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The giant magnetostrictive transducer is a transducer device that realizes magneto-mechanical energy conversion. Each mechanical component is connected by the joint surface to realize the transmission of ultrasonic vibration energy. To ensure the efficient transmission of energy, the influence of the contact characteristics of the joint surface on the output stability of the transducer is studied. According to the contact conditions between the mechanical joint surfaces of the giant magnetostrictive ultrasonic transducer (GMUT), the key factors affecting the mechanical vibration performance of the ultrasonic system are obtained by analyzing the vibration transmission characteristics of the joint surfaces. The influence of different joint surface contact characteristics (JSCT) on the amplitude–frequency curve of the transducer is analyzed by the ANSYS software. Simulations and experiments have been conducted to verify the predicted results. As the preload force increases, the natural frequency of the transducer increases, but the growth rate decreases. The natural frequency of the double-rod GMUT with a small joint surface area is slightly higher in the optimal output mode shape, while its amplitude is significantly larger. The optimal prestress for the GMUT with different-sized joint surfaces is 3–5 MPa. This paper acquires the JSCT under a high-frequency vibration condition, reveals the influence of the joint surface on the mechanical output performance of the GMUT, and can provide a theoretical basis for the design and analysis of the rotary ultrasonic vibration processing system. [ABSTRACT FROM AUTHOR]

Magnetostrictive transducer, as a kind of high-efficiency transducer, has a broad application in the field of energy harvesting and sensor. However, the voltage generating performance of the transducer limits its application. This paper will endeavor to quantify the load-induced voltage of magnetostrictive transducer by developing a holistic theoretical model and deriving the corresponding analytical solution. On this basis, this paper proposed the concept of voltage sensitivity in transducer optimization, which could quantitatively analyze the normalized voltage generated by a unit excitation. Based on the theoretical simulation and experimental validation, the voltage sensitivities of magnetostrictive transducer under different mechanical loads are investigated. The parametric analysis will be conducted to further optimize the transducer structure to enhance its open-circuit and load voltage. The works of this paper could be instructive to guide magnetostrictive transducer design in sensing and energy harvesting applications. [ABSTRACT FROM AUTHOR]

For realizing ultrasonic elliptical vibration-assisted cutting, a single excitation elliptical vibration system was proposed in this work, which was composed of a giant magnetostrictive transducer and an asymmetrical stepped ultrasonic horn with arc transition (ASUH). The dynamic simulation of the vibration system was carried out using ANSYS, the output end of the vibration system produced longitudinal and transverse vibrations simultaneously due to the ASUH at the resonant frequency, and the influence of the transition arc of the ASUH on the elliptical vibration performance of the vibration system was studied. The impedance, elliptical vibration trajectory of the output end, and output amplitude of the vibration system were tested experimentally. The results show that the actual resonant frequency of the vibration system was 20.708 kHz, the mechanical quality factor was 106, and the longitudinal amplitude was slightly greater than the transverse amplitude of the output end. The theoretical calculations coincide with the experimentally tested results. [ABSTRACT FROM AUTHOR]

This paper proposes a multilevel three-dimensional constitutive model based on a microscopically phenomenological approach from the domain rotation mechanism, which is a fully coupled self-consistent homogenization scheme considering the interactions between elastic–inelastic strain and hysteresis. Considering the interactions among magnetic domains, grains, polycrystalline complexes, and macroscopic phenomenology, we predict the nonlinear magnetostrictive response of Terfenol-D under different types of external force loads and magnetic excitations in various thermal environments involving multi-fields of coupled magnetic, elastic, thermal, and mechanical phenomena. The average values of the mechanical bulk strains for different magnetization states are obtained at the grain scale utilizing Boltzmann functions and a self-consistent homogenization scheme. A Taylor series expansion of the Gibbs function concerning the field variables and an adapted Jiles–Atherton model are used to construct the hysteresis coupled constitutive relations at the macroscopic scale. The results associated with the experiments show that the established model can reasonably predict the magnetostrictive response under different external mixed stimuli. It can provide theoretical guidance for the precise control of nonlinear vibrations and the optimal design of the rotating giant magnetostrictive transducers at both microscopic and macroscopic multiple scales. [ABSTRACT FROM AUTHOR]

Economic and social development of nations across the globe is demanding enormous need for energy and power resources. Energy production using safe and renewable sources can aid in mitigating the release of greenhouse gases and avoiding the devastating climate changes. In the present case, a linear type magnetostrictive transducer device is designed by employing Terfenol-D magnetostrictive rods for renewable energy harvesting application. A linear device was designed with two Terfenol-D rods, three permanent magnets (neodymium magnets), springs, and primary and secondary coils. Terfenol-D rod crystallizes in cubic Laves phase and exhibits the saturation magnetostriction value of 1242 × 10−6 at the field of 2.5 kOe. An equivalent circuit is constructed for the induced magnetic flux in the designed transducer device. Frequency and wave form dependent output voltage is examined in the designed energy harvesting device. A square wave at the applied frequency of 2200 Hz (100 mA current) produces a maximum output voltage of 4.91 V. Sine and triangle waves produce 3.38 and 2.82 V, respectively, at 1700 and 1600 Hz. The induced voltage is sufficient to ignite the light emitting diode. A linear type magnetostrictive transducer can be employed as a potential renewable energy source for real-time application with moderate output voltage. [ABSTRACT FROM AUTHOR]

Giant magnetostrictive transducer can be widely used in active vibration control, micro-positioning mechanism, energy harvesting system, and ultrasonic machining. Hysteresis and coupling effects are present in transducer behavior. The accurate prediction of output characteristics is critical for a transducer. A dynamic characteristic model of a transducer is proposed, by providing a modeling methodology capable of characterizing the nonlinearities. To attain this objective, the output displacement, acceleration, and force are discussed, the effects of operating conditions on the performance of Terfenol-D are studied, and a magneto-mechanical model for the behavior of transducer is proposed. A prototype of the transducer is fabricated and tested to verify the proposed model. The output displacement, acceleration, and force have been theoretically and experimentally studied at different working conditions. The results show that, the displacement amplitude, acceleration amplitude, and force amplitude are about 49 μm, 1943 m/s2, and 20 N. The error between the model and experimental results are 3 μm, 57 m/s2, and 0.2 N. Calculation results and experimental results show a good agreement. [ABSTRACT FROM AUTHOR]

In recent years, ultrasonic machining has been developing rapidly, and it is used in areas such as abrasive machining, cleaning, and welding. In this research, a magnetostrictive device with pure nickel conical core with cone angle of 30° was constructed. The observed sound pressure level was used as a measure of transducer performance. Also, the ability of the device to reduce the residual pesticide on cucumber surface due to cavitation was evaluated. The results showed that the sound pressure from simulation by JMAG-Designer software is almost the same as the sound pressure produced in the constructed transducer. To assess the performance of the device in removing residual pesticide from cucumber surface and evaluate the changes in peel texture of cucumber, the gas chromatography (GC) and scanning electron microscope (SEM) methods were used, respectively. The GC results showed that with 20 min treatment, the removal of pesticide based on height and chromatogram area was 75% and 83%, respectively. The SEM results showed that by increasing the treatment time, the stomatal pore area reduced from 144.74 μ m 2 (reference) to 30.56 μ m 2 (20 min treatment). These results are promising; hence, further research is suggested towards enhancing the device for commercial use in biomaterials processing operations such as cleaning and removing pesticides from fruits and vegetables. [ABSTRACT FROM AUTHOR]

A numerical study of the delay in the excitation of oscillations of a magnetostrictive transducer in the frequency multiplication mode based on the model of coupled oscillators is presented. The non-stationary nature of the oscillations excited after the amplitude jump is revealed. The phenomenon is interpreted on the basis of the dynamic potential model. A numerical study of the development of oscillations in time has been carried out, and phase portraits of oscillations have been constructed. The fractal-like nature of non-stationary oscillations is established, which manifests itself in the preservation of the degree of their chaoticity with a change in the value of the calculation step in time. [ABSTRACT FROM AUTHOR]

The applications of sensors in the aerospace industry are mostly concentrated in the middle and high frequencies, and low-frequency sensors often face the problems of low power and short working bandwidth. A lightweight, thin, high-power, low-frequency broadband transducer based on giant magnetostrictive material is designed. The design and optimization processes of the core components are introduced and analyzed emphatically. The finite element simulation results are validated by the PSV-100 laser vibration meter. Three basic configurations of the work panel are proposed, and the optimal configuration is determined by modal, acoustic, and vibration coupling analyses. Compared with the original configuration, it is found that the lowest resonant frequency of the optimal configuration is reduced by 24.6% and the highest resonant frequency within 2000 Hz is 1744.9 Hz, which is 54.2% higher than that of the original configuration. This greatly improves the vibration power and operating frequency range of the transducer. Then, the honeycomb structure is innovatively applied to the work panel, and it is verified that the honeycomb structure has a great effect on the vibration performance of the work panel. By optimizing the size of the honeycomb structure, it is determined that the honeycomb structure can improve the vibration power of the work panel to its maximum value when the distance between the half-opposite sides of the hexagon is H = 3.5 mm. It can reduce the resonant frequency of the work panel; the lowest resonant frequency is reduced by 12.8%. At the same time, the application of a honeycomb panel structure can reduce the weight of the transducer. [ABSTRACT FROM AUTHOR]

The giant magnetostrictive transducer (GMT) can be widely used in ultra-precision machining in precision-fluid-control fields. The temperature stability of GMT is critical for the reliable generation of output characteristics. This study presents a magnetic-energy-losses method for the GMT working at high frequency, and designs a temperature-stable control system to improve energy transmission and heat dissipation. Based on the loss-separation theory and experimental data, the temperature-rise characteristics of the transducer are analyzed. The temperature rise considers the effects of hysteresis loss, the eddy-current loss, the anomalous loss and the Joule heat. A constitutive relation among losses, frequency and magnetic-flux density is given. The temperature distribution of the transducer can be quickly and accurately calculated, using the constitutive equation. According to the convective heat-transfer and the thermal-compensation method, a temperature-control system is designed. A prototype of the system is then fabricated and tested to verify the feasibility and efficacy of the proposed design methods. The results demonstrate that the output- displacement deviation can be controlled at less than 0.65 μm, and the temperature difference is less than 3 °C. [ABSTRACT FROM AUTHOR]

The vibration characteristics of a giant magnetostrictive transducer play a significant role in the stability and processing effect of spinning ultrasonic machining. The output characterization of the giant magnetostrictive transducer is unstable subject to an powerful external load, which severely restricts the application of giant magnetostrictive transducer in industry. In this study, the effect of change of load force and electrical parameter in the different directions on the high-frequency (about 20 kHz) vibration output characteristics of the giant magnetostrictive transducer is investigated, through finite element analysis and static loading experimental. The result shows that the electrical parameter of a giant magnetostrictive transducer has a similar changing trend with the increasing of the axis and radial force load; The resonant frequency also increases with the increase of electrical parameter and load force; The amplitude attenuation of ultrasonic vibration will become extraordinary intense even almost to stop beat when the axis force load increase to 750 N and radial force load increase to 550 N; The gradient of resonant frequency in a radial direction is more significant than that in an axial direction. Based on the results of theoretical analysis and static loading experimental, the measures to reduce amplitude attenuation and improve output stability of amplitude under resonant frequency are proposed. The results can provide theoretical guidance for a magnetostrictive transducer used in the actual spinning ultrasonic vibration processings. [ABSTRACT FROM AUTHOR]

Due to high piezomagnetic coefficient of the synthetic giant magnetostrictive materials, they are able to provide good enough force and displacements for industrial applications. Some natural materials such as nickel also exhibit magnetostrictive properties, but with poor performance, which might be improved by some electromagnetic manipulations. In this study, the effect of different coil parameters such as current, frequency, the number of coil turn, and the core lamination factor in different directions ([X or Y] and Z axes), on the performance of a nickel‐core magnetostrictive transducer is investigated. Since the fluctuation of magnetostrictive force in the longitudinal direction of core (along the Z‐axis) is an important parameter for generating the ultrasonic waves, the results showed that this force fluctuation decreases with increasing frequency. By increasing the lamination factor in the X direction, the fluctuation of magnetostrictive force along the Z‐axis remains constant. However, the ultrasonic performance of the magnetostrictive transducer may be optimized by proper selection of lamination factor along the X‐axis. The relationships between the results were investigated in more detail and presented as linear equations. Based on these equations, it was concluded that current and turn number of coil has the greatest positive impact on the magnetostrictive performance of the transducer, while increasing the frequency and lamination factor have a weakening effect. [ABSTRACT FROM AUTHOR]

This article presents a design method of Longitudinal-Bending Coupled Horn (L-BCH) of a giant magnetostrictive transducer utilized in spinning ultrasonic machining. The structural parameters are initially determined by the design theory of the horn and thick disc. Then, the effect of the structural parameters of the rotating wheel on the vibration characteristics of the L-BCH are explored by the model and harmonic response analysis through the finite element method. Through continuous modification of the geometrical parameters of the rotary wheel, the L-BCH meeting the requirements of a giant magnetostrictive transducer is designed. Finally, the frequency and amplitude measurements are performed on the prototype by the impedance analyzer and the laser vibrometer. The finite element analysis and experimental results show that: the large diameter, small diameter, thickness, and fillet radius of the rotating wheel have different impacts on the dynamic characteristics of the L-BCH. Among them, the thickness of the rotary wheel has the most significant influence on the natural frequency and amplitude. In addition, the rotating wheel has a pitch circle when the longitudinal-bending coupled vibration occurs, and the structure itself also has the characteristic of amplifying amplitude. [ABSTRACT FROM AUTHOR]

A comprehensive model is a basis for adequately understanding the energy conversion mechanism of magnetostrictive materials and guides the design of magnetostrictive devices. This paper established a fully coupled model that fully considered the piezomagnetic effect and the electromagnetic effect in its procedure of energy conversion. The proposed model can accurately predict the output voltage with different excitation levels and illustrate the interaction between physical fields. Based on the established model, we quantify the voltage contributed by the piezomagnetic effect and the electromagnetic effect. After a thorough analysis, we discovered that even though the voltage generation is always dominated by the piezomagnetic effect of the magnetostrictive material, the proportion from the electromagnetic effect will increase moderately with larger excitation levels. In addition, the magnetostrictive effect toward the output performance is also discussed, which proved to lead to a marginal impact on the voltage waveform. [ABSTRACT FROM AUTHOR]

Air-coupled ultrasonic excitation is a relatively poorly studied method of nondestructive testing of polymer and composite materials. The combination of noncontact ultrasonic stimulation in conjunction with laser vibrometry can provide an assessment of the quality of the product without external influence on the tested material. This work is devoted to the study of an ultrasound diagnostic system based on the combined use of a noncontact magnetostrictive transducer and scanning laser Doppler vibrometry for nondestructive testing of polymer and composite materials. We believe that such combination can provide sufficient power for rapid detection of defects, while the optimization of the experimental conditions increased the efficiency of testing results. Measurement of the directional diagram of the magnetostrictive transducer has made it possible to determine the features of the radiation of the magnetostrictor in an assembly with a titanium step-type waveguide. [ABSTRACT FROM AUTHOR]

In this study, a giant magnetostrictive ultrasonic transducer was designed with Terfenol-D as the active material. The influence of different Terfenol-D rod structures on the performance of the giantmagnetostrictive transducerwas investigated. Finite element analysis was used to analyze the dynamics of the theoretical giant magnetostrictive transducer and to validate the design. Eddy current losses were simulated for Terfenol-D rods of various structures using finite element analysis in ANSYS Maxwell. Two different Terfenol-D rods were then fabricated with either slices along the axial direction or slit along the radial direction, then the impedance and amplitude of the magnetostrictive ultrasonic transducer composed of the two Terfenol-D rods were measured. The results suggest that sliced Terfenol-D rods can suppress eddy currents more effectively, resulting in higher energy conversion efficiency; therefore, the Terfenol-D rods of small giant magnetostrictive transducers should be sliced along the axial direction to suppress eddy currents, whereas radial slits should be adopted for the rods of large giant magnetostrictive transducers to ensure integrity of the Terfenol-D rod and avoid adverse effects on the vibration performance of the giant magnetostrictive transducer that are caused by cutting the rods. [ABSTRACT FROM AUTHOR]

In this paper, a vibrational drilling tool using a magnetostrictive torsional transducer is designed and fabricated. The torsional transducer is a hollow cylinder, which is made up of "2 V permendur." Passing an alternating current through the material creates a variable circular magnetic field and exciting a coaxial coil with a direct current generates a constant axial field in the material. According to the Wiedemann effect, the magnetic domains of the material rotate helically in the direction of the external field and cause a shear strain in the material. To utilize the maximum torque and amplitude of the transducer as well as to maintain the transducer's resonance conditions, a wave transmitter is designed to connect the transducer to a drill bit. The dimensions of the vibrating tool are calculated theoretically and verified by the finite element software of COMSOL. Friction couplings are designed to connect the transducer, wave transmitter, and the drill bit. This torsional drilling tool is used for drilling of aluminum workpieces. The tests show that torsional vibrations reduce the required drilling torque by 60% in comparison to conventional drilling. In addition, usage of the torsional vibrations has the effect of the chip breaking, improving the accuracy of the hole size by 55.4%, and reducing the drilling surface roughness by the percent of 25.3% in comparison to conventional drilling. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical and experimental study on high-frequency (>5000 Hz) output characteristics of the giant magnetostrictive transducer (GMT) at varied operating conditions. Based on the Jiles–Atherton model, Maxwell’s equations, Newton’s law, and Fourier’s heat transfer equation, a nonlinear electromagnetic–mechanical–thermal multi-field coupled finite element model for GMT is established. The output displacement amplitude of the magnetostrictive rod and the acceleration of vibrating horn at the GMT device are measured and analyzed at varied exciting amplitude of ac magnetic field and frequencies (from 5600 to 7000 Hz). The frequency dependences of permeability and magnetoelastic coupling coefficient obtained from the experimental results are used in revising the model parameters. These output characteristics analysis results can provide theoretical and experimental guidance in the optimization of structural design and precise controlling for high-frequency GMT system. [ABSTRACT FROM AUTHOR]

Experimental and calculating analysis of magnetic losses for Terfenol-D is a necessary step for the design of high-power magnetostrictive transducer. In order to further research the magnetic energy losses characteristics, a Terfenol-D rod is sectioned along different directions, and these slices are made into several square annular sheet samples. The influences of material magnetization direction on the losses are compared and analyzed. The values of magnetic energy losses are measured to investigate their variations at different frequencies and magnetic densities of driving magnetic field. Furthermore, the traditional losses formula is improved. The values of the hysteresis losses, eddy-current losses, and anomalous losses are separated out, and the losses coefficients are achieved through polynomial curve fitting. This paper can provide theoretical and experimental guidance for the high-frequency applications of magnetostrictive materials. [ABSTRACT FROM AUTHOR]

• A giant magnetostrictive transducer was simulated and calculated using magneto-mechanical coupling in COMSOL Multiphysics, the influence of the thickness of the magnetic cylinder and the magnetic block on the performance of the transducer was investigated. • The temperature rise of the two transducers during the operation was simulated and experimentally tested. • The finite element calculations of the output amplitude and temperature rise of the transducer agreed with the experimental test values. It can be used as a simulation method to optimize the design of the magnetic circuit structure of the giant magnetostrictive transducer and improve its vibration performance. A giant magnetostrictive transducer was studied. The dynamic simulation analysis of the transducer was carried out, the influence of the magnetic block and the magnetic cylinder on the vibration performance of the transducer was studied, and the temperature rise of the transducer during the operation was simulated and calculated. The impedance and output amplitude of the developed transducer were tested experimentally. The results show that the axial magnetic field intensity of the Terfenol-D rod increased and then decreased, and the output amplitude increased and then decreased slightly with the increase of the thickness of the magnetic cylinder. As the thickness of the magnetic block increased, the axial magnetic field intensity of the rod increased, and the output amplitude of the transducer also increased. Compared with the transducer without magnetic cylinder, the transducer with magnetic cylinder has larger electromechanical conversion coefficient, and output amplitude, but the temperature was higher after working for the same time. [ABSTRACT FROM AUTHOR]

This paper analyzes a prototype microgyrosensor that employs the magnetostrictive alloy Galfenol for transduction of Coriolis-induced forces into an electrical output for quantifying a given angular velocity. The magnetic induction distribution in the Galfenol sensor patch depends on its bending shape and magnetoelastic properties and is investigated using a finite element model. Fluctuations in magnetic induction caused by a sinusoidal rotation of the sensor produce an amplitude modulated voltage in a surrounding coil which is simulated and measured. [ABSTRACT FROM AUTHOR]

magnetic field sensor of air-gap Fabry–Perot fiber interferometersis proposed based on magnetostrictive effect. The sensor is consisted of single-model fiber (SMF), air-gap, no-core fiber (NCF) and magnetic fluid. Those are sealed in the capillary, SMF and NCF are connect with air chamber and magnetic fluid column. With the presence of an external magnetic field, air chamber cavity length changes because of the magneto-volume variation of magnetic fluids. This situation causes a change in the optical path difference. Detection of the drift of interference spectrum leads to the detection of the change in magnetic field. When the magnetic field is parallel to the direction in which the capillary is placed, the sensitivity is 0.2347 nm/mT; when the magnetic fluid is perpendicular to the direction in which the capillary is placed, the sensitivity is 0.325 nm/ mT. In addition to this new magnetic fluid sensor, a practical detection system is built, which relative error rate is less than 2%. [ABSTRACT FROM AUTHOR]

Many piping networks in processing plants, such as refineries, chemical plants, and electric power generation plants, are operated at elevated temperatures (=250 °F or 121 °C). Failure of these insulated high temperature pipes can cause a major disruption of plant operation. In addition to inspection during the regular plant shutdowns, processing industries are looking for ways to inspect and monitor these pipelines on-line to ensure safe operation of the plants. Permanent monitoring of high temperature structures would require addressing the following technical problems: supporting the sensor functionality at high temperatures, ensuring the probe durability, and maintaining good coupling of the probe to the structure. In this work, a probe utilizing magnetostrictive transduction was tested on a mockup at 200 °C and produced a steady high amplitude signal over a period of 270 days. Probe performance parameters such as signal to noise ratio, data reproducibility, and sensitivity to anomalies are discussed. [ABSTRACT FROM AUTHOR]

In this work, a switching control energy harvesting method using magnetostrictive materials is proposed. By combining a magnetostrictive material, an electric circuit, and an electronic switch, large-scale kinetic to electrical energy conversion can be achieved. The magnetostrictive material, magnet bias, and coils constitute an energy transducer, called a magnetostrictive transducer. The electronic switch strategically controls the switching of the circuit state according to an input switching signal. Using numerical simulations, we optimised the parameters and validated the harvesting performance with experimental measurements using a 3.75 m vibrated cantilever truss structure. In 20.0 s, the proposed method achieved an electrical energy of approximately 45 μJ, which is seven times more than that of the conventional passive method. [Display omitted] • Switching control energy harvesting method proposed using magnetostrictive material. • Large-scale kinetic to electrical energy conversion can be achieved. • Numerically predicted the performance and validated it experimentally. • Proposed strategies applied to a truss structure to simulate flexible infrastructure. [ABSTRACT FROM AUTHOR]

To date, the successful application of large scale ultrasound in water treatment has been a challenge. Magnetostrictive ultrasound technologies for constructing a large-scale water treatment system are proposed in this study. Comprehensive energy evaluation of the proposed system was conducted. The effects of chosen waveform, scalability and reactor design on the performance of the system were explored using chemical dosimetry. Of the fundamental waveforms tested; sine, triangle and square, the highest chemical yield resulted from the square wave source. Scaling up from the 0.5 L bench-scale system to the 15 L large-scale unit resulted in a gain of approximately 50% in sonochemical efficiency (SE) for the system. The use of a reactor tank with 45° inclined sides further increased SE of the system by 70%. The ability of the large scale system in removing contaminants from natural water samples was also investigated. The results revealed that the large-scale unit was capable of achieving a maximum removal of microbes and dissolved organic carbon (DOC) of 35% and 5.7% respectively at a power density approximately 3.9 W/L. The results of this study suggest that magnetostrictive ultrasound technology excited with square wave has the potential to be competitive in the water treatment industry. [ABSTRACT FROM AUTHOR]

CoFe2O4 (core)/BiFeO3 (shell) nanoparticles are prepared by varying the relative molar concentration of core and shell materials (40%CoFe2O4-60%BiFeO3, 50%CoFe2O4-50%BiFeO3, and 60%CoFe2O4-40%BiFeO3). The core-shell nature is confirmed from transmission electron microscopy on these samples. A plot of ΔM (=MFC-MZFC) vs temperature suggests the presence of two types of spin dynamics: (a) particle size dependent spin blocking and (b) spin-disorder. These two spin dynamic processes are found to contribute independently to the generation of magnetoelectric voltage. Very clear first order and second order magnetoelectric voltages are recorded. The resemblance of the first order magnetoelectric coefficient vs temperature plot to that of building up of order parameters in the mean field theory suggests that spin disorder can act like one of the essential ingredients in building the magnetoelectric coupling. The best result is obtained for the 50-50 composition sample, which may be due to better coupling of magnetostrictive CoFe2O4, and piezoelectric BiFeO3, because of the optimum thickness of shell and core. [ABSTRACT FROM AUTHOR]

As a rapid, noncontact, and nondestructive technology, magnetostrictive guided waves have been widely used for the quality inspection of pipes and stay cables. Traditionally, a single-frequency signal with a high amplitude and a long pulse duration is used to increase the excitation energy and detection distance. However, the longer the pulse duration of a single-frequency signal is, the lower the resolution of adjacent defects and the accuracy of defect location will be. A novel method of addressing this problem is proposed in this paper. An encoded multifrequency excitation signal, whose frequency range is selected from a calculated dispersion curve, is used to excite the guided wave. After passing through the signal-conditioning board, the detected defect signals are sampled, averaged, and then filtered using a matched filter. In this manner, the pulse width of echoes can be greatly compressed. Our experimental results demonstrate that our proposed method can improve the resolution of adjacent defects and the accuracy of defect location in the propagation direction of the magnetostrictive guided wave. [ABSTRACT FROM AUTHOR]

Combinatorial search is one of the useful methods that could search for optimal composition of alloymaterials or novel alloy materials. Combinatorial sputtering provides sample group (library) having different compositions in a limited place. Then, the properties of the samples can be scanned in an efficient way. In this research, magnetostrictive material with high magnetostriction, relative permeability, and resistivity was studied. Desired value of magnetostriction is more than 20 × 10-6, relative permeability is more than 4000, and resistivity is more than 100 μΩ·cm. As a result, composition that Cr content is less than 14 at.% fill the desired value of relative permeability, and more than 10 at.% fill the desired value of resistivity. There is possibility to fill the desired value of magnetostriction. [ABSTRACT FROM AUTHOR]

• A description of the energy of propagating magnetostrictive guided waves is derived. • An energy-based model for magnetostrictive guided wave propagation in bridge cables is proposed. • The energy-based model shows good performance in predicting energy attenuation. • The frequency of the guided waves and cable force significantly affect the model parameters. • Energy losses and energy exchange between the wires are negligible in the strands. Guided wave inspection has broad application potential in detecting defects in bridge cables. The attenuation characteristics of guided waves must be understood to quantify damage. However, owing to the mutual coupling between adjacent wires in cables, the attenuation characteristics of guided wave propagation in bridge cables are highly complex. In this work, the attenuation characteristics of low frequency longitudinal guided waves generated by magnetostrictive transducers in bridge cables were studied theoretically and experimentally. The results revealed that the energy-based model proposed herein—which considers the material damping, the energy transferred between adjacent wires and the heat energy generated by the energy transferred—performs well in predicting the energy attenuation. The frequency of the guided waves and the cable force significantly affect the model parameters. As the heat energy conversion coefficient decreases with increasing cable force, the energy of guided waves propagating at close range concordantly increases. The energy-based model for guided wave propagation in strands can be simplified as an exponential function, because energy losses and energy exchange between wires are negligible. In addition, high frequency guided waves decay faster in cables and strands. The decay rate increases more quickly with increasing frequency in the cables, as the cables have more wire contact that make high frequency guided waves decay faster. Although guided waves for 5–30 kHz decay faster in strands, the attenuation rate for guided wave propagation in cables will exceed the strands if the frequency keeps increasing. [ABSTRACT FROM AUTHOR]

The analysis of a passive damper employing smart materials is carried out through the description of a concept device loaded by a vibrating mass. Such a device is able to damp vibration and to produce electric energy (energy harvesting). Its basic properties are described in detail and the relationships between damping features and its physical parameters are shown. The analysis is carried out by a linear modeling at first, while the comparison to its actual behaviour is exploited to justify a more careful study where the material non-linearity is considered. Analytical results on the linear model and the spice numerical analysis of a non-linear model are presented. [ABSTRACT FROM AUTHOR]

In this paper, a fiber optic based sensor capable of fault detection in both radial and network overhead transmission power line systems is investigated. Bragg wavelength shift is used to measure the fault current and detect fault in power systems. Magnetic fields generated by currents in the overhead transmission lines cause a strain in magnetostrictive material which is then detected by Fiber Bragg Grating (FBG). The Fiber Bragg interrogator senses the reflected FBG signals, and the Bragg wavelength shift is calculated and the signals are processed. A broadband light source in the control room scans the shift in the reflected signal. Any surge in the magnetic field relates to an increased fault current at a certain location. Also, fault location can be precisely defined with an artificial neural network (ANN) algorithm. This algorithm can be easily coordinated with other protective devices. It is shown that the faults in the overhead transmission line cause a detectable wavelength shift on the reflected signal of FBG and can be used to detect and classify different kind of faults. The proposed method has been extensively tested by simulation and results confirm that the proposed scheme is able to detect different kinds of fault in both radial and network system. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel rotating actuator based on the interaction of a permanent magnet with a magnetostrictive soft ribbon submitted to mechanical stress. The direction and magnitude of the stress generates a directional magnetic anisotropy (easy axis) in the soft ribbon. A nonzero angle between the polarizing magnet and the induced easy axis results in a torque between the two: hence the magnet being free to rotate aligns itself with the easy axis. A demonstrator of this principle was made using a Nd–Fe–B magnet above a disk cut from an iron-based amorphous ribbon glued between two unidirectional piezoelectric actuators. The analytical model takes into account the magnetic domains and assumes a magnetization mechanism of both coherent rotation and domain-wall displacement, with a uniaxial anisotropy induced by the applied stress. [ABSTRACT FROM AUTHOR]

Magnetostrictive transducers are employed for several purposes where, often, the applied mechanical stress strongly affects the device hysteretic behavior. This issue complicates the design of controllers where such variable has to be considered as an additional input. Nevertheless, a compensation scheme with two input variables can be defined and fruitfully utilized in a suitable invertibility region. Aim of this paper is to present a novel compensation algorithm able to take into account the applied mechanical stress. Numerical results compared with experimental data, over a magnetostrictive actuator, show that the proposed approach leads to lower compensation errors with respect to stress-independent, classical, compensators. [ABSTRACT FROM AUTHOR]

Ultrasonic guided waves provide unique capabilities for the structural health monitoring of plate-like structures. They can detect and locate various types of material degradation through the interaction of shear-horizontal (SH) waves and Lamb waves with the material. Magnetostrictive transducers (MSTs) can be used to generate and receive both SH and Lamb waves and yet their characteristics have not been thoroughly studied, certainly not on par with piezoelectric transducers. A series of multiphysics simulations of the MST/plate system is conducted to investigate the characteristics of MSTs that affect guided wave generation and reception. The results are presented in the vein of showing the flexibility that MSTs provide for guided waves in a diverse range of applications. In addition to studying characteristics of the MST components (i.e., the magnetostrictive layer, meander electric coil, and biased magnetic field), single-sided and double-sided MSTs are compared for preferential wave mode generation. The wave mode control principle is based on the activation line for phase velocity dispersion curves, whose slope is the wavelength, which is dictated by the meander coil spacing. A double-sided MST with in-phase signals preferentially excites symmetric SH and Lamb modes, while a double-sided MST with out-of-phase signals preferentially excites antisymmetric SH and Lamb modes. All attempted single-mode actuations with double-sided MSTs were successful, with the SH3 mode actuated at 922 kHz in a 6-mm-thick plate being the highest frequency. Additionally, the results show that increasing the number of turns in the meander coil enhances the sensitivity of the MST as a receiver and substantially reduces the frequency bandwidth. [ABSTRACT FROM AUTHOR]

Giant magnetostrictive transducer with micro and nano precision has a wide application prospect in the field of remote sensing. However, excessive heat loss of components could generate during the energy conversion and transfer from electric energy to magnetic energy, and magnetic energy to mechanical energy, thereby affecting its long-term service and also reducing energy utilization. In this paper, a new magnetostrictive transducer is proposed and its excitation coil, internal and external magnetic circuit are optimized from the perspective of reducing heat loss. With the help of theoretical and finite element analysis, the response law between key parameters and heat loss of key components are summarized, which provides a basis for reducing heat loss. Finally, according to the optimization scheme, the prototype is processed, and the temperature rise and dynamic output performance of the transducer are tested by constructing an experimental setup. The results show that the transducer has a low temperature rise and good frequency response characteristics, which can provide support for long-time precise actuation on-orbit. [ABSTRACT FROM AUTHOR]

This paper deals with the development of a modeling approach for describing the magnetomechanical behavior of magnetostrictive actuators. The model couples the finite element solution, accounting for eddy currents in the magnetic materials, with a modified Preisach-type model, identified starting from the static characterization of the magnetoelastic material. The model is applied to the dynamic analysis of a Terfenol-D actuator under ac and biased supply conditions, comparing the results with experiments, and focusing the investigation on the dynamic characteristics of the device. [ABSTRACT FROM AUTHOR]

This paper addresses the development of robust control designs for high-performance smart material transducers operating in nonlinear and hysteretic regimes. While developed in the context of a magnetostrictive transducer used for high-speed, high-accuracy milling, the resulting model-based control techniques can be directly extended to systems utilizing piezoceramic or shape memory alloy compounds due to the unified nature of models used to quantify hysteresis and nonlinearities inherent to all of these materials. When developing models and corresponding inverse filters or compensators, significant emphasis is placed on the utilization of the material's physics to provide the accuracy and efficiency required for real-time implementation of resulting model-based control designs. In the material models, this is achieved by combining energy analysis with stochastic homogenization techniques, whereas the efficiency of forward algorithms is combined with monotonicity properties of the material behavior to provide highly efficient inverse algorithms. These inverse filters are then incorporated in ℋ2 and ℋ∞ theory to provide robust control algorithms capable of providing high-accuracy tracking even though the actuators are operating in nonlinear and hysteretic regimes. Through numerical examples, it is illustrated that the robust designs incorporating inverse compensators can achieve the required tracking tolerance of 1-2 μm for the motivating milling application, whereas robust designs which treat the uncompensated hysteresis and nonlinearities as unmodeled disturbances cannot achieve design specifications. [ABSTRACT FROM AUTHOR]

This paper focuses on the development of a homogenized energy model which quantifies certain facets of the direct magnetomechanical effect. In the first step of the development, Gibbs energy analysis at the lattice level is combined with Boltzmann principles to quantify the local average magnetization as a function of input fields and stresses. A macroscopic magnetization model, which incorporates the effects of polycrystallinity, material nonhomogeneities, stress-dependent interaction fields, and stress-dependent coercive behavior, is constructed through stochastic homogenization techniques based on the tenet that local coercive and interaction fields are manifestations of underlying distributions rather than constants. The resulting framework incorporates previous ferromagnetic hysteresis theory as a special case in the absence of applied stresses. Attributes of the framework are illustrated through comparison with previously published steel and iron data. [ABSTRACT FROM AUTHOR]

• The first study to establish a mathematical model for optimum compensation of a GMUT. • The first study showing resonance characteristics for frequency tracking of a GMUT. • The optimum compensation capacitance can maximize the use of ultrasonic energy. • The feedback current signal can be used for the frequency tracking method of a GMUT. Giant magnetostrictive materials (GMMs) have been widely used to fabricate transducers with high-energy output because of their excellent properties. However, there are few reports on mathematical models to optimize the impedance compensation and resonance characteristics of giant magnetostrictive transducers. In this study, a giant magnetostrictive ultrasonic transducer (GMUT) suitable for rotary ultrasonic machining systems is proposed. A mathematical model for optimum impedance compensation that considers the loss in energy conversion is established to maximize the use of ultrasonic energy. The frequency characteristics of the electrical feedback signal in the resonance state are investigated, and the resonance zone found is used for frequency tracking. An impedance analyzer is used to determine the parameters of the mathematical model, and the validity of the optimum compensation capacitance is verified by experiments. The frequency characteristics of the minimum current, active power, and amplitude are obtained to obtain the resonance zone in the GMUT with the lowest energy consumption. The results of this study provide a reference for frequency tracking. [ABSTRACT FROM AUTHOR]

• Magnetostrictive transducer simulated to generate L(0,2) mode in SG tubes of PFBR. • The transducer has been fabricated and tested experimentally. • Very good agreement observed between FE and experimental results. • Long-range propagation of 51 m has been achieved experimentally. • The magnetostrictive transducer could detect a pinhole of 1.5 mm diameter. An in-bore magnetostrictive transducer is designed for the steam generator tubes of Prototype fast breeder reactor for the generation of L(0,2) modes of frequencies in the range of 250–350 kHz. Towards this, axi-symmetric finite element models are developed to optimize the coil parameters. The optimized length of the transmitter and the receiver coils turns out to be 10 mm (~half the wavelength) for the frequency of 300 kHz. The optimized width of the coils turns out to be 0.46 mm. FE models also show the generation, propagation and reception of L(0,2) modes in the frequency range of 250–350 kHz. The role of skin effect in the magnetostrictive based-generation of L(0,2) modes with frequency is also discussed. A transducer is designed based on the FE results. The transducer is tested for the generation of L(0,2) mode in the frequency range of 250–350 kHz in a 1 m long steam generator tube segment. A good agreement is observed between FE and experimental normalized amplitudes and the times of flight for different frequencies. L(0,2) modes are found to generate and propagate and received, as predicted by the finite element simulations. An excellent agreement is observed between the experimentally measured group velocities with those obtained from the dispersion curves in this frequency range. Experiments show the signal to noise ratio to be better than 15 dB. To ascertain the utility of the transducer in steam generator tubes for the long range testing, L(0,2) mode at 300 kHz frequency is propagated in a 1.5 m long tube. The resulted multiple end reflections amount to the propagation of 51 m distance. To check the capability of detection of defects, a short tube with a full circumferential defect of depth 0.46 mm (20%WT) and a short tube with a pin hole of 1.5 mm diameter are considered. Further, FE results for the case of the axi-symmetric circumferential defect are validated experimentally. For the case of the pinhole (non-axi-symmetric), the experimental signal to noise ratio turns out to be 6 dB, which is only 6 dB lower as compared to that obtained using a piezo based ultrasonic transducer of frequency 300 kHz coupled to the end of the tube. [ABSTRACT FROM AUTHOR]

In this study, high-power ultrasonics has been used for non-contact nondestructive testing of composites. Air-coupled magnetostrictive ultrasonic transducers provide reasonable amplitudes of horn oscillations even if this type of ultrasonic stimulation is close to the idle mode. Four types of ultrasonic horns have been designed and manufactured in order to choose an optimal horn configuration. For each horn, the dependence of vibration amplitude on ultrasonic unit power has been found to exhibit a good match between the theoretical and experimental results. The resonance frequencies and amplitudes of oscillatory velocity were experimentally evaluated by using the technique of scanning laser vibrometry and modeled by means of the Autodesk Inventor software. An air-coupled magnetostrictive transducer, in conjunction with an optimized horn, has been used in the evaluation of impact damage in a graphite epoxy composite and detection of water and excessive epoxy adhesive in an aviation honeycomb panel. It is expected that the technique of air-coupled ultrasonics may be useful for inspecting thin, fragile and hydrophilic materials. Image 1 • High-power magnetostrictive ultrasonic device was used for nondestructive testing. • Four type of ultrasonic horns were designed and tested. • Vibration characteristics of the horns were analyzed top optimize test results. • Optimized magnetostrictor was used in the inspection of composites and honeycombs. [ABSTRACT FROM AUTHOR]

Magnetostrictive transduction has been widely utilized in nondestructive evaluation (NDE) applications, specifically for the generation and reception of guided waves for the long-range inspection of components such as pipes, vessels, and small tubes. Transverse-motion guided wave modes (e.g., torsional vibrations in pipes) are the most common choice for long-range inspection applications, because the wave motion is in the plane of the structure surface, and therefore does not couple well to the surrounding material. Magnetostrictive-based sensors for these wave modes using the Wiedemann effect have been available for several years. An alternative configuration of a sensor for generating and receiving these transverse-motion guided waves swaps the biasing and time-varying magnetic field directions. This alternative design is a reversed Wiedemann effect magnetostrictive transducer. These transducers exhibit a number of unique features compared with the more conventional Wiedemann sensor, including: (1) the use of smaller rare earth permanent magnets to achieve large, uniform, and self-sustained bias field strengths; (2) the use of more efficient electric coil arrangements to induce a stronger time-varying magnetic field for a given coil impedance; (3) beneficial non-linear operating characteristics, given the efficiency improvements in both magnetic fields; and (4) the ability to generate unidirectional guided waves when the field arrangement is combined with a magnetically soft ferromagnetic strip (patch). Reversed Wiedemann effect magnetostrictive transducers will be presented that are suitable for different inspection applications, one using electromagnetic generation and reception directly in a ferromagnetic material, and another design that integrates a magnetostrictive patch to improve its efficiency and enable special operating characteristics. [ABSTRACT FROM AUTHOR]

The present paper focuses on the determination of effective magneto-mechanical properties of magnetostrictive composite materials in consideration of their microscopic morphologies. For this purpose, a homogenization procedure involving a two-scale transition is applied, where representative volume elements ( ${\cal RVE}$ s) on the microscopic level are used. In order to obtain characteristic non-linear and hysteretic magnetization and magnetostrictive strain curves, we implemented a dissipative material model into the homogenization framework. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

This paper presents a bidirectional wireless swimming microrobot that has been developed, analyzed, and experimentally tested. The robot is developed based on fin beating propulsion, using giant magnetostrictive films for head and tail fins. An innovative drive approach, using separate second order resonance frequencies of the head and tail fins to generate forward and backward thrusts, is proposed and implemented on a bidirectional swimming microrobot prototype. Dynamic model of the proposed microrobot has been derived based on theoretical analysis. Simulation and experimental results have demonstrated the feasibility of the proposed drive approach and design. The developed swimming microrobot features a low driving frequency, low power consumption, and a large range of swimming speed in both the forward and backward directions. [ABSTRACT FROM AUTHOR]