Optimal design of blank thickness in superplastic AZ31 alloy to decrease forming time and product weight

Superplastic forming has drawn growing interest from both automotive and aeronautical fields. It allows to decrease the weight of the product by eliminating fasteners because it can be used to form components with complex shapes that are very close to that of the final product; it can be considered a near-net-shape forming process. This work shows the optimal design of the thicknesses of a blank in AZ31 superplastic magnesium-based alloy to form a complex-shaped product. The adopted optimization method changed a set of geometric parameters of the blank to find the values that make as uniform as possible the final distribution of the product thicknesses. This method led to a blank with a variable thickness. The design was assisted by finite element analysis. The optimized process allowed to obtain, if it is compared to the same superplastic forming process on a blank with a constant thickness, (i) a final product characterized by a more uniform thickness distribution, (ii) a reduction of forming time, and (iii) a reduction of the product weight. It was carried out an experimental activity too that confirmed the convenience of adopting a blank with a variable thickness on which to carry out the forming process.