双锥形管液压成形过程中破裂和起皱的力学条件

针对双锥形管液压成形过程,分析了破裂和皱纹产生的几何及力学原因,并用数值模拟和工艺实验进行了验证。研究结果表明,有益皱纹需要同时满足几何条件和力学条件。几何条件是补料结束时形成的局部皱纹表面积略小于零件相应的表面积。力学条件是皱纹形状参数G不小于中间皱峰半径R,皱峰在后续高压整形过程中壁厚无减薄。当几何条件不满足时,即坯料任一段表面积大于零件相应表面积会起皱,过小会破裂:当力学条件不满足时,整形过程中中间皱峰发生开裂。

Stress Conditions of Bursting and Wrinkling during Hydroforming of Double-Cone Tube

Firstly,the geometry condition and the stress condition of the bursting and wrinkles during the hydroforming of double-cone tube were given.Then the analytical results were compared with the FEM analysis and experiments results.The results show that the useful wrinkles must meet both the geometry condition and the stress condition.The geometry condition of useful wrinkles is that the area of workpiece in the local zone at the end of axial feeding is close to the area of the corresponding part.The stress condition of useful wrinkles is that shape parameter G is not smaller than the radius R at the top of middle wrinkle.That means the increment of thickness strain det is positive and no thickness thinning will occur during the calibration.When the wrinkles didn’t match geometry condition,the dead wrinkles and the bursting will take place.And when the wrinkles didn’t match stress condition,the bursting at top of middle wrinkle will occur during the calibration.