Double-sided high pressure hydroforming of thin-walled aluminum alloy tube

A new process parameter, external pressure, Is Introduced to achieve favorable tri-axial stress state during deformation process. The experiment and numerical simulation of double-sided hydroforming of thin-walled aluminum tube was carried out. The maximum external pressure Is 100MPa, a little bigger than the yield stress of the material. The bursting pressure, distribution of the expansion ratio and thickness were measured and analyzed. The stress state was discussed. It Is shown that the external pressure will provide back support to the tube material and larger tube expansion could be achieved. And bigger thickness reduction could be obtained without bursting. For part with the same thickness reduction, the hoop stress was lower with high external pressure. So the formability of the material was elevated by adding the external pressure.