Analytical and numerical analysis of bursting failure prediction in tube hydroforming

In this paper, bursting failure in tube hydroforming under combined internal pressure and independent axial feeding is predicted analytically and numerically. To predict the initiation of necking the Swiftʹs criterion for diffuse plastic instability is adopted based on the Hillʹs general theory for the uniqueness to the boundary value problem. In addition, in order to predict fracture initiation the Cockcroft and Lathamʹs ductile fracture criterion is introduced and evaluated from the histories of stress and strain calculated by means of finite element analysis. Finally, from the comparison with a series of tube bulge tests the prediction of the bursting failure based on the plastic instability and the ductile fracture criterion demonstrates to be reasonable so that these approaches can be extended to a wide range of practical tube hydroforming processes.