Out-of-Round Railway Wheels - Causes and Consequences

An Investigation Including Field Tests, Out-of-Roundness Measurements and Numerical Simulations

Abstract: Causes and consequences of out-of-round railway wheels are investigated through literature studies, full-scale field experiments, out-of-roundness measurements, and numerical simulations. Both defects around the complete wheel circumference (e.g. polygonal wheels with wavelengths up to one wheel circumference) and local defects (e.g. wheel flats) are studied.

Wheel tread irregularities occurring in different types of train traffic in Sweden (high-speed, passenger, freight, commuter, subway) have been assessed using out-of-roundness measurements. These measurements show that high roughness levels with wavelengths between 3 cm and 8 cm (corrugation) are present on tread braked freight wheels and tread braked powered X2 high-speed train wheels. A previously known polygonalization of C20 subway wheels has been quantified.

The influence of different types of wheel out-of-roundness on the vertical dynamic wheel-rail contact force and on the track response is investigated through extensive field tests and numerical simulations. Measured responses are used to calibrate and validate numerical models for simulation of train-track interaction in the time domain.

An existing multibody system model for simulation of general three-dimensional train-track interaction is extended to include rolling contact mechanics according to the FASTSIM model and wear according to the Archard model, and also general wheel and rail profiles. The numerical model employs an iteration scheme with simulation of dynamic train-track interaction in the time domain coupled to a model of long-term wear. The extended model is used to study wheel polygonalization on subway wheels and rail corrugation growth due to (corrugated or round) powered high-speed train wheelsets. Some polygonalization wavelength-fixing mechanisms depending on the track properties have been discovered. The influence of corrugated wheels on rail corrugation growth is found to be negligible.

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