Experimental and numerical investigation of single and bi-layered tube hydroforming using a new sealing technique

Tube hydroforming is a metal-forming technology process with expanding applications, particularly that is growing used in the production of hollow and complex-shaped parts in automotive and aerospace industry. One of the challenges of industrial tube hydroforming processes is the low formability of multi-layered tubes. Friction plays an important role in tube hydroforming due to the high contact pressure between the surface of the die and tube. Friction force affects the tube formability by preventing the material flow toward the deformation zone. In this research, a new sealing method is used to eliminate the internal pressure in the feeding zone. As a result of this, the friction force between the tube and the die is removed from this zone and flowing of the material toward the deformation zone is improved. First, the new sealing method was examined in a free bulge formation of aluminum tubes. The results show that the new sealing method can increase the formability of aluminum tubes by 19% compared with the conventional sealing method. Finite element simulation of the free bulge formation was performed in Abaqus software with different process parameters. During the simulations, the forming limit curve obtained from the experimental tests was used for the prediction of necking. Results showed that increasing of the friction coefficient increases the formability of the aluminum tubes in the new sealing method. In addition to that, the formability of parts was improved in bi-layered tubes by this technique.