Researchers Achieve Breakthrough in Solving Leading Cause of Gearbox Failures

May 11, 2016

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Accomplishing a significant milestone, researchers from the U.S. Department of Energy’s Argonne National Laboratory have successfully replicated the leading cause of wind turbine gearbox failures, known as white-etch cracks or axial cracks. This represents a big step forward in solving a problem that has plagued the wind industry for years.

“These results provide us with critical information to determine what causes these cracks and inform testing approaches that will allow us to understand how to actually prevent them from occurring,” said Dr. Aaron Greco, principal materials scientist, Argonne National Laboratory. “Solving the white-etch crack issue in gearboxes would significantly improve turbine reliability and reduce overall wind plant maintenance costs.” 

White-etch cracks are thought to be caused by aspects of turbine operation, such as transient loading, electrical currents, and lubricant contamination. Argonne researchers determined that certain levels of these operating parameters lead to the formation of white-etch cracks, therefore establishing an energy threshold beyond which white-etch cracks are predicted to form.

Microscopic image of white-etch cracks
Argonne is working with the support of the Energy Department and several industrial partners, including SKF Group and Afton Chemical, to identify the conditions leading to white-etch cracks and how to improve bearing reliability.

“Our goal in collaborating with Argonne National Laboratory is to design a standardized test that will evaluate the ability of current wind turbine lubricants to protect against white-etch cracks,” said Dr. Marc Ingram, R&D engineering specialist, Afton Chemical Ltd. “This work is leading the way for both understanding the white-etch crack phenomenon and developing solutions to this problem, in which lubricants can play a part.”   

Argonne is also partnering with NREL to gain insight on the conditions bearings experience in a wind turbine during events such as variable winds, grid faults, and emergency stops. This is being done by instrumenting the high-speed shaft of the gearbox in the Energy Department’s 1.5-megawatt wind turbine located at the National Wind Technology Center to measure actual loads, electrical currents, and other conditions during the turbine operation.

For its part, Argonne is focused at the material level, characterizing the failed bearings and performing benchtop testing to replicate the white-etch cracks in a controlled environment and to transfer these findings from the labs to the relevant industrial original equipment manufacturers. For more information, read the publication.