共查询到19条相似文献,搜索用时 62 毫秒
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采用有限元法,分析了含单层柱形空腔橡胶层(厚度20 mm)的吸声性能,表明其吸声峰频率比相同尺寸的球形空腔低,这与单个柱形和球形空腔的单极共振频率相对应,通过谐波散射分析证实了空腔单极共振引起的能量耗散增强了声波的吸收。采用能量耗散功率及位移场分布,对柱形空腔结构的吸声机理进行了深入分析.其次,在钢背衬条件下分析了横波损耗因子对橡胶层吸声特性的影响,并采用遗传算法对含不同尺寸柱形空腔橡胶层在1.5—10 kHz频段上的吸声特性进行了优化,获得了较好的宽频吸声效果. 相似文献
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水下吸声覆盖层对潜艇的隐身具有重要的意义, 因此得到了广泛的关注. 本文对含有玻璃微球的黏弹性复合材料覆盖层的水下吸声性能进行了理论分析. 采用等效参数法计算了玻璃微球的体积含量对复合材料的力学和声学性能的影响. 应用声波在多层介质中传播的一维模型, 计算了不同玻璃微球体积含量的单层复合材料覆盖层的吸声性能.结果表明, 增加玻璃微球的体积含量可以提高覆盖层的低频吸声性能, 但是其高频吸声性能降低.采用遗传算法对玻璃微球在覆盖层厚度方向上的体积含量分布进行优化. 优化的多层结构可以在一定的频带内改善覆盖层的表面与水的声阻抗匹配, 在保证覆盖层的高频吸声系数大于某一限值(0.7)的前提下, 提高其低频吸声性能.另外, 多层优化结构覆盖层不含宏观的空腔结构, 不影响覆盖层的耐压性能.其结构简单, 对制备工艺的要求不高.因此, 本文形成的理论方法适用于水下吸声覆盖层的设计.
关键词:
水下吸声
黏弹性复合材料
玻璃微球
遗传算法 相似文献
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为了揭示管束穿孔板共振吸声结构的吸声机理,利用热黏性条件下基于有限元算法的管束穿孔板仿真模型,研究了平面声波正入射条件下,管束穿孔板内部声场分布特征,并利用阻抗管对吸声系数的理论仿真结果进行了试验验证.结果表明,管束穿孔板在低频主要靠腔体共振吸声,在高频主要靠管共振吸声,管束穿孔板整体呈现出较为明显的管腔耦合共振吸声特征。管束穿孔板共振时管中声强和质点法向振速较大,高频次吸声峰频点处管中和腔中均有驻波形成,频率越高驻波数量越多.管束穿孔板的耦合共振受到管长、腔深、穿孔率和管内径等参数变化的影响,管长对高频耦合共振的影响最大,管长增大使高频主吸声峰频点移向低频,并使相邻主吸声峰之间的间距减小. 相似文献
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在水下结构表面敷设去耦覆盖层是降低其声辐射的有效途径. 为了深入分析一种含横向无限长空腔的覆盖层的去耦机理, 本文将其等效为均匀介质, 建立了敷设这种覆盖层的单向基体板在线激励下的声辐射模型, 验证了计算模型的有效性, 并利用计算模型对含横向空腔覆盖层的去耦机理进行了分析. 研究结果表明: 基体板-覆盖层接触面的能量流以纵波能量为主, 而横波能量很小, 因而计算覆盖层的去耦特性时可以忽略横波的作用; 和均匀覆盖层相比, 横向空腔型覆盖层在中高频段极大地增强了基体板的力阻抗, 从而更有效地抑制了基体板的振速; 此外, 和均匀覆盖层相比, 横向空腔型覆盖层和水的阻抗失配更大, 使其在中高频具有良好的振动传递损失特性. 因此, 总体而言, 含横向空腔的覆盖层相比均匀覆盖层具有更好的中高频去耦性能. 相似文献
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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. 相似文献
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Backing effects on the underwater acoustic absorption of a viscoelastic polymer slab embedded with locally resonant scatterers are reported. The polymer slab is embedded with two layers of locally resonant scatterers, i.e. Al spheres coated by soft silicon rubber. Theoretical absorption coefficients of the polymer slab under different backings using a layer multiple scattering method show good agreement with the experimental results, which supports unambiguously the experimental observation. Then relations between the resonance modes and the low-frequency absorption peaks of the composite slab are clarified to address the absorption mechanisms. It shows that the mass of the steel backing affects evidently the low-frequency absorption, the absorption peak shifts to lower frequency range while increasing the backing mass. 相似文献
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本文利用标准化动态力学测量手段获得了某种高分子聚合物的动态杨氏模量,并根据时温等效原理对动态杨氏模量与声学测量在频段上的差异加以分析和转换,得到了500—7500 Hz频率范围内该黏弹性材料杨氏模量随频率变化的特性.基于所测得动态杨氏模量,采用有限元方法分析了均匀黏弹材料的吸声性能,并将仿真结果与样品声管实验数据进行对比,验证了测试所得参数的准确性.进一步仿真分析了含有局域共振结构的声学覆盖层吸声性能,并讨论了黏弹性材料的动态特性对其吸声性能的影响,提出了改进水声覆盖层低频宽带吸声特性的建议. 相似文献
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Wide-band underwater acoustic absorption based on locally resonant unit and interpenetrating network structure 总被引:1,自引:0,他引:1 下载免费PDF全文
The interpenetrating network structure provides an interesting avenue to novel materials. Locally resonant phononic
crystal (LRPC) exhibits excellent sound attenuation performance based on the periodical arrangement of sound wave scatters.
Combining the LRPC concept and interpenetrating network glassy structure, this paper has developed a new material which can achieve a wide band underwater strong acoustic absorption. Underwater absorption coefficients of different samples were measured by the pulse tube. Measurement results show that the new material possesses excellent underwater acoustic effects in a wide frequency range.Moreover, in order to investigate impacts of locally resonant units,some defects are introduced into the sample. The experimental result and the theoretical calculation both show that locally resonant units being connected to a network structure play an important role in achieving a wide band strong acoustic absorption. 相似文献
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Reflection and transmission coefficients of rubberized coir pads over the frequency band 200 kHz to 4 MHz are presented in this Paper. These results are compared with those reported for neoprene, paraffin wax, rubber car mat and plastic door mat1. The rubberized coir pads were found to possess wideband absorption characteristics. It has been experimentally found that 0.05 m thick coir pads have almost 100% absorption in the frequency range 800 kHz-3 MHz with a maximum at 2.35 MHz. We have used this material for lining the water tank for underwater acoustic studies. 相似文献
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Effects of core position of locally resonant scatterers on low-frequency acoustic absorption in viscoelastic panel 下载免费PDF全文
《中国物理 B》2015,(8)
Locally resonant sonic materials, due to their ability to control the propagation of low-frequency elastic waves, have become a promising option for underwater sound absorption materials. In this paper, the finite element method is used to investigate the absorption characteristics of a viscoelastic panel periodically embedded with a type of infinite-long noncoaxially cylindrical locally resonant scatterers(LRSs). The effect of the core position in the coating layer of the LRS on the low-frequency(500 Hz–3000 Hz) sound absorption property is investigated. With increasing the longitudinal core eccentricity e, there occur few changes in the absorptance at the frequencies below 1500 Hz, however, the absorptance above 1500 Hz becomes gradually better and the valid absorption(with absorptance above 0.8) frequency band(VAFB)of the viscoelastic panel becomes accordingly broader. The absorption mechanism is revealed by using the displacement field maps of the viscoelastic panel and the steel slab. The results show two typical resonance modes. One is the overall resonance mode(ORM) caused by steel backing, and the other is the core resonance mode(CRM) caused by LRS. The absorptance of the viscoelastic panel by ORM is induced mainly by the vibration of the steel slab and affected little by core position. On the contrary, with increasing the core eccentricity, the CRM shifts toward high frequency band and decouples with the ORM, leading to two separate absorption peaks and the broadened VAFB of the panel. 相似文献
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本文围绕粘贴黏弹性吸声材料方法对水下小平台上安装矢量传感器的指向性和测向的影响展开理论分析和实验研究.首先建立了吸声材料和平台结构组成的复合层结构的数学模型,对声波经过复合层结构的声学特性进行了分析,在此基础上利用有限元耦合边界元法对粘贴吸声材料前后的水下小平台上的矢量传感器的声学特性进行研究.通过理论计算和数值分析研究了吸声材料对矢量传感器的各通道的指向性的影响,并计算了覆盖吸声材料前后矢量传感器的测向精度.水池实验验证了分析结果的正确性. 相似文献
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Acoustic scattering from a submerged cylindrical shell coated with locally resonant acoustic metamaterials 下载免费PDF全文
Using the multilayered cylinder model, we study acoustic scattering from a submerged cylindrical shell coated with locally resonant acoustic metamaterials, which exhibit locally negative effective mass densities. A spring model is introduced to replace the traditional transfer matrix, which may be singular in the negative mass region. The backscattering form function and the scattering cross section are calculated to discuss the acoustic properties of the coated submerged cylindrical shell. 相似文献
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提出了一种具有负模量特性的新型声学超结构,并揭示了其低频带隙的形成及拓宽机理.通过理论推导给出了该新型结构的归一化有效模量表达式,由于有效模量的零值点与系统参数密切相关,可以调节合适的参数使得零值点降低或带隙下界降低,进一步实现低频带隙.理论结果表明,在一定的频率范围内,系统的弹性模量为负且负模量区域进一步拓宽,从而通过负模量区域的放大而拓宽带隙.这种新的实现低频带隙的方法克服了传统局域共振附加质量过大及惯性放大结构带隙较窄的缺点.同时,通过有限元法得到的周期结构的传输率随着结构参数的变化趋势与理论分析的变化趋势基本一致,并得到了约40—180 Hz的低频宽带.这种实现低频带隙的新思路对低频声波的控制具有很重要的理论指导意义. 相似文献