DUCTILE DAMAGE ANALYSIS FOR FRACTURE IN SHEET METAL FORMING BASED ON GTN MESOSCOPIC DAMAGE MODEL

Based on the Gurson-Tvergaard-Needleman (GTN) mesoscopic damage constitutive model, a finite element numerical method is developed to describe the damage and fracture problems in the sheet metal forming. It combines the implicit stress integration method and the explicit finite element solving algorithm. The plastic anisotropic behavior is also considered. The GTN damage models are implemented in the commercial finite element software ABAQUS by using the user material subroutine VUMAT to simulate the damage and failure process in AA5052-O aluminum alloy deep cup drawing. Experiments and numerical analysis of damage and fracture are performed with different sheet diameters. Numerical results show that the GTN damage model can effectively reveal the complicated damage behavior and predict the fracture of the sheet metal forming. The theoretical results of the damage model are in good agreement with the experimental observations. The fracture tendency of the cups increases with the increase of the initial sheet diameter.