Prediction of deformation and failure anisotropy for thin magnesium sheets under mixed-mode loading

Abstract

The plastic deformation and the failure behavior of a third generation magnesium AZ31 sheet is studied under quasi-static tensile, compressive, and mixed mode loading conditions at room temperature. While the deformation anisotropy is found to be less pronounced compared to previously investigated rolled sheets of this alloy, a strong dependence of the failure strain on the sheets orientation is experienced. This failure anisotropy is further studied and quantified using mixed-mode tests realized using a modified Arcan fixture. The irreversible deformation is modeled in the framework of finite elements using two coupled anisotropic plastic potentials. The model parameters are calibrated using the global force-elongation record of the tested samples. For the prediction of failure, an uncoupled damage model based on transformation of strain rates is developed and applied. It is shown that this model is able to predict the observed edge failure of notched specimens with good accuracy. The model predictions for the smooth tensile tests are analyzed in detail by full-field FE analyses to understand the interaction between strain localization and predicted damage evolution.