Bearing Inner Ring Axial Cracks

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Bearing inner ring axial cracks.Photo courtesy RBB Engineering © 2014.

Definition: Axial cracks that typically occur on the inner ring of a bearing.

Identification: Length wise cracks that occur along the roller path of a bearing inner ring. Etched micrographs of the bearing section often reveal irregular white etch areas. The phenomenon is sometimes referred to as “white etch cracking”.

Discussion: Axial crack failure due to irregular white etch areas have occurred in many applications, but have become pervasive in wind turbine gearboxes over the past five years. Some wind turbine gearbox types have seen failure rates of up to 40% within the first two years of operation.

Prevention: Use case carburized bearings with the appropriate amount of retained austenite. Keep bearing misalignment within good design practice limits. Ensure that roller profiles are appropriate for the application. Ensure that bearing inner ring interference fit is within good design practice limits to minimize hoop stress. The publishers of this site have special expertise with this failure mode. Please see the article on How to Prevent Axial Crack Bearing Failures in our resources section.

More Information: For more information on axial cracks, please submit a question to our “Ask an Expert” link. For assistance with a gearbox failure analysis, please visit our “Consulting” page.