Fault severity trending in rolling element in bearings

Fatigue-induced fault propagation is the most common cause of failure in rolling element bearings. As most classic diagnostic indicators do not trend monotonically with wear development, the ability to assess fault severity remains limited at present. This paper aims to expand current understanding and establish a correlation between the vibration signal and the actual extent of fault propagation. To achieve this, an extensive test program was undertaken using a laboratory test rig fitted with bearings initially seeded with small faults on the inner race. Vibration data from the rig was collected and analysed systematically at regular time intervals. Concurrently, the defect size and raceway topography were examined using laser scanning microscopy. The results from both sources were then combined to provide valuable insight into the effectiveness of common vibration indicators for fault trending. Through a detailed comparison of these indicators, a method of tracking fault severity is suggested which will aid greatly in the prognostics of rolling element bearings.