If spur gears are properly made and lubricated, they may still be subjected to which type of failure?

The correct answer is pitting, which is a type of surface fatigue failure that can occur in spur gears despite them being properly made and lubricated. Pitting is characterized by small pits or cavities that form on the gear teeth surfaces due to repeated stress cycles. This failure is often a result of high contact stresses as gears mesh and transmit loads.

In well-designed and lubricated spur gears, the lubrication helps reduce friction and wear, but the materials and loading conditions can still lead to pitting over time. Pitting occurs typically due to the cyclic nature of the loads that the gears experience, where localized stresses exceed the material's endurance limits, leading to small areas where the material fatigues and breaks away.

Understanding pitting is crucial in gear design and maintenance, as it can ultimately lead to gear failure if left unchecked. Regular inspections and monitoring are necessary to identify signs of pitting early, preventing larger issues in the gear operation.

The other types of failures, such as tooth spalling, typically involve larger pieces of material breaking off rather than the gradual loss seen in pitting. Tooth pending refers to issues related to alignment or mounting rather than the direct surface failure, and shearing would relate to more catastrophic failures of the teeth themselves under extreme loads,