Research On Vibro-acoustic Behaviour Of High-speed Train Windows Under General Boundary Condition

The noise and vibration outside high-speed trains can cause vibration of windows,leading to sound radiation into vehicles.Sound radiation is not only frequency-dependent,but also affected by the connections between windows and borders.It is necessary to investigate the vibro-acoustic behaviour of windows under general boundary conditions,and it is an effective way to control the interior noise of a high-speed train by sound radiation reduction and sound insulation improvement.Therefore,the purpose of this thesis is to establish a vibro-acoustic model for the window and the boundary conditions between the window and the border are accounted for.The impact of boundary supporting parameters on the vibro-acoustic behaviour are studied under different excitations,including point forces,acoustic plane waves,turbulent and border excitations.The research works include:Firstly,the finite element model(FEM)of a rectangular thin plate is established with Galerkin’s method based on Kirchoff thin plate theory and Hamliton theory.In the FE model,the supporting boundary conditions including translational and rotational springs and their corresponding damping are taken into consideration.Based on the acoustic Rayleigh integral,the boundary element models for the acoustic domains on both sides the plate are established.Using the coupling conditions between the plate and the fluids,the coupling FE-BE model for the vibro-acoustics of the plate is developed.Secondly,the coupling FE-BE model for a rectangular and thin plate is validated by applying to a thin aluminium plate.The model parameters extracted from the model are compared with the results from ANSYS.They match well with each other.The sound radiation and sound transmission loss(STL)from this model are compared with those of an infinite plate,of which analytical solutions are available.Except for frequencies near the sound radiation peaks or the STL dips and in the stiffness controlling area,the two show a good agreement.Finally,the verified FE-BE coupling model is applied to a window from high-speed trains.The influence of the supporting parameters on the vibro-acoustic behaviour of the window is investigated in condition of point forces,acoustic plane waves,turbulent and border vibration excitations.The effect of the point force locat ion on the radiated sound power of the window and the effect of the incident angle on the sound transmission loss of windows are analysed.It is shown that 1)the translational stiffness between the border and the window has a greater impact on the vibro-acoustics of the window than the rotational stiffness.When the translational stiffness is below 1×10~3N/m or above 1×10~6N/m,the sound radiation and STL do not change explicitly along with the stiffness,when between these two values,the vibro-acoustics are greatly affected with sound radiation peaks or STL dips vary abruptly;2)The damping from the supports can slightly affect the vibro-acoustic behaviour of the window only when it is larger than 0.1.The damping from the complex translational supports has a greater effect on the vibroacoustics of the window than those from the complex rotation supports;3)Increasing the connection stifness between the window and the border makes the vibration significanlty transferring from them,and therefore,it is not helpful for vibration and noise control of a high-speed train;4)Moving the point force to the boundary of the window can reduce the radiated sound power in the stiffness controlling region.When the point force is located at the belly of a modal shape,the corresponding mode is hardly excited and hence the corresponding sound raidation peak will not occur;5)Increaing the incident angle of an acoustic plane wave can improve the sound transmission loss at most frequencies.When the plane wave impinges on the window in the longitudinal and latteral directions of the window,the dyanmic response is symmetric about the mid-line of the plate in the corresponding direction.If the plane wave obliquely impinges in the diagonal direction of the window,the strong anti-symmetric response will occur.