Piezoelectric Shear Research Articles

Acoustofluidics 4: Piezoelectricity and application in the excitation of acoustic fields for ultrasonic particle manipulation

Piezoelectric materials are widely used in the excitation of MHz frequency vibrations in devices for ultrasonic manipulation. An applied electrical voltage is transformed into mechanical stress, strain and displacement. Piezoelectric elements can be used in either a resonant or non-resonant manner. Depending on the desired motion the piezoelectric longitudinal, transverse or shear effects are exploited. Because of the coupling between electrical and mechanical quantities in the constitutive law the modelling of devices turns out to be quite complex. In this paper, the general equations that need to be used are delineated. For a one-dimensional actuator the underlying physics is described, including the consequences resulting for the characterization of devices. For a practical setup used in ultrasonic manipulation, finite element models are used to model the complete system, including piezoelectric excitation, solid motion and acoustic field. It is shown, how proper tailoring of transducer and electrodes allows selective excitation of desired modes.

Vibration Control of a Space Flexible Robot Manipulator Using PZT Actuators

The dynamic analysis and control of flexible robot manipulators have been the main concerns of many recent studies in aeronautics and robotics. Moreover, the complexity of this problem increases when a flexible manipulator carries a payload. In this paper, we proposed a space two-link flexible manipulator with tip payload featuring surface-bonded piezoelectric torsional actuator and shear actuator. The equations of motion for the system are obtained using Hamilton’s principle. A Lyapunov-based controller is proposed to suppress the vibration of the system. Stability of the system is also investigated. The simulation results demonstrate the proposed control strategy is well suited for active control of vibration suppression on flexible manipulators.

Design and Application of a Novel Piezoelectric Torsional Actuator

In this paper, a piezoelectric torsional actuator generating angular displacement from piezoelectric shear strain is proposed. The procedure for the design, and manufacture of the piezoelectric torsional actuator are presented. To evaluate the performance of the proposed piezoelectric torsional actuator, the torsional vibration suppression of a flexible manipulator system with the proposed actuator is studied. The experimental results show the piezoelectric torsional actuator is capable of producing large torque and angular displacement and is suited for vibration suppression on flexible torsional manipulator system.

Monolithic Piezoelectric Sensor for Measurement of Triaxial Forces Applied to Bridge by String Vibration

We propose a piezoelectric sensor to investigate string vibration. This sensor has a square pyramidal structure and five electrodes on each surface, and enables us to measure triaxial forces. Measuring triaxial forces from a single sensor enables us to obtain complex vibration mechanisms, such as the string vibration of musical instruments. We designed the sensor to serve as a bridge of musical instruments and to measure triaxial forces applied by string vibration directly. A previously proposed sensor, which also serves as the bridge, has a problem regarding its charge sensitivity. To improve charge sensitivity, the newly proposed sensor is designed to have large electrodes by devising its structure. The sensitivity of the newly proposed sensor is compared with that of the previously proposed sensor using a finite element method. The sensitivity of the proposed sensor becomes higher than that of the previous sensor. In particular, the sensitivity of the proposed sensor in the horizontal direction becomes about 2.5 times higher than that of the previous one. The reason for this is that the new sensor is applied with a piezoelectric shear effect to measure its sensitivity in the horizontal direction, while the previous one is applied with a longitudinal effect. The constant of the piezoelectric shear effect is generally about two times higher than that of the longitudinal effect. Moreover, we obtain the sensitivity of the proposed sensor in the experiment. The experimental results suggest that the triaxial force can be measured by calculating the pseudo-inverse matrix of the measured sensitivity.

Control of torsional vibrations in piezolaminated rods

This paper is concerned with active control of torsional vibrations in laminated rods by piezoelectric shear sensors and actuators. A piezoelectric layer can be used as a sensor by utilizing the direct piezoelectric effect, measuring either the charge on short-circuited electrodes or the voltage on open electrodes. On the other hand, the converse piezoelectric effect enables actuation by applying an electric potential difference to the electrodes of a piezoelectric layer. The sensor and actuator equations are formulated in the framework of an extended Saint-Venant torsion theory considering additional cross-sectional warping due to piezoelectric eigenstrains. A solution of the shape control problem for torsional vibrations is presented, i.e. the necessary distribution of actuation strains in order to completely compensate vibrations caused by external excitations. For the case, in which the external excitations are not known exactly, a feedback control solution is presented using one piezoelectric layer as a sensor and a second one as an actuator. For the examples of a rectangular and a circular cross-section, the theoretical results are validated by three-dimensional finite element computations, showing a very good coincidence. Copyright © 2011 John Wiley & Sons, Ltd.

Field stability of piezoelectric shear properties in PIN-PMN-PT crystals under large drive field.

The coercive fields (E(C)) of Pb(In₀.₅Nb₀.₅)O₃-Pb(Mg(¹/₃)Nb(²/₃)O₃-PbTiO₃ (PIN-PMN-PT) ternary single crystals were found to be 5 kV/cm, double the value of binary Pb(Mg(¹/₃)Nb(²/₃)O₃-PbTiO₃ (PMNT) crystals, further increased to 6 to 9 kV/cm using Mn modifications. In addition to an increased EC, the acceptor modification resulted in the developed internal bias (E(int)), on the order of ~1 kV/cm. The piezoelectric shear properties of unmodified and Mn-modified PIN-PMN-PT crystals with various domain configurations were investigated. The shear piezoelectric coefficients and electromechanical coupling factors for different domain configurations were found to be >2000 pC/N and >0.85, respectively, with slightly reduced properties observed in Mn-modified tetragonal crystals. Fatigue/cycling tests performed on shearmode samples as a function of ac drive field level demonstrated that the allowable ac field levels (the maximum applied ac field before the occurrence of depolarization) were only ~2 kV/cm for unmodified crystals, less than half of their coercive field. Allowable ac drive levels were on the order of 4 to 6 kV/cm for Mn-modified crystals with rhombohedral/orthorhombic phase, further increased to 5 to 8 kV/cm in tetragonal crystals, because of their higher coercive fields. It is of particular interest that the allowable ac drive field level for Mn-modified crystals was found to be ≥ 60% of their coercive fields, because of the developed E(int), induced by the acceptor-oxygen vacancy defect dipoles.

S112043 ISO 16047に準拠した新しいねじ締付け試験機の開発 : 水晶圧電式センサシステムの特性評価([S11204]機械要素の設計・製造・応用技術(4))

It is one of the most important issues for structural safety to control the clamp force of bolted joints. However, the accuracy of the testing apparatus commercially available to evaluate the tightening characteristics for wide variety of fasteners is not sufficient. This study aims to develop a new testing machine for torque/clamp force testing, which will meet the requirement specified in ISO 16047. In this study, the root cause of measuring error of the piezoelectric sensor system is analyzed both experimentally and analytically. As a result, it is found that both the torque acting on the preloading bolts and shear stress distribution on the sensor surface may affect sensitivity of piezoelectric shear force sensors as well as the inherent characteristics of the sensors, and the configuration of the sensor system is proposed to reduce the measuring error.

Piezoelectric d15 shear response-based torsion actuation mechanism: an experimental benchmark and its 3D finite element simulation

An experimental benchmark is proposed for piezoelectric, direct-torsion actuation using mono-morph piezoceramic d15 shear patches. This is reached by designing and assembling an adaptive plate having two identical composite faces sandwiching a core made of connected six oppositely polarized (OP) piezoceramic d15 shear patches along the length. An electronic speckle pattern interferometry system was used to measure the static tip deflection of the adaptive sandwich composite plate that was mounted in a cantilever configuration and actuated in torsion by progressively applied voltages on the piezoceramic shear core electroded major surfaces. Then, the effective rate of twist was post-processed and proposed as an evaluation criterion for smart composites under piezoelectric torsion actuation. For verification of the experimental results, the proposed experimental benchmark was simulated using three-dimensional piezoelectric finite elements (FE) within ABAQUS® commercial software. The comparison of the obtained experimental and simulation results showed reasonable agreement, but the slight nonlinear experimental response was not confirmed by the linear FE analysis. The experimentally proved torsion actuation mechanism, produced by OP piezoceramic d15 shear patches, can be applied actively to prevent torsion in many applications, such as in wind turbines, helicopter blades, robot arms, flexible space structures, etc.

Nonlinear Shear Response in (K,Na)NbO<sub>3</sub>-Based Lead-Free Piezoelectric Ceramics

The piezoelectric shear response of 94.0(Ka0.5, Na0.5)NbO3 (KNN) + 5.0LiNbO3 (LN) + 0.5SrTiO3 (ST) + 0.5BiFeO3 (BF) ceramics was investigated by Laser Doppler Vibrometry (LDV) and resonance-antiresonance method. From resonance-antiresonance method, the piezoelectric d15 constant was obtained to be 273 pC/N. The shear strain obtained by LDV at the frequency of 150kHz showed strong nonlinearity. This suggested that the domain contribution to piezoelectric response in shear mode of KNN-LN-ST-BF ceramics existed at the operational frequency for the shear mode divices.

Optimal shape control of a beam using piezoelectric actuators with low controlvoltage

This paper deals with the shape control of a cantilever beam structure by using laminatedpiezoelectric actuators (LPAs) with a low control voltage. The shape control equation ofthe cantilever beam partially covered with LPAs is derived based on the constitutiverelations of the elastic material and piezoelectric material and shear deformation beamtheory (Timoshenko theory). The actuating forces produced by the LPAs areformulated as well. It reveals how the actuating forces depend on the number ofpiezoelectric layers, the thickness of piezoelectric layers and the position of theactuators. The driving voltages of the LPAs are then determined by a geneticoptimization algorithm. The shape control of the cantilever beam from applying theoptimal voltage to the LPAs is simulated. The simulation results show that anLPA of large layer number is able to diminish effectively the pre-deflection of thebeam under a low control voltage. The voltage applied to the LPA of five layerswas almost five times smaller than that of one layer. In addition, increasing thenumber of LPA layers can significantly improve the control performance as theacting forces of the LPA are a quadratic function of the LPA layer number. TheL2 norm of the displacement array of all nodes is diminished about 30% after optimization.Also with the same low control voltage, the LPA can obtain a better control performancethan the conventional single layer piezoelectric actuator.

Saint-Venant’s Problem for Compound Piezoelectric Beams

The solution of the Saint-Venant’s Problem for a slender compound piezoelectric beam presented in this paper generalizes the recent solution by the authors and E. Harash (J. Appl. Mech. 11:1–10, 2007) for a homogeneous piezoelectric beam and the solution for a compound elastic beam developed by O. Rand and the first author (Analytical Methods in Anisotropic Elasticity with Symbolic Computational Tools, Birkhauser, Boston, 2005). Justification for this approximation emerges from the St. Venant’s Principle. The stress, strain and (electrical) displacement components (“solution hypothesis”) are presented as a set of initially assumed expressions involving twelve tip loading parameters, six unknown weight coefficients, and three pairs of torsion/bending functions of two variables. Each pair of functions satisfies the so-called coupled non-homogeneous Neumann problem (CNNP) in the cross-sectional domain. The work develops concepts of the torsion/bending functions, the torsional rigidity and piezoelectric shear center, the tip coupling matrix, for a compound piezoelectric beam. Examples of exact and approximate solutions for rectangular laminated beams made of transtropic materials are presented.

Vibration Welding Quality Control using Piezoelectric Shear Stress Transducers

The quality control (QC) of welded parts is a critical manufacturing step. Although QC can be performed on the finished part, identification of defects during the manufacturing process is preferred to minimize the value associated with defective parts. In this paper, the use of piezoelectric shear stress transducers mounted on vibration welding fixtures is presented as a real-time QC tool. Laboratory studies complemented with welding trials on industrial air-intake manifolds show that this technology can be used to identify defects such as incomplete weld beads.

Compensation of torsional vibrations in rods by piezoelectric actuation

In this paper, the piezoelectric compensation of torsional vibrations in rods caused by external excitations is studied. As an illustrative example, a laminated rod containing piezoelectric shear actuators is assumed to be fixed at the one end, and the other end is subjected to a torsional couple; additionally, a distributed torsional couple per unit length is acting. In such a system, cross-sectional warping is known to be present. The consideration of piezoelectric eigenstrains requires an extension of Saint Venant’s theory of torsion, which is achieved by introducing an additional warping function. Using D’Alembert’s principle, the boundary value problems for Saint Venant’s warping function, the additional warping function and the torsional angle are obtained. From the latter boundary value problems, the distribution of piezoelectric actuation is derived in order to completely compensate the external excitations, i.e. an analytical solution of the corresponding shape control problem is obtained. Finally, the results are verified by means of three-dimensional finite element computations.

Processing of PZT actuator and nickel plate in a multi-droplets microejector

The fabrication processes of components for a liquid microejector are described in the paper. The components of the microejector, the vibration plate and the nozzle nickel-made plate, were produced by multilevel electroforming of UV-LIGA technology. A shear-mode PZT actuator, manufactured by powder metallurgy, was devised to drive the microejector for generating tiny liquid droplets. This plate-shaped actuator poled with remnant polarization perpendicular to the actuating field induced a piezoelectric shear effect. The polarizing procedure of the PZT actuator was illustrated in detail. The components were bonded together by thermosetting adhesive. The temperature effect on the PZT actuating performance was further investigated since the bonding temperature can substantially affect the electromechanical properties of the PZT actuator. An appropriate bonding temperature for PZT actuator was suggested.

Real-time monitoring of adhesion and aggregation of platelets using thickness shear mode (TSM) sensor

Hemostasis is required to maintain vascular system integrity, but thrombosis, formation of a clot in a blood vessel, is one of the largest causes of morbidity and mortality in the industrialized world. Novel clinical and research tools for characterizing the hemostatic system are of continued interest, and the object of this research is to test the hypothesis that clinically relevant platelet function can be monitored using an electromechanical sensor. A piezoelectric thickness shear mode (TSM) biosensor coated with collagen-I fibers to promote platelet activation and adhesion was developed and tested for sensitivity to detect these primary events. Magnitude and frequency response of the sensor were monitored under static conditions at 37 °C, using platelet-rich plasma (PRP), and PRP with adenosine diphosphate (ADP), a clinical aggregation inhibitor (abciximab), or a collagen binding inhibitor. Sensors loaded with PRP exhibited a 3-stage response; no significant change in response for the first 20 min (Stage-1), followed by a larger drop in response (Stage-2) and subsequently, response gradually increased (Stage-3). Exogenous ADP stimulated an immediate Stage-2 response, while abciximab delayed and reduced the magnitude change of Stage-2. In the presence of collagen inhibitor, Stage-2 response was similar to that of control but was delayed by an additional 20 min. The obtained results, supported by epifluorescence and complementary SEM studies, demonstrated the selective sensitivity of TSM electromechanical biosensors to monitor platelet function and inhibition, particularly aggregation.

Dynamic response and active control of a composite cylindrical shell with piezoelectricshear actuators

This paper presents exact solutions of the dynamic responses of a fully coupled hybridpiezoelastic cylindrical shell with piezoelectric shear actuators (PSAs). The fundamentalresponse quantities of each layer in the shell are expanded into a double Fourier series. Astate-space method is used to represent the response quantities using eight first-orderhomogeneous ordinary differential equations with variable coefficients. The solutions arethen obtained by the Frobenius method. Numerical examples are presented to show theeffects of thickness ratio and location of PSAs on the transverse response of the shellsubjected to mechanical and electric loadings. Finally, an active vibration control model fora simply supported laminated cylindrical shell with piezoelectric shear sensorand actuator layers is established using the negative velocity feedback controlstrategy. Numerical results are presented to verify the feasibility of the controlmodel.

A non-Standard shear resonator for the matrix characterization of piezoceramics and its validation study by finite element analysis

Standard shear samples used for piezoceramic characterization lead to underestimation of the piezoelectric shear coefficients due to its dynamical clamping at resonance. This work presents the application of Alemany et al's automatic iterative method to the resonance of a non-Standard shear sample, in order to determine the related complex parameters of piezoceramics, thus including losses, from impedance measurements. The matrix of dielectric, elastic and piezoelectric complex parameters that fully characterize a piezoceramic, a 6 mm symmetry material, can be obtained from such shear data combined with the application of the method to three other electromechanical resonances, namely: the length extensional mode of long rods or rectangular bars, length poled; the thickness extensional mode of a thin plate or disc, thickness poled; and the radial mode of a thin disc, thickness poled. The shear results obtained here are those of non-Standard samples of a commercial Navy type II piezoceramic, thus solving the underestimation of the coefficients in the Standard shear sample and allowing the improvement of the previously reported characteristic matrix from Standard samples. Three-dimensional finite element analysis (FEA) modelling of the resonances of the three material samples used in the matrix characterization was here accomplished using the improved matrix of dielectric elastic and piezoelectric material coefficients including all losses. The comparison of the experimental resonance spectra of these piezoceramic samples and the FEA results obtained for the elastically, dielectrically and piezoelectrically homogeneous items modelled is presented and discussed here.

Picturing the elephant: Giant piezoelectric activity and the monoclinic phases of relaxor-ferroelectric single crystals

Understanding the relationship between the structure and “giant” piezoelectric properties of relaxor ferroelectric solid solutions (1–x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 [PMN–xPT] and (1–x)Pb(Zn1/3Nb2/3)O3–xPbTiO3 [PZN–xPT] is an extremely difficult task. In this article, three main paradigms are reviewed. In the first, the monoclinic phases present at the morphotropic phase boundary (MPB) are responsible for the giant piezoelectric response in that they allow, or at least facilitate, polarization rotation. In the second, a strong polarization rotation effect is explained by the large piezoelectric shear coefficients of zero-field rhombohedral and orthorhombic phases due to the near degeneracy at the MPB and the intrinsic softness of the relaxor state; zero-field monoclinic symmetries are explained by residually distorted rhombohedral and orthorhombic phases in the presence of internal stresses and/or residual bias fields. In the third, the monoclinic “phases” are composed of very finely twinned rhombohedral or tetragonal domains. In this “adaptive phase” model, based on that for ferroelastic martensites, the large electric-field induced strains are extrinsic in nature and result from the progressive switching of the component “nano-twins”; the ease of polarization rotation is explained by a high domain wall mobility. These paradigms remain to be mutually reconciled. The article includes a thorough review of the history of PMN–xPT and PZN–xPT single crystals and, particularly, the most important work done over the last decade.

Ultrasonic torsional guided wave sensor for flow front monitoring inside molds

Measuring the extent of flow of viscous fluids inside opaque molds has been a very important parameter in determining the quality of products in the manufacturing process such as injection molding and resin transfer molding. Hence, in this article, an ultrasonic torsional guided wave sensor has been discussed for monitoring the movement of flow front during filling of resins in opaque molds. A pair of piezoelectric normal shear transducers were used for generating and receiving the fundamental ultrasonic torsional guided wave mode in thin copper wires. The torsional mode was excited at one end of the wire, while the flowing viscous fluid progressively wet the other free end of the wire. The time of flight of the transient reflections of this fundamental mode from the air-fluid interface, where the wire enters the resin, was used to measure the position of the fluid flow front. Experiments were conducted on four fluids with different viscosity values. Two postprocessing algorithms were developed for enhancing the transient reflected signal and for suppressing the unwanted stationary signals. The algorithms were tested for cases where the reflected signals showed a poor signal to noise ratio.

Induced shear actuation of helicopter rotor blade for active twist control

Induced shear based mechanism is used for attaining active twist in a soft-inplane hingeless rotor with a two-cell thin-walled airfoil section. The rotor properties dynamically represent a real rotor. A closed loop controller is developed to obtain the optimum voltage required to be given to the rotor blade for obtaining twist using strain rate feedback. Nonlinear relationship between piezoelectric shear coefficient and applied electric field is included in the controller design. Optimal placement of actuators lead to an overall vibration reduction of about 65%. Since thin-walled structures such as rotor blades are highly flexible and have strong aeroelastic effects, these effects on the loads and stability are thoroughly studied to evaluate the feasibility of the active twist rotor concept. No aeroelastic instabilities are found to occur due to active twist.