冲压件侧壁卷曲的机理及控制

Mechanism and controlling of side-wall curl in sheet metal forming

侧壁卷曲现象存在于带法兰零件的弯曲和拉深工序中,其导致的冲压件尺寸和形状偏差会给零件的后续焊接和装配造成困难。该文通过分析零件变形过程及最终应力分布,解释了侧壁卷曲现象的成因。通过有限元模拟,对比压边力和施加方式对侧壁卷曲现象的影响。结果表明,单纯增加压边力不能减少侧壁卷曲,理想情况是分两步施加压边力,行程开始时施加较小的压边力,在行程结束前很小的行程内施加较大的压边力。提出采用浮动拉延筋工艺可获得理想的压边力模型以减小零件的侧壁卷曲。为验证所提出的工艺,制作相应的模具进行带法兰U形件的成形,结果表明,该新型工艺简单易行,能有效减小侧壁卷曲。

Side-wall curl usually occurs in the bending and drawing processes of flanged parts . The shape and dimension errors caused by the side-wall curl bring difficulties in subsequent welding and assembling processes . In this paper , the reason of side-wall curl was explained by analyzing the deforming history and stress distribution at the final forming stage . Using FE simula-tion , the effects of variable blank hold forces and different applying methods on the side-wall curl were compared . The results showed the side-wall curl cannot be reduced by only increasing BHF . A good stage is to apply a small BHF at the beginning of stroke and then to apply a higher value in a very short distance just before the end of forming . Based on this model , a floating draw bead technology is proposed to reduce the side-wall curl . To verify this method , a set of die with floating draw bead was manufactured and used to form U shape parts . The results showed that this technology can effectively reduce the side-wall curl and is easy to apply .