筒形件多次拉深极限预测

Prediction on Multiple Deep-drawing Limits of Cylindrical Cup

依据再次拉深筒坯口部最厚、最硬 ,以及最大拉深力出现于拉深后期的特点 ,假定最大拉深力相应于筒口达到变形区入口位置 ,采用平衡微分方程和塑性方程联解方法 ,建立了变形区应力数值解。应用分散性失稳准则 ,导出再拉深危险断面失稳强度。利用再拉深极限理论及首次拉深极限理论[1 ] ,通过计算机可以迅速准确地预测筒形件及带实缘筒形件的多次极限拉深系数。

Based on the fact that maximum value of both wall thickness and hardness is at the opening of cup blank and the maximum drawing force occurs at a certain moment in later period when succeeding deep-drawing is performed,it is supposed that the maximum drawing force occurs as soon as the opening of cup blank comes to the entrance of deforming region.The numerical solutions of stress in deforming region are established by solving simultaneous equations-diferential balance equation and yielding equation.Besides,the strength of plastic tensile instability on the dangerous section of cup is also established by using the criterion of diffuse instability.Based on the writer's theory on limiting deep-drawing of both first forming and succesively forming.Multiple limiting drawing ratioes of both cup and that with flange may be estimated rapidly and exactly with the help of a computer.