Study On Influence Of Out-of-Round Railway Wheels On Wheel/Rail Interaction Force

With the development of high-speed railway, out-of-round wheel become more common, due to the stiff contact property between wheel and rail, geometric defects on a wheel tread can intensify wheel/rail interaction, causing severe repeated high-frequency impact loads, and can have a detrimental influence on both track and vehicle components, which influence the train running quality, safety and cost of transportation.In order to investigate dynamic wheel/rail interaction resulted from out-of-round wheels, a vehicle-track coupled dynamic model was established for numerical simulation first. This thesis describes the characteristics of unroundness of wheel tread profile and classifies out-of-round wheels. By means of vehicle-track system dynamic simulation model, this thesis systematically studies the influence on dynamic response of wheel/rail impact vibration due to flat wheels, local non-circular wheels, wheel polygonalization. The variations of impact vibrations with the train running speeds are given out. The numerical results show that wheel flat would result in considerable fluctuation of vertical wheel/rail contact loads and the vertical impact contact load results from the old wheel flat increases as the speed increases, and is much larger than that caused by the new wheel flat under the high-speed situation. So it is reasonable to take the old wheel flat model as the model which is used to calculate the limit value of a wheel flat. The local non-circular wheel would lead to the periodic vertical dynamic load and it will increase with the increase of the speed and flat depth, and the wheel flat depth will contribute more to the change of vertical impact load than speed. The wheel-rail vertical forces cause by wheel polygonalization become greater as the increase of wave depth, harmonic orders and running speed, the harmonic orders cause negligible influence on vehicle stability, but lead to severe vibration to the wheel and bogie.Furthermore, according to the data from the wheel polygonalization tracking test in the Beijing Shanghai line and combine the existing railway standards, the suggested limit value of out-of-round wheel is calculated. when the vehicle speed is over 250km/h and 200km/h, the corresponding length of wheel flat should be under 30mm and 35mm; when the wavelength of the local non-circular is 500mm, the vehicle speed is over 250km/h,300km/h and 350km/h, the corresponding wavelength depth must be under 0.95mm,0.8mm and 0.7mm; when the vehicle speed is over 250km/h the wave depth of 1,3,6 and 11 order should be under 1.5mm,0.5mm,0.2mm and 0.1mm; If the wheel out-of-roundness wave depth of the wheel is out of this limit, more attention should be paid to it.