Condition Monitoring of Grease Lubricated Rolling Bearings by Acoustic Emission Measurements

The behaviour of grease lubrication of rolling bearings is less known than the behaviour of oil lubrication in the same type of tribological systems, although greases are the most common lubricants for rolling bearings. Problems connected with the lubrication of grease lubricated rolling bearings arise from starvation of the contact zone and contaminants in the lubricant. This thesis presents a new tool for predictive condition monitoring of grease lubricated rolling bearings. The tool consists of acoustic emission measurement technology, of guidelines for interpreting the AE measurement results and of an empirical model for prediction of the acoustic emission pulse count rate. Significant features of grease lubrication in rolling bearings are the starvation and the time dependence of the lubrication situation and the behaviour of the lubrication situation that does not follow the classical EHL theory for oil lubricated rolling bearings. The six papers presented in this thesis deal with mechanisms of grease lubrication and verification of the behaviour of grease lubrication in a real rolling bearing application. The conclusions regarding the