4/19/2002, Wednesday Three Stages Fatigue Fracture

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4/19/2002, Wednesday Three Stages Fatigue
Fracture
Chapter 12, 13
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Stage I
Crack Nucleation
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Development of Surface Roughness
Ductile metal surface under cyclic loading
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Stage II
Micrfocrack Development
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Fatigue Crack Growth in Ductile Metals
Plastic blunting and re-sharpening in fully
reversed fatigue
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Fatigue Striations
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Advancing Fatigue Crack
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Stage III
Catastrophic Failure
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Fatigue-Crack Growth Rate
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Stress Intensity Factor Range
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Strong material are desired for high-cycle fatigue
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At low DK value, fatigue striation are not evident