Occurence of strain path changes in a two-stage deep drawing process

This work is dedicated to the influence of the strain path change on the prediction of the deep-drawing of cylindrical cups. The aim of this work is to highlight the influence of the hardening model on the numerical prediction of the applied punch load, in the case of the 1999 Numisheet benchmark of the reverse re-drawing of cylindrical cups. The forming process consists in drawing a circular blank into a cylindrical cup in two stages, firstly in one direction and then in the opposite one. Three-dimensional numerical simulations of the process were performed using the Hill’s 1948 yield criterion associated with three different hardening laws: a purely isotropic hardening, a mixed hardening with both isotropic and non-linear kinematic contributions and a dislocation-based hardening model, which takes into account transient behaviors recorded during strain path changes. The experimental setup is presented as well as results obtained with a mild steel. Numerical simulation results obtained with the three hardening models are compared with experimental ones. It is shown that there is a significant influence of the hardening model in the second stage, when important strain path changes occur during the process.