Prediction of blow forming profile of spherical titanium tank

When manufacturing spherical titanium tank by superplastic blow forming, it is important to obtain uniform thickness distribution of the tank in terms of performance. In the current study, the optimization of thickness distribution of diffusion bonded initial blank and the prediction of the thickness at final forming stage have been carried out by using theoretical equations available in reference and finite element methods for superplastic blow forming process. The analysis has been carried out for each case of using uniform blank, profiled one, and optimized blank without boss. The optimized blank resulted in almost uniform thickness of final product, however, slight thinning phenomena near the boss was observed because of large size of boss. Also, the final thickness deviated a bit from the target thickness. This resulted from that the equation employed for the current study was driven without considering the boss diameter, and the difference of boundary condition. Therefore, since the region near boss is a region where stress concentration occurred under internal pressure loading, more improved theoretical or empirical optimization should be followed to prevent from thinning near boss and to maximize the performance of the tank.