基于小波理论的悬臂板压电动力控制模式

采用Daubechies小波理论的尺度函数变换，建立了由压电片感应器（sensors）的观测电量识别悬臂板结构变形的一一对应显式关系，从而克服了传统模态方法因逆矩阵求解在某些情形下得不到保证而导致观测失效的不足．随后基于小波尺度函数变换，对于悬臂板建立了具有位移与速度信号反馈的压电致动控制动力模式．由于小波尺度函数逼近具有自动滤除高频分量的能力，建立的控制模式将不会出现由观测溢出与控制溢出耦会造成的不稳定性．数值结果表明：控制方法在抑制外界干扰方面要快于传统方法．     

Hertzian Contact of Anisotropic Piezoelectric Bodies

The Fourier transform method is applied to the Hertzian contact problem for anisotropic piezoelectric bodies. Using the principle of linear superposition, the resulting transformed (algebraic) equations, whose right-hand sides contain both pressure and electric displacement terms, can be solved by superposing the solutions of two sets of algebraic equations, one containing pressure and another containing electric displacement. By presupposing the forms of the pressure and electric displacement distribution over the contact area, the problem is solved successfully; then the generalized displacements, stresses and strains are expressed by contour integrals. Details are presented in the case of special orthotropic piezoelectricity whose material constants satisfy six relations, which can be easily degenerated to the case of transverse isotropic piezoelectricity. It can be shown that the result gained in this paper is of a universal and compact form for a general material.Supported by the National Natural Science Foundation of China (No.10372003).     

Magnetic and electric poling effects associated with crack growth in BaTiO3–CoFe2O4 composite

Magnetoelectroelastic composite possesses the dual feature that the application of magnetic field induces electric polarization and electric field induces magnetization. The poling directions introduced magnetically and electrically can be different in addition to those for the applied magnetic and electric field. Their choices can influence the character of crack growth which could be enhanced or retarded. The details of how the directions of poling and applied field would affect crack initiation and growth are discussed in relation to the volume fraction of inclusions for a BaTiO₃–CoFe₂O₄ two phase composite. The multi-functional aspects of magnetoelectroelastic materials are involved since they entail multi-scaling features. Failure criteria that applies to isotropic elastic materials may not hold for composites exhibiting piezomagnetic and piezoelectric properties. For instance, a negative energy release rate has been obtained for cracks in piezoelectric materials.In view of what has been said with reference to the energy release rate approach, it is desirable to use the strain energy density function as a failure criterion, even if it is only for its positive definiteness character. Physically speaking, it is attractive to have a function that could rank the proportion of energy related to volume and shape change. They determine the proportion of the hard and soft phase of the composite and hence the volume fraction of the constituent. Strength and toughness parameters used for ranking isotropic and homogeneous materials will not apply for anisotropic and/or nonhomogeneous materials if these microstructure effects could not be suppressed to a lower scale and represented as an average at the macroscopic scale. Too much emphases cannot be placed on the need to clarify the multi-scaling aspects of piezoelectric and piezomagnetic materials. Their behavior as affected by the presence of crack-like defects should be understood prior to deciding whether the material characterization approach would be suitable. That is whether simplicity could justify at the expense of conceptual rigor. Much of this would depend on scaling the time and size related to loading and material structure interaction. The magnetoelectroelastic crack model selected in the work to follow perhaps will provide an insight into the complexicity of the state of affairs for treating the finer details of material behavior with rigor.The proposed test model shows that crack growth in the magnetoelectroelastic materials can be suppressed by increasing the magnitude of the piezomagnetic constants in relation to those for piezoelectricity. A more rational means of evaluating the resistance of materials against fracture is thus proposed, particularly when anisotropy and inhomogeneity might be present.     

具损伤压电智能层合中厚板的非线性动力稳定性分析

基于各向异性损伤理论和压电理论，采用能量法和Lagrange方程，建立了具损伤压电智能层合中厚板在参数激励下的非线性运动控制方程，应用增量谐波平衡法，求解了具损伤压电智能层合中厚板的非线性动力稳定性问题。算例中，分析了损伤参数和压电效应对压电智能层合板非线性动力稳定性的影响，揭示了力电耦合效应的内在特征，并与有关文献的结果进行了比较。     

电流变液与压电陶瓷复合的自耦合阻尼器

基于智能结构的思想,率先提出设计制作电流变液和压电陶瓷复合的自耦合阻尼器．相比于通常的电流变液阻尼器,该自耦合阻尼器采用压电陶瓷响应外界振动而输出高电压,激励电流变液体工作,从而省去了外加高压电源．随外作用力变化,激励电流变液的压电陶瓷电压自动改变,阻尼器具有自适应的特征,省去了通常的计算机等控制系统．研制的第1代电流变液／压电陶瓷阻尼器实现了自适应的控制过程,显示了良好的减振性能．在第2代产品中采用了新的设计,提高了阻尼器的结构稳定性和可靠性,使阻尼器整体性能得到提高．     

Exact electroelastic analysis of functionally graded piezoelectric shells

A paper focuses on implementation of the sampling surfaces (SaS) method for the three-dimensional (3D) exact solutions for functionally graded (FG) piezoelectric laminated shells. According to this method, we introduce inside the nth layer I_n not equally spaced SaS parallel to the middle surface of the shell and choose displacements and electric potentials of these surfaces as basic shell variables. Such choice of unknowns yields, first, a very compact form of governing equations of the FG piezoelectric shell formulation and, second, allows the use of strain–displacement equations, which exactly represent rigid-body motions of the shell in any convected curvilinear coordinate system. It is worth noting that the SaS are located inside each layer at Chebyshev polynomial nodes that leads to a uniform convergence of the SaS method. As a result, the SaS method can be applied efficiently to 3D exact solutions of electroelasticity for FG piezoelectric cross-ply and angle-ply shells with a specified accuracy by using a sufficient number of SaS.     

Nonlinear characteristics of circular-cylinder piezoelectric power harvester near resonance based on flow-induced flexural vibration mode

The nonlinear behaviors of a circular-cylinder piezoelectric power harvester （CCPPH） near resonance are analyzed based on the flow-induced flexural vibration mode. The geometrically-nonlinear effect of the cylinder is studied with considering the in-plane extension incidental to the large defection. The boundary electric charges generated from two deformation modes, flexure and in-plane extension, were distinguished with each other because the charge corresponding to the latter mode produces no contribution to the output current. Numerical results on output powers show that there are multi- valuedness and jump behaviors.     

ANALYSIS OF A TRANSIENT ELASTODYNAMIC CRACK IN PIEZOELECTRIC MATERIALS USING A SINGULAR INTEGRAL EQUATION METHOD

利用广义Betti-Rayleigh 互易公式给出了二维压电材料非渗透裂纹问题的一般解和奇异积分方程,其中未知函数为裂纹上的位移间断和电势间断的导数. 在理论分析的基础上,使用高斯-切比雪夫求积公式及Lubich 卷积积分方法建立了问题的数值求解方法,并给出典型算例的广义动应力强度因子随时间变化的规律.     

Angular stability of electric field‐induced effects in crystalline materials

We analyze angular bandwidths of extrema of the indicative surfaces describing spatial anisotropy of piezoelectric (PE) and electrooptic (EO) properties of doped lithium niobate (LiNbO₃:MgO) and langasite (La₃Ga₅SiO₁₄) crystals. A number of highly efficient experimental geometries are suggested, which are promising for PE and EO devices. Our data obtained with both analytical and numerical techniques characterize angular stability of those devices and, in particular, their angular aperture. We show that, besides of a maximal size of the electric field‐induced effects, ‘nondirect crystal cuts’ offer considerably higher angular stability of their characteristics, when compared with that typical for ‘direct crystal cuts’ usually employed in PE and EO devices.     

Evolution of electric response of Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 and Pb0.99[(Zr0.90Sn0.10)0.96Ti0.04]0.98Nb0.02O3 ferroelectric ceramics under shock wave compression

The objective of this work is to investigate the dependence of the electric behavior on shock pressure in Pb_0.99(Zr_0.95Ti_0.05)_0.98Nb_0.02O₃ (PZT 95/5-2Nb) and Pb_0.99[(Zr_0.90Sn_0.10)_0.96Ti_0.04]_0.98Nb_0.02O₃ (PZST) ferroelectric ceramics under shock wave compression. PZT 95/5-2Nb and PZST ceramics were subjected to high dynamic pressure generated by plate impacts. The output currents were measured under the short-circuit condition in the pressure range from 0.23 to 4.50 GPa. The evolution of the electric response exhibits three distinct regions: (1) Below the critical phase transition pressure (σ_C), alternate negative and positive piezoelectric currents are observed and the corresponding piezoelectric constant is e ₃₁. (2) Above σ_C and below the complete phase transition pressure (σ_H), released charge increases with increasing shock pressure, illustrating the transition of ferroelectric to antiferroelectric phase. (3) Above σ_H, the output current is insensitive to the shock pressure. A similar evolutionary process is also observed in hydrostatic and uniaxial stress experiments.