an analytical approach for the prediction of forming limit curves subjected to combined strain paths

in the present work, an analytical approach for the prediction of forming limit curves is proposed to incorporate the effect of combined strain paths. the effect of combined strain paths (considering the directional dependency of pre-straining and further straining) is addressed by integrating the incremental equivalent strain expression in two stages i.e., pre-strain and subsequent loading. in each stage, the strain path is assumed to be linear and different combinations of pre-strain (uniaxial, plane-strain and equi-biaxial) are considered. material anisotropy is taken into account in each stage. the predictions of the present model are compared with the experimental results on forming limit curves under combined strain paths for al6111-t4 and are found to be in good agreement with each other.