Research For Prediction Of Noise In Structure-Acoustic Coupling System Of Rail Car

With high speed developing of railcar industry, vehicle noise not only seriously affect the comfort of passengers,but also can bring parts fatigue damage of railway vehicle in early stage. So it reduce the service life of railway vehicle and restrict the development of railway traffic to a certain extent. Therefore,this paper focus on researching on acoustic-structure coupling system of a railcar base on finite element method and boundary element method has realistic meaning.This paper mainly aims at following aspects:Firstly,the structural model of the railcar has been simplified as assemblage of shell and beam,and the geometric model of structure body has established with I-DEAS.Then,the finite element model of the structure body ,the air cavity and the acoustic-structure coupling system of railcar have set up by Hypermesh after the research of contact technology of the finite element model of the structure body and the air cavity in the acoustic-structure coupling model.Secondly,the structure, air cavity and acoustic-structure coupling mode have been analysed by ANSYS and SYSNOISE.Due to the symmetry of the length, width and height of air cavity,the modes of cabin sound field are eudipleural, front-back and up-down symmetrical. Compareing with the strcture mode of body which is not took interior air into account,for the first mode,the frequency of the acoustic-structure coupling system mode is decrescent,and close to the first modal frequency of cabin sound field, for rest modes, mode shapes are Similar, differencies in frequency are few.Then, the acoustic-structure coupling system which is applied a harmonic unit excitation at vertical, longitudinal and transverse drietions is analyzed from 0 to 200 Hz, the vibration response of railcar body at different frequency is obtained.Lastly, basing on FEM and BEM, research and predition on interior sound field of the acoustic-structure coupling system of bare railcar is performed. Field point plane and test points are chosen according to ISO3381 and the ISO3095. The sound pressure level of field point plane is almost eudipleural about the center line of railcar body at most frequencies. The maximal SPL located at the midst of the railcar is 102 dB at 110Hz.The SPL results from BEM are bigger than the SPL results from FEM in the same position of interior sound field at each frequency.The maximal A-weighted SPL is 84.6dBA at C test point (0, 0, 1.2) , the maximal A-weighted SPL of the rest test points are about 75dBA.