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

采用光学干涉测量技术，研究了不同流体在不同载荷和速度下的圆形弹流接触中的膜形。结果表明，为了更清楚地认识表面失效的原因和预防方法，应考虑润滑油的凝固现象、接触面弹性模量差异的影响、平行于接触面的压力分量和表面粗糙度的影响，重构弹流动力润滑理论。主要研究结果如下：(1)纯轧制时，EHL中的油膜表现为类固体行为。然而，在滑动中，EHL膜的流动特性取决于润滑流体的分子结构。即凝固或紧密堆积的油在外力作用下坍塌，油膜形状呈锥形楔形，使最小油膜厚度比理论预测的薄。然而，有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时保持紧密的堆积状态。(2)当接触体的弹性模量不同时，即使保持滚动速度或夹带速度不变，滑滚比对EHL膜的形状也有显著影响。特别是，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，则接触面会出现局部增厚（凹陷），而不是EHL理论预测的平坦平台。(3)凸起在滚动和滑动中的表现不同。在纯轧制中，薄膜的行为与使用光滑表面时几乎相同，尽管在挤压作用下，粗糙的前缘有微收缩。然而，在滑动时，膜的形状明显受到位置和粗糙层的影响。特别是当存在壁滑移时，膜的轮廓随时间而变化。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