Investigation of the generation mechanism of the internal pressure of metal thin-walled tubes based on liquid impact forming

Liquid impact forming (LIF) is a new type of composite forming method based on tube hydroforming (THF) and stamping forming. It has high efficiency and low energy consumption, with no need for external pressure source, so LIF has good development prospect and application value in the field of lightweight and integrated manufacturing. In order to investigate LIF technology, the generation mechanism of the internal pressure was analyzed in this paper. Firstly, based on the theory of the liquid volume compression, the change law of the cavity volume of metal thin-walled tubes was analyzed according to size parameters of the tube and dies during the forming process. The mathematical relationship between the internal pressure in the tube cavity and clamping parameters (clamping speed and clamping height) was obtained under the impact load. Then, the theoretical maximum internal pressure Pmax1 was discussed under different die cavities. Furthermore, the relationship between the internal pressure in the tube and the clamping time under different die cavities with a same clamping speed was obtained according to the transient dynamic analysis by ANSYS Workbench. At the same time, the simulated maximum internal pressure Pmax2 and the calculational maximum internal pressure Pmax were acquired under different die cavities. In addition, the LIF experiments were performed using a simple and suitable device to verify the calculational maximum internal pressures under die cavities with different side lengths. Through the comparison of the calculational and experimental maximum internal pressures, it is not difficult to find that the values of both showed a good agreement and the maximum deviation is 10.27%. The research results indicate that the theoretical equation of internal pressure of metal thin-walled tubes based on LIF is reliable, and it will lay a good foundation for further study.