Failure analysis of anisotropic sheet-metals using a non-local plastic damage model

A ductile damage model which takes account of void shape effect and anisotropy of the matrix material is integrated into an explicit finite element framework to predict the damage evolution which occurs under crash or stamping process. The void coalescence failure mechanism by internal necking is also considered by using a modified Thomason's plastic limit-load model. The pathological mesh dependence has been overcome by a non-local approach where the Laplacians of the effective plastic strain and of the porosity are incorporated. In this paper, the implicit gradient formulation constitutes an additional partial differential equation of the Helmholtz type which is solved separately by a boundary element method (BEM). The presented formulation is applied to a mild-steel, a Ni-based sheet-metal (INCO 718) and an aluminium alloy (AA 5182). The effectiveness of the numerical predictions is verified carrying out a set of experimental tests with a flat-headed punch.