Fatigue in materials engineering is best described as?

• A. Permanent deformation under static load
• B. Progressive structural damage due to cyclic loading leading to failure
• C. Corrosion under stress
• D. Immediate fracture due to impact

Answer: (B)

Fatigue is the process where a material accumulates damage under repeated or fluctuating stresses, eventually leading to fracture. Tiny cracks tend to initiate at defects or surface irregularities and then grow with each load cycle, even when the peak stress is below the level that would cause immediate deformation or failure. After many cycles, the crack becomes large enough to carry the load and the part fails. This slow, cycle-based progression distinguishes fatigue from a single static overload, from corrosion-related cracking, or from an immediate impact fracture.