| With the rapid development of urban transportation construction in China,the subway has brought convenient and fast transportation to people’s lives.At the same time,the environmental vibration problems caused by it have become increasingly serious,which has attracted extensive attention from all walks of life.The steel spring floating slab track is recognized as the best track structure with the best vibration reduction effect at present.It has a good vibration reduction effect in a wide range of frequency.However,the existing literature studies show that the vibration amplification phenomenon of floating slab track in the fundamental frequency still needs to be solved.In this paper,quasi-zero stiffness(QZS)structure and magnetorheological(MR)damper are introduced into the traditional steel spring floating slab track from two aspects of non-linear stiffness and damping,which provides a valuable way to improve the vibration reduction performance of the steel spring floating slab track at low frequencies.Firstly,based on the traditional steel-spring floating slab track structure,the basic type of QZS floating slab track is designed.Through the force analysis of the single-degree-of-freedom model,the influence of the parameters of QZS structure on the dynamic characteristics of the system is determined.At the same time,the dynamic performance of the MR damper was tested.According to the test results,the parameters of the dynamic model selected in this paper are fitted.Then the damping performance of the QZS and the MR damper were verified by combining the single-degree-of-freedom theory.Finally,the vertical coupling dynamic model of the vehicle-floating slab track with the QZS and the MR damper is established.The influence of key parameters of the QZS and the MR damper on wheel-rail safety and track damping performance is analyzed by simulation.The main research results and conclusions are as follows:(1)In this paper,a QZS floating slab track structure is designed with classical transverse spring as negative stiffness element.Based on this structure type,the influence of transverse spring parameters on the mechanical properties of the structure and the force transfer rate of the system is analyzed.When the displacement range of the structure is fixed,the bearing capacity and dynamic stiffness of quasi-zero stiffness structure are mainly affected by the horizontal length ratio and stiffness ratio of the transverse spring.Single adjustment of horizontal length and stiffness of lateral spring can change the dynamic stiffness of the structure at the equilibrium position,but excessive value of horizontal length or stiffness will result in negative dynamic stiffness of the system at the equilibrium position,which will lead to the jump frequency of the amplitude-frequency characteristic curve of the system and will have a negative impact on the vibration isolation performance of the system.In the single-degree-of-freedom system,by comparing the force transfer rate of the quasi-zero-stiffness steel-spring floating slab track structure with that of the traditional steel-spring floating slab track,it is found that the quasi-zero-stiffness structure can expand the vibration isolation range of the system and gradually reduce the force transfer rate of the system,but the reduction of dynamic stiffness will increase the response amplitude of the system.(2)By analyzing the test results of MR damper,it is found that the external current can adjust the output of MR damper.Based on the experimental results,a modified Dahl dynamic model is used to fit the parameters,and a better fitting result is obtained.By analyzing the force transfer rate of the single-degree-of-freedom model of MR damped floating slab track,it is found that the output of MR damper only affects the magnitude of the force transfer rate of the system,and does not change the natural frequency of the structure.Moreover,the magnification of high-frequency vibration caused by viscous damper can be effectively suppressed by semi-active control method.Combining magnetorheological damper with quasi-zero stiffness structure can reduce the natural frequency and force transfer rate of the system.(3)Considering the safety of wheel and rail and the vibration reduction of track,the simulation results of random vibration of wheel-rail coupling system are analyzed.It is suggested that the maximum output of MR damper be regulated by semi-active control strategy.For the steel spring floating slab track required for general vibration reduction,in order to improve the vibration reduction effect of the track structure at the fundamental frequency effectively,it is suggested that the maximum output of MR damper should be controlled at about 1/10 of the time domain amplitude of dynamic wheel-rail force.At the same time,according to the calculation results of the improved bang-bang control method adopted in this paper,in order to prevent the phenomenon of high frequency amplification of fulcrum reaction caused by excessive output of MR damper,it is suggested that the maximum output control displacement threshold of MR damper be 2 mm.(4)According to the analysis results of the non-linear dynamic characteristics of the quasi-zero stiffness floating slab track model and the simulation calculation,it is found that the vertical displacement of the track structure increases gradually with the decrease of the dynamic stiffness of the equilibrium position.When designing quasi-zero stiffness steel spring floating slab track structure,the space size of floating slab track structure should be fully considered,and the horizontal length ratio and stiffness ratio of quasi-zero stiffness structure should be reasonably matched.The dynamic stiffness of quasi-zero stiffness structure at equilibrium position is reduced as much as possible.On the basis of ensuring driving safety,the natural frequency of the system is reduced and the vibration reduction performance of the floating slab track is improved. |
PDF Full Text Request