双迭片弯曲压电陶瓷换能器及振动模态分析测量

介绍了双迭片弯曲压电陶瓷换能器的制作及边缘固定金属压电陶瓷双迭片弯曲振动，并利用有限元分析了换能器的谐振模式，采用激光多普勒干涉仪对换能器的谐振特性以及振动速度和位移分布进行了测量和分析，结果表明：换能器空载性能良好，通过有限元分析与先进测量手段的结合，能够对换能器器件的制作与分析进行指导。     

双迭片压电振子的振动研究

利用压电方程和小挠度弯振理论,推导了边界自由压电陶瓷双迭片薄板小挠度条件下弯曲振动位移的一般解及振型频率方程。由频率方程计算得到的各阶振型频率与用有限元方法计算的结果基本相符,并基本得到实验结果的验证。所得结论对边界自由双迭片压电振子弯曲振动的设计提供了理论参考。     

压电陶瓷圆环与金属圆环复合振动系统的径向振动

对由压电陶瓷圆环与金属圆环组成的复合振动系统的径向振动特性进行了研究。首先分析了压电陶瓷圆环和金属圆环的径向振动,推出了其各自的机电等效电路。在此基础上,得出了压电陶瓷圆环与金属圆环复合振动系统的机电等效电路及其共振频率方程。探讨了系统的共振及反共振频率、有效机电耦合系数与其几何尺寸之间的关系。研究表明,当复合振动系统的壁厚比增大时,其共振及反共振频率升高。对于换能器的第一阶径向振动,其有效机电耦合系数随壁厚比的增大而单调减小;对于换能器的第二阶径向振动,其有效机电耦合系数随壁厚比的增大会出现一个极大值,而且,在一定的壁厚比范围内,换能器第二阶径向振动的有效机电耦合系数大于第一阶径向振动的有效机电耦合系数,这一规律与传统的有关压电换能器的分析理论及结果是有所不同的。     

三维同振型矢量水听器设计

为了使同振型压电陶瓷矢量水听器在低频和甚低频下有高的振速接收灵敏度和优良的偶极方向性,采用高灵敏度的双迭片压电弯曲圆片作为加速度计和注水银技术。简要介绍了该矢量水听器的结构设计和水银量补偿两个关键技术,给出三维同振型矢量水听器声学性能测试结果。     

扭转振动压电超声换能器的研究

本文对夹心式复合结构压电超声扭转振动换能器进行了系统的理论研究，该换能器由两段金属真圆棒及切向极化的压电陶瓷圆片堆复合而成，文中首先研究了切向极化压电陶瓷细长管的扭转振动性，推出了其机电等效电路，并提出了压电陶瓷细长管截面扭转系数的概念。，     

压电复合材料用于透镜式聚焦换能器的研究

为了增加聚焦换能器的带宽, 抑制其多模振动耦合现象, 提高电声转换效率, 实验采用1-3型压电复合材料代替压电陶瓷作为超声发射材料, 设计并制作了一种新型的1-3型压电复合材料透镜式聚焦换能器。通过频率特性的对比研究, 证明了1-3型压电复合材料透镜式聚焦换能器不仅能增加换能器的带宽, 达到PZT压电陶瓷透镜式聚焦换能器带宽的3.13倍, 而且能明显抑制径向振动, 得到单一纯净的厚度振动模态。另外, 1-3型压电复合材料透镜式聚焦换能器的电声转换效率达到PZT压电陶瓷透镜式聚焦换能器的1.88倍, 为高效率聚焦超声换能器的实现提供了理论及实验基础。     

指数型纵—扭复合模式超声换能器研究

纵-扭复合模式夹心式压电超声换能器是超声马达、超声加工等应用技术中的重要组成部分.本文研究的复合模式换能器由圆柱型金属后盖板、指数型金属前盖板及轴向极化和切向极化的二组压电陶瓷晶堆组成.导出了换能器中纵向振动与扭转振动模式的共振频率方程.并得出了两种振动同频共振的条件.实验表明.换能器的测试频率与设计频率符合很好.且换能器的纵向共振频率与扭转共振频率基本一致.     

超声波料位仪的研制

超声料位仪上的换能器主要是夹心式和多波节复合弯曲换能器，本文介绍了一种采用压电陶瓷圆管径向振动模式的超声波料位仪，它的工作频率21kHz，最大量程25m，盲区≤0．85m，工作可靠性能稳定．     

弯曲振动气介式超声换能器的振动特性及辐射声场研究

本文对弯曲振动气介式超声换能器进行了研究，推出了夹心式换能器与弯曲圆板二者复合振子的机电等效电路及其总体频率方程，得出了其远场声压分布及指向性的解析表达式，并数值计算了换能器近场三维声压分布。     

大位移压电陶瓷驱动器的设计与试验

针对大位移压电陶瓷驱动器,研究了压电陶瓷双晶片的驱动效能。基于压电陶瓷材料的逆压电效应,应用压电陶瓷双晶片在机械自由、电学短路状态下,一片加正向电压缩短另一片加反向电压伸长共同作用产生弯曲变形,通过组合设计将压电陶瓷双晶片的弯曲变形位移叠加起来,实现了压电陶瓷驱动器的大位移输出。在相同电压的条件下,此压电陶瓷驱动器的输出位移量比叠层驱动器有较大的增加,达200μm,结构尺寸也大大减小。该驱动器不需要位移放大机构,可直接应用于有大位移要求的机构驱动。     

Free vibration analysis of the piezoceramic bimorph with theoretical and experimental investigation

This paper investigates the vibration characteristics of an asymmetric, three-layered piezoceramic circular bimorph under traction-free boundary conditions by applying the electroelasticity and Kirchhoff plate theory. The asymmetric, three-layered bimorph consists of an isotropic shim layer and two piezoceramic layers of equal thickness and same polarization. Two optical techniques, amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and laser Doppler vibrometer (LDV), are used to validate the theoretical analysis. The resonant frequencies of the piezoceramic bimorph also are measured by an impedance analyzer. Both theoretical and experimental results indicate that the transverse vibration modes cannot be measured by impedance analysis, and only resonant frequencies of extensional vibration modes are present. However, transverse vibration modes of the piezoceramic bimorph can be obtained by the AF-ESPI and LDV measurements. The numerical calculations also are obtained using the finite-element method (FEM), and the results agree comparatively well with the theoretical analysis and experimental measurements. According to the theoretical calculation, the variations in resonant frequencies and effective coupling factors versus the various layer-thickness ratios also are investigated in this work.     

SPICE model for lossy piezoceramic transducers

A transmission line equivalent circuit for piezoelectric transducers has been modified to provide modeling of lossy piezoceramic transducers. A lossy transmission line is used to model the mechanical losses. The equivalent circuit parameters are derived from analogies between electrical transmission lines and acoustic wave propagation. Implementation of the equivalent circuit model in SPICE is shown. Simulations and measurements in the time and frequency domain of a low-Q material and a multilayered ultrasonic sensor using a low-Q piezoceramic transducer are presented.     

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     

Resonances in the System of Shield-Coupled Hydroacoustic Piezoceramic Transducers

Strength of Materials - Outcomes of the stress state investigations are presented for cylindrical hydroacoustic piezoceramic transducers on their operation in the shielded electroacoustic systems,...     

压电陶瓷堆位置对郎之万换能器内部损耗的影响

压电陶瓷堆位置是郎之万换能器优化设计的一个重要对象,人们对其研究较多但结论并不一致。文章主要考虑压电陶瓷的机械损耗及介电损耗,分析了恒振幅输出时这两种损耗与压电陶瓷堆位置的关系,并通过引入负载系数探讨了不同负载情况下压电陶瓷堆位置对郎之万换能器内部损耗的影响。分析结果表明,对于不同的负载,压电陶瓷堆均对应一个最佳位置,此时换能器的内部损耗最小,且随着负载的增大,这一最佳位置逐渐向换能器的节点位置靠近。可见,压电陶瓷堆位置的优化设计与实际负载密切相关,以往关于该问题的不同结论源于其仅针对某种特定负载分析而得。     

Piezoelectrically driven morphing structures based on bistable unsymmetric laminates

Due to their anisotropy multilayered fibre-reinforced polymers tend to generate residual stresses, which are primarily influenced by thermal and hygroscopic processes. In the case of an unsymmetric reinforcement architecture, those residual stresses may induce large out-of-plane deformations in thin-walled laminates. Here, specific stacking sequences support the development of so called bistable laminates which are characterised by two distinct deformation states which can be converted by applying forces or bending moments. In combination with appropriate actuator systems, like piezoceramic transducers, such bistable composites can purposefully be used to design compliant mechanisms and novel morphing structures that stand out for a permanent change of shape only by a small energy supply. For the structural analysis and the computation of the necessary actuation voltage to initiate the snap-through of bistable composite structures with piezoceramic actuators, non-linear semi-analytical and numerical simulation methods have been elaborated. First active bistable prototypes have been manufactured and successfully tested.     

Ultrasound transducer modeling--general theory and applications to ultrasound reciprocal systems

A tutorial presentation on the theory of reciprocal ultrasound systems is given, and a complete set of modeling equations for one-dimensional multi-layer ultrasound transducers is derived from first principles. The model includes dielectric losses and mechanical losses in the transducer material layers as well as sound absorption in the transmission medium. First, the so-called constitutive relations of a piezoelectric body are derived based on general thermodynamic considerations, assuming that transducer operation takes place under almost isentropic conditions. Second, full attention is given to transducers oscillating in the thickness mode, discarding all other vibration modes. Dynamic transducer equations are determined using Newton's Second Law, Poisson's equation, and the definition of strain applied to a piezoelectric transducer with one or more non-piezoelectric layers on the front surface (multilayer transducer). Boundary conditions include continuity of normal velocity and stress across material interfaces as well as a subsidiary electrical condition over the piezoceramic electrodes. Sound transmission is assumed to take place in a water bath such that the Rayleigh equation can be used to obtain the incoming pressure at the receiver aperture from the acceleration of the opposing transmitter. This allows, e.g., a detailed treatment of receiver signal variations as the receiver moves from the near-field zone to the far-field zone of the transmitter. In the remaining part of the paper, receiver voltage and current signals are obtained by solving the full set of dynamic equations numerically. Special attention is given to transducers consisting of a) a pure piezoceramic layer only, b) a piezoceramic layer and a quarter-wavelength matching layer of polyphenylensulphide (PPS), c) a piezoceramic layer and a half-wavelength matching layer of stainless steel, and d) a piezoceramic layer and a half-wavelength matching layer of stainless steel tuned to resonance by a parallel inductance. Results are also given for receiver incoming pressure and receiver voltage signals when sound reception takes place in the near-field and far-field zones of the transmitter.     

Preparation and characterization of thin transducer layers sensitive to free chlorine in water

The paper deals with preparation and characterization of layers of optical absorption transducers sensitive to free chlorine in water and based on commercially available chemicals. The electrochemical deposition and chemical approach based on the sol–gel method were employed for the immobilization of the transducers onto ITO-coated planar optical substrates. The transducers, namely methylene blue, o-phenylenediamine, Lu (III) acetate pthalocyanine tetrasulfonate tetrasodium salt (Lu-III-complex), murexid, quercetin, 1,2,3-benzenetriazole, benzopurpurine, thionine, bilirubin and its metal complexes, and 3-methyl-4 nitro-1(4-nitrophenyl) 2-pyriazoline-5-one (picrolonic acid), were tested. Transmission spectra, redox potentials, layer thickness and optical responses of the transducer layers to chlorine were investigated. By using sensitive layers based on o-phenylenediamine and methylene blue it was possible to detect chlorine in a minimum concentration of 0.25 ppm. The best results were obtained with the o-phenylenediamine layers prepared electrochemically. Both these transducer layers are useable for detection of chlorine up to concentration  8 ppm.