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Railway rails accumulate severe plastic deformation at the surface as a result of loading by passing wheels. This process of plastic strain accumulation is plastic ratcheting. Ratcheting failure occurs when material accumulates a critical strain and failed material produces wear debris and rolling contact fatigue cracks. A computer model of strain accumulation, ratcheting failure and wear has been...
The tractive force transmitted through the contact of rail and wheel is often lower than the limiting friction force and such contacts are not fully slipping. The distribution of traction is no longer proportional to the distribution of normal pressure in the contact patch. The distribution of stress in the rail, and therefore also the shakedown limit and the ratchetting wear rate, is affected as...
Rolling contact fatigue (RCF) is currently one of the principal limitations of railway infrastructure productivity. Head checks in particular are prevalent in curves and switches where flange contact at the gauge corner results in increased slip and decreased wheel–rail contact area. These surface-initiated cracks can lead to complete failure of the rail and potentially derailment. The focus of the...
A ductile material subjected to repeated rolling contact can accumulate very high levels of shear strain near the surface. At some point the material loses its integrity and fails, and this failure is manifested in the form of wear (the material detaching from the surface and producing debris) or rolling contact fatigue (initiation of micro-cracks which may subsequently propagate and branch). Models...
Surface textures of very small scale are able to carry pockets of lubricant into heavily loaded contacts, leading to reductions in friction and wear. Recently, such textures have been produced by a new method in which two materials of differing wear properties are combined to form a composite surface. In a typical application, a distribution of individual wear resistant islands of small dimension...
A mechanism of metallic wear is proposed in which laminar wear debris is generated by a process of plastic ratchetting brought about by repeated pummelling of the softer wearing surface by the asperities on a harder mating surface. Wear rate is found to be approximately proportional to (load) and an increasing function of a single non-dimensional parameter termed the plasticity index for repeated...
The wear properties of diamond-like carbon films deposited on single-crystal silicon using an r.f. plasma enhanced chemical vapour deposition process are analysed as a function of deposition conditions. It is found that the tribological properties of the film are highly dependant on the d.c. self-bias voltage developed between the r.f. driven electrode and the plasma during deposition. The films were...
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