The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Nobutada Ohno - One of the best experts on this subject based on the ideXlab platform.
-
implementation of cyclic plasticity models based on a general form of Kinematic Hardening
International Journal for Numerical Methods in Engineering, 2002Co-Authors: Mineo Kobayashi, Nobutada OhnoAbstract:This paper deals with implementation of cyclic plastic constitutive models in which a general form of strain Hardening and dynamic recovery is employed to represent the multilinear, as well as non-linear, evolution of back stress. First, in order to incorporate such a general form of Kinematic Hardening in finite element methods, successive substitution and its convergence are discussed for implicitly integrating stress; moreover, a new expression of consistent tangent modulus is derived by introducing a set of fourth-rank constitutive parameters into discretized Kinematic Hardening. Then, the constitutive parameters introduced are specified in three cases of the general form of Kinematic Hardening; the three cases have distinct capabilities of simulating ratcheting and cyclic stress relaxation. Numerical examples are given to verify the convergence in successive substitution and the new expression of consistent tangent stiffness. Error maps for implicitly integrating stress under non-proportional as well as proportional loading are also given to show that the multilinear case of the general form provides high accuracy even if strain increment is very large. Copyright © 2002 John Wiley & Sons, Ltd.
-
Kinematic Hardening model suitable for ratchetting with steady state
International Journal of Plasticity, 2000Co-Authors: Mohammad Abdelkarim, Nobutada OhnoAbstract:Abstract A new Kinematic Hardening model useful for simulating the steady-state in ratchetting is developed within the framework of the strain Hardening and dynamic recovery format. The model is formulated to have two kinds of dynamic recovery terms, which operate at all times and only in a critical state, respectively. The model is examined on the basis of nonproportional experiments of Modified 9Cr–1Mo steel at 550°C and IN738LC at 850°C. The experiments include multiaxial, as well as uniaxial, ratchetting, multiaxial cyclic stress relaxation, and nonproportional cyclic straining along a butterfly-type strain path. It is shown that the model is successful in simulating the experiments, and that the model is featured by the capability of representing appropriately the steady-state in ratchetting under multiaxial and uniaxial cyclic loading.
-
Kinematic Hardening rules with critical state of dynamic recovery part i formulation and basic features for ratchetting behavior
International Journal of Plasticity, 1993Co-Authors: Nobutada Ohno, J.-d. WangAbstract:Abstract Kinematic Hardening rules formulated in a Hardening/dynamic recovery format are examined for simulating rachetting behavior. These rules, characterized by decomposition of the Kinematic Hardening variable into components, are based on the assumption that each component has a critical state for its dynamic recovery to be activated fully. Discussing their basic features, the authors show that they can predict much less accumulation of uniaxial and multiaxial ratchetting strains than the Armstrong and Frederick rule. Comparisons with multilayer and multisurface models are made also, resulting in a finding that the simple one in the present rules is similar to the multilayer model with total strain rate replaced by inelastic (or plastic) strain rate. Part II of this work deals with applications to experiments.
-
Kinematic Hardening rules with critical state of dynamic recovery part ii application to experiments of ratchetting behavior
International Journal of Plasticity, 1993Co-Authors: Nobutada Ohno, J.-d. WangAbstract:Abstract The Kinematic Hardening rules formulated in Part I of this work (i.e, Models I and II) are applied to ratchetting experiments of Modified 9Cr-1Mo steel done by Tanaka et al. as well as to a nonproportional experiment of OFHC copper by Lamba and Sidebottom. It is shown the Models I and II have the capability of simulating ratchetting behavior well because they can predict much less accumulation of ratchetting strain under uniaxial and multiaxial loadings than the Armstrong and Frederick model. It is also shown that if ratchetting strain is negligible, Models I and II may give nearly the same predictions as the Armstrong and Frederick model.
-
transformation of a nonlinear Kinematic Hardening rule to a multisurface form under isothermal and nonisothermal conditions
International Journal of Plasticity, 1991Co-Authors: Nobutada Ohno, J.-d. WangAbstract:Abstract A nonlinear Kinematic Hardening rule with back stress decomposed into components is transformed to a multisurface form. First it is shown under isothermal conditions that the multisurfaces generated by the transformation are nested and obey a Mroz-type translation rule. It is also shown that the multisurface form can be specialized to a piecewise linear Kinematic Hardening rule. The transformation is then applied to a time recovery term describing thermal softening and a temperature-rate term operating in nonisothermal inelasticity. A multisurface model is thus derived for nonisothermal, as well as isothermal, plasticity and viscoplasticity.
J.-d. Wang - One of the best experts on this subject based on the ideXlab platform.
-
Kinematic Hardening rules with critical state of dynamic recovery part i formulation and basic features for ratchetting behavior
International Journal of Plasticity, 1993Co-Authors: Nobutada Ohno, J.-d. WangAbstract:Abstract Kinematic Hardening rules formulated in a Hardening/dynamic recovery format are examined for simulating rachetting behavior. These rules, characterized by decomposition of the Kinematic Hardening variable into components, are based on the assumption that each component has a critical state for its dynamic recovery to be activated fully. Discussing their basic features, the authors show that they can predict much less accumulation of uniaxial and multiaxial ratchetting strains than the Armstrong and Frederick rule. Comparisons with multilayer and multisurface models are made also, resulting in a finding that the simple one in the present rules is similar to the multilayer model with total strain rate replaced by inelastic (or plastic) strain rate. Part II of this work deals with applications to experiments.
-
Kinematic Hardening rules with critical state of dynamic recovery part ii application to experiments of ratchetting behavior
International Journal of Plasticity, 1993Co-Authors: Nobutada Ohno, J.-d. WangAbstract:Abstract The Kinematic Hardening rules formulated in Part I of this work (i.e, Models I and II) are applied to ratchetting experiments of Modified 9Cr-1Mo steel done by Tanaka et al. as well as to a nonproportional experiment of OFHC copper by Lamba and Sidebottom. It is shown the Models I and II have the capability of simulating ratchetting behavior well because they can predict much less accumulation of ratchetting strain under uniaxial and multiaxial loadings than the Armstrong and Frederick model. It is also shown that if ratchetting strain is negligible, Models I and II may give nearly the same predictions as the Armstrong and Frederick model.
-
transformation of a nonlinear Kinematic Hardening rule to a multisurface form under isothermal and nonisothermal conditions
International Journal of Plasticity, 1991Co-Authors: Nobutada Ohno, J.-d. WangAbstract:Abstract A nonlinear Kinematic Hardening rule with back stress decomposed into components is transformed to a multisurface form. First it is shown under isothermal conditions that the multisurfaces generated by the transformation are nested and obey a Mroz-type translation rule. It is also shown that the multisurface form can be specialized to a piecewise linear Kinematic Hardening rule. The transformation is then applied to a time recovery term describing thermal softening and a temperature-rate term operating in nonisothermal inelasticity. A multisurface model is thus derived for nonisothermal, as well as isothermal, plasticity and viscoplasticity.
Mohammad Abdelkarim - One of the best experts on this subject based on the ideXlab platform.
-
an evaluation for several Kinematic Hardening rules on prediction of multiaxial stress controlled ratchetting
International Journal of Plasticity, 2010Co-Authors: Mohammad AbdelkarimAbstract:Abstract This study evaluates the performance of several non-linear Kinematic Hardening rules in predicting the various biaxial ratchetting experiments of stainless steel (SS) 304L under various stress-controlled histories performed by Hassan et al. (2008) . The non-linear Kinematic Hardening rules proposed by Burlet and Cailletaud, 1986 , Ohno and Wang, 1993 , Ohno and Wang, 1994 , Abdel-Karim and Ohno, 2000 , Kang, 2004 , Chen and Jiao, 2004 , Chen et al., 2005 and the different rules of Abdel-Karim (2009) are examined and carefully scrutinized. The considered Kinematic Hardening rules range from the simple classical ones to more detailed rules, which incorporate additional terms and/or parameters to simulate different factors that affect ratchetting. It is shown that none of the examined Kinematic Hardening rules is general enough to simulate all of the ratchetting responses for the experiments under consideration.
-
modified Kinematic Hardening rules for simulations of ratchetting
International Journal of Plasticity, 2009Co-Authors: Mohammad AbdelkarimAbstract:Abstract In order to simulate multiaxial ratchetting, and as a preliminary step, common different variables introduced into the dynamic recovery term of recently developed Hardening rules are presented and scrutinized in details. Subsequently, two modified Kinematic Hardening rules are formulated and presented. The proposed modified rules are based on the Ohno–Wang Kinematic Hardening rule in which accumulated plastic strain increment is contributed to the dynamic recovery term. The first modified rule is defined by introducing the radial evanescence term of Burlet–Cailletaud [Burlet, H., Cailletaud, G., 1986. Numerical techniques for cyclic plasticity at variable temperature. Eng. Comput. 3, 143–153] into the Ohno–Wang rule powered by specific material parameters. In the second modified rule a multiplying factor, depends on both the unit vector normal to the yield surface ( n ∼ ) and the deviatoric part of back stress ( a ∼ ), is utilized into the Ohno–Wang rule. The modified rules are examined in details to study their characteristics under uniaxial tensile, uniaxial cyclic and multiaxial loading conditions. Then, the validity and accuracy of these rules are scrutinized critically based on simulations of the well-known multiaxial ratchetting experiments of Corona et al. [Corona, E., Hassan, T., Kyriakids, S., 1996. On the performance of Kinematic Hardening rules in predicting a class of biaxial ratchetting experiments. Int. J. Plast. 12 (1), 117–145] as well as the recently carried out experiments of Chen et al. [Chen, X., Jiao, R., Kim, K.S., 2005. On the Ohno–Wang Kinematic Hardening rules for multiaxial ratchetting modeling of medium carbon steel. Int. J. Plast. 21, 161–184]. The two modified Kinematic Hardening rules simulate most of the considered multiaxial ratchetting experiments fairly well; nevertheless, the second one is relatively superior.
-
Kinematic Hardening model suitable for ratchetting with steady state
International Journal of Plasticity, 2000Co-Authors: Mohammad Abdelkarim, Nobutada OhnoAbstract:Abstract A new Kinematic Hardening model useful for simulating the steady-state in ratchetting is developed within the framework of the strain Hardening and dynamic recovery format. The model is formulated to have two kinds of dynamic recovery terms, which operate at all times and only in a critical state, respectively. The model is examined on the basis of nonproportional experiments of Modified 9Cr–1Mo steel at 550°C and IN738LC at 850°C. The experiments include multiaxial, as well as uniaxial, ratchetting, multiaxial cyclic stress relaxation, and nonproportional cyclic straining along a butterfly-type strain path. It is shown that the model is successful in simulating the experiments, and that the model is featured by the capability of representing appropriately the steady-state in ratchetting under multiaxial and uniaxial cyclic loading.
Otto T Bruhns - One of the best experts on this subject based on the ideXlab platform.
-
new cyclic crystal viscoplasticity model based on combined nonlinear Kinematic Hardening for single crystals
Materials Research Innovations, 2011Co-Authors: Guozheng Kang, Otto T BruhnsAbstract:Based on the existing experimental data of cyclic deformation for copper single crystal, a face centred cubic crystal, a new cyclic constitutive model was developed in the framework of single crystal viscoplasticity. In the developed model, a combined nonlinear Kinematic Hardening model was introduced and the remarkable cyclic Hardening of copper single crystal was described by the progressive evolution of back stress and isotropic deformation resistance in each slip system. The self‐ and latent‐Hardening of dislocation slip in the different slip systems were considered by employing an interaction Hardening matrix H. The proposed model is first verified by comparing the simulated results with some referable experimental data. And then, the capability of the model to describe the uniaxial ratcheting of copper single crystal is discussed, even if the corresponding experimental data cannot be referred now yet.
-
large simple shear and torsion problems in Kinematic Hardening elasto plasticity with logarithmic rate
International Journal of Solids and Structures, 2001Co-Authors: Otto T Bruhns, H Xiao, A MeyersAbstract:Abstract Large simple shear and torsion problems in plasticity have been the object of a large number of papers. Sophisticated schemes have been developed (e.g. J. Appl. Mech. 50 (1983) 561) that overcome problems encountered (cf. e.g. J. Mech. Phys. Solids 48 (2000) 2231; Int. J. Solids Struct. 37 (2000) 5037). This paper substantially uses the logarithmic rate (Acta Mechanica 124 (1997a) 89), which is equally based on strong mathematical and physical principles and therefore may contrast to classical approaches of cited kinds. Stress responses to large simple shear and torsional deformations in elastoplastic bodies are studied by applying the self-consistent Kinematic Hardening J 2 -flow model based on the logarithmic tensor rate, recently established by these authors (Int. J. Plasticity 15 (1999) 479). The application of the logarithmic stress rate in the elastic rate equation of hypoelastic type results in an exact finite hyperelastic solution in terms of Hencky's logarithmic strain. The plastic solution is composed of two parts: the back stress and the effective stress (the Kirchhoff stress reduced by the back stress). It is shown that the evolution equation of the back stress with the logarithmic rate is integrable to deliver a closed-form relation between the back stress and Hencky's logarithmic strain and the current stress. Moreover, the effective stress is shown to be governed by a first-order nonlinear ordinary differential equation with a small dimensionless material parameter multiplying the highest derivative, for which the initial condition is related to the elastic–plastic transition and prescribed in terms of the just-mentioned small parameter. A singular perturbation solution for the just-mentioned equation is derived by utilizing the method of matched expansions. With the analytical solution derived, it is possible to make a detailed study of the coupling effect of material properties, including the elastic, yielding and Hardening properties, on elastic–plastic responses. For the large deformations at issue, it is demonstrated that, merely with three commonly known classical material constants, i.e., the elastic shear modulus, the initial tensile yield stress and the Hardening modulus, the simple Kinematic Hardening J 2 -flow model with the logarithmic rate may supply satisfactory explanations for salient features of complex behaviour in experimental observation.
-
large strain responses of elastic perfect plasticity and Kinematic Hardening plasticity with the logarithmic rate swift effect in torsion
International Journal of Plasticity, 2001Co-Authors: H Xiao, Otto T Bruhns, A MeyersAbstract:Abstract A new Eulerian rate type elastic-perfectly plastic model has recently been established by utilizing the newly discovered logarithmic rate. It has been proved that this model is unique among the objective elastic-perfectly plastic models with all objective corotational stress rates and other known objective stress rates by virtue of the self-consistency criterion: the hypoelastic formulation intended for elastic behaviour must be exactly integrable to deliver a hyperelastic relation. The finite simple shear response of this model has been studied and shown to be reasonable for both shear and normal stress components. On the other hand, a Kinematic Hardening plasticity model may be formulated by adopting the logarithmic rate. The objective of this work is to further study the large deformation responses of the foregoing two kinds of idealized models, in particular the well-known Swift effect, in torsion of thin-walled cylindrical tubes. A complete, rigorous analysis is made for the orders of magnitude of all stress components. A closed-form solution is obtained for the Kinematic Hardening plastic case, and an analytical perturbation solution is derived for the elastic-perfectly plastic case. It is shown that the simple idealized Kinematic Hardening model with the logarithmic rate, which uses only two classical material constants, i.e., the initial (tensile) yield stress and the Hardening modulus, may arrive at satisfactory explanation for and reasonable accord with salient features of experimental observation.
A Meyers - One of the best experts on this subject based on the ideXlab platform.
-
large simple shear and torsion problems in Kinematic Hardening elasto plasticity with logarithmic rate
International Journal of Solids and Structures, 2001Co-Authors: Otto T Bruhns, H Xiao, A MeyersAbstract:Abstract Large simple shear and torsion problems in plasticity have been the object of a large number of papers. Sophisticated schemes have been developed (e.g. J. Appl. Mech. 50 (1983) 561) that overcome problems encountered (cf. e.g. J. Mech. Phys. Solids 48 (2000) 2231; Int. J. Solids Struct. 37 (2000) 5037). This paper substantially uses the logarithmic rate (Acta Mechanica 124 (1997a) 89), which is equally based on strong mathematical and physical principles and therefore may contrast to classical approaches of cited kinds. Stress responses to large simple shear and torsional deformations in elastoplastic bodies are studied by applying the self-consistent Kinematic Hardening J 2 -flow model based on the logarithmic tensor rate, recently established by these authors (Int. J. Plasticity 15 (1999) 479). The application of the logarithmic stress rate in the elastic rate equation of hypoelastic type results in an exact finite hyperelastic solution in terms of Hencky's logarithmic strain. The plastic solution is composed of two parts: the back stress and the effective stress (the Kirchhoff stress reduced by the back stress). It is shown that the evolution equation of the back stress with the logarithmic rate is integrable to deliver a closed-form relation between the back stress and Hencky's logarithmic strain and the current stress. Moreover, the effective stress is shown to be governed by a first-order nonlinear ordinary differential equation with a small dimensionless material parameter multiplying the highest derivative, for which the initial condition is related to the elastic–plastic transition and prescribed in terms of the just-mentioned small parameter. A singular perturbation solution for the just-mentioned equation is derived by utilizing the method of matched expansions. With the analytical solution derived, it is possible to make a detailed study of the coupling effect of material properties, including the elastic, yielding and Hardening properties, on elastic–plastic responses. For the large deformations at issue, it is demonstrated that, merely with three commonly known classical material constants, i.e., the elastic shear modulus, the initial tensile yield stress and the Hardening modulus, the simple Kinematic Hardening J 2 -flow model with the logarithmic rate may supply satisfactory explanations for salient features of complex behaviour in experimental observation.
-
large strain responses of elastic perfect plasticity and Kinematic Hardening plasticity with the logarithmic rate swift effect in torsion
International Journal of Plasticity, 2001Co-Authors: H Xiao, Otto T Bruhns, A MeyersAbstract:Abstract A new Eulerian rate type elastic-perfectly plastic model has recently been established by utilizing the newly discovered logarithmic rate. It has been proved that this model is unique among the objective elastic-perfectly plastic models with all objective corotational stress rates and other known objective stress rates by virtue of the self-consistency criterion: the hypoelastic formulation intended for elastic behaviour must be exactly integrable to deliver a hyperelastic relation. The finite simple shear response of this model has been studied and shown to be reasonable for both shear and normal stress components. On the other hand, a Kinematic Hardening plasticity model may be formulated by adopting the logarithmic rate. The objective of this work is to further study the large deformation responses of the foregoing two kinds of idealized models, in particular the well-known Swift effect, in torsion of thin-walled cylindrical tubes. A complete, rigorous analysis is made for the orders of magnitude of all stress components. A closed-form solution is obtained for the Kinematic Hardening plastic case, and an analytical perturbation solution is derived for the elastic-perfectly plastic case. It is shown that the simple idealized Kinematic Hardening model with the logarithmic rate, which uses only two classical material constants, i.e., the initial (tensile) yield stress and the Hardening modulus, may arrive at satisfactory explanation for and reasonable accord with salient features of experimental observation.
