Influence Of Out-Of-Round Railway Wheel On Vehicle-Track System Dynamic Behaviour

Out-of-round wheel is a common imperfection form among railway vehicle wheels. Due to the stiff contact property between wheel and rail, geometric defects on a wheel tread can intensify wheel/rail interaction. Out-of-round wheels can cause detrimental effect on components of vehicle and track, however, they may pose a potential threat to operational safety. In order to ensure the operating safety, it is necessary to make the out-of-roundness condition under reasonable control. The formation and influence mechanism of out-of-round wheels has not been recognized adequately. Therefore, it is essential to conduct further relevant researches.In order to investigate vertical dynamic wheel/rail interaction resulted from out-of-round wheels; the wheel radial deviations from metro trains were measured and analyzed. A vehicle-track coupled dynamic model was established for numerical simulation. The results from polygonal metro wheels were employed as excitations of the dynamic model. The influence of actual polygonal wheels on dynamic wheel/rail interaction was analyzed in both time and frequency domain. Simulation results demonstrate that the polygonal wheel can result in considerable fluctuation of vertical wheel/rail contact loads. Derivatives of wheel radial deviations can reasonably reflect the dynamic property of wheel/rail contact force. The wheel/rail interaction can be classified into three categories according to excitation frequencies. Rail vibration plays a key role in the dynamic wheel/rail contact force. High-frequency oscillation induced by out-of-round wheels can be attenuated to a large extent though vehicle suspension systems. However, the short-wavelength components of the polygonal wheel can obviously intensify high-frequency vibration of rails. Polygonal wheels can lead to obvious wheel load reduction with higher operational speeds and lower axle loads. Lower stiffness railpads may alleviate dynamic wheel/rail interaction to some extent.To study the influence of out-of-round wheels on vehicle-track system dynamics at high speeds, detected results from German ICE high-speed polygonal wheels were employed as multi-harmonic excitation. Wheel/rail dynamics characteristics due to the periodic and non-periodic out-of-round wheels were compared. Due to the high-frequency wheel/rail Hertz contact, derivative of wheel radial deviations with respect to time is an effective indicator of the dynamic wheel/rail contact force. Dynamic wheel/rail contact force becomes more sensitive to higher order harmonics with increased speeds.