Acoustic - Structure Coupling System Vibration Analysis And Sensitivity Analysis

Nowadays, people pay more and more serious attention to the noise problems with the passenger compartments of vehicle, ship, submarines and aircrafts. These compartments are considerably complicated acoustic systems not only because of their complex structures and irregular shapes, but also because of the sound-absorbing materials attached to the structural boundaries. The finite element method provides a very powerful methodology for analyzing vibration and acoustic problems with complicated geometry and boundary conditions. Therefore, this method can be used to acoustic-structural coupled system and to accomplish the theoretical analysis and prediction of noise response of the passenger compartments during design stages.It turns out that study on the coupling acoustic-structural characteristics of the compartments plays key roles in noise control and acoustic design. The sensitivity analysis for the acoustic-structural system can be conveniently and quickly used in dynamic modifications of the compartments to reduce their noise levels. It also sets up the foundation of optimum structural design.The aim of this thesis is to investigate the vibration of acoustic-structural systems as well as the system sensitivity analyses based on JIFEX, the large-scale engineering structural analysis and optimization software. Topics will be provided concerning with cavity acoustics theory, frequency, mode and response analysis of acoustic-structural FEM model, and sensitivity analysis of dynamic eigenvalues and responses for structural optimization. The author's work includes:(1). Development of the finite element model for the acoustic-structural system.(2). The finite element numerical approach for analyzing natural frequencies, modes and responses of the acoustic-structural system. Comparisons of solution precision and efficiency are made among these three methods.(3). Dynamic sensitivity analyses of natural frequencies and sound pressure levels for the coupled system.This thesis is supported by the key project of the National Natural Science Foundation of China (project number: 10032030).