Mechanism analysis on thickness distribution of aluminum alloy hemispherical shells in double-sided sheet hydroforming

Thickness distribution is always an important criterion in evaluating the deformation uniformity of sheet metal shells. In order to study the influence of double-sided liquid pressure on the thickness distribution of aluminum alloy curved shells, a dedicated experimental setup was designed to carry out double-sided sheet hydroforming processes. The thickness distribution of the formed shells were measured and compared under different loading paths. The deformation mode and the stress state were analyzed using simulation results to make a deeply understand on the mechanism of the thickness variation. It is shown that the forward pressure plays a slightly negative role in the thickness distribution of the formed parts. The deformation mode of the shells varies little when added forward pressures in the current experiments. The Von Mises stress and the effective strain of the components are improved when conducting the double-sided hydroforming process. The larger thinning phenomenon when adding forward pressure on the blank is mainly caused by the increasing of reduced third principle stress. This paper can offer suggestions and guides to the future studies about the double-sided sheet hydroforming process.