不同断裂准则下铝合金冲压成形裂纹扩展模拟

使用自主研发的金属板材摩擦系数测试设备,在不同拉速、不同压力条件下,测试了6016铝合金板材在冲压成形过程中的变摩擦系数值和平均摩擦系数值。建立了铝合金板材胀型实验数值模型,模型中输入平均摩擦系数来考虑摩擦边界条件,分别选取成形极限图以及临界厚度减薄率作为铝合金板材断裂准则,采用有限元法对数值模型进行了求解计算,并对数值模拟计算结果进行了实验验证。对比分析发现,采用成形极限图作为模型断裂准则计算时,裂纹起裂位置及区域与实验结果有较大差异;采用临界厚度减薄率作为模型断裂准则计算时,裂纹起裂位置及形貌与实验结果吻合度较高。证明了本文研究所得的临界厚度减薄率准则可以用于预测铝合金板材在冲压成形过程中裂纹的产生及扩展问题。

The crack propagation numerical simulation of stamping of aluminum alloy sheets under different fracture critera

Under different pressure and different pulling speed conditions, the dynamic and the average friction coefficient of 6016 aluminum alloy sheets during the stamping process is tested by self-developed friction coefficient test equipment of metal sheets. A numerical model of aluminum alloy sheet expansion test is established with importing average friction coefficient to consider the friction boundary conditions. With taking forming limit diagram and critical thickness reduction rate as cracking criterion respectively, the numerical model is calculated by finite element method and the calculation results are verified experimentally. The results show that the crack initiation position and the crack morphology are more accord with experimental verification results when the critical thickness reduction rate is taken as cracking criterion, which proves the critical thickness reduction rate parameters obtained in this paper are suitable for analyzing the crack initration and propagation of aluminum alloy sheets in the stamping process.