Number Of Piezoelectric Layers Research Articles

Modeling and electromechanical performance of improved smart aggregates using piezoelectric stacks

Smart aggregates (SAs) are often formed by embedding lead zirconate titanate (PZT) patches into concrete or marble blocks. They not only have the advantages of low cost, quick response, high reliability, and long service life, but also possess comprehensive actuating and sensing abilities, and have been widely used in structural health monitoring in the field of civil engineering. However, due to the plate-like geometry of the PZT patch and the limited number of layers, SAs have a relatively short sensing range. To solve this issue, a new type of SA using piezoelectric stacks was developed. Theoretical modeling of this new transducer was established, and prototypes were fabricated. Comparisons between the theoretical predictions and the experimental results are presented, and good agreement can be found. The effects of the key parameters, including the total height of the specimen, the elastic modulus of the cement, the radius of the piezoelectric stack, the thickness of the piezoelectric layer, and the number of piezoelectric layers in the piezoelectric stack, on the electromechanical properties were analyzed, and the guidelines for optimal design were presented. In addition, the improved and the traditional SAs were used to monitor the water content in soil specimens based on the electromechanical impedance technique. The results showed that the improved SAs using piezoelectric stacks are more sensitive than the traditional ones, and have good potential in structural health monitoring in the field of civil engineering.

Multi-layered BTO/PVDF nanogenerator with highly enhanced performance induced by interlaminar electric field

The flexible piezoelectric nanogenerator (PNG) has been spotlighted as a promising candidate for sustainable power source in wireless portable device. Here, a multi-layered BaTiO3 (BTO) /poly(vinylidene fluoride) (PVDF) PNG has been designed by spin coating and layer by layer assembled method. Benefited from the composite strategy and interlaminar electric field effect, the typical four-layered BTO/PVDF nanogenerator contained with 20 wt% BTO nanoparticles represents excellent output performance with voltage of 14.22 V (about 6.49 times than that of 1 layered PNG), current of 2.42 μA, and maximum power of 11.55 μW. The dielectric constant and residual polarization of the PNG vary with the number of piezoelectric layers, which is suspected as the root cause for the enhancement of piezoelectric and output performance. In addition, 4000 pressing-releasing cycles test, finger tapping and foot striking measurements also demonstrated excellent stability of the synthesized BTO/PVDF PNG, showing their great potential in wireless sensing and wearable device applications.

Band Structures Analysis of Elastic Waves Propagating along Thickness Direction in Periodically Laminated Piezoelectric Composites

Existing studies on elastic waves in periodically laminated piezoelectric structures mainly concerned the passive band properties, since the electrical boundaries in the considered structures cannot vary. This paper investigates the tuning of band properties of uncoupled primary and shear (P- and S-) waves along the thickness direction by actively varying the electrical field in periodically multilayered piezoelectric structures consisting of orthotropic materials. The alteration of the electrical field is realized in the multilayered unit cell here by either applying or switching four kinds of electrical boundary conditions, including the electric-open, applied electric capacitance, electric-short, and applied feedback voltage, to the constituent piezoelectric layer via the constituent electrode layers covering both its surfaces. First, the state space formalism is introduced to obtain the partial wave solution of any constituent orthotropic layer in the unit cell. Second, the traditional transfer matrix method is adopted to derive the dispersion equation of general, periodically laminated piezoelectric composites with unit cells consisting of an arbitrary number of piezoelectric layers with various boundaries and of elastic layers. Third, numerical examples are provided to verify the proposed analysis method, and to study the influences of electrode thickness as well as four electrical boundaries on the band structures. All the frequency-related dispersion curves are also illustrated by numerical examples to summarize the general dispersion characteristics of uncoupled P- and S-waves in periodically laminated piezoelectric composites. The main finding is that the innovative dispersion characteristic resulting from the negative capacitance may also be achieved via feedback control.

Research on a multi-layer piezoelectric structure applied in beam as a sensor

In this paper, a multi-layer piezoelectric structure (MPS) is designed as a sensor with multi-channel and high-output properties. It is bonded onto the surface of a cantilever, and then the FEM modeling and simulations are developed. The mathematical formulation of the model is based on the shear d eformation beam theory because of the large thickness of MPS. Furthermore, the FEM model is obtained based on the Hamilton's principle and the finite element method. The effects of some key parameters such as the number of piezoelectric layers, the thickness of per piezoelectric patch and that of per adhesive layer are analyzed on the sensing property of the MPS. Finally, a contrast experiment is also finished. The results have shown that this novel piezoelectric structure has a clear sensing advantage. It is helpful for designing the piezoelectric balance sensor or the piezoelectric vibration energy harvesting structure.

Parametric analysis of multilayered unimorph piezoelectric vibration energy harvesters

The use of a multilayer piezoelectric cantilever beam for vibration-based energy harvesting applications has been investigated as an effective technique to increase the harvested electrical power. It has been shown that the multilayered energy harvester performance is very sensitive to the number of layers and their electrical connection due to impedance variations. The objective of this work is to suggest a comprehensive mathematical model of multilayered unimorph piezoelectric energy harvester allowing analytical solution for the harvested voltage and electrical power. The model is used to deeply investigate the influence of different parameters on the harvested power. A distributed-parameter model of the harvester using the Euler–Bernoulli beam theory and Hamilton's principle is derived. Gauss's law is used to derive the electrical equations for parallel and series connections. A closed-form solution is proposed based on the Galerkin procedure and the obtained results are validated with a finite element 3D model. A parametric study is performed to ascertain the influence of the load resistance, the thickness ratio, the number of piezoelectric layers on the tip displacement and the electrical harvested power. It is shown that this model can be easily used to adjust the geometrical and electrical parameters of the energy harvester in order to improve the system's performances. In addition, it is proven that if one of the system's parameter is not correctly tuned, the harvested power can decrease by several orders of magnitude.

Models for designing radially polarized multilayer piezoelectric/elastic composite cylindrical transducers

The models for designing multilayer piezoelectric/elastic composite cylindrical transducers with two kinds of radial polarization directions are extended based on the typical sandwiched piezoelectric/elastic transducer, and their dynamic characteristics are performed. Based on the plane stress assumption, dynamic analytical solutions of the transducers subjected to an external harmonic voltage are derived, and the electric admittances are obtained. The effects of polarization directions, the inner radius of the transducers, the distance between two adjacent piezoelectric layers, the number of piezoelectric layers, and piezoelectric material types on the dynamic characteristics of the transducers are discussed. For some special cases, comparisons with other related investigations are also given, and good agreements are found. The present investigation provides a comprehensive understanding of multilayer piezoelectric/elastic composite cylindrical transducers, which have potential applications in the field of ultrasonic and underwater sound.

Static analysis of a multilayer piezoelectric actuator with bonding layers and electrodes

Based on the theory of piezoelasticity, an analytical solution for a typical multilayer piezoelectric composite cantilever is obtained by the Airy function method. The piezoelectric cantilever may consist of any number of layers. Moreover, the material and thickness for different layers may be different. The solution obtained in the present paper is concise and can be easily applied for the bending analysis of multilayer piezoelectric actuators considering the effect of bonding layers and electrodes. At last, a comprehensive parametric study is conducted to show the influence of electromechanical coupling (EMC), the number of piezoelectric layers, the elastic modulus of elastic layer and the thickness ratio on the bending behavior of actuators. Some interesting results for the design of multilayer piezoelectric actuators are presented.

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.

Control of Smart Laminated FRP Structures using Artificial Neural Networks

This paper deals with the vibration control of smart laminated fiber-reinforced plastic (FRP) composites using back propagation neural networks (BPNNs). To simulate the system dynamics, a finite element model for smart layered FRP composites is developed, which could incorporate any number of piezoelectric layers in addition to the usual composite layers. To control the vibrations of smart FRP laminated composites, BPNN has been used. Sensing and actuation are achieved by the piezoelectric sensors and actuators. The active vibration control performance of beams/plates with piezoelectric sensors and actuator layers is studied using this model. It has been observed that the use of neural network can control the displacement reasonably well.

Optimization of Signal-to-Noise Ratio for Multilayer Pzt Transducers

In medical ultrasound imaging, two-dimensional (2-D) array transducers are desirable to implement dynamic focusing and phase aberration correction in two dimensions as well as volumetric imaging. Unfortunately, the small size of a 2-D array element results in a small clamped capacitance and a large electrical impedance near the resonance frequency. This results in poor signal-to-noise ratio (SNR) of the array elements. It has previously been demonstrated that transducers made from multilayer PZT ceramics have lower electrical impedance and greater SNR than comparable single layer elements. A simplified circuit model has been developed to optimize the SNR for multilayer ceramic (MLC) transducers. In this model, an electronic transmitter excites the array element and in the receive mode, the element drives a coaxial cable load terminated by a high impedance preamplifier. The transducer impedance is Zt/N2, where N is the number of piezoelectric layers. Maximum transmit signal is obtained when N = Ntx such that the transducer impedance, Zt/Ntx2, is matched to the source impedance. Maximum receive signal is obtained when N = Nrx such that the transducer impedance, Zt/Nrx2, is matched to the coaxial cable reactance. For maximum pulse-echo signal, the transducer should be designed with N = square root of Ntx Nrx, the geometric mean of Ntx and Nrx. Using this optimization technique, a 1.5-D array was designed with 3 layers for maximum pulse-echo SNR. Results of simulations from the simplified circuit analysis were consistent with those of the KLM model. The 3 layer array was fabricated as well as a single layer control array. The measured transmit signal and receive signal agreed with the simulation results.

Optimization of Signal-to-Noise Ratio for Multilayer PZT Transducers

In medical ultrasound imaging, two-dimensional (2-D) array transducers are desirable to implement dynamic focusing and phase aberration correction in two dimensions as well as volumetric imaging. Unfortunately, the small size of a 2-D array element results in a small clamped capacitance and a large electrical impedance near the resonance frequency. This results in poor signal-to-noise ratio (SNR) of the array elements. It has previously been demonstrated that transducers made from multilayer PZT ceramics have lower electrical impedance and greater SNR than comparable single layer elements. A simplified circuit model has been developed to optimize the SNR for multilayer ceramic (MLC) transducers. In this model, an electronic transmitter excites the array element and in the receive mode, the element drives a coaxial cable load terminated by a high impedance preamplifier. The transducer impedance is Z t/N 2, where N is the number of piezoelectric layers. Maximum transmit signal is obtained when N = N tx, such that the transducer impedance, Z t/N tx 2, is matched to the source impedance. Maximum receive signal is obtained when N = N rx such that the transducer impedance, Z t/N rx 2 is matched to the coaxial cable reactance. For maximum pulse-echo signal, the transducer should be designed with N = [formula] the geometric mean of N tx and N rx. Using this optimization technique, a 1.5-D array was designed with 3 layers for maximum pulse-echo SNR. Results of simulations from the simplified circuit analysis were consistent with those of the KLM model. The 3 layer array was fabricated as well as a single layer control array. The measured transmit signal and receive signal agreed with the simulation results.