Numerical simulation of low stress triaxiality ductile fracture

One of the main shortcoming of existing damage models when applied to the simulation of metal forming operations is their limited validity under low stress triaxiality conditions. An extended Gurson model incorporating the effect of void shape and relative void spacing on the growth and coalescence has been developed in order to encompass both low and large stress triaxiality regimes. The constitutive model has been implemented into an implicit finite element code within a finite strain set up. Identification procedures from experimental data are proposed and illustrated in an application on copper bars exhibiting different strain hardening capacity. A parametric analysis of the damage evolution in specimens deformed under uniaxial tension with necking demonstrates the importance of properly accounting for void shape and void coalescence in the case of large strains problems.