| With the continuous expansion of high-speed railway network and the mass investment of EMU,the safety of train operation is becoming more and more important while bringing convenience and comfort to people.Timely maintenance work is the basic guarantee for railway development.High-speed railway in China has been operating for nearly ten years since Beijing-Tianji urban railway operated in 2008.The overall condition is good,and the railway infrastructure has stood the test of time.However,with the increase of operation time,some problems of high-speed railway are gradually exposed.Short-wave diseases in wheel/rail system include surface abrasion,spalling,rail corrugation,weld defects,contact noise,etc.The abnormal high-frequency vibration problem of high-speed track/vehicle system shortens the service life of track/vehicle components,and increases railway maintenance cost,which is also a potential hazard to traffic safety.The wheel/rail short-wave diseases are closely related to the unsteady characteristics of wheel/rail contact in high-speed running.Wheel/rail unsteady rolling contact,also known as transient wheel/rail contact,was first proposed by Kalker.He developed the corresponding exact theoretical solution program of CONTACT.However,because of its slow computation speed,it has not been widely used.And it is also unable to solve the problem that considering the wheel/rail short-wave defects and the geometric nonlinearity.Therefore,it is urgent to find a reliable method to deal with the wheel/rail transient rolling contact problem,and study the high-frequency transient response characteristics of high-speed railway track/vehicle system caused by wheel/rail short-wave diseases.It will provide theoretical evidence for exploring the development trend of the diseases and the prevention measures.In view of this,this paper takes the unsteady rolling contact of high-speed wheel/rail as the core,and aiming at the track short-wave diseases of high-speed railway,from the view of combining field test and theoretical analysis,the improved vertical high-frequency transient simulation model and multidirectional track/vehicle system are established respectively.It is used to study the dynamic response characteristics of track/vehicle system caused by single-point randomness and continuous periodic short-wave diseases.The formation and development mechanism of rail corrugation on high-speed railway is deeply studied.The research work is carried out and the innovative achievements achieved are summarized as follows.(1)Based on explicit finite element method,the transient 3D finite element simulation model of high-speed track/vehicle system is established.Taking wheel/rail real geometry and material nonlinearity into account,the high-frequency vertical simulation model of track/vehicle system is improved.The script interface is used to develop the parametric modeling of rail fastening system and the user subroutine is used to control the process of wheel/rail elastoplastic material.Pre-pressure is applied on vehicle suspension system to accelerate the track/vehicle system to enter the initial stable state,and shorten the overall duration of the dynamic simulation.(2)As the lateral degree needs to be considered when a train passes a curved track,a multi-directional transient finite element simulation model for track/vehicle system is proposed with considering the structure of vehicle system.The initial running speed of train is defined,and the wheelset vertical,lateral and longitudinal degrees of freedom and vehicle system suspension parameters are considered.Explicit finite element method is used to calculate the duration of the track/vehicle system entering the dynamic stable state under initial excitation.The simulation model is verified by the comparison with the measured wheel/rail force data on the corrugation section of curved track.(3)Aiming at high-speed track/vehicle system vibration caused by bad rail welding,the phenomenon of rail corrugation near individual bad welds,the relationship between the characteristics of track/vehicle system high-frequency dynamic response and the wheel/rail transient rolling state is studied by the vertical simulation model.From time and frequency domain,the effects of train speed and rail straightness on track/vehicle dynamic response are studied.The range of rail welding straightness requirement under different high-speed railway operating speed levels is proposed,and the formation reason of middle and long wavelength of rail corrugation near the weld is explored.(4)The high-frequency wheel/rail system vibration caused by continuous periodic short-wave diseases such as straight rail grinding marks and rail corrugation is discussed.Based on the track/vehicle system high-frequency vertical simulation model,the relationship between the characteristics of track/vehicle system high-frequency dynamic response and the wheel/rail transient rolling state is studied.The initial cause of corrugation at rail grinding marks is explored,and the development trend of rail corrugation is predicted with the train passing frequency and the traction ratio.(5)A multi-directional high-frequency simulation model for track/vehicle system is used,the dynamic response characteristics and the initial formation mechanism of curved rail corrugation are studied.Combined with wheelset frequency response and rail Pinned-Pinned vibration characteristics,the track/vehicle system transient response law of guide and non-guide wheel in rail corrugation section is compared.The formation mechanism of curved rail corrugation is also studied considering the super and the under superelevation high of curved track. |
PDF Full Text Request