内压对镁合金差温内压成形起皱行为的影响

针对镁合金管材热态内压成形存在的壁厚不均、膨胀率小等问题,本文提出利用温度差控制变形的差温内压成形新方法,沿管材轴向建立了具有不同温度梯度的温度场,开展非均匀温度场作用下的镁合金管材塑性失稳起皱行为研究,研究了内压对镁合金差温内压成形起皱参数的影响规律。当恒定内压8MPa时,成形后形成均匀的三个皱纹;采用线性增加的内压补料,成形后仅形成均匀的两个皱纹。恒定内压下轴向补料有助于形成更均匀的多点起皱,变内压轴向补料会改变起皱临界条件,提高了成形区材料的稳定性,抑制后续皱纹的形成。

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.