矩形智能板弯曲形状的主动控制

研究具有离散分布压电控制器的矩形智能板,在外加电场作用下的弯曲形状与压电元件外加控制电压之间的关系,建立了对智能矩形板的弯曲形状进行主动控制的方法,得到各离散分布压电元件控制电压的解析解,并给出了算例     

压电智能环形板的主动控制

对在不同位置粘有任意多组压电传感器和压电执行器的轴对称弹性环形薄板的振动控制进行了研究．根据压电执行元件的等效作用量得到了压电智能环板的振动控制方程和传感方程,再利用分离变量法以及由传感器测得的电量和作用在执行器上电压之间的控制模式得到振动方程的全解．实行了对整体结构的主动控制．对不同的压电片布置进行了数值计算．结果表明：当离散分布压电元件布置越密,振动衰减的效果越佳     

DAP增强梁结构形状控制的机理研究

对称粘贴在梁结构上下表面上的压电元件在外部电场的作用下能使梁结构发生弯曲变形，通过分析驱动构件与结构中的应变分布，采用定向固定的压电元件(DAP，即directional attached piezoelectric)来代替传统的压电元件(CAP，即conventional attached piezoelectric)，减小了驱动构件的横向效应，提高了压电驱动的效率，并进行了实验对比验证。     

压电复合材料梁和板的变形控制问题

由于具有良好的结构、力学性能,复合材料层合板在现代飞行器上大量应用;而压电复合材料,作为一种新兴的智能材料,由于其独特的力电耦合性能得到了人们更多的关注。本文研究含有压电片的复合材料梁和板在电场作用下的变形控制问题。基于经典的梁理论和层合板理论,分别研究了下列问题:(1)双压电片布置的悬臂梁的变形;(2)含有压电层的层合板变形控制问题;(3)含有一对压电片的层合板的变形控制问题。针对上述问题,分别给出了理论解和数值解,并进行了相关讨论分析。结果表明压电材料可对结构进行精确控制,因此本文的结果可对复合材料梁和板在电场作用下的变形控制问题提供工程参考。     

主动约束阻尼板压电层电压拓扑优化研究

建立主动约束层阻尼板有限元模型,以结构模态阻尼比最大化为目标函数,压电层总电能消耗为约束条件,压电层单元控制电压为设计变量,对主动约束层阻尼板压电层电压进行了拓扑优化,获得了压电层电压最优拓扑分布。通过引入虚拟设计变量,将压电层电压控制不连续问题转化为连续问题。考虑实际工程应用的需要,采用指数函数对电压中间变量进行惩罚。在灵敏度分析基础上,采用移动渐进线(MMA)法,求解了主动约束层阻尼板电压拓扑优化问题。数值算例证实了电压拓扑优化模型以及数值求解方法的有效性。     

Lamb波理论及层合板冲击损伤的实验研究

从理论上分析了板中Lamb波信号的传播特性,并给出Lamb波在板中传播的频散方程。理论分析及实验均表明,Lamb波的频散特性与复合材料结构损伤有着直接的联系,而且最低阶的对称和反对称Lamb波模态对层合板的损伤比较敏感,但应用Lamb波的频散效应监测结构的损伤在检测技术上还难以实现。根据板中导波形成Lamb波的共振原理,板中应力波的幅频特性很大程度上反映了Lamb波的谐振特征。因此,利用压电元件的压电阻抗谱分析应力波的各阶模态频率及振幅对结构损伤的变化,能够反映材料内部损伤与Lamb波的频散特性。文中针对表面粘贴压电元件的层合板智能结构,建立了包含Lamb波谐振模式的压电阻抗计算模型。冲击损伤试件的实验表明,由于结构损伤的出现压电阻抗谱中的模态频率及其阻抗幅值等特征信息将发生变化。因此,引入应力波损伤因子可以对结构冲击损伤的存在和程度进行初步评价。该方法基于结构的机-电动态阻抗特性,不受结构的几何形状限制,测试用的压电元件成本低,方法简单可行,有望在智能结构的健康诊断方面获得应用。     

基于MFC的结构静态形状控制研究

宏纤维复合材料MFC(Macro Fiber Composite)具有体积小、主动控制适用性强、作动效果好等特点。本文开展了宏纤维复合材料MFC对结构静态形状主动控制研究。建立了悬臂梁结构有限元模型,并采用载荷比拟法计算得到了MFC压电作动器的驱动载荷。基于数值分析结果,搭建了悬臂梁结构主动控制实验平台,分析了不同加载电压下的悬臂梁的弯曲变形效果,进而分析MFC结构在静态形状控制中的力学性能。数值仿真和实验结果表明:在不同的静态电压加载下,结构的变形和加载电压近似呈线性关系;仿真和实验结果对比中呈现出较好的一致性,其最大位移误差为12.45%。最后讨论了MFC压电作动器自身时间蠕变特性对静态变形控制实验结果产生的影响,结果表明在大电压作用下MFC材料存在蠕变效应,在实际使用过程中需要关注。本文采用以悬臂梁为载体的实验和仿真研究方法对在其他横观各向同性材料的压电材料力学性能分析具有普遍适用性。     

智能柔性悬臂梁的动力学建模研究

对带有压电陶瓷作动器和传感器的平面智能柔性梁进行了有限元动力学建模。采用Euler-Bernoulli梁模型,在考虑平面梁压电效应的基础上,考虑了大变形和非线性变形,进行了有限元离散;基于Lagrange方程建立了带压电元件的智能柔性悬臂梁的电-结构耦合动力学有限元精确模型,并将本文模型和一般不考虑压电元件质量和电势能模型的仿真结果进行了对比,结果表明:两种模型得到的一阶固有频率最大相差31.8%,响应振幅也有较大的差异。因此,在工程动力学建模中,不能忽略压电元件的质量和电势能。本文所建立的电-结构耦合动力学模型能更加精确地反映实际应用中智能柔性悬臂梁的动力学特性。     

湿度对骨内压电信号的影响

对不同相对湿度下的骨压电电压和压电电荷信号进行测量研究,来考察湿度对骨压电信号的影响.采用三点弯曲干骨试样,以梯形脉冲载荷的方式进行加载,分别应用超高输入阻抗的生物信号放大器和电荷放大器测量了三种不同相对湿度下的骨压电电压和压电电荷信号波形.结果表明,骨压电电压峰值随湿度的增加而下降很快,当湿度从30%增至60%时,电压降幅达到了80%左右;基于测试原理的不同,骨压电电荷也随湿度的增加而下降,其降幅较小.由此可以推断,骨在体内湿润的状态下,受力变形时压电电压幅值可能趋于零.电荷的产生和瞬时泄放有可能是骨在体内的动态载荷作用下的压电效应的表现形式.     

压电弹性层合板静力机电耦合特性的解析解

应用经典板壳理论和压电理论对层合板结构进行简化.对四边简支压电层合板在不同电学边界条件下,包括四边电学开路和电学短路,上下表面受外加电压及无外加电压作用,进行分析,求得了电势和挠度的解析表达式.给出了压电层和基体的挠度、电势分布图.     

Postbuckling of FGM plates with piezoelectric actuators under thermo-electro-mechanical loadings

A postbuckling analysis is presented for a simply supported, shear deformable functionally graded plate with piezoelectric actuators subjected to the combined action of mechanical, electrical and thermal loads. The temperature field considered is assumed to be of uniform distribution over the plate surface and through the plate thickness and the electric field considered only has non-zero-valued component E_Z. The material properties of functionally graded materials (FGMs) are assumed to be graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents, and the material properties of both FGM and piezoelectric layers are assumed to be temperature-dependent. The governing equations are based on a higher order shear deformation plate theory that includes thermo-piezoelectric effects. The initial geometric imperfection of the plate is taken into account. Two cases of the in-plane boundary conditions are considered. A two step perturbation technique is employed to determine buckling loads and postbuckling equilibrium paths. The numerical illustrations concern the postbuckling behavior of perfect and imperfect, geometrically mid-plane symmetric FGM plates with fully covered or embedded piezoelectric actuators under different sets of thermal and electric loading conditions. The effects played by temperature rise, volume fraction distribution, applied voltage, the character of in-plane boundary conditions, as well as initial geometric imperfections are studied.     

FINITE ELEMENT MODELING AND ROBUST VIBRATION CONTROL OF TWO-HINGED PLATE USING BONDED PIEZOELECTRIC SENSORS AND ACTUATORS

Active vibration control for a kind of two-hinged plate is developed in this paper. A finite element model for the hinged plate integrated with distributed piezoelectric sensors and actuators is derived, including bending and torsional modes of vibration. In this model, the hinges are simplified as regular plate elements to facilitate operation. The state space representations for bending and torsional vibrations are obtained. Based on two low-order models of the bending and torsional motion, two H ∞ robust controllers are designed for suppressing the vibrations of the bending and torsional modes, respectively. The simulation results indicate the effectiveness and feasibility of the designed H ∞ controllers. The vibration magnitudes of the low-order modes can be reduced without affecting the high frequency modes.     

压电弹性层合板静力机耦合特性的解析解

应用经典权壳理论和压电理论对层合板结构进行简化。对四边简支压电层合板在不同电学边界条件下,包括四边电学开路和电学短路。上下表面受外电压及无外加电压作用,进行分析,求得了电势和挠度的解析表达式,给出了压电层和基体的挠度、电势分布图。     

Analytical solution for the cylindrical bending vibration of piezoelectric composite plates

An analytical solution for the cylindrical bending vibrations of linear piezoelectric laminated plates is obtained by extending the Stroh formalism to the generalized plane strain vibrations of piezoelectric materials. The laminated plate consists of homogeneous elastic or piezoelectric laminae of arbitrary thickness and width. Fourier basis functions for the mechanical displacements and electric potential that identically satisfy the equations of motion and the charge equation of electrostatics are used to solve boundary value problems via the superposition principle. The coefficients in the infinite series solution are determined from the boundary conditions at the edges and continuity conditions at the interfaces between laminae, which are satisfied in the sense of Fourier series. The formulation admits different boundary conditions at the edges of the laminated piezoelectric composite plate. Results for laminated elastic plates with either distributed or segmented piezoelectric actuators are presented for different sets of boundary conditions at the edges.     

Control of mechanical deformation of a laminate by piezoelectric actuator taking into account the transverse shear

Summary The control of dynamic deformation of a laminate plate is conducted by applying electrical load to a piezoelectric actuator integrated into the laminate. The dynamic behavior of the laminate is analyzed in the paper taking into account the effect of transverse shear. The analytical model of the laminate is composed of fiber-reinforced laminae and piezoelectric layers constituting a symmetric cross-ply laminate rectangular plate with simply-supported egdes. It is subjected to mechanical and electrical loads acting on the piezoelectric actuator in order to compensate the effect of the mechanical loads. The behavior of the laminate is analyzed based on the first-order shear deformation theory. Closed-form solutions are obtained for the following quantities: (1) natural frequencies of the laminate plate, (2) weight functions for the deflections and rotations and (3) transient deflections due to loads varying arbitrarily with time. Illustrative examples are shown for the control of deflections caused by the mechanical loads by means of electrical voltage applied to the piezoelectric actuators.     

含压电材料智能结构动态特性的研究

本文推导了含压电材料智能结构有限元动力方程,讨论了智能结构系统的动态特性,得到了模态形状和相应的模态电压以及考察了具有分布的压电传感器和执行器的四边简支方板的各阶固有频率随以馈增益的变化规律,这些结果将在智能结构控制的优化设计中起到了很大的作用。     

Exact solutions for magneto-electro-elastic laminates in cylindrical bending

Analytical solutions are derived for the cylindrical bending of multilayered, linear, and anisotropic magneto-electro-elastic plates under simple-supported edge conditions. We construct the general solution in terms of a simple formalism for any homogeneous layer, from which any physical quantities can be solved for the given boundary conditions. For multilayered plates, we derive the solution in terms of the propagator matrices. A special feature of cylindrical bending, which distinguishes itself from the three-dimensional plate problem, is that the associated eigenvalues for any homogeneous layer are independent of the sinusoidal mode, and thus need to be solved only once. Typical numerical examples are also presented for a piezomagnetic plate, a two-layered piezoelectric/piezomagnetic plate, and a four layered piezoelectric/piezomagnetic plate, with different span-to-thickness ratios. In particular, the piezoelectric and piezomagnetic fields show certain interesting features, which give guidance on the development of piezoelectric/piezomagnetic thin-plate theories. Furthermore, it is shown that the variations of the elastic, electric, and magnetic quantities with thickness depend strongly upon the material property and layering, which could be useful in the analysis and design of smart composite structures with sensors/actuators.     

考虑挠曲电效应的压电纳米薄板力-电-热耦合特性研究

摘要：挠曲电效应是由应变梯度引起的，与尺度相关的力电耦合效应。基于Kirchhoff板假设和挠曲电理论，本文推导了温度和电压作用下的压电薄板力-电-热耦合微分控制方程，定量分析了微分控制方程中非线性项的影响，并针对四周固支压电薄板采用Ritz法求解，数值计算了压电薄板的弯曲和振动行为。在研究温度和挠曲电效应对薄板耦合特性和力学行为的影响时，本文分别考虑了材料系数不随温度变化和随温度线性变化两种情况。以PZT-5H为例，我们讨论了挠曲电和温度对压电薄板的横向位移和固有频率的影响。研究结果表明挠曲电效应对压电纳米薄板的力学行为影响很大，且具有明显的尺寸效应。此外，薄板对温度变化非常敏感。因此，可通过挠曲电效应和温度来调控压电纳米薄板的多场耦合特性和力学行为，进而优化基于压电薄板的NEMS/MEMS中传感器、作动器等电子器件的性能。