GTN MESO-DAMAGE MODEL BASED ON DIFFERENT HARDENING RULES AND ITS APPLICATION FOR SPRINGBACK FINITE ELEMENT ANALYSIS IN SHEET METAL FORMING

To improve the accuracy of springback prediction in sheet metal forming, a Gurson-Tvergaard- Needleman (GTN) meso-damage model and its finite element constitutive integration algorithm are developed, based on Ziegler linear kinematic hardening, Lemaitre-Chaboche nonlinear kinematic and nonlinear combined hardening rules. The GTN damage models are implemented in the commercial finite element software ABAQUS by using the user material subroutine VUMAT. The NUMISHEET’93 U-bending benchmark problem is employed to investigate the effect of different hardening rules and damage on springback prediction by using the coupled explicit to implicit the finite element procedure. The results show that the springback predicted by the linear kinematic hardening and nonlinear kinematic rules is small, then is that predicted by the nonlinear combined hardening rule. The springback predicted by the isotropic hardening rule is the largest. After considering the damage, the GTN model predicts lower springback, which is closer to the experiment data.