Papers by Keyword: Piezoelectric Materials

Abstract: Energy harvesting has been at the forefront of research due to the significant interest in green energy sources, especially for powering remote sensors in structural health monitoring of coastal and offshore facilities. This work reports the magnet-actuated piezoelectric harvesters (M-APH) that use magnetic coupling to actuate piezoelectric film-embedded silicon rubber strips for energy harvesting from fluids. The piezo-silicon strips are deflected by the tip-magnets in the actuation system, such that the M-APH can effectively be triggered to generate electrical energy from vibration. The M-APH prototypes are printed using 3D printing technology, and the experiments are conducted to determine the output electrical voltage using a rectifier. Strip properties are varied to study the geometric influence (i.e., thickness and shape) on the energy performance. The electrical performance was evaluated for each curved piezoelectric strip and straight strips according to the piezoelectric material used. The reported M-APH can be applied to various fluids for energy harvesting.

Abstract: This paper shown and describe this behaviour an original conceptual design of an electrical transformer. The device it is constituted by an electrodynamic actuator and piezoelectric crystals.The input AC voltage generates an axial vibration in the electrodynamic actuator. The axial vibration is transmitted to a piezoelectric crystal which is polarized in the axial direction and generates the output voltage. In a reduced volumes and a single step, it would be possible to reach voltages of tens of MV and great transformation ratios-achieving these voltages is impossible with conventional systems-The transformer works at axial resonance of the piezoelectric crystal. This device operates to the frequency of order kHz; therefore could be used to generate electromagnetic waves. The capacitive and inductive at its output negligible respect conventional transformer. This transformer could be used in countless devices, such as gamma‐ray machines, electron microscope, solid-state propulsion system, Ion thruster, small particle accelerator etc.

Abstract: This study developed a novel full stressed energy harvester composed of a cantilever with varied thickness in the length direction to harvest energy from ambient vibrations. This harvester owns a higher efficiency of energy harvesting when compared with the harvester of a uniform cross section, since the maximum bending stress is constant in each cross section. The current available models for cantilever harvesters are inapplicable to the new improved fully stressed harvester due to its unique shape. By employing Rayleigh-Ritz method, a corresponding governing equation is hence developed to model the full stressed harvester for estimating the efficiency. The influence of the geometry on the generated electric power is also discussed for the full stressed harvester. The results show that the full stressed harvester can double the electric power generated by the uniform harvester, and the full stressed harvester has a lower natural frequency.

Abstract: Lead-free MnO doped 0.955K_0.5Na_0.5NbO₃-0.045Bi_0.5Na_0.5ZrO₃ (abbreviate as KNN-0.045BNZ) ceramics have been prepared by a conventional solid-state sintering method in a reducing atmosphere. The addition of MnO suppresses grain growth and eliminates the liquid phase. MnO dopant changes the crystalline structures of KNN-0.045BNZ ceramics from the classical Morphotropic Phase Boundary (MPB) with rhombohedral phase (R) and tetragonal phase (T) to the suppressed MPB with R/T phase. The 0.4% MnO doped KNN-0.045BNZ ceramics show an excellent electrical properties with quasi static piezoelectric constant d₃₃=300 pC/N, Curie temperature T_C = 350 °C, insulation resistivity ρ=4.83 × 10¹¹ (Ω・cm), and high field piezoelectric constants =438 pm/V (at E_max = 25 kV/cm). The results indicate that the 0.4%Mn doped KNN-0.045BNZ ceramic is a promising lead-free piezoelectric candidate material for commercial applications.

Abstract: Piezoelectric materials exhibit an electromechanical coupling which allows for their use assensors or energy harvesting devices (direct piezoelectric effect) or actuators and shape control de-vices (inverse piezoelectric effect). They are applied in many technological sectors of current interestsuch as the aerospace and automotive industries, and they are generally constructed in block form orin a thin laminated composite. The study of the integrity of such materials in their various forms andsmall sizes is still a challenge nowadays. To gain a better understanding of these systems, this workpresents a crack surface contact formulation which makes it possible to study the integrity of theseadvanced materials under more realistic crack surface multifield operational conditions. The formu-lation uses the BEM for computing the elastic influence coefficients and contact operators over theaugmented Lagrangian to enforce contact constraints on the crack surface, in the presence of electricfields. The capabilities of this methodology are illustrated solving a benchmark problem.

Abstract: Piezoelectric generator is a device used to convert mechanical energy into electrical energy. The basic element of the generator is made from piezoelectric material in which electrical energy is created as a result of deformations caused by reactions of mechanical structure of the generator. The amount of obtained electrical energy depends mainly on the piezoelectric material used, construction of the generator as well as a type of the source of mechanical energy. Construction of the generator is adjusted to the type of the source of mechanical energy. In order to obtain electrical energy from mechanical vibrations, the most frequent solution is beam structure. Effective electric energy generation by the piezoelectric generators depends on the following main factors: piezoelectric material used, generator structure, electronic system of the control and storage of energy, and the generator size. Generated by piezoelectric generators electric energy, can be used to power of miniaturized electronic devices with low power supply demand. The goal may be monitoring of the structure or industrial processes in hardly accessible places or/and in systems requiring the use of a big number of sensors. It will make cutting the operating costs possible and allow to create the eco-friendly technology without waste discharged batteries.

Abstract: Piezoelectric materials, which can couple electrical and mechanical displacements, are one of the most important functional materials nowadays. They comprises piezoelectric monocrystals, piezoelectric polycrystals (piezoelectric ceramics), piezoelectric polymers, and piezoelectric composites. Sensors made of these materials can convert pressure, acceleration, flow rate, etc. to surface charge (voltage) that can be easily processed, and at the same time generate their own energy instead of consuming it. Compared to other electromechanical transduction technologies, piezoelectric sensors have the advantages of high environmental and chemical stability, broad temperature and frequency band, as well as self-sufficiency. Piezoelectric materials can also be used in various applications such as energy harvesters, actuators, transducers, and capacitors. This paper reviews the piezoelectric materials and their recent application progress on sensors and others. These published results show the developing trend of piezoelectric sensors to become lead-free, flexible, and with high performance.

Abstract: The modified behavior of the phase transition temperatures (T_O-T and/or T_C) between orthorhombic (O), tetragonal (T) and cubic (C) that caused by doping Sb⁵⁺ in (Li_0.052Na_0.493K_0.455)(Nb_1-xSb_x)O₃ (LNKNS_x) ceramics was reported in the present investigation. The results show that differing from the insensitive T_O-T to the Sb⁵⁺ content, T_C splits into two peaks T_C^I and T_C^II when doping Sb⁵⁺. The decreased T_C^I by raising x may be ascribed to the Sb-rich grains and the settled T_C^II round 480 °C resulting from the Sb-lack ones. The enhanced piezoelectric coefficient d₃₃ value of 263 pC/N and planar mode electromechanical coupling coefficient k_p value of 42.5% at x=0.052 can be attributed to the polymorphic phase boundary (PPB) behavior with an appropriate ratio between T and O phases without any second phase.

Abstract: A three-dimensional boundary element methodology to study frictionless indentation response of piezoelectric (PE) materials is presented. The boundary element method (BEM) is used in order to compute the electro-elastic influence coeffcients of fully anisotropic piezoelectric solids. The proposed contact formulation is based on the augmented Lagrangian method presented in [33, 34, 35] and makes it possible to consider piezoelectric materials under different mechanical and electrical boundary conditions (i.e. insulating indenter and conducting indenter). The methodology is validated by comparison with theoretical solutions presented in the literature.

Abstract: This paper presents a numerical study on the influence of multimodal shunt circuit parameters in the flutter velocity of a typical section under an unsteady airflow. Flutter on typical sections is a kind of self-excited oscillation which can occur due to the interaction with the airflow. In the flutter point, when the critical dynamic pressure is reached, the vibrations of the typical section become unstable and increase fast and significantly in time. As a result, it can lead the structure to failure. Thus, it becomes important to investigate the possibility of reducing the effects of flutter in order to increase the reliability of composite structures during service. In this work, the aero-electromechanical dynamic model formulation is based on the Hamilton principle. The unsteady aerodynamic forces are calculated based on the linearized thin-airfoil theory, proposed by Theodorsen. The passive element responsible for the energy dissipation is a multimodal resonant shunt circuit in series topology, attached to a piezoelectric patch. An iterative solution algorithm is proposed to solve the resultant nonlinear eigenvalue problem. The optimum shunt tuning is firstly performed using Hagood and Flotow’s propositions; then, it is used an heuristic optimization algorithm, based on Differential Evolution. The preliminary results indicate that the flutter speed can be affected by the passive control, both in its mechanical aspect as electrical.