Finite element simulation of sheet forming based on a planar anisotropic strain-rate potential (Q1918367)

Many FEM formulations are based on stress potentials defined in the stress field. Nevertheless, there are formulations where potentials defined in the strain-rate field are especially convenient for implementation. These include rigid-plastic formulations based on minimum plastic work paths, which can be used for process design as well as for process analysis. In this paper, based on a strain-rate potential proposed recently for anisotropic materials exhibiting orthotropic symmetry, a formulation for sheet forming process analysis is developed using the Cartesian coordinate system. An efficient formulation to account for material rotation is also included. The predictions made for a cup draving test of a 2090-T3 aluminium-lithium alloy sheet show good agreement with experiments. However, some discrepancies are observed between predicted and experimental thickness strain and cup height directional trends. The cause of these discrepancies is discussed using a simple analysis based on Lankford or on plastic strain relation.