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In materials science, fatigue is the initiation and propagation of cracks in a material due to cyclic loading. Once a fatigue crack has initiated, it grows a small amount with each loading cycle, typically producing striations on some parts of the fracture surface.
However, in corrosion fatigue crack nucleation is facilitated by corrosion; typically, about 10 percent of life is sufficient for this stage. The rest (90 percent) of life is spent in crack propagation. Thus, it is more useful to evaluate crack-propagation behavior during corrosion fatigue. Fracture mechanics uses pre-cracked specimens ...
Scanning electron microscope image of fatigue striations produced from constant amplitude loading. The crack is growing from left to right. Striations are marks produced on the fracture surface that show the incremental growth of a fatigue crack. A striation marks the position of the crack tip at the time it was made.
Different types of crack growth (e.g. fatigue, stress corrosion cracking, hydrogen embrittlement) produce characteristic features on the surface, which can be used to help identify the failure mode. The overall pattern of cracking can be more important than a single crack, however, especially in the case of brittle materials like ceramics and ...
Fatigue performances in polymers caused by cyclical loading usually go through two stages: crack initiation/nucleation and crack growth. Hence, a lot of researcher design experiments to study the fatigue behaviors of polymers according to these two phases, especially for rubber fatigue.
A crack growth equation is used for calculating the size of a fatigue crack growing from cyclic loads. The growth of a fatigue crack can result in catastrophic failure, particularly in the case of aircraft. When many growing fatigue cracks interact with one another it is known as widespread fatigue damage. A crack growth equation can be used to ...
Paris' law (also known as the Paris–Erdogan equation) is a crack growth equation that gives the rate of growth of a fatigue crack. The stress intensity factor K {\displaystyle K} characterises the load around a crack tip and the rate of crack growth is experimentally shown to be a function of the range of stress intensity Δ K {\displaystyle ...
Crack closure is a phenomenon in fatigue loading, where the opposing faces of a crack remain in contact even with an external load acting on the material. As the load is increased, a critical value will be reached at which time the crack becomes open .