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Here, in order to calibrate the magnetostrictive liquid-level meter in situ, a set of in-situ calibration device for magnetostrictive liquid-level meter is designed. The structure and working principle of the device are described, and the experimental test and error analysis are carried out for the parts of the in-situ calibration device. Finally, according to the modern instrument and error theory, the accuracy of the calibration device is assessed, and the field calibration experiment of magnetostrictive liquid level gauge is carried out. The theoretical analysis and field experiment results show that the calibrated device can meet the in-situ calibration requirements of the magnetostrictive liquid-level meter with a range of 0–6 m and a precision of 1 mm.

The output power generated by a vibrational magnetostrictive energy harvester depends on several parameters, some of them linked to the mechanical source, as vibration amplitude and frequency, others related to design quantities, like mechanical preload, magnetic bias, coil turns and load impedance. Complex models have been developed in literature to reproduce the behavior of these devices. However, for output variables such as power and voltage, one moves in a space of many variables and it is not trivial to reconstruct an overall behavior of the device. The aim of this paper is to provide a wide picture concerning the device behavior investigating experimentally the output power and voltage as a function of the mechanical and especially magnetic bias, varying the amplitude and frequency of the driving vibration. A galfenol rod (Fe81Ga19) sample inserted in a three-legged magnetizer is utilized to vary the magnetic bias and to provide the flux closure to the sample, while a dynamic test machine provides both the mechanical bias and the driving vibration at different frequencies up to 100 Hz. The paper analysis has highlighted that the output power and voltage depend on the magnetic bias according to an exponentially modified Gaussian distribution. Keeping constant the other parameters and varying the mechanical bias, a family of modified Gaussian distributions is obtained. Moreover, fixing the electric load, the amplitude and frequency of the vibration, the couple of values “magnetic bias – mechanical preload” corresponding to the maximum output power of the device depicts a linear behavior. The results here obtained point out that it is possible to simplify the design of magnetostrictive energy harvesters and to obtain high output power even with permanent magnets providing a relatively small coercive field. The results have been confirmed by using two yokes equipped with permanent magnets on the external columns. The maximum output average power obtained with permanent magnets has been 796 mW equal to 6.5 mW/cm3 with a sinusoidal vibration amplitude of 40 MPa at 100 Hz. publishedVersion

The diode is used as the detection unit to receive the millimetre-wave signal directly. A circuit is made with an operational amplifier OP27 to amplify the signal. The magnification of the OP27 circuit is stable at 100

This paper presents the implementation of magneto-mechanical constitutive law utilizing thermodynamic approach in a 3D finite element solver using COMSOL Multiphysics software. The analytical expression for the magnetic field strength and stress is derived from the constitutive model utilizing magnetic flux density and mechanical strain as state variables. The constitutive model is successfully implemented in commercially available software COMSOL. This implementation allows 3D analysis of an energy harvester device efficiently and accurately. A prototype concept device is developed to validate the model and its implementation. The device is tested under uniaxial compressive loading by varying the preload, dynamic load and magnetic bias. The model is validated by comparing the simulated and experimental results. The comparison shows that the model can reasonably predict the optimal value of the preload and magnetic bias yielding maximum power and is able to follow the measurement trends. This model can be used as a suitable tool to analyze the behavior of the concept energy harvesters and determine the optimal design parameters. acceptedVersion

Magnetostrictive thin films primarily find use for their actuation properties. Micro-electro-mechanical systems (MEMS devices) capitalize on the induced mechanical deformations when these thin films are subjected to a magnetic field. In this study, experiments are conducted on Tb-Dy-Fe thin film samples to determine their characteristic magnetization curves. The thin films are subjected to a periodically varying magnetic field of �0.6 T and the deflections at the tip are measured. A simple analytical model based on the theories of elasticity and considering transversely isotropic material properties of both the film and the substrate layers has been proposed to predict the deflections. The study has been extended to predict the tip deflections numerically using Comsol Multiphysics. The measured tip deflections are further compared with the simulated analytical and numerical results, which are found to agree with each other. � 2015 Elsevier B.V. All rights reserved.

Conference of 15th Anglo-French Physical Acoustics Conference, AFPAC 2016 ; Conference Date: 13 January 2016 Through 15 January 2016; Conference Code:126251; International audience; An Electro-Magnetic Acoustic Transducer (EMAT) is a non-contact source used in Ultrasonic Testing (UT) which generates three types of dynamic excitations into a ferromagnetic part: Lorentz force, magnetisation force, and magnetostrictive effect. This latter excitation is a strain resulting from a magnetoelastic interaction between the external magnetic field and the mechanical part. Here, a tensor model is developed to transform this effect into an equivalent body force. It assumes weak magnetoelastic coupling and a dynamic magnetic field much smaller than the static one. This approach rigorously formulates the longitudinal Joule's magnetostriction, and makes it possible to deal with arbitrary material geometries and EMAT configurations. Transduction processes induced by an EMAT in ferromagnetic media are then modelled as equivalent body forces. But many models developed for efficiently predicting ultrasonic field radiation in solids assume source terms given as surface distributions of stress. To use these models, a mathematical method able to accurately transform these body forces into equivalent surface stresses has been developed. By combining these formalisms, the magnetostrictive strain is transformed into equivalent surface stresses, and the ultrasonic field radiated by magnetostrictive effects induced by an EMAT can be both accurately and efficiently predicted. Numerical examples are given for illustration.

We have designed a temperature and strain monitoring system for a magnetic actuator based on the giant magnetostrictive material Terfenol-D (Tb0.3 Dy0.7Fe1.92) with Fiber Bragg grating (FBG) sensors. Magneto-elastic properties of Terfenol-D depend on magnetization, stress pre-history, and temperature. In order to simultaneously monitor these effects, we have implemented a system based on a cylindrical Terfenol-D rod monitored with four FBGs that allows making the appropriate compensations on the strain measurement due to temperature drift. We have measured the magnetostriction in the axial and the transverse directions for the Terfenol-D rod with two perpendicular FBGs, and calculated the Poisson ratio. An additional mechanical system for strain amplification has been designed in order to increase sensitivity, by a factor of 4, in the strain measurement with the FBG sensor.

The magnetostriction means of generation and reception of ultrasonic guided waves is being used for the longrange inspection of pipelines for in-service damage such as corrosion. The generation of higher-strength ultrasonic guided waves in pipes using a magnetostrictive transducer, due to increased magnetostriction using a flux concentrator, is reported in this paper. A soft magnetic ribbon with negligible magnetostriction was used as a flux concentrator in the magnetostrictive sensor. The amplitude of the signal from a sensor with the flux concentrator at a power level of 10% (of the maximum instrument power level) was found to be comparable with the signal obtained from the sensor without flux concentrator at power levels of 50% of the maximum. The effect of the flux concentrator on different magnetostrictive sensors is also reported in this paper.

Ferromagnetic and ferroelectric characteristics of Gd and Nd-substituted nickel ferrite were investigated. The materials formed in the cubic inverse spinel phase with small amounts of GdFeO 3 and NdFeO 3 as the additional phases in the respective materials. Substitution of Gd and Nd for Fe caused decrease in the saturation magnetization and Curie temperature of the nickel ferrite. However, the saturation magnetostriction is seen not to change significantly by the substitution of Gd and Nd. The existence of the ferroelectricity was confirmed from the ferroelectric loops and magnetocapacitance of -2% and -3% were observed. The large frequency dependence of the (high) dielectric constant reveals a wide dispersion of relaxation times. The ferroelectric transition temperature values of NiO.Fe 1.95Gd 0.05O 3 and NiO.Fe 1.95Nd 0.05O 3 were found to be 498 and 544 K, respectively. � 2009 Elsevier B.V. All rights reserved.

This paper deals with buckling, free vibration and damping analysis of viscoelastic sandwich beam with constrained magnetostrictive layer. Eight node plane stress element is used for the analysis. The influence of viscoelastic core thickness and magnetostrictive layer thickness on the buckling and dynamic analysis of sandwich beam under magnetic environment is analyzed by considering the initial stresses due to uniform magnetic field. The validation is carried out using commercial package ANSYS 8.1, based on the thermal analogy concept given by Cote et al. [Dynamic and static modeling of piezoelectric composite structures using a thermal analogy with MSC/NASTRAN, Compos. Struct. 65 (2004) 471-484]. � 2008 Elsevier B.V. All rights reserved.

This paper describes and discusses the "STBU" speaker recognition system, which performed well in the NIST Speaker Recognition Evaluation 2006 (SRE). STBU is a consortium of four partners: Spescom DataVoice (Stellenbosch, South Africa), TNO (Soesterberg, The Netherlands), BUT (Brno, Czech Republic), and the University of Stellenbosch (Stellenbosch, South Africa). The STBU system was a combination of three main kinds of subsystems: 1) GMM, with short-time Mel frequency cepstral coefficient (MFCC) or perceptual linear prediction (PLP) features, 2) Gaussian mixture model-support vector machine (GMM-SVM), using GMM mean supervectors as input to an SVM, and 3) maximum-likelihood linear regression-support vector machine (MLLR-SVM), using MLLR speaker adaptation coefficients derived from an English large vocabulary continuous speech recognition (LVCSR) system. All subsystems made use of supervector subspace channel compensation methods-either eigenchannel adaptation or nuisance attribute projection. We document the design and performance of all subsystems, as well as their fusion and calibration via logistic regression. Finally, we also present a cross-site fusion that was done with several additional systems from other NIST SRE-2006 participants. © 2006 IEEE.

We report on the results pertinent to structural, magnetic, magnetostrictive studies of the Tb 0.3 Dy 0.7 − x Nd x Fe 1.93 [ x = 0, 0.05, 0.1, 0.15 and 0.2] compounds. From the evidenced magnetization and magnetostriction results, the crucial finding that we emphasize is that the realization of minimum anisotropy for the compound with the composition x = 0.1. From the X-ray diffraction on magnetically aligned samples, (4 4 0) peak splitting analysis and Mossbauer studies, we ascertain that the easy magnetization direction (EMD) for x = 0.2 compound it is towards 〈1 1 0〉. Above results also affirmed that indeed there exists transformation of the structural distortion from rhombohedral to orthorhombic from x = 0 to x = 0.2. The Laves phase compound Tb 0.3 Dy 0.6 Nd 0.1 Fe 1.93 with a large magnetostriction ( λ 111 ≈ 1270 × 10 −6 ) and a low anisotropy may be a potential candidate for magnetostriction applications.

The paper analyses the damping characteristics obtained using a distributed magnetostrictive layer bonded to an aluminum beam for different boundary conditions and coil configurations. The magnetostrictive layer produces the actuating force required to control the vibration in the beam, based on a negative velocity feedback control law. The control input is the current to the solenoid surrounding the beam. Prior formulations in the literature have assumed that the current through the coil is a function of axial distance. Even though this assumption is mathematically valid, a physical consideration of the problem limits such an assumption. In the present study, perhaps for the first time, a finite element formulation, physically consistent with the problem has been developed. Vibration reduction in the beam, by positioning the magnetostrictive layer and its current carrying actuating coil pair along the beam is investigated. Issues associated with control for different boundary condition are highlighted. ? 2003 Elsevier Science Ltd. All rights reserved.

Conference of 12th Anglo-French Physical Acoustics Conference, AFPAC 2013 ; Conference Date: 16 January 2013 Through 18 January 2013; Conference Code:104840; International audience; Magnetostriction arises in ferromagnetic materials subjected to magnetization, e.g., when an EMAT (Electro-Magnetic Acoustic Transducer) is used to generate ultrasonic waves. In such a case, the magnetostriction force must be taken into account as a transduction process that adds up to the Lorentz force. When the static magnetic field is high compared to the dynamic field, both forces are driven by the excitation frequency. For lower static relative values of the magnetic fields, the Lorentz force comprises both the excitation frequency and its first harmonic. In this work, a model is derived to predict the frequency content of the magnetostrictive force that comprises several harmonics. The discrete frequency spectrum strongly depends on both the static field and the relative amplitude of the dynamic field. The only material input data needed to predict it is the curve of macroscopic magnetostrictive strain that can be measured in the direction of an imposed magnetic field. Then, the various frequency-dependent distributions of Lorentz and magnetostriction body forces can be transformed into equivalent surface stresses. Examples of computation are given for different static and dynamic magnetic fields to study their influence on the frequency content of waves generated in ferromagnetic materials.

cited By 1; International audience; The magnetostriction of composites consisting of a non-magnetic matrix, randomly filled by ferromagnetic particles is measured as a function of temperature. The magnetic property of the particles and the mechanical property of the matrix are both dependent on temperature. Extracting the thermal expression of the magnetic stress and recording the composite mechanical stressstrain response allows us to predict the magnetostriction thermal behavior of the composites. © 2012 IOP Publishing Ltd.

International audience; Heterostructures of piezoelectric Pb(Zr,Ti)O 3 and magnetostrictive Galfenol were fabricated by sputtering and pulsed laser deposition on platinized Si substrates with the aim to induce a magnetoelectric coupling between the layers of the two materials. In this study, no intermediate layer was introduced between Pb(Zr 0.56 Ti 0.44 )O 3 and Galfenol in contrast to most of the previous thin films studies. The obtained magnetoelectric coupling constant is in the range of 6-7 V/(cm Oe), indicating that an undisturbed piezoelectric-magnetostrictive interface can outbalance small deteriorations of the ferroic properties of the active materials. © 2015 AIP Publishing LLC.

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.

cited By 36; International audience; The magnetostriction of composite consisting of a soft matrix, non-magnetic, randomly filled by ferromagnetic particles is measured. The measured elongation on cylinder-shaped samples displays shape dependence. A model based on the demagnetizing field and the effective Young's modulus is provided. Both calculation and measurement show a positive magnetostriction with larger values as the samples are flatter. The model is derived to have the behavior of the elongation as a function of the filling factor. An expression of the optimal filling factor, providing a maximal strain, is also expressed. © 2010 Elsevier B.V. All rights reserved.

Structure and magnetostriction of Tbx Dy0.9-x Nd 0.1 Fe1.93 (0.2

The paper tackles the analysis of eddy current induced by Villary effect in a magnetostrictive device for energy harvesting purposes. The study aims to focus on the basic loss mechanism which would strongly affect the global performances of these devices, usually employed up to hundreds of hertz.

We report a power supply-free, bidirectional electric current-voltage converter based on a coil-wound laminated composite of magnetostrictive alloy and piezoelectric crystal. An electric current applied to the coil induces a magnetic field, resulting in an electric voltage from the composite due to the direct magnetoelectric effect. Conversely, an electric voltage applied to the composite produces a magnetic induction due to the converse magnetoelectric effect, leading to an electric current from the coil. The converter exhibits excellent linear relationships between current and voltage. Compared with traditional current/voltage converters made by operational amplifiers, the advantages of the proposed device include low cost, no power consumption, and bidirectional conversion.

In this paper, a probability-based balance monitoring concept for humanoid robots is proposed. Two algorithms are presented that allow us to distinguish between exceptional situations and normal operations. The first classification approach uses Gaussian-Mixture-Models (GMM) to describe the distribution of the robot's sensor data for typical situations such as stable walking or falling down. With the GMM it is possible to state the probability of the robot being in one of the known situations. The concept of the second algorithm is based on Hidden-Markov-Models (HMM). The objective is to detect and classify unstable situations by means of their typical sequences in the robot's sensor data. When appropriate reflex motions are linked to the critical situations, the robot can prevent most falls or is at least able to execute a controlled falling motion. The proposed algorithms are verified by simulations and experiments with our bipedal robot BARt-UH. © SAGE Publications 2009 Los Angeles, London.

Long-range, torsional guided waves generated in pipes using magnetostrictive sensors (MsSs) have great potential for applications to the structural health monitoring (SHM) of hard-to-inspect pipes. This paper reports an improved MsS technique (when compared to related techniques currently used for the NDT of pipes) that uses polymeric magnetic tape material that is suitable for use in a variety of industries as an SHM tool for pipes. Improvements include increased efficiency, reduced cost and increased long-term survivability of the sensor system. Transduction efficiency was increased by reducing the sensor eddy current losses and by using a field concentrator strip. For long-term monitoring, a low-cost magnetic oxide based MsS material (video recording tape) having the required magnetic properties was used. The MsS strips were oriented to generate non-dispersive torsional guided ultrasonic waves that propagate long distances with minimal mode conversion. Further, considering both safety and long-term survivability of the sensor, low-power ultrasonic instrumentation was developed and tested. Measurements reported here demonstrate the sensitivity of this sensor to both radial notches (sawcuts) and drilled holes. Results also show that magnetic anisotropy of the strip plays a role in generating torsional waves. It is envisioned that results obtained from the present study will significantly enhance the ability to monitor the long-term structural health of piping systems. � IOP Publishing Ltd.

This paper describes and discusses the "STBU" speaker recognition system, which performed well in the NIST Speaker Recognition Evaluation 2006 (SRE). STBU is a consortium of four partners: Spescom DataVoice (Stellenbosch, South Africa), TNO (Soesterberg, The Netherlands), BUT (Brno, Czech Republic), and the University of Stellenbosch (Stellenbosch, South Africa). The STBU system was a combination of three main kinds of subsystems: 1) GMM, with short-time Mel frequency cepstral coefficient (MFCC) or perceptual linear prediction (PLP) features, 2) Gaussian mixture model-support vector machine (GMM-SVM), using GMM mean supervectors as input to an SVM, and 3) maximum-likelihood linear regression-support vector machine (MLLR-SVM), using MLLR speaker adaptation coefficients derived from an English large vocabulary continuous speech recognition (LVCSR) system. All subsystems made use of supervector subspace channel compensation methods-either eigenchannel adaptation or nuisance attribute projection. We document the design and performance of all subsystems, as well as their fusion and calibration via logistic regression. Finally, we also present a cross-site fusion that was done with several additional systems from other NIST SRE-2006 participants. © 2006 IEEE.

This paper describes and discusses the "STBU" speaker recognition system, which performed well in the NIST Speaker Recognition Evaluation 2006 (SRE). STBU is a consortium of four partners: Spescom DataVoice (Stellenbosch, South Africa), TNO (Soesterberg, The Netherlands), BUT (Brno, Czech Republic), and the University of Stellenbosch (Stellenbosch, South Africa). The STBU system was a combination of three main kinds of subsystems: 1) GMM, with short-time Mel frequency cepstral coefficient (MFCC) or perceptual linear prediction (PLP) features, 2) Gaussian mixture model-support vector machine (GMM-SVM), using GMM mean supervectors as input to an SVM, and 3) maximum-likelihood linear regression-support vector machine (MLLR-SVM), using MLLR speaker adaptation coefficients derived from an English large vocabulary continuous speech recognition (LVCSR) system. All subsystems made use of supervector subspace channel compensation methods-either eigenchannel adaptation or nuisance attribute projection. We document the design and performance of all subsystems, as well as their fusion and calibration via logistic regression. Finally, we also present a cross-site fusion that was done with several additional systems from other NIST SRE-2006 participants. © 2006 IEEE.

Proposes the compensation of the hysteretic behaviour of an actuator constituted by a Terfenol-D magnetostrictive material to enhance the performance of a typical control scheme for vibration suppression. Hysteresis is modelled by the application of the classical Preisach model whose identification procedure is performed by the adoption of fuzzy approximators. This allows analytic reconstruction of Everett integrals and the Preisach distribution function, without any special smoothing of the measured data, thanks to the altering capabilities of the fuzzy interpolators. Moreover, the idea of compensator for operators with memory is also described in detail and the concept of pseudo-compensator is introduced. The latter operator allows approximation of the inverse of a given Preisach-like operator and then to easily compensate hysteresis and nonlinearity of a real magnetostrictive actuator.

The magnetoelectric (100-x) BaTiO3 - (x) NiFe1.98 O4 (x=20, 40, 60, and 80 wt %) particulate composites have been prepared and the effects of size and interface are studied through microscopy measurements. Large magnetoelectric voltage coefficient (?E) values accompanied by large piezoelastic coefficient, large magnetostrictive strain coefficient, and an adequate interface contact between the magnetic and electric phases were observed in these nanocomposites. The nanocomposite with x=40 has an ?E value of 252 mV cm-1 Oe-1, which is the largest value for any particulate magnetoelectric composite, based on the available open literature. � 2009 American Institute of Physics.

A magnetostrictive transducer operating at 100 kHz using rare earth transition metal giant magnetostrictive material for nondestructive testing (NDT) applications was designed and fabricated. The giant magnetostrictive Tb0.3 Dy0.7 Fe2 material was chosen as the active element for the present purpose. From the impedance measurements, the resonant frequency of the transducer is found to be 100 kHz. The performance of the transducer was validated by carrying out NDT on a test concrete block with delaminated regions, using the ultrasonic through-transmission technique and the pitch-catch method. � 2008 American Institute of Physics.