Dabin Cui

Optimal design of wheel profiles for high-speed trains

The high maintenance cost of high-speed wheels due to wear and rolling contact fatigue is a major problem in the commercial operation of high-speed trains in China. In order to understand the wear behavior of high-speed wheels and its influence on the motion stability of high-speed trains, the worn profiles and the work-hardening of the wheels of the CRH3 high-speed trains that operate on the Wuhan–Guangzhou line were monitored in different periods during service; in particular, the influence of hollow wear of the wheel on the lateral acceleration of the bearing-box was investigated in detail. A new wheel profile design method was suggested to reduce the hollow wear by seeking an optimization match of the wheel profiles, the vehicle’s suspension systems, and the wear behavior of wheels in service. The feasibility of the method was verified by numerical simulation using the operation conditions of CRH3 high-speed trains on the Wuhan–Guangzhou line. A new wheel profile was designed using this method. The wheel/rail contact performance and the vehicle’s dynamic behavior resulting from the designed new wheel were investigated in detail and compared with those of the original wheel. The wear behavior of the designed new wheel profile was predicted based on wear data measured on the original wheel. The results show that compared with the original wheel profile, the designed new wheel profile can improve the wheel/rail contact state, reduce the contact stress level, and lower the friction power of wheel and rail. The extent of hollow wear on the new wheel is significantly decreased and the vehicle has improved dynamic behavior when wheelsets with the designed new profile are used. Thus, the period before re-profiling is required can be effectively extended.

Influence of Vehicle Parameters on Critical Hunting Speed Based on Ruzicka Model

While introducing foreign advanced technology and cooperating with Chinese famous research institutes, the high-speed vehicles are designed and take the major task of passenger transport in China. In high-speed vehicle, the characteristic of shock absorber is an important parameter which determines overall behavior of the vehicle. The most existing researches neglect the influence of the series stiffness of the shock absorber on the vehicle dynamic behavior and have one-sided views on the equivalent conicity of wheel tread. In this paper, a high speed passenger vehicle in China is modeled to investigate the effect of the parameters taking series hydraulic shock absorber stiffness into consideration on Ruzicka model. Using the vehicle dynamic model, the effect of main suspension parameters on critical speed is studied. In order to verify the reasonableness of shock absorber parameter settings, vibration isolation characteristics are calculated and the relationship between suspension parameters and the vehicle critical hunting speed is studied. To study the influence of equivalent conicity on vehicle dynamic behavior, a series of wheel treads with different conicities are set and the vehicle critical hunting speeds with different wheel treads are calculated. The discipline between the equivalent conicity of wheel tread and critical speed are obtained in vehicle nonlinear system. The research results show that the critical speed of vehicle much depends on wheelset positioning stiffness and anti-hunting motion damper, and the series stiffness produces notable effect on the vehicle dynamic behavior. The critical speed has a peak value with the equivalent conicity increasing, which is different from the traditional opinion in which the critical speed will decrease with the conicity increasing. The relationship between critical speed and conicity of wheel tread is effected by the suspension parameters of the vehicle. The study results obtained offer a method and useful data to designing the parameters of the high speed vehicle and simulation study.

Effect of the turning characteristics of underfloor wheel lathes on the evolution of wheel polygonisation

During both running and wheel cut operations, wheels of railway vehicles and the friction rollers that support and drive the wheelset on a typical wheel cut lathe are subject to wear and hence are likely to develop out-of-round characteristics after sustained use. The resulting out-of-round wheels can significantly affect the ride quality and can potentially increase the incidence of fatigue-related component failures due to the resulting higher intensity loading cycles. Furthermore, the corresponding out-of-round characteristics of the lathes friction rollers will continue to degrade the subsequent cut quality of wheels. For the analysis of the out-of-round characteristics caused by an underfloor wheel lathe used for the high-speed trains in China, a mathematical model based on a typical electric multiple unit (EMU) vehicles wheelsets and their interactions with the wheel lathe friction rollers was established. Factors influencing the cut quality of the wheels, including the number of cuts, eccentricity forms of the friction rollers and the longitudinal spacing of the two rollers, have been analysed. The results show that two cuts can effectively remove the higher order polygon on the wheel surface. The eccentricity and phase angle of the friction rollers have no influence on the cut quality of higher order polygons, whereas they are the primary cause for the fourth-order polygons. The severity of the fourth-order polygon depends on the level and the phase of the eccentricity of the friction rollers. The space of the two rollers can also significantly affect the cut quality. Obtaining the theoretical and practical value for the maintenance of polygonised wheels using the underfloor lathe is the main outcome of this study.