等应变模变薄拉延时的上限法研究

 首次拟定了等应变模变薄拉延时的运动学容许速度场。根据上限原理,研究了等应变模变薄拉延时各变形工艺参数对冲头单位压力的作用。同时,结合最小能量原理,优化了重要工艺参数—凹模型线高度(H_opt)值。研究结果表明:变薄系数、加工硬化效应、变形体与凹模间的摩擦是决定冲头单位压力的主要因素;变薄系数、变形体与凹模间的摩擦和工件外形尺寸R_e值是确定H_opt值的决定性因素。黄铜H62和H68的实验结果表明:理论分析与实验结果比较一致。

ON IRONING WITH CONTOURED DIE OF EQUAL STRAIN RATE BY THE UPPER-BOUND APPROACH

The kinematically admissible velocity .field of ironing with contoured die of equal strain rate has been first put forward in this paper. According to the upper-bound theorem, the influence of technological parameters on the average pressure of punch during the ironing with contoured die of equal strain rate is studied. Meanwhile, with the aid of the minimum energy principle, the optimum height of contoured die (H0pt), which is an essential variable for ironing with contoured die of equal strain rate, has been calculated. The calculated results show that; reduction in thickness, work-hardening effect and friction existing between billet and die are the main factors affecting the average pressure of punch; reduction in thickness, outer dimension of billet (Re) and friction existing between billet and die are the essential variables for determining the value of H0Pt, The experimental results of H 62 (corresponding to ASTM 280) and H 68 (corresponding to ASTM 260) show that the analytical results agree well with the experimental results.