Wheelrail

Wheelrail refers to the interface between a railway wheel and the rail on which it runs. This contact is central to rail vehicle dynamics, affecting ride quality, safety, wear, energy efficiency, and noise. The wheel typically has a conical tread and a flange, while the rail presents a rounded top surface. Under load, the contact region is small and shifts with changes in speed, cant (superelevation), axle load, and steering of the wheelset.

The interaction is commonly analyzed as a rolling contact problem. Basic models use Hertzian contact theory to estimate contact pressures and patch size, but real surfaces exhibit roughness, plastic deformation, and lubrication effects that influence friction, adhesion, and wear. Friction at the wheel-rail interface controls traction for acceleration and braking, as well as resistance to sliding in curves. Wheel-rail behavior also affects steering stability and the occurrence of slip or skid under varying weather and surface conditions.

Wear and degradation are ongoing concerns. Tread wear gradually shapes the wheel profile, while rail heads wear to adjust contact geometry. Rolling contact fatigue can produce surface defects on rails and wheels, including surface checks, corrugation, or localized wheel flats. Maintenance aims to manage these effects by reprofiling and grinding wheels, reprofiling rails, and applying lubrication or friction modifiers where appropriate. Regular inspection helps detect defects early and prevent service disruption.

Advances in wheelrail engineering include optimized wheel profiles for lower wear and noise, improved rail grinding techniques, and monitoring systems that track temperature, vibration, and wear to guide maintenance planning.