Investigation on preformed shape design to improve formability in tube hydroforming process using FEM

A selection of proper tubular blank and a suitable preformed tube shape as well as a reasonable combination of the internal pressure and the axial feeding are essential parameters for successful tube hydroforming processes (THF). A carefully selected preformed shape can be considered as a key factor for successful THF, since thinned sections may not be able to endure internal pressure during expansion, and consequently burst, whereas excessive thickening may lead to wrinkles. This paper introduces a novel numerical approach as an effective tool to design the preformed shape in order to improve the formability based on the deformation history during forward numerical simulation about THF. This numerical approach is implemented in a simple free bulge case in order to be able to enhance the formability. The results proved to be successful on its effectiveness and feasibility. Consequently, it is shown that the novel numerical approach, proposed in this paper, with which to design the preformed shape will provide a feasible method to satisfy the increasing practical demands for enhancement of the formability in THF.