基于修正M-K模型的AZ31B镁合金板材预变形前后成形极限预测

Forming limit prediction of magnesium alloy sheet before and after pre-strain based on the modified M-K model

在Marciniak-Kuczynski(M-K)模型基础上,结合修正Mohr-Coulomb(MMC)理论和韧性断裂准则建立了修正M-K模型,并对AZ31B镁合金板材成形极限进行了预测。通过修正MMC理论获取了板材成形过程中各应变路径下的极限应变,利用韧性断裂准则判断原始板材及预变形后板材在各个应变路径下是否达到失效,从而获得了板材的成形极限图(FLD)。结果表明,基于修正M-K模型理论计算获取的AZ31B镁合金板材的FLD比传统的M-K模型的预测结果更准确,验证了该方法的可行性和准确性。通过修正M-K模型理论预测了室温预变形和250℃预变形工艺对AZ31B镁合金板材成形极限的影响,随着预变形量的增加,板材成形极限逐渐向左上偏移,且250℃预变形板材的成形极限提高更为显著。

Based on the Marciniak-Kuczynski(M-K)model,combined with the modified Mohr-Coulomb(MMC)criterion and the ductile fracture criterion,a modified M-K model was established,and the forming limit of AZ31B magnesium alloy sheet was predicted.The ultimate strain under each strain path in sheet forming process was obtained by modified MMC theory,the ductile fracture criterion was used to judge whether the as-received sheet and pre-strained sheet reached failure under each strain path,and the forming limit diagram(FLD)of sheet was obtained.The results show that the prediction of FLD based on the theoretical calculation of modified M-K model is more accurate than that based on traditional M-K model,which verifies the feasibility and accuracy of the method.The influences of room temperature pre-strained and 250℃pre-strained processes on the forming limit of AZ31B magnesium alloy sheet were predicted by modified M-K model theory.With the increase of pre-strain amount,the forming limit of the sheet gradually shifts to the upper left,and the forming limit of 250℃pre-strained sheet increases more significantly.