Outflow characteristics of a pressure medium during sheet hydroforming and its finite element modeling

板材液压拉深是一种利用液压代替凹模的拉深工艺，在各个行业中受到了广泛的关注。本文研究了板料液压成形过程中压力介质的流出特性及其数值模拟方法，可用于板料液压成形过程的有限元模拟。我们提出了一个数值模型来预测压力介质在过程的初始阶段的临界流出压力。在达到临界出流压力后，水压随板料变形的变化较大，这说明在进行精确的数值模拟时，应考虑水压的这种变化。

Sheet hydroforming is a deep-drawing process in which hydraulic pressure is employed instead of a female die, and is drawing a lot of attention in various industries. In this study, the outflow characteristics of a pressure medium during sheet hydroforming and their numerical modeling that can be utilized in finite element simulations of sheet hydroforming processes were examined. We proposed a numerical model to predict the critical outflow pressure of a pressure medium at the initial stage of the process. We also revealed that, after the critical outflow pressure is reached, the hydraulic pressure changes largely with the sheet deformation, suggesting that such a change in the hydraulic pressure should be taken into consideration to conduct accurate numerical simulations.