Development of Tube Hydroforming Technology Using Axial Movable Dies

In order to expand the practical application of tube hydroforming to automotive parts, it is important to develop the technologies for forming complex shapes and to expand the formable range. To meet these demands, the hydroforming technology using axial movable dies is proposed. This method consists of two stages. In the first stage, similar to conventional tube hydroforming, internal pressure and axial feeding on tube edge are applied. In the second stage, the movable die is fed in synchrony with axial feeding cylinders under internal pressure. It is experimentally confirmed that by this method, small corner radius can be achieved with low internal pressure, and thickness deviations in the expanded portion can be made uniform. Furthermore, the application of this method to products with long expanded areas is discussed. This method is effective in suppressing the increase in thickness near the edge of the tube and reducing the thickness at the center of the expanded area. By FE analysis, the effect of friction on the material flow and the deformation behavior in this process is clarified.