NON-LOCAL PLASTIC-DAMAGE MODEL FOR FAILURE ANALYSIS OFSHEET-METALS

摘要

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 considered by using a modified Thomason's plastic limit-load model.A 3D.Analysis of a unit cube (RVE) containing an ellipsoidal void and rigid inclusion has been carried out to calibrate the coalescence 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.The implicit gradient formulation constitutes an additional partialdifferential equation of the Helmholtz type which is solved separately here by a boundary element method (BEM).The presented formulation is applied to determine the Forming Limit Diagrams (FLD) of an aluminum alloy of a 5182 type.The effectiveness of the numerical predictions is verified carrying out a set of experimental tests with flat-headed and hemispherical punches and D.I.C.strain measurements.