Kargarnovin - Sharif University of Technology, Tehran, Iran
Ashouri - Sharif University of Technology, Tehran, Iran

In this paper, primarily the possibility of the application of Oyane’s ductile fracture criterion in prediction of bursting failure in tube hydroforming process under combined internal pressure and independent axial feeding is examined. The histories and distributions of stress and strain are calculated by means of finite element method using Oyane’s ductile fracture integral, then the position where the fracture initiates is located and consequently the forming limit is identified. The numerically obtained results are confirmed by on hand experimental results of series of tube bulging tests. Consequently, it is shown that this ductile fracture criterion provides a better method to satisfy the increasingly practical demand for computer aided formability evaluation system in hydroforming process. Then, the region of fracture initiation and the forming limit in hydroforming of a cylindrical tube into a rectangular tube under different forming conditions are predicted by this criterion in this study for the first time. The effects of different parameters such as friction, axial feeding and internal pressure on bursting failure position are studied.

Tube hydroforming; Forming limit; Ductile fracture criterion; FEM