含陀螺效应的声表面波波动方程的求解

含陀螺效应的声表面波(SAW)波动方程的求解是分析旋转压电基体SAW传播特性和设计SAW角速度传感器的理论基础.以旋转条件下压电基体声表面波方程的建立和求解为研究内容,推导了含陀螺效应的Christoffel方程的一般表达式,提出了在求解中必须注意对解耦波的判别及进行相应的处理,设计了计算机数值求解的软件,并给出了流程.以新型压电材料硅酸镓镧作为求解的实例,验证了算法的可行性.理论与算法可为与陀螺效应有关的SAW器件的设计提供参考.     

有限弹性体中声表面波波速的分析

声表面波在无限大弹性体中以瑞利波(Rayleigh wave)的形式传播,弹性体中声表面波波速的求解最早也是由Rayleigh从各向同性材料在半无限空间求解开始的.以后的研究工作都沿用半无限空间模型,但在实际工程问题中,声表面波必定是在有限弹性体中传播的.这就要求我们必须研究在有限弹性体中声表面波传播的问题.在声表面波的分析中我们利用Matlab软件进行计算分析.求解了声表面波在带有电极层的各向同性材料弹性体中的波速.此外还推导并求解了各向异性材料弹性体中声表面波的波速方程..     

声表面波陀螺效应的有限元仿真分析

声表面波陀螺主要是依据声表面的陀螺效应的原理进行设计制作的。以YX-128°Li Nb O3压电材料作为基底建立了声表面波器件的有限元分析简化模型进行仿真研究。对仿真模型的X,Y,Z轴分别施加旋转角速率,激活了陀螺效应,从而进一步分析声表面波的频率和旋转角速率在绕不同的旋转轴旋转时的关系。     

基于SAW器件的微间隙压力监测传感器

声表面波SAW(Surface Acoustic Wave)器件能进行无源无线通信,为微间隙等特殊环境下物理量的测量提供了新的解决思路.研究设计了一种基于声表面波延迟线的接触应力传感器.围绕微间隙环境,研究了声表面波器件的结构类型,并确定压力监测的技术方案;根据设计原理,设计一种新型声表面波传感器,并利用有限元分析法对压电基片进行应力仿真;将设计出的传感器进行实验测试并提出温度补偿.通过对声表面波传感器设计的探究,验证了利用声表面波传感器实现微间隙压力监测的可行性.     

ZnO薄膜在传感器方面的最新应用进展

ZnO薄膜是一种新型的、性能优良的半导体材料.本文详细介绍了ZnO薄膜在声光器件、压电器件、气敏元件、声表面波器件、压力元件、湿敏元件和紫外探测器等方面的最新应用进展,并对该材料的发展趋势进行了展望.     

基于声表面波实现数字微流体的产生

数字微流体的产生是压电材料为基片的微流控芯片进行微流分析的前提,报道了在压电基片上应用声表面波技术产生数字微流体的方法.在128°旋转Y切割X传播方向的LiNbO3基片上集成PDMS微通道,在微通道出口一侧为经疏水处理的铝薄片,注射泵产生恒定流量的微流体经PDMS微通道到达铝薄片并聚集,当聚集的微流体体积足够大时,微流体克服表面张力作用下滑到达压电基片,并在中心频率为27.7 MHz叉指换能器激发的声表面波作用下输运,实现微流体的数字化.同时,理论分析了微流体在铝薄片表面上受力状况,并以水为实验对象,进行微流体数字化实验.结果表明,声表面波作用下能精确产生微升量级数字微流体,为压电微流控芯片提供了一种新的微流体引入方法.     

考虑横向剪切和转动惯量效应的多层压电层合壳中波的传播

研究了考虑横向剪切及转动惯量效应影响的正交各向异性压电层合壳中的波传播规律。利用Cooper-Naghdi壳体理论建立了波在压电层合壳中传播方程，通过求解特征值得到并讨论了波在压电层合壳中传播特征曲线，分析丁不同的压电层数和厚度比对特征曲线的影响。该方法可用于不同层数、不同厚度、不同母体材料层的壳体中波传播的研究。     

基于AlN声表面器件的设计与分析

声表面波器件是一种利用压电材料的压电效应与逆压电效应工作电子器件,文章首先详细描述了声表面波器件的设计与仿真过程,运用有限元分析的方法分别计算了利用声表面波的SAW器件与利用体波的BAW器件的性能与各项参数,对相关的器件进行了计算分析,分别用上述方法研究了基于AlN薄膜的声表面波器件和悬臂梁结构的体波器件,推导得出了器件的电学导纳与频率之间的关系,通过分析器件的导纳-频率曲线,推导出器件内部声波的模式以及合适的工作频率,最终得出在IDT周期为8微米的情况下,SAW器件的理想工作频率是0.7～1.95 GHz,BAW器件的理想工作频率在0.6～3.2 GHz的结果.     

石英上准纵漏表面声波在液体传感方面的潜在应用

本文报道了石英材料上一种新的可用于液体传感的准纵漏声表面波模式的传播方向 ,即 Euler角为 [0°,136°,5 0°]的传播方向 ,并对该传播方向上准纵漏声表面波在液体传感方面的应用进行了初步研究 .结果表明 :与目前常用液体声表面波传感器所用声波模式所在传播方向相比较 ,这种新的传播方向上存在较少的声表面波模式 ,当应用于液体传感时只有准纵漏声表面波一种模式存在 .特别是 ,该传播方向上准纵漏声表面波频率温度系数实验测量值为 - 31.13ppm/℃ .这些特性使得本文所提传播方向上准纵漏声表面波具有很好的应用前景 .     

结合金属膜的YZ-LiNbO3压电基片上声表面波陀螺效应分析

在声表面波陀螺效应作用过程中,由于哥氏力的作用比较微弱,导致现有的声表面波陀螺仪的检测灵敏度极低。为了改善哥氏力作用,在声表面波传播路径上分布金属点阵以增加质量负载,将有可能获得良好的灵敏度性能。本文结合研究层状介质中声波传输特性的方法对YZ-LiNbO3压电基片上的金属膜层对陀螺效应的影响做了理论计算。对比分析有无金属膜层的压电基片中陀螺效应的大小,以及不同金属材料对陀螺效应的影响作用,验证了用布置重金属点阵的方法来提高行波模式声表面波陀螺仪检测灵敏度的可行性,从而为高性能行波模式声表面波陀螺仪的研制奠定理论基础。     

水平剪切声板波的激发机理及其特性研究

水平剪切声板波(SH-APM)是在板状固体结构中传播的一种声波,其质点振动垂直于传播方向和界面法线。针对SH-APM的激发机理和激发特性两个方面展开研究。首先通过分析压电介质的Christoffel方程组解耦情况来研究SH-APM的激发机理,推导出为了在压电板上激发出SH-APM,压电基片的材料常数所必须满足的条件;然后在此基础上,建立了SH-APM器件的理论分析模型,并以PZT-5H压电陶瓷为例,研究了SH-APM的激发特性,包括激发模态、传播速度、激发效率、振动位移等;最后,通过实验以及理论计算与相关文献对比,证明了理论模型的正确性及研究结果的有效性。     

High Order Accurate Finite Difference Modeling of Seismo-Acoustic Wave Propagation in a Moving Atmosphere and a Heterogeneous Earth Model Coupled Across a Realistic Topography

We develop a numerical method for simultaneously simulating acoustic waves in a realistic moving atmosphere and seismic waves in a heterogeneous earth model, where the motions are coupled across a realistic topography. We model acoustic wave propagation by solving the linearized Euler equations of compressible fluid mechanics. The seismic waves are modeled by the elastic wave equation in a heterogeneous anisotropic material. The motion is coupled by imposing continuity of normal velocity and normal stresses across the topographic interface. Realistic topography is resolved on a curvilinear grid that follows the interface. The governing equations are discretized using high order accurate finite difference methods that satisfy the principle of summation by parts. We apply the energy method to derive the discrete interface conditions and to show that the coupled discretization is stable. The implementation is verified by numerical experiments, and we demonstrate a simulation of coupled wave propagation in a windy atmosphere and a realistic earth model with non-planar topography.     

薄膜体声波谐振器的FDTD数值分析

提出了基于时域有限差分方法对薄膜体声波谐振器进行数值分析的新方法。利用时域有限差分法理论对压电材料的控制方程,牛顿方程和电学方程在空间和时间进行了离散化,通过得到的差分方程直接得出了声场传播的时域数值解。使用该数值方法对薄膜体声波谐振器的电学特性阻抗进行了分析,并将结果与一维Mason模型的解析解进行了比较验证。     

Investigations on excitation and detection methods for Lamb wave sensors

Due to a high potential sensitivity, Lamb wave acoustic sensors have been studied for biochemical applications. Usually, Lamb waves are generated and detected using piezoelectric transducers. This technology involves bilayers structures and causes some problem of induced strain and temperature compensation. In this paper, we have investigated optical and electrostatic excitation methods. The optical excitation of Lamb waves is studied, and the main limitations of such an excitation method are pointed out. Theoretical as well as experimental studies are reported on electrostatic excitation of Lamb waves, and it is shown that this technique can be suitable for biosensors.     

OPCM AE传感器特性的理论仿真与实验研究

基于均匀场和细观力学理论,对应用于结构损伤声发射(AE)检测的1-1型压电复合材料(OPCM)AE传感器,建立了它的等效力电模型,在此基础上,推出了其等效力、电参数,通过这些参数的对比,发现OPCM具有明显的正交异性的特性;同时,应用有限元仿真计算,得到了在x和z两方向上传感器受到单向应力波荷载作用时,电极面输出的电压存在明显差异;所设计的实验表明:OPCM能够区分出不同方向的应力波,并对特殊方向上的应力波具有强烈的响应,再次证实了OPCM传感器的正交异性特性。     

Numerical solution of potential flow equations with a predictor-corrector finite difference method

We develop a numerical solution algorithm of the nonlinear potential flow equations with the nonlinear free surface boundary condition.A finite difference method with a predictor-corrector method is applied to solve the nonlinear potential flow equations in a two-dimensional (2D) tank.The irregular tank is mapped onto a fixed square domain with rectangular cells through a proper mapping function.A staggered mesh system is adopted in a 2D tank to capture the wave elevation of the transient fluid.The finite difference method with a predictor-corrector scheme is applied to discretize the nonlinear dynamic boundary condition and nonlinear kinematic boundary condition.We present the numerical results of wave elevations from small to large amplitude waves with free oscillation motion,and the numerical solutions of wave elevation with horizontal excited motion.The beating period and the nonlinear phenomenon are very clear.The numerical solutions agree well with the analytical solutions and previously published results.     

A finite element model for the analysis of 3D axisymmetric laminated shells with piezoelectric sensors and actuators: Bending and free vibrations

This paper addresses the bending and free vibrations of multilayered cylindrical shells with piezoelectric properties using a semi-analytical axisymmetric shell finite element model with piezoelectric layers using the 3D linear elasticity theory. In the present 3D axisymmetric model, the equations of motion are expressed by expanding the displacement field using Fourier series in the circumferential direction. Thus, the 3D elasticity equations of motion are reduced to 2D equations involving circumferential harmonics. In the finite element formulation the dependent variables, electric potential and loading are expanded in truncated Fourier series. Special emphasis is given to the coupling between symmetric and anti-symmetric terms for laminated materials with piezoelectric rings. Numerical results obtained with the present model are found to be in good agreement with other finite element solutions.     

Active noise control of flexible linkage mechanism with piezoelectric actuators

An active noise control method for flexible linkage mechanism systems with piezoelectric actuators and strain gauge sensors is studied. By employing a set of wave number transformations on the original equations of motion of the flexible linkage mechanisms, a new set of equations of motion is obtained, in which the unknown variables can describe the structural acoustic radiation level of the mechanism system directly. On the basis of the new equations, the active noise control of the flexible linkage mechanism system with piezoelectric actuators is discussed. Firstly, the optimal control forces are determined based on the optimal control theory. Secondly, the controller of the system that consists of the output feedback and the disturbance feed-forward control laws is presented. Simulations show that the method presented in this paper is valid.     

Numerical simulation of piezoelectrically agitated surface acoustic waves on microfluidic biochips

Microfluidic biochips are biochemical laboratories on the microscale that are used for genotyping and sequencing in genomics, protein profiling in proteomics, and cytometry in cell analysis. There are basically two classes of such biochips: active devices, where the solute transport on a network of channels on the chip surface is realized by external forces, and passive chips, where this is done using a specific design of the geometry of the channel network. Among the active biochips, current interest focuses on devices whose operational principle is based on piezoelectrically driven surface acoustic waves (SAWs) generated by interdigital transducers placed on the chip surface. In this paper, we are concerned with the numerical simulation of such piezoelectrically agitated SAWs relying on a mathematical model that describes the coupling of the underlying piezoelectric and elastomechanical phenomena. Since the interdigital transducers usually operate at a fixed frequency, we focus on the time-harmonic case. Its variational formulation gives rise to a generalized saddle point problem for which a Fredholm alternative is shown to hold true. The discretization of the time-harmonic surface acoustic wave equations is taken care of by continuous, piecewise polynomial finite elements with respect to a nested hierarchy of simplicial triangulations of the computational domain. The resulting algebraic saddle point problems are solved by blockdiagonally preconditioned iterative solvers with preconditioners of BPX-type. Numerical results are given both for a test problem documenting the performance of the iterative solution process and for a realistic SAW device illustrating the properties of SAW propagation on piezoelectric materials. The first two authors have been supported by the DFG within the Collaborative Research Center SFB 438. The seond author acknowledges further support by the NSF under Grant No. DMS-0411403, Grant No. DMS-0412267 and Grant-No. DMS-0511611.