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Locomotive wheel polygonisation due to discrete irregularities: simulation and mechanism

Discrete irregularities are a common issue occurring on locomotive wheels. The wheel roughness measured in the field sites indicates that some wheels suffer from discrete wheel irregularities, such as wheel flats or local defect. Meanwhile, the wheels exhibit obvious polygonisation. A wheel wear model is present to study the influence of discrete wheel irregularities on locomotive wheel polygonisation, which consists of a flexible-rigid locomotive-track coupled dynamics model and a wear calculation model based on the frictional work of wheel–rail contact patch. A series of discrete irregularities with different wavelengths are taken as initial input of irregularities. The wheel–rail interaction and wheel polygonisation evolution process induced by discrete wheel irregularities are analysed. The simulation results indicate that discrete wheel irregularities can excite the structural elastic vibration of the wheelset, especially the wheel lateral vibration, which leads to oscillations of the lateral creepage and creep force in a certain frequency. Wheel polygonisation is formed finally resulting from the fluctuation of wheel–rail creepages and creep forces. The frequency-fixing mechanism of wheel polygonisation with wavelengths of 630 and 200 mm in 1/3 octave band are the coupling of parameter excitation of discrete sleeper support with P2 resonance and lower bending resonance of the wheelset, respectively.