Relation between the Limit of Hydrodynamic Lubrication and Micro Cavitation caused by Sruface Roughness

本研究的目的是了解由表面粗糙度引起的空化对流体动力润滑到边界润滑过渡区附近流体动力作用的影响。本文用带有粗糙表面的滑块在转鼓上作枢轴转动，观察了空泡的产生条件，并研究了空泡对润滑性能的影响，结果表明：（1）在粗糙表面的全膜润滑区，由表面粗糙度引起的空泡是存在的，而在相对光滑的表面，则是存在的。直到两个表面彼此接触才观察到空腔。(2)动压润滑区的空穴产生于轴承后部压力较低的区域。(3)当滑块与滚筒接触时，在滑块中心附近产生空穴并向下游扩展。(4)在流体动力润滑条件下，微腔的产生对摩擦系数的影响不大。其次，为了研究表面粗糙度对油膜破裂的影响，以及油膜破裂方式对轴承性能的影响，采用粗糙表面透明滑块在滚动体上的实验装置，对油膜破裂进行了观察，结果如下：（5）在流体动力润滑条件下，粗糙表面和光滑表面的油膜破裂区域不同。(6)在流体动力润滑条件下，表面粗糙度对摩擦力的影响与油膜破裂方式的变化相一致。

The purpose of this reserch is to understand the effect of cavitation caused by surface roughness on the hydrodynamical action near the transition region from hydrodynamic lubrication to boundary lubrication. The observations of the cavities has been made with a pivoted slider having rough surface on a drum and the condition of the cavitation generation and the effect of the cavitation on the lubrication performance were investigated.The results are shown as follows: (1) The cavities caused by surface roughness were observed in the full film lubricating area for the rough surface but for comparative smooth surface. the cavity was not observed untill two surfaces touched each other. (2) The cavities in the hydrodynamic lubricating area were generated in the backward area of the bearing where the pressure is low. (3) The cavity was generated in the vicinity of the slider center and spreaded to the down stream when the slider touched the rolling drum. (4) The generation of micro cavity did not exert a great effect on the friction coefficient under hydrodynamic lubrication.Next, to investigate the way of change in the film rupture due to surface roughness and the effect of the film rupture pattern on the bearing performance an apparatus of a transparent slider with rough surface on a roller was employed and the film rupture was observed.The results are shown as follows: (5) The difference between rough surface and smooth surface was found in the area of the film rupture under the hydrodynmic lubrication. (6) The friction force was infuenced by surface roughness in accordance with the change in film rupture pattern under the hydrodynamic lubrication.