关键词: 2.5维有限元法, 2.5维边界元法, 高速列车, 铝型材, 振动声辐射, 隔声

Abstract: Aluminium extrusions are main components of multi-layered composite structures from high-speed train carriages. The vibro-acoustic behaviours of the extruison are highly relevant to the interior noise and riding comfort. Due to its large size and complex geometry, the analytical solution and traditional finite element(FE)/boundary element(BE) methods are limited to the vibro-acoutic prediciton of such a structure. Since the cross-section is uniform in the longitudial direction, the extrusion can be idealized to a waveguide, especially when the structural wavelength is much larger than the dimension of the extrusion. It is widely accepted that the two-and-half dimensional (2.5D) FE/BE methods are particularly suitable to predict the vibro-acoustic behaviours of such a strcture. Therefore, the wave propagation model of the extrusion is establised using the 2.5D FE method, with which the wave types in the structure are catogorized. The acoustic fields on both sides of the structure are predicted using the 2.5D BE method. Combing with the boundary conditions at the interface of the extrusion with the fluids, the coupled 2.5D FE-BE model for vibro-acoustics of the structure is esbalised. Using the 2.5D FE-BE model, the effects of mechanical force location on the vibraion response, sound radiation power and sound radiation efficiency of the strucutre are analyzed. A method is proposed to equivalently treat the extrusion as an homogenous plate based on the dispersion relation. The influence of boundary conditions on the diffused field sound transmission loss (STL) of the structure are studied. Results show that at low frequecies and high frequencies, free waves with global and local cross-section deformation propagating in the structure contributes the vibration of the structure respectively. The flexual dispersion relation of the equivalent plate matches well with that of the extruson. Mechanical force location has a significant effect on the vibraiton response and radiated sound power, while has little influence on the radiation efficiency. The STL of the structure at stiffness-controlled regieon is greatly affected by the boundary conditions that the more the constraints, the higher the STL. These research results can provide theoretical guidance to vibration and noise reduction in the future study.

Key words: 2.5D finite element method, 2.5D boundary element method, high-speed train, aluminium extrusion, sound radiation, sound transmission loss