Comparison of full field predictions of crystal plasticity simulations using the Voce and the dislocation density based hardening laws

Abstract

Crystal plasticity modeling and simulation is an important predictive tool for understanding the deformation of polycrystalline materials under diverse loading conditions. The validity and accuracy of these simulations depend on the choice of the constitutive law. One of the main components of the constitutive law for plastic deformation is the hardening law. This study, therefore, focuses on understanding the effect of the phenomenological Voce hardening law and the dislocation density based hardening law on full field predictions of crystal plasticity simulations. The crystal plasticity simulations were performed using a three dimensional (3D) fast Fourier transform-based elasto-viscoplastic (EVP-FFT) micromechanical solver for the tensile deformation of copper. Simulation results show that the local distribution of stress strongly depends on the hardening rule. Average texture characteristics predicted by both the laws do not vary significantly. However, spatial orientation evolution (micro-texture) varies with increasing strain. For the Voce law, spatial distribution of the dislocation density calculated from the threshold stress is more homogeneous than the predictions of the dislocation density based hardening law. Finally, our results highlight that a simple dislocation density based storage–recovery model is insufficient to explain the orientation dependence of the stored energy distribution. Hence, careful choice of the hardening law is important for the prediction of localized micromechanical fields.