Superplastic Forming/Diffusion Bonding (SPF/DB) of multiple flat and curved titanium alloy sheets is an attractive manufacturing process in the aerospace industry to develop complex components with light weight and high strength, such as wall panels, blades, airfoil surfaces and missile compartments since this forming technology means a relative low cost, accuracy shape, and fine surfaces. However, this technology is also very challenging not only because the forming process of SPF/DB is entirely invisible, but also because the process is controlled synchronously by multiple forming conditions such as press, time, temperature and initial inner structure design. Accordingly, in order to analysis effects of these conditions on the SPF/DB products and provide proper forming suggestion, in this study, numerical simulation is carried out for the flat and curved diffusion bonded multiple sheets. Through the commercial finite element program Marc, the deformed shapes of inner and outer sheets are shown with the variation of the forming time. The effect of optimal strain rate is investigated, the forming press-time cycle is predicted, and the thickness distribution of forming products is provided. Besides, simulations of superplastic flow forming of several sets of sheets with different initial thickness distribution and different diffusion bonding width are also carried. Improper thickness of multiple sheets and diffusion bonding width often cause surface folding or sinking. Consequently, conclusions on how to choose proper thickness for forming sheets and how to set the bonding width are very useful, which can keep the product away from these forming defects and satisfy the given design specification. To verify the simulation results and analysis, experiments of four sets of different thickness sheets and bonding width were carried out. The comparability between them proves that the simulation is successful and correct, and can be used to instruct our experiments.
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