Accelerated natural fault diagnosis in slow speed bearings with Acoustic Emission

Rolling element bearings are the most common cause of rotating machinery failure. Over the past 20 years, Acoustic Emission (AE) technology has evolved as a significant opportunity to monitor and diagnose the mechanical integrity of rolling element bearings. This paper presents results of an investigation to assess the potential of the Acoustic Emission (AE) technology for detecting and locating natural defects in rolling element bearings. To undertake this task a special purpose test-rig was built that allowed for accelerated natural degradation of a bearing race. It is concluded that sub-surface initiation and subsequent crack propagation can be detected using a range of data analysis techniques on AE's generated from natural degrading bearings. The paper also investigates the source characterisation of AE signals associated with a defective bearing whilst in operation. This study also attempted to identify the size of a natural defect on bearings using AE technology. In conclusion, the results from this investigation show that whilst measurements on operational bearings cannot be achieved as described in this paper, the method of identifying the onset of crack propagation can be employed as a quality control tool for bearing manufacturers particularly for testing bearing material homogeneity.