| beach marks | a visible feature of fatigue with three regions:
1) initiation site
2) propagation where beach marks are found perpendicular to applied stress with light and dark areas indicating varying concentration of oxidation during cyclic loading. here, thousands of striation marks can be found
3) final fracture region due to ductile overload by exceeding yield strength or fracture toughness |
| cleavage fracture | (by exceeding K_1c)
in steel:
- found in temps below the transition temp (TT)
- small amounts of plastic deformation (brittle)
- low toughness |
| hydrogen-assisted cracking | - intergranular crack boundary
- fine bright lines (crows feet)
- hemispherical voids (fisheyes)
- yawning grain boundaries |
| intergranular stress corrosion cracking | idk |
| microvoid coalescence | (by exceeding yield)
occurs when voids form around tiny inclusions in the steel as it stretches open during yielding
in steel:
- found in temps above the transition temp (TT)
- large amounts of plastic deformation (ductile)
- high toughness |
| striations | - a microscopic feature of fatigue
- traces of individual cycles before failure |
| transgranular stress corrosion cracking | idk |
