Application of homogeneous potentials for the modeling of the Bauschinger effects in ultra low carbon steel

In this work, an approach is proposed for the description of the plastic behavior of materials subjected to multiple or continuous strain path changes. In particular, although it is not formulated with a kinematic hardening rule, it provides a reasonable description of the Bauschinger effect when loading is reversed. This description of anisotropic hardening is based on homogeneous yield functions/plastic potentials combining a stable, isotropic hardening-type, component and a fluctuating component. The capability of this constitutive description is illustrated with applications on an ultra low carbon steel sheet sample deformed in three-stage uniaxial loading with two load reversals [1].ope

Orthotropic strain rate potentials using multiple linear transformations

This paper reviews a class of anisotropic plastic strain-rate potentials, based on linear transformations of the plastic strain-rate tensor. A new formulation is proposed, which includes former models as particular cases and allows for an arbitrary number of linear transformations, involving an increasing number of anisotropy parameters. The formulation is convex and fully three-dimensional, thus being suitable for computer implementation in finite element codes. The parameter identification procedure uses a micromechanical model to generate evenly distributed reference points in the full space of possible loading modes. Material parameters are determined for several anisotropic, fcc and bcc sheet metals, and the gain in accuracy of the new models is demonstrated. For the considered materials, increasing the number of linear transformations leads to a systematic improvement of the accuracy, up to a number of five linear transformations. The proposed model fits very closely the predictions of the micromechanical model in the whole space of plastic strain-rate directions. The r-values, which are not directly used in the identification procedure, served for the validation of the models and to demonstrate their improved accuracy

PARAMETER IDENTIFICATION OF ADVANCED PLASTIC POTENTIALS AND IMPACT ON PLASTIC ANISOTROPY PREDICTION

In the work presented in this paper, several strain rate potentials are examined in order to analyze their ability to model the initial stress and strain anisotropy of several orthotropic sheet materials. Classical quadratic and more advanced non-quadratic strain rate potentials are investigated in the case of FCC and BCC polycrystals. Different identifications procedures are proposed, which are taking into account the crystallographic texture and/or a set of mechanical test data in the determination of the material parameters.International audienceIn the work presented in this paper, several strain rate potentials are examined in order to analyze their ability to model the initial stress and strain anisotropy of several orthotropic sheet materials. Classical quadratic and more advanced non-quadratic strain rate potentials are investigated in the case of FCC and BCC polycrystals. Different identifications procedures are proposed, which are taking into account the crystallographic texture and/or a set of mechanical test data in the determination of the material parameters

Parameter identification of advanced plastic potentials and impact on plastic anisotropy prediction

In the work presented in this paper, several strain rate potentials are examined in order to analyze their ability to model the initial stress and strain anisotropy of several orthotropic sheet materials. Classical quadratic and more advanced non-quadratic strain rate potentials are investigated in the case of FCC and BCC polycrystals. Different identifications procedures are proposed, which are taking into account the crystallographic texture and/or a set of mechanical test data in the determination of the material parameters

A new concept for continuum distortional plasticity

This paper presents hexah, a framework based on the homogeneous anisotropic hardening (HAH) model. It aims at recreating the effects of arbitrary strain path changes over the plastic behavior of metals. Its core relies on the concept of microstructure deviator, a tensor representing one set of active slip systems. The present theory makes use of an arbitrary number of microstructure deviators spawned by abrupt changes of loading paths. A formalism is detailed to describe a smooth evolution from one set of activated slip systems to another. This new approach carries significant advantages: evolution equations are simplified, the number of parameters decreased, and the behavior near cross-loading stabilized.11Nsciescopu

Advanced constitutive modeling and application to industrial forming processes

Continuum constitutive descriptions of plasticity suitable for finite element simulations of sheet forming processes are succinctly discussed in this presentation. Although multi-scale approaches allow for a more explicit representation of the physical deformation mechanisms occurring at microscopic scales, they are usually not suitable for industrial applications because of the quick turnaround time needed for process design simulations. Therefore, advances in classical concepts such as plastic anisotropy and strain hardening are still very much in demand. Actual forming simulation examples conducted for the steel industry are presented for illustration purposes

Advanced constitutive modeling and application to industrial forming processes

Continuum constitutive descriptions of plasticity suitable for finite element simulations of sheet forming processes are succinctly discussed in this presentation. Although multi-scale approaches allow for a more explicit representation of the physical deformation mechanisms occurring at microscopic scales, they are usually not suitable for industrial applications because of the quick turnaround time needed for process design simulations. Therefore, advances in classical concepts such as plastic anisotropy and strain hardening are still very much in demand. Actual forming simulation examples conducted for the steel industry are presented for illustration purposes