Fatigue Failure Analysis of a Grease-Lubricated Roller Bearing from an Electric Motor

The grease-lubricated roller bearing of an electric motor that drove a supply blower suddenly failed during operation. In order to identify the causes of the failure, a variety of characterizations were carried out. The failed surfaces of the bearing were observed visually and microscopically, and the characteristics of the lubricating grease were also investigated. Results showed that the surface of the inner ring of the bearing contained contact fatigue damage, and was covered with a multitude of debris and contact fatigue pits. What’s more, the lubricating grease was subjected to severe thermally induced degradation due to high service temperature, which consequently resulted in the decrease of the lubricating capacity of the grease. Thus, the lubricant film in the roller/raceway contacts was not formed effectively and the lubrication of the roller bearing was poor. As a result, serious local wear as well as contact fatigue damage were brought about on the roller and raceway and the wear finally led to the failure of the bearing.