Forming Limit Prediction of Anisotropic Aluminum Magnesium Alloy Sheet AA5052-H32 Using Micromechanical Damage Model

This paper focuses on the implementation and applicable evaluation of a modified Gurson–Tvergaard–Needleman (GTN) damage model for predicting forming limit diagram of anisotropic aluminum alloy sheet, in which its elasto-plastic behavior is assumed to obey a non-quadratic anisotropic yield criterion. The original porous ductile material model is heuristically enhanced to suit anisotropy of sheet metal, and then, it is implemented via a user material subroutine using finite element codes of ABAQUS/Explicit software package. The material damage model is calibrated and applied to predict forming limit diagram of commercial aluminum alloy sheet AA5052-H32 via the Nakajima drawing tests under plane stress condition. To obtain various strain paths, the Nakajima tests are conducted for seven specimens, which are designed in accordance with standard ISO 12004-2-2008. The influence of material anisotropy on the predicted forming limit is also considered and discussed. The numerical simulation results obtained from the proposed damage model showed a good agreement with those of the experimental data.