Study On Wheel-rail Dynamic Characteristics In Rail Corrugation Section Of Metro

With the development of urban rail transit,rail corrugation has attracted wide attention.Rail corrugation occurs frequently in metro lines and causes great harm,which exacerbate vibration and noise of wheel-rail system,abbreviate the service life of vehicles and track components,affect the comfort of passengers,and even endanger the transportation security.Rail corrugation is closely related to the dynamic characteristics of wheel-rail system,which is a difficult and hot issue that has not been completely solved for wheel-rail system.Based on the comprehensive analysis of the research status of rail corrugation and wheel-rail dynamics at home and abroad,this paper studied on wheel-rail dynamic characteristics in rail corrugation section of metro by the method of field measurement and numerical analysis.The safety threshold values of rail corrugation and the optimization of track line parameters were proposed for the prevention and treatment of rail corrugation.The main research work and results of this article are as follows:(1)The rail surface irregularities in the typical corrugation section of the general monolithic track were measured on site,and the existing rail corrugation evaluation indexes were summarized.According to this analysis,the rail corrugation mainly occurs on the inner rail in the curve section with a small radius,and the characteristic wavelength was mainly200-250 mm,followed by 40 mm,the maximum wave depth about 0.8mm,which exceeded the existing rail corrugation evaluation standard.The short-pitch corrugation appears in the straight section with the main wavelength of 40 mm and the maximum wave depth of 0.1mm,which is slighter than that in the curve section.(2)The vibration characteristics and vibration transmission law of the track and tunnel structures in the corrugation section of the small radius curve were measured.The measured results showed that the vibration of the track and tunnel structures are too large due to the rail corrugation,and the main frequency of the vibration is consistent with the passing frequency of the corrugation.The high frequency vibration of 400 Hz excited by the short-pitch corrugation is more intense.The transmission of vibration gradually decays from rail to track bed and then to tunnel wall.The attenuation of high frequency vibration energy by earth makes the vibration frequency of 80 Hz become the main frequency of ground vibration.(3)Based on vehicle-track coupling dynamics theory,a vehicle-track coupling dynamics model considering flexible track was established by using multi-body system dynamics method and finite element method.The rail corrugation excitation of wheel-rail system was obtained by field measurement,or the displacement input function used to simulate the corrugation to control the wavelength and wave depth characteristic variables.The correctness and accuracy of the model established in this paper were verified by comparing the model calculation results with the existing literature and measurement results.(4)Based on the vehicle-track coupling system dynamics model,the influence of different rail corrugation on the dynamic characteristics of wheel-rail system was analyzed,and the safety threshold of wave depth for guiding the corrugated rail grinding was proposed.The results showed that the rail corrugation deteriorates the wheel-rail interaction.The wheel-rail vertical force fluctuates periodically with the wavelength of corrugation,which in one period the impact vibration of wheel-rail system reaches the peak value at 1/4 wavelength.The influence of rail corrugation on the wheel-rail dynamic response decreases with wavelength and increases with wave depth.The short-pitch corrugation leads to high-frequency vibration of wheel-rail system,and the driving safety index is more likely to exceed the limit.The corrugation safety thresholds for rail grinding in the existing regulations are applicable to long-wavelength corrugation,but for the short-pitch corrugation with wavelengths of 30,40,50 and 60 mm the safety threshold values of wave depth are recommended to be 0.08,0.11,0.12 and 0.21 mm respectively at the vehicle speed of 80km/h.(5)For the rail corrugation issue in small radius curve section,the influences of curve radius,vehicle speed,wheel-rail friction coefficient and other parameters on wheel-rail dynamic characteristics and rail corrugation were analyzed.Based on the control of rail corrugation,the optimization suggestions of relevant influencing factors were given.The results showed that too small curve radius is the main reason for frequent rail corrugation.The actual vehicle speed in the small radius curve section can be slightly larger than the design speed,so that the curve in an appropriate deficient superelevation state,which can not only control the wheel-rail wear and rail corrugation,but also ensure the traffic safety and stability.As the friction coefficient increases,the wheel-rail wear increases,and the rail corrugation is more likely to occur.If the friction coefficient is too small,the wear between wheel and rail will also increase,and affect the traction and braking performance of the train.It is suggested that the proper lubrication between wheel and rail should be maintained.(6)For the rail corrugation issue in the straight section of damper fastener,the influence of fastener vertical stiffness and damping on wheel-rail dynamic characteristics and rail corrugation were analyzed.The results showed that the fastener stiffness mainly affects the damping performance of track structure.The fastener damping mainly affects the attenuation of vibration energy of track system,which is closely related to the development of rail corrugation.In order to control the rail corrugation and ensure the vibration reduction effect,it is suggested that the damper fastener should maintain smaller stiffness and try to select larger damping.