Abstract: Based on Gurson-Tvergaard-Needleman(GTN) mesoscopic damage model, a stress update numerical algorithm is extended for plane stress and shell element. The damage evolution behavior of the high temperature metal sheet during hot stamping is studied. A detail method which combined response surface method based on central composite design and genetic optimization algorithm to identify the damage parameters of GTN model under elevated temperature is described. The damage parameters and of high strength steel 22MnB5 under different elevated temperatures(600-800 ℃) are identified through this method. Using these obtained parameters, the NAKAJIMA bulge forming test under elevated temperatures coupled with GTN mesoscopic damage model is simulated and the damage evolution of sheet is analyzed. The results show that the simulation results agree with the experimental conditions very well. It indicates that the GTN model can be used to predict the damage and failure of metal sheet under hot stamping process and the method to identify the damage parameter is available.

Key words: mesoscopic damage, numerical algorithm, response surface, simulation prediction, hot stamping