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Xu Chen - One of the best experts on this subject based on the ideXlab platform.
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cyclic deformation of 316l stainless steel and constitutive modeling under non proportional variable loading path
International Journal of Plasticity, 2019Co-Authors: Ruisi Xing, Shouwen Shi, Xu ChenAbstract:Abstract In order to investigate the effect of non-proportional loading history on cyclic deformation of 316L stainless steel, a series of multiaxial cyclic experiments with variable loading path are conducted at room temperature. It is found that the materials exhibit cyclic Hardening at initial stage, followed by a long period of cyclic softening. Significant cyclic softening is observed when non-proportional loading path changes into proportional loading path and the rate of cyclic softening is related to non-proportional loading history. A visco-plasticity constitutive model based on Ohno-Wang kinematic Hardening Rule and Marquis isotropic Hardening Rule is used to characterize non-proportional cyclic behavior. Simulation results agree with experiments very well in terms of cyclic Hardening effects. However, this model is found to be less effective in simulating cyclic softening effect, especially considering the influence of non-proportional loading history. A modified isotropic Hardening model is thus proposed to simulate the cyclic softening behavior of 316L stainless steel by introducing a memory non-proportionality and qualifying a partial recoverable softening term of isotropic Hardening Rule. Simulation results of the proposed model agree much better with experimental values.
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thermo viscoplastic modeling incorporating dynamic strain aging effect on the uniaxial behavior of z2cnd18 12n stainless steel
International Journal of Plasticity, 2012Co-Authors: Xu Chen, Gang ChenAbstract:Abstract Monotonic tension, isothermal/anisothermal fully reversed strain cycling and zero-to-tension cyclic tests were conducted within the temperature domain from room temperature to 823 K to investigate the mechanical behavior of Z2CND18.12N austenitic stainless steel under various uniaxial loading conditions. Interesting results were observed from these tests, including obvious rate-dependence at room temperature but lack of rate-dependence at elevated temperatures with the occurrence of serrated flow stress in tensile tests, more cyclic Hardening at higher temperature in strain cycling tests, and tendency to reach shakedown condition at elevated temperatures in zero-to-tension cyclic tests. Dynamic strain aging (DSA) effect was presumably believed to contribute to these characteristics of the material. A thermo-viscoplastic constitutive model was proposed to describe the mechanical behavior of the material under uniaxial loading conditions at small strains. Kinematic Hardening Rule with two components of back stress and isotropic Hardening Rule incorporating DSA effect are the novel features of the proposed model. The simulated and predicted results show reasonable agreement with the experimental data.
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visco plastic constitutive modeling on ohno wang kinematic Hardening Rule for uniaxial ratcheting behavior of z2cnd18 12n steel
International Journal of Plasticity, 2012Co-Authors: Gang Chen, Xu ChenAbstract:Abstract Experimental results of monotonic uniaxial tensile tests at different strain rates and the reversed strain cycling test showed the characteristics of rate-dependence and cyclic Hardening of Z2CND18.12N austenitic stainless steel at room temperature, respectively. Based on the Ohno–Wang kinematic Hardening Rule, a visco-plastic constitutive model incorporated with isotropic Hardening was developed to describe the uniaxial ratcheting behavior of Z2CND18.12N steel under various stress-controlled loading conditions. Predicted results of the developed model agreed better with experimental results when the ratcheting strain level became higher, but the developed model overestimated the ratcheting deformation in other cases. A modified model was proposed to improve the prediction accuracy. In the modified model, the parameter m i of the Ohno–Wang kinematic Hardening Rule was developed to evolve with the accumulated plastic strain. Simulation results of the modified model proved much better agreement with experiments.
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modified kinematic Hardening Rule for multiaxial ratcheting prediction
International Journal of Plasticity, 2004Co-Authors: Xu Chen, Rong JiaoAbstract:Abstract A modified kinematic Hardening Rule is proposed in which one biaxial loading dependent parameter δ′ connecting the radial evanescence term [(α:n)ndp] in the Burlet–Cailletaud model with the dynamic recovery term of Ohno–Wang kinematic Hardening Rule is introduced into the framework of the Ohno–Wang model. Compared with multiaxial ratcheting experimental data obtained on 1Cr18Ni9Ti stainless steel in the paper and CS1026 steel conducted by Hassan et al. [Int. J. Plasticity 8 (1992) 117], simulation results by modified model are quite well in all loading paths. The simulations of initial nonlinear part in ratcheting curves can be improved greatly while the evolutional parameter δ′ related to plastic strain accumulation is added into the modified model.
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modified kinematic Hardening Rule for multiaxial ratcheting prediction
International Journal of Plasticity, 2004Co-Authors: Xu Chen, Rong JiaoAbstract:A modified kinematic Hardening Rule is proposed in which one biaxial loading dependent parameter� 0 connecting the radial evanescence term [(� :n)ndp] in the Burlet–Cailletaud model with the dynamic recovery term of Ohno–Wang kinematic Hardening Rule is introduced into the framework of the Ohno–Wang model. Compared with multiaxial ratcheting experimental data obtained on 1Cr18Ni9Ti stainless steel in the paper and CS1026 steel conducted by Hassan et al. [Int. J. Plasticity 8 (1992) 117], simulation results by modified model are quite well in all loading paths. The simulations of initial nonlinear part in ratcheting curves can be improved greatly while the evolutional parameter � 0 related to plastic strain accumulation is added into the modified model. # 2003 Published by Elsevier Ltd.
A R Khoei - One of the best experts on this subject based on the ideXlab platform.
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a three invariant cap model with isotropic kinematic Hardening Rule and associated plasticity for granular materials
International Journal of Solids and Structures, 2008Co-Authors: H Dormohammadi, A R KhoeiAbstract:Abstract In this paper, a three-invariant cap model is developed for the isotropic–kinematic Hardening and associated plasticity of granular materials. The model is based on the concepts of elasticity and plasticity theories together with an associated flow Rule and a work Hardening law for plastic deformations of granulars. The Hardening Rule is defined by its decomposition into the isotropic and kinematic material functions. The constitutive elasto-plastic matrix and its components are derived by using the definition of yield surface, material functions and non-linear elastic behavior, as function of Hardening parameters. The model assessment and procedure for determination of material parameters are described. Finally, the applicability of proposed plasticity model is demonstrated in numerical simulation of several triaxial and confining pressure tests on different granular materials, including: wheat, rape, synthetic granulate and sand.
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a three invariant cap plasticity with isotropic kinematic Hardening Rule for powder materials model assessment and parameter calibration
Computational Materials Science, 2007Co-Authors: A R Khoei, H DormohammadiAbstract:Abstract The constitutive modeling of powder is clearly a keystone of successful quantitative solution possibilities. Without a reasonable constitutive model, which can reproduce complicated powder behavior under loading conditions, the computations are worthless. In this paper, a three-invariant cap plasticity model with isotropic–kinematic Hardening Rule is presented for powder materials. A generalized single-cap plasticity is developed which can be compared with some common double-surface plasticity models proposed for powders in literature. The Hardening Rule is defined based on the isotropic and kinematic material functions. The constitutive elasto-plastic matrix and its components are derived by using the definition of yield surface, material functions and nonlinear elastic behavior, as function of Hardening parameters. The procedure for determination of material parameters is described. Finally, the applicability of the proposed model is demonstrated in numerical simulation of triaxial and confining pressure tests.
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a three invariant cap plasticity model with kinematic Hardening Rule for powder materials
Journal of Materials Processing Technology, 2007Co-Authors: A R Khoei, H Dormohammadi, A R AzamiAbstract:Abstract In this paper, a three-invariant cap plasticity with a kinematic Hardening Rule is presented for powder materials. A general form is developed for the cap plasticity which can be compared with some common double-surface plasticity models proposed for powders in literature. The constitutive elasto-plastic matrix and its components are derived based on the definition of yield surface, Hardening parameter and non-linear elastic behavior, as function of relative density of powder. The procedure for determination of powder parameters is described. Finally, the applicability of the proposed model is demonstrated in numerical simulation of triaxial and confining pressure tests.
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a single cone cap plasticity with an isotropic Hardening Rule for powder materials
International Journal of Mechanical Sciences, 2005Co-Authors: A R Khoei, A R AzamiAbstract:Abstract In this paper, a new single cone-cap plasticity with an isotropic Hardening Rule is presented for powder materials. A general form is developed for the cap plasticity, which can be compared with some common double-surface plasticity models proposed for powders in literature. The constitutive elasto-plastic matrix and its components are derived based on the definition of yield surface, Hardening parameter and nonlinear elastic behavior, as a function of relative density of powder. Different aspects of the model are illustrated and the procedure for determination of powder parameters is described. Finally, the applicability of the proposed model is demonstrated in numerical simulation of triaxial and confining pressure tests.
Jwo Pan - One of the best experts on this subject based on the ideXlab platform.
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effects of pressure sensitive yielding on stress distributions in crankshaft sections under fillet rolling and bending fatigue tests
International Journal of Fatigue, 2009Co-Authors: K S Choi, Jwo PanAbstract:Abstract In this paper, the evolution equation for the active yield surface during the unloading/reloading process based on the Drucker–Prager yield function and a recently developed anisotropic Hardening Rule is first presented. A user material subroutine based on the anisotropic Hardening Rule and the constitutive relation was written and implemented into the commercial finite element program ABAQUS. Computations were first conducted for a simple plane strain finite element model under uniaxial monotonic and cyclic loading conditions. The results indicate that the anisotropic Hardening Rule with the non-associated flow Rule describes well the strength-differential effect and the asymmetric closed hysteresis loops as observed in the uniaxial cyclic loading tests of cast irons. Then, a two-dimensional plane strain finite element analysis of a crankshaft section under fillet rolling and subsequent bending was conducted. For the pressure sensitivity corresponding to the cast iron crankshaft of interest, the critical locations for fatigue crack initiation according to the stress distributions for pressure-sensitive materials agree with the experimental observations in bending fatigue tests of crankshaft sections.
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a generalized anisotropic Hardening Rule based on the mroz multi yield surface model for pressure insensitive and sensitive materials
International Journal of Plasticity, 2009Co-Authors: Kyoo Sil Choi, Jwo PanAbstract:Abstract In this paper, a generalized anisotropic Hardening Rule based on the Mroz multi-yield-surface model for pressure insensitive and sensitive materials is derived. The evolution equation for the active yield surface with reference to the memory yield surface is obtained by considering the continuous expansion of the active yield surface during the unloading/reloading process. The incremental constitutive relation based on the associated flow Rule is then derived for a general yield function for pressure insensitive and sensitive materials. Detailed incremental constitutive relations for materials based on the Mises yield function, the Hill quadratic anisotropic yield function and the Drucker–Prager yield function are derived as the special cases. The closed-form solutions for one-dimensional stress–plastic strain curves are also derived and plotted for materials under cyclic loading conditions based on the three yield functions. In addition, the closed-form solutions for one-dimensional stress–plastic strain curves for materials based on the isotropic Cazacu–Barlat yield function under cyclic loading conditions are summarized and presented. For materials based on the Mises and the Hill anisotropic yield functions, the stress–plastic strain curves show closed hysteresis loops under uniaxial cyclic loading conditions and the Masing hypothesis is applicable. For materials based on the Drucker–Prager and Cazacu–Barlat yield functions, the stress–plastic strain curves do not close and show the ratcheting effect under uniaxial cyclic loading conditions. The ratcheting effect is due to different strain ranges for a given stress range for the unloading and reloading processes. With these closed-form solutions, the important effects of the yield surface geometry on the cyclic plastic behavior due to the pressure-sensitive yielding or the unsymmetric behavior in tension and compression can be shown unambiguously. The closed form solutions for the Drucker–Prager and Cazacu–Barlat yield functions with the associated flow Rule also suggest that a more general anisotropic Hardening theory needs to be developed to address the ratcheting effects for a given stress range.
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an anisotropic Hardening Rule with non associated flow Rule for pressure sensitive materials
ASME 2009 Pressure Vessels and Piping Conference, 2009Co-Authors: K S Choi, Jwo PanAbstract:In this paper, cyclic plastic behaviors of pressure-sensitive materials based on an anisotropic Hardening Rule with two non-associated flow Rules are examined. The Drucker-Prager pressure-sensitive yield function and the Mises plastic potential function are adopted to explore the cyclic plastic behaviors of pressure-sensitive materials or strength-differential materials. The constitutive relations are formulated for the initial loading and unloading/reloading processes based on the anisotropic Hardening Rule of Choi and Pan [1]. Non-associated flow Rules are employed to derive closed-form stress-plastic strain relations under uniaxial cyclic loading conditions. The stress-plastic strain curves based on a conventional non-associated flow Rule do not close, and show a significant ratcheting under uniaxial cyclic loading conditions. A new non-conventional non-associated flow Rule is then formulated based on observed nearly closed hysteresis loops of pressure-sensitive materials. The stress-plastic strain curves based on the non-conventional non-associated flow Rule show closed hysteresis loops under uniaxial cyclic loading conditions. The results indicate that the anisotropic Hardening Rule with the non-conventional non-associated flow Rule describes well the strength-differential effect and the asymmetric closed hysteresis loops as observed in the uniaxial cyclic loading tests of pressure-sensitive materials.Copyright © 2009 by ASME
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a generalized anisotropic Hardening Rule based on the mroz multi yield surface model
ASME 2008 Pressure Vessels and Piping Conference PVP2008, 2008Co-Authors: K S Choi, Jwo PanAbstract:In this paper, a generalized anisotropic Hardening Rule based on the Mroz multi-yield-surface model is derived. The evolution equation for the active yield surface is obtained by considering the continuous expansion of the active yield surface during the unloading/reloading process. The incremental constitutive relation based on the associated flow Rule is then derived for a general yield function. As a special case, detailed incremental constitutive relations are derived for the Mises yield function. The closed-form solutions for one-dimensional stress-plastic strain curves are also derived and plotted for the Mises materials under cyclic loading conditions. The stress-plastic strain curves show closed hysteresis loops under uniaxial cyclic loading conditions and the Masing hypothesis is applicable. A user material subroutine based on the Mises yield function, the anisotropic Hardening Rule and the constitutive relations was then written and implemented into ABAQUS. Computations were conducted for a simple plane strain finite element model under uniaxial monotonic and cyclic loading conditions based on the anisotropic Hardening Rule and the isotropic and nonlinear kinematic Hardening Rules of ABAQUS. The results indicate that the plastic response of the material follows the intended input stress-strain data for the anisotropic Hardening Rule whereas the plastic response depends upon the input strain ranges of the stress-strain data for the nonlinear kinematic Hardening Rule.Copyright © 2008 by ASME
H Dormohammadi - One of the best experts on this subject based on the ideXlab platform.
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a three invariant cap model with isotropic kinematic Hardening Rule and associated plasticity for granular materials
International Journal of Solids and Structures, 2008Co-Authors: H Dormohammadi, A R KhoeiAbstract:Abstract In this paper, a three-invariant cap model is developed for the isotropic–kinematic Hardening and associated plasticity of granular materials. The model is based on the concepts of elasticity and plasticity theories together with an associated flow Rule and a work Hardening law for plastic deformations of granulars. The Hardening Rule is defined by its decomposition into the isotropic and kinematic material functions. The constitutive elasto-plastic matrix and its components are derived by using the definition of yield surface, material functions and non-linear elastic behavior, as function of Hardening parameters. The model assessment and procedure for determination of material parameters are described. Finally, the applicability of proposed plasticity model is demonstrated in numerical simulation of several triaxial and confining pressure tests on different granular materials, including: wheat, rape, synthetic granulate and sand.
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a three invariant cap plasticity with isotropic kinematic Hardening Rule for powder materials model assessment and parameter calibration
Computational Materials Science, 2007Co-Authors: A R Khoei, H DormohammadiAbstract:Abstract The constitutive modeling of powder is clearly a keystone of successful quantitative solution possibilities. Without a reasonable constitutive model, which can reproduce complicated powder behavior under loading conditions, the computations are worthless. In this paper, a three-invariant cap plasticity model with isotropic–kinematic Hardening Rule is presented for powder materials. A generalized single-cap plasticity is developed which can be compared with some common double-surface plasticity models proposed for powders in literature. The Hardening Rule is defined based on the isotropic and kinematic material functions. The constitutive elasto-plastic matrix and its components are derived by using the definition of yield surface, material functions and nonlinear elastic behavior, as function of Hardening parameters. The procedure for determination of material parameters is described. Finally, the applicability of the proposed model is demonstrated in numerical simulation of triaxial and confining pressure tests.
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a three invariant cap plasticity model with kinematic Hardening Rule for powder materials
Journal of Materials Processing Technology, 2007Co-Authors: A R Khoei, H Dormohammadi, A R AzamiAbstract:Abstract In this paper, a three-invariant cap plasticity with a kinematic Hardening Rule is presented for powder materials. A general form is developed for the cap plasticity which can be compared with some common double-surface plasticity models proposed for powders in literature. The constitutive elasto-plastic matrix and its components are derived based on the definition of yield surface, Hardening parameter and non-linear elastic behavior, as function of relative density of powder. The procedure for determination of powder parameters is described. Finally, the applicability of the proposed model is demonstrated in numerical simulation of triaxial and confining pressure tests.
K S Choi - One of the best experts on this subject based on the ideXlab platform.
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effects of pressure sensitive yielding on stress distributions in crankshaft sections under fillet rolling and bending fatigue tests
International Journal of Fatigue, 2009Co-Authors: K S Choi, Jwo PanAbstract:Abstract In this paper, the evolution equation for the active yield surface during the unloading/reloading process based on the Drucker–Prager yield function and a recently developed anisotropic Hardening Rule is first presented. A user material subroutine based on the anisotropic Hardening Rule and the constitutive relation was written and implemented into the commercial finite element program ABAQUS. Computations were first conducted for a simple plane strain finite element model under uniaxial monotonic and cyclic loading conditions. The results indicate that the anisotropic Hardening Rule with the non-associated flow Rule describes well the strength-differential effect and the asymmetric closed hysteresis loops as observed in the uniaxial cyclic loading tests of cast irons. Then, a two-dimensional plane strain finite element analysis of a crankshaft section under fillet rolling and subsequent bending was conducted. For the pressure sensitivity corresponding to the cast iron crankshaft of interest, the critical locations for fatigue crack initiation according to the stress distributions for pressure-sensitive materials agree with the experimental observations in bending fatigue tests of crankshaft sections.
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simulations of stress distributions in crankshaft sections under fillet rolling and bending fatigue tests
International Journal of Fatigue, 2009Co-Authors: K S ChoiAbstract:Abstract The residual stresses due to fillet rolling and the bending stresses near the fillets of crankshaft sections under bending fatigue tests are important driving forces to determine the bending fatigue limits of crankshafts. In this paper, the residual stresses and the bending stresses near the fillet of a crankshaft section under fillet rolling and subsequent bending fatigue tests are investigated by a two-dimensional plane strain finite element analysis based on the anisotropic Hardening Rule of Choi and Pan [Choi KS, Pan J. A generalized anisotropic Hardening Rule based on the Mroz multi-yield-surface model for pressure insensitive and sensitive materials (in preparation)]. The evolution equation for the active yield surface during the unloading/reloading process is first presented based on the anisotropic Hardening Rule of Choi and Pan (in preparation) and the Mises yield function. The tangent modulus procedure of Peirce et al. [Peirce D, Shih CF, Needleman A. A tangent modulus method for rate dependent solids. Comput Struct 1984;18:875–87] for rate-sensitive materials is adopted to derive the constitutive relation. A user material subroutine based on the anisotropic Hardening Rule and the constitutive relation was written and implemented into ABAQUS. Computations were first conducted for a simple plane strain finite element model under uniaxial monotonic and cyclic loading conditions based on the anisotropic Hardening Rule, the isotropic and nonlinear kinematic Hardening Rules of ABAQUS. The results indicate that the plastic response of the material follows the intended input stress–strain data for the anisotropic Hardening Rule whereas the plastic response depends upon the input strain ranges of the stress–strain data for the nonlinear kinematic Hardening Rule. Then, a two-dimensional plane-strain finite element analysis of a crankshaft section under fillet rolling and subsequent bending was conducted based on the anisotropic Hardening Rule of Choi and Pan (in preparation) and the nonlinear kinematic Hardening Rule of ABAQUS. In general, the trends of the stress distributions based on the two Hardening Rules are quite similar after the release of roller and under bending. However, the compressive hoop stress based on the anisotropic Hardening Rule is larger than that based on the nonlinear kinematic Hardening Rule within the depth of 2 mm from the fillet surface under bending with consideration of the residual stresses of fillet rolling. The critical locations for fatigue crack initiation according to the stress distributions based on the anisotropic Hardening Rule appear to agree with the experimental observations in bending fatigue tests of crankshaft sections.
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an anisotropic Hardening Rule with non associated flow Rule for pressure sensitive materials
ASME 2009 Pressure Vessels and Piping Conference, 2009Co-Authors: K S Choi, Jwo PanAbstract:In this paper, cyclic plastic behaviors of pressure-sensitive materials based on an anisotropic Hardening Rule with two non-associated flow Rules are examined. The Drucker-Prager pressure-sensitive yield function and the Mises plastic potential function are adopted to explore the cyclic plastic behaviors of pressure-sensitive materials or strength-differential materials. The constitutive relations are formulated for the initial loading and unloading/reloading processes based on the anisotropic Hardening Rule of Choi and Pan [1]. Non-associated flow Rules are employed to derive closed-form stress-plastic strain relations under uniaxial cyclic loading conditions. The stress-plastic strain curves based on a conventional non-associated flow Rule do not close, and show a significant ratcheting under uniaxial cyclic loading conditions. A new non-conventional non-associated flow Rule is then formulated based on observed nearly closed hysteresis loops of pressure-sensitive materials. The stress-plastic strain curves based on the non-conventional non-associated flow Rule show closed hysteresis loops under uniaxial cyclic loading conditions. The results indicate that the anisotropic Hardening Rule with the non-conventional non-associated flow Rule describes well the strength-differential effect and the asymmetric closed hysteresis loops as observed in the uniaxial cyclic loading tests of pressure-sensitive materials.Copyright © 2009 by ASME
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a generalized anisotropic Hardening Rule based on the mroz multi yield surface model
ASME 2008 Pressure Vessels and Piping Conference PVP2008, 2008Co-Authors: K S Choi, Jwo PanAbstract:In this paper, a generalized anisotropic Hardening Rule based on the Mroz multi-yield-surface model is derived. The evolution equation for the active yield surface is obtained by considering the continuous expansion of the active yield surface during the unloading/reloading process. The incremental constitutive relation based on the associated flow Rule is then derived for a general yield function. As a special case, detailed incremental constitutive relations are derived for the Mises yield function. The closed-form solutions for one-dimensional stress-plastic strain curves are also derived and plotted for the Mises materials under cyclic loading conditions. The stress-plastic strain curves show closed hysteresis loops under uniaxial cyclic loading conditions and the Masing hypothesis is applicable. A user material subroutine based on the Mises yield function, the anisotropic Hardening Rule and the constitutive relations was then written and implemented into ABAQUS. Computations were conducted for a simple plane strain finite element model under uniaxial monotonic and cyclic loading conditions based on the anisotropic Hardening Rule and the isotropic and nonlinear kinematic Hardening Rules of ABAQUS. The results indicate that the plastic response of the material follows the intended input stress-strain data for the anisotropic Hardening Rule whereas the plastic response depends upon the input strain ranges of the stress-strain data for the nonlinear kinematic Hardening Rule.Copyright © 2008 by ASME
