Analysis and finite element simulation of the tube bulge hydroforming process

The purpose of this paper is to evaluate the quality of the tubes produced by bulge hydroforming processes. A mathematical model considering the forming tube by an ellipsoidal surface is proposed to examine the plastic deformation behaviour of a thin-walled tube during the bulge hydroforming process in an open die. In the formulation of this mathematical model, non-uniform thinning in the free-bulged region and sticking friction between the tube and die are considered. In the sticking friction mode, the elements after contact with the die do not move or slide. Secondly, the tube bulge hydroforming process in an open die is analysed by using the finite element code “DEFORM”. The relationship between the internal pressure and the bulge height of the tube is examined. The effects of various forming parameters, such as the die entry radius, the initial thickness, the initial length of the tube, etc., upon the forming pressures are discussed systematically.