| Rail transit,with its advantages of safety,punctuality,comfort and large transportation capacity and so on,has become the first choice for citizens to travel.Due to the continually increasing axle load and speed,the interaction between vehicle and track is more and more intensive,thus the wheel-rail dynamic interaction become more and more complicated.To alleviate the wheel-rail dynamic interaction,and further reduce the low frequency vibration problem aroused by train operation,the dynamic characteristics and parameters optimization of metro vehicle-track system are studied by analytical model analysis,structural optimization,simulation calculation,model experiment and on-line testing.The parameters of the mass,stiffness and damping of the elastic element are optimized and combined to make the multiple units work in coordination with each other.The effect of absorbing vibration energy and reducing vibration transmission are realized,and the problem of low frequency vibration amplification is alleviated.Finally,the analytical model of theory and the results of dynamic parameter optimization are verified by using track model experiments in real size and the on-line testing method.The main contents and achievements of this paper are as follows:(1)From the point of view of structural dynamics,the track can seemed as an single mass-spring-damp model and the vibration control index are derived,then to analysis the fundamental principles of track vibration attenuation and isolated.Use measured date to study on the rugulation of track vibration attenuation in practical engineering application,and to verified the accuracy and reliability of the analytic model.(2)For dynamic analytical models of damping track,the analytical solutions of dynamic transfer coefficient and dynamic displacement transfer coefficient are formulated and derived.The changing rule and the working mechanism of dynamic characteristics of damping track are analyzed qualitatively by using MATHEMATICA software to carry out numerical calculation.(3)The parameter optimization method of three-layer elastic element track is studied based on the dynamics model of fastener/vibration absorbing plate/floating slab and the complex method of structural optimization design.The damping property of elastic elements brought into play makes many elastic elements working harmoniously with each other.The effects of absorbing vibration energy and reducing vibration transmission are realized,and the optimized vibration vibration absorbing plate can be used to suppress the vibration part of 20~40Hz effectively.The method of complex shape optimization is compared with the method of fixed point homology optimization,and the effect of vibration absorption plate is verified by simulation calculation method.(4)According to the actual track structure,a 25 meter long test platform is built,and the displacement and vibration responses of the track structure are measured under preload.Comparisons are made for the dynamic characteristics of the tracks with and without vibration absorbing plate,under different fastener stiffness and different value of pre-load.The track dynamic/static characteristic experiments provide reliable experimental data for the study of dynamic characteristics.(5)By replacing the original track structure with the one after optimization,i.e.fastener/vibration absorbing plate/floating slab structure,the elevated section of Shanghai Rail Transit Line 2 is selected as the test line.The performance of wheel/rail safety,track dynamics and vibration and noise reduction before and after the revamping are studied and analyzed.Meanwhile,the reliability of the optimization method of track dynamic parameters of multilayer elastic elements are verified. |
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