含共振单元微穿孔板型周期结构材料的声学性能研究

This project takes the microperforated panel periodic structure materials including resonance elements as the research object. The acoustic performance of micro perforated panel periodic structure including resonance elements are studied by using the finite element method, numerical simulation and laboratory experiment. Based on the finite element theory, the acoustic performance of the microperforated panel is analyzed from the point of view of the bandgap property of periodic structure. Compared with the classical theory of microperforated panel, the inner connection and difference between them are analyzed. The main purpose is to develop a more reasonable method to guide the microperforated panel absorption of low frequency noise. Then, the periodic distribution cell holes are arranged on the microperforated panel, a film unit and a mass block are pasted on each cell hole, and the local resonance structure is formed. Microperforated panel periodic structure including resonance elements is established by finite element method. Energy band structure is calculated. Combined with the analysis of the vibration modes at the bandgap edges, the mechanism of the bandgap generation are explained. Effects of the geometry parameters of the resonance elements are discussed. The optimum design of the microperforated panel periodic structure materials including resonance elements will be proposed. This study not only provides solid foundations of developing new low-frequency broadband sound absorbers, but also is an exploration of new metamaterials combined with sound structure for the application.

本项目以含共振单元的微穿孔板型周期结构材料为研究对象，采用有限元理论分析、数值模拟和实验室实验相结合的方法，系统地研究含共振单元的微穿孔板型周期结构材料的声学性能。通过有限元理论从周期结构的带隙特性角度分析微穿孔板的声学性能，与经典的微穿孔板理论进行比较，分析它们的内在关联与区别，发展较为合理的方法指导微穿孔板吸收低频噪声。然后，通过在微穿孔板基体上开设周期分布的单元孔，每个单元孔贴上薄膜型共振单元及质量块，构成局域共振结构。利用有限元方法建立含共振单元的微穿孔板型周期结构材料，计算能带结构，结合带隙的边界模态分析，分析带隙产生的机理，讨论共振单元的结构几何参数对带隙及带通特性的影响，优化结构参数配置，提出具有低频宽带隙的含共振单元的微穿孔板型周期结构材料的较优的设计方案。本项研究是拓宽微穿孔板吸声结构吸声性能的一个新思路，也是新型超材料与声学结构付诸应用的一个探索。

微穿孔板吸声体具有良好的低频吸声性能，但由于基于共振原理有效作用带宽较窄。为了拓宽微穿孔板结构的吸声带宽，本项目研究了含共振单元微穿孔板型周期结构材料的声学性能，通过三年的研究取得了以下主要研究成果：. 结合有限元理论和实验室实验，研究了附加不同质量块的单胞薄膜型声学超材料的隔声性能，分析了结构的负质量密度产生的频带范围，解释了薄膜型声学超材料的传递损失变化规律；研究了轴对称分布的质量环的质量密度、与薄膜的接触面积，放置位置等变化时对薄膜型声学超材料传递损失的影响；设计了一种薄膜型声学超材料扩散体，并与传统施罗德扩散体的扩散性能进行比较，发现调控后的薄膜超构表面声扩散体对声能的吸收降低，并使入射声能更均匀地向全方向扩散。. 建立了L型分割背腔的微穿孔板吸声结构的等效电路模型，数值模拟和实验结果表明L型分割背腔的微穿孔板吸声结构能明显改善微穿孔板的低频吸声性能；开发了一种超微孔微穿孔板的制造工艺，通过传统工艺在热缩片上制作微孔，经过受热收缩后得到比传统工艺孔径缩小20%-80%的孔，实现了超微孔微穿孔板的加工；研究了薄层纺织材料的编织工艺、纤维细度、纤维孔隙率、材料的表面密度参数对其吸声性能的影响，实现薄层纺织材料的吸声性能优化设计，并研制出两种具有良好吸声效果的薄层纺织材料样品；利用PP材料通过纺粘工艺开发了一种相当于超微孔板结构吸声性能的无纺布吸声材料。. 在微穿孔板薄膜单元复合结构上，增加质量块，组成微穿孔板结合薄膜型声学超材料结构。通过阻抗管系统对超材料结构进行测试，结果表明，膜单元和质量块可以通过引入附加的吸收峰来改变MPP的吸声性能，通过合理设计MPP、膜单元尺寸、数量、和质量块位置，可以获得吸声性能良好的吸声结构；建立了内置微穿孔板的周期型膨胀腔结构的有限元模型，研究表明，微穿孔板的引入使结构的第一通过频率消失，隔声带宽明显增大。