预弯对铝合金管材内高压成形缺陷与尺寸精度的影响

铝合金异形截面管件是实现汽车结构轻量化的有效途径之一,其成形工艺是先将铝合金管材经过数控弯曲获得轴线形状,然后进行内高压成形。弯曲产生的回弹、截面畸变及起皱等缺陷会影响后续内高压成形的质量。本工作通过建立管材塑性弯曲的理论模型和材料模型,计算任意弯曲角度的卸载回弹量,在弯曲过程考虑回弹量补偿,有效避免了内高压成形时的咬边缺陷。通过改善芯轴条件,使用带有一个芯球的芯轴,使截面不圆度由7.55%降低至1.43%,避免了弯曲件在内高压成形时发生破裂。同时对弯曲产生皱纹的管件进行内高压成形,证实了内高压成形过程不能够消除管件在弯曲过程形成的起皱。通过工艺实验研制出6063铝合金异形截面管件,获得了无缺陷的成形件。对47个内高压成形件进行尺寸精度测量,最大尺寸偏差为1.08mm(1.63%),尺寸和精度符合设计要求。

Effects of Pre-bending on Defect and Dimensional Precision in Hydroforming of Aluminum Alloy Tube

Hydroformed aluminum hollow components with various sections have been widely used in the field of automotive lightweight engineering.The main manufacturing process of the component is that the tube is pre-formed by CNC bending, and then hydro-formed into the desired shape.The springback, cross section distortion and wrinkling defects caused by bending will affect subsequent hydro-forming process.Theoretical model of tube plastic bending and model of material were established, and the theoretical springback value of any bending angle was obtained by the combination of equilibrium equation and total strain theory, the undercut defect was avoided effectively during hydroforming.The cross section un-roundness was decreased from 7.55% to 1.43% by the improvement of the core shaft, and the fracture of bend tube during hydroforming can be significantly avoided.The wrinkle defects formed in tube bending cannot be eliminated by hydroforming.The 6063 aluminum components with various sections were developed by the technology experiment, and the parts without any defects were obtained.The dimensional precision of 47 hydroformed components were measured, and the maximum dimensional deviation is 1.08mm (1.63%), and the dimensional precision meets the requirements.