Effects of internal pressure on wrinkling in warm tube hydroforming

Abstract

Effects of internal pressure on critical wrinkling stress, stress–strain state during the wrinkling and thickness distribution of the wrinkles in warm tube hydroforming were investigated through mechanics analysis, finite element simulation and hydroforming experiments of an AZ31B magnesium alloy tube. In mechanics analysis, the critical circumferential stress and axial stress for the onset of axisymmetric wrinkling were derived. The relationship among the ratio of axial to circumferential stress, the critical wrinkling stress and the internal pressure were analysed. At last, the effect of internal pressure on the stress tracks and thinning ratio distribution was discussed according to the simulated and experimental results.

Keywords:

• Internal pressure
• Critical wrinkling stress
• Warm tube hydroforming

The authors are grateful for support from the National Natural Science Foundation of China (grant no. 51075100) and the Program for New Century Excellent Talents in University (grant no. NCET‐07‐0237), China.