The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Hyun-chul Park - One of the best experts on this subject based on the ideXlab platform.
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A study of micro bending test for polycrystalline by modified strain gradient theory
Nanosensors Biosensors and Info-Tech Sensors and Systems 2012, 2012Co-Authors: Bong-bu Jung, Hyun-chul ParkAbstract:Recent experiments with non-uniform plastic deformation have shown the size Effects in micro/nano scale. But the classical continuum plasticity can't predict these size Effects in micro/nano scale, since the constitutive equation of the classical mechanics doesn't include the internal length as a parameter for the deformation. The mechanism based strain gradient plasticity is one of the methods to analyze non-uniform deformation behavior in micro/nano scale. The MSG plasticity is the multi-scale analysis connecting the micro-scale notion of the statistically stored dislocations and the geometrically necessary dislocation to meso-scale deformation using the strain gradient. In this paper, modified strain gradient theory is proposed based on the nonhomogeneity of polycrystalline metallic materials and Free Surface Effect. Consideration of the geometrically necessary dislocations on the grain boundary and the Free Surface Effect suggests a relationship between the characteristic length, specimen size and grain size. This relationship can explain the size Effects and flow stress in micro/nanoscale structures. We will propose a new model for bending tests using the modified strain gradient plasticity theory. Using the proposed model, bending behavior of polycrystalline materials in micron-scale structures is investigated, and compared with experimental results from other researchers.
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Analysis of microbending tests for polycrystalline materials using the modified strain gradient theory
International Journal of Solids and Structures, 2012Co-Authors: Bong-bu Jung, Hun-kee Lee, Hyun-chul ParkAbstract:AbstractA modified strain gradient theory is proposed based on the nonhomogeneity of polycrystalline metallic materials and Free Surface Effects. Consideration of the geometrically necessary dislocations on the grain boundary and the Free Surface Effect suggests a relationship between the characteristic length, specimen size and grain size. This relationship can explain the size Effects and flow stress in micro/nanoscale structures. We will propose a new model for bending tests using the modified strain gradient plasticity theory. Using the proposed model, bending behavior of polycrystalline materials in micron-scale structures is investigated, and compared with experimental results from other researchers
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On the size Effect for micro-scale structures under the plane bulge test using the modified strain gradient theory
International Journal of Precision Engineering and Manufacturing, 2011Co-Authors: Hun-kee Lee, Bong-bu Jung, Dongseob Kim, Hyun-chul ParkAbstract:A modified strain gradient theory is proposed based on the nonhomogeneity of polycrystalline metallic materials. Geometrically necessary dislocations are generated on the slip planes as well as on the grain boundary to accommodate deformation with minimum internal stress. Since amount of the geometrically necessary dislocation depends on the deformation shape, specimen size and grain size, it is an important factor for the modified strain gradient theory and the size Effect. This new theory differs from the mechanism based strain gradient plasticity in its consideration of the geometrically necessary dislocations on the grain boundary and Free Surface Effect. This theory provides a possible explanation for conflicting size Effect: the smaller can be either harder or softer due to the deformation. Using the proposed theory, analysis of the Effect of both specimen and grain size under the plane bulge test of polycrystalline materials is performed.
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Analysis of the Effect of both specimen size and grain size on the tensile strength of the polycrystalline metallic materials
Nanosensors Biosensors and Info-Tech Sensors and Systems 2010, 2010Co-Authors: Bong-bu Jung, Hun-kee Lee, Hyun-chul ParkAbstract:A modified strain gradient plasticity theory is proposed based on the mechanism-based strain gradient (MSG) plasticity. This study is motivated by nonhomogeneity of polycrystalline materials. We believe that the geometrically necessary dislocations (GND) are generated on slip system as well as grain boundary to accommodate the deformation shape with internal stress. The new theory differs from the MSG plasticity in consideration of the GND on grain boundary and Free Surface Effect of polycrystalline materials. A model describing the size Effect on the tensile strength of crystalline metallic materials is investigated. Using the nonhomogeneity of polycrystalline materials and Free Surface Effect, the density of the geometrically necessary dislocations during tension is derived. Using the proposed model, an analysis of the Effect of both specimen size and grain size on the tensile strength of the polycrystalline materials is carried out.
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Analysis of flow stress and size Effect on polycrystalline metallic materials in tension
Materials Science and Engineering: A, 2009Co-Authors: Hun-kee Lee, Bong-bu Jung, Youngdeuk Kim, Woonbong Hwang, Hyun-chul ParkAbstract:A model describing the size Effect on the tensile strength of crystalline metallic materials is investigated. Using the nonhomogeneity of polycrystalline materials and Free Surface Effect, the density of the geometrically necessary dislocations during tension is derived. Using the proposed model, an analysis of the Effect of both specimen size and grain size on the tensile strength of the polycrystalline metallic materials is carried out.
Bong-bu Jung - One of the best experts on this subject based on the ideXlab platform.
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A study of micro bending test for polycrystalline by modified strain gradient theory
Nanosensors Biosensors and Info-Tech Sensors and Systems 2012, 2012Co-Authors: Bong-bu Jung, Hyun-chul ParkAbstract:Recent experiments with non-uniform plastic deformation have shown the size Effects in micro/nano scale. But the classical continuum plasticity can't predict these size Effects in micro/nano scale, since the constitutive equation of the classical mechanics doesn't include the internal length as a parameter for the deformation. The mechanism based strain gradient plasticity is one of the methods to analyze non-uniform deformation behavior in micro/nano scale. The MSG plasticity is the multi-scale analysis connecting the micro-scale notion of the statistically stored dislocations and the geometrically necessary dislocation to meso-scale deformation using the strain gradient. In this paper, modified strain gradient theory is proposed based on the nonhomogeneity of polycrystalline metallic materials and Free Surface Effect. Consideration of the geometrically necessary dislocations on the grain boundary and the Free Surface Effect suggests a relationship between the characteristic length, specimen size and grain size. This relationship can explain the size Effects and flow stress in micro/nanoscale structures. We will propose a new model for bending tests using the modified strain gradient plasticity theory. Using the proposed model, bending behavior of polycrystalline materials in micron-scale structures is investigated, and compared with experimental results from other researchers.
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Analysis of microbending tests for polycrystalline materials using the modified strain gradient theory
International Journal of Solids and Structures, 2012Co-Authors: Bong-bu Jung, Hun-kee Lee, Hyun-chul ParkAbstract:AbstractA modified strain gradient theory is proposed based on the nonhomogeneity of polycrystalline metallic materials and Free Surface Effects. Consideration of the geometrically necessary dislocations on the grain boundary and the Free Surface Effect suggests a relationship between the characteristic length, specimen size and grain size. This relationship can explain the size Effects and flow stress in micro/nanoscale structures. We will propose a new model for bending tests using the modified strain gradient plasticity theory. Using the proposed model, bending behavior of polycrystalline materials in micron-scale structures is investigated, and compared with experimental results from other researchers
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On the size Effect for micro-scale structures under the plane bulge test using the modified strain gradient theory
International Journal of Precision Engineering and Manufacturing, 2011Co-Authors: Hun-kee Lee, Bong-bu Jung, Dongseob Kim, Hyun-chul ParkAbstract:A modified strain gradient theory is proposed based on the nonhomogeneity of polycrystalline metallic materials. Geometrically necessary dislocations are generated on the slip planes as well as on the grain boundary to accommodate deformation with minimum internal stress. Since amount of the geometrically necessary dislocation depends on the deformation shape, specimen size and grain size, it is an important factor for the modified strain gradient theory and the size Effect. This new theory differs from the mechanism based strain gradient plasticity in its consideration of the geometrically necessary dislocations on the grain boundary and Free Surface Effect. This theory provides a possible explanation for conflicting size Effect: the smaller can be either harder or softer due to the deformation. Using the proposed theory, analysis of the Effect of both specimen and grain size under the plane bulge test of polycrystalline materials is performed.
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Analysis of the Effect of both specimen size and grain size on the tensile strength of the polycrystalline metallic materials
Nanosensors Biosensors and Info-Tech Sensors and Systems 2010, 2010Co-Authors: Bong-bu Jung, Hun-kee Lee, Hyun-chul ParkAbstract:A modified strain gradient plasticity theory is proposed based on the mechanism-based strain gradient (MSG) plasticity. This study is motivated by nonhomogeneity of polycrystalline materials. We believe that the geometrically necessary dislocations (GND) are generated on slip system as well as grain boundary to accommodate the deformation shape with internal stress. The new theory differs from the MSG plasticity in consideration of the GND on grain boundary and Free Surface Effect of polycrystalline materials. A model describing the size Effect on the tensile strength of crystalline metallic materials is investigated. Using the nonhomogeneity of polycrystalline materials and Free Surface Effect, the density of the geometrically necessary dislocations during tension is derived. Using the proposed model, an analysis of the Effect of both specimen size and grain size on the tensile strength of the polycrystalline materials is carried out.
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Analysis of flow stress and size Effect on polycrystalline metallic materials in tension
Materials Science and Engineering: A, 2009Co-Authors: Hun-kee Lee, Bong-bu Jung, Youngdeuk Kim, Woonbong Hwang, Hyun-chul ParkAbstract:A model describing the size Effect on the tensile strength of crystalline metallic materials is investigated. Using the nonhomogeneity of polycrystalline materials and Free Surface Effect, the density of the geometrically necessary dislocations during tension is derived. Using the proposed model, an analysis of the Effect of both specimen size and grain size on the tensile strength of the polycrystalline metallic materials is carried out.
Hun-kee Lee - One of the best experts on this subject based on the ideXlab platform.
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Analysis of microbending tests for polycrystalline materials using the modified strain gradient theory
International Journal of Solids and Structures, 2012Co-Authors: Bong-bu Jung, Hun-kee Lee, Hyun-chul ParkAbstract:AbstractA modified strain gradient theory is proposed based on the nonhomogeneity of polycrystalline metallic materials and Free Surface Effects. Consideration of the geometrically necessary dislocations on the grain boundary and the Free Surface Effect suggests a relationship between the characteristic length, specimen size and grain size. This relationship can explain the size Effects and flow stress in micro/nanoscale structures. We will propose a new model for bending tests using the modified strain gradient plasticity theory. Using the proposed model, bending behavior of polycrystalline materials in micron-scale structures is investigated, and compared with experimental results from other researchers
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On the size Effect for micro-scale structures under the plane bulge test using the modified strain gradient theory
International Journal of Precision Engineering and Manufacturing, 2011Co-Authors: Hun-kee Lee, Bong-bu Jung, Dongseob Kim, Hyun-chul ParkAbstract:A modified strain gradient theory is proposed based on the nonhomogeneity of polycrystalline metallic materials. Geometrically necessary dislocations are generated on the slip planes as well as on the grain boundary to accommodate deformation with minimum internal stress. Since amount of the geometrically necessary dislocation depends on the deformation shape, specimen size and grain size, it is an important factor for the modified strain gradient theory and the size Effect. This new theory differs from the mechanism based strain gradient plasticity in its consideration of the geometrically necessary dislocations on the grain boundary and Free Surface Effect. This theory provides a possible explanation for conflicting size Effect: the smaller can be either harder or softer due to the deformation. Using the proposed theory, analysis of the Effect of both specimen and grain size under the plane bulge test of polycrystalline materials is performed.
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Analysis of the Effect of both specimen size and grain size on the tensile strength of the polycrystalline metallic materials
Nanosensors Biosensors and Info-Tech Sensors and Systems 2010, 2010Co-Authors: Bong-bu Jung, Hun-kee Lee, Hyun-chul ParkAbstract:A modified strain gradient plasticity theory is proposed based on the mechanism-based strain gradient (MSG) plasticity. This study is motivated by nonhomogeneity of polycrystalline materials. We believe that the geometrically necessary dislocations (GND) are generated on slip system as well as grain boundary to accommodate the deformation shape with internal stress. The new theory differs from the MSG plasticity in consideration of the GND on grain boundary and Free Surface Effect of polycrystalline materials. A model describing the size Effect on the tensile strength of crystalline metallic materials is investigated. Using the nonhomogeneity of polycrystalline materials and Free Surface Effect, the density of the geometrically necessary dislocations during tension is derived. Using the proposed model, an analysis of the Effect of both specimen size and grain size on the tensile strength of the polycrystalline materials is carried out.
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Analysis of flow stress and size Effect on polycrystalline metallic materials in tension
Materials Science and Engineering: A, 2009Co-Authors: Hun-kee Lee, Bong-bu Jung, Youngdeuk Kim, Woonbong Hwang, Hyun-chul ParkAbstract:A model describing the size Effect on the tensile strength of crystalline metallic materials is investigated. Using the nonhomogeneity of polycrystalline materials and Free Surface Effect, the density of the geometrically necessary dislocations during tension is derived. Using the proposed model, an analysis of the Effect of both specimen size and grain size on the tensile strength of the polycrystalline metallic materials is carried out.
Shin Nishimura - One of the best experts on this subject based on the ideXlab platform.
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Local kinetics of cavitation in hydrogen-exposed EPDM using in-situ X-Ray tomography: focus on Free Surface Effect and cavity interaction
Polymer Testing, 2020Co-Authors: Mahak Fazal, Sylvie Castagnet, Azdine Nait-ali, Shin NishimuraAbstract:Decompression failure in high-pressure gas exposed rubbers has almost only been studied at a global scale so far. In the present study in hydrogen-exposed EPDM, the growth kinetics of cavities was visualized and quantified for the first time at the cavity scale using 3D in-situ Xray micro-tomography with an emphasis on interaction Effects and boundary conditions. The volume evolution of cavities was processed and the inflation rate and maximum volume were calculated. The boundary conditions of selected cavities was analysed in terms of distance to the Free Surface as well as distance to other cavities. Proximity to the Free Surface was found to be a driving force for evolution of cavities up to a certain value beyond which the growth kinetics are more driven by other factors such as time of nucleation. No clear interaction Effect was pointed out between cavities with the current spatial resolution.
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Local kinetics of cavitation in hydrogen-exposed EPDM using in-situ X-Ray tomography: Focus on Free Surface Effect and cavity interaction
Polymer Testing, 2020Co-Authors: Mahak Fazal, Sylvie Castagnet, Azdine Nait-ali, Shin NishimuraAbstract:Abstract Decompression failure in high-pressure gas exposed rubbers has almost only been studied at a global scale so far. In the present study in hydrogen-exposed EPDM, the growth kinetics of cavities was visualized and quantified at the cavity scale using 3D in-situ X-ray micro-tomography with an emphasis on interaction Effects and boundary conditions. The volume evolution of cavities was processed and the inflation rate and maximum volume were calculated. The boundary conditions of selected cavities was analysed in terms of distance to the Free Surface as well as distance to other cavities. Proximity to the Free Surface was found to be a driving force for evolution of cavities up to a certain range beyond which the growth kinetics are more driven by other factors such as time of nucleation. Within the range made accessible by the current spatial resolution, no clear interaction Effect was pointed out between close cavities.
Boo Cheong Khoo - One of the best experts on this subject based on the ideXlab platform.
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Numerical investigation on Free Surface Effect on the supercavitating flow over a low aspect ratio wedge-shaped hydrofoil
Journal of Hydrodynamics, 2020Co-Authors: Boo Cheong KhooAbstract:In this study, the Effect of the Free Surface on the supercavitating flow that surrounds a low aspect ratio wedge-shaped hydrofoil is studied based on computational fluid dynamics (CFD), with Cartesian cut-cell mesh method. The volume of fraction (VOF) method and the k - e turbulence model with the Schnerr Sauer cavitation model are used for simulating the supercavitation in turbulent flow. Both quasi-3-D and full-3-D cases are considered. The quasi-3-D simulation results are compared with the previous water tunnel experimental data and analytical data, and the results agree well with each other. The results are presented for a wide range of submerged distance in terms of the Free Surface Effect on the cavity shape, wave elevation and force coefficients. The range of the Free Surface Effect is found. The simulation results show that the cavitating flow around the hydrofoil become shorter and thicker as the submerge depth decreases. As the aspect ratio of the hydrofoil studied in the full-3-D cases is low, the 3-D Effect on the supercavitating flow is strong. The relationship between the flow patterns and vortex structures is also revealed from the numerical results.
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Numerical investigation on Free Surface Effect on the supercavitating flow over a low aspect ratio wedge-shaped hydrofoil
Journal of Hydrodynamics, 2020Co-Authors: Boo Cheong KhooAbstract:In this study, the Effect of the Free Surface on the supercavitating flow that surrounds a low aspect ratio wedge-shaped hydrofoil is studied based on computational fluid dynamics (CFD), with Cartesian cut-cell mesh method. The volume of fraction (VOF) method and the k - ε turbulence model with the Schnerr Sauer cavitation model are used for simulating the supercavitation in turbulent flow. Both quasi-3-D and full-3-D cases are considered. The quasi-3-D simulation results are compared with the previous water tunnel experimental data and analytical data, and the results agree well with each other. The results are presented for a wide range of submerged distance in terms of the Free Surface Effect on the cavity shape, wave elevation and force coefficients. The range of the Free Surface Effect is found. The simulation results show that the cavitating flow around the hydrofoil become shorter and thicker as the submerge depth decreases. As the aspect ratio of the hydrofoil studied in the full-3-D cases is low, the 3-D Effect on the supercavitating flow is strong. The relationship between the flow patterns and vortex structures is also revealed from the numerical results.
