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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 multi-layer 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.