Numerical and experimental studies on the new design concept of hydroforming dies for complex tubes

Recently, the tube hydroforming (THF) process has found a remarkable role in the production of tubular parts especially for the transportation industry. In prior research, there were only two parameters, i.e. hydroforming pressure and axial feeding, to play with to obtain a part without any problems like bursting and wrinkling. However, for parts with complex geometries it is sometimes impossible to produce them by changing only these two variables. In this paper a new concept to design THF dies is presented and verified by numerical and experimental studies. By application of this concept, dies will have three parts instead of two, and consequently the tube will be preformed by the die closing before the start of the hydroforming step. The numerical verifications confirmed that without this modification, the production of most of the workpieces with complex geometries is difficult, if not impossible. The numerical results showed good agreement with the performed experiments.