Wheel Tread Wear And Its Influence On Dynamic Performance Of Vehicles

Wheel wear is a common problem in railway transportation. Wheel wear causes change of wheel profile in the lateral and circumferential directions of wheel tread, and thus may cause great change in the wheel-rail contact relationship, which may lead to the degrade of dynamic response of vehicles. A survey found that the form of the wheel wear varies from conditions of both track and vehicle. It is also found that the form of wheel wear have direct influence on the safety, stability, and cost of the operation of high speed trains. The wheel wear has become one of the major problems in the high-speed railways, and therefore, become a hot spot of research in the major railway transportation nations. The main work of this thesis includes:(1) Monitoring of wheel wear of trains operating on a high-speed railway. The results indicate that hollow wear of the wheel tread is the main wear style on the monitored high-speed vehicles. All wheels are worn to different levels. Some of the vehicles were found to have wheel deflected wear that leans to the same side of the vehicles.(2) The vehicle system dynamic model of the monitored trains was built. The detrimental effects of hollow-wear and other wear styles on the vehicle dynamic performance were simulated. The strategy of wheel reprofiling was discussed. The results show that negative equivalent conicity occurs on the condition of wheel deflected wear, which leads to the equilibrium position of wheelset offsets from the middle of the track, which in return accelerates the deflected wear. There are several wheel/rail equilibrium positions on the hollow-worn wheel tread profile. Thus, the wheel/rail contact point jumps from one equilibrium position to another, when the vehicle is running at a high speed, leading to a "flange to flange" vibration, which can affect the vehicle dynamic behavior. The present of deflected wear on the hollow-worn wheels makes the influence of the "flange to flange" vibration on the vehicle dynamic behavior more complex. On the same bogie, if the wear of two wheel sets is deflected to one side, the deflected wear has greater influence than that is deflected on different sides. The vehicle dynamic behavior with different wheel wear styles was analyzed and advices on wheel re-profiling were given.(3) A three-dimensional wheel-rail contact model was established based on the spline fitted profile of the measured tread profile. It is found that there is a two-point contact between the wheel and rail because of the hollow wear, resulting in smaller contact area and extremely high contact stress, which may cause plastic deformation on the wheel and rail.(4) Monitoring of wheel polygonalization was conducted on high-speed trains. The main orders of polygonalization were identified and the results was used in the vehicle system dynamic model to discuss the detrimental effects of wheel polygonalization on the vehicle dynamic performance.