Longitudinal and transverse magnetoelectric voltage coefficients of magnetostrictive/piezoelectric laminate composite: experiments

Magnetostrictive Terfenol-D (Tb(x)Dy(1-x)Fe2) and piezoelectric (Pb(Zr(1-x)Ti(x))O3) magnetoelectric (ME) laminate composites have been investigated experimentally for various modes of operation: longitudinal magnetized/longitudinal polarized (L-L mode), transverse magnetized/longitudinal polarized (T-L mode), and transverse magnetized/transverse polarized (T-T mode) ME modes. We report their experimentally determined performance characteristics based on our previously developed equivalent circuits for these various modes. Predicted and experimental results are in agreement that the L-L mode laminates have enhanced ME effects, and that, under low or zero magnetic bias, the L-L mode ME voltage coefficients are up to a factor of 5-20x higher than those of the T-L mode or T-T mode laminates. The maximum ME voltage coefficient of the L-L mode laminates is over 86 mV/Oe under a bias of 500 Oe.     

Self-amplified magnetoelectric properties in a dumbbell-shaped magnetostrictive/piezoelectric composite

We report magnetoelectric (ME) properties in a dumbbell-shaped metallic glass alloy/Pb(Zr(x)Ti(1-x))O(3) laminated composite, yielding a magnetic field amplification resulting from magnetic flux concentration effects of the dumbbell-shaped design. Compared with the traditional rectangular structures, the modified geometry results in an effective improvement in the ME coefficient, a significant decrease in the required dc magnetic bias field, and an enhancement in magnetic field sensitivity.     

Design of magnetostrictive/piezoelectric laminate composite for coil-less magnetic force control

We propose a magnetic force control device consisting of laminate composites of magnetostrictive material and piezoelectric material. The magnetic force control is based on energy conversion in the composite, such that the variation of magnetization of the magnetostrictive material induced by the piezoelectric material is converted to the variation of magnetic force by magnetic circuits. Because of the capacitive property of the piezoelectric material, the device requires little current in order to maintain control of a constant force. The laminate composite can be fabricated easily and in small sizes. In this paper, we report the magnetic force control properties of a composite of Terfenol-D and piezoelectric material plates (PZTs) and discuss the design of the laminate composite. Our theoretical magnetic force formulation derived by an equivalent magnetic analysis and finite-element analysis of strain distribution in the Terfenol-D, and measurements with various thicknesses of PZT demonstrated that there are appropriate thicknesses to provide large variation of the magnetic force and energy conversion efficiency. Stacking the composites was found effective for increasing the effective area of the Terfenol-D.     

Influence of mechanical failure on the magnetoelectric response of magnetostrictive/piezoelectric multiferroic composite

Based on modified multi-field coupling equations, the magnetoelectric (ME) response of a new kind of Ni_47.4Mn_32.1Ga_20.5/PZT multiferroic composites are calculated by considering the mechanical failure of the brittle PZT substance. It is theoretically revealed that the Ni_47.4Mn_32.1Ga_20.5/PZT bilayer composites could produce an ideal giant ME (GME) response up to 120 V/cm Oe, much larger than the best reports up to now. However, the real ME response will be strongly limited by the mechanical strength of the brittle PZT. Reducing the PZT layer and using a mechanically stronger PZT material have been suggested to enhance the ME response.     

Dynamic response in magnetic force control using a laminate composite of magnetostrictive and piezoelectric materials

We investigate the dynamic response of a magnetic force control device composed of a laminate composite of magnetostrictive/piezoelectric material. The device exploits the inverse magnetostrictive effect of a magnetostrictive material so that the variation in the magnetization of the material, and hence the magnetic force in a magnetic circuit, can be controlled with a voltage to the piezoelectric material. Here, we compare the voltage-induced frequency responses of the admittance and flux (magnetic force) between the new device and a conventional electromagnet in order to identify the factors that degrade the response of the device. A finite-element calculation of the modal shape of the composite supports the observed correlation between the vibration of the composite and the flux in the gap in dynamic response.     

Piezomagnetic losses in bilayered magnetostrictive/piezoelectric composites: Effect of Terfenol-D content on the magnetoelectric susceptibility

This letter reports on the influence of piezomagnetic loss in magnetostrictive Terfenol-D (TeD)/polyurethane composite layer/piezoelectric PZT ceramic layer laminates on the phase shift between magnetoelectric current and ac magnetic field versus bias dc field. For a given low measurement frequency (1 kHz), piezomagnetic losses are predominant when the amount of TeD powder embedded in polyurethane is small (2 vol.%), inducing an imaginary magnetoelectric susceptibility and a 0° up to 180° variation of phase shift of magnetoelectric current. When TeD content is high enough (7 vol.%), piezomagnetic losses are almost null, which yields a real magnetoelectric susceptibility and a − 90° up to + 90° variation of phase angle of the current.     

Electromechanical analysis of a symmetric piezoelectric/elastic laminate structure: theory and experiment

The dynamic characteristics of a piezoelectric laminate cantilever structure treated as an actuator are analyzed by electroelasticity. General formulation of calculations for displacement sensitivity, electric current, electromechanical coupling coefficients, and results from parametric analyses are presented for axial expansion/contraction, transverse bending, and expansion/contraction-bending coupled motion. The frequency response of displacement and electrical current and the displacement sensitivity were experimentally measured. Close agreement between theoretical and experimental results confirms validity of the theory.     

Electromechanical analysis of an asymmetric piezoelectric/elastic laminate structure: theory and experiment

The electromechanical characteristics of an asymmetric piezoelectric/elastic laminated actuator are investigated by electroelasticity and experiments. The axial expansion-bending coupled motion of the system is separated into quasi-axial expansion and quasi-bending by its physical significance of vibration modes. General formulation of calculations for the mechanical, electrical, and electromechanical characteristics of the structure are presented via parametric analysis. Finally, the displacement sensitivity and the frequency response of displacement and electrical current are experimentally measured for this piezoelectric/elastic laminated specimen. Close agreement between theoretical and experimental results confirms the validity of the theory.     

Magnetic force control with composite of giant magnetostrictive and piezoelectric materials

We propose a new magnetic force control device, composed of a giant magnetostrictive material (Terfenol-D) and a piezoelectric material (PZT), for coilless magnetic force control. The device uses the inverse magnetostrictive effect, whereby the variation of magnetization of a Terfenol-D rod controlled by PZT is converted to the variation of magnetic force by a magnetic circuit. Because PZT is electrically capacitive, the method has the advantage of low power consumption and low heat generation in static operation. We have fabricated several devices with different geometrical shapes of the rods and magnetic yokes, and we describe their characteristics such as power consumption, heat generation, and response. We discuss a magnetic circuit design strategy that uses the /spl Delta/E effect in magnetostrictive materials to increase the energy conversion efficiency.     

Electromagneto-mechanical fields of giant magnetostrictive/piezoelectric laminates

This paper presents the nonlinear electromagneto-mechanical behavior of magnetostrictive/piezoelectric laminated pieces under magnetic fields both numerically and experimentally. The pieces are fabricated using thin Tb_0.3Dy_0.7Fe₂ (Terfenol-D) and Pb(Zr,Ti)O₃ (PZT) layers, and the magnetostriction of the pieces is measured. A nonlinear finite element analysis is also employed to evaluate the second-order magnetoelastic constants in Terfenol-D layer bonded to the PZT layer, and the nonlinear displacement, internal stresses and induced voltage for the magnetostrictive/piezoelectric laminated pieces under magnetic fields are discussed.     

Enhanced magnetoelectric effect in multiferroic composite beams due to flexoelectricity and transverse deformations

This paper is concerned with the exploration of the role of transverse normal and shear deformations on enhancing the magnetoelectric (ME) coefficient of multiferroic bilayer composite beams composed of a piezoelectric layer and a piezomagnetic layer. Analytical models have been derived based on the displacement field which accounts for both the transverse normal and shear deformations, Timoshenko beam theory and Euler Bernoulli beam theory. The induced flexoelectricity in the piezoelectric layer due to axial strain gradient and transverse shear strain gradient has also been taken into consideration for estimating the ME coefficient. It has been found that the contribution of transverse normal strain in the piezoelectric layer for enhancing the ME coefficient is significantly larger than that due to axial strain, transverse shear strain and flexoelectricity. For the particular values of the thicknesses of the piezoelectric layer and the piezomagnetic layer, the ME coefficient remains invariant for both thick and thin multiferroic composite beams.     

Longitudinal and transverse damage taxonomy in woven composite components

This work addresses the issue of micro-structural damage in the longitudinal direction of the woven during a deformation process, primarily in the tensile mode. This paper extends the insight into self-inflicted damage in dimensional multilayer woven composites subjected to uniaxial tensile and shear loading. Two composites made of multilayer woven architectures, hereby named: orthogonal and normal layer interlock forms the basis of this study. It identifies the physical characteristics which initiate the various damage modes, what these modes are and when they occur. This work complements the work already reported on the transverse direction in woven composites.     

Modeling of a rotary motor driven by an anisotropic piezoelectric composite laminate

This paper proposes an analytical model of a rotary motor driven by an anisotropic piezoelectric composite laminate. The driving element of the motor is a three-layer laminated plate. A piezoelectric layer is sandwiched between two anti-symmetric composite laminae. Because of the material anisotropy and the anti-symmetric configuration, torsional vibration can be induced through the inplane strain actuated by the piezoelectric layer. The advantages of the motor are its magnetic field immunity, simple structure, easy maintenance, low cost, and good low-speed performance. In this paper, the motor is considered to be a coupled dynamic system. The analytical model includes the longitudinal and torsional vibrations of the laminate and the rotating motion of the rotor under action of contact forces. The analytical model can predict the overall characteristics of the motor, including the modal frequency and the response of motion of the laminate, the rotating speed of the rotor, the input power, the output power, and the efficiency of the motor. The effects of the initial compressive force, the applied voltage, the moment of rotor inertia, and the frictional coefficient of the contact interface on the characteristics of the motor are simulated and discussed. A selection of the numerical results from the analytical model is confirmed by experimental data.     

Linear and quadratic magnetoelectric effect in CNMFO:PZT magnetoelectric composite

Dynamic magnetoelectric voltage measurements of 30 % Co_0.7?xNi_xMn_0.3Fe₂O₄:70 % Pb(Zr_0.52Ti_0.48)O₃ composites with x = 0.00, 0.05, 0.10, 0.15 synthesized by ceramic method were carried out by linear and quadratic method. Maximum linear magnetoelectric coefficient (α) of 14.7 mv Oe^?1 cm^?1 and maximum quadratic coefficient (β) of 2.26 × 10^?4 mv Oe^?2 cm^?1 were obtained for composition with x = 0.05. Maximum values of α and β for composition with x = 0.05 may be due to more connectivity between grains than in other compositions observed from scanning electron micrographs. Higher values of dielectric constant and ac conductivity for particular composition could also be possible reasons for maximum magnetoelectric coefficients. Smaller dielectric loss at higher frequencies was observed for the same composition which may result into less leakage of charges consequently increasing the resultant magnetoelectric coefficients.     

Characterization of electromechanical coupling coefficients of piezoelectric films using composite resonators

By analyzing the resonance frequency spectrum of a composite resonator consisting of a piezoelectric ceramic film deposited on a substrate plate, the thickness extensional mode electromechanical coupling coefficient of the film, k(t)(2), can be directly calculated from the effective coupling factor values, k(eff )(2), for two special modes of the resonator. The effects of the mechanical loss in the piezoelectric films on the measurement are investigated by numerical simulation, and some guidelines for improving the accuracy of the k(t)(2) measurement are reported.     

磁电复合结构磁场传感器灵敏度的电压调控研究

目的:实现外加激励电压调节磁电复合结构磁场传感器灵敏度的方法。方法:通过实验测量三层磁电复合结构磁电传感器,在压电调控层上施加不同电压时的磁电响应特性和灵敏度的变化。结果:无论是在静态还是在谐振状态,通过改变压电调控层的调控电压,均可以有效调节磁电传感器的灵敏度;在不同的谐振状态和不同的DC磁场段,外加调控电压调节传感器灵敏度变化的趋势不一样。特别是在共振频率为43 kHz的一阶弯曲共振模式,在调控电压变化400 V的范围内,传感器的灵敏度变化高达47.59%。结论:实验测量结果证实了压电调控层上外加调控电压调节磁电传感器灵敏度的可行性。     

Structural,magnetic and magnetoelectric properties of the magnetoelectric composite material

(x) CoFe₂O₄ + (1 ? x) Ba_0.9Sr_0.1TiO₃ magnetoelectric (ME) composites with x = 0.1, 0.2, 0.3, 0.4 and 0.5 were prepared by a conventional standard double sintering ceramic method. The magnetic and ME properties of composites consisting of cobalt ferrite (CoFe₂O₄) and barium strontium titanate (Ba_0.9Sr_0.1TiO₃) were investigated. The X-ray diffraction analysis was carried out to confirm the phases formed during sintering and also to calculate the lattice parameters. The hysteresis measurements were done to determine saturation magnetization (Ms), remanence magnetization (Mr) and coercivity (Hc) of the samples. The ME voltage coefficient (dE/dH)_H was studied as a function of intensity of the magnetic field. The measured ME response demonstrated strong dependence on the volume fraction of CoFe₂O₄ and the applied magnetic field. A large ME voltage coefficient of about 1,380 µV/cm/Oe was observed for 10 % CoFe₂O₄ + 90 % Ba_0.9Sr_0.1TiO₃ composite.     

Tensile behaviour of a niobium/alumina composite laminate

The tensile properties of a ceramic/metal laminate were examined. Alternating layers of niobium and alumina were fabricated into composite material and tensile tested at room temperature and 982 °C (1800 °F). The tensile behaviour of the laminate material was predicted using established models based on classical laminate theory. The estimated and measured properties showed excellent agreement. Relative to monolithic niobium, the composite material was found to have lower density and substantially higher stiffness.