Numerical Simulation of Superplastic Forming of AA7475 Aluminum Alloy in a Circular Die

Superplastic materials undergoe large amount of plastic deformation. Since large plastic strains can be achieved at relatively low flow stresses, this process leads to considerable industrial interest in superplastic forming of aircraft parts, automobile parts etc, which require relatively high tooling and assembly cost. Therefore, the superplastic forming has become an alternative process to manufacture those components which require fewer stages with minimum wastage. The aim of this paper is to explore the superplastic deformation behavior of the AA7475 aluminum sheet during blow forming in to a circular die by numerical simulation using the Finite element package, C++, and validation with the reported results of experiment. In the theoretical modeling of superplastic forming at every stage of forming, the bulge is assumed to be a part of sphere. From this, a geometric relation is established to predict the thickness distribution, radius of curvature of the dome, height and radius of the bulge at various points of bulging during forming. In the FEM approach, a circular die is modeled and on the top of which AA7475 aluminum alloy blank is fixed rigidly around the die periphery and constant pressure is applied, which is numerically simulated using the FEM package to predict the bulge height as a function of time over the buying profile.