多点模具的拉形工艺及其数值模拟

为检验多点模具拉形工艺的可行性,采用显式有限元软件对抛物柱面与马鞍面件的拉形过程进行了数值模拟,并与采用整体模具的拉形效果进行了比较。数值模拟结果表明:使用多点模具直接进行蒙皮拉形,成形件表面将出现压痕。为抑制压痕,必须在多点模具与板料之间放置弹性垫层。弹性垫能够有效地分散多点模具冲头的集中载荷。当弹性垫较薄时,成形件表面仍有压痕出现,当弹性垫厚度达到8 mm时,压痕被消除,成形表面光滑,与整体模具的成形结果非常接近。实验表明:只要采用合适的弹性垫,多点模具可应用于实际拉形工艺。

Stretching Process Based on Multi-point Die and Its Numerical Simulation

In order to check the feasibility of stretching process based on the multi-point die, the stretching processes of paraboloid and saddle parts were simulated by an explicit finite element software,and the results of stretching based on the multi-point die were compared with those on the conventional solid die. Numerical simulation results show that dimples will occur on the surface of deformed parts if the sheet metal is stretched directly by the multi-point die. To suppress dimple, it is necessary to use a polymer blanket called “elastic cushion” between the multi-point die surface and the sheet metal. Elastic cushion disperses the concentrated load applied by punches of multi-point die effectively. When the cushion was thin, dimples still occured. When the thickness approaches to 8 mm, the dimples are eliminated completely, and the surface of the part is smooth and the forming result approximates the result by conventional solid die. Experimental results show that multi-point die can be applied to the practical stretching process so long as the proper elastic cushion is used.