Fatigue failure in a bearing typically begins with what visible defect?

Fatigue failure in a bearing is characterized by a process where microscopic cracks develop due to the repeated stress cycles that the bearing experiences during operation. The correct choice, flaking, is associated with the deterioration of the surface layer of the bearing material. As these microscopic cracks propagate, they can lead to the detachment of small fragments of material from the bearing surface, which is observed as flaking. This visible defect is a clear sign of wear and the onset of fatigue, indicating that the bearing has experienced cyclic loading beyond its fatigue limit.

Flaking typically occurs after the initial stages of sub-surface crack formation, making it a more advanced indicator of fatigue compared to other defects. Proper monitoring and understanding of these failure modes are critical in maintaining the integrity of rotating machinery and ensuring operational reliability. This choice not only highlights the specific defect associated with fatigue failure but also emphasizes the need for early detection to prevent catastrophic bearing failures.