Research On Low Noise Design Theory And Optimization Method Of Bi-material Structures

Structure noise is one of the main noise sources. With more and more concerned about the living environment noise, noise and vibration control technology attracts more attention. After decades of research, traditional noise control technology has been developed to a mature stage and has little development space. So it is necessary to develop a more effective noise control technology. A bi-material structure is becoming a new research direction in noise and vibration reduction field. A bi-material low noise design theory and method will be the fundamental method to solve the problem of structure noise.This paper analyzes the domestic and international development on sound radiation theory and optimization design methods. The method links the disciplines of structural dynamics, acoustics and optimization into a unified methodology. The structural sound radiation is taken into the product design stage as a design index. A bi-material low noise design theory and method has been researched in-depth.The external sound radiation prediction model based on the green function is established. Theory of acoustic radiation under multi-frequency excitation has been studied, and an acoustic design sensitivity analysis method and Two-materials SIMP (the Solid Isotropic Material with Penalization) material interpolation model are given. Using topology optimization method, a bi-material low noise design theory and method is presented. The proposed theory and optimization method about bi-material structure low noise design is validated by testing method.This paper studied the following particular aspects:A detailed derivation of external sound radiation boundary element method based on the second Green equation is presented. The numerical method for calculating corners' coefficient is presented, facilitating numerical computation. Non-isoparametrical element transformation is given to deal with function singular integration. Gauss numerical integration method for solving the equations is given, while CHIEF method is simultaneously implemented to deal with the nonuniqueness of Helmholtz integral equation.Acoustic impedance matrix is introduced for studying the sound radiation theory under multi-frequency excitation and acoustic sensitivity analysis. The model of acoustic sensitivity subjected to the sound power is established. The sound radiation can be translated to the analysis of structure dynamic sensitivity and impedance matrix sensitivity. Taking a simple supported plate as a example, the trend of the acoustic sensitivity is given. It provides direction for structure low noise design.Bi-matrial interpolation theory, algorithm and model based on SIMP are given. Then topological optimization model of continuous structure with single constraint for minimal compliance is presented. Discussion is given for the topological optimization result using different optimization parameters. The numerical results shows, ideal topological results can be obtained through properly selecting individual optimization parameters.A study of low noise design method about bi-material structure based on the topology optimization theory is given. The element volume density and minimization of sound power are taken as design variable and design objective function respectively. Numerical results show that the optimization result possess low radiation property. The structural low noise design method proposed in this chapter provides a set of product design method for acoustic designers.Experimental study of the proposed method is given and compared with numerical results. The proposed theory and optimization method about bi-material structure low noise design is validated.