Exam Question

### Introduction to Metal Fatigue
Metal fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic or fluctuating stresses. The nominal maximum stress values are significantly less than the ultimate tensile strength (UTS) and often below the yield strength of the material. Failure occurs after a specific number of stress cycles and is characterized by a brittle-like fracture surface, even in ductile materials.
The process of fatigue failure can be broken down into three distinct stages as cited in the reference material:
1. **Stage I: Crack Initiation:** After a number of cycles, micro-cracks initiate on the surface of the component. These cracks are extremely small and typically form at points of high stress concentration, such as notches, sharp corners, or material defects.