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

本研究的目的是了解表面粗糙度引起的空化对流体动力润滑向边界润滑过渡区域附近流体动力作用的影响。利用转鼓上具有粗糙表面的枢轴滑块对空穴进行了观察，研究了空化产生的条件和空化对润滑性能的影响。结果表明：(1)粗糙表面的空穴主要分布在全膜润滑区，而相对光滑的表面则是由表面粗糙引起的空穴。直到两个表面相互接触，才能观察到空洞。(2)动压润滑区的气穴产生于压力较低的轴承后部。(3)当滑块接触滚筒时，空穴在滑块中心附近产生，并扩展到下游。(4)在动压润滑条件下，微孔的产生对摩擦系数的影响不大。其次，为了研究表面粗糙度引起的油膜断裂的变化方式以及油膜断裂方式对轴承性能的影响，利用滚子上带有粗糙表面的透明滑块对油膜断裂进行了观察。结果表明：(5)在动压润滑条件下，油膜断裂的区域存在粗糙表面和光滑表面的差异。(6)摩擦力受表面粗糙度的影响，与流体动力润滑下膜破裂形态的变化相一致。

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.