Fatique Failure
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Stress Ratio - Fatique Failure

Metal fatigue is caused by repeated cycling of of the load. It is a progressive localized damage due to fluctuating stresses and strains on the material. Metal fatigue cracks initiate and propagate in regions where the strain is most severe.


The process of fatigue consists of three stages:

• Initial crack initiation
• Progressive crack growth across the part
• Final sudden fracture of the remaining cross section
• Schematic of S-N Curve, showing increase in fatigue life with decreasing stresses.