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

Abstract

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.

Keywords

• CNC bending
• hydroforming
• springback
• cross section distortion
• wrinkling