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The cellulose fibers that form washi are longer than those of regular paper made from wood pulp. Hence, the mechanical properties of washi can be higher than those of conventional paper. This study evaluated the magnetic, magnetostrictive, and tensile properties of negative magnetostrictive cobalt ferrite (CoFe2O4) particle dispersed handmade washi (washi−CoFe2O4). The CoFe2O4 additives magnetized the washi, which displayed negative magnetostriction with the fiber direction perpendicular to the magnetic field and in the parallel fiber direction. Concerning the mechanical properties, the washi−CoFe2O4 displayed an elongation of up to 77% after yielding. [ABSTRACT FROM AUTHOR]

We investigated the effects of poling conditions on the piezoelectric performance of potassium sodium niobate [(K,Na)NbO3, KNN]/polymer composites, to obtain their unsteady energy harvesting potential. KNN nanoparticle/polymer composites were designed and fabricated and the poling condition test was performed. The composites were polarized using the corona poling method for various poling conditions and then the piezoelectric coefficient d33 was measured. It was found that piezoelectricity does not decrease over days. Scanning electron microscopic observations were conducted to study the distribution of the nanoparticles in the matrix. Meanwhile, the microstructure of the composites was studied by X-ray diffraction. Unsteady wind energy harvesting tests were accomplished to investigate the output voltage characteristics in the KNN nanoparticle/polymer composites in unsteady winds. The study represents an important step in developing flexible energy harvesters with stable performance. [ABSTRACT FROM AUTHOR]

The Internet of Things (IoT) requires power supplies without recharging. We conceived the idea of generating electricity from the impact of magnetostrictive materials against a propeller. This study evaluated the energy harvesting performance and energy storage capabilities of Fe–Co alloy and Ni clad (Fe–Co/Ni) films that directly strike propellers rotated by the wind in a duct airflow. The 0.08- and 0.2-mm-thick Fe–Co/Ni films generated powers of 28.1 and 89.4 µW, respectively. Moreover, the 0.08-mm-thick Fe–Co/No film generated power lower than that generated by the 0.2-mm-thick Fe–Co/Ni film. However, at a wind speed of 1.5 m/s, the 0.08-mm-thick Fe–Co/Ni film generated power, whereas the 0.2-mm-thick Fe–Co/Ni film stopped the rotation of propellers and did not generate any power. Furthermore, the Fe–Co/Ni film was successfully charged in a capacitor, and the stored voltages were 108.3 mV for the 0.08-mm-thick Fe–Co/Ni films for 30 min and 337.3 mV for the 0.2-mm-thick Fe–Co/Ni films for 1 h. It is also worth noting that no damage occurred to the surfaces of the Fe–Co/Ni films. [ABSTRACT FROM AUTHOR]

This paper studies the electromechanical response of multilayer piezoelectric actuators from room to high temperatures for fuel injector applications. A phenomenological model of depolarization at high temperatures was proposed, and the temperature dependent piezoelectric coefficients were obtained. The nonlinear electromechanical fields of the multilayer piezoelectric actuators due to the depolarization at high temperatures were then calculated by the finite element method. In addition, experimental results on the electric field induced strain at high temperatures were presented to validate the predictions. [ABSTRACT FROM AUTHOR]

A class of the magnetostrictive iron-cobalt/nickel clad plate cantilever is prepared in this study. The relevant ability for harvesting vibration energy is systematically investigated in comparison with the single iron-cobalt cantilever. In addition, the effects of the magnitude of bias magnetic field (i.e., external magnetic field) and the magnetization angle on the energy-harvesting performance are considered. The results indicated that the iron-cobalt/nickel clad plate cantilever exhibits far greater power generation compared with that of the single iron-cobalt cantilever. Besides, the iron-cobalt/nickel clad plate cantilever displayed high sensitivity to the magnitude of bias magnetic field and the magnetization angle. In more detail, the output voltage of the iron-cobalt/nickel clad plate cantilever peaks at a point even while the bias magnetic field constantly increases. A theory of dynamic balance can explain this phenomenon. Meanwhile, the resonance frequency of the iron-cobalt/nickel clad plate cantilever is proportional to the bias magnetic field due to the influence of the elastic modulus variation. This work provides insights into the exploration and design, not only of the vibration-energy-harvesting components but also of the sensitive detectors. [ABSTRACT FROM AUTHOR]

This paper examines theoretically and experimentally the electromechanical behavior of multilayer piezo-actuators for fuel injectors at cryogenic temperatures. A thermodynamic model was employed to predict a monoclinic phase. A shift in the morphotropic phase boundary (MPB) between the tetragonal and rhombohedral/monoclinic phases with decreasing temperature was determined, and the temperature dependent piezoelectric coefficients were obtained. Temperature dependent coercive electric field was also predicted based on the domain wall energy. A finite element analysis was then performed to calculate the nonlinear electromechanical fields of the multilayer piezo-actuators from room to cryogenic temperatures, due to the shift in the MPB and polarization switching. In addition, experimental results on the electric field induced strain, which verify the model, were presented. [ABSTRACT FROM AUTHOR]

This article describes the results of an analytical and experimental study of the effect of magnetic fields on the stress intensity factors in a soft ferromagnetic strip under uniaxial tension. The linear magneto-elastic problem for a soft ferromagnetic strip with a single-edge crack is analyzed. Fourier transform techniques are used to formulate the mixed boundary value problem as a singular integral equation. The stress intensity factors are obtained for several values of material and geometrical parameters, and magnetic field. Static experiments are also conducted on nickel–iron soft magnetic materials with a single-edge cracked plate specimen geometry in the bore of a superconducting magnet at room temperature. A strain gauge method is employed in experiments to determine the stress intensity factor. A comparison of the stress intensity factor is made between theory and experiment, and the agreement is good for the magnetic field considered. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental and numerical investigation in electric fracture behavior of composite [Pb(Zr,Ti)O3] double torsion (DT) specimens. DT tests were conducted on a commercial piezoelectric ceramic bonded between two metals. Fracture loads under different electric fields were obtained from the experiment. Nonlinear three-dimensional finite element analysis was also employed to calculate the energy release rate for DT specimens based on the exact (permeable) and approximate (impermeable) crack models. The effects of applied electric field and domain switching on the energy release rate are discussed, and the model predictions are compared with the results of the experiments. [ABSTRACT FROM AUTHOR]

This paper discusses the crack behavior of rectangular piezoelectric ceramics under electromechanical loading. A finite element analysis was employed to calculate the fracture mechanics parameters such as mode I energy release rate for the permeable, impermeable, and open crack models. Recently proposed nonlinear electrically discharging crack model was also considered. The effect of applied electric fields on the fracture mechanics parameters was then examined under various electrical boundary conditions at the crack face. [ABSTRACT FROM AUTHOR]

Energy harvesting technology is becoming increasingly important with the appearance of the Internet of things. In this study, a magnetostrictive clad steel plate for harvesting vibration energy was proposed. It comprises a cold-rolled FeCo alloy and cold-rolled steel joined together by thermal diffusion bonding. The performances of the magnetostrictive FeCo clad steel plate and conventional FeCo plate cantilevers were compared under bending vibration; the results indicated that the clad steel plate construct exhibits high voltage and power output compared to a single-plate construct. Finite element analysis of the cantilevers under bending provided insights into the magnetic features of a clad steel plate, which is crucial for its high performance. For comparison, the experimental results of a commercial piezoelectric bimorph cantilever were also reported. In addition, the cold-rolled FeCo and Ni alloys were joined by thermal diffusion bonding, which exhibited outstanding energy harvesting performance. The larger the plate volume, the more the energy generated. The results of this study indicated not only a promising application for the magnetostrictive FeCo clad steel plate as an efficient energy harvester, related to small vibrations, but also the notable feasibility for the formation of integrated units to support high-power trains, automobiles, and electric vehicles. [ABSTRACT FROM AUTHOR]