Fatighetsegenskaper

Fatighetsegenskaper refers to the behavior of materials under repeated or cyclic loading. Unlike static strength, which describes a material's resistance to failure under a constant load, fatigue is the progressive and localized structural damage that occurs when a material is subjected to stresses that fluctuate over time. Even stresses well below the material's yield strength can cause fatigue failure if applied repeatedly.

The process of fatigue typically involves three stages: crack initiation, crack propagation, and final fracture. Crack initiation often begins at stress concentrations, such as surface imperfections, sharp corners, or internal defects. Once a crack forms, it grows incrementally with each load cycle. The rate of crack growth depends on the material properties, the magnitude and range of the applied stress, and the environment. Eventually, the crack becomes large enough that the remaining cross-section of the material can no longer support the applied load, leading to rapid and often brittle fracture.

Fatigue life is a critical design parameter, representing the number of load cycles a component can withstand before failure. Factors influencing fatigue life include the stress amplitude, mean stress, stress ratio, material microstructure, surface finish, and the presence of environmental factors like corrosion. Understanding and predicting fatigue behavior is essential in the design of structures and components subjected to dynamic loads, such as aircraft, bridges, vehicles, and rotating machinery. Fatigue testing is commonly employed to determine the fatigue properties of materials and to validate designs.