Fatigue provides what for Stress, Stress spectrum, Failure mechanism and crack propagation?

• A. Plastic, full-life, immediate
• B. Viscoelastic, dynamic, immediate
• C. Elastic, LL only, warning and slow
• D. Elastic, LL only, warning and fast

Answer: (C)

Fatigue damage arises from repeated loading, so the material’s response is essentially elastic over most of the cycle, with any plastic effects confined to small regions near cracks or flaws. Because damage accrues with cycles rather than a single overload, the crank is a gradual, progressive process rather than an immediate break. That means fatigue is described by an elastic stress response, a long-life (low-stress) regime, and crack growth that provides warning signs before final fracture. The cracks advance slowly, so you see gradual propagation rather than a sudden, catastrophic failure. This is why fatigue is characterized as elastic, in a long-life regime, with warning and slow crack growth.