Plastic Deformation


Plastic deformation of gear teeth, with yielding in gear tooth fillets. Photo courtesy GEARTECH © 2014.

Definition: Plastic deformation occurs when a component is stressed beyond it’s yield strength, resulting in a permanently deformed shape, even after the load is removed.

Identification: Plastically deformed gear teeth can sometimes be identified by the presence of bent teeth and cracks in the tooth root fillets. Bent teeth are not always visible to the naked eye, and in some cases must be checked using a gear checking machine.

Discussion: Plastic deformation is very harmful to gear operation, as the location of the gear teeth has changed, which affects the load share amongst the gear teeth and can lead to tip-to-root interference.

Prevention: Plastic deformation due to overload can be prevented by reducing load magnitude, increasing gear material strength, or by changing gear geometry to increase load capacity.

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