用于微电池的压电悬臂梁电特性仿真

研究了一种带质量块的压电悬臂梁结构,利用压电薄膜的正压电效应将机械能转化成电能,可以用于振动能的收集。利用有限元分析软件ANSYS对结构进行建模,通过模态分析和谐波分析得到：悬臂梁在一阶模态时上下振动,形成恰当的工作状态;通过改变梁的各个几何参数和振动源的频率,得到了悬臂梁上下电极间峰值电压的变化情况;当振动源的频率为悬臂梁的一阶共振频率时,得到的峰值电压最大。     

新型智能隔振复合结构的动态特性研究

针对精密机械的微位移隔振问题,设计了一种以PVDF压电薄膜为作动器和传感器的新型智能隔振复合结构。根据压电方程推导出了层叠式PVDF压电薄膜作动器厚度变形量表达式,建立了该智能复合结构的隔振理论模型,采用LMS自适应控制算法,以Matlab和有限元混合建模分析方式对本智能隔振复合结构的动态特性进行研究。有限元模型的分析结果与Matlab计算数据一致,验证了本新型智能隔振复合结构对微位移隔振的有效性,其结论将为精密仪器、微纳米设备的微位移智能主动隔振奠定理论基础。     

电压激励的压电层合悬臂梁横向振动分析

以压电陶瓷-金属-压电陶瓷对称层合结构为研究对象,基于能量法得到了等截面压电层合对称悬臂梁在横向激振电压下的强迫振动微分方程。用ANSYS软件对建立的相关有限元模型进行模态分析、谐响应分析及瞬态动力学分析,仿真结果与理论值基本吻合,验证了理论的正确性。进一步分析了阻尼对横向位移响应的影响,讨论了速度、加速度随时间的变化规律,分析了压电悬臂梁的最大应力出现位置及最大应力值随时间的关系。所得结论可为压电振子的设计和分析提供必要理论参考。     

压电智能结构冲击荷载谱的反演方法

基于对智能层合板结构的模态分析，提出由结构的压电模态响应反演瞬态荷载时间历程的有限元方法。介绍了压电模态传感器的实现原理，并给出了由实测压电单元输出得到结构模态响应的计算公式。采用无条件稳定的精细逐步积分法求解结构的模态动力学微分方程，构造了通过结构的模态响应直接反求荷载列阵的迭代算法。该方法迭代过程简单可靠、计算速度快、识别精度高，适用于任意形状和边界条件的复杂智能结构。实例表明了该方法的可行性。     

仿蟋蟀尾毛的MEMS振动传感器 有限元仿真分析

基于MEMS技术和仿生学设计了一种纤毛+薄膜振动传感器敏感结构,由垂直纤毛和两个相互垂直的悬臂梁构成信息接收和传递单元,沉积在与悬臂梁末端固连的硅衬底薄膜上的PZT压电薄膜作为敏感转化单元.建立了该传感器结构的等效运动模型,在此基础上对传感器的输出特性和频率特性进行了数学分析.利用ANSYS有限元软件对不同结构及几何参数的敏感结构进行了仿真分析,对比仿真结果,优化传感器的结构和几何参数.仿真结果表明该结构传感器共振频率达到了6 757.4 Hz.     

硅基反铁电薄膜微悬臂梁力学仿真分析

采用双层微悬臂梁理论模型,对基于反铁电薄膜微悬臂梁驱动构件的力学行为进行分析研究.以反铁电薄膜材料体积应变=ε0.8%为设定量,实现硅基反铁电薄膜微悬臂梁结构的应变-应力载荷转化,运用AN SY S11.0对基于反铁电薄膜应变效应的硅基微悬臂梁结构进行了静态分析、模态分析和谐响应分析,通过对此微驱动结构的优化设计、仿真,得出了不同几何参数硅基微悬臂梁构件的挠度和谐振频率.从而无需进行大量的工艺流片,为大量程的微悬臂梁驱动构件的设计加工提供指导意义.     

部分主动约束阻尼梁振动的假设模态法建模

摘 要:基于夹层结构的Mead-Markus基于假设使用假设模态法对部分主动约束阻尼覆盖的梁结构进行建模计算,并与有限元结果进行比较。重点研究压电层厚度、阻尼层厚度、ACLD长度和位置对模态损耗因子的影响,研究表明,适当增加压电层厚度,减小阻尼层厚度,增加ACLD长度有利于增强阻尼效果。     

L型压电振动能量采集器的有限元分析与特性仿真

单频悬臂梁式压电振动能量采集器存在工作频带窄、采集转换效率低等问题。通过在单频悬臂梁式压电振动能量采集器的水平悬臂梁末端增加一垂直悬臂梁,构造了一种L型宽频压电振动能量采集器;运用有限元法建立L型振动能量采集器的有限元分析模型,仿真分析了L型振动能量采集器的结构参数对其前两阶模态频率的影响,得到了结构最优尺寸。利用Hamilton原理建立了L型能量采集器的机电耦合分析模型,对其振动特性和电输出特性进行了数值仿真,结果表明L型结构能够提高能量采集器的工作频带和采集效率。     

基于等几何方法的压电功能梯度板动力学及主动振动控制分析

针对表面粘贴有压电层的功能梯度板的动力学及主动振动控制问题，建立了一种基于三阶剪切变形理论的等几何分析求解方法。其中，功能梯度板的材料属性为板厚方向的幂函数分布，并假设电势沿着压电层的厚度方向呈线性变化。利用线性压电本构方程以及哈密顿变分原理，推导了压电功能梯度板的相关等几何分析有限元方程。通过分析压电智能结构的静态弯曲行为验证了该方法的有效性与精确性。运用模态叠加技术与Newmark-β直接积分法分析了两种不同结构的压电功能梯度板的动力学响应与主动振动控制问题。在主动振动控制分析中，引入了物理中面的概念避免当传感器与驱动器分别粘贴于功能梯度的上、下表面时，由拉伸-耦合效应引起的控制不稳定的问题，并着重分析了振动控制过程中两种结构传感器层和驱动器层的电压响应。     

硅基PZT压电薄膜微开关的设计和制作

对硅基锆钛酸铅（PZT）压电薄膜微开关进行了结构和版图设计，根据MEMS加工工艺和标准硅基IC工艺的特点，获得了硅基PZT压电薄膜微悬臂梁结构系统工艺流程中的关键工艺技术和典型工艺条件，对多孔硅的选择性生长进行了较为详细的实验研究，最后成功的制备出硅基PZT压电薄膜微开关样品，这对集成化芯片系统的进一步发展打下了必要的良好的实验基础。     

基于COMSOL的声表面波器件仿真

声表面波器件在通信、传感、射频识别等领域有着广泛的应用.以有限元方法为基础,利用有限元软件COMSOL对声表面波器件进行了仿真.从器件的模型建立入手,按由浅入深的顺序对无电极压电基片、压电基片表面沉积叉指换能器、叉指换能器表面溅射薄膜、薄膜上负载液体的4种结构进行了仿真分析.仿真研究表明:叉指换能器的电极效应会产生正、反特征频率,并且两种频率都随着叉指电极的敷金比与高度增加而向低频偏移;薄膜厚度的增加同样会导致器件频率向低频变化;当器件负载液体用于液体密度检测时,可通过器件频率变化对液体密度的灵敏程度来对薄膜厚度进行优化.其研究结果可以为声表面波器件的设计制作提供依据.     

Simple Efficient Smart Finite Elements for the Analysis of Smart Composite Beams

This paper is concerned with the development of new simple 4-noded locking-alleviated smart finite elements for modeling the smart composite beams. The exact solutions for the static responses of the overall smart composite beams are also derived for authenticating the new smart finite elements. The overall smart composite beam is composed of a laminated substrate conventional composite beam, and a piezoelectric layer attached at the top surface of the substrate beam. The piezoelectric layer acts as the actuator layer of the smart beam. Alternate finite element models of the beams, based on an “equivalent single layer high order shear deformation theory”, and a “layer-wise high order shear deformation theory”, are also derived for the purpose of investigating the required number of elements across the thickness of the overall smart composite beams. Several cross-ply substrate beams are considered for presenting the results. The responses computed by the present new “smart finite element model” excellently match with those obtained by the exact solutions. The new smart finite elements developed here reveal that the development of finite element models of smart composite beams does not require the use of conventional first order or high order or layer-wise shear deformation theories of beams. Instead, the use of the presently developed locking-free 4-node elements based on conventional linear piezo-elasticity is sufficient.     

An advanced finite element formulation for piezoelectric beam structures

Since many piezoelectric components are thin rod-like structures, a piezoelectric finite beam element can be utilized to analyse a wide range of piezoelectric devices effectively. The mechanical strains and the electric field are coupled by the constitutive relations. Finite element formulations using lower order functions to interpolate mechanical and electrical fields lead to unbalances within the numerical approximation. As a consequence incorrect computational results occur, especially for bending dominated problems. The present contribution proposes a concept to avoid these errors. Therefore, a mixed multi-field variational approach is introduced. The element employs the Timoshenko beam theory and considers strains throughout the width and the thickness enabling to directly use 3D constitutive relations. By means of several numerical examples it is shown that the element formulation allows to analyse piezoelectric beam structures for all typical load cases without parasitically affected results.     

基于有限元法的周期压电智能梁滤波特性分析

周期结构具有通频和禁频特性,使其在动态载荷的滤波器、具有主动控制功能的结构研究中得到了重要应用。基于Timoshenko梁理论,考虑基梁和压电片的转动惯量和剪切效应,采用有限元法和传递矩阵法推导了波在周期性地粘贴压电片的Timoshenko梁中的传播模型,分析了几何尺寸和材料特性对其频带性质的影响,并与Bernoulli-Euler梁理论得到的结果进行了对比。研究表明,当基梁与压电层厚度比达到40时,禁带带宽减小了54%,因此对于周期结构中的深梁,应舍弃Bernoulli-Euler梁理论而采用Timoshenko梁理论建立的模型;对于不同尺寸和材料特性的压电周期结构,频带性质会有很大不同,可以通过调整结构的参数来改变其频带性质,从而改变波动在结构中的传播特性。     

自感知压电层合梁的数值分析与数值模拟

从压电本构方程出发,借助Hamilton原理建立了压电层合结构的有限元方程,基于此理论,对一五层的压电梁运用ANSYS参数化设计语言(APDL)建模,采用二维四结点四边形耦合单元,分析了梁与压电层的几何参数对传感与致动性能的影响,比较了不同边界条件下梁的变形变化。得出的一些有效结论,对多层智能结构的设计具有一定的参考价值。     

节瘤缺陷对薄膜热力损伤的有限元分析

在多层介质薄膜中,节瘤缺陷是影响薄膜激光损伤的关键因素。为了理解节瘤缺陷对薄膜激光损伤的影响,以热传导理论为依据,通过有限元方法模拟了多层介质薄膜中的节瘤缺陷在激光辐照下的热力响应,分析了节瘤缺陷的大小和深度对热力响应的灵敏度。发现大而浅的节瘤缺陷有较高的热力响应灵敏度,因此,消除直径较大的膜层表面附近的缺陷有助于提高薄膜抗激光损伤的能力。     

Measurement of fracture toughness by nanoindentation methods: Recent advances and future challenges

In this paper, we describe recent advances and developments for the measurement of fracture toughness at small scales by the use of nanoindentation-based methods including techniques based on micro-cantilever, beam bending and micro-pillar splitting. A critical comparison of the techniques is made by testing a selected group of bulk and thin film materials. For pillar splitting, cohesive zone finite element simulations are used to validate a simple relationship between the critical load at failure, the pillar radius, and the fracture toughness for a range of material properties and coating/substrate combinations. The minimum pillar diameter required for nucleation and growth of a crack during indentation is also estimated. An analysis of pillar splitting for a film on a dissimilar substrate material shows that the critical load for splitting is relatively insensitive to the substrate compliance for a large range of material properties. Experimental results from a selected group of materials show good agreement between single cantilever and pillar splitting methods, while a discrepancy of ∼25% is found between the pillar splitting technique and double-cantilever testing. It is concluded that both the micro-cantilever and pillar splitting techniques are valuable methods for micro-scale assessment of fracture toughness of brittle ceramics, provided the underlying assumptions can be validated. Although the pillar splitting method has some advantages because of the simplicity of sample preparation and testing, it is not applicable to most metals because their higher toughness prevents splitting, and in this case, micro-cantilever bend testing is preferred.     

Elastic bending analysis of bilayered beams containing a gradient layer by an alternative two-variable method

Aifantis’s strain gradient elasticity theories and Zhang’s two-variable method are used to study elastic bending problems of bilayered micro-cantilever beams, containing a gradient layer, subjected to a transverse concentrated load. The differential element method is used to obtain differential governing equations. The variational method is employed to overcome the difficulty in deriving nonlocal natural boundary conditions, which could not be automatically fulfilled in gradient theories, not like that in classical theories. Then the differential governing equations subjected to the related boundary conditions are solved analytically to obtain the deformation field, which could be degenerated to that in classical elasticity theories. The gradient parameters of epoxy polymeric resin and copper single crystals in the present model are provided by fitting Lam’s and Demir’s experiments. The influences of length and layer thickness on normalized deflection and effective rigidity are discussed in a representative case of a Cu/epoxy polymeric resin beam. Results show that size effect makes the effective rigidity vary more prominently with shorter beam length or larger layer thickness. For given materials, although size effect exists, classical elasticity theories are still valid in some particular combination of three geometric parameters: beam length, upper and lower layer thicknesses.     

Simulation of the creep damage behavior of thin film/substrate systems by bending creep tests

The purpose of this paper is to understand the creep damage properties of thin film/substrate systems by bending creep tests. To this aim, a numerical study has been performed on the creep damage development of the thin film/substrate systems by implementing the Kachanov–Rabothov damage law into finite element models. The work may shed some light on the influence of the modulus ratio of the substrate to the thin film, the thickness of the thin film and the bending load. Finite element method (FEM) results show that three obviously damaged zones are found. The first is at the edge of the loading pin, the second is at the interface between the film and the substrate ahead of the loading pin edge, the last is at the edge of the supporting pin A. The influence of the modulus ratio of the substrate to the thin film on the bending creep damage is not obvious at the preliminary stage of creep time. However, with the lapse of time, the damage rate decreases with the increase of modulus ratio of the substrate to the thin film. The change of the thickness of the thin film and the bending load also influence the creep damage behavior of the thin film/substrate systems.     

Flexural vibration behavior of piezoelectric heterogeneous bimorph beams

Bending oscillations of piezoelectric bimorph beams are effective sound sources in gases or fluids, and, therefore, of practical interest. On the basis of the piezoelectric constitutive relations and the elastodynamic equations, the differential equation of flexural vibrations of thin rectangular piezoelectric heterogeneous bimorph beams, consisting of a piezoelectric layer glued onto an elastic substrate, is derived. The piezoelectric layer is polarized in thickness direction and can be excited to thickness vibrations by an electric alternating current voltage applied to electrodes covering the upper and lower surface of the layer. This causes an oscillating transverse contraction in the piezoelectric layer but not in the substrate, and, thus, generates flexural vibrations of the beam. The differential equation is solved analytically for beams of finite length with both ends free, one clamped and one free end, as well as for both ends clamped. Their vibration behavior in viscous fluids is considered. For a piezo-ceramic composite layer joined to a steel plate vibrating in air and in water, the analytical results are evaluated numerically as function of frequency