The Behavior of Indentation Marks in Rolling-Sliding Elastohydrodynamically Lubricated Contacts

Indentation marks in rolling-sliding contacts are known to increase the risk of failures in heavily loaded elastohydrodynamically lubricated contacts found in machine elements, like gears and rolling bearings. In this article, literature is discussed showing the different hypotheses available to explain the interaction of sliding with the indentation marks, in both gears and rolling bearings. With the use of semi-analytical simulations, it is shown that the failure mechanism and its initiation point may be influenced by different mechanisms, depending on the rolling-sliding magnitude and the lubrication conditions (high sliding is different from nearly pure rolling situations). One possible mechanism is the well-known stress concentration produced by the pressure ripple at the edges of the dent. The other mechanism (rarely mentioned in the literature) is a possible local film collapse (including wear) located at the leading edge of the dent in nearly pure rolling situations (bearings). The amount of sliding influences the pressure and clearance ripples. These ripples are made of two components, one traveling with the speed of the dented surface and the other traveling with the average speed of the lubricant. With large sliding, the failure may then be related to the location and condition when these two components superimpose. The theoretical results are qualitatively verified with the use of experiments carried out in-house.