Modeling of large strain multi-axial deformation of anisotropic metal sheets with strength-differential effect using a Reduced Texture Methodology

• RTM is used to provide the computational efficiency while keeping the physics-based nature of the polycrystalline model.
• A new hardening law featuring two hardening matrices for slips systems. Good plasticity modeling for more than 30 loadings.
• A novel initial back stress model at slip system level, which is an effective and practical way to describe history effect.
• The capability of modeling cross-hardening at the macroscopic level is validated through two non-proportional tests.
• The applicability of the present model to large-scale practical problems is demonstrated through structure validations.

This paper works on the macroscopic modeling of the anisotropic plasticity of a 6260-T6 thin-walled aluminum extrusion with a focus on the large strain multi-axial deformation with Strength-Differential Effect (SDE). Based on the framework of the self-consistent polycrystalline plasticity, the recently developed Reduced Texture Methodology (RTM) (Rousselier et al., 2012) is employed to provide the computational efficiency needed for industrial applications while keeping the physically-based nature of the plasticity model. In particular, the new model features a novel hardening law at slip-system level to better capture large strain behaviors, as well as a generic method designed to describe the stress/strain history effect. All model parameters (including texture) are identified from mechanical experiments using a special optimization procedure. An extensive experimental program covering more than 30 distinct multi-axial stress states with both proportional and non-proportional loadings is used to calibrate and validate the present model. Both full- and reduced-thickness specimens are tested to capture the through-thickness heterogeneity of texture and grain size. It is shown that the present model predicts well the stress–strain responses in most of the multi-axial loading conditions which have been tested. Moreover, the model is able to capture various interesting behaviors of the present material during plastic deformation, including anisotropy, through-thickness heterogeneity, SDE of tension/compression or shear, and cross-hardening during non-proportional loadings. Furthermore, successful simulation of two structural level tests including a circular punch indentation and a three-point bending shows the applicability and potential of the new model in industrial practices.