The path of rolling elements in defective bearings: Observations, analysis and methods to estimate spall size

•Identify and disprove discrepancies in previous assumptions and theories in defective bearings.•Analysis of the effect of load and speed on the signature of the entry and exit vibration responses.•Propose a more accurate load dependant defect size estimation algorithm with greater accuracy.

This paper describes the experimental investigation of the vibration signature generated by rolling elements entering and exiting a notch defect in the outer raceway of a bearing. The vibration responses of the bearing housing and the displacement between the raceways were measured and analyzed. These key features can be used to estimate the size of the defect and is demonstrated in this paper for a range of shaft speeds and bearing loads. It is shown that existing defect size estimation methods include assumptions that describe the path of the rolling elements in the defect zone leading to poor estimates of defect size. A new defect size estimation method is proposed and is shown to be accurate for estimating a range of notch defect geometries over a range of shaft speeds and applied loads.