1. 4/19/2002, Wednesday Three Stages Fatigue Fracture
Chapter 12, 13

2. Stage I
Crack Nucleation

3. Development of Surface Roughness
Ductile metal surface
under cyclic loading

4. Stage II
Micrfocrack Development

5. Fatigue Crack Growth in Ductile Metals
Plastic blunting and re-sharpening in fully reversed fatigue

6. Fatigue Striations

7. Advancing Fatigue Crack

8. Stage III
Catastrophic Failure

9. Fatigue-Crack Growth Rate

10. Stress Intensity Factor Range

11. Strong material are desired for high-cycle fatigue

12. At low DK value, fatigue striation are not evident