Magnetostrictive materials have attracted attention as materials for energy harvesting such as vibration power generation for Internet of Things (IoT). Fe-Co alloys have been focused on since the alloys have remarkable magnetic and mechanical properties. In this work, we evaluated the effect of heat treatment on the magnetic and magnetostrictive properties of rolled Fe-Co magnetostrictive films with Cr and Mo addition as bcc stabilizing elements to clarify. It was shown that the coercivity and the residual magnetism of the annealed specimens increase with the increase of the additive element quantity. This result indicates an increase in the amount of vibration power generation due to the Villari effect.
Carbon fiber reinforced plastic (CFRP) has been generally chosen in the areas where weight reduction is important, for instance, sports goods and aerospace. For safe operation of the system using CFRP, we have to assess the damage state and predict the remaining service life accurately, which is one of the critical issues to keep the reliability in CFRP applications. Recently, multi-functional CFRP, especially embedded with piezoelectric or magnetostrictive materials, has been explored to realize lightweight battery-free sensors for structural health monitoring (SHM). In present study, the hybrid CFRP embedded with magnetostrictive Fe-Co fibers was developed, and the effect of composite design parameters (e.g. diameter of the fibers, location of the layers, bias magnetic field) on the inverse magnetostrictive response characteristic was also investigated. Mechanical cyclic bending tests showed that the fluctuation of magnetic flux density was measured resulting from the flexural deformation of our hybrid CFRP. Moreover, the measured magnetic flux density changed drastically when the CFRP was damaged, which implies that our hybrid CFRP has damage self-sensing ability. It seems that we should experimentally and numerically design and investigate the hybrid CFRP with magnetostrictive Fe-Co fibers in order to improve the capability as sensor composite materials. Accordingly, this study must make contribution to feasibility of lightweight, buttery-free, high performance stress sensors for SHM.
As the development of Internet of Things (IoT), the power supply to the sensors in IoT becomes more and more important. The piezoelectric material was widely studied as a material for energy harvesting devices. Our target is to design and fabricate a flexible, eco-friendly and light functionally graded piezocomposite for energy harvesting devices by polyvinylidene fluoride (PVDF) and lead-free piezoelectric particles. Two kinds of lead-free piezoelectric particles -- barium titanate (BTO) and potassium sodium niobite (KNN) are used in the study. And the addition of the PVDF can greatly improve the toughness of the material and broaden the applications of the material. In this study, the multi-layer lead-free piezoelectric particle/PVDF composites with different contents of lead-free piezoelectric particles and structure are fabricated by spin coating and hot press method. The suitable parameters of the spin coating and hot press are found. The composites are polarized by corona poling method and optimal poling conditions of the composites are also studied. Scanning electron microscopic (SEM) observations are conducted to study the distribution of the particles in the matrix and the interface between the different layers. Then, the piezoelectric coefficient d33 is measured by a piezo-d33 meter. This study gives a workable fabrication method to the functionally graded piezocomposites and explores the piezoelectric properties of the composites which have potential to be used as energy harvesting device materials.
The inverse magnetostrictive response, known as the Villari effect, of magnetostrictive materials is a change in magnetization due to an applied stress. It is commonly used for sensor applications. This work deals with the inverse magnetostrictive characteristics of Fe-Co bimetal plates that were subjected gas-nitriding process. Gas-nitriding was performed on bimetal plates for 30 min at 853 K as a surface heat treatment process. The specimens were cooled to room temperature after completing the nitriding treatment. Three-point bending tests were performed on the plates under a magnetic field. The changes on the magnetic induction of the plates due to the applied load are discussed. The effect of the nitriding treatment on the inverse magnetostrictive characteristics, magnetostrictive susceptibility, and magnetic hysteresis loop was examined. Our work represents an important step forward in the development of magnetostrictive sensor materials.
The energy harvesting characteristics of piezoelectric/copper (BaTiO3/Cu) laminates rising from sharp temperature changes were investigated both numerically and experimentally. First, a phase field simulation was performed to determine the temperature-dependent piezoelectric coefficient and permittivity values. Then, the output voltages of the BaTiO3/Cu laminates were calculated for variations from room temperature to either a cryogenic temperature (77 K) or a higher temperature (333 K) using a 3D finite element simulation with the properties calculated from the phase field simulation. Finally, the output voltages of the piezoelectric BaTiO3/Cu laminates were measured for the same temperature changes and were compared to the simulation results.
We discuss the dynamic electromechanical behavior of barium titanate (BT) unimorph cantilevers with sensing, grounding and driving electrodes under alternating current (AC) electric fields. A three-dimensional finite element analysis (FEA) was performed to predict the deflection and output voltage in the BT unimorph cantilevers. The deflection and output voltage were also measured, and numerical results were compared with measured values. The deflection, output voltage and output power were then examined in detail.
KEYWORDS: Microsoft Foundation Class Library, Switching, Ferroelectric materials, Polarization, Electrodes, Finite element methods, Composites, Chemical elements, Epoxies, Current controlled current source
This work investigates the electromechanical response of piezoelectric macro-fiber composites (MFCs) under tension.
Nonlinear three dimensional finite element model incorporating the polarization switching mechanism was used to
predict the electromechanical fields near interdigitated electrode (IDEs) in the piezoelectric MFCs. The lead zirconate
titanate (PZT) fibers in the MFC are partially poled. The electric field-induced strain was then measured, and test results
were presented to validate the predictions.
This work presents the nonlinear bending response of magnetostrictive/piezoelectric laminated devices under
electromagnetic fields both numerically and experimentally. The devices are fabricated using thin Terfenol-D and PZT
layers. The magnetostriction of the Terfenol-D layer bonded to the PZT layer is measured, and a nonlinear finite element
analysis is performed to evaluate the second-order magnetoelastic constants in Terfenol-D layer using measured data.
The deflection, internal stresses and induced voltage/magnetic field for the laminated devices under magnetic/electric
fields are then discussed in detail.
This work presents the nonlinear bending response of magnetostrictive/piezoelectric laminated actuators under magnetic
fields both numerically and experimentally. The actuators are fabricated using thin Terfenol-D and PZT layers, and the
magnetostriction of the actuators is measured. A nonlinear finite element analysis is also performed to evaluate the
contribution of magnetic domain switching to the second-order magnetoelastic constants in Terfenol-D layer, and the
effect of magnetic field on the deflection, internal stresses and induced voltage for the magnetostrictive/piezoelectric
laminated actuators are discussed in detail.
The electromechanical field concentrations due to surface and internal electrodes in multilayer piezoelectric film
actuators are investigated through numerical and experimental characterization. A nonlinear finite element analysis is
carried out to discuss the effects of electric field and poling on the displacement and internal electromechanical fields in
fully and partially poled piezoelectric actuators, by introducing models for polarization switching. Displacement
measurements are also performed for the actuators, and a comparison of the predictions with experimental data is
conducted.
This paper presents the results of an analytical and experimental investigation in fatigue crack growth behavior of
piezoelectric ceramics under electromechanical loading. Static fatigue tests are performed in three-point bending with the
single-edge precracked-beam piezoelectric specimens under electric fields. Time-to-failure under different mechanical
loads and electric fields are measured, and the effect of applied electric fields on the energy release rate vs lifetime
curves are discussed, with combination with the finite element method. Cyclic crack growth tests are also conducted on
the same piezoelectric specimens under electric fields, and the fatigue crack growth rate vs maximum energy release rate
curves are examined.
This paper examines the dynamic electroelastic response of Rosen-type piezoelectric transformers in a combined experimental and numerical investigation. Experiments were performed to measure the electrical impedance and voltage gain at various frequencies. The finite element method was also used to solve the coupled electro-elastic boundary value problem. The electrical impedance and voltage gain were calculated and a comparison was made between experiment and simulation. The effects of load resistance and capacitance on the voltage gain and electroelastic field concentrations were also discussed.
The theory of dynamic antiplane piezoelectricity is applied to solve the problem of a circular piezoelectric inclusion embedded in an infinite piezoelectric matrix subjected to horizontally polarized shear waves and a steady-state inplane electrical load. The problem is formulated by means of the wave function expansion method. Numerical values on the dynamic stress and electric field concentrations are obtained, and the results are displayed graphically to exhibit the electroelastic interactions.
The electric fracture behaviour of a piezoelectric ceramic under applied electric fields has been discussed through experimental and theoretical characterizations. The single –edge precracked beam tests were performed on a commercial lead zirconate titanate ceramic. Mechanical loading was applied by the crosshead displacement control of the screw-driven electromechanical test machine. The fracture initiation loads under different electric fields are obtained from the experiment. It is shown that the crack opens less under a positive electric field (electric field in poling direction) than under a negative electric field. A finite element analysis was also employed to calculate the energy release rate and stress intensity factor, and to study the validity of the electrical boundary conditions at the crack surfaces to the permeable in piezoelectric material. An expression is presented for determining the fracture properties due to electrical effects by experimental and theoretical means. For a given displacement, the energy release rate is lower for positive electric fields and higher for negative electric fields. This is in agreement with the experimental findings. The numerical results under an applied force are in contrast to those under a constant displacement, and consistent with the relevant experimental results.
Following the theory of linear piezoelectricity, we consider the dynamic bending of a cracked composite plate with attached piezoelectric polyvinylidene fluoride layers subjected to electric field loading and incident flexural waves. The input waves are generated by a combination of bending moments applied to the plate edge causing the plates to vibrate in the transverse direction, and the electric field and the poling direction are perpendicular to the plate surfaces. Fourier transforms are used to reduce the mixed boundary value problem to the solution of a pair of dual integral equations. The integral equations are further reduce to a Fredholm integral equation of the second kind. Numerical results are given for the dynamic moment intensity factor versus frequency for several values of the electric field and the geometrical parameters.
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