Development of an automotive rear subframe by the tube hydroforming process

The automotive industry has shown a growing interest in tube hydroforming during recent years. The advantages of hydroforming (less thinning, a more efficient manufacturing process, etc.) can, for instance, be combined with the high strength of extra-high-strength steels, which are usually less formable, to produce structural automotive components which exhibit lower weight and improved service performance. Design and production of tubular components require knowledge about tube material and forming behaviour during hydroforming and how the hydroforming operation itself should be controlled. These issues are studied analytically in the present paper. In this study, the whole process of rear subframe parts development by tube hydroforming using steel material having a tensile strength of 440 MPa is presented. At the part design stage, it requires a feasibility study and process design assisted by computer aided engineering to confirm hydroformability in detail. The effects of parameters such as internal pressure, axial feeding, and geometry shape in the automotive rear subframe by the hydroforming process were carefully investigated. The overall possibility of hydroformable rear subframe parts could be examined by cross-sectional analyses. Moreover, it is essential to ensure the formability of tube material on every forming step such as pre-bending and hydroforming. In addition, all the components of a prototyping tool are designed and interference with a press is examined from the point of geometry and thinning.