柔性和刚性压边方式防止薄板多点成形拉裂的对比分析

采用有限元数值模拟方法研究了薄板鞍型件在有压边多点成形过程中的拉裂现象。提出了能够避免拉裂的柔性压边成形方式,分析了刚性压边与柔性压边成形时的成形极限和成形效果,证明柔性压边成形能够很好地解决板料起皱与拉裂之间的矛盾,并利用压边面中板料的流动分析了柔性压边成形时压边力大小与拉裂之间的关系。当采用刚性压边多点成形时,加大压边力板料可能拉裂,减小压边力板料可能起皱;而采用柔性压边多点成形方式可以有效避免起皱和拉裂,大大提高变形量,得到更好的成形结果。

Contrast study of crack on sheet metal under flexible and rigid blank holders in multi-point forming

FEA numerical method was employed to study the sheet metal crack in the deformation of multi-point forming(MPF),and to analyze the crack of saddle workpiece with blank holder forming.Then a flexible blank holder forming mode was proposed to avoid crack by improving the processes.The forming limits and forming effects of rigid and flexible blank holder formings were analyzed.It was shown that the contradiction between wrinkle and crack can be settled by flexible blank holder forming.The relation between crack and the holding force was also studied by analyzing the sheet metal flow on the surface of the blank holder.Results indicate that in rigid blank holder forming,large holding force may induce crack in the sheet metal,while small holding force may lead to wrinkle.In flexible blank holder forming,both crack and wrinkle can be avoided and the deformation can be significantly increased,thus much better forming result is obtained.