Research On Acoustic Radiation Sensitivity Analysis And Design Optimization Of Structural Vibration

With the rapid development of modern industrialization, noise pollution becomes more and more serious. Now it has been one of three major envitonmental problems and the others are water polluton and air pollution. Therefore the reduction of sound radiation from vibrating structures is a very important research field. Traditional noise control is mainly based on the experience of engineers, and it needs a lot of testing and a large number of human and financial resources. With the continuous development of computer technology, it is more possible to calculate the structural acoustic radiation with numerical methods. Based on existing methods and functions in the large-scale structural analysis and optimization software JIFEX, we developed functional modules, including numerical analysis, sensitivity analysis and design optimization of the structural-acoustic radiation. In order to reduce the acoustic radiation level, the structural vibro-acoustic problem is simulated by FEM and BEM, and a design optimization model is presented and solved with an effective optimization method. Numerical examples show their effectiveness.The research work is supported by the National Natural Science Foundation of China, "Optimization of coupled system of multi-disciplinary design theory and numerical methods" (10032030) and the National Natural Science Foundation of China (10772038,10728205). The main contents of the thesis are as follows:Chapter 1:An overview of structural-acoustic radiation, its sensitivity analysis and design optimization is provided, which consist of the background, some basic acoustic research methods, the progress of optimizing structural-acoustic and noise control. Additionally, the research work presented in this thesis is also introduced.Chapter 2:The basic theories of acoustics are described in this chapter. These mainly include:acoustic basic equations, Helmhotlz equations and boundary element equations as well as methods to calculate acoustic radiation power.Chapter 3:Finite element formulas are given to calculate structural vibration analysis and its sensitivity formulas are also given. Structural acoustic radiation and its sensitivity analysis are proposed on emphasis. The optimization model is presented and the numerical results verify the accuracy of the sensitivity of acoustic radiation and the effectiveness of the optimization model.Chapter 4:Acoustic radiation and its sensitivity analysis of composite laminated structure are studied in this chapter. With the use of quadrilateral elements, acoustic sensitivities with respect to plying thickness and plying angle are derived and the acoustic radiation optimization model of composite laminated structure is presented. Numerical results show the accuracy of acoustic radiation sensitivity and the effectiveness of the presented optimization model.Chapter 5:Acoustic radiation from structures under random excitation is studied. Base on the theory of pseudo excitation method (PEM) for random vibration analysis, it is extended to acoustic analysis combined with boundary element method (BEM). The formula of acoustic radiation problems are derived with PEM and BEM. Numerical results verify the proposed method.Chapter 6:The random excited structural-acoustic design optimization is studied in this chapter. Random acoustic radiation sensitivity is derived and random acoustic radiation optimization model is presented. Numerical results show the accuracy of sensitivity analysis and the effectiveness and feasibility of the proposed optimized model.The conclusions and outlook are given in the last part.