Abstract: With considering the influence of equivalent plastic strain on void-damage and taking Lemaitre damage equivalent stress as plastic potential, based on continuous damage mechanics theory, a new criterion for ductile fracture is derived. The two key material constants in the criterion are determined by the combination of tension tests with FE (finite element) simulation. On the basis of the values of stress and strain calculated from commercial finite element software, the forming limit in cylindrical deep drawing of annealed aluminum alloy LY12(M) is predicted by means of the new ductile fracture criterion. Experiments verify that the predicted results are in agreement with the experimental ones. Hence, it is reliable to predict the forming limit in deep drawing by means of the new ductile fracture criterion.

Key words: Sheet metal forming, Ductile fracture criterion, FEM, Forming limit