中文摘要：

最近研究表明, 将声子晶体中的局域共振现象引入到水下吸声材料的设计中, 可以观察到由局域共振引起的低频声吸收现象. 为了进一步揭示局域共振低频吸声机理并获得更优的水下低频声吸收性能, 研究了内嵌不同形状散射子的黏弹性声学覆盖层. 利用晶格和散射子在空间排布的对称性, 传统有限元方法得到简化, 从而节约了计算时间和存储空间, 并通过将简化有限元法计算得到的结果与传统有限元法计算的结果进行对比, 验证了简化有限元方法的正确性. 结合位移云纹图, 考察了特定频率点上振动模态与相应的局域共振吸声峰之间的关系, 揭示了内嵌圆柱形散射子的黏弹性覆盖层的吸声机理. 进一步讨论了相同体积下不同形状的圆柱形散射子对黏弹性覆盖层吸声性能的影响, 给出了提升覆盖层低频吸声性能的优化思路. 通过讨论不同芯体材质对内嵌圆柱形散射子的黏弹性覆盖层吸声性能的影响, 找到了改变第一共振峰位置的方法, 从而可以通过调整第一共振峰来实现特定频率范围内的宽带吸声.

英文摘要：

The low-frequency underwater sound absorption phenomenon induced by the localized resonance in phononic crystal shows a promising application for the design of underwater acoustic absorption material in recently study. To further reveal the sound absorption mechanism and optimize the low-frequency underwater sound absorption characteristic, the viscoelastic coating embedded with various shapes of scatterer is investigated. In this paper, to shorten the computing time of the original finite element program and save the core memory, the conventional finite element method is simplified due to the symmetry of the lattice and the scatterers, then the simplified finite element method is validated by comparing the results of the simplified finite element method with those of the conventional finite element method. The relationship between the resonance mode described with the displacement contours of one unit cell at specified frequencies and the corresponding absorption spectrum is discussed in detail, which reveals briefly the sound absorption mechanism of the viscoelastic coating embedded with cylindrical scatterer. Finally, the shape effect of the scatterer on the sound absorption characteristics is investigated, spherical scatterers and the three cylindrical scatterers with different shapes but the same volume are considered. Further, the influence of the density of the core on acoustic absorption characteristic under an air backing is discussed. The results show that lower sound absorption properties can be deduced by adopting the cylindrical scatterers and reducing the radius of the base of circular cylindrical scatterer, and the absorption bandwidth can be improved by choosing the optimal scatterer material.