Effect of Transient Loads on Premature Bearing Failures in Wind Turbine Drivetrain

Harpal Singh¹, Haifeng Qin², Benjamin Gould, Aaron Greco², Gary Doll³

¹Sentient Science Corporation, Buffalo, NY

² Argonne National Laboratory, Energy Systems Division, Lemont, IL

³Timken Engineered Surface Laboratories, University of Akron, Akron, OH

Abstract

Rapid and severe impact loading of the rollers on the bearing raceway can cause stress-induced white etch cracking (WEC), significantly shortening the life of bearings and gearboxes. It is believed that load reversals lead to severe plastic deformation, when this deformation exceeds a certain threshold it leads to the formation of WECs.  To test the hypothesis, we have designed a test rig to replicate the transient loading conditions experienced by wind turbine bearings. NU 306 cylindrical roller bearings were used as test specimens which were impacted by sudden loads while rotating at 1725 rpm. The tests were conducted in PAO ISO 10 oil. Microstructural analysis performed on tested samples revealed multiple cracks oriented in random directions. White etch areas were also observed adjacent to few cracks. Results revealed that transient loading leads to localized plastic deformation creating discrete locations of strain which leads to the formation of cracks.