基于韧性断裂的汽车用铝合金板滚压包边成形开裂预测

Fracture Prediction of Auto-body Aluminum Alloy Sheets under Roller Hemming Process Based on Ductile Fracture

通过对比铝合金平面直线翻边试验及基于集中性失稳模型得到的极限应变和开裂断口,研究了汽车用铝合金滚压包边的失效机理;基于韧性断裂、塑性增量法则和混合强化准则,理论推导得到了弯曲成形极限图,并通过试验对成形极限应力图进行了验证;最后,通过数值解析的方法,研究了韧性断裂准则在滚边成形中的适用范围。结果表明:基于韧性断裂准则的成形极限图,可以用来预测铝合金滚压包边过程中产生的开裂;包边变形过程中弯曲强化效应无法忽略,适用于拉弯成形极限预测的集中性失稳理论将无法应用于滚压包边成形。

The limit strain and fracture from flat surface straight line flanging and under localized instability necking theory were compared to study the failure mode of aluminum alloy sheet in roller hemming process. The bending limit curve could be got by theoretical derivation based on ductile fracture, deformation theory of constitutive equation and combined hardening rule, and was verified by comparing with experiment result. Finally, the available range of ductile fracture criterion in roller hemming process was studied by numerical analysis. The results show that the bending limit curve based on ductile fracture could be adapted for prediction of roller hemming fracture of aluminum alloy sheets. Since the bending enhancement effect can＇t be neglected in roller hemming, the localized instability necking theory for stretch bending can/t be applied to roller hemming process.