Research On Wheel Polygonization Of High-speed Train

As the China high-speed railway lines constantly increase, wheel polygonization phenomena are recently detected on wheel treads along the circumferential direction after running a certain mileage. Wheel out-of-roundness(OOR) can aggravate wheel-rail interaction, causing severe repeated high-frequency impact loads, and can have a detrimental influence on both track and vehicle components, worsening passenger riding comfort. Thus, the wheel OOR problems cause railway departments and research institutes pay more and more attention.Currently, the study of wheel OOR are mainly focused on the1st to5th order of wheel OOR by domestic and foreign scholars, while the20th order OOR has already been detected by field measurement.In addition, wheel OOR have been one of difficult problem in wheel-rail interaction, As the formation mechanism of wheel OOR are very complex, there is no clear explanation at present. Therefore, it is essential to conduct comprehensive research on wheel OOR.First, To study the influence of the1st to25th order of wheel OOR on the dynamic performance of high-speed trains, using harmonic function define wheel polygonization, vehicle-track dynamics simulation model is established. Then, Based on the existing research results from railway, car and machining, the formation mechanism of wheel OOR of high-speed train are investigated and analyzed. In the end, considering wheel OOR, influence of parameter variations of vehicle and track on the dynamic performance are study.Previously analyzing the formation mechanism of wheel OOR, it is generally acknowledged that polygonal number is approximately equivalent to the ratio of wheel-rail excitation frequency to the rotational frequency of wheel, namely the value is integer. In this paper, a new idea is put forward: when the ratio occurs remainder, wheel OOR can also be generated. Furthermore, in case the ratio is integer, which means the formation of N orders of wheel OOR need wheel roll only one circle, otherwise, it need several circles. Thus, the20th order of wheel OOR could be formed by wheel rolling one circle, three circles or seven circles, the corresponding excitation frequencies are616Hz,205.3Hz and88Hz respectively at the speed of300km/h.The effect of track spectrum excitation is not taken into account in the process of simulation. Results show: for6th order of wheel OOR to25th order of wheel OOR, especially for10th or higher orders of wheel OOR, the wheel-rail vertical forces become greater as the increase of wave depth, harmonic orders and running speed, while it dosen’t increase with the speed for1st to5th order of wheel OOR. Also, the influence of higher orders of wheel OOR on wheel-rail lateral forces can’t be neglected, but the lower orders of wheel OOR have little influence. The wheel OOR also has little influence on the carbody ride index and derailment coefficient. Whereas, the critical speed decrease as the harmonic orders and wave depth increase, which is449km/h for normal round wheel and408km/h for25th order of wheel OOR,the critical speed decreased by9.1%, higher orders of wheel OOR have more impact and can’t be ignored. Finally, according to the permission value170kN of wheel-rail vertical forces, the wave depth limits for10th to25th high harmonic order of wheel polygonization at the speed of200,250,300,350km/h are determined, which could be referred as a reference for ensuring the running safety of high-speed trains.