固-固掺杂结构声子晶体中弹性波的缺陷模

为了研究弹性波在固-固掺杂结构声子晶体中缺陷模的特性,推导出弹性波斜入射固-固掺杂结构声子晶体的转移矩阵。利用它计算了固-固掺杂结构声子晶体中弹性波的透射系数,得到由于掺杂在禁带的中间出现了多条缺陷模透射峰带,缺陷模透射峰带随杂质厚度的变化呈周期性地出现,在同一缺陷模透射峰带上缺陷模的频率随杂质厚度增加近似呈线性减少。缺陷模的这些特征可以作为设计声子晶体滤波器的理论依据。     

利用叠加理论研究固-液声子晶体纵波的能带结构

采用相干叠加原理推导出一种研究一维固-液有限周期声子晶体中纵波的透射率公式,建立了一种研究一维固-液有限周期声子晶体能带的新方法——波叠加理论。将波叠加理论和转移矩阵法进行了比较研究,结果表明波叠加理论和转移矩阵法得出的结果是一致的。波叠加理论不仅具有转移矩阵法的优点,而且又克服了转移矩阵法的不足。因此波叠加理论是一种研究一维固-液有限周期声子晶体中纵波能带的更为有效的方法。     

固-液圆柱掺杂声子晶体中弹性波的缺陷模

利用一维固-液圆柱形掺杂声子晶体中弹性波横向受限的条件,推导出弹性波在一维固-液圆柱形掺杂声子晶体中各种模式满足的关系式,研究了各种模式弹性波的特性。利用转移矩阵计算出弹性波的缺陷模随模式量子数以及圆柱半径的变化规律,得到了一些一维固-液结构圆柱形掺杂声子晶体缺陷模的新特征。研究结果表明,缺陷模的频率和半高宽均与模式量子数和圆柱半径有关。     

固-固有限周期声子晶体中SH波全反射隧穿的机理

利用边界条件推导出SH波在一维固-固有限周期声子晶体中的转移矩阵,并用倏逝波的概念和多波束干涉理论,从理论上解释了一维固-固有限周期声子晶体全反射隧穿效应产生的物理机理,得出了全反射隧穿峰带波长满足的解析公式。利用解析公式和转移矩阵研究了一维固-固有限周期声子晶体中SH波的全反射隧穿效应,结果发现两种方法得出的结论是吻合的。     

固-固有限周期声子晶体中SH波全反射隧穿的机理

利用边界条件推导出SH波在一维固-固有限周期声子晶体中的转移矩阵,并用倏逝波的概念和多波束干涉理论,从理论上解释了一维固-固有限周期声子晶体全反射隧穿效应产生的物理机理,得出了全反射隧穿峰带波长满足的解析公式。利用解析公式和转移矩阵研究了一维固-固有限周期声子晶体中SH波的全反射隧穿效应,结果发现两种方法得出的结论是吻合的。     

SH波在局部非均匀声子晶体中的传播

使用传输矩阵法,研究了水平剪切波(SH波)在一维局部材料非均匀声子晶体中的传播。首先使用皮亚诺方程给出了SH波在特定非均匀梯度介质声场的传输矩阵。然后使用传输矩阵和布洛赫定律给出了该声子晶体的禁带结构和传输系数。通过具体计算,发现这种非均匀性能明显影响声子晶体的频散曲线和禁带结构。然后比较了幂指数取不同值时,禁带结构与归一化频率和填充比的关系。发现幂指数不同,声子晶体的禁带不同。     

弹性波斜入射声子晶体的传输特性

引入四维波矢的概念,推导出弹性波斜入射到多层介质系统的转移矩阵以及透射系数和反射系数公式.利用这些公式计算了横波和纵波斜入射一维声子晶体时横渡和纵波的透射系数,得出横波斜入射,透射波中的横波和纵波在一定频率范围内都会出现禁带,纵波斜入射时也有类似的结果.透射波中横波与纵波的相互转型随着入射角的增大而越加明显.     

一维固-液掺杂声子晶体缺陷模的机理研究

建立了一维固-液掺杂声子晶体的谐振腔模型,利用谐振腔的共振条件推导出了缺陷模频率满足的解析公式,从理论上解释了产生一维固-液掺杂声子晶体缺陷模的物理机理.利用频率的解析公式研究了缺陷模的频率随入射角、杂质厚度、杂质波速的变化规律.结果表明:缺陷模的频率随入射角和杂质波速的增加而增加,缺陷模的频率随杂质厚度的增加而减少,圆满地解释了一维固-液掺杂声子晶体缺陷模的变化规律.在此基础上并与转移矩阵法的计算结果进行了比较,其结果吻合.     

一维声子晶体中声波能带的解析研究

为了对一维声子晶体的能带进行解析研究,采用一维声子晶体的色散法,推导出一维声子晶体禁带频率和通带频率的解析公式;并利用此式对一维声子晶体的能带结构进行了解析研究,得到了禁带和导带的频率中心、频率宽度分别随介质厚度和声阻抗两者的变化规律,并与转移矩阵方法的计算结果进行了比较.研究结果表明:两种方法得到的结论相同,但解析法能更准确、更深刻地反映出一维声子晶体的能带随介质厚度和声阻抗等因素的变化规律;并且解析法克服了转移矩阵法等其他方法不能对能带结构进行解析研究的不足,是一种研究一维声子晶体能带更有效的方法.     

圆管型局域共振声子晶体三维构型振动带隙研究

采用多重多级子结构方法计算具有一定刚度的圆管型局域共振声子晶体三维构型振动带隙特性。考察包裹方向对带隙特性的影响,并对第一带隙上下边界点的单胞振动形式进行分析。结果表明,两种包裹形式都可以得到较低较宽的第一带隙,并且带隙特性相似,因而其周期结构都可以大幅减弱带隙范围内弹性波的传播。但两种构型带隙上下边界点对应振动形式不同,此外带隙特性还受单胞尺寸的影响。通过给定评价指标得到相关材料参数与带隙特性关系的相图,由此分析包裹层材料属性对带隙特性的影响。     

Shear wave propagation in periodic phononic/photonic piezoelectric medium

Coupled electro-elastic SH waves propagating oblique to the lamination of a one dimensional piezoelectric periodic structure are considered in the framework of the full system of Maxwell’s electrodynamic equations. The dispersion equation has been obtained and numerical analyses carried out for two kinds of composites both consisting of two different piezoelectric materials. The results demonstrate the significant effect of piezoelectricity on the widths of band gaps at acoustic frequencies and confirm that it does not affect the band gaps at optical frequencies.     

Propagation behavior of elastic waves in one-dimensional piezoelectric/piezomagnetic phononic crystal with line defects

Using a stiffness matrix method, we in- vestigate the propagation behaviors of elastic waves in one-dimensional （1D） piezoelectric/piezomagnetic （PE/PM） phononic crystals （PCs） with line defects by calculating energy reflection/transmittion coefficients of quasi-pressure and quasi-shear waves. Line defects are created by the re- placement of PE or PM constituent layer. The defect modes existing in the first gap are considered and the influences on defect modes of the material properties and volume fraction of the defect layers, the type of incident waves, the location of defect layer and the number of structural layers are discussed in detail. Numerical results indicate that defect modes are the most obvious when the defect layers are inserted in the middle of the perfect PCs; the types of incidence wave and material properties of the defect layers have important effects on the numbers, the location of frequencies and the peaks of defect modes, and the defect modes are strongly de- pendent on volume fraction of the defect layers. We hope this paper will be found useful for the design of PE/PM acoustic filters or acoustic transducer with PCs structures.     

Size effects on the mixed modes and defect modes for a nano-scale phononic crystal slab

The size-dependent band structure of an Si phononic crystal(PnC) slab with an air hole is studied by utilizing the non-classic wave equations of the nonlocal strain gradient theory(NSGT). The three-dimensional(3D) non-classic wave equations for the anisotropic material are derived according to the differential form of the NSGT. Based on the the general form of partial differential equation modules in COMSOL, a method is proposed to solve the non-classic wave equations. The bands of the in-plane ...     

Piezoelectric-sensitive mode of lamb wave in one-dimensional piezoelectric phononic crystal plate

We investigate the transmission modes in one-dimensional piezoelectric phononic crystal plate, which is consisted of piezoelectric ceramics placed periodically in epoxy. The influences of piezoelectricity and different electrical boundary conditions on the Lamb waves in the composite plate are studied in detail, and an important elastic wave mode named as piezoelectric-sensitive mode (PSM) is defined. Furthermore, the influences of the piezoelectric constants, the filling fraction and the ratio of thickness to lattice pitch on PSM are given, and the physical mechanism of PSM is also discussed. The numerical results show that PSM has a relatively larger frequency shift and significant change in the displacement distribution when piezoelectricity is considered; the electromechanical coupling coefficient of PSM is much larger than the other modes. It reveals that PSM is an important and useful mode in piezoelectric periodic structures. This investigation is helpful in controlling the band gaps and also gives a potential application in design of sensing system and different piezoelectric devices.     

Flexural wave bandgap properties of phononic crystal beams with interval parameters

Uncertainties are unavoidable in practical engineering, and phononic crystals are no exception. In this paper, the uncertainties are treated as the interval parameters,and an interval phononic crystal beam model is established. A perturbation-based interval finite element method(P-IFEM) and an affine-based interval finite element method(A-IFEM) are proposed to study the dynamic response of this interval phononic crystal beam, based on which an interval vibration transmission analysis can be easi...