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Preform Shape Design in Tube Hydroforming Process Using Equi-Potential Line Method

The quality of a tube-hydroformed component and the tooling cost and processing time involved in the process are notably affected by the component's preform. Hence, it is necessary to produce a proper preform shape for the successful hydroforming from the initial tube to final shape. In this article, a new technique based on the equi-potential line (EPL) designed in the electric field was used for the first time to find an appropriate preform shape in THF (Tube Hydroforming) process. The equi-potential line generated between two conductors of different voltages show similar trends for minimum work path between the initial and final shapes. Based on this similarity, the equi-potential line obtained by arrangement of the initial tube and final die was used for preform design. The finite element (FE) method was employed to find the forming pressure to form the preform shape in the die cavity, and then the effectiveness of this method was compared with previous methods. It was shown that the new method was simpler and more accurate than the other methods in finding the preform shape. Finally, experimental tests were carried out to verify the FE results. For this, a tube inside the square die was considered and its preform shape was extracted from EPL method, then its forming pressure from finite element modeling was used in a THF process. From the results, the prediction of the preform shape by using the EPL method demonstrated to be reasonable. In addition, there was an acceptable agreement between experimental and FE results. As a result, this approach can be extended to a wide range of practicable tube hydroforming processes.