Piezoelectric Shear Research Articles

A 3-DOF Multi-Mode spherical actuator driven by cooperative piezoelectric units

Stick-slip piezoelectric actuators are widely used in precision engineering due to their high accuracy and small size. However, most of these actuators achieve multi-DOF motion by serially connecting multiple units, resulting in a non-compact structure and large assembly errors.To resolve this issue, this paper proposes a spherical actuator consists of a rotor and four drive units distributed around the rotor. Each drive unit comprises a piezoelectric shear stack and a piezoelectric plate. By utilizing the cooperation of piezoelectric elements, various driving modes with different performance and control complexity can be switched. To understand the influence of position and orientation of the drive units on the actuator’s performance, a dynamic model describing the behavior of the proposed actuator is established. This model takes into account the behavior of the drive units, friction and motion transmission between the drive units and the rotor, as well as transformation of coordinates. Finally, a prototype is developed based on the design, and the three-DOF motion performance of the prototype is tested under different drive modes. This work contributes to the mechanical design of multi-DOF precision positioning devices and the study of motion modes.

Piezoelectric Yield of Single Electrospun Poly(acrylonitrile) Ultrafine Fibers Studied by Piezoresponse Force Microscopy and Numerical Simulations.

Quantitative converse piezoelectric coefficient (d33) mapping of polymer ultrafine fibers of poly(acrylonitrile) (PAN), as well as of poly(vinylidene fluoride) (PVDF) as a reference material, obtained by rotating electrospinning, was carried out by piezoresponse force microscopy in the constant-excitation frequency-modulation mode (CE-FM-PFM). PFM mapping of single fibers reveals their piezoelectric activity and provides information on its distribution along the fiber length. Uniform behavior is typically observed on a length scale of a few micrometers. In some cases, variations with sinusoidal dependence along the fiber are reported, compatibly with a possible twisting around the fiber axis. The observed features of the piezoelectric yield have motivated numerical simulations of the surface displacement in a piezoelectric ultrafine fiber concerned by the electric field generated by biasing of the PFM probe. Uniform alignment of the piezoelectric axis along the fiber would comply with the uniform but strongly variable values observed, and sinusoidal variations were occasionally found on the fibers laying on the conductive substrate. Furthermore, in the latter case, numerical simulations show that the piezoelectric tensor's shear terms should be carefully considered in estimations since they may provide a remarkably different contribution to the overall deformation profile.

Characterizing the electric field- and rate-dependent hysteresis of piezoelectric ceramics shear motion with the Bouc-Wen model

Piezoelectric technology is widely used in the field of precision drives. However, when piezoelectric actuators are employed at high voltages and high frequencies, their hysteresis can greatly affect the accuracy of such systems. The Bouc-Wen model has typically been used by researchers to characterise the hysteresis of piezoelectric materials. Besides, to extract the parameters of this model from experimental data, particle swarm optimization (PSO) is often employed. However, the majority of such studies only considers hysteresis as a function of the electric field strength and not as a function of actuation frequency. In addition, most of such existing reports have focused on longitudinal type piezo actuators. In this context, the research presented here complements this body of knowledge by demonstrating the application of the PSO algorithm for determining the parameters of the Bouc-Wen model when hysteresis depends not only on the electric field but also on the rate of the driving signal and when applied on a shear-type piezoelectric actuator. The obtained experimental data showed that with the increase of electric field strength, both the piezoelectric coefficient and hysteresis value increased significantly, and that with the increase of frequency, the piezoelectric coefficient decreased, while the hysteresis value changed slightly. The variations of the Bouc-Wen model parameters with the electric field and frequency were identified and then used to predict the shear motion trajectory of the piezoelectric stack. It was found that in the identified range of electric field and frequency, the predicted error rate of the hysteresis loop amplitude was less than 16.5% with a minimum value of 0.1%, and the error rate of the hysteresis loop width was less than 14.5% with a minimum value of 2.7%. Based on the identified electric field- and rate-dependent Bouc-Wen model, a novel finite element (FE) model was also proposed to analyse the effect of electrical and mechanical coupling on the piezoelectric movement.

Development and analysis of magnet-engaged piezoelectric energy generator under friction-induced vibration

Piezoelectric energy transducers, which can be an efficient solution for the power supply of wireless devices, have been widely researched. This study investigated the characteristics of a magnet-engaged nonlinear piezoelectric energy generator stimulated by friction-induced vibration (FIV), in two distinct design configurations (in-parallel and in-series). A mathematical model was developed, and the dynamic response of the mechanical system and voltage output from the piezoelectric shear deformation were solved using an iterative method. A friction model considering the Stribeck effect was introduced to describe the friction motion. The emergence of a stick-slip motion induced limit cycle and its vanishing delineates the unstable and stable regions of the system, respectively. A critical sliding velocity vc splits the regions. When the sliding velocity exceeds vc, the system remains in stable region with exclusive slip friction behavior. Parameter studies were conducted to explore the effect of decay factor β, dynamic friction coefficient μk, static friction coefficient μstatic, and normal force FN on vc. The results indicate that increasing β and μk can reduce the unstable region and generation of FIV, whereas, increasing FN and μstatic can promote the occurrence of FIV. The energy generation was evaluated by a transient charging simulation that has been experimentally validated in a previous study. The influence of β, μk, μstatic, and FN on the energy generation was also investigated relative to the operating velocity range (OVR) and sum of root mean square charging power (SRCP). The in-parallel systems exhibit a higher SRCP within the same OVR, whereas the in-series systems are more likely to excite FIV with a wider OVR. Additionally, the simulation results of fluctuating working conditions show that both fluctuating FN and v0 have negative effects on the energy generation. The nonlinear in-series system exhibits better robustness with the least affected SRCP and almost unchanged OVR under fluctuating FN and v0.

Architected Piezoelectric Metamaterial With Designable Full Nonzero Piezoelectric Coefficients

Abstract Piezoelectric metamaterials have received extensive attention in the fields of robotics, nondestructive testing, energy harvesting, etc. Natural piezoelectric ceramics possess only five nonzero piezoelectric coefficients due to the crystal symmetry of ∞mm, which has limited the development of related devices. To obtain nonzero piezoelectric coefficients, previous studies mainly focus on assembling piezoelectric ceramic units or multiphase metamaterials. However, only part of the nonzero piezoelectric coefficients or locally piezoelectric electromechanical modes are achieved. Additionally, it still remains a challenge for manipulating the piezoelectric coefficients in a wide range. In this work, full nonzero piezoelectric coefficients are obtained by symmetry breaking in the architected piezoelectric metamaterial. The piezoelectric coefficients are designable over a wide range from positive to negative through manipulating the directions of each strut for the three-dimensional architected lattice. The architected metamaterials exhibit multiple positive/inverse piezoelectric modes, including normal and shear deformation. Finally, a smart gradient architected piezoelectric metamaterial is designed to take advantage of this feature, which can sense the position of the normal and shear force. This work paves the way for the manipulation of piezoelectric metamaterial in a wide range with designable full nonzero piezoelectric coefficients, thereby enabling application potential in the fields of smart sensing and actuation.

Piezoelectric shear rheometry: Further developments in experimental implementation and data extraction

The piezoelectric shear gauge (PSG) [Christensen and Olsen, Rev. Sci. Instrum. 66, 5019 (1995)] is a rheometric technique developed to measure the complex shear modulus of viscous liquids near their glass transition temperature. We report recent advances to the PSG technique: (1) The data extraction procedure is optimized, which extends the upper limit of the frequency range of the method to between 50 and 70 kHz. (2) The measuring cell is simplified to use only one piezoelectric ceramic disk instead of three. We present an implementation of this design intended for liquid samples. Data obtained with this design revealed that a soft extra spacer is necessary to allow for thermal contraction of the sample in the axial direction. Model calculations show that flow in the radial direction is hindered by the confined geometry of the cell when the liquid becomes viscous upon cooling. The method is especially well-suited for—but not limited to—glassy materials.

Block symmetric-triangular preconditioners for generalized saddle point linear systems from piezoelectric equations

Based on the symmetric-triangular (ST) decomposition technique, a class of block ST (BST) preconditioners are proposed for generalized saddle point linear systems arising from the meshfree discretization of piezoelectric equations. By applying the BST preconditioners, we first transform the generalized saddle point linear systems into symmetric positive definite ones, which then can be solved in a fast and efficient way by the classical conjugate gradient (CG) or the preconditioned CG (PCG) iteration methods. Two practical BST preconditioners are presented and analyzed in detail. Eigen-properties and upper bounds of the condition numbers of the preconditioned matrices are proved. Implementation aspects are discussed. Finally, two numerical experiments arising from the piezoelectric strip shear deformation problem and the piezoelectric strip bending problem are presented. Numerical results show that the iteration steps of the PCG methods are independent of the number of degrees of freedom and the proposed BST preconditioners perform much better than some existing preconditioning techniques.

Electrical Power Generation Using Dynamic Piezoelectric Shear Deformation Under Friction

A new electrical power generation device based on high-frequency dynamic piezoelectric shear deformation under friction is developed. During the operation of a moving plate compressed and sliding on the top of a piezoelectric patch with constant velocity, dynamic shear deformation of the elastic piezoelectric patch is excited by periodic friction force and status (sliding and stick) variation. The dynamic piezoelectric shear strain can then generate continuous electrical power for energy absorbing and harvesting applications. The design of the piezoelectric couple device is first provided, and its mechanism, dynamic response and electric power generation under friction are described by a detailed iteration model. By comparing with previous experimental results, the accuracy of the proposed model is proven. Through numerical studies, the influences of the equivalent mass of the system, the velocity of the sliding object, the static friction coefficient and its lower limit, as well as the friction force delay rate on the power generation are obtained and discussed. The numerical results show that with the proposed design, up to 50-Watt maximum electrical power could be generated by a piezoelectric patch with a dimension of 20times 2times 6 cm under continuous friction with the moving plate at the velocity of 15 m/s. The possible bi-linear elastic stiffness variation of the system is also introduced, and the threshold of bi-linear elastic deformation, where the system stiffness changes, can be optimized for obtaining the highest power generation.

Parameter Identification of the Nonlinear Piezoelectric Shear d15 Coefficient of a Smart Composite Actuator

The objective of this work is to characterize the nonlinear dependence of the piezoelectric d15 shear coefficient of a composite actuator on the static electric field and include this effect in finite element (FE) simulations. The Levenberg-Marquardt nonlinear least squares optimization algorithm implemented in MATLAB was applied to acquire the piezoelectric shear coefficient parameters. The nonlinear piezoelectric d15 shear constant of the composite actuator integrated with piezoceramic d15 patches was obtained to be 732 pC/N at 198 V. The experimental benchmark was simulated using a three-dimensional piezoelectric FE model by taking piezoelectric nonlinearity into consideration. The results revealed that the piezoelectric shear d15 coefficient increased nonlinearly under static applied electric fields over 0.5 kV/cm. A comparison between the generated transverse deflections of the linear and nonlinear FE models was also performed.

Cell‐by‐cell approximate Schur complement technique in preconditioning of meshfree discretized piezoelectric equations

AbstractThe radial point interpolation meshfree discretization is a very efficient numerical framework for the analysis of piezoelectricity, in which the fundamental electrostatic equations governing piezoelectric media are solved without mesh generation. Due to the mechanical‐electrical coupling property and the piezoelectric constant, the discrete linear system is sparse, of generalized saddle point form and often very ill conditioned. In this work, we propose a technique for constructing a family of cell‐by‐cell approximate Schur complement matrices, to be used in preconditioning to accelerate the convergence of Krylov subspace iteration methods for such problems. The approximate Schur complement matrices are simply and cheaply constructed in the process of the meshfree discretization and have a sparse structure. It is proved that the so‐constructed approximate Schur complement matrices are spectrally equivalent to the exact Schur complement matrix, which leads to very fast convergence when used in preconditioning. In addition, nondimensionalization of the piezoelectric equations is considered to make the computations more stable. The robustness and the efficiency of the proposed preconditioners is illustrated numerically on two test problems, arising from a piezoelectric strip shear deformation problem and a piezoelectric strip bending problem. Numerical results show that the number of iterations to achieve a given tolerance is independent of the number of degrees of freedom as well as of the various problem parameters.

High sensitivity face shear magneto-electric composite array for weak magnetic field sensing

A magnetic field sensor is designed and fabricated using a piezoelectric face shear mode Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT)/Metglas magneto-electric (ME) composite. An outstanding ME coupling coefficient up to 1600 V/(cm Oe) was experimentally achieved, being ∼50% higher than the value from the extensional PMN–PT/Metglas ME composite with the same volume. The detection limit was found to be 2 × 10−6 Oe for the DC magnetic field, while it was 2 × 10−8 Oe for the AC magnetic field. The sensitivity of the face shear mode PMN–PT/Metglas ME composite is about one order of magnitude higher than that of a 32 extensional mode PMN–PT/Metglas based ME composite in sensing a weak DC magnetic field. A sensing array was also designed based on the ME composite to image weak DC magnetic fields, demonstrating a great potential promising for sensing weak magnetic fields.

ESTRUCTURAS BASADAS EN POZOS CUÁNTICOS ANALIZADAS POR FOTORREFLECTANCIA ANISOTRÓPICA A TEMPERATURA AMBIENTE

We report the visualization of interface optical anisotropies in III-V semiconductor based coupled double quantum wells by using photoreflectance anisotropy spectroscopy. Interfacial optical anisotropies were detected from buried layers with quantum dimensions at room temperature through a piezoelectric shear strain. The discrete transitions associated to coupled double quantum wells were observed in near-infrared range, specifically in the second telecommunication band. We propose to use this extended photoreflectance spectroscopy through a polarization contrast as a simple and complementary optical method for analyzing anisotropic quantum structures with polarizable defects or anti-symmetries.

High Volume Production of PZT Fiber Arrays for Direct Functional Integration into Metal Structures

A new concept for electromechanical coupling of piezoceramic to metal structures is enabled with the technology of joining by forming. This approach allows for the manufacturing of so‐called piezo‐metal modules. To make the manufacturing process ready for series production, it is necessary to fabricate lead zirconate titanate (PZT) fiber arrays with high geometric accuracy. In addition, the aim is to design the PZT fiber arrays so that they are usable with either piezoelectric transversal, longitudinal, or shear mode to enable different application options. In particular, the realization of the shear mode offers new application potentials in comparison to commercially available products. This paper presents both, a high volume production method, and the specific order for the production steps of PZT fiber arrays to achieve the different piezoelectric modes. In particular, the usable piezoelectric effects are determined by the order of the coatings of electrode and insulating layers as well as the direction of the polarization. Experimentally produced samples are tested in functional tests before and after the joining by forming process. The results verify the proof of the production method of PZT fiber arrays with a high accuracy. Furthermore, structurally integrated PZT fiber arrays demonstrate the functional use of the three piezoelectric modes in the plane of an aluminum sheet. Fabricated piezo‐metal modules with transversal mode and shear mode are successfully verified in sensory function. The longitudinal mode is tested in actuator function. During the tests, failures for the insulation layer are identified. These can be eliminated with a modified manufacturing process, which is proposed.

A multilayered-cylindrical piezoelectric shear actuator operating in shear (d15) mode

In this work, a multilayered-cylindrical piezoelectric shear actuator (MCPSA) operating in the d15 shear mode was presented for precision actuation under a large mechanical load. The actuator was made of Pb(Zr,Ti)O3 (PZT-51) piezoelectric ceramic rings, which were concentrically assembled together in electrically parallel connection with alternately positive and negative polarizations along the axial direction. Experimental results show that the acquired displacement amplitude at the center of the actuator along the axial direction is around 6.5 μm under the 1 Hz applied voltage of 400 Vpp/mm, and it stayed stably under a mechanical load up to 18 N, which is 7 times larger than that of the previously reported d15 shear actuator. The proposed actuator also shows good displacement linearity with a high resolution of 0.1 μm in responding to a step voltage, indicating its great potential for precision actuation under a large mechanical load.

Thermo-electro-radial coupling nonlinear instability of piezoelectric shear deformable nanoshells via nonlocal elasticity theory

In the present article, the size-dependent nonlinear thermo-electro-mechanical instability of piezoelectric nanoshells under a combined action of hydrostatic pressure, lateral electric field and uniform changes in temperature is examined in the presence of the geometric imperfection sensitivity. The non-classical formulations given herein are built upon the nonlocal continuum elasticity within the framework of the shear deformation shell theory incorporating von Karman nonlinearity due to large deflection. The nonlocal-based governing equations are constructed based on the minimum potential energy of the system and then they are deduced using boundary layer theory of shell buckling. By applying an efficient perturbation-based solution methodology, closed-form solutions including explicit expressions are extracted for nonlocal postbuckling equilibrium paths of thermo-electro-mechanical excited piezoelectric nanoshells. It is displayed that for the both local and nonlocal shell models, the lateral applied electric fields with positive and negative signs induce, respectively, initial contraction and expansion in the piezoelectric nanoshell which causes in order to increase and decrease the critical shortening relevant to the electro-radial instability of piezoelectric nanoshell.

Dual Actuation of Fast Scanning Axis for High-speed Atomic Force Microscopy

In order to overcome the limiting trade-off between the imaging speed and scanning range of an atomic force microscope (AFM), this paper combines two piezoelectric actuators as a dual stage actuator (DSA) for a lateral motion (X axis) of the AFM probe with respect to the sample. As the first actuator, a piezoelectric tube actuator of the commercial AFM is utilized. Although the actuator realizes a relatively large actuation range, it has the first mechanical resonance at a low frequency of 2.5 kHz. In the case of high-speed imaging, this resonance impairs the imaging speed and quality. In order to overcome this, a piezoelectric shear actuator with the first resonance at 19 kHz is selected as the second actuator, combined in the commercial AFM. To generate the X-axis motion by synchronizing those two actuators, this paper proposes a feedforward control design for DSAs in the frequency domain, which takes into account the actuator dynamics. In the proposed approach, triangular raster scan is composed as a Fourier series by individually adjusting the complex Fourier coefficients for each actuator. The effectiveness of the DSA and its control is validated by experimental AFM imaging at a scan rate of 200 Hz, where the lowest frequency component is applied to the tube actuator and the other higher components of the scanning signal to the high-speed shear actuator.

Study of the Relation between the Resonance Behavior of Thickness Shear Mode (TSM) Sensors and the Mechanical Characteristics of Biofilms.

This work analyzes some key aspects of the behavior of sensors based on piezoelectric Thickness Shear Mode (TSM) resonators to study and monitor microbial biofilms. The operation of these sensors is based on the analysis of their resonance properties (both resonance frequency and dissipation factor) that vary in contact with the analyzed sample. This work shows that different variations during the microorganism growth can be detected by the sensors and highlights which of these changes are indicative of biofilm formation. TSM sensors have been used to monitor in real time the development of Staphylococcus epidermidis and Escherichia coli biofilms, formed on the gold electrode of the quartz crystal resonators, without any coating. Strains with different ability to produce biofilm have been tested. It was shown that, once a first homogeneous adhesion of bacteria was produced on the substrate, the biofilm can be considered as a semi-infinite layer and the quartz sensor reflects only the viscoelastic properties of the region immediately adjacent to the resonator, not being sensitive to upper layers of the biofilm. The experiments allow the microrheological evaluation of the complex shear modulus (G* = G′ + jG″) of the biofilm at 5 MHz and at 15 MHz, showing that the characteristic parameter that indicates the adhesion of a biofilm for the case of S. epidermidis and E. coli, is an increase in the resonance frequency shift of the quartz crystal sensor, which is connected with an increase of the real shear modulus, related to the elasticity or stiffness of the layer. In addition both the real and the imaginary shear modulus are frequency dependent at these high frequencies in biofilms.

Thermo-electro-mechanical size-dependent postbuckling response of axially loaded piezoelectric shear deformable nanoshells via nonlocal elasticity theory

The current study addresses the size-dependent nonlinear thermo-electro-mechanical instability of piezoelectric nanoshells under a combined action of axial compressive load, lateral electric field and uniform changes in temperature. The non-classical formulations given herein are built upon the nonlocal elasticity theory within the framework of the shear deformation shell theory. On the basis of the minimum potential energy of the system and using a boundary layer theory of shell buckling, the nonlocal-based governing equations are deduced incorporating the nonlinear prebuckling deformations and initial geometric imperfection sensitivity. After that, a perturbation-based solution methodology is put to use in order to anticipate the size-dependent thermo-electro-mechanical postbuckling response of piezoelectric nanoshells corresponding to different nonlocal parameters, applied electric voltages and temperature changes. It is displayed that for the both local and nonlocal models with and without initial geometric imperfection, a lateral electric field coming from a positive applied voltage leads to increase the axial stiffness of piezoelectric nanoshell in such a way that the critical load and width of postbuckling domain increase, but no considerable change occurs in the minimum load of the postbuckling regime.

Piezoelectric d36 in-plane shear-mode of lead-free BZT-BCT single crystals for torsion actuation

We report the study of piezoelectric direct torsion actuation mechanism using lead-free piezoelectric d36 in-plane shear-mode BZT-BCT single crystals. The generated angle of twist of the piezoelectric torsion actuator was obtained from the transverse deflection measurement using a laser vibrometer. The bi-morph torsional actuator, consisting of two lead-free piezoelectric BZT-BCT in-plane shear-mode single crystals with a giant piezoelectric d36 shear strain coefficient of 1590 pC/N, provided a rate of twist of 34.12 mm/m under a quasi-static 15 V drive. The experimental benchmark was further modelled and verified by the ANSYS software using three dimensional (3D) piezoelectric finite elements. The experimental results revealed that lead-free piezoelectric BZT-BCT d36-mode single crystal is a superior candidate for piezoelectric torsion actuation. This lead-free piezoelectric BZT-BCT d36-mode torsion actuator can be effectively applied in torsional deformation control by taking into account the environmental considerations.

Enhanced torsional actuation and stress coupling in Mn-modified 0.93(Na0.5Bi0.5TiO3)-0.07BaTiO3 lead-free piezoceramic system

This paper is concerned with the development of a piezoelectric d15 shear-induced torsion actuator made of a lead-free piezoceramic material exhibiting giant piezoelectric shear stress coefficient (e15) and piezoelectric transverse shear actuation force comparable to that of lead-based shear-mode piezoceramics. The Mn-modified 0.93(Na0.5Bi0.5TiO3)-0.07BaTiO3 (NBT-BT-Mn) composition exhibited excellent properties as a torsional transducer with piezoelectric shear stress coefficient on the order of 11.6 C m–2. The torsional transducer, consisting of two oppositely polarized NBT-BT-Mn d15 mode piezoceramic shear patches, provided a rate of twist of 0.08 mm m–1 V–1 under quasi-static 150 V drive. The high value of piezoelectric shear d15 coefficient in NBT-BT-Mn sample further demonstrated its potential in practical applications. These results confirm that the lead-free piezoceramics can be as effective as their lead-based counterparts.