Crystal plasticity-based forming limit prediction for FCC materials under non-proportional strain-path

Sheet metal forming is one of the most important manufacturing processes. The formability of the sheet metal is related to its crystalline structure. In this paper, the forming limit of FCC sheet under non-proportional strain-path is investigated using a crystal plasticity-based prediction model, in which the M–K approach is integrated with a rate-dependent crystal plasticity model. The prediction model has been validated by comparing with the experiment-based FLD data available in the literature, and has been proved to be effective in predicting FLD of anisotropic sheet metal with FCC type of slip systems. The forming limit under non-proportional strain-path has been studied numerically and experimentally. The agreement between the experiments and simulations is quite good. The results show that texture evolution and slip system hardening induced by pre-strain have an important effect on FLD. With crystal plasticity model well describing the crystal microstructure effect, our model can be used to predict the FLD of FCC sheet metal under complicated strain-path in plastic forming process with good accuracy.

Research highlights▶ Uniaxial pre-tension has noticeable effect on FLDs. ▶ FLDs depend on plane equi-biaxial pre-tension. ▶ Plane strain pre-tension has less effect on FLDs. ▶ The forming limit strains of Al5052 sheet are increased by uniaxial pre-tension.