Effect of internal pressure on springback during low pressure tube hydroforming

For the existence of bending deformation during low pressure tube hydroforming(LPTH), springback is unavoidable and deteriorate the forming accuracy. In this paper, an analytical model of springback for LPTH was proposed. The simulation and experiment were carried out to investigate the effects of the main factors on the springback, such as internal pressure, corner radius and thickness. The results indicate that, different from expansion deformation, bending forming is the main and basic deformation for tube forced into the required shape during the LPTH. Consequently, springback appears. However, the deformation type has great dependence on the internal pressure, which ensures the internal pressure of the function to reduce the springback. There is a critical pressure which would induce pure bending deformation and result in the largest springback. Consequently, it need try to avoid the critical pressure for the LPTH. On the contrary, whatever the internal pressure is less or bigger than the critical pressure, springback are all decreased. In contrast, it is more effective to decrease the springback when pressure is bigger than the critical pressure. In addition, bigger corner radius can also contribute to decrease the springback because of a much larger tensile force introduced under the same internal pressure. For a definite component, improving internal pressure is the only method to decrease the springback.