Predictions of forming limit diagrams using crystal plasticity models

Crystal plasticity models are used in conjunction with the Marciniak-Kuczynski approach to predict forming limit diagrams (FLDs) of different annealed aluminium alloy sheet (AA6xxx series) with various initial crystallographic textures. The numerically determined FLDs are compared with experimental data. Two distinct models are used for FLDs predictions. The first method involves the calculation of yield surfaces from a rigid-plastic rate insensitive crystal plasticity model without recourse to the use of analytical yield functions. In the second method, the response of the material is based on an elastic-viscoplastic crystal plasticity model. Both methods take into account texture evolution during deformation. By taking into consideration the elastic part of the deformation, the elastic-plastic model can predict the shift of the forming limit curve minimum towards positive minor strains. It is found that the Goss orientation 011 〈 100〉 present in the initial texture as well as the microstructure influence significantly the formability.