一步逆成形法中边界等效阻力的自适应算法

在一步逆成形法中,如果最终构形只包括零件型面,为了得到合理的毛坯形状,需将压边圈的摩擦阻力以及拉深筋的阻力等效到零件边界线的节点上,根据实际经验给出等效阻力的大小。但是等效阻力的大小并不是均匀分布的,如果视为均匀分布,势必造成较大误差,如果分段手动给定,则效率太低,这里提出一种边界等效阻力的自适应算法。算法首先通过线弹性反向变形求得零件在无边界等效阻力作用下的毛坯外轮廓线,假设边界等效阻力的大小与该外轮廓线与零件边界线相应单元边之间的距离成正比,从而实现等效阻力的自适应分布。并以两个典型冲压件为例,通过比较等效阻力自适应算法、等效阻力均布算法、利用商业化软件Fastform分段手动给定阻力的大小和多次试验这四种不同方法得到的零件毛坯外轮廓线,验证了这一算法的有效性和便捷性。

Self-adaptive Algorithm of the Equivalent Resistance on the Boundary Line in One-step Inverse Analysis

In one-step inverse analysis, the resistance produced by the blank holder or draw bead should be given by experience and then equivalent to the nodal force on the boundary line for obtaining a rational blank shape if the final configuration only contains the part surface. However, the resistance is not distributed uniformly. Handling as uniform distribution will cause big error. Giving manually section by section is inefficient. Here, a self-adaptive algorithm of the equivalent resistance is introduced. In the algorithm, firstly the initial configuration is obtained by linear elastic reverse deformation without considering any resistance. Then the resistance is assumed to be in direct proportion to the distance between the above mentioned initial configuration and the part contour line. In this way, the equivalent resistance can be distributed adaptively. To confirm the algorithm’s validity, two typical stamping parts are presented as examples. By comparing four different results respectively obtained by non-uniformly distributed resistance algorithm, uniformly distributed resistance algorithm, giving resistance manually section by section, a commercial software Fastform and trial and error, this self-adaptive algorithm is proved accurate and convenient.