International Journal of Applied Electromagnetics and Mechanics - Volume 64, issue 1-4

Authors: Rahman, Arifur | Mizuno, Takeshi | Ishino, Yuji | Takasaki, Masaya | Yamaguchi, Daisuke

Article Type: Research Article

Abstract: A newly developed AC magnetic suspension system is designed and fabricated to investigate the performances. A new concept of design is revealed for operating the apparatus differentially where the floator is kept at a constant position despite changing the parameters of the upper stator electromagnets. An extensive finite element analysis is conducted to estimate the basic characteristics of the system. A permanent magnet is incorporated in this system to reduce the required supply energy to the stator electromagnets. Magnetic suspension with a maximum gap of 2.0 mm without any control with the upper electromagnet in cumulative coupling mode and with …a gap of 3.0 mm with indirect damping in the differentially operated mode is achieved. The indirect damping is achieved by applying PD control to the stator. The individual force, current and phase for variable frequency and gap between primary and secondary electromagnet are measured to examine the basic characteristics and performances. Show more

Keywords: Magnetic suspension, magnetic resonance coupling, self-stabilization, magnetic force, indirect damping

DOI: 10.3233/JAE-209390

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 64, no. 1-4, pp. 779-787, 2020

Authors: Bai, Yinghao | Zhang, Na | Peng, Lei | Li, Xiaoguang | Kong, Yuying | Tao, Yu | Ye, Chaofeng

Article Type: Research Article

Abstract: Eddy current testing (ECT) is commonly used in steam generator tube inspection. Among multiple probes applied in this area, array probe shows the merit of the capability of obtaining a C-scan image in a simple linear scan. In this work, a novel array ECT probe with three-phase excitation is proposed. The probe consists of two rows of excitation coils and a row of pickup coils. The induced eddy current shifts electrically in the testing sample so that the necessity of multiplexer is eliminated, resulting in advantages of lower cost, less noise and faster inspection speed. Theoretical analysis indicates that the …background signal of the array sensor would be small. A 3D finite element method (FEM) model is developed to study the operating principle and to predict the inspection performance of the probe. A prototype probe has been developed and tested, by which a steam generator tube sample with different kinds of defects was inspected. The experiment results validate the simulation model and further demonstrate the feasibility of the sensor. Show more

Keywords: Steam generator tube inspection, eddy current testing, array probe, three-phase excitation

DOI: 10.3233/JAE-209391

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 64, no. 1-4, pp. 789-797, 2020

Authors: Ido, Yasushi | Iwamoto, Yuhiro | Inden, Takuya

Article Type: Research Article

Abstract: The thermal conductivity of a magnetic fluid is expected to enhance by adding micron-sized particles with high thermal conductivity. The thermal conductivity of the magnetic fluid containing micron-sized graphite particles was investigated experimentally. The shapes of the graphite particles were sphere and flake-like. As the results of visualization experiments using the dark field microscope, the spherical graphite particles form chain-like clusters under applied magnetic field, while the fibrous structure is formed by the flake-like graphite particles, however, chain-like cluster formation cannot be clearly observed. The experiments using the transient hot-wire method showed that the thermal conductivity of magnetic fluid containing …graphite particles is enhanced by applying magnetic field and by increasing the volume fraction of graphite particles. Show more

Keywords: Magnetic fluid, cluster, graphite particle, thermal conductivity, dark field microscopy

DOI: 10.3233/JAE-209392

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 64, no. 1-4, pp. 799-805, 2020

Authors: Zhang, Zijian | Shang, Kai | Du, Yunpeng | Zhou, Ji | Dong, Yangyang

Article Type: Research Article

Abstract: It is of great significance to accurately calculate the mutual inductance of one-primary multiple-secondary coil system (OPMSC) in order to improve energy transmission efficiency, measurement accuracy of magnetic sensor, etc. In this paper, a method based on time harmonic field to calculate such mutual inductance is proposed. Both the high frequency alternating current model and the time-harmonic electromagnetic field calculation method are used to ensure engineering practicability of the method. The current of each coil and the relative position between coils are considered in the proposed method. Moreover, according to the full derivation of a new analytical method. the extremum …phenomenon of mutual inductance is described. And this method is verified by both finite element simulations and experiments, which proves that the method is effective for optimizing the relative position of the multiple coils when mutual influence among all the coils is taken into account. Show more

Keywords: Electromagnetic analysis, mutual inductance, multi-coil system

DOI: 10.3233/JAE-209393

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 64, no. 1-4, pp. 807-816, 2020

Authors: Zhou, Xinwu | Urayama, Ryoichi | Uchimoto, Tetsuya | Takagi, Toshiyuki

Article Type: Research Article

Abstract: Eddy current testing is widely used for the automatic detection of defects in conductive materials. However, this method is strongly affected by probe scanning conditions and requires signal analysis to be carried out by experienced inspectors. In this study, back-propagation neural networks were used to predict the depth and length of unknown slits by analyzing eddy current signals in the presence of noise caused by probe lift-off and tilting. The constructed neural networks were shown to predict the depth and length of defects with relative errors of 4.6% and 6.2%, respectively.

Keywords: Eddy current testing, artificial intelligence, back-propagation neural network

DOI: 10.3233/JAE-209394

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 64, no. 1-4, pp. 817-825, 2020

Authors: Ueno, Satoshi | Tomoda, Masaya | Jiang, Changan

Article Type: Research Article

Abstract: This paper introduces an axial-flux self-bearing motor (ASBM) using two permanent magnet attractive type passive magnetic bearings (PMBs). The ASBM provides both functions of a disc motor and thrust magnetic bearing, and controls motor torque and axial force by single rotational magnetic flux. The PMB consists of a cylindrical permanent magnet and an iron shaft with conical edge, and it supports the rotor in radial directions. This motor has a simple structure and control system, and it is possible to reduce the size and cost. In this paper, the structure and control method are introduced, and the results of levitation …and rotation tests whose non-contact rotation speed was achieved up to 1,500 rpm are shown. Show more

Keywords: Magnetic bearing, axial-flux self-bearing motor, passive magnetic bearing

DOI: 10.3233/JAE-209395

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 64, no. 1-4, pp. 827-833, 2020

Authors: Li, Weibin | Jiang, Chang | Lan, Zifeng | Deng, Mingxi

Article Type: Research Article

Abstract: Nickel and nickel-based composites are of vital importance in many fields, while temperature loading can greatly influence the strength and performance of the materials. Nondestructive evaluation and characterization of such thermal damage can be used to predict the failure of metallic structures, thermal barrier coatings and so on, especially in a non-contact way under certain strict circumstances, such as testing at high temperature or in radiative environment. Herein, a contactless ultrasonic technique employing electromagnetic acoustic transducers (EMATs) combined with the resonance ultrasound spectroscopy is applied to make up the low energy transition efficiency of EMATs and enhance the signal-to-noise ratio …of ultrasonic testing signals. The method is adopted to assess the thermal damages of different levels in artificially heat loaded nickel plates. The damage sensitivity of third order harmonics generated from shear waves is discussed, along with linear ultrasonic features including wave velocity and attenuation. Experimental results show that the proposed nonlinear electromagnetic acoustic resonance (EMAR) technique can be used to evaluate the thermal damage in ferromagnetic material with improved reliability and sensitivity over linear ones. Show more

Keywords: Contactless, higher harmonic generation, electromagnetic acoustic resonance, thermal loading

DOI: 10.3233/JAE-209396

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 64, no. 1-4, pp. 835-842, 2020

Authors: Sasaki, Ryunosuke | Koizumi, Kohei | Kiryu, Shogo

Article Type: Research Article

Abstract: In this study, a magnetic resonance wireless power transmission system with a sown auxiliary coil is described. The system is proposed to deliver power to an “implantable cardioverter defibrillator” (ICD) device from a bed. The auxiliary coil is supposed to be sown in a shirt. With the coil, the poor coupling coefficient and the effective quality factor can be improved. In this study, the power efficiency was investigated on a magnetic resonance wireless power transmission system with a sown auxiliary coil by using a 1/2 scaled model. As a result, when transfer distance was 100 mm (200 mm in the full scaled …model) and lord resistance was 20 Ω, the maximum transfer efficiency with an auxiliary coil was measured to be about 70% much higher than without that. Show more

Keywords: Wireless power transmission, sown coil, magnetic resonance

DOI: 10.3233/JAE-209397

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 64, no. 1-4, pp. 843-851, 2020

Authors: Zhou, Jiaming | Dong, Longlei | Yan, Jian | Guan, Wei

Article Type: Research Article

Abstract: The optimization design of complex nonlinear structures mainly relies on expert experiences and trial and error. In this paper, we proposed an optimization design framework for nonlinear structures by combining experimental data and machine learning. The framework can search the entire design space and guide the next experiment by machine learning model until the optimization targets are met. To demonstrate the effectiveness and practicability of this framework, we have optimized the damping efficiency and principal resonance frequency (PRF) of an Electricity Distribution System (EDS) with eight rubber isolators. The results show that the design targets of the optimized structure are …consistent with the experimental results after two iterations. This framework is able to guide and accelerate nonlinear structure design and has significant value for engineering applications. Show more

Keywords: Optimization design, machine learning, nonlinear structure, vibration isolation

DOI: 10.3233/JAE-209398

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 64, no. 1-4, pp. 853-859, 2020

Authors: Sakurai, Sho | Nakamura, Kenji

Article Type: Research Article

Abstract: Many communication servers are being installed in order to develop information technology (IT). The servers require not only high-performance processer but also its cooling system. Among the cooling systems, a cooling fan is the most suitable due to good balance between performance and cost. In order to further improve the fan’s performance, both torque and speed of cooling fan motors are increased. However, iron loss and eddy current loss are also increased along with larger torque and higher speed, which worsens the efficiency. This paper investigates the optimum rotor structure for the fan motor in order to obtain sinusoidal flux …distribution in air gap, which can reduce the iron and eddy current losses. Show more

Keywords: IPM motor, cooling fan, Halbach array

DOI: 10.3233/JAE-209399

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 64, no. 1-4, pp. 861-868, 2020