Väsymislujuutta

Väsymislujuutta, also known as fatigue strength or endurance limit in English, refers to the stress level below which a material can withstand repeated cyclic loading indefinitely without failing. This phenomenon is crucial in engineering design, especially for components subjected to dynamic or oscillating forces. Unlike tensile strength, which measures resistance to a single pulling force, fatigue strength addresses the cumulative damage caused by repeated stress cycles.

When a material is subjected to cyclic loading, even if the maximum stress is below its yield strength, microscopic cracks can initiate and propagate over time. Eventually, these cracks reach a critical size, leading to sudden and often catastrophic failure. The fatigue strength of a material is determined through experimental testing, typically involving applying a series of precisely controlled stress cycles and observing the number of cycles to failure at different stress amplitudes.

Factors such as the material's composition, microstructure, surface finish, and the presence of defects significantly influence its fatigue strength. Surface treatments like polishing or shot peening can improve fatigue resistance by introducing compressive stresses on the surface. Understanding and accounting for väsymislujuutta is essential for ensuring the long-term reliability and safety of structures and mechanical parts in various applications, from aircraft wings to bridges and automotive components.