Definition - What does Fatigue mean?
The weakening of material due to frequent motion or constantly applied loads is referred to as Fatigue. It is the damage that occurs when an object is subjected to continuous stress over a prolonged duration. When loading and unloading of a material occurs repeatedly, Fatigue occurs. It is understood by the materials technologists that fatigue is the process in which brittle cracking of structure occurs due to the cyclic stresses applied by the object or material.
Petropedia explains Fatigue
Fatigue is the damage that occurs due to the continuous efforts or loads applied to a material. If the loads applied are above a certain limit, small cracks begin to form on the surface. Due to the repeatedly applied loads, the cracks eventually reach to a critical size resulting in the fracture of the structure. The fracture is fragile and it may take some time for it to increase in size and that depends on both the intensity and frequency of the stress cycles. Thus, Fatigue in rock formations is very common.
Fatigue life is the number of stress cycles a material undergoes before any failure of a specified nature takes place. The shape of the structure affects the Fatigue life; as stress is raised on the sharp corners or the square holes leading to Fatigue cracks and the Fatigue strength grows at the round holes or the fillets. There are three methods that the engineers use to determine the Fatigue life, i.e., stress-life method, strain-life method and linear-elastic fracture mechanisms.