Crystal plasticity finite element analysis of ferritic stainless steel for sheet formability prediction

A crystal plasticity finite element analysis was conducted for predicting forming limits of a ferritic stainless steel. A virtual microstructure crystal plasticity finite element model, or a representative volume element (RVE), was developed, in which the behavior of grains was governed by a rate-dependent viscoplastic crystal plasticity model. To account for the variation in hardening of different slip modes, the model parameters of different slip modes in the bcc metal were obtained from the uniaxial stress-strain, longitudinal-transverse strains, and hydraulic bulge test data using an inverse method. A multi-scale framework, which combines the virtual microstructure models and the Marciniak-Kuczynski procedure, was developed and applied to the forming limit analysis of a ferritic stainless steel. Forming limits predicted using the combined slip mode compared well with the measurements when the {110}<111> and {112}<111> slip systems are operating and the {123}<111> slip systems are inactive. The influence of the slip system activity on the yield criteria and forming limits is discussed.