Fold zone analysis in wiping die bending process by using experimental and numerical approaches

This paper deals with an analysis of the fold zone of bent parts within the sheet thickness by means of micro hardness measurement and numerical modelling. The failure risk has to be accurately predicted by using a continuum damage mechanics in order to avoid some expensive experiments. In this reason, a 3D numerical model, based on Lemaitre damage formulations, has been developed. The scalar damage variable D as well as the hardening law are taken to be isotropic within the sheet. The numerical approach is based on an incremental integration scheme of the constitutive equations coupled with ductile damage and von Mises criteria. The corresponding numerical algorithm is implemented into ABAQUS/Standard code. During bending operation, the damage variable evolution is computed and the hydrostatic stress effect is investigated within the sheet thickness. The hardening and plastic strain evolutions have been compared with the micro hardness one deduced from experimental tests. The comparison between experimental and numerical results illustrates the capability of the model in 3D process simulation, particularly in bending processes