Multi-site damage (MSD)
Definition
The simultaneous presence of fatigue cracks at multiple adjacent fastener holes or structural features, characteristic of ageing aircraft fuselage and other riveted structures. MSD leads to rapid link-up and catastrophic failure once one crack bridges the gap between neighbours.
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...
- Ratchet marks
- Radial steps or ridges on a fatigue fracture surface separating adjacent regions that initiated from separate sites. They run from the component...
- 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 StriationsThe simultaneous presence of fatigue cracks at multiple adjacent fastener holes or structural features, characteristic of ageing aircraft fuselage and other ri...