Research on the effect of the local constraints on sheet hydroforming with the movable die

Abstract

An improved Sheet Hydro‐forming process was put forward, which was researched in the Institute of Metal Research (Chinese Academy of Sciences) and Aalborg University jointly. In this paper, the effects of local constraints on the sheet deformation were researched experimentally. For this case, the local constraints include rigid tools (movable die) and surface roughness of the movable die, especially around the shoulder of the movable die. Finally, ASAME system and FEM are used to analyze the forming process to explain some results that were found in the experiment. In the simulation, the effects of the friction between the movable die and the blank and the movable die on the deformation of the blank are investigated in detail by using the FEM code LS‐DYNA. For the sheet hydroforming with local constraints, the contact between the sheet and the dies affects the material flow and the fracture of the sheet can be avoided. Moreover, the forming limit of sheet metal can be remarkably improved. This process meets the need of the deformation of complicated parts as well as forming of low‐formability and light‐weight materials, such as aluminum lithium alloys and magnesium alloys. The die can be replaced with other die of various shapes, and can also be made of very cheap materials. Thus complex‐shaped sheet parts can be formed with less expensive tool systems.