[MP]=the assembled fluid equivalent “mass” matrix,

[KP]=the assembled fluid equivalent “stiffness” matrix,

[M fs]=the assembled fluid-structure coupling “mass” matrix,

[K fs]=the assembled coupling “stiffness” matrix,

{P}{P:}=the nodal pressure vector and the vector of its second time derivatives respectively,

{U}=the nodal displacement vector and {U:}=the nodal acceleration vector.

3.2 ANSYS Unsymmetric Solver

In order to solve the set of governing equations presented in Acoustic-Structure Coupling, it was necessary to make use of the Lanczos algorithm implemented in the ANSYS Unsymmetric Solver. A verification procedure was first performed, to make sure the results produced were accurate. A mode-frequency analysis of the elastic shell in vacuo was carried out using both the Reduced and the Unsymmetric Solvers. With acceptable errors from the engineering point of view, the results were comparable. The comparison above gives sufficient confidence to apply the Unsymmetric Solver in the structure-acoustic modal analysis. It should be noted, however, that the so-called “shift” (the starting frequency or point of discovery) is of paramount importance for achieving meaningful results with the Lanczos algorithm. If some eigenvalues are clustered, the final outcome depends on the first step at which a hidden eigenvalue is expected. Bearing in mind the “strange” behavior of the Unsymmetric Solver, the “shift” value should be kept constant in all applications where any kind of comparison between the solutions is required. This approach was adopted in the present study. In addition, one should bear in mind that the Lanczos algorithm is suitable for extraction of some, but not all, eigenvalues and associated eigenvectors in the frequency ranges of interest. It is assumed that the frequencies extracted are “exact”, but some of the mode shapes may be distorted, hence they are difficult to recognize.

摘要 在低频率，结构声学分析的研究中，对交通车辆内部噪声的重新关注有了新的兴趣。封闭空腔内的内部声场受腔的声学模态特性的影响，由周围结构的动态特性，以及由这些动态系统耦合的性质。P最近的工作是为了更轻的汽车车厢结构和封闭的空腔之间的声学结构相互作用。本系统是采用ANSYS有限元分析（FE）有限设计建模涉及的结构和三维壳体有限元（3D）的空腔声学元件。三维有限元模态分析结果可视化的复杂图像声振耦合。有发现，在附近的任何声学共振的薄壁结构和声学外壳之间的耦合存在。也有发现声共振的附近存在“组合”的振动模态，这意味着耦合系统表现出一种新的能量交换。

毕业论文关键词：声振相互作用  振动  有限元

1 引言 汽车工业是一个持续不断的努力，以提高客运车辆的噪声和振动特性的产业。根据道路条件，在客运车辆的噪声频谱CLE在低频范围内< 400Hz发现主要是结构噪声（见例[1]）。从各种来源产生的振动能量传递到室腔通过结构连接。因此，空腔及其边界的振动特性是一个非常重要的因素，占主导地位的车辆乘客车厢的声学响应。不可预知的不发生时的车身和车厢系统加上封闭腔自然动态特性不好预测ISE的问题。各种车辆的噪声问题中，结构噪声如蓬勃发展的是一个详细的调查对象（见例[2]和[3]）。论文网