Design sensitivity analysis and optimization of the hydroforming process

Tube hydroforming has recently been drawing the attention of the automotive industries due to its several advantages over conventional methods. It can produce a wide range of products such as sub-frames, engine cradles, and exhaust manifolds with cheaper production cost by reducing the overall number of processes. The tube hydroforming process is based on the use of internal pressure combined with axial load. Successful tube hydroforming depends on the reasonable combination of the internal pressure and the axial load at the tube ends. This paper deals with the optimal process design (internal pressure and axial load) of the hydroforming process using numerical simulation by the explicit finite element code combined with an optimization tool. An optimization technique is used in order to minimize the tube thickness variation by determining the optimal loading path in the tube expansion forming and the sub-frame forming process. The optimization is performed by means of a gradient-based method including sensitivity analysis.