Rim and Web Cracks

Rim crack in gear. Photo courtesy GEARTECH © 2014.

Definition: Gear rim and web cracks develop in the rim or web of the gear body.

Identification: Rim and web cracks start in the rim or web of the gear body, often near stress concentrating features. They progress radially through the gear, usually exiting the gear body in a tooth root fillet.

Discussion: Gear rim and web cracks may be caused by a rim that is too thin, a stress concentration, or a resonance of the gear body.

Prevention: Make the gear rim thickness greater than 2 times the whole tooth depth. Avoid gear blank resonance conditions. Minimize the presence of stress concentrations.

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