Squats
Definition
Flat-bottomed depressions in the rail running surface accompanied by internal crack systems, another manifestation of rolling contact fatigue caused by wheel slip and high contact stresses on the rail head crown.
- Appearance
- Flat-bottomed depressions in the rail surface
- Associated feature
- Internal crack systems
- Cause
- Rolling contact fatigue
- Contributing factors
- Wheel slip and high contact stress on the rail head crown
Common questions
How do squats differ from ordinary surface wear on a rail?+
Surface wear removes material gradually and evenly, while a squat develops from subsurface cracking that grows toward the surface, producing a localised depression with an internal crack network that wear alone would not create.
Why do squats matter in a rail failure investigation?+
The internal cracks associated with squats can propagate into a transverse rail fracture, so identifying them early is part of assessing whether a rail failure resulted from a pre-existing, detectable defect.
Related terms
- Gauge-Corner Cracking
- A specific RCF pattern where cracks initiate at the gauge corner of the rail head, the edge most heavily loaded by wheel...
- Press-Fit Fretting
- Relative micro-motion between a wheel or disc pressed onto an axle at its interference fit, generating fretting fatigue damage and pits that...
- RAIB
- Rail Accident Investigation Branch: the independent UK body that investigates railway accidents with the objective of improving safety, operating under the same...
- Rolling Contact Fatigue (RCF)
- Surface and subsurface fatigue damage caused by cyclic wheel-rail contact stress. Micro-cracks initiate at the rail surface, typically in the gauge-corner region,...
- Track Geometry Measurement
- Systematic recording of gauge, cross-level, twist, alignment, and surface profile along a route using dedicated measurement vehicles, producing a continuously updated map...