A magnetic anisotropy sensor (MAS) is a probe-type sensor capable of non-contact, non-destructive measurement of stress in ferromagnetic materials. The output voltage of the MAS is induced by a directional difference of relative permeabilities caused by the inverse magnetostrictive effect.
It is often necessary that the internal stress distribution in the direction of depth should be clarified. By changing the MAS exciting frequency, it is possible to searching for the different depth stress. This paper proposes a method for measuring the stress distribution in the direction of depth. Furthermore, this paper shows that the stress distributions in the measurement surface and opposing surface can be estimated from the MAS output.
In this paper we discuss the followings:
(1) By developing a stress-electric conversion theory of the MAS, it is clarified that the output voltage is proportional to the principal stress differences.
(2) Using punched thin steel sheet as a specimen, by changing the exciting frequency, the measurements from one side makes it possible to estimate the stress in the opposite surface.
(3) Conversion of the principal stress differences to relative permeabilities reveals that tensile stress remains in the upper surface, and compressive stress exists in the lower surface.

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超磁歪材料を用いた音響振動素子の磁気回路解析, 振動解析について述べた.超磁歪材料は, 応用する上で比透磁率の低いこと, 定数が使用状況によっては定数でなくなることなどから厳密な解析はなかなか困難である.しかし, 超磁歪材料はひずみ量が大きく, 魅力に富む材料である.

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We are investigating a large-scale displacement sensor using a magnetostrictive wire with torsional and longitudinal elastic waves.
Until now, many differential transformer and potentiometers have been used as displacement sensors in the industrial field. The displacement sensor described in this paper, however, measures displacement by using magnetostrictive wire. The advantage of this sensor is its non-contact, high-precision displacement measurement.
We examined the generation and detection of torsional and longitudinal elastic waves. This paper describes the result of measuring how much the magnetostriction and elastic wave detection property of magnetostrictive wire are affected by heat treatment and demagnetization. It is shown that the treatment and demagnetization methods have different effects on longitudinal elastic waves and torsional waves.

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This paper describes a long-scale displacement sensor using a magnetostrictive wire with a measurement range of over 10 m. Since the sensor is a non-contact type that measures the propagation time of the elastic wave transmitted in the wire, it is thought to be suitable as a displacement sensor for transportation systems. However, no sensor of this type with a range of over 5 m has been reported in practical use hitherto. In order to develop a long-scale displacement sensor, it was considered that two detection methods should be compared experimentally: One using an AE sensor, and the other using a detection coil. The experimental results showed that the method using a detection coil is more stable and has a lower attenuation coefficient of the elastic wave detection voltage versus distance than the method using an AE sensor.

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The magnetic anisotropy sensor (MAS) is noncontactly able to measure the mechanical stresses of ferromagnetic materials. The output voltage is caused by the inverse magnetostrictive effect. To measure tensile or bending stress, MAS output voltage − each stress characteristic was needed. This paper deals with the relationship of MAS output voltage for tensile and bending stresses. The output voltage on bending stress is calculated using the output voltage ratio and output voltage-tensile stress characteristics. Thus, MAS can measure both the tensile and bending stresses using output voltage- tensile stress characteristics.

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A high-speed hydraulic servo valve using a linear dc motor (LDM), which has the LDM's yoke made of a carbon steel (S 15C), has been developed by the authors. To simplify the manufacturing process for the LDM's yoke, the use of spheroidal graphite cast iron (FCD450) is considered. This paper describes the dc and ac magnetization characteristics of S15C and FCD450, and the static and kinetic characteristics of two LDMs made of S15C and FCD450, respectively.The following conclusions are reached: (1) the maximum magnetic flux densities of S15C and FCD450 at a magnetizing field of 5 kA/m are 1.63 T and 1.31 T, respectively, (2)the maximum static thrusts of two LDMs made of these materials a t an exciting current of 7 A are 91 N and 82 N.respectively, and (3) the frequency response of two LDMs made of these materials are 420 Hz and 370 Hz, respectively.

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The magnetic anisotropy sensor (MAS) is able to measure the mechanical stress of ferromagnetic material noncontactly. This paper deals with the conversion theory of MAS output voltage utilizing directional permeability distribution that assumed an elliptical form in the specimen. Relative permeability is proportional to the stress. Theoretical expression of the output voltage is derived from the concept of directional permeability distribution. The calculated curves of the output voltage have a comparatively good approach to the measured value due to the change of stress.

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Steel wire rope has a complicated structure that is made by twisting a large number of steel wires together. We propose finite-element modeling for the analysis of the magnetic flux leakage testing of wire rope. The first step is modeling a simple model for analysing the state of magnetization of the wire rope under a magnetic yoke, where wire rope is considered to be a pipe. In the second step, a detailed model is used for the evaluation of flux leakage around wire breaks, where the wire rope is expressed as a single bundle of straight wires or strands. The results obtained from these numerical analyses of the proposed models are useful for quantitative evaluation of wire rope testing.

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　Glassy alloys have exceptional soft magnetic properties. It has an advantage that shaping is possible by thermal spraying method and ideal coercive force of Glassy alloys is zero as same as other amorphous metals. Glassy alloy's magnetic properties will be improved by control of internal stress and grant of induced magnetic anisotropy with heat treatment. In this paper, we fabricated ring and cylinder samples of two kinds Glassy alloys and evaluated its magnetic property. As a result, we found the relative permeability of ring samples is about 400 and that of cylinder samples is about 120. Residual magnetization of cylindrical magnetic shield is about 0.10 mT. Transverse shielding factor for AC magnetic field is about 10.

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The goal of this study is to develop a device which is used to both energy storage and wireless power transfer for ultra-low energy applications. It is a flywheel-like device with new concepts. This device consists of a rotating module and magnetic energy harvesting module. The rotating module is a rotating mechanical device that is used to store not only rotating energy but also magnetic energy. To make it simple and low costs, we use a geared-shape magnetic material between two antiparallel magnets. The magnetic energy harvesting module is an “on demand” power receiver device that is used to convert magnetic energy to electric energy. This paper focuses on this wireless power transmission performance. We consider the magnetic core shape for the magnetic energy harvesting module, and evaluate the harvesting power and its efficiency as a function of distance between two modules.

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The thrust of a linear DC motor (LDM) depends on the magnetic characteristics of the magnetic material used for the yokes. It is thus necessary to clarify the relation of this material and the thrusts in order to design LDMs easily. This paper considers the relation for a thin (under 40-mm-thick) LDM with a long stroke (105 mm) on the basis of measurements. The results of the measurements were as followings; (1) the maximum magnetic flux density shows a tendency to be saturated at 10 kA/m in the five measured magnetic materials, (2) the thrust constant was saturated, and (3) the saturated value of the thrust constant of LDMs is proportional to the maximum magnetic flux density of the magnetic material used for the center yoke.

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This paper presents an energy strage and wireless power transmission system for energy harvesting. This system consists of sabonius windmill, rotating module and magnetic energy harvesting module. The sabonius windmill converts the wind energy to rotation energy of both the windmill and rotating module. The rotating module also can provide the power to the magnetic energy harvesting module with magnetic energy. From experimental results, the storage enegy of the system, provided power to the load and energy losses in the system are considered. Compared with a DC generator, advantages of the system are discussed.

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The magnetic anisotropy sensor (MAS) is a stress sensor that detects internal stresses induced by the inverse magnetostrictive effect. In this study, the sample is a cold rolled steel plate used for a car body. Because the penetration depth of flux is greater than the thickness of the sample, 0.75 [mm], the MAS detects the average of the internal stress distribution Therefore, the output voltage is affected by the internal stress distribution. The flux density distribution in the sample caused by the skin effect is varied with the excitation frequency. This paper shows that the internal stress distribution can be estimated from the output voltage-excitation frequency characteristics.

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It is important to measure mechanical stress with a non-destructive method for magnetic materials. A magnetic anisotropy sensor (MAS), which is previously applied to the stress or torque sensor, is also available for the detection of magnetic anisotropy of the materials to estimate their stress or defect noncontactly. However, since the MAS is a probe type sensor, it is affected by the external magnetic field, which is a serious problem for practical use. This paper discusses an effect of the external magnetic field to the MAS and proposes a method to reduce its influence.

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When a built-in resolver is incorporated into a motor shaft, there is sometimes a problem of an eccentricity error caused by mounting misalignment and tilting. This eccentricity error affects the sensing accuracy of the resolver and causes an angular error. A short-circuit winding applied in quadrature to the exciting winding helps to reduce the angular error due to the shaft eccentricity if the internal impedance of the short-circuit winding is optimally designed. This paper (1) analyzes the mechanism whereby the angular error leads to an error equation, (2) analyzes how the short-circuit winding reduces the magnetic flux in the quadrature axis, which acts to induce the angular error, and (3) clarifies the conditions for realizing a resolver error of under 10' at an eccentric rate (δ/g×100%) of under 50%.

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The magnetic anisotropy sensor (MAS) is able to measure the mechanical stress of ferromagnetic material non-contactly. This paper deals with the physical meaning of hysteresis phenomena in the MAS output voltage versus stress characteristics of the specimen (cold rolled steel). Experimental results disclosed the removal of the hysteresis between MAS output voltage and stress by the effect of AC demagnetizing field intensity, H_D, that is about sixty times as large as coercive force, H_c, of the specimen.

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The magnetic anisotropy sensor (MAS) is based on the phenomenon that steel materials, when brought under application of stress, change in their magnetic anisotropy. The MAS has a small, light probe and is capable of noncontact stress measurement. This paper deals with the experimental result of noncontact stress measurement of rail steel. The specimen was cut from a real 60 kg rail steel. Tensile and compressive stress were applied to the specimen using a fatigue testing machine. Good linearity was disclosed between MAS output voltage and stress of the rail steel over the range of tensile stress measurement 0 to +160 MPa with demagnetization.

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The mechanism of electromagnetic acoustic transducer (EMAT) for fundamental symmetrical Lamb wave using magnetostrictive effect in thin steel sheet was studied. The EMAT was constructed from the magnet for loading the parallel field to the sample surface and the meander coil for carrying the transmitting current. First the field dependence of the received signal amplitude and the phase for the transmitter and the receiver EMAT at the two different positions of the meander coil was investigated. Next the driving mechanism was discussed on the basis of the experimental results. This paper shows that this type of EMAT works using the time and spatial change of the synthesized magnetic field and has the different driving mechanism under the lead lines and between the lead lines of the meander coil.

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In recent years, linear oscillatory actuators (LOAs) employing mechanical resonance have been researched aiming at highly efficient actuators. This paper considers a cylindrical moving magnet type LOA having spring characteristics for resonant oscillation in the actuator itself An equation to express the thrust of the proposed LOA is derived using a permeance model, and calculation results by the permeance analysis and magnetic field analysis are compared with actual measured results. The thrust constants by the permeance analysis and magnetic field analysis agree with the measurement, and the permeance analysis with a short calculation time is effective in calculation of the thrust constant. The magnetic field analysis is effective in the calculation of the spring characteristics of static thrusts. In addition, the optimization of the size of the proposed LOA based on the motor constant is investigated A relational equation of the size of the LOA and the motor constant is derived. From calculation results on the motor constant using the permeance analysis and magnetic field analysis, the effectiveness of the permeance analysis with a short calculation time is confirmed. Moreover, by focusing on the motor constant below the same thrust constant, it is found that the coil resistance is effective as optimization indices identical to the motor constant.

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