Ratchet marks
Definition
Radial steps or ridges on a fatigue fracture surface separating adjacent regions that initiated from separate sites. They run from the component surface into the fracture and indicate multi-site initiation or high stress amplitude.
Related terms
- Beach marks
- Macroscopic curved bands on a fatigue fracture surface, visible without magnification, produced by changes in crack growth rate during service (load changes,...
- Fatigue fracture
- Fracture resulting from repeated cyclic loading, typically at stresses below the static yield strength. The fracture surface has characteristic markings (beach marks,...
- Fatigue striations
- Microscopic parallel marks on a fatigue fracture surface, formed during individual loading cycles in Stage II crack growth. Visible by SEM at...
- Multi-site damage (MSD)
- The simultaneous presence of fatigue cracks at multiple adjacent fastener holes or structural features, characteristic of ageing aircraft fuselage and other riveted...
- Stress intensity range (ΔK)
- The difference between the maximum and minimum stress intensity factor in one loading cycle, ΔK = K_max - K_min. The Paris law...
Explained in
- Fatigue Fracture: Beach Marks and StriationsRadial steps or ridges on a fatigue fracture surface separating adjacent regions that initiated from separate sites. They run from the component surface into t...