反挤压成形内圆筒上限单元技术研究

在以前各种著作中出现的速度场不满足在模具和材料接触面的法线速度必须为零的条件，而且忽略了冲头下面的材料旋转，对上述的不足之处进行了改进，利用新的速度场，本文中挤压载荷的理论计算值比以臆文献中出现的低，但更接近实验结果；平均挤压高度计算与实际情况吻合较好。

Backward Extrusion of Circular-cylinder by the Upper-bound Elemntal Technique

The original veocity fields appearing in the liberature did not satisfy the conditionthat the normal velocity on the die and meterial interface must be zero, and the rotation ofmaterial under the punch was neglected. In this paper, the former is corrected and the latter isimproved by a new velocity field. From the proposed velocity field, the upper-bound extrusionload and average extruded height for regular polygonal-shaped billets are determined with respectto selected parameters. The theoretical predicted extrusion loads are lower than those in the previousliterature and c1ose to the expermental results that the calculated average extruded height andagrees well with experment.