热冲压成形过程细观损伤演化机理研究

基于Gurson-Tvergaard-Needleman(GTN)细观损伤模型,扩展其在平面应力、壳单元问题中的应力更新数值算法,研究高强度硼钢热冲压成形过程中板材内部的损伤演化行为。采用响应曲面中心复合试验设计和遗传优化算法,系统地阐述高温下GTN损伤参数的识别方法并获取了热成形高强度硼钢22Mn B5在高温下(600~800℃)的损伤特征参数(0,,,N Ff f f fc)。对耦合损伤的高强度钢板NAKJIMA凸模胀形热冲压过程进行有限元仿真预测,并与试验结果进行对比分析。结果表明:运用响应曲面法确定热冲压高温板材损伤参数的方法是可行的,同时采用GTN损伤模型可以准确模拟高强度钢板热冲压过程中的开裂行为。

Investigation of Mesoscopic Damage Evolution Mechanism of High Strength Steel in Hot Stamping Process

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 f0, fN , fc and fF 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.