What is the phenomenon of fatigue failure?

Fatigue failure specifically refers to the process where a material experiences a gradual loss of strength and eventual failure due to the application of cyclic loading. This means that when a material is subjected to repeated cycles of stress, even if each individual load is below the ultimate tensile strength of the material, microstructural changes can occur. These changes accumulate over time, leading to the development of cracks that eventually result in complete failure.

The nature of fatigue failure is critical in engineering design because it highlights the importance of considering not just the maximum loads that a material can withstand, but also the frequency and nature of loading conditions during its service life. This is particularly relevant in components that experience regular stress cycles, such as bridge beams, aircraft wings, and rotating shafts. Understanding fatigue failure helps engineers design safer and more reliable structures and components by selecting appropriate materials and designing for durability against such loading conditions.