Magnetostrictive Vibration Research Articles

S043012 磁歪振動発電・圧電ファイバを組込んだワイヤレスタイヤセンサの試作([S043]減災・サステイナブル工学)

S043012 磁歪振動発電・圧電ファイバを組込んだワイヤレスタイヤセンサの試作([S043]減災・サステイナブル工学)

Magnetostrictive vibrator utilizing iron–cobalt alloy

In this paper, a novel magnetostrictive vibrator with a unique and integrated design is proposed and developed by using a kind of iron–cobalt alloy (Permendur). Permendur is a giant magnetostrictive material (GMM) with magnetostriction exceeding 70ppm, Young's modulus of 210GPa, high relative permeability and sufficient force for actuation, which shows a good performance as actuator material and has been drawn a lot of attention. The magnetostrictive vibrator has four legs around which the coils are wound. The legs can be pushed (expansion) and pulled (contraction) independently through controlling the input currents of the coils. The actuation principle of the magnetostrictive vibrator is illustrated. The lateral vibrating motion can be generated by using a pair of opposing coils, whereas 2D vibrating motion can be obtained by using two pairs of opposing coils. The finite element analysis (FEA) is adopted to analyze the vibration mode and assist the concrete design of magnetostrictive vibrator. Through some fundamental experiments, the characteristics of the magnetostrictive vibrator are evaluated. For the application, it has been successfully used as a vibrating polisher in the ultra-precision finishing of micro-optic molds.

Finite element analysis of magnetostrictive vibration energy harvester

PurposeThe paper aims to analyze the behavior of the Galfenol rods under bending conditions that are employed in a vibration energy harvester by illustrating the spatial variations in stress and magnetic field.Design/methodology/approachThis paper describes a 3‐D static finite element model of magnetostrictive materials, considering magnetic and elastic boundary value problems that are bidirectionally coupled through stress and field dependent variables. The finite element method is applied to a small vibration‐driven generator of magnetostrictive type employing Iron‐Gallium alloy (Galfenol).FindingsThe 3‐D static finite element modeling presented here highlights the spatial variations in magnetic field and relative permeability due to the corresponding stress distribution in the Galfenol rods subjected to transverse load. The numerical calculations show that about 1.1 T change in magnetic flux density is achieved which demonstrates the effectiveness of the inspected vibration‐driven generator in voltage generation and energy harvesting. The model predictions agree with the experimental results and are coherent with the magnetostriction phenomenon.Originality/valueThis paper fulfils the behavior analysis of Galfenol rods under transverse load that includes both compression and tension. The compressive and tensile stresses contributions to change in magnetic flux densities in the Galfenol rods were calculated by which the effectiveness of the inspected vibration‐driven generator in voltage generation and energy harvesting is demonstrated.

A Railway Running Status Monitoring System based on Energy Harvesting Wireless Sensor Network

In order to meet the requirement of train running status monitoring in railway environment and according to the landform characteristics in the rail laneway, this paper introduced a reliable railway running status monitoring system based on energy harvesting wireless sensor networks (EH-WSN). The sensor node of the system mainly composed of a magnetostrictive vibration energy harvester, an energy storage element, and a wireless single chip microcomputer. The sink node is placed in the railway station with stable power supply to communicate with monitoring server. The design of hardware and the flow chart of software are given. Through experiments in a railway workshop, we check the transmission characteristic at 2.4 GHz, and also make sure that while the distance between two wireless sensor nodes is 60 meters, the system can run successfully and monitor the status of the track in real-time. This makes a good supplement to the existing railway monitoring system.

Micro Polishing of Tungsten Carbide Using Magnetostrictive Vibrating Polisher

Micro structured glass lenses are highly required in new fields such as Micro channels, Fresnel lenses for solar panels and Wafer Level Cameras (WLC). The glass lenses are moulded bypress moulding with micro ceramics moulds made of tungsten carbides (WC). In this paper, a new Vibration Assisted Polishing (VAP) method is proposed and developed by using circular vibration of the magnetostrictive vibrating polisher. The polisher is composed of a magnetostrictive vibrator and a small polishing tool, and the small polishing tool is mounted on the head of the magnetostrictive vibrator. The concrete design of the magnetostrictive vibrating polisher is assisted by the finite element method (FEM) and through vibration mode analysis, the 4th mode is selected. It generates a circular vibration trace at a frequency of 9.2 kHz with a radius of 30 μm. The polisher is fixed in a 5-axis (X, Y, Z, B and C) controlled polishing system. Through some fundamental polishing experiments, the shapes of the removal function is acquired and surface roughness is reduced to 9 nm Rz (1 nm Ra).

The Influence of Remanence on Magnetostrictive Vibration and Hysteresis in Mn-Zn Ferrite Cores

Previously, experimental results have been presented showing that Mn-Zn ferrite core losses rise significantly with dc bias levels due to an increase in magnetostrictive vibration. In addition, it has been shown that the presence of a high level of remanent flux density, Br, left within a core after the removal of a dc bias can significantly increase core losses and, therefore, influence the hysteresis loop shape. In this paper it is shown that this loss mechanism is rate-independent in nature; furthermore, it is proposed to originate from regions of irregular stress that are dependent on the magnetostrictive vibration of a core. Accordingly, it is also proposed that certain parameters of the Jiles-Atherton (J-A) model must be modified, in order to allow influence of Br on hysteresis loops to be shown. These modifications are consistent with the real physical effects experienced by a ferrite core in the presence of a high level of Br.

J044105 磁歪材料を用いた振動物体からのエネルギーハーベスト

Up to the present, by using the Terfenol-D (Tb-Dy-Fe alloy from ONR/USA) giant magnetostrictive alloys containing rare earth elements, there was an example of measuring power generation due to vibration of the impact force and compression force of the uniaxial direction. Terfenol-D has been limited field of application because it is brittle but high cost. In this study, we investigated the characteristics of the vibration generator when two magnetostrictive alloys of magnetostrictive FeCo-and FeGa, in that way, the inverse magnetostrictive effect of magnetostrictive material is used, and the beam is vibrated and paste the magnetostrictive material plate to the cantilever. A leakage flux is generated by the inverse magnetostrictive effect distortion due to vibration, so that the induced currents generated by the change in magnetic flux of time were compared for each material. So, in addition, we also measured and compared the amount of magnetostriction and magnetization characteristics. As a result, important finding that applied stress and the amount of magnetostriction are strongly related with the output voltage of the magnetostrictive vibration generator.

Magnetic properties of Fe80−xCoxZr7Si13 (x = 0 – 30) amorphous alloys

Amorphous Fe80−xCoxZr7Si13 (x = 0 – 30) alloys, in which boron was completely replaced by silicon as a glass forming element, have been prepared by melt quenching. Partial substitution of iron by cobalt causes the increase of the hyperfine fields from about 19 to 27 T for x = 0 and 30, respectively, as revealed by conventional Mössbauer spectroscopy. The specialized rf-Mössbauer technique permitted us to estimate the soft magnetic properties of the alloys. The rf-collapse effect, which is very sensitive to the local anisotropy field, is observed for all amorphous FeCoZrSi alloys revealing that they are magnetically very soft. The rf-sidebands intensities, which are related to the magnetostriction, increase with the increase of Co content in the alloys. In Fe60Co20Zr7Si13 and Fe50Co30Zr7Si13 samples the rf field exposure induced partial crystallization that was attributed to mechanical deformations related to high frequency magnetostrictive vibrations forced by the rf field. The magnetostrictive origin of this effect was supported by the measurements of magnetostriction constants of the studied alloys. Measurements of the hysteresis loops revealed that coercivity increases for higher Co content.

The Impact of Vibration Due to Magnetostriction on the Core Losses of Ferrite Toroidals Under DC Bias

The ferrite cores of transformers and inductors are commonly excited under dc bias conditions in power electronic circuitry. Results have previously been presented showing core losses increase significantly with dc bias, along with various explanations for the cause. This paper presents measurements showing a strong correlation between core losses, and the magnetostrictive vibration caused by the presence of a dc bias. The measurements are made on power grade material ferrite toroidal cores at frequencies equal to, and distant from magnetomechanical resonance. Based on this evidence it is proposed that a mechanism causing core losses to increase with dc bias is the increase in vibration with dc bias, with losses being dependent on the amplitude and nature of the vibration waveform. The means by which core losses increase with vibration are also described.

A Magnetostrictive Force and Vibration Mode Analysis of 3 kW BLDC Motor by a Magneto-Mechanical Coupling Formulation

This paper proposes a method to calculate magnetostrictive forces, displacement, and vibration modes of a large-scale Brushless DC(BLDC) motor by using a magneto-mechanically strong coupling formulation. The force is calculated using the energy method with magnetostrictive stress tensor. The mechanical vibration modes are also analyzed by using the principle of Hamilton and the calculated magneto-elastic forces acting on the surfaces of the stator. To verify the algorithm, 3 MW BLDC motor is simulated, and the forces, displacements, and vibration modes are calculated. The result shows that the mechanically stressed core has more deformation or displacements than those of the normal condition.

Human power-based energy harvesting strategies for mobile electronic devices

Energy problems arise with the proliferation of mobile electronic devices, which range from entertainment tools to life saving medical instruments. The large amount of energy consumption and increasing mobility of electronic devices make it urgent that new power sources should be developed. It has been gradually recognized that the human body is highly flexible in generating applicable power from sources of heat dissipation, joint rotation, enforcement of body weight, vertical displacement of mass centers, and even elastic deformation of tissues and other attachments. These basic combinations of daily activities or metabolic phenomena open up possibilities for harvesting energy which is strong enough to power mobile or even implantable medical devices which could be used for a long time or be recharged permanently. A comprehensive review is presented in this paper on the latest developed or incubating electricity generation methods based on human power which would serve as promising candidates for future mobile power. Thermal and mechanical energy, investigated more thoroughly so far, will particularly be emphasized. Thermal energy relies on body heat and employs the property of thermoelectric materials, while mechanical energy is generally extracted in the form of enforcement or displacement excitation. For illustration purposes, the piezoelectric effect, dielectric elastomer and the electromagnetic induction couple, which can convert force directly into electricity, were also evaluated. Meanwhile, examples are given to explain how to adopt inertia generators for converting displacement energy via piezoelectric, electrostatic, electromagnetic or magnetostrictive vibrators. Finally, future prospects in harvesting energy from human power are made in conclusion.

Crystallization of amorphous alloys induced by the radio frequency magnetic field

The effect of the rf field induced crystallization of Co-containing amorphous alloys, observed in the rf-Mössbauer study of Fe81−x−yNixCoyZr7B12 alloys, is discussed in detail. This effect was attributed to mechanical deformations originating from magnetostrictive vibrations induced by the rf field (rf-sideband effect). The rf field induced crystallization is particularly large for high magnetostriction Co-containing alloys, and it does not occur in the Co-free alloys with smaller magnetostriction. The magnetostriction origin of the crystallization effect induced by the rf field is supported by the measurements of the magnetostriction constants of the alloys studied.

Magnetostrictive Vibration Actuator with Improved Characteristics at Low Frequencies

Giant magnetostrictive element has an advantage in excitation force at high frequencies, but has a weakness in the ability to produce vibration power at low frequencies. The purpose of this paper is to develop a new vibration actuator with improved characteristics at low frequencies by using electromagnetic force to assist the magnetostrictive element. A prototype of the actuator is designed and fabricated. The characteristics of the actuator are measured. The results of measured acceleration or force show an efficient excitation at high frequencies due to magnetostrictive element. It is also shown that the electromagnetic force improves the characteristics at low frequencies where the acceleration amplitude is flat at frequencies below 1kHz. It is confirmed that the magnetostrictive force and electromagnetic force are cooperatively working in this actuator. In addition, the actuator has an advantage in easiness of attachment to or removal from the wall because it sticks to the wall with magnetic force derived from the magnet equipped to produce bias magnetic flux in the magnetostrictive element. This allows flexible location selection of actuators when the actuators are used for vibration control.

Magnetorheological Valve for Hybrid Electrohydrostatic Actuation

There is an increasing demand for compact actuators capable of producing large deflections, large forces, and broad frequency bandwidths. Due to their solid state nature, smart materials can enable novel actuator solutions that compete favorably with established technologies based on electric, hydraulic, or pneumatic motors. However, in all existing active materials, large force and broadband responses are obtained at small displacements and methods for transmitting very short transducer element motion to large deformations need to be developed. We present a new hybrid actuator which operates on the principle of rectification of magnetostrictive vibrations by means of magnetorheological (MR) flow control. Experiments and theoretical calculations are aimed at substantiating the feasibility of the hybrid actuator and establishing design criteria for the development of an effective MR valve. The experiments presented here demonstrate the ability of the valve to completely block the flow due to the combined action of a pressure differential and MR fluid activation. For characterization purposes, two variations of the main valve concept are considered, one with moving coils and the other with fixed coils. Actuation measurements conducted on the complete actuator show deflections of 6.5 in. in response to fluid inputs produced with a hydraulic piston in combination with an applied quasistatic voltage of amplitude 5 V. A system-level model is presented which is developed by treating the system as an RLC equivalent electrical circuit with operation across electrical, mechanical, and fluid domains. Attributes and shortcomings of the model are discussed through comparison of model results with experimental data.

Ｆｅ‐Ｇａ合金（Ｇａｌｆｅｎｏｌ）を用いたマイクロ磁歪振動子

Micro magnetostrictive vibrator using Iron-Gallium alloy (Galfenol) was investigated. Galfenol is an iron-based magnetostrictive material with the magnetostriction more than 200 ppm, high permeability μr > 100 and Young's modulus of 70 GPa. The material is machinable to free of the shape by conventional cutting process, and sustainable for tensile, bending, and impact. Micro actuator using Galfenol equipped with iron yoke and winding coil, therefore, has advantages over PZT type, in simple, low voltage driving, high robustness and wide temperature operation range. This paper describes the performance of a micro vibrator improved to our previous prototype, in configuration, material, and fabrication process. The vibrator using stress-annealed Galfenol machined to the rod of 1mm diameter was observed the displacement of 1.2μm, high bandwidth of 30 kHz and high tensile robustnesswithstanding suspended weight of 500g. The vibrator was also verified useful as speaker which can generate clearsound from the power of a portable music player.

Magnetostrictive Vibration Sensor based on Iron-Gallium Alloy

ABSTRACTThis work characterizes magnetostrictive single crystal Fe84Ga16 (Galfenol) as static and dynamic sensor in bending mode. Galfenol patch bonded to a cantilevered aluminum beam was characterized for static and dynamic loading of the beam. A figure of merit has been defined and sensor parameters have been obtained for different stress conditions and Galfenol patch thickness. Issues related to application in static and dynamic sensing have been discussed.

Magnetostriction and motor vibration

AbstractA quiet induction motor is strongly demanded today. Electromagnetic factors are a main cause of vibration and acoustic noise in a small induction motor. Electromagnetic forces and magnetostrictive forces are considered as the origin of electromagnetic vibration and noise. In this paper, magnetostrictive vibration of a ring of electrical steel sheets was simulated by the mechanical finite element method. Magnetostriction was assumed as external forces and they were added at each node of the meshed ring. Resonant frequency and the mode of the ring were calculated. In the steel sheet ring excited by a PWM voltage source inverter, the frequency spectrum of vibration of ring was measured and compared with the calculated results. It was confirmed that these procedures simulated magnetostriction behavior of electrical steel sheets. Furthermore, the electromagnetic forces of a small induction motor were calculated and compared with the magnetostriction data. It became clear that electromagnetic vibration was affected by the magnetostriction of steel. These results will be useful in the reduction of acoustic noise and the development of quiet motors. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(2): 8–13, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10338

Optimum driving of magnetostrictive amorphous wire micro-motor

Abstract Characteristics of a magnetostrictive vibration micro-motor were investigated in relation to a supporting position of a magnetostrictive amorphous wire for optimization of the motor. It was found that a vibration of the wire resembled a vibration mode of both ends free and a maximum rotational speed was obtained by supporting the nodes of vibration.

High Bandwidth Tunability in a Smart Vibration Absorber

An electrically tunable vibration absorber based on the strong δ E effect of Terfenol-D has been developed. A general description of tuned vibration absorbers is presented along with a description of the magnetostrictive effects that make an electrically tunable Terfenol-D vibration aborber function. It is emphasized that the large modulus changes achievable with the proposed magnetostrictive vibration absorber arise as a consequence of the stiffening of the crystal lattice as the magnetic field is increased from the demagnetized state to magnetic saturation. This is in contrast to the small modulus changes often reported in the literature which are achieved by operating smart materials between their open- and short-circuit states. Experimental results are presented that show agreement with prior art and demonstrate control of a magnetostrictive actuator resonant frequency between 1375 Hz and 2010 Hz by electrically varying the elastic modulus of a magnetostrictive material. This operating principle is then implemented to obtain high bandwidth tunability in a Terfenol-D vibration absorber.

巨大ジャイロ磁気効果マイクロモータ

High-speed rotation of amorphous wire in an ac longitudinal field was investigated in relation to magnetostrictive vibration for Fe, Fe-Co, and Co based wires. It was found that high-magnetostriction Fe and Fe-Co based wires rotate around the wire axis, but low-magnetostriction Co based wire does not, and that the rotational speed is a linear function of magnetomechanical resonance freqency. It seems from these observations that the rotation of amorphous wire around its axis originates from the magnetostrictive vibration.