Beach Marks
Definition
Macroscopic curved bands on a fatigue fracture surface, visible without magnification, produced by changes in crack growth rate during service (load changes, shutdowns, overloads). Each band marks where the crack front was at a specific point in service history.
- Visibility
- Macroscopic (naked eye)
- Fracture type
- Fatigue fracture
- What they show
- Position of crack front over time during cyclic loading
Common questions
What are beach marks and why do they appear on fractures?+
Beach marks are curved lines that show up on a fatigue fracture surface. They form because the fatigue crack grows in stages, and each band marks where the crack front was at a moment during the loading history. Think of them like a record of the crack's journey.
Can you see beach marks without a microscope?+
Yes. Beach marks are macroscopic, which means they are visible to the naked eye. That sets them apart from striations, which need magnification. You can spot beach marks by looking at the fracture surface directly.
What causes variations in beach mark patterns?+
Changes in load, service shutdowns, and overloads all affect how fast the crack grows. When the growth rate changes, a new band forms. This makes beach marks useful for reading the service history of a failed part.
Related terms
- Fatigue Striations
- Microscopic parallel marks on a fatigue fracture surface, formed during individual loading cycles in Stage II crack growth. Visible by SEM at...
- Damage-Tolerant Design
- A structural-design philosophy that assumes cracks will form and specifies inspection intervals short enough to detect and repair cracks before they reach...
- Ductile Dimples
- Microscopic cup-shaped depressions visible on a ductile overload fracture surface under SEM, formed by nucleation, growth, and coalescence of microvoids at second-phase...
- Fatigue Fracture
- Fracture resulting from repeated cyclic loading, typically at stresses below the static yield strength. The fracture surface has characteristic markings (beach marks,...
- Fractography
- The systematic examination and interpretation of fracture surfaces to determine the mechanism, origin, and propagation direction of fracture; uses optical and scanning...
- MCAS
- Maneuvering Characteristics Augmentation System; the Boeing 737 MAX software feature that repeatedly commanded nose-down stabiliser trim based on a single AoA sensor...
- 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...
- Progressive Collapse
- A failure mode in which local structural failure triggers a sequence of failures in adjacent members, resulting in collapse disproportionate to the...
- Ratchet Marks
- Radial steps or ridges on a fatigue fracture surface separating adjacent regions that initiated from separate sites. They run from the component...
- River Patterns
- Fan-shaped or river-delta-like markings on brittle-cleavage fracture surfaces that indicate crack propagation direction; rivers diverge from the origin and converge toward the...
- S-N Curve
- A plot of cyclic stress amplitude (S) against the number of cycles to failure (N), used to characterise a material's fatigue life;...
- Safe-Life Design
- A structural-design philosophy where a component is retired from service before its predicted fatigue life is consumed; does not require crack detection...
Explained in these topics
- Fatigue Fracture: Beach Marks and StriationsMacroscopic curved bands on a fatigue fracture surface, visible without magnification, produced by changes in crack growth rate during service (load changes, s...
- Forensic Engineering: Failure Analysis and FractographyMacroscopic curved lines visible on a fatigue fracture surface, each recording the position of the fatigue crack front at a point in time during cyclic loading...