A polycrystalline damage model applied to an anisotropic aluminum alloy 2198 under non-proportional load path changes

Abstract

A ductile damage model, which fully couples classical void growth at high stress triaxiality and Coulomb ductile model at the slip system scale at low stress triaxiality, was applied for the sheet specimens in an anisotropic aluminum alloy under non-proportional load path changes. The Coulomb model combines the resolved normal and shear stresses for each slip plane and directions. A Reduced Texture Methodology (RTM) was used to provide computational efficiency and this approach involved a significant reduction in the number of representative crystallographic orientations. The 12-grain model using 12 crystallographic orientations was validated for non-proportional load path change experiments. The model was calibrated in plasticity using single element calculations under proportional tension, shear and non-proportional ‘shear to tension’ (ST) loadings. Next, the damage parameters were calibrated against the proportional loading shear and tension experimental results using 3D mesh full-size calculations. The calibrated model successfully predicted non-proportional failure. Locally, the damage indicator maxima coincided with the damage location where the damage features were observed via experimental 3D imaging (computed tomography).