Characteristics And Optimization Of The Vibration And Noise Reduction Of An Embedded Track Structure For Tram

Modern tram is becoming an important part of urban rail traffic due to its unique advantages.Along with the requirements of low vibration and low noise for people,as a good track type,embedded track can reduce wheel-rail vibration and noise during its traveling which can satisfy people's needs better.Because of the less research on embedded track and considerable application foreground of embedded track,this thesis established the embedded track finite element and acoustic boundary element model in frequency domain,and established the resilient wheel and considered the wheel contribution into the wheel-rail relative force excitation model.Furthermore,the research of the vibration and sound radiation characteristics of the embedded track were studied by the finite element and boundary element method.Through the calculation of the embedded track vertical vibration prediction model excited by unit force,the embedded track natural vibration characteristics could be predicted.Combined with the modal analysis,the results showed that embedded track vibration displacement admittance appeared peaks at 240Hz,300Hz and 420Hz,which were close to the modal resonance frequency.Embedded track modal number was dense within 1000Hz.The vibration of rail and elastomer in the gutter was significant.According to the application of embedded track on the actual railway line,the rail roughness and wheel roughness as an input excitation was used to simulate wheel-rail force when the tram was traveling at 60km/h on the track,meanwhile the embedded track vibration characteristics excited by wheel-rail force was analyzed,the results showed that embedded track had excellent vibration and noise reduction ability which could significantly reduce the vibration along vertical,horizontal and longitudinal direction of the track.The sound radiation characteristics of embedded track was predicted by the acoustic boundary element model,the results indicated that the significant sound radiation frequency spectrum was in the range of 250?1250Hz.The biggest noise source contribution came from the gutter for the embedded track,and the contribution of slab was less.Because the vibration and noise mainly came from the gutter for embedded track,the material parameters of the elastomer,prefabricated blocks and elastic pad should be investigated,which concluded Young's modulus and damping loss factor.The vibration and sound radiation of embedded track was analyzed under different material parameters,and the results showed that within the limited range,the Young's modulus optimal values of elastomer,prefabricated blocks and elastic pad were 25MPa,15MPa and 5MPa,and the damping loss factor optimal values were 0.20,0.30 and 0.30.Changing the shape of the prefabricated blocks and designing four new embedded track types,the effect of the shape of the prefabricated blocks could be studied through comparing with the vibration and sound radiation of origin embedded track.Combined the optimization results of material parameters and the shape of the prefabricated blocks,the integrated scheme could be acquired.Within the limited wheel-rail roughness excitation,the vibration and sound radiation of the integrated scheme could reduce 1.7dBA comparing with the origin scheme.