基于辐射声功率最小化的安静结构设计

Quiet structure design based on the minimization of radiated sound power

本文研究了一种基于模型修改使结构辐射声功率最小的方法,使用了结构动力学、声学和优化理论等学科知识,对结构修改后固有频率变化可以忽略不计时的声辐射优化进行了研究,将设计变量看作外部阻抗,对结构的表面振速进行了重新分布,可以降低结构辐射的声功率。将质量块与动力吸振器进行组合实现声辐射最小化,不但降低了一定频率范围内的平均声功率,还降低了动力吸振器所对应的单频下的声功率;运用遗传算法搜索结构辐射声功率最小时附加质量块或动力吸振器的位置,对附加质量块和有源控制作用下简支钢板的声功率最小化进行了比较研究,阐明了附加外部结构与有源控制实现安静结构的物理机理。最后,对本文提出的基于平板辐射声功率最小化的安静结构设计方法进行了实验验证。

Abstract An approach for solving the problem of vibration-acoustic optimization for a vibrating structure by material tailoring is investigated theoretically and experimentally. A structure is optimally designed to fit a specified set of acoustic characteristics, e.g. changing the sound spectrum or minimizing the radiated power. The method links the disciplines of structural dynamics, acoustics and optimization into a unified methodology. Firstly, the eigen-values are considered unchanged, the design variables are taken to be the addition of masses or vibration absorbers or their combinations to the structure as well as the distribution of stiffeners. The sound power generated by a simply supported plate under a harmonic force is computed with a lumped parameter or wave superposition method. A genetic algorithm is used by using MATLAB code to find the optimal point mass distribution for minimum of the sound power. Secondly, a comparison between masses adding and active structural acoustic control is investigated. Finally, experiments are carried out to verify the validation of the theoretical method. It is shown that optimal designs are achieved through converting certain mode shapes of the structure into the ＂quiet structure＂.