Abstract:

Numerical analysis was carried out for pure squeeze EHL of free falling ellipsoid.Through reasonable definition about dimensionless parameters of velocity,acceleration and mass,dimensionless form of kinetic equation and dimensional form were unified.Multigrid method of a quarter of domain was used
herein for saving time.Numerical results reveal that,in the whole striking process,appearing and changing of the central pressure and edge-peak pressure are analyzed,and when the ellipsoid leaves the oil,these pressures are combined into a high pressure.A dimple of surface is produced by the effect of pure squeeze,and the pressure is distributed in the dimple.In addition the bigger ellipticity ratios,the shorter striking time,the less change of film thickness and the earlier inflection point of the curve.At last,the numerical simulation of the curve of the central pressure against time achieved by Safa and Gohar in their experiment is performed,and  the simulation results are close to the test curve, which prove the correctness of the procedure.

Key words: pure squeeze, elasto-hydrodynamic lubrication(EHL), ellipsoid, free falling

摘要：

通过数值求解分析了椭球自由下落的纯挤压弹流润滑问题,通过合理定义速度、加速度和质量的量纲一参数,使得动力学方程的量纲一形式与有量纲形式得到了统一。使用多重网格技术在直角坐标系下的1/4域上求解，大大缩短了计算时间。数值计算结果表明：在整个撞击和反弹过程中，先有中心压力再有边峰压力，在椭球即将离开油膜时二者重合;油膜的纯挤压效应使得弹性表面出现了凹陷，压力主要分布在该凹陷区域内，而且凹陷里的油膜承受了主要的外部载荷。另外，椭圆比越大，整个撞击过程持续的时间越短，膜厚的变化越平缓，曲线的拐点越提前。最后,对文献\[11\]的试验曲线进行了数值模拟,理论曲线与试验曲线的吻合验证了程序的正确性。

关键词: 纯挤压, 弹流润滑, 椭球, 自由落体