Prediction of nonlinear kinematic hardening parameters for DP steels by crystal plasticity-based micromechanical analysis

Abstract

Measuring stress-strain curve of sheet material is challenging because the sheet is subject to buckling due to its thin geometry. Modeling springback needs significantly accurate constitutive models which reproduce the material behavior in tension followed by compression or vice versa, because the major deformation in sheet metal forming includes bending/unbending/re-bending. Many experiments to uncover the compressive behavior of sheet metals have been proposed, but still there are uncertainties if the proposed test methods are robust. In this study, a micromechanical simulation approach was proposed to predict the cyclic behavior of dual-phase steels which show significant Bauschinger effect. Crystal plasticity finite element method was employed as a main constitutive model, thus the effect of elastic anisotropy, interactions among grains could be considered. Especially, a simplified dislocation-grain interaction model was newly included and its effect on the cyclic behavior was discussed. Finally, the predicted stress-strain curves were used to obtain material parameters for the well-known phenomenological isotropic-kinematic hardening law which can be directly used for the prediction of springback in sheet metal forming. © 2012 American Scientific Publishers. All rights reserved.