Study On Air-borne Sound Of New Silent Rail In Metro Depot

In recent years,with the rapid development of science and technology and productive forces in our country,the population has shown a trend of concentration to the city,which leads to the continuous emergence of super-large-scale cities.However,the existing infrastructure can not meet the growing needs of people’s daily life,especially the transportation problem,so the development of subway has become an important way to meet people’s daily travel needs.The Metro Depot,which takes on many tasks such as Metro train overhaul,trial operation and so on,is the "Gas station" and "Safe harbor" for metro trains.However,during the operation of metro depot,serious noise is produced,which has a bad effect on the surrounding environment.Therefore,it is urgent and necessary to study the noise reduction performance of silent rail in vehicle depot.The main noise source of the metro train is the noise generated by the train running on the test line and in and out of the depot.Since most of the test track and storage track are normal 50kg/m rail,this paper is based on a special assembly on the normal 50kg/m rail,the noise reduction performance of the new rail damper applied to the test line of the vehicle depot and the in and out of storage was studied.In this paper,based on the modal analysis theory and harmonic response analysis theory,the normal 50kg/m rail-slab model and the silent rail-slab model are established by Hypermesh and Abaqus,the vertical modes,the vertical harmonic response and the vibration attenuation rate of the normal 50kg/m rail and the silent rail are obtained respectively.Then the field force hammer experiment was carried out to verify the accuracy of the numerical simulation model.Then through virtual.Lab established the sound field model of Metro Vehicle Depot,and obtained the noise reduction degree of the silent rail compared with the normal 50kg/m rail at the maximum running speed of the test line and the storage.Finally,by modifying the material parameters of the damper,the effect of density,elastic modulus and loss factor on the noise reduction is discussed.The main conclusions are as follows:(1)The results of modal analysis show that the modal frequency of the silent rail moves forward compared with that of the normal 50kg/m rail under the same modal array,and the phenomenon is more obvious with the increase of the modal order;This can also be used to explain the forward movement of a pinned-pinned resonant frequency.(2)The results of the vertical harmonic response analysis show that the first-order pinned-pinned resonance occurs at 883 Hz and 740 Hz for the normal 50kg/m rail and the silent rail,respectively.The first-order pinned-pinned resonance frequencies of the numerical simulation model are calculated at 878 Hz and 724 Hz,respectively At the same time,the first-order pinned-pinned resonance frequency of rail is calculated by the formula at 865 Hz,and the accuracy of the model is verified The rail damper can effectively reduce the first-order pinned-pinned resonant frequency and the response amplitude of the rail at that frequency.(3)The results of attenuation rate analysis show that the attenuation rate of silent rail is higher than that of normal 50kg/m rail in the range of 80-2500 Hz,and the transmission of rail vibration can be effectively restrained by using rail damper.(4)The results of acoustic analysis show that with the increase of train speed,the noise reduction effect of silent rail is more obvious,and the effect of damper is more obvious in the middle and high frequency part(after 200Hz)of noise.(5)The results show that the elastic modulus of damped rubber is more effective with the decrease of the value,but too low or too high elastic modulus will be unfavorable to the noise reduction of rail The noise reduction effect is more obvious with the increase of damping rubber loss factor;the noise radiation will increase when the damping rubber disconnects from the bottom of the rail;the noise reduction effect of the silent rail will be obviously enhanced with the increase of mass density,but with the increase of density,the noise reduction degree is reduced,and the effect of noise reduction of silent rail is improved by using steel restraint layer with larger elastic modulus and density.