多自由度低频抑振器的抑振降噪机理研究

The dominant structural noise of underwater vehicles in low speed or medium speed is limited at the low and the middle frequency. At present, how to decrease the structural vibration and acoustic radiation at the low frequency, especially at the extreme-low frequency, is still a great challenge. The traditional acoustic covered coating has little effect on the vibration-acoustic reduction at the extreme-low frequency, and the effect of dynamic vibration absorber on the suppression of bending wave propagation is also not satisfactory.. The multiple-degree-of-freedom vibration suppressor has been proposed in this project, which the major part of suppressor is a viscoelastic hollow cylinder, and a mass is placed at the top of the cylinder. Because there are many degrees of freedom and more vibration modes in the suppressor, which may dissipate vibration energy in different ways such as both resistive suppression and resistant suppression, then the bending vibration of plate and shell at low frequency will be suppressed effectively.. Using the theoretical, numerical and experimental methods, the mechanisms that the bending wave is suppressed by the multiple-degree-of-freedom vibration suppressor and the reduction of vibration-acoustic radiation caused by the external excitation will be revealed firstly. Then, the relationship between the performance of vibration-acoustic reduction and the structure, materials and arrangement of vibration suppressor will be analyzed. Besides, the vibration-acoustic performance of plate and shell which are attached with suppressors arrays will be studied, and the integrated optimization including the structural parameters, material properties and arrangement of vibration suppressor will be profiled. Finally, some meaningful developments on the design and application of low-frequency vibration suppressor will be provided.

中低速航行的水下航行器结构噪声以中低频噪声分量为主，如何降低低频，尤其是极低频的结构振动声辐射是一个极大挑战。声学覆盖层技术对降低如此低频的振动噪声收效甚微，而动力吸振器技术对抑制壳体中的弯曲波传播也效果欠佳。. 本项目提出一种多自由度低频抑振器，其特点是以黏弹性材料为主体的、在顶端有一质量块的空心圆筒结构。该抑振器存在多自由度方向运动和更多振动模态，具有阻式和抗式抑振等多种耗散振动能量的方式，能有效抑制低频离散线谱的弯曲振动。. 本项目拟通过理论分析、数值计算和实验测量等手段，分析多自由度低频抑振器抑制结构弯曲波传递、降低受激振动声辐射的机理，建立抑振降噪特性与抑振器结构材料及布局方式的关系，研究附连抑振器阵列的板壳结构振动声辐射特性，并对抑振器的结构材料和布局方式提出综合优化设计方法。预期通过本项目研究，将为低频抑振器的设计和应用提供重要的理论基础和技术支持。

多自由度低频抑振器存在多自由度方向运动和更多振动模态，具有阻式和抗式抑振等多种耗散振动能量的方式，能有效抑制低频离散线谱的弯曲振动，利用该特性可有效改善弹性板壳结构的振动声辐射特性。本项目主要开展了以下研究内容：.1）多自由度低频抑振器的抑振特性研究。包括单个低频抑振器对弹性梁中弯曲波的传播衰减机理和规律，两种不同的低频抑振器阵列形式对弹性平板中弯曲波的传播衰减的机理和规律，低频抑振器及阵列的抑振降噪特性及参数化分析。.2）多自由度低频抑振器的吸声特性研究。包括多自由度低频抑振器的吸声模型建立，单个多自由度低频抑振器的吸声特性及参数化分析，多自由度低频抑振器阵列的吸声特性分析等内容。.取得的主要结果如下：.1）建立了多自由度低频抑振器的抑振降噪分析模型，指出黏弹性主体材料的损耗因子、弹性模量，顶端质量和内部空腔直径是影响低频抑振器抑振降噪特性的主要参数。对于低频抑振器阵列，纵向布置比横向布置有更好的抑振和降噪效果。将安装位置靠近振源后，可提高纵向布置时高频范围的抑振效果，以及全频段的降噪效果。.2）建立了多自由度低频抑振器的吸声特性分析模型，指出黏弹性主体材料的弹性模量和内部空腔直径是影响低频抑振器吸声特性的主要参数，在低频时减小杨氏模量或者增大内部空腔半径均可有效提高吸声性能。通过布置多个具有不同吸声频率和吸声带宽的低频抑振器形成阵列，可有效提高低频抑振器的低频、宽带吸声性能。.3）通过项目实施，共发表论文11篇，其中SCI检索4篇，EI检索4篇。培养毕业硕士研究生3人。.本项目相关研究成果为多自由度低频抑振器的设计和应用提供了理论基础和技术支持。