Study On Design And Evaluation Method Of Rail Vibration Absorber Based On Phononic Crystal Theory

In recent years,the metro has developed rapidly in major cities in China,which has effectively alleviated the problems of urban population travel and traffic congestion.In this historical development process,many metro operation and maintenance problems are gradually exposed,which reduce the operation quality of metro,even threaten the driving safety and force the metro to operate at high cost.As far as the metro rail is concerned,the long-standing problem of rail corrugation has shown a spreading trend in the metro network with the sharp metro curve,which has occurred all over the country.After the occurrence of rail corrugation,it will significantly worsen the dynamics interaction between wheels and rails,cause medium and high frequency strong vibration,reduce the running stability and comfort of metro,but also cause secondary problems,such as vibration fatigue and high noise of vehicle and track key component,threaten the operation safety,and greatly increase the workload and cost of rail maintenance.Therefore,academia has carried out continuous research on rail corrugation treatment,and a large number of research results can be seen in the literature.In this thesis,the research on rail vibration absorber will be carried out from the perspective of reducing the vibration caused by rail corrugation,so as to provide reference for the treatment of rail corrugation.Firstly,this thesis briefly summarized the research status of rail corrugation treatment at home and abroad,including rail grinding and rail vibration absorber vibration reduction,points out their respective advantages and disadvantages,and also expounded the development process of phononic crystal theory and its application in the field of rail transit.On this basis,using the phononic crystal band gap theory,a design method of rail vibration absorber for P2 resonant rail corrugation of the sharp metro curve was proposed,and the specific design was abstracted and simplified into the "spring–damping–mass" model,which was introduced into the dynamics model of vehicle–track coupling system,and the vehicle–track coupling dynamics time–domain model considering rail vibration absorber was established,which evaluated the effective vibration reduction frequency band and effect of rail vibration absorber when the vehicle passed through the rail corrugation.Based on the sharp metro curve(R350 m),the dynamics response of vehicle–track system under rail corrugation excitation was analyzed,it was found that the model can effectively simulate the P2 resonance characteristics of the system.Using this model,the vertical dynamics response of wheel rail under the excitation of rail corrugation with wavelength of146–312 mm and wave depth of 0.04–0.4 mm was analyzed under the premise of P2 resonance frequency of 69 Hz and passing speed of 39–84 km/h.The results show that the vertical dynamics response of wheel set reaches the maximum at 69 Hz when the speed and rail corrugation wavelength change,indicating that the simulated rail corrugation is indeed related to P2 resonance,which can be used for further research on P2 resonance rail corrugation;compared with the condition without rail corrugation,the vertical dynamics response of wheel and rail under rail corrugation condition is significantly improved,and the response frequency is consistent with the passing frequency of corrugation;with the increase of rail corrugation depth,the dynamics response between wheel and rail intensifies,which is consistent with the actual situation and previous research conclusions.Taking the P2 resonant rail corrugation on the sharp metro curve of R350 m as an example,the passing frequency or P2 resonant frequency of vehicle–track system was set as the middle frequency of the band gap of the rail vibration absorber,using the phononic crystal local resonance theory and the phononic crystal structure design method,the rail vibration absorber which could suppress the system vibration under the excitation of rail corrugation and its optimal energy band structure diagram was obtained.In order to deal with rail corrugation with different passing frequencies,rail vibration absorbers corresponding to different band gap center frequencies were designed for the following research.In order to analyze the vibration reduction effect of rail vibration absorber in time–domain,using the equivalent modeling method,the designed rail vibration absorber was abstracted and simplified into the "spring–damping–mass" model,which was introduced into the vehicle–track coupling dynamics model,it was connected with the rail at the actual installation position,and the vehicle–track coupling dynamics model considering rail vibration absorber was established.By changing speed,wavelength,vibration absorber and other parameters and using the above vehicle–track coupling dynamics model,the effective vibration reduction frequency band and effect of different rail vibration absorbers were analyzed and evaluated.On the premise of no track spectrum excitation,the P2 resonance frequency or the center frequency of the band gap of the vibration absorber is set to 69 Hz,when the vehicle passes through the rail corrugation with the wavelength of 221 mm and the wave depth of 0.2 mm at the speed of39–84 km/h,it is found that the damping of the coating layer of the vibration absorber can broaden the effective vibration reduction frequency band and expand its application range,but will weaken the maximum vibration reduction effect.When the track spectrum is still ignored,the track and vibration absorber parameters are changed,and three P2 resonance frequencies and band gap center frequencies of 50,58 and 69 Hz are simulated,the vibration reduction effect of the vehicle passing through the rail corrugation of different wavelengths at the speed of 55 km/h is analyzed,and the wave depth remains unchanged at 0.2 mm,it is found that the optimal vibration reduction effect occurs near the band gap center frequency,which is consistent with the original design intention.When the center frequency of the band gap of the vibration absorber is 50,58 and 69 Hz respectively,the effective vibration reduction frequency bands are 41–65 Hz,52–73 Hz and 61–85 Hz respectively,and the maximum vibration reduction effect is 26%,27.7% and 24.4% respectively.The effective vibration reduction frequency band of the vibration absorber predicted by the time–domain evaluation method is slightly wider than and completely covers the band gap predicted by the phononic crystal theory,the vibration reduction effect shows an important nonlinearity with the change of the central frequency of the band gap.Taking the track spectrum into account,the vibration reduction effect of the vehicle passing through the rail corrugation with wave depth of 0.2 mm and different wavelengths at the speed of 55 km/h were analyzed for the three P2 resonance frequencies and band gap center frequencies of 50,58 and 69 Hz.Compared with the above conditions without track spectrum,it is found that the effective vibration reduction frequency band of the vibration absorber does not change,and the optimal vibration reduction effects under the central frequency of the three vibration absorbers are slightly reduced,which becomes 25%,24.25% and 22.67% in turn.Ultimately,the main work of the thesis is summarized and a prospect is made.