During tube hydroforming process, the friction conditions between the tube and the die have a great importance on the material plastic flow and the distribution of residual stresses of the final component. Indeed, a three-dimensional finite element model of a tube hydroforming process in the case of square section die has been performed, using dynamic and static approaches, to study the effect of the friction conditions on both plastic flow and residual stresses induced by the process. First, a comparative study between numerical and experimental results has been carried out to validate the finite element model. After that, various coefficients of friction were considered to study their effect on the thinning phenomenon and the residual stresses distribution. Different points have been retained from this study. The thinning is located in the transition zone cited between the straight wall and the corner zones of hydroformed tube due to the die–tube contact conditions changes during the process. In addition, it is clear that both die–tube friction conditions and the tube bending effects, which occurs respectively in the tube straight wall and corner zones, are the principal causes of the obtained residual stresses distribution along the tube cross-section.

在管材液压成型过程中，管材与模具之间的摩擦条件对材料的塑性流动以及最终零件的残余应力的分布非常重要。确实，已经使用动态和静态方法对方形截面模具进行了液压成形过程的三维有限元模型，以研究摩擦条件对塑性流动和该过程所引起的残余应力的影响。首先，对数值结果和实验结果进行了比较研究，以验证有限元模型。之后，考虑各种摩擦系数以研究它们对变薄现象和残余应力分布的影响。这项研究保留了不同的观点。稀化位于液压成型管的直壁和拐角区域之间引用的过渡区域中，这是因为在此过程中模具与管的接触条件会发生变化。此外，很明显，分别在管子的直壁和拐角区域发生的模-管摩擦条件和管子的弯曲效应，都是沿管子横截面获得残余应力分布的主要原因。