轴对称塑性变形区内一点流动方向的探索

INVESTIGATION ON FLOW DIRECTION OF A POINT IN AXISYMMETRIC PLASTIC DEFORMATION

为研究塑性变形体中金属流动方向与局部应力场之间的关系,首先给出塑性变形中局部应力场的平均应力梯度的近似求解算法,并计算圆柱体镦粗、圆环镦粗和正挤压塑性区等典型轴对称应力场中各点的平均应力梯度方向。将应力场中各点的平均应力梯度方向和速度方向同时可视化,并对比统计二者的相似程度,结果显示在轴对称应力场中质点的流动方向与平均应力梯度方向大致保持一致。将变形区中各点的运动分解为刚体运动和相对运动(流动)两个分量,认为刚体运动主要由工具运动决定;在不考虑刚体运动的情况下,轴对称塑性变形区中的质点流动方向与附近区域的局部应力场在该点的平均应力梯度方向大致保持一致。

In order to investigate the relationship between the flow direction of a point and local stress field in plastic deformation, an approximate solve algorithm is carded out to calculate the maximum mean stress gradient direction of local stress field. The algorithm is applied to calculate the maximum mean stress gradient directions in stress fields of typical axisymmetric problems, such as cylinder compression, ring compression and extrusion. Then the maximum mean stress gradient directions and the flow directions of points are visualized and compared. Good similarity is found between the movement direction and the maximum mean stress gradient direction of the related local mean stress field in the deforming bodies. Furthermore, the motion of a point in plastic deformation is decomposed into two components： the motion of rigid body and the relative motion. The motion of rigid body is mainly determined by tool motion, while the relative motion is consistent with the maximum mean stress gradient direction.