Effect of internal pressure on wrinkling behavior of magnesium alloy tube in warm hydroforming with non-uniform temperature field

Tube warm hydroforming of Mg alloy tube usually induces poor thickness uniformity and low expansion ratio, therefore, a new warm hydroforming process with non-uniform temperature field is presented. The temperature field along the tube axis with different temperature gradient is established to control the plastic deformation behavior of the tube blank. The plastic wrinkling tests of Mg alloy tubes with non-uniform temperature field are carried out, and the effect of internal pressure on wrinkling behavior of magnesium alloy tube in warm hydroforming with non-uniform temperature field is studied. The results show that three uniform wrinkles can be formed when the internal pressure is kept as a constant, and only two uniform wrinkles can be formed using linearly increasing internal pressure. Axial feeding with constant internal pressure contributes to the formation of uniform multi-point wrinkling, but the axial feeding with linearly increasing internal pressure can change the critical conditions of wrinkling, which improve the stability of forming zone and inhibit the formation of subsequent wrinkles.