任意形状坯料反挤压成形内圆筒的上限单元技术的改善分析

提出了对任意形状坯料扳挤压成形内圆筒的运动许可速度场改善。

Modified analysis of backward extrusion of internally circular shaped tubes from arbitrarily shaped billets by upper bound elemental technique

A modified kinematically admissible velocity field for the backward extrusion of internally circular shaped tubes from arbitrarily shaped billets is proposed. The original velocity fields appearing in the liberature did not satisfy the condition that the normal velocity on the die and material interface must be zero, and material rotation under the punch was neglected. Therefore, in this work the fomer is corrected and the latter is improved by a new velocity field. From the proposed velocity field, the upper bound extrusion load and average extruded height for regular polygonal shaped billets are determined with respect of the chosen parameters. The theorelical predictions of extrusion load are lower and closer to the experimental results than those in the previous literature. The average extruded height and the grid distortion of theory and experiment agree well when using the proposed velocity field.