Correct option is B
Fatigue is a phenomenon where the resistance of a material to withstand stress decreases due to the repeated application of fluctuating or cyclic stresses over time. This can lead to failure at stress levels significantly lower than the material's ultimate tensile strength.
When a material is subjected to repeated cycles of loading and unloading, microscopic cracks may form at areas of stress concentration. These cracks gradually grow with each cycle of stress until the material fails completely. The number of cycles a material can withstand before failure occurs depends on the magnitude of the applied stress and the material properties.
Fatigue failure is common in engineering components subjected to fluctuating loads, such as bridges, aircraft wings, and rotating machinery. The resistance of a material to fatigue is an important consideration in the design of components that experience cyclical loading, as failure due to fatigue can occur without any significant plastic deformation, making it particularly dangerous.
