矩形截面件开式液压成形变形规律及起皱行为

Deformation and Wrinkling Behavior in Hydroforming of Square Overlapping Parts

目的开式筒壳液压成形采用具有搭接结构的开式筒壳作为坯料,具有提高成形能力、改善壁厚分布、降低成形压力等优势。旨在以矩形截面件为对象,研究内压作用下开式筒壳的圆角充填行为。方法采用数值模拟手段,分析了矩形截面件开式液压成形过程中的应力应变变化及成形缺陷。利用内高压成形机和自主研制的自密封装置,开展了搭接区中点分别位于圆角区、过渡区和直边区3种搭接位置条件下的矩形截面件开式液压成形实验研究。结果模拟和实验结果表明,开式筒壳搭接区的外层为易起皱区。当搭接量为80 mm且搭接区中点位于圆角区时,模具型腔的外压作用有效抑制了起皱的形成。4个圆角中距离对应搭接位置最近的圆角最先完成充填。搭接区域所在位置的壁厚减薄率显著低于其他区域,3种条件下成形件中间截面的最大减薄率分别为10.4%、9.8%和10.2%,搭接区中点位于过渡区时最大减薄率较低。结论采用一定搭接量的开式筒壳比封闭截面管坯更有利于圆角的充填。选取适宜的搭接位置可避免成形过程中起皱缺陷的产生。此外,搭接位置对开式筒壳圆角充填的应力应变分布、圆角半径以及壁厚分布起到重要作用。

Hydroforming of overlapping blank that uses overlapping blanks rather than traditional tube with closed cross-sections has distinct advantages such as enhancement of forming ability,improvement of wall-thickness distribution,reduction of forming pressure,etc.The work aims to study the corner filling behavior in hydroforming of square overlapping parts.Stress and strain variation and forming defects of square overlapping parts were revealed through numerical simulation.Hydro-forming machine and the self-sealing device were adopted to perform the experimental investigation on the hydroforming of square overlapping parts at three overlap positions including corner,transition,and straight side.Simulation and experiment re-sults showed that the out layer of the overlapping blank was prone to wrinkling.Wrinkles were controlled by the external pres-sure of the die cavity when the mid-point of overlap was located on the straight side of the blank at the overlap amount of 80 mm.It was found that among the four corners,the one closest to the overlap was filled firstly.In addition,the thinning ratio in the overlap area was significantly lower than that in other areas,and the maximum thinning ratio of the middle section of the formed part under three conditions was 10.4%,9.8%and 10.2%respectively.The maximum thinning ratio was the smallest when overlap was located on the transition area.It can be concluded that the overlapping blank with a certain overlap is more beneficial to the filling of corner than the closed cross-section blank and choosing a suitable lap position can avoid wrinkling defects in the forming process.The overlap position has a significant effect on forming defects,stress and strain distributions,corner radius,and wall-thickness distribution.