This paper describes the development of a novel test rig to study mechanisms of surface failures and lives of constant velocity universal joints, CVJs, which are used in drive lines of automobiles. In order to simulate the rolling contact with slip and spin between a ball and inner and outer races of a CVJ, the test rig employed a crank mechanism that allowed a ball to make reciprocal linear and rotational motion relative to upper and lower specimens. Preliminary tests with greases showed that, by changing the test conditions, the rig was able to simulate various failure modes that occur in CVJs. They included the flaking by surface-initiated cracks, the flaking caused by sub-surface initiated cracks with structural changes including white etching areas, and the wear without flaking. Details of the failure processes were examined by the observation of track surfaces and cross sections. The results confirmed that the crack propagation depended on the driver-follower relationship between the specimens.

We carried out wear tests with material combination of a hard-drawn copper contact wire and an iron-based sintered alloy contact strip by changing the apparent contact area with four steps to clarify the influence of the apparent contact area on wear properties under electric current flowing condition. And we focused on a film resistance such as an oxide film and a wear particle on the contact wire surface, and considered the relationship between wear depth and wear mode transition phenomena. Based on wear properties obtained from wear test results and microscopic observations, we clarify the phenomena that the wear mode which maximizes the wear rate of contact wire will be changed depending on the apparent contact area, and that the wear depth determined by the apparent contact area and the load is an important parameter for melting of contact wire. Finally, the possibility of suppressing the maximum wear of contact wire is suggested by decreasing the film resistance of contact wire with changing the apparent contact area.