共查询到19条相似文献,搜索用时 109 毫秒
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本文提出了一种新型局域共振复合单元声子晶体结构, 并结合有限元方法对结构的带隙机理及低频共振带隙特性进行了分析和研究. 共振带隙产生的频率位置由所对应的局域共振模态的固有频率决定, 并且带隙宽度与局域共振模态的品质因子及其与基体之间的耦合作用强度有关. 采用局域共振复合单元结构可以实现声子晶体的多重共振, 在低频范围能打开多条共振带隙, 但受到共振单元排列方式的的影响. 由于纵向和横向局域共振模态的简并, 复合单元结构能在200 Hz以下的低频范围打开超过60%宽度的共振带隙, 最低带隙频率低至18 Hz. 这为声子晶体结构获得低频、超低频带隙提供了一种有效的方法.
关键词:
局域共振
低频带隙
复合单元
声子晶体 相似文献
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运用FDTD(时域有限差分法)研究了弹性波/声波通过二维正方形排列的铁/水声子晶体的传播特性.发现铁/水声子晶体在高频范围存在完全带隙,软包层铁/水声子晶体在低频范围出现共振带隙,它们分别对应于不同的带隙形成机理.通过铁/水声子晶体和软包层铁/水声子晶体的组合,可以得到从高频到低频的组合宽带隙结构,从而达到在更宽频范围内控制弹性波传播的目的;而且通过调整包层的厚度、铁芯的大小、以及填充率等结构参数,可以有效地调节组合宽带隙的频率结构. 相似文献
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借助于平面波展开法分析了二维复式格子声子晶体能带结构,计算了铝合金柱体按周期性结构排列在空气中形成的二维固/气复合体系的声子晶体,给出了复式蜂窝格子和复式Kagome格子的能带结构,进而对比分析了复式格子和简单格子的能带结构特性.结果表明,与简单格子相比,复式格子的带隙出现在频率相对较低的位置;在f=0.091—0.6046范围内,将声子晶体排列为复式格子要优于简单格子,可以得到更宽带隙.此外,引入了带隙分布图,讨论了填充系数f对带隙数目、带隙宽度以及带隙上下边界频率的影响.
关键词:
声子晶体
复式格子
带隙
平面波算法 相似文献
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本文利用集中质量法对弹性纵波在一维指数形截面有限周期声子晶体中的传播进行了研究, 得到了频率响应函数的表达式. 与一维等截面的声子晶体相比, 指数形变截面声子晶体带隙内的衰减值随着输出端截面积的增大而减小, 同时带隙的起始频率降低而截止频率升高, 也即带隙的宽度会得到拓展. 晶格常数和材料组份比变化时, 变截面声子晶体带隙的起始频率和截止频率的变化趋势与等截面时的声子晶体相同. 希望本文的研究能够推动声子晶体在减振降噪等领域中的应用. 相似文献
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设计了一种多频局域共振型声子晶体板结构, 该结构由一薄板上附加周期性排列的多个双悬臂梁式子结构而构成. 由于多个双悬臂梁式子结构的低频振动与薄板振动的相互耦合作用, 这种局域共振型板结构可产生多个低频弯曲波带隙(禁带); 带隙频率范围内的板弯曲波会被禁止传播, 利用带隙可以实现对薄板的多个目标频率处低频减振. 本文针对这种局域共振型板结构进行了简化, 并基于平面波展开法建立了其弯曲波带隙计算理论模型; 基于该模型, 结合具体算例进行了带隙特性理论分析. 设计、制备了一种存在两个低频弯曲波带隙的局域共振型板结构样件, 通过激光扫描测振仪测试证实该结构存在两个低频带隙, 在带隙频率范围的板弯曲振动被显著衰减. 相似文献
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We show that by placing a metal plate next to a two-dimensional phononic crystal, acoustic waves can tunnel through the combined structure at a specific frequency that lies inside the band gap of the phononic crystal. The enhanced transmission is attributed to the coupling of the input waves with the acoustically resonant states created between the metal plate and the phononic crystal. Experiments are in excellent agreement with the theoretical predictions. 相似文献
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We have studied the propagation of a surface acoustic waves (SAW), in a structure constituted by a 2D phononic film (a few micrometers thick and having lattice constants of a few hundreds of micrometers in the two directions of the propagation plane) deposited onto a homogeneous semi-infinite substrate. First, we have calculated the dispersion relations of the acoustic modes by using a plane waves expansion method. We found that the surface branch exhibits both the folding effect and a band gap for the propagation along some particular directions. This is a very interesting result which demonstrates that the effects related to the existence of the band gap (sound velocity dispersion, diffraction, refraction, ultrasound tunneling, etc.) can all appear, even if the thickness of the phononic film is much less than the penetration depth of the SAW. Then, we used an all-optical technique to monitor the spectral content of the SAW propagating along the GammaX direction in the reduced Brillouin zone. We show that a wave with frequency in the stop band, is destructively diffracted after it propagates through less than ten periods. Finally, we report on measurements of the Rayleigh wave phase velocity and we show that the transit time is independent of the distance traveled inside the phononic crystal, suggesting that tunneling trough the sample is involved. 相似文献
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《Comptes Rendus Physique》2016,17(5):512-517
We report on the existence of unidirectional phononic band gaps that may span over extended regions of the Brillouin zone and can find application in trapping elastic (acoustic) waves in properly designed multilayered 3D structures. Phononic isolators operate as a result of asymmetrical wave transmission through a slab of a crystallographic phononic structure with broken mirror symmetry. Due to the use of lossless materials in the crystal, the absorption rate is dramatically enhanced when the proposed isolator is placed next to a vibrational harvesting cell. 相似文献
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We present a comparative study on the acoustic tunneling through artificial periodical composites, from phononic crystals to acoustic metamaterials. We find that the features of the acoustic tunneling are closely related with the origins of band gaps. In particular, the band gap associated with the negative effective material parameter in the metamaterial results in a better analog of the tunneling effect to the quantum system. 相似文献
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Based on the transfer matrix method (TMM) and Bloch theory, the interaction of elastic waves (normal incidence) with 1D phononic crystal had been studied. The transfer matrix method was obtained for both longitudinal and transverse waves by applying the continuity conditions between the consecutive unit cells. Dispersion relations are calculated and plotted for both binary and ternary structures. Also we have investigated the corresponding effects on the band gaps values for the two types of phononic crystals. Furthermore, it can be observed that the complete band gaps are located in the common frequency stop-band regions. Numerical simulations are performed to investigate the effect of different thickness ratios inside each unit cell on the band gap values, as well as unit cells thickness on the central band gap frequency. These phononic band gap materials can be used as a filter for elastic waves at different frequencies values. 相似文献
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声子晶体管路的带隙特性,可以实现管路系统在特定频率下的噪声控制.利用二维模态匹配法推导出单个内插扩张室元胞的传递矩阵,结合Bloch定理,得到声子晶体管路的能带结构计算方法;验证了二维方法在计算能带结构时的准确性.研究发现,内插扩张室声子晶体管路存在布拉格带隙和局域共振带隙.进一步研究了晶格常数以及内插管长度对能带结构的影响,结果表明,晶格常数主要控制布拉格带隙,而内插管长度对局域共振带隙有较大的影响,并研究了两种参数变化下的带隙耦合.研究结果可以为管路降噪设计提供新的思路. 相似文献
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《Comptes Rendus Physique》2016,17(5):543-554
The propagation of intense acoustic waves in a one-dimensional phononic crystal is studied. The medium consists in a structured fluid, formed by a periodic array of fluid layers with alternating linear acoustic properties and quadratic nonlinearity coefficient. The spacing between layers is of the order of the wavelength, therefore Bragg effects such as band gaps appear. We show that the interplay between strong dispersion and nonlinearity leads to new scenarios of wave propagation. The classical waveform distortion process typical of intense acoustic waves in homogeneous media can be strongly altered when nonlinearly generated harmonics lie inside or close to band gaps. This allows the possibility of engineer a medium in order to get a particular waveform. Examples of this include the design of media with effective (e.g., cubic) nonlinearities, or extremely linear media (where distortion can be canceled). The presented ideas open a way towards the control of acoustic wave propagation in nonlinear regime. 相似文献
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We report on an ‘in plane mode’ band gaps investigation of a novel diamond CRS (circle-rectangle-square) shaped holey phononic crystals in the desired operating frequency ranges. An ultra-wide band gap for diamond in the ‘in plane mode’ is observed. We also investigate an ultra-wide acoustic band gap for a finite one-dimensional (1D) diamond CRS phononic crystal (PnC) in the ‘out of plane mode’, and an ultra-wide acoustic band gap of a finite two-dimensional (2D) diamond CRS phononic crystal (PnC) in the ‘out of plane mode’ based on the FEA (Finite Element Analysis) method. We analyze that the transmission response of diamond in the length extension and width extension manner is more reasonable. Ultra-wide peak attenuations in the transmission spectra of a CRS shaped diamond phononic crystal successfully reveal the complete band gaps. The wide band gap of a CRS shaped diamond phononic crystal and the wide peak attenuation strongly agree in the same frequency region. It is analyzed that when a CRS-diamond phononic crystal is employed for MEMS resonators with different tether widths the quality Q of the resonators improved, and the energy losses decrease with extremely low insertion loss. In addition, it is observed that the vibrational displacement of a resonator is reduced by employing a diamond phononic crystal. 相似文献