Prototype tryout and die design for automotive parts using welded blank hydroforming

Hydroforming is the technology that utilizes hydraulic pressure to form tube and sheet materials into desired shapes inside die cavities. It can be characterized as tube hydroforming and sheet hydroforming depending on the shape of used blank. Hydroforming offers several advantages as compared with conventional manufacturing via stamping and welding, such as part consolidation, weight reduction, improved structural strength and stiffness, lower tooling costs, fewer secondary operations, tight dimensional tolerances, low springback, and reduced scrap. In this paper, the welded blank hydroforming (WBH) technology is discussed in the aspects of formability, and the engine mount bracket and the subframe are analyzed and manufactured for the application of the technology, which have been manufactured by stamping and welding processes. Die geometry and process parameters are suggested by the computer simulation using the explicit finite element code, PAM-STAMP™. Various defects, especially wrinkling in the area of big difference of die depth and large height deviation of the die flange face, are investigated and analyzed. The numerical results are compared with prototype tryout results, and the wrinkling and the local thinning under different forming conditions are predicted.