多层独石式压电微位移器的扫描电声像研究

对多层独石式压电微位移器的陶瓷／内电极层界面进行扫描电子显微镜（ＳＥＭ）和扫描电声显微镜（ＳＥＡＭ）的无损观察，发现该界面在ＳＥＭ和ＳＥＡＭ观察得到的像所给出的信息存在着很大差别，根据ＳＥＡＭ的成像原理，探针能谱分析（ＥＤＳ）以及器件本身陶瓷／内电极层间的层状结构形式，认为这种差异是由于器件在热压和烧结等制作过程中，陶瓷层和内电极层间不同的收缩率使得界面产生非均匀性力学性能而引起的，它与器件烧结时     

Finite element analysis of a multilayer piezoelectric actuator taking into account the ferroelectric and ferroelastic behaviors

Ferroelasticity and ferroelectricity are the non-linear behaviors exhibited by piezoceramics, especially in the case of high electric field or stress. Many studies have focused on the role of ferroelastic and ferroelectric switching in fracture of actuators. However, engineering reliability analyzes are carried out with tools like finite element software that do not take into account these non-linear phenomena. To overcome such a problem, a simplified phenomenological constitutive law describing the non-linear behavior of piezoceramics has been developed and implemented in the commercial software ABAQUS. This finite element tool is used to study the effects of applied voltage on the electroelastic field concentrations ahead of electrodes in a multilayer piezoelectric actuator. The study lies on the experimental observations made by Shindo et al. [Y. Shindo, M. Yoshida, F. Narita, K. Horiguchi, Electroelastic field concentrations ahead of electrodes in multilayer piezoelectric actuators: experiment and finite element simulation, J. Mech. Phys. Solids 52 (2004) 1109–1124]. Electroelastic analysis on piezoceramics with surface electrode showed that high values of stress and electric displacement arose in the neighborhood of the electrode tip. Thus, the strain, stress and electric displacement concentrations were calculated and the numerical results showed that ferroelectric switching arose in the area of the electrode tip, causing a change in remnant polarization and remnant strain.     

晶体结构对压电陶瓷微位移驱动器特性的影响

对钙钛矿结构的ＰＺＴ－５和钨青铜结构的ＰＢＮＮ二种压电陶瓷制成的压电微位移器进行了电压－位移特性的比较和分析，发现我们所研制的ＰＢＮＮ压电微位移器具有线性好、回零好、等优点。     

Piezoelectric control of delamination response in woven fabric composites under mode I loading

This paper investigates the application of piezoelectric actuators to control the delamination response in woven fabric composites subjected to Mode I loading. Experiments were conducted on a double cantilever beam (DCB) specimen of woven glass fiber reinforced polymer (GFRP) composite laminates with piezoelectric ceramic actuators bonded on the surfaces, in order to evaluate the dependence of the delamination behavior on the applied electric fields. A finite element analysis of the DCB specimen with surface-bonded actuators was also performed, and a comparison was made between the finite element predictions and the test results. In addition, the effect of the actuator location on the effectiveness of the piezoelectric control was examined numerically.     

Composite piezoelectric transducer with truncated conical endcaps“cymbal”

This paper presents original results obtained in the development of the moonie-type transducers for actuator applications. The moonie-type actuators fill the gap between multilayer and bimorph actuators, but its position-dependent displacement and low generative force are unacceptable for certain applications. The moonie transducers were modified systematically by using finite element analysis combined with experimental techniques. A new transducer design, named “cymbal transducer”, was developed with larger displacement, larger generative forces, and more cost-effective manufacturing. The cymbal transducers consist of a cylindrical ceramic element sandwiched between two truncated conical metal endcaps and can be used as both sensors and actuators. The cymbal actuator exhibits almost 40 times higher displacement than the same size of ceramic element. Effective piezoelectric charge coefficient, Eff. d₃₃, of cymbal is roughly 40 times higher than PZT itself     

Factors affecting the performance of piezoelectric bending actuators for advanced applications: an overview

The behaviors of piezoelectric bending actuators both in static and dynamic conditions driven by a high electric field were investigated and are summarized in this paper. In the static condition, the polarization and the displacement were measured and analyzed. It was found that the displacement hysteresis loop is the superposition of displacement loop induced by each layer of the actuator. The shape variation of the hysteresis loop is affected by the actuator configuration, i.e., the arrangement of electric field and poling direction. When the poling direction is parallel to an even electric field, such as parallel bimorph, the domain turns to switch at the exact coercive field of the piezoelectric material. However, when the poling direction is antiparallel to the electric field, such as series bimorph, the effect of electric field redistribution will take place during the domain reorientation, which reduces the actual electric field in the electric field–poling direction antiparallel layer, therefore prohibiting further domain reorientation. As a result, the series bimorph is noted to be more resistant to domain reorientation than the parallel bimorph. In the dynamic condition, the functions and relations of vibration velocity, heat generation, stress, and frequency were examined both theoretically and experimentally. It was found that the stress effect dominates at low frequency. At low frequency the failure mode of the actuator is often the physical fracture of the material. However, at high frequency, the failure modes mainly resulted from heat generation, unstable operation, depoling, and domain reorientation of the actuators. The vibration velocity will also decrease accordingly at the high frequency range due to more losses and heat generation.     

PZN-PZT Piezoelectric Multilayer Actuator with Ag/Pd Electrodes

1. IntroductionThe piezoelectric multilayer actuators have manyadvalltages such as small size, quick response timeand low driving voltage and arise much nit.re,tll'2].In the cofiring of MLA, the choice of electrodes mustbe carefully considered to reduce or avoid the interaction and the iaterdiffusion between the ceramic andthe electrodes. FOr PZT--based ceramic MLA withAg/Pd as internal electrodes, the interaction products such as PdpbO2, Pbpd,['] may cause delamination between ceramic l…     

Carbon Nanotube and Graphene‐based Bioinspired Electrochemical Actuators

Bio‐inspired actuation materials, also called artificial muscles, have attracted great attention in recent decades for their potential application in intelligent robots, biomedical devices, and micro‐electro‐mechanical systems. Among them, ionic polymer metal composite (IPMC) actuator has been intensively studied for their impressive high‐strain under low voltage stimulation and air‐working capability. A typical IPMC actuator is composed of one ion‐conductive electrolyte membrane laminated by two electron‐conductive metal electrode membranes, which can bend back and forth due to the electrode expansion and contraction induced by ion motion under alternating applied voltage. As its actuation performance is mainly dominated by electrochemical and electromechanical process of the electrode layer, the electrode material and structure become to be more crucial to higher performance. The recent discovery of one dimensional carbon nanotube and two dimensional graphene has created a revolution in functional nanomaterials. Their unique structures render them intriguing electrical and mechanical properties, which makes them ideal flexible electrode materials for IPMC actuators in stead of conventional metal electrodes. Currently although the detailed effect caused by those carbon nanomaterial electrodes is not very clear, the presented outstanding actuation performance gives us tremendous motivation to meet the challenge in understanding the mechanism and thus developing more advanced actuator materials. Therefore, in this review IPMC actuators prepared with different kinds of carbon nanomaterials based electrodes or electrolytes are addressed. Key parameters which may generate important influence on actuation process are discussed in order to shed light on possible future research and application of the novel carbon nanomateials based bio‐inspired electrochemical actuators.     

A sensor charge output deviation method for delamination detection using isolated piezoelectric actuator and sensor patches

Delamination is one of the most prevalent failure mechanisms for laminated composites. To secure the safety of composite structures, it is required and necessary to develop cost-effective and efficient delamination detection techniques and methods. In this paper, a dynamic analytical model, namely sensor charge output deviation method is proposed to identify a delamination embedded in a cantilever laminated composite beam bonded with isolated piezoelectric actuator and sensor patches. Two pairs of collocated piezoelectric patches are bonded on top and bottom surfaces of the beam and used as actuators for exciting the composite beam. Another piezoelectric patch with gridding electrode pattern on its top surface is bonded on the top surface of the host beam and is employed as a sensor to record the required voltage and thus the sensor charge output along the beam. The effects of some major geometric parameters and the type of applied electric voltage on the sensor charge output distribution and delamination detection sensitivity are discussed in this paper. A comparison between the analytical models using isolated piezoelectric actuator and sensor patches and that using integrated piezoelectric sensor/actuator layer, which was developed previously, is conducted. For the baseline case considered here, there is an excellent agreement of the first three order frequencies between the present finite element analysis and analytical models.     

Compact piezoelectric stacked actuators for high power applications

Small, hollow, multilayer actuators with a diameter of 3 mm were fabricated by the stacking method from piezoelectric hard lead zirconate titanate (PZT) ceramics. Langevin vibrators were also constructed with the hollow multilayer actuators. The performance capabilities of the actuator and Langevin vibrator samples were examined under high-power conditions. The high-power vibration level at a given sinusoidal drive voltage was significantly enhanced by using a multilayer structure under either a nonresonance or resonance condition. A maximum vibration velocity of 0.17 m/sec was obtained for the 9-layer actuator sample under nonresonance conditions. The vibration velocity was further improved with the Langevin vibrator driven at the resonance frequency. The temperature rise due to heat generation under high-power conditions was the immediate limitation on the maximum accessible vibration velocity for the stacked actuators.     

Design and fabrication of functionally graded PZT/Pt piezoelectric bimorph actuator

A laminated piezoelectric bimorph actuator with a graded compositional distribution of PZT and Pt was fabricated, and its deflection characteristics were evaluated. Using experimentally determined compositional dependency of elastic and piezoelectric properties in the PZT/Pt composites, the modified classical lamination theory and the finite element method were applied to find the optimum compositional profile that will give a larger deflection and smaller stress, simultaneously. The miniature bimorph-type graded actuator that consists of a composite internal-electrode (PZT/30 vol% Pt) and three piezoelectric layers of different compositions (PZT/0–20 vol% Pt) were fabricated by powder stacking and sintering. The deflection of the actuator was measured using electric strain gages mounted on the top and bottom surfaces of the actuator. The deflection was found to strongly depend on the composition distribution profile. Under an applied electric field of 100 V m^–1, the actuator with an optimum composition profile exhibited a curvature of up to 0.03 m^–1, which is a satisfactory performance for this kind of actuators. The stress generated on actuation was estimated to be as low as 0.4 MPa, which is much smaller than those of conventional directly bonded actuators and will assure a long actuation life.     

应力对压电陶瓷驱动器位移性能的影响

在研制由钨青铜型压电陶瓷分立驱动器组装成特种圆环状压电驱动器中,发现组装后横向位移模圆环驱动器的位移量呈现异常的变化;它的位移量比分立器件的增加可达～３０％．对组成、器件制备等进行了大量实验,分析认为;分立器件在组装后处于严重的压应力中,它对逆压电效应的影响是上述结果的原因．它的主要机制是在压应力下通过９０°畴重新取向或钨青铜结构中基本组元－氧八面体的畸变使自发极化偏离于原压应力方向,一旦施加电场则造成位移量的大大增加．     

Effect of nano-sized TiO<Subscript>2</Subscript> powder addition on characteristics of silver–palladium electrodes

This study presents the sintering behavior of silver/palladium electrode powders to which have been added TiO₂ nanoparticles, and the effect this additive has on the ability of the electrode to match the characteristics of piezoelectric ceramics, Pb(Zr, Ti)O₃. The densification (shrinkage) of the electrodes was investigated as a function of sintering temperature, and the reaction between the ceramic matrix and the electrodes was studied. The densification of the TiO₂-enhanced electrode paste during the sintering process was explained with reference to a solid-state diffusion mechanism which integrated the TiO₂ into the ceramic. Reactions occurred between the ceramic and electrode layers, resulting in reduced internal stress and enhanced mechanical adhesion. Based on these results, it is clear that high adhesive strength and good electrical conductivity of more than 10⁴/Ω cm can be obtained in multilayer ferroelectric devices composed of stacks of ceramic and electrode layers provided the contain these nanoparticles. In the sintering process, interfacial diffusion of TiO₂ occurred and, as a consequence, coarse grains of PZT were formed at the interface.     

Superfast-response and ultrahigh-power-density electromechanical actuators based on hierarchal carbon nanotube electrodes and chitosan

Here we report a novel single-walled carbon nanotube (SWNT) based bimorph electromechanical actuator, which consists of unique as-grown SWNT films as double electrode layers separated by a chitosan electrolyte layer consisting of an ionic liquid. By taking advantage of the special hierarchical structure and the outstanding electrical and mechanical properties of the SWNT film electrodes, our actuators show orders-of-magnitude improvements in many aspects compared to previous ionic electroactive polymer (i-EAP) actuators, including superfast response (19 ms), quite wide available frequency range (dozens to hundreds of Hz), incredible large stress generating rate (1080 MPa/s), and ultrahigh mechanical output power density (244 W/kg). These remarkable achievements together with their facile fabrication, low driving voltage, flexibility, and long durability enable the SWNT-based actuators many applications such as artificial muscles for biomimetic flying insects or robots and flexible deployable reflectors.     

Wave propagation generated by piezoelectric actuators attached to elastic substrates

Summary Piezoelectric actuators can be used to generate high-frequency elastic waves for damage identification of materials. This paper provides a comprehensive theoretical study of the electromechanical behavior of surface-bonded or embedded piezoelectric actuators under inplane electric fields. A modified one-dimensional actuator model is introduced, from which arbitrarily distributed electric fields along the actuator can be considered. The model is used to simulate the dynamic load transfer between the actuator and the host medium and the resulting elastic wave propagation by using the integral transform method and solving the resulting singular integral equations. Of particular interest is the generated waveform away from the actuator under different electric fields. An asymptotic analysis is conducted to obtain the far-field solution of the wave field. The property of the resulting waveform is studied, and the simulation shows that the direction of wave propagation can be adjusted by controlling the phase distribution of the applied electric field along the actuator.     

Design and fabrication of functionally graded PZT/Pt piezoelectric bimorph actuator

A laminated piezoelectric bimorph actuator with a graded compositional distribution of PZT and Pt was fabricated, and its deflection characteristics were evaluated. Using experimentally determined compositional dependency of elastic and piezoelectric properties in the PZT/Pt composites, the modified classical lamination theory and the finite element method were applied to find the optimum compositional profile that will give a larger deflection and smaller stress, simultaneously. The miniature bimorph-type graded actuator that consists of a composite internal-electrode (PZT/30 vol% Pt) and three piezoelectric layers of different compositions (PZT/0–20 vol% Pt) were fabricated by powder stacking and sintering. The deflection of the actuator was measured using electric strain gages mounted on the top and bottom surfaces of the actuator. The deflection was found to strongly depend on the composition distribution profile. Under an applied electric field of 100 V m⁻¹, the actuator with an optimum composition profile exhibited a curvature of up to 0.03 m⁻¹, which is a satisfactory performance for this kind of actuators. The stress generated on actuation was estimated to be as low as 0.4 MPa, which is much smaller than those of conventional directly bonded actuators and will assure a long actuation life.     

A Resistivity Gradient Piezoelectric FGM Actuator

To whom correspondence should be addressedE-mail: zymeng@guomai.sh.cn1. IntroductionDuring the last several years the application ofpiezoelectric materials as reliable micro scale positioner has undergone considerable research and development work[1-3]. The two most common typesof piezoelectric actuators are the multilayer ceramicactuator with internal electrodes and the cantileveredbimorph actuator. However these technologies havetheir limitations in regard to size, weight, maximum displacem…     

Dielectric Elastomers in Actuator Technology

Electroactive polymers (EAPs) are characterized by their ability to respond to external electric stimulation by displaying a significant shape or size displacement. Actuators, based on dielectric elastomers exhibiting low elastic stiffness and high dielectric constants, can produce high strain levels from 10 to 380 %. Typically, acrylic and silicone materials are used as dielectric layer in such actuators. Their potential to mimic the movement of animals, insects and even human body parts are increasingly of interest for researchers in the field of biomimetics, as well as more classical application fields like robotics. The control of the most important material properties, elastic moduli and dielectric constants of the dielectric elastomers and electrode materials, together with the control of fabrication parameters i.e. film thickness, electrode manufacturing as well as design of the actuator configuration allow the fabrication of tailor‐made actuators, which match the necessary requirements for a given application. Theoretical models contribute to a deeper understanding of EAP actuators and improve design and optimisation.     

The influence of electrodes on the strength of planar zirconia solid oxide fuel cells

The strength of symmetric anode/electrolyte/anode and cathode/electrolyte/cathode planar multiple electrode assemblies (MEAs), fabricated by screen printing electrodes onto pre-fired tape-cast electrolyte plates was measured in biaxial flexure. The electrolyte was Zr_0.84Y_0.16O_1.92 (YSZ), the anode NiO/YSZ and the cathode La_0.75Sr_0.2MnO_3–. The residual stress in the electrodes was estimated by curvature measurement after removal of one electrode. The residual stress in the anodes was very low (11 MPa) due to stress relief by extensive channel cracking. The residual stress in the cathodes was much higher (39 MPa) and was in reasonable agreement with the expected thermoelastic stress. The applied load at failure, and the stress in the electrolyte at failure (343 MPa), for anode MEAs were almost equal to those of electrolyte plates (374 MPa). This is consistent with the low residual stress and observed crack deflection by delamination at the anode/electrolyte interface. The applied load at failure, and the stress in the electrolyte at failure (182 MPa), for cathode MEAs were much lower. This is partially explained by the residual stress in the cathode acting to increase the applied stress intensity at defects in the electrolyte, but this effect is not large enough to explain fully the reduced strength.     

Design optimization of dome actuators

This paper reports the conceptual design, analysis, and modeling of the electromechanical behavior of dome actuators. The geometric parameters of the actuator (dome thickness, width, radius, and depth), poling direction, electric field, and material properties (elastic compliance, piezoelectric constants, and dielectric permittivity) have been taken into account in the modeling work. The results of the analysis indicate that a dome actuator with a tangentially alternating poling direction and electric field (Case C) exhibits much larger displacement and force responses than dome actuators with other poling directions and electric fields. The first mode of natural frequency of the Case C dome actuator also was investigated, and its predicted performance was compared with that of moonie and rainbow actuators. The findings of this research clearly demonstrate the merit of design optimization of electromechanical devices.