管壁异形渐进翻孔成形的力与变形特征分析

Analysis on force and deformation characterisitics of incremental hole-flanging on tube wall with special shapes

管壁渐进翻孔成形是传统渐进成形这一柔性成形工艺的重要扩展。针对圆管与方管管壁的长圆形和矩形翻孔,设定了8组渐进成形参数的加工方案,探讨了不同加工条件下管壁变形特点及其影响因素。研究发现:采用改进工具头以及"预翻+整形"方式,能够实现曲面结构的复杂翻孔加工;由于几何形状和材料流动性的差异,方管渐进翻孔的成形载荷远大于圆管渐进翻孔的成形载荷;就不同翻孔位置的减薄率而言,圆弧端最大、圆弧过渡端次之、直壁端最小。采用增加渐进翻孔的预翻量、选择直壁端进刀、减小进给量,以及采用顺-逆时针相结合的递进方式等措施,有助于消除破裂、金属堆积等缺陷,从而提高管壁渐进翻孔成形质量。

The incremental hole-flanging on tube wall is an important extension of traditional incremental forming,which is a flexible forming process.For the oval and rectangular hole flanging on circular and square tubes,the processing schemes for eight groups of incremental forming parameters were set,and the characteristics of tube wall deformation and its influencing factors under different processing conditions were discussed.The results show that the complex hole-flanging on curved surfaces can be realized by improved tool head and’pre-flanging+shaping’process,and the forming load of incremental hole-flanging on square tubes are larger than that of circular tubes due to the difference of geometric shape and material fluidity.In terms of the thinning rate at different hole-flanging positions,the arc end is the largest,the transition end is the second,and the straight wall end is the smallest.Adopting measures such as increasing the pre-flanging amount during incremental hole-flanging,selecting the straight wall end feeding,reducing the feeding amount and adopting the progressive method combining clockwise and counterclockwise can eliminate the defects,such as cracking,metal accumulation and so on,which improve the forming quality of incremental hole-flanging on tube wall.