Definition - What does Fatigue Fracture mean?
A fatigue fracture is a material failure that occurs as a result of excessive cyclic loading. Prior to final fatigue fracture, many different micro fractures are created and eventually the repeated dynamic loading propagates the cracks. When a fatigue fracture occurs depends largely on the type and shape of the material.
Corrosionpedia explains Fatigue Fracture
A fatigue fracture is caused when a stress is applied, then removed, then reapplied. This process can repeat millions of times before a fatigue fracture is significant enough to cause material failure. Every time the stress is reapplied, micro cracks on the surface of the material are allowed to grow. Once the growth of these micro cracks and the stress applied is sufficient, one or more of the cracks will propagate throughout the thickness of material; this ultimately results in material or component failure.
Fatigue fracture is determined by many variables. Material selection is very important. For example, aluminum has less fatigue resistance than a material such as steel. Also, materials with sharp corners fracture easier than materials that have rounded edges because the sharp corners act as stress concentrators that are nucleation points for the initial micro cracking. Another cause is the stress being cyclically applied. If the stress can be reduced either in magnitude or in multitude, then the risk of a fatigue fracture diminishes.