板结构的振动声辐射及其隔声性能研究/the vibration&acoustic radiation and noise muffling charateris

2018-11-27 14:55:05

vibration noise 阻尼 used acoustic



随着科学的发展,人们生活水平的进一步提高和军事战略的需要,船舶的噪声及其控制问题已日益受到人们的关注。各种类型的板结构是被广泛应用于工程领域的一种结构形式,它不仅在受到外界激励时会向外辐射噪声,而且也可用于控制噪声的传播。阻尼技术是解决工程中振动和噪声问题的十分有效的手段。目前已被广泛应用于诸如航空航天、机械、船舶及家用电器等各个领域,有助于结构减少传递振动与声辐射的能力。
本文首先建立板的声辐射模型及辐射声功率与振动速度之间的关系。有限元计算结果表明加强筋可以降低表面振动速度,减弱结构辐射声功率。并对阻抗矩阵进行了特征值分析从理论上证明了特征向量对应的一组速度分布,其辐射效率正比于该阶特征向量对应的特征值。
本文还利用弹性理论中的Lame方程描述自由阻尼层的运动,并将阻尼层的位移沿阻尼层厚度方向展开,根据阻尼层与基层的位移连续性条件及阻尼层与声场的应力连续性条件,得到了自由阻尼层的位移表达式,进而得到了结构损耗因子与辐射声功率的计算公式。
针对声波入射板面时在某一特定频率或特定入射角度时会使声辐射能力大大增加并产生大量声能的大量透射这一现象,详细讨论了产生吻合效应的条件,并针对工程实际中所应用到的各种尺寸、材质的板分别推导了其吻合频率和临界频率的计算公式,得出了厚板和材料的各向异性均会使结构的临界频率下降的结论。
最后就工程中应用较广泛的各种类型板(加筋板、复合阻尼板)的隔声问题进行了详细全面的讨论。在认识隔声理论的前提下,给出了修正质量定律的公式,并总结了板材加筋以及敷设阻尼对结构隔声的影响,具有一定的工程实用价值。



with the development of technology, the enhancement of people’ living standard and the need of military strategy, the problem of ship noise controlling has received an increasing attention. Many kinds of plates have been used in engineering fields, which, under the outside implement, not only can radiate noise but also can be used in noise controlling. Damping technology is a very effective way to dispose of vibration and noise problem. At present, it has been extensively utilized in many spheres, such as aerospace, machinery and shipping, etc., which can lower the capacity of structural vibration and radiation.
In this paper, firstly an acoustic model and the relation between acoustic power and vibration velocity are established, FEM calculating results reveal that stiffener can lower the face vibration velocity and the radiatonn acoustic power. Besides, eigenvalue analysis is used in sound-impedence matrix. With the help of optimization theory, the conclsion is receiced that the radiaton efficiences by a group of velocity distribution corresponding to eigenvector are proportional to the eigenvalue of the velocity vectors.Secondly, the lame equation is used to model the motion of the free-layer damping. The motions are expanded in the depth direction. The continuous conditions of stress and displace at the layer’s inter face are used. The structural loss factor is presented.
Thirdly, considering when acoustic wave with a certain frequency or angle is incident upon plates, it will greatly cause the radiation power’ translating. This paper details the causes of coincident effect and infer the calculating formula. The conclusion is resulted that thick plate and uniaxial anisotropics can lower critical frequency.
On the basis of above parts, this paper discusses the noise-muffling of several kinds of plates. It gives the modifying formula of the mass law and verifies its accuracy with an example. At last, this paper explains the effect of stiffeners and damping on the plates’ muffling characteristics.