were solved and the velocity jump at the gas-Particle Interface was treated numerically by imposition of the slip boundary condition. Analytical solution to the Stokesian slip flow past a spherical Particle was used as a benchmark for code verification, and excellent agreement was achieved. The Simulation results showed that in addition to the Knudsen number, the Reynolds number affects the slip correction factor. Thus, the Cunningham-based slip correctio- ns must be augmented by the inclusion of the effect of Reynolds number for application to Lagrangian tracking of fine Particles. A new expression for the slip correction factor as a function of both Knudsen number and Reynolds number was developed.
Siamak Soleymani Shishvan - One of the best experts on this subject based on the ideXlab platform.
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interfacial diffusion in high temperature deformation of composites a discrete dislocation plasticity investigation
Journal of The Mechanics and Physics of Solids, 2017Co-Authors: Siamak Soleymani Shishvan, Robert M. Mcmeeking, Tresa M. Pollock, Vikram DeshpandeAbstract:Abstract We present a discrete dislocation plasticity (DDP) framework to analyse the high temperature deformation of multi-phase materials (composites) comprising a matrix and inclusions. Deformation of the phases is by climb-assisted glide of the dislocations while the Particles can also deform due to stress-driven interfacial diffusion. The general framework is used to analyse the uniaxial tensile deformation of a composite comprising elastic Particles with dislocation plasticity only present in the matrix phase. When dislocation motion is restricted to only glide within the matrix a strong size effect of the composite strength is predicted with the strength increasing with decreasing unit cell size due to dislocations forming pile-ups against the matrix/Particle Interface. Interfacial diffusion decreases the composite strength as it enhances the elongation of the elastic Particles along the loading direction. When dislocation motion occurs by climb-assisted glide within the matrix the size effect of the strength is reduced as dislocations no longer arrange high energy pile-up structures but rather form lower energy dislocation cell networks. While interfacial diffusion again reduces the composite strength, in contrast to continuum plasticity predictions, the elongation of the Particles is almost independent of the interfacial diffusion constant. Rather, in DDP the reduction in composite strength due to interfacial diffusion is a result of changes in the dislocation structures within the matrix and the associated enhanced dislocation climb rates in the matrix.
Abouzar Moshfegh - One of the best experts on this subject based on the ideXlab platform.
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heat transfer analysis of a microspherical Particle in the slip flow regime by considering variable properties
Heat Transfer Engineering, 2015Co-Authors: Behzad Mohajer, Mehrzad Shams, Vahid Aliakbar, Abouzar MoshfeghAbstract:In order to investigate how far the temperature-dependent fluid properties and characteristic length influence the drag coefficient and the heat flux, a three-dimensional simulation study for a slip flow around an unconfined microspherical Particle has been performed. Gas properties such as density, viscosity, conductivity, and mean free path were assumed to vary with temperature. Slip velocity and temperature jump at the gas Particle Interface were both treated numerically by imposition of the slip boundary conditions. The effects of variable gas properties and Knudsen number on momentum and heat transfer were also taken into account. It was concluded that for microflows with high heat transfer rates, the constant fluid properties approximation is very crude. In addition, the slip velocity and temperature jump affect the heat transfer in opposite ways: a large slip on the wall increases the convection along the surface, whereas a large temperature jump decreases the heat transfer by reducing the temperat...
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a new expression for spherical aerosol drag in slip flow regime
Journal of Aerosol Science, 2010Co-Authors: Abouzar Moshfegh, Mehrzad Shams, Goodarz Ahmadi, Reza EbrahimiAbstract:A 3D simulation study for an incompressible slip flow around a spherical aerosol Particle was performed. The full Navier–Stokes equations were solved and the velocity jump at the gas–Particle Interface was treated numerically by imposition of the slip boundary condition. Analytical solution to the Stokesian slip flow past a spherical Particle was used as a benchmark for code verification, and excellent agreement was achieved. The simulation results showed that in addition to the Knudsen number, the Reynolds number affects the slip correction factor. Thus, the Cunningham-based slip corrections must be augmented by the inclusion of the effect of Reynolds number for application to Lagrangian tracking of fine Particles. A new expression for the slip correction factor as a function of both Knudsen number and Reynolds number was developed. The Particle total drag coefficient was also correlated against Re and Kn over the range of gas–Particle relative speeds yielding the incompressible slip flow from the Stokesian regime up to the threshold of compressibility. Inclusion of gas slip on the Particle surface enhances the accuracy of Particle drag force prediction up to 40.9% in the range of 0.01
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a novel slip correction factor for spherical aerosol Particles
World Academy of Science Engineering and Technology International Journal of Mechanical Aerospace Industrial Mechatronic and Manufacturing Engineering, 2008Co-Authors: Abouzar Moshfegh, Mehrzad Shams, Goodarz Ahmadi, Reza EbrahimiAbstract:A 3D simulation study for an incompressible slip flow around a spherical aerosol Particle was performed. The full Navier-Stokes equations were solved and the velocity jump at the gas-Particle Interface was treated numerically by imposition of the slip boundary condition. Analytical solution to the Stokesian slip flow past a spherical Particle was used as a benchmark for code verification, and excellent agreement was achieved. The Simulation results showed that in addition to the Knudsen number, the Reynolds number affects the slip correction factor. Thus, the Cunningham-based slip correctio- ns must be augmented by the inclusion of the effect of Reynolds number for application to Lagrangian tracking of fine Particles. A new expression for the slip correction factor as a function of both Knudsen number and Reynolds number was developed.