数值模拟中应用最小厚度准则预测板料成形极限

在数值模拟中应用最小厚度作为成形极限判据,研究最小厚度值与应变路径的关系。如果对从单向拉伸到双向等拉之间的各种近似线性应变路径均应用相同最小厚度值作为判据,那么得到的极限应变点呈近似线性分布。对实验数据点与计算点的相对位置关系进行分析,发现两者之间的比值存在着近似指数函数的关系。对拉-压区和拉-拉区分别采用两段指数函数对最小厚度值进行修正,使其成为与应变路径相关的变量。采用修正后的最小厚度准则作为数值模拟中极限应变的判据,对ST14钢等三种材料成形极限的预测取得了较好的结果。

Sheet Metal Forming Limit Prediction with Minimum Thickness Criterion in Numerical Simulation

In numerical simulation minimum thickness was taken as forming limit criterion. The research on the relation between minimum thickness and strain paths was carried out. The predicted forming limit strains distributed near linearly if the same minimum thickness was taken as the forming limit criterion to different near-linear strain paths between tensile to equi-biaxial. Exponential function approximate relationship was found among the difference between the experiment data and the predicted data. Then the minimum thickness was modified to be relevant to strain paths by exponential function in the tension-compression region and the tension- tension region respectively. Good agreement was achieved between the predicted data and the experiment data of three kinds of material by using the modified minimum thickness criterion as the forming limit criterion in the numerical simulation.