Improvement of springback prediction accuracy applying a new constitute model considering damage and nonlinear elastic unloading-reloading behaviors

Abstract

Nonlinear elastic unloading-reloading behaviours which were closely related to the springback prediction have been observed in high-strength steels forming process. So, the constitute model considering nonlinear elastic unloading-reloading behaviors must be established. There has been the most classic model Quasi-Plastic-Elastic (QPE) model which can well describes nonlinear elastic behaviour to improve springback calculation accurately. But it does not take into account the effects of continuum damage mechanism on the stress distribution and hysteresis loop. Thus, the QPE model was modified and coupled with Lemaitre damage model to simulate the springback. The proposed model was planted in finite element code ABAQUS with user defined subroutine UMAT. To identify the model parameters and verify the model, the uniaxial unloading-reloading experiments were carried out with X80 high strength pipeline steel. Finally, the proposed model was applied to the simulation of three-point bending forming. The results show that the springback angle error predicted by the QPE-Damage model is within 5% compared with that without considering damage, and the accuracy of springback prediction is significantly improved.