Experimental Study on Water Lubrication Characteristics of Full-Flat Thrust Bearing with Partial Water-Repellent Surface

Abstract

In this study, a flat thrust bearing is developed by active exploiting the slip flow generated on a water-repellent surface. In order to produce a load, this bearing has a structure that generates a pressure flow by using the discontinuity of shear flow rate between a water-repellent surface and an untreated or a hydrophilic surface. This structure results in the completely flat bearing that has no geometrical variations in its surface. Friction tests were carried out with respect to the water-repellent thrust bearing that consists of three water-repellent parts and untreated or hydrophilic parts. The results verified that this partial water-repellent thrust bearing functioned well with a low and stable friction coefficient (less than 0.002). And lubrication surfaces had no damages at all because both surfaces are separated with fluid film which enables to avoid the solid contact. The friction coefficient became lower for the bearing having large difference of contact angle (thus, shear flow rate) between both parts. Furthermore, a friction coefficient for the bearing of which water-repellent part and hydrophilic part had same area was the lowest, and friction coefficient became larger than its value in case of not only wide water-repellent part but also narrow one. These results suggest a possibility that this thrust bearing operates by the same mechanism as a conventional bearing under fluid lubrication.