Plane Strain Simulation for Corner Fill of Hydroforming Tubes in Oversized Die

Corner fill is a simple benchmark conceived to gain knowledge of tube hydroforming. In corner fill of tube hydroforming, an originally long round tube is positioned in a cylindrical die with square cross-section and expands under applied internal pressure to fill the corners of the die. In order to ensure burst of the tubes, the cross-sectional dimension of the square die is chosen to be greater than the outer diameter of the tube. A two-dimensional plane strain finite element model has been developed to study the tube behaviors under applied internal pressure. This model treats the corner fill process more realistically than shell elements models because thickness stress and distortions of a normal segment through the thickness of the tube can be simulated [Chen, 2004]. The calculated results of stress and strain and the change of tube geometry as functions of pressure are presented. The results show that the obtained radial expansion and pressure relations agree excellently with experiments. However, bursting failure predicted using various failure criteria underestimate the burst pressure and radial expansion. How to reduce this discrepancy will be the subject of further investigations.