The Experts below are selected from a list of 2214 Experts worldwide ranked by ideXlab platform
Valery I Levitas - One of the best experts on this subject based on the ideXlab platform.
-
Plastic flows and Strain induced alpha to omega phase transformation in zirconium during compression in a diamond anvil cell finite element simulations
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017Co-Authors: Biao Feng, Valery I LevitasAbstract:Abstract Coupled Plastic flows and the Strain-induced α → ω phase transformation (PT) in a zirconium sample under compression in a diamond anvil cell are investigated using finite element method (FEM). The PT is treated as Strain-induced rather than pressure-induced and the previously developed model for Strain-induced PTs is utilized. Very heterogeneous fields of stress tensor, Accumulated Plastic Strain, and concentration of the ω phase are obtained for different applied loads. The PT starts at the center of a sample when pressure exceeds the minimum pressure p e d = 1.7 G P a , below which a direct Strain-induced PT to a high pressure phase cannot occur, and it propagates from the center to the periphery with an increasing load. Even at the maximum pressure of 7 GPa, the PT is not completed everywhere. With an increasing load, the pressure and pressure gradient along the radial direction significantly increase in the two-phase region due to the much larger yield strength of the ω phase. This in turn promotes transformation and produces a positive mechanochemical feedback. Obtained results are utilized for the interpretation of published experimental data on pressure-, stress-, and Strain-induced α → ω PTs in Zr and Titanium (Ti) and α → β and ω → β PTs in Zr under compression and high pressure torsion. This includes correcting the reported minimum pressures for these transformations by a factor of 3–6 due to the stress heterogeneity, the effect of transmitting media, the pressure hysteresis, and the reversibility of the transformation.
-
Plastic flows and Strain induced alpha to omega phase transformation in zirconium during compression in a diamond anvil cell finite element simulations
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017Co-Authors: Biao Feng, Valery I LevitasAbstract:Abstract Coupled Plastic flows and the Strain-induced α → ω phase transformation (PT) in a zirconium sample under compression in a diamond anvil cell are investigated using finite element method (FEM). The PT is treated as Strain-induced rather than pressure-induced and the previously developed model for Strain-induced PTs is utilized. Very heterogeneous fields of stress tensor, Accumulated Plastic Strain, and concentration of the ω phase are obtained for different applied loads. The PT starts at the center of a sample when pressure exceeds the minimum pressure p e d = 1.7 G P a , below which a direct Strain-induced PT to a high pressure phase cannot occur, and it propagates from the center to the periphery with an increasing load. Even at the maximum pressure of 7 GPa, the PT is not completed everywhere. With an increasing load, the pressure and pressure gradient along the radial direction significantly increase in the two-phase region due to the much larger yield strength of the ω phase. This in turn promotes transformation and produces a positive mechanochemical feedback. Obtained results are utilized for the interpretation of published experimental data on pressure-, stress-, and Strain-induced α → ω PTs in Zr and Titanium (Ti) and α → β and ω → β PTs in Zr under compression and high pressure torsion. This includes correcting the reported minimum pressures for these transformations by a factor of 3–6 due to the stress heterogeneity, the effect of transmitting media, the pressure hysteresis, and the reversibility of the transformation.
-
modeling and simulation of Strain induced phase transformations under compression in a diamond anvil cell
Physical Review B, 2010Co-Authors: Valery I Levitas, Oleg M ZarechnyyAbstract:Strain-induced phase transformations (PTs) under high-pressure differ fundamentally from the pressure-induced PTs under quasihydrostatic conditions. A model and finite-element approach to Strain-induced PTs under compression and torsion of a sample in rotational diamond anvil cell are developed. The current paper is devoted to the numerical study of Strain-induced PTs under compression in traditional diamond anvils while the accompanying paper [V. I. Levitas and O. M. Zarechnyy, Phys. Rev. B 82, 174124 (2010)] is concerned with compression and torsion in rotational anvils. Very heterogeneous fields of stress tensor, Accumulated Plastic Strain, and concentration of the high-pressure phase are determined for three ratios of yield strengths of low-pressure and high-pressure phases. PT kinetics depends drastically on the yield strengths ratios. For a stronger high-pressure phase, an increase in strength during PT increases pressure and promotes PT, serving as a positive mechanochemical feedback; however, maximum pressure in a sample is much larger than required for PT. For a weaker high-pressure phase, strong Strain and high-pressure phase localization and irregular stress fields are obtained. Various experimentally observed effects are reproduced and interpreted. Obtained results revealed difficulties in experimental characterization of Strain-induced PTs and suggested some ways to overcome them.
Volodymyr Okorokov - One of the best experts on this subject based on the ideXlab platform.
-
new formulation of nonlinear kinematic hardening model part ii cyclic hardening softening and ratcheting
International Journal of Plasticity, 2019Co-Authors: Volodymyr Okorokov, Yevgen Gorash, Donald Mackenzie, Ralph Van RijswickAbstract:Abstract The second part of the study presents development of the Dirac delta functions framework to modelling of cyclic hardening and softening of material during cyclic loading conditions for the investigated in Part I low carbon S355J2 steel. A new criterion of Plastic Strain range change is formulated. This provides more certainty in the cyclic Plasticity modelling framework compared to classical Plastic Strain memorization modelling. Two hardening parameters from the developed kinematic hardening rule are written as functions of both Plastic Strain range and previously Accumulated Plastic Strain. This representation of hardening parameters is able to accurately match experimental results with different types of loading programs including random loading conditions and considering initial monotonic behaviour with yield plateau deformation. Ratcheting behaviour is simulated by the developed cyclic Plasticity framework by considering an approximated form of the Dirac delta function for modelling the deviation effect and introducing an additional supersurface for better prediction of ratcheting rate. The proposed cyclic Plasticity model requires up to 21 material constants, depending on application. A clear and straightforward calibration procedure, where sets of material constants are determined for each Plasticity phenomenon considered, is presented. Application of the model to different materials under various tension-compression and non-proportional axial-torsion cycles shows very close agreement with test results.
-
New formulation of nonlinear kinematic hardening model, part II: cyclic hardening/softening and ratcheting
International Journal of Plasticity, 2019Co-Authors: Volodymyr Okorokov, Yevgen Gorash, Donald Mackenzie, Ralph Van RijswickAbstract:Abstract The second part of the study presents development of the Dirac delta functions framework to modelling of cyclic hardening and softening of material during cyclic loading conditions for the investigated in Part I low carbon S355J2 steel. A new criterion of Plastic Strain range change is formulated. This provides more certainty in the cyclic Plasticity modelling framework compared to classical Plastic Strain memorization modelling. Two hardening parameters from the developed kinematic hardening rule are written as functions of both Plastic Strain range and previously Accumulated Plastic Strain. This representation of hardening parameters is able to accurately match experimental results with different types of loading programs including random loading conditions and considering initial monotonic behaviour with yield plateau deformation. Ratcheting behaviour is simulated by the developed cyclic Plasticity framework by considering an approximated form of the Dirac delta function for modelling the deviation effect and introducing an additional supersurface for better prediction of ratcheting rate. The proposed cyclic Plasticity model requires up to 21 material constants, depending on application. A clear and straightforward calibration procedure, where sets of material constants are determined for each Plasticity phenomenon considered, is presented. Application of the model to different materials under various tension-compression and non-proportional axial-torsion cycles shows very close agreement with test results.
Ralph Van Rijswick - One of the best experts on this subject based on the ideXlab platform.
-
New formulation of nonlinear kinematic hardening model, part II: cyclic hardening/softening and ratcheting
International Journal of Plasticity, 2019Co-Authors: Volodymyr Okorokov, Yevgen Gorash, Donald Mackenzie, Ralph Van RijswickAbstract:Abstract The second part of the study presents development of the Dirac delta functions framework to modelling of cyclic hardening and softening of material during cyclic loading conditions for the investigated in Part I low carbon S355J2 steel. A new criterion of Plastic Strain range change is formulated. This provides more certainty in the cyclic Plasticity modelling framework compared to classical Plastic Strain memorization modelling. Two hardening parameters from the developed kinematic hardening rule are written as functions of both Plastic Strain range and previously Accumulated Plastic Strain. This representation of hardening parameters is able to accurately match experimental results with different types of loading programs including random loading conditions and considering initial monotonic behaviour with yield plateau deformation. Ratcheting behaviour is simulated by the developed cyclic Plasticity framework by considering an approximated form of the Dirac delta function for modelling the deviation effect and introducing an additional supersurface for better prediction of ratcheting rate. The proposed cyclic Plasticity model requires up to 21 material constants, depending on application. A clear and straightforward calibration procedure, where sets of material constants are determined for each Plasticity phenomenon considered, is presented. Application of the model to different materials under various tension-compression and non-proportional axial-torsion cycles shows very close agreement with test results.
Ralph Van Rijswick - One of the best experts on this subject based on the ideXlab platform.
-
new formulation of nonlinear kinematic hardening model part ii cyclic hardening softening and ratcheting
International Journal of Plasticity, 2019Co-Authors: Volodymyr Okorokov, Yevgen Gorash, Donald Mackenzie, Ralph Van RijswickAbstract:Abstract The second part of the study presents development of the Dirac delta functions framework to modelling of cyclic hardening and softening of material during cyclic loading conditions for the investigated in Part I low carbon S355J2 steel. A new criterion of Plastic Strain range change is formulated. This provides more certainty in the cyclic Plasticity modelling framework compared to classical Plastic Strain memorization modelling. Two hardening parameters from the developed kinematic hardening rule are written as functions of both Plastic Strain range and previously Accumulated Plastic Strain. This representation of hardening parameters is able to accurately match experimental results with different types of loading programs including random loading conditions and considering initial monotonic behaviour with yield plateau deformation. Ratcheting behaviour is simulated by the developed cyclic Plasticity framework by considering an approximated form of the Dirac delta function for modelling the deviation effect and introducing an additional supersurface for better prediction of ratcheting rate. The proposed cyclic Plasticity model requires up to 21 material constants, depending on application. A clear and straightforward calibration procedure, where sets of material constants are determined for each Plasticity phenomenon considered, is presented. Application of the model to different materials under various tension-compression and non-proportional axial-torsion cycles shows very close agreement with test results.
Yevgen Gorash - One of the best experts on this subject based on the ideXlab platform.
-
new formulation of nonlinear kinematic hardening model part ii cyclic hardening softening and ratcheting
International Journal of Plasticity, 2019Co-Authors: Volodymyr Okorokov, Yevgen Gorash, Donald Mackenzie, Ralph Van RijswickAbstract:Abstract The second part of the study presents development of the Dirac delta functions framework to modelling of cyclic hardening and softening of material during cyclic loading conditions for the investigated in Part I low carbon S355J2 steel. A new criterion of Plastic Strain range change is formulated. This provides more certainty in the cyclic Plasticity modelling framework compared to classical Plastic Strain memorization modelling. Two hardening parameters from the developed kinematic hardening rule are written as functions of both Plastic Strain range and previously Accumulated Plastic Strain. This representation of hardening parameters is able to accurately match experimental results with different types of loading programs including random loading conditions and considering initial monotonic behaviour with yield plateau deformation. Ratcheting behaviour is simulated by the developed cyclic Plasticity framework by considering an approximated form of the Dirac delta function for modelling the deviation effect and introducing an additional supersurface for better prediction of ratcheting rate. The proposed cyclic Plasticity model requires up to 21 material constants, depending on application. A clear and straightforward calibration procedure, where sets of material constants are determined for each Plasticity phenomenon considered, is presented. Application of the model to different materials under various tension-compression and non-proportional axial-torsion cycles shows very close agreement with test results.
-
New formulation of nonlinear kinematic hardening model, part II: cyclic hardening/softening and ratcheting
International Journal of Plasticity, 2019Co-Authors: Volodymyr Okorokov, Yevgen Gorash, Donald Mackenzie, Ralph Van RijswickAbstract:Abstract The second part of the study presents development of the Dirac delta functions framework to modelling of cyclic hardening and softening of material during cyclic loading conditions for the investigated in Part I low carbon S355J2 steel. A new criterion of Plastic Strain range change is formulated. This provides more certainty in the cyclic Plasticity modelling framework compared to classical Plastic Strain memorization modelling. Two hardening parameters from the developed kinematic hardening rule are written as functions of both Plastic Strain range and previously Accumulated Plastic Strain. This representation of hardening parameters is able to accurately match experimental results with different types of loading programs including random loading conditions and considering initial monotonic behaviour with yield plateau deformation. Ratcheting behaviour is simulated by the developed cyclic Plasticity framework by considering an approximated form of the Dirac delta function for modelling the deviation effect and introducing an additional supersurface for better prediction of ratcheting rate. The proposed cyclic Plasticity model requires up to 21 material constants, depending on application. A clear and straightforward calibration procedure, where sets of material constants are determined for each Plasticity phenomenon considered, is presented. Application of the model to different materials under various tension-compression and non-proportional axial-torsion cycles shows very close agreement with test results.