Application of segmented rubber rings to increase the sealing efficiency in hydroforming

The tube hydroforming process uses a pressurized fluid as the forming medium, and the sealing efficiency of the internal fluid has an important influence on the hydroformability. This study investigates the applicability of segmented rubber rings to prevent pressure leakage in hydroforming. When the target shape is non-axisymmetric, the possibility of pressure leakage is increased due to the biased stress distribution on the punch. A sealing system is proposed, which is composed of segmented rubber rings, a cylindrical sleeve, and a punch with an end fillet. When the rubber rings are compressed, the reaction force acting on the rings contributes to the prevention of pressure leakage. The circumference of the tube end becomes more tightly sealed by the axial pressure between the punch and sleeve. A deformation analysis was conducted using a compression test, which revealed that the combined use of a steel ring with a rubber ring was more efficient in preventing fluid leakage. The enhanced sealing effect of the proposed system with rubber and steel rings was confirmed by comparing the experimental results with a conventional hydroforming process.