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

利用光学干涉测量技术，在较宽的载荷和速度范围内，测量了几种流体在圆形弹流接触中的膜层分布。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、接触面弹性模差、平行于接触面的压力分量和表面粗糙度的影响，对弹流润滑理论进行重构。主要研究结果如下：(1)纯轧制条件下，弹流润滑油膜呈现类固体行为。然而，在滑动过程中，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的作用下坍塌，油膜形状呈锥形楔形，因此最小油膜厚度为…更多的ESS变得比理论预测的更薄。然而，有些油在流体与表面的交界处或附近滑移，因此在通过接触区时保持紧密堆积状态。(2)如果接触体的弹性模数不同，即使滚动或卷吸速度保持不变，滑滚比也会显著影响弹流润滑油膜的形状。特别是，如果弹性模数较低的表面比弹性模数较高的表面速度快，则在接触面处会出现局部增厚(韧窝)，而不是弹流理论所预测的平坦平台。(3)粗糙表面在滚动和滑动过程中表现不同。在纯轧制中，虽然由于挤压作用，粗糙表面在前缘有微缩，但薄膜的行为与光滑表面的薄膜行为几乎相同。然而，在滑动过程中，粗糙度的位置和层数会显著影响薄膜的形状。特别是，当存在壁面滑移时，薄膜的轮廓随时间变化。较少

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