基于成形应力极限的管材液压成形缺陷预测

基于塑性应力应变关系及Hill79屈服准则,推导出极限应力与极限应变间转化关系,进而建立2008T4铝合金的成形应力极限图(Forming limit stress diagram,FLSD)。采用LS-DYNA软件对三通管液压胀形过程进行模拟,应用FLSD预测胀形过程中破裂的发生及成形压力极限,并与传统成形极限图(Forming limit diagram,FLD)结果进行了对比。研究表明,FLD与FLSD预测结果中破裂缺陷位置相同,但极限内压力值存在很大差别,而FLSD预测结果与物理试验结果较吻合。考虑到FLD受应变路径影响显著的因素,将FLSD作为管材液压成形等复杂应变路径下的成形极限的判据更加方便可靠。

Prediction of Defects in Tube Hydroforming Based on Forming Stress Limit

Transformation relation between limit strain and limit stress is derived on the basis of the plastic theory and Hill79 yield criterion. Then, the conventional strain-based forming limit diagram (FLD) of 2008T4 Aluminum alloy sheet is converted into stress-based forming limit stress diagram (FLSD). This FLSD is used in conjunction with LS-DYNA finite element simulation to predict the onset of necking and the limit pressure in T-shaped tube hydroforming. The prediction results using FLSD and FLD are also comp...