Temporal observation of running-in at rolling-sliding contact

Abstract

In rolling-sliding contact surfaces of mechanical elements such as gears and rolling bearings, surface fatigue and wear may occur due to high contact pressure, friction and repeated load. Although many research results have been reported to suppress them, there are few studies that elucidate detailed surface failure process because it is difficult to directly observe the contact interface. In this study, we developed a four-disk friction tester that enables temporal observation of surface changes in order to investigate the of surface failure mechanism at rolling-sliding contact surfaces. The marked features of the developed friction tester are follows; firstly, the size of test specimen is too small to be nondestructively placed inside many analyzing devices; secondly, the test specimen can be easily attached and removed. We conducted rolling-sliding test using this friction tester and confirmed the continuous change of the contact surfaces by interrupting the test and observing the specimen several times. From these tests, it is found that micropitting occurred and progressed with repeated contact, but the location of occurrence and size of pit changed with the running-in of the surface. It was also confirmed that the area where the micropitchings were densely generated was worn away.