Thickness distribution in the guiding zone of hydroforming of tube with variable cross sections

The analytic formula of the feeding zone thickness distribution in hydroforming of variational cross-section tube is derived by using the total strain theory. The formula shows the effect of initial length of feeding zone, friction coefficient, and internal pressure, on the thickness difference between two ends of feeding zone quantitatively, and the analytic results have good agreement with the FEM. The results show that with the increasing of initial length, friction coefficient and internal pressure, the thickness difference between two ends of feeding zone increased, namely the thickening of outer end increased. The thickening of feeding zone prevention can be realized by shorting the initial length of feeding zone, decreasing the friction coefficient and choosing low internal pressure.