What is fatigue failure?
Short answer
flowchart LR
A[Repeated/fluctuating stress] --> B[Stress raiser]
B --> C[Crack initiation]
C --> D[Crack propagation\nbeach marks]
D --> E[Final fracture]
- Definition: Fracture under repeated or fluctuating stress below static strength
- Mechanism: Crack initiates at stress raiser, grows each cycle, final fracture
- Characteristic: Beach marks on fracture surface
- Common locations: Shafts, crankshafts, welded structures
- Mitigation: Good fillets, surface finish, avoid stress raisers
- Class requirement: IACS Rec 106 fatigue strength assessment, UR S7 longitudinal strength
- SMS requirement: Planned maintenance to detect stress raisers and monitor cyclic loading
- SE role: Inspect cyclic-loaded components, monitor, report cracks to Chief Engineer
Full answer
The full answer explains each point step by step, with the regulations and figures behind it and the discussion from other candidates. It is in the MEO Class II section of the Marine One forum, open to members enrolled for the MEO Class II exam.