Materiaaliväsymys

Materiaaliväsymys, also known as fatigue, is a phenomenon where a material weakens over time due to repeated stress. This weakening can occur even if the applied stress is below the material's yield strength. The process involves the initiation and gradual propagation of cracks within the material. These cracks start at microscopic flaws or stress concentration points and grow incrementally with each load cycle. Eventually, when the accumulated crack growth reaches a critical size, the material can fail suddenly and catastrophically.

The rate at which fatigue damage accumulates depends on several factors, including the magnitude and type of stress cycles, the material's properties, and the environmental conditions. Cyclic loading, where stress is applied and removed repeatedly, is the primary driver of fatigue. The frequency and waveform of these cycles also play a role. Materials with lower toughness and higher notch sensitivity are generally more susceptible to fatigue failure. Environmental factors like corrosion can accelerate fatigue crack growth, a process known as corrosion fatigue.

Understanding and predicting material fatigue is crucial in engineering design, especially for components subjected to dynamic loads, such as aircraft structures, bridges, and rotating machinery. Design methodologies often incorporate safety factors and fatigue life calculations to ensure that components can withstand the expected service loads for their intended lifespan. Techniques like crack detection and monitoring are employed in-service to identify potential fatigue damage before it leads to failure.