Study On Vibration Characteristics Of CWR Track Structure With Axial Temperature Force

The CWR is wildely used in the resonstruction of the existing railway and the high speed railway for it can reduce the number of rail joints greatly and improve the safety and comfort of train operation.What's more,it also can prolong the service life of components of the train and the track system.Due to the ballast resistance and rail fastening resistance,large temperature stress will exist in the long rail of CWR when the rail temperature changes which may results in the rail expansion or break-out.Therefore,how to detect the temperature stress inside the long rail quickly and accurately is an important research topic in the field of railway operation safety monitoring for the researchers around the world.In this paper,the vibration differential equation of periodic supporting rail under harmonic harmonic load is deduced according to the theory of Timoshenko beam.The relationship between the resonant frequency in the frequency range(0~5000Hz)and the axial temperature stress of the rail is analyzed by the wavenumber finite element method for periodical structure.At the same time,the influences of the support stiffness under the rail,sleeper spacing and the rail type on the resonant frequency are discussed.According to the research,the main conclusions are as follows:(1)There is a certain change relatiaonship between the axial temperature force and the resonance frequencies(including vertical and lateral)of the periodic discrete support rail.The resonant frequency of each order increases with the increases of the axial tensile force,and decreases with the increases of the axial temperature pressure force.Therefore,it is feasible to analyze the rail internal temperature force by detecting the change of rail resonant frequencies.(2)Among the resonant frequencies of the periodical discretely support rail,the higher the resonance frequency,the more obvious the influence of axial temperature force.While the temperature of the rail changes,the average change rate of the 3~5 order resonant frequency of the vertical vibration is 0.0978 Hz/?,0.1437 Hz/? and 0.2064 Hz/?,respectively.What's more,the average change of 3~5 resonant frequency of lateral vibration is 0.189Hz/?,0.0015/? and 0.2025/?,respectively.(3)Considering the influence of the stiffness of the rail pad and the ballast,the first,second and the fourth order resonant frequencies(both vertical and lateral vibration)of the periodic discretely support rail are influenced mostly.However,it has little influence on the third and fifth order resonant frequencies.The main reason is that the third and 5 resonance frequencies are first and second order pinned-pinned resonant frequencies of rail,respectively,and they are not influenced by the change of support stiffness under the rail.Therefore,combined with the conclusion(2),taking into account the resonant frequency in the high frequency range(above 3000Hz)is difficult to stimulate,the third resoant frequency of both verical and lateral vibration is more appropriate for detecting the axial temperature force in CWR.(4)By analyzing the influence of the change of sleeper spacing on the resonant frequencies of the periodic discretely support rail,the resonant frequency of each order decreases with the increases of the sleeper spacing.However,for the larger sleeper spacing,the resonant frequency of each order is more sensitive to the change of the temperature force.(5)The firstand and the second order resonant frequencies of the vertical vibration of the periodic discretely support rail decreases with the increase of the rail mark,and the 3~5 order resonance frequencies increase with the increases of the rail mark.Therefore,it is necessary to determin the sleeper spacing and rail type in advance by detecting the internal temperature force of CWR rails by vibration method.In summary,through the analysis the influence of the change of axial temperature force and support stiffness under the rail on the vertiacal and lateral vibration charateristics of the periodic discrete support rail,the third resonant vertical and lateral frequencies(1080Hz,570Hz)of periodic discretely support rail maybe the most suitable evaluation index for measuring the temperature force in CWR.In addition,through the analysis of influence of the track structure parameters on the vibration characteristics of the track structure,the first order and two order vertical resonant frequencies(79Hz,526Hz)may be used for evaluating whether the stiffness of the ballast and raila pad can meet the requirements.