Formability prediction using bifurcation criteria and GTN damage model

In this paper, four plastic instability criteria, which are based on the bifurcation theory, coupled with GTN damage model for prediction of diffuse and localized necking. General (GB) criterion limit-point (LPB) used to predict necking, while loss ellipticity (LOE) strong (LOSE) The resulting constitutive equations criteria implemented into finite element code ABAQUS/Standard. formulated within framework large deformations fully three-dimensional approach. Since developed numerical tools have intended applications mainly thin sheet metals; therefore, plane-stress conditions considered criteria. present contribution focuses effect destabilizing mechanisms, due non-associative plasticity non-normal flow rule, forming limit diagrams (FLDs). Theoretical classification in terms their order critical necking strains, is first presented. Then, several variants combined FLDs fictitious materials. It shown that hierarchical different consistent theoretical classification, all model. More specifically, it GB provides a lower bound prediction, LOE represents an upper bound.