中文摘要：

纯挤压条件下弹流油膜的研究已证实了油膜的中央凹陷。研究利用常载荷下的钢球在较小的初始间隙下冲击附有润滑油的玻璃盘,在接触区外围出现了外围凹陷,而不是熟知的中央凹陷。研究结果表明当初始的冲击间隙较大时,油膜的压力分布和厚度以及中心压力-时间曲线中的峰值和接近结束时的中央凹陷都与以前的自由落球问题相似。随着初始的冲击间隙减小,最大压力从接触区中心转换到圆周外围区,相应地,中央凹陷变得越来越不明显而在外围区出现了圆周凹陷,进一步的数值分析,发现当油膜足够厚时在小的初始间隙条件下也出现了外围凹陷。这主要是当初始的冲击间隙变小时,中央油膜厚度比大冲击间隙条件下润滑油被＂冰冻＂时薄很多,中央凹陷不明显;在外围区域,表面间隙很小,局部挤压效应变强,因此形成了外围凹陷。

英文摘要：

Studies about pure squeeze elastohydrodynamic lubrication（EHL） have disclosed a film profile with a central dimple.In this study,the steel ball impacts the steel plate with an oil layer thickness of hoil under an initial impact gap of hini,a circumferential dimple is formed at the periphery of the contact instead of the familiar central dimple,parameter studies show that When the initial central impact gap is large,the film pressure and the film thickness are similar to those in previous free ball dropping problems,including the spike in the central pressure time trace and the central dimple formed at the end of the approach.As the initial impact gap decreases,the maximum pressure changes its location from the contact center to the periphery,correspondingly,the central dimple becomes less distinct and another circumferential dimple appears at the periphery of the contact.Further numerical calculations,under a small initial impact gap the periphery dimple appears when the oil layer is thick enough.In cases where the initial impact gap is small,the central oil film is much thinner than that under large initial impact gaps when the lubricant is ＂frozen＂,and then no marked central dimple can be formed.In the periphery region,the surface gap is closing at a small initial gap and the local squeeze effect in the periphery region becomes strong,and therefore a periphery dimple is generated.