Effects of Surface Roughness and Visco-Elastic or Elastic-Plastic Characteristics in Ehl

本文用光学干涉技术研究了几种流体在较宽的载荷和速度范围内的圆弹流接触油膜轮廓。为了更清楚地了解表面失效的原因和预防方法，建议从润滑油的凝固现象、接触表面弹性模量的差异、平行于接触表面的压力分量和表面粗糙度的影响等方面来重建弹流润滑理论。主要研究结果如下：（1）纯滚动条件下，油膜弹流润滑表现为类固体行为。而在滑动状态下，弹流润滑油膜的流动特性取决于润滑液的分子结构。也就是说，凝固的或紧密堆积的油在外部剪切力作用下破裂，油膜形状呈现锥形楔， 关于我们 ESS变得比理论预测的薄。然而，一些油在流体和表面之间的界面处或附近滑动，因此它们在通过接触区域期间保持其紧密堆积状态。(2)如果接触体的弹性模量不同，即使滚动或卷吸速度保持恒定，滑滚比也会显著影响弹流润滑膜的形状。特别地，如果具有低弹性模量的表面比具有高弹性模量的表面更快，则在接触表面中出现膜的局部增厚（凹坑），而不是由EHL理论预测的平坦平台。(3)粗糙体在滚动和滑动时表现不同。在纯滚动中，膜的行为几乎与使用光滑表面获得的相同，尽管粗糙体在前缘上由于挤压作用而具有微收缩。而在滑动过程中，微凸体的位置和排列方式对油膜的形状有很大的影响。特别是当存在壁面滑移时，膜的轮廓随时间变化。少

Using optical interferometry technique film profiles in circular elastohydrodynamic contacts are examined with several kinds of fluid under wide ranges of loads and speeds. As a result, it was suggested that in order to have a clearer understanding of the cause of surface failure and methods for its prevention, the elastohydrodynamic lubrication (EHL) theory should be reconstructed by considering the solidification phenomenon of lubricating oils, effects of the difference in elastic moduli of the contacting surfaces, pressure components parallel to the contacting surfaces and surface roughness. The main results obtained are summarized as follows :(1) In pure rolling, the oil film in EHL exhibits solid-like behavior. However, in sliding the flow characteristics of EHL film depend on the molecular structure of lubricating fluids. That is, a solidified or closely packed oil collapses under external shearing force, and the film shape exhibits a tapered wedge so that the minimum film thickn … More ess becomes thinner than the theoretical prediction. Some oils, however, slip at or near the interface between the fluid and the surfaces, and consequently they keep their closely packed state during the pass through the contact region.(2) If the contacting bodies are different in their elastic moduli, the EHL film shape is markedly influenced by the slide/roll ratio even if the rolling or entrainment velocity is kept constant. In particular, if the surface having a low elastic modulus is faster than that having a high elastic modulus, a local thickening of the film (dimple) occurs in the contact surface in place of the flat plateau predicted by the EHL theory.(3) Asperities behave differently in rolling and sliding. In pure rolling, the film behavior is almost the same as that obtained using the smooth surfaces, although the asperity has a microconstriction on the leading edge by the squeeze action. However, in sliding, the film shape is markedly affected by the position and the lay of asperity. In particular, when there exists the wall slip, the film profile changes with time. Less