[109] Early detection of white etching crack formation under dynamic loading using an electrostatic sensing technique

K Esmaeili1, L Wang1, T J Harvey1, N M White2 and W Holweger1,3
1nCATS, Faculty of Engineering and Physical Sciences, University of Southampton, UK

2Electronics and Computer Science, Faculty of Engineering and Physical Sciences, University of Southampton, UK

3Basics Tribology, Schaeffler Technologies GmbH & Ko KG, Herzogenaurach, Germany  

White etching cracks (WECs) are networks of cracks formed in rolling element bearings that can cause a failure within 1-20% of the bearing’s expected L10 life. Due to the subsurface nature of these cracks, early detection of WECs in bearings has been very challenging.
A previous study conducted by the authors of this paper showed that the electrostatic sensing techniques have the potential to detect WECs under the influence of electrical current. In this study, WECs were created on a test-bench with cylindrical roller bearings of type NU222, under dynamic loading and without the application of electrical current to the bearing, while two electrostatic sensors were positioned close to the two test bearings in the test-rig to monitor the bearing conditions.
The results from the tests show that both electrostatic sensors detected bearing failures due to WEC formation by showing an increase well before the spall occurred in the bearings. Post-test metallographic analysis has shown that the final bearing damage was caused by WECs formed in the subsurface of the bearing race. Detailed analysis of the electrostatic sensor signals will reveal whether there are charge-discharging events during the WEC tests without applying electrical current to the bearings.