Effects of Axial Clearance on Surface Initiated Flaking in Tapered Roller Bearings

The calculating method for fatigue life of rolling bearings is based on the theory of Lundberg and Palmgren. The rated life is determined from the ratio of the dynamic load rating of the bearing to the dynamic equivalent load. However, in actual applications, flaking damage may occur earlier than this rated life. For example, surface initiated flaking may occur due to contamination in the lubricant. In addition, differences in the internal clearance of bearings are also thought to influence the occurrence of surface initiated flaking. This study aims to investigate the effect of different internal clearance on surface initiated flaking in tapered roller bearings. Firstly, rotating tests were conducted on combination tapered roller bearings with dented raceways under several axial clearances different from the standard condition. Secondly, the surface profiles of the bearings before and after the tests were compared to investigate the relationship between the distribution of flaking area and the axial clearance. Furthermore, the effect of axial clearance on the surface initiated flaking life was clarified from the comparison between the results of the rotating tests. Finally, the theoretical and experimental lives were compared. As a result, it has been found that when the axial clearance is excessively large, the distribution of flaking is biased toward the large diameter side of the outer raceway. In addition, it has been demonstrated that the bearing life is substantially affected by the axial clearance, and that the bearing life shortens as the axial clearance increases.