The superplastic forming technology of Ti-6Al-4V titanium alloy bellows

A new forming technology for bellows, which uses a combined superplastic forming (SPF) method by applying gas pressure and an axial compressive load, is developed. It can be used to fabricate large diameter U type titanium alloys bellows. Compared with conventional methods, the method has the advantage of low cost, high dimension accuracy and a high rate of finished products. During the SPF process, the tubular blank is restrained in a multilayer die. The final dimensions of the bellows conform to corresponding dies. In order to obtain optimum thickness distribution of the components, the load route is divided into three stages - free bulging, clamping and calibrating. Numerical simulations of this bellows SPF process are performed using a rigid visco-plasticity shell finite element code that was developed by the authors. Simulation results show great agreement with the experiments.