Sound Field Structure Coupled System Of Finite Element Analysis And Sensitivity Calculations

The numerical analysis for acoustic and the acoustic-structural coupling system has broad application in the industrial fields, such as the automobile, the aviation and the aerospace. Nowadays, people pay more and more serious attention to the noise problems. To reduce the noise and the vibration in the structure design, such as the automobile, has become a serous problem. The noise level is one of the key indexes to the evaluation for the design quality of the engineering structure. The conventional method for the analysis of the interior field noise sound level of the complicated structure is very difficulty, but 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 during design stages and provide the sound design basis for the analysis of the acoustic-structural coupling system. Therefore, it is helpful to reduce the noise with computer-aided design technique, in particular, the design optimization method of structural and multidisciplinary systems.This paper studies the numerical simulation and sensitivity analysis of coupled acoustic-structure systems with finite element method. For the analyzing and the optimization design of the interior noise, it is necessary not only to calculate the eigenvalue and the eigenvector, but also to calculate their sensitivities to the design variables. The concept of the left and right eigenvectors with regard to the eigenvalue problems of coupled systems is used in the paper and four propositions concerning this concept are then proved. In the new orthogonality and M-normalization condition of the coupled system, this paper accomplished the calculation of the eigenvalue, the eigenvector and their sensitivities, the sound pressure level and its sensitivity. The aim of this thesis is to provide the basis analysis of the acoustic-structural systems based on JIFEX, the large-scale engineering structural analysis and optimization software.The author's work includes:(1) Development of the finite element model for the acoustic-structural system based on the sound and the structure finite element analysis. Accomplishment the calculation of frequencies and modes with the new orthogonality and the M-normalization condition.(2) Dynamic sensitivity analyses of natural frequencies and the eigenvectors for the coupled system. Accomplishment of the calculation of the sensitivities of eigenvalue and the eigenvector. The accuracy analysis of this method is performed.(3) The modal frequency response and its sensitivity analysis for the coupled system using the direct method and the eigenmodes.This thesis is one of the part of the national key basis research development plan project (G1999032805) and the key project of the National Natural Science Foundation of China (No. 10032030).