Research On Vibration Absorption Of Floating Slab Track Based On Phononic Crystals

With the rapid development of urban rail transit,the vibration and noise problems generated during subway operation are becoming increasingly prominent.The vibration reduction and noise reduction of subway has become an urgent problem to be solved.Studying the vibration characteristics of track structures has important theoretical significance and engineering application value for the vibration reduction and noise reduction of subway.With the in-depth research on the dynamic characteristics of track structures,various forms of track structures have been proposed.Among them,the floating slab track structure system has become one of the most widely used vibration reduction and noise reduction measures for subways due to its ability to effectively reduce vibration caused by train operation.In recent years,the research of phononic crystals and acoustic metamaterial has gradually become one of the hot spots in the international scientific and technological field.This material can well solve the isolation problem of medium and low frequency noise,and has broad application prospects in the subway vibration and noise reduction.In this thesis,the low frequency vibration absorption performance of floating slab track steel spring vibration isolation device is studied,combined with the band gap characteristics of phononic crystals,this project intends to study a phononic crystals isolation device which can restrain the vibration and noise caused by the floating slab track from the aspects of reasonable lattice constant,scatterer structure and component material.The main work of this thesis is as follows:(1)Taking the low-frequency vibration of the subway as the research object,the energy band characteristics of the phonon crystal are considered comprehensively,and the appropriate lattice constants,scatterer structures and component materials are selected for the design of the phonon crystal unit structure.The energy band structure of the phonon crystal was calculated by numerical simulation using finite element analysis software.(2)The effects of material properties,cell structure size parameters and other factors on the energy band structure of the phonon crystal are investigated,and appropriate lattice constants,scatterer structures and component materials(steel,rubber,etc.)are selected for the vibration characteristics of the floating-plate orbit.(3)The overall three-dimensional model of the floating plate track is established,and the phonon crystal isolator is placed in the track,and the overall damping effect is calculated and compared with that of the steel spring isolator floating plate track.At 50 Hz,the phononic crystal isolator has the most significant damping effect compared to the steel spring isolator.Below 143 Hz,the average damping effect of phononic crystal isolator floating plate track compared to steel spring floating plate track can be reduced by 7.2 d B.(4)The vibration damping performance of the phononic crystal was experimentally verified by placing the vibration isolator on a shaker and conducting a frequency sweep experiment in the frequency range of 5-143 Hz and a fixed frequency experiment at 50 Hz,80 Hz and 120 Hz.The experimental results show that the phononic crystal vibration isolator has good vibration damping effect at different frequencies.Specifically,the vibration transmission rate is reduced by 52.7 d B,29.5d B and 12.8 d B at 50 Hz,80 Hz and 120 Hz,respectively,and the experimental results are consistent with the general trend of the simulation results,which proves the feasibility of the theoretical design method.It is of great reference significance for the study of the performance and application of phononic crystal vibration isolators.