Press-Fit Fretting
Definition
Relative micro-motion between a wheel or disc pressed onto an axle at its interference fit, generating fretting fatigue damage and pits that act as stress concentrations for crack initiation.
- Mechanism
- Micro-motion at an interference fit
- Typical location
- Wheel or disc pressed onto an axle
- Damage type
- Fretting fatigue, generates pits
- Consequence
- Pits act as crack-initiation stress concentrations
Common questions
Why does a press-fit joint fret even though it is designed to be rigid?+
A press fit is never perfectly immobile under service loads; cyclic bending, vibration, and load transfer through the joint cause tiny relative slip between the mating surfaces, and it is this repeated micro-slip, not gross movement, that generates fretting damage over time.
How does an investigator confirm press-fit fretting as a failure origin?+
Fractographic examination of the axle or disc surface at the interference-fit boundary typically shows characteristic fretting scars, oxide debris, and fatigue striations radiating from a pit at that location, distinguishing it from fatigue origins elsewhere on the component such as a surface defect or corrosion pit.
Related terms
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- 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,...
- Squats
- Flat-bottomed depressions in the rail running surface accompanied by internal crack systems, another manifestation of rolling contact fatigue caused by wheel slip...
- 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...