Analytical model for tube hydro-forging: Prediction of die closing force, wall thickness and contact stress

The new forming technology – tube hydro-forging (THFG) was completely different from traditional tube hydroforming, the die closing force instead of internal pressure is the deformation force to compress the cross-section and increase the thickness, also result in a special contact stress state. In this paper, a mathematical model is developed to determine the strain and stress along the tube wall, also predict the die closing force, thickness distribution and contact stress; furthermore, the effects of various factors on the die closing force, thickness distribution and contact stress were discussed. At last, finite element analyses and experiments of THFG are conducted. The experimental and simulation results of die closing force, thickness distribution and contact stress are compared with the theoretical results to verify the correctness of this mathematical model. This model can provide a guideline for determining the technique parameters and designing rational die, also helps in understanding the mechanism of THFG.