Study On Wheel Profile Design Method For High-Speed Train

The wheel/rail profile optimization has always been a focus of railway research. Optimized profiles can increase the quality of the running trains and reduce the related maintenance costs. Deteriorated or mismatched profiles greatly influence the wear and other damages of both wheels and rails, and even drop the vehicle behavior.. Obviously, a wheel-rail profile design, developed on the basis of observations of wheel tread problems, can reduce the frequency of wheel re-profiling, and further the operational cost of the railway.Chapter1of this thesis reviews the history and the present situation of the research into wheel profile optimization. Chapter2introduces the methods employed in this thesis to solve the wheel/rail matching performance parameters, the wheel/rail interaction and vehicle system dynamics. In order to create a reference for wheel profile design, the advantages and disadvantages of the wheel profiles of Chinese high-speed trains are also explained.Excessive wheel/rail contact stress is the root cause of wheel damages. Therefore, to reduce wheel/rail contact stress is one of the main objectives of the profile optimization. Chapter3develops a forward solution method for designing wheel profile based on the wheel/rail normal gap, the main objective of which is to reduce the wheel/rail contact stress. The improved sequential quadratic programming method is used to solve the optimization model. The results of the numerical analysis show that wheel/rail force stress of the new profile is largely reduced without sacrificing the dynamic performance of the wheelset.For the high-speed vehicles with low axle load, however, the riding quality and running stability of the vehicle is more important objective than the wheel/rail contact stress. Because of the differences between the Chinese high-speed railway system and those in other countries, the wheel profiles behaved well at abroad may not be used directly in China, and modifications or further improvements are normally necessary. The traditional method can fully consider the advantages and disadvantages of the old profiles, so that the obtained results can easily be extended. In chapter4, the wheel profile of vehicle is designed by the traditional method. Two design proposals with small wheel/rail clearance are achieved to meet vehicle running requirement at the speed of350km/h～380km/h.In comparison with the traditional method, the inverse method has some features such as high production efficiency and low design cost. In chapter5, the wheel/rail contact geometry relationship was derived in detail, the wheel profile inverse design method is developed based on the RRD function, and the parallel algorithm which has high efficiency and good convergence is developed. The RRD function is adjusted based on the measured wheel profile and the new wheel profile is obtained using this method.Currently, the vast majority of wheel profile design methods only focuse on the matching performance and dynamic behavior in the beginning stage, and are usually separated from the vehicle dynamics. However, a successful wheel profile should ensure the high dynamic performance of the vehicle, ideally in the whole re-profiling period. Chapter6developed a new wheel profile design method on the basis of the methods introduced in the previous chapters, which is named as "average-fine design method".With this method the wheel profile is optimized with the consideration of contact stress, dynamic performance of the vehicle, wear of wheel tread and so on. For validation, a new profile was designed using this method based on the measured wheel profiles and its sound effects were proved in vehicle operation.Chapter7introduces the wear state of wheels in different lines and analyzes the effect of hollow-worn wheel on vehicle stability in detail. Take CRH3as an example, a wheel profile was designed using the average-fine design method and the performances of the new profile are investigated in detail and compared with the original wheel. The results show that the new profile has the better performances and can alleviate the hollow wear on the wheel, thus, the period of re-profiling can effectively be extended.Finally, the conclusions and prospect of the wheel profile design method are given.