Numerical and experimental investigation of the effect of the pressure path on forming metallic bellows

Abstract

Tubular metal bellows have wide applications in different industries. They are mainly manufactured in the open die hydroforming process, which comprises two stages of bulge and closing (final forming). In this paper, the effect of pressure path on forming bellows in both stages was studied by finite element simulation and experiment. The results obtained from simulation illustrated that the pressure path influences the production of the desired parts, or the occurrence of bursting or wrinkling defects in the products. Experiments were carried out to verify the simulation results. By using the simulation and experimental results a comprehensive forming window for bellows was presented. Based on this forming window, the wrinkling and bursting defects for bulge and closing stages, and the safe zone for producing the desired part were determined. The study also showed that the number of convolutions does not influence the internal pressure and maximum forming load, but affects the forming energy.