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Abstract
According to inverse magnetostrictive effect, the dynamic magnetic field of giant magnetostrictive material (GMM) under magnetoelastic force in magnetization process was derived based on the minimal value principle of energy combining with magnetic theory. Then the frequency characteristics of eddy current loss, hysteresis loss and complex permeability were studied. The simulative and experimental results were used to analyze the influence of magnetic loss on the temperature rise characteristic of giant magnetostrictive actuator (GMA). These results indicate that the calculational result of the eddy current loss is in a good agreement with that of the simulation, so the calculation method can be used to study the loss of GMM under low-middle frequency, and the change of complex permeability under high frequency increases hysteresis nonlinearity of magnetic field. Also it indicates that the axial temperature distribution of GMM in actuator varies with the frequency. The experimental result confirms the validity of calculation and simulation. Finally the effect of forced water cooling in GMA is discussed, and the above studies have a significant guidance for the analysis, design and application of GMA.
... And the output of the GMA may vary a lot as well. 26 As a result, while working in dynamic condition, it is necessary to identify and adjust the parameters online to better predict the output of the GMA. However, identication methods available usually rely on a large number of iterations to obtain a satisfactory solution, especially intelligent algorithms, which have relatively high precision. ...
Giant magnetostrictive actuator (GMA) suffers dominant hysteresis nonlinearity while working. In order to better predict its output, a dynamic model of GMA based on the J-A model is established. On the foundation of the model, an online parameter identification method is proposed. Classified into two types, some parameters are determined by physical theories, while the others are identified by a sensitivity-based identification method. Serving as the identification algorithm, the particle swarm optimization (PSO) algorithm is modified to accelerate the identification process. Moreover, to validate the effectiveness of the proposed method, an online parameter identification system is designed as well as identification software. Experimental results prove that the proposed system performs well and is fit for online identification.
... It points out that the prestress can affect the size of the magnetostrictive strain, but there are very few collected data and the status signals are not highly precise [1] . The driving frequency has loss effect on GMA, but it failed to give the direct relationship between the frequency and output displacement [2] . Bias magnetic field affects the efficiency of Giant Magnetostrictive Material(GMM), coupling coefficient, permeability and other coefficient, but the data acquisition system is too complicated [3] . ...
... Since the 1970s, GMM as a kind of strategic functional materials got a fast development and was widely employed in the aerospace engineering, ocean, geology, measuring instrument, machinery, national defence and medical technology through taking advantage of its own features such as Joule effect, Villari effect, Wiedemann effect, Matteucci effect, ∆E effect and so on [1][2][3][4]. A large number of experimental results show that the coupling field of electricitymagnetism-machinery-hot and nonlinearities significantly exist in the GMA between its input current and output displacement which will destroy the property seriously [5][6][7][8]. The exciting coil as the only driving field is the source of the electromagnetic conversion and its parameters are the key factors to improve the efficiency and closely related to the frequency characteristic and stability control. ...
Exiting coil as the center of the electromagnetism conversion is mainly to provide driving magnetic field for the giant magnetostrictive actuator (GMA) and control its output displacement through inputting different current. Therefore, the structural parameters of the exiting coil are the key factors to improve the electromagnetic conversion efficiency and make GMA effect sufficiently. This paper designs and optimizes parameters of the exiting coil according to the designing principles that are high uniformity and intensity of the magnetic field near giant magnetostriction materials (GMM) rod, minimum heat loss and compact-sized through analyzing the working conditions of the GMA. Then, the magnetic circuit with the optimized excitation coil is analyzed based on Ansoft. The result indicates that the distribution of magnetic field is more uniform and the uniformity rate is raised to be 99.35%.
The magnetic and elastic parameters of the Terbium Dysprosium Iron (abbreviated as TFD)giant magnetostrictive material are important fundamental parameters for the design of magnetostrictive transducer based on the piezomagnetic analogy method. Therefore, the study of temperature characteristics of magnetic and elastic parameters of giant magnetostrictive material can help to grasp the law of temperature influence on the working performance of the giant magnetostrictive transducer. In this paper, the variation patterns of magnetic and elastic parameters with temperature for a total of three tangential types of giant magnetostrictive material samples, including the sample along the magnetostrictive direction(TFD-1#), the sample perpendicular to the magnetostrictive direction(TFD-3#) and the sample at an angle of 45° to the magnetostrictive direction(TFD-2#), were comprehensively measured under different external magnetic field conditions. The experimental results showed that: The magnetostriction coefficient is linearly related to the external magnetic field in the range of 10MPa pre-stress and 50∼150kA/m external magnetic field (the same below), corresponding to the dynamic operating range of the magnetostrictive transducer. In this interval, the magnetostrictive strain constants d31 and d33 show a single-peak pattern of increasing and then decreasing with increasing external magnetic field, it changes slowly and modestly with increasingly temperature; The relative permeability of the giant magnetostrictive materials μr11 and μr33 decreases with increasing external magnetic field and temperature at an external magnetic field below 150kA/m; The elastic constant increases with increasing external magnetic field and decreases with increasing temperature.
Giant magnetostrictive material (GMM) has the nature of high energy density and relatively high thermal conductivity, but it is sensitive to temperature. Therefore ambient temperature significantly affects the operational performance of GMM. The effect of temperature on the dynamic output characteristics of GMM transducer is analyzed with finite element software COMSOL Multiphysics in this paper. The results show, under the same loading time with increasing temperature, the amplitude and aftershock of the transducer output displacement decreases and output frequency is close to 7.5 kHz; under the room temperature of 20°C with shortening loading time, amplitude first increases and then decreases while aftershock significantly enhance and the output frequency has a slight increase; when Young modulus is considered, with rising temperature the amplitude of output displacement markedly decreases and aftershock reduces slightly and output frequency is less than 10 kHz.
Giant magnetostrictive actuators (GMAs) have received considerable attention in recent years and are becoming increasingly important in the exploitation of new type electromechanical devices. The performance of giant magnetostrictive actuator (GMA) is generally determined by the precision of the GMA output displacement; however, the heat-induced displacement of a GMA is the principal element influencing the precision of the GMA output displacement. In this paper, a precise GMA with a heat-induced displacement suppression system is developed; the heat-induced displacement control mechanism consists of a temperature control module and a thermal displacement compensation module. Based on the heat-transfer rules, a GMA heat-transfer mathematical model and a GMM rod heat-induced displacement model are built; next, the mathematical models of GMA heat-transfer are solved and the temperature distribution, the heat-induced displacement, and the heat transfer rate of GMA are completely obtained. Finally, a test system for a GMA heat-induced displacement suppression system is implemented, and an experimental study of the system is performed. The results of the GMA heat-induced displacement by experimental research basically coincide with the results of the GMA heat-transfer mathematical model, that is, the GMA temperatures are controlled to below 35 degrees C and the GMA heat-induced displacement remains within a small range under an input current of 1 A for a period of continuous operation of 80 mm. The system observably improved the precision of the GMA output displacement; as a result, the research results provided a basis for a precise micro-displacement GMA.
The complex permeability variation measurements at microwave frequencies of a magnetostrictive/piezoelectric bilayer under different values of a dc electric field are reported. A 25% variation of the initial permeability is achieved under a 1.5times10<sup>6</sup> V/m static electric field
The magnetic field distribution model in the giant magnetostrictive materials rod is build by means of Maxwell's equation combining with the piezomagetic theory. The magnetic field distribution function in the giant magnetostricive materials rod is derived. In the inner magnetic field distribution function, the magneto-electric characteristic parameters of the material are induced. The influence of the material characteristic parameters on the inner magnetic field distribution and eddy current loss of the material are discussed. The results indicate that the inner magnetic field of the material not only has relations with the external magnetic field but also with the material piezomagnetic coefficient, Young's modulus and the relative magnetic permeability. Meanwhile, the hysteresis characteristic exists between the inner magnetic field and the external magnetic field; the material radius when material inner eddy current loss under condition of considering the material characteristic parameters reaches its maximum will be larger than the material radius without considering the material characteristic parameters, and the change trend of the eddy current loss will also becomes moderate. No matter how the material magneto-electric parameters change, the basic law of the magnetic energy loss doesn't change in the giant magnetostrictive rod.
Based on the Jiles-Atherton model and structural dynamics principle of transducer, the magnetoelastic dynamic strain model of giant magnetostrictive transducer was developed, which considered the eddy current losses and the variety of stress. Model simulations were compared with experiments at various drive levels and frequencies of operation. Simulation results are in a good agreement with the experimental ones. This indicates that the dynamic strain model can describe the relation between the applied field and the output vibration. The Bode diagram was obtained based on the calculation results of the model. This work is very useful to design the controller of transducer.
The magnetization and magnetostriction of a variety of Laves phase rods of TbxDyyHo1-x-yFe1.95 grown in the form of [112] oriented dendritic platelets were measured as a function of magnetic field H(-2200 < H < 2200 Oe), compressive stress (20, 30, and 40 MPa), and temperature T(-60 < T < 80 degrees C). Compared to Terfenol-D (Tb0.3Dy0.7Fe1.95), Ho containing alloys can have lower hysteresis with only slightly lower magnetostriction. Sample compositions were chosen both along a line of minimum near room-temperature anisotropy (Tb0.3Dy0.7Fe1.95-Tb0.20Dy0.22Ho0.58Fe1.95) and at Ho-0.15 and Ho-0.30 across the line. (C) 2000 American Institute of Physics. [S0021-8979(00)16208-5].
The giant magnetostrictive materials, such as Terfenol-D, present more applications as a new type functional material. As a new type of device which transfers electromagnetic energy to mechanical energy, Giant Magnetostrictive Actuator (GMA) using Terfenol-D can be used in micro-orientation system, precision mechanical processing, micro-valve system, active-vibration control system, etc. Based on the finite element method, we designed several GMAs. This paper presents a theoretical and experimental study of dynamic properties of Terfenol-D actuators at varied operating conditions. The varied operating conditions include varied magnetic bias, varied AC applied magnetic field amplitude and frequency. A set of dynamic stain of GMA system versus different magnetic bias, dynamic strain versus different exciting magnetic field amplitude and frequency (from 50Hz to 800Hz) are compared. The varied trends of material properties, such as permeability and axial strain coefficient are also obtained from the experimental results. These dynamic property trends are very helpful to be used in optimization of GMA structural design and in establishing the mathematic model of the GMA system.
The frequency response of the magnitude and phase of the dynamic relative permeability of Terfenol‐D (Tb 0.27 Dy 0.73 Fe 2 ) has been measured for low drive fields (a few hundred A m<sup>-1</sup> rms) and the energy loss per cycle determined. The data shows that when eddy current shielding is not significant, the frequency dependence of the magnitude of this energy loss follows that calculated from classical eddy current theory, suggesting that there is negligible anomalous loss. The permeability, along with the dynamic strain coefficient, is observed to possess a flat response with frequency up to the value at which eddy current shielding of the sample core is expected to be significant. However, the ratio of the dynamic strain coefficient to the dynamic susceptibility (d/χ) remains independent of drive frequency, suggesting that the magnetization processes do not change. Measurements using high drive fields show that at 5 kA m<sup>-1</sup> rms the frequency dependence of the loss is still in good agreement with classical eddy current theory. This data also shows that the loss angle is identical to that measured at low drive fields, indicating that the eddy current losses scale as the square of the drive field.
Si microcantilevers coated with giant magnetostrictive Sm-Fe or
Tb-Fe thin films are fabricated and the deflection of the cantilevers is
measured as a function of magnetic field. In the case of a
microcantilever with the dimension 3.7 mm (length)×1.0 mm
(width)×13 μm (thickness), for example, a very large deflection
of 52 μm is achieved at 150 Oe from the first ascending magnetic
field, by the coating of a Sm<sub>42.7</sub>Fe<sub>56.9</sub>B<sub>0.4
</sub> thin film with the thickness of 1.2 μm. Total deflection
doubles when a magnetic field of the same amplitude (150 Oe) is applied
alternately in the length and the width directions. Relatively large
deflections are also observed for Tb-Fe thin film based microcantilevers
as well as other Sm-Fe based cantilevers. The level of deflection
achieved In the present magnetostrictive microcantilevers is considered
to be suitable for microdevices applications
Based on the Jiles-Atherton model and transducer's structural dynamics principle, the magnetoelastic dynamic strain model of giant magnetostrictive transducer is founded. This model takes into account the eddy current losses and the variety of stress. Simulation results are in a good agreement with the experimental ones. This indicates that the dynamic strain model can characterize the magnetization intensity and strain behavior at different frequency. The proposed model is suitable to describe the relation between the applied field and the output vibration at a wide range of exciting frequency