International Journal of Applied Electromagnetics and Mechanics - Volume Pre-press, issue Pre-press

Authors: Li, Yiying | Fei, Zhangjun | Huang, Yanlan | Yang, Shiyou

Article Type: Research Article

Abstract: A metamaterial (MM) generally works on a resonance mode, and its permeability will vary sharply around this resonance frequency. Consequently, the performance of a MM will be largely degraded if it is designed using a traditional optimization technique without considering these inevitable imperfections in fabrications. In this regard, the robustness of a solution must be included in the design optimization of a MM, exacerbating additional computational burdens to the already costly design procedure arising from the application of a high-fidelity model. Consequently, it is demanding to reduce the function calls for a high-fidelity model in the robust design of a …MM. In this point of view, an optimization methodology by combining the genetic algorithm (GA) and a local search surrogate model is proposed for efficiently robust optimizations of a MM unit. Show more

Keywords: Genetic algorithm, metamaterial, robust optimization, surrogate model

DOI: 10.3233/JAE-220168

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. S1-S7, 2022

Authors: Guo, Yijun | Yusa, Noritaka | Hashizume, Hidetoshi

Article Type: Research Article

Abstract: This study explores the applicability of microwave nondestructive testing to detect a metal pipe’s inner crack. Three-dimensional finite element simulations were conducted to study the inspectability of cracks using microwaves in different modes and the dependency of the reflection characteristics of microwaves on crack size. The simulation results showed that microwaves in the TM01 and TE01 modes can detect circumferential and axial cracks, respectively. The positive relationship between crack size and intensity corresponding to the reflected microwaves was obtained in simulations and then verified by experiments. In both simulations and experiments, the axial crack length showed a small …influence on the results, especially for shallow crack detection. In the experiments, circumferential and axial cracks with a width of 0.3 mm were detected using microwaves. The experimental results revealed that signal amplitudes decreased when a slit penetrated a pipe wall, probably due to a microwave leakage. Show more

Keywords: Circumferential and axial cracks, microwave mode, crack size, pipe wall penetration

DOI: 10.3233/JAE-220127

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. S1-S9, 2022

Authors: Sasayama, Teruyoshi | Guo, Ziwei

Article Type: Research Article

Abstract: Rectangular wave eddy current testing (RECT), which is performed using a rectangular wave excitation current, can simultaneously obtain multiple datasets. However, the high-frequency harmonic signal detected by the detection coil interferes with the low-frequency signal based on Faraday’s law of induction. The method proposed in this study is a type of electronic bridge, wherein a compensation method is implemented to enhance the low-frequency signal of the RECT using a digital-to-analog converter (DAC). The compensation wave generated by the DAC is determined such that the output signal becomes zero when the probe does not detect any flaws. A 12 mm thick …aluminum plate with flat-bottom drill holes on the backside is used as the specimen. The holes have a diameter of 3 mm and depths of 2, 4, and 6 mm, respectively. The results demonstrate that the flaw signal cannot be detected without compensation. However, the flaw signal can be successfully detected around these holes with compensation. Show more

Keywords: Eddy current testing, low frequency, rectangular wave eddy current testing, digital-to-analog converter, electronic bridge

DOI: 10.3233/JAE-220106

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. S1-S8, 2022

Authors: Kitayama, Fumiya | Kondo, Ryou | Endo, Riku

Article Type: Research Article

Abstract: Lower limb exoskeletons with actuators aids disabled individuals in walking. However, the exoskeleton weight is greater than that of conventional medical devices such as orthoses and walking frames. In this study, we propose a novel strain wave gear for light exoskeletons, which is 50% lighter than conventional commercial strain wave gears. This gear uses magnets and yokes, rather than mechanical elements. The thin-walled elastic cylinder is deformed by the magnetic force in the gear, and the torque is transmitted by tooth engagements. The maximum torque was calculated to be 10.5 Nm using flexible multibody dynamics analyses with a magnetic force database. …The outcome was efficient in development of lightweight machines. Show more

Keywords: Strain wave gear, magnetic force, lower limb exoskeletons, electromagnetic analysis, multi body dynamics analysis

DOI: 10.3233/JAE-220213

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. S1-S10, 2022

Authors: Itagaki, Ryo | Kanai, Yasushi | Greaves, Simon

Article Type: Research Article

Abstract: Dual field generation layer (FGL) spin torque oscillators (STO) were investigated for use in microwave-assisted magnetic recording. The STOs were integrated into the gaps of write heads for stable oscillation. According to preliminary calculations, a FGL thickness of 5 nm was suitable, while the volume of 7.5 nm and 10 nm thick FGLs was too large and they did not oscillate stably. The most dominant factor influencing the FGL rotation was found to be the strength of the antiferromagnetic coupling between the FGLs. Other parameters were also varied, e.g., the exchange coupling between the negative spin injection layer (nSIL) and the trailing shield …(TS), however, no significant effect was found. Unlike single FGL STOs, the oscillation frequency changed drastically, from 38 GHz to 73 GHz, on varying the injected current density to the STO. Recording simulations showed that the signal-to-noise ratio was maximized for an STO oscillation frequencies between 34 GHz and 50 GHz, depending on the recording media used in the calculations. Therefore, the dual FGL STO may be suitable for a wide range of recording media. Alternatively, the dual FGL STO may be used for dual-layer recording, where different resonance frequencies are needed for each of the layers, obviating the need for a second STO. Show more

Keywords: Microwave-assisted magnetic recording (MAMR), spin torque oscillator (STO), write heads, micromagnetic simulation

DOI: 10.3233/JAE-220146

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. S1-S11, 2022

Authors: Ou, Raishin | Gotoh, Yuji

Article Type: Research Article

Abstract: The large-diameter steel pipes are often used in petrochemical plants. In this large-diameter steel pipe, there are many cases where corrosion in the steel pipe is inspected from the outside of the steel pipe. In particular, there is a demand for a method for detecting defects inside or outside the steel pipe from the outer side of the steel pipe at high speed. Therefore, the electromagnetic inspection method is useful for detecting these defects. In the electromagnetic inspection method, using both static (DC) magnetic field and alternating (AC) magnetic field is proposed for inspecting inner side defects as well as …outside defects. On the other hand, the Fourier series expansion of the full-wave rectified wave of the stationary AC magnetic field shows that it is a composite of the DC component and the AC component due to the cosine wave. Therefore, in this research, an inspection method using full-wave rectified AC magnetic field is proposed for inspecting inner side defects as well as surface defects. In this paper, the usefulness of the proposed method is demonstrated by electromagnetic field analysis using the “play model” that takes into account minor loop magnetic properties. In addition, a verification experiment is also carried out. Show more

Keywords: Full-wave rectified AC magnetic field, magnetic flux leakage, opposite side defect, electromagnetic nondestructive testing, 3-D nonlinear FEM taking account of minor loop curve, play hysterons model method

DOI: 10.3233/JAE-220205

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. S1-S10, 2022

Authors: Rao, Shaowei | Yang, Shiyou | Zou, Guoping

Article Type: Research Article

Abstract: A methodology to diagnose transformer faults based on dissolved gas analysis (DGA) is proposed. Since a fault is more sensitive to the ratios of gas contents, a general ratio feature extraction framework is proposed to generate a feature subset as the input of the diagnosis model. The feature subset is evaluated by the improved case-based reasoning (CBR) and optimized by using a proposed new algorithm called the k -optimal algorithm (k -OA). The comparison results between the k -OA and the genetic algorithm (GA) show that the k -OA is more efficient in solving such a combinatorial optimization problem. The …obtained optimal feature subset is used to diagnose a public transformer fault dataset, and a 92.6% diagnosis accuracy is observed as compared to that of only 85.1% diagnosis accuracy by using the original features. Show more

Keywords: Case-based reasoning, combinatorial optimization, fault diagnosis, feature extraction, transformer

DOI: 10.3233/JAE-220169

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. S1-S8, 2022

Authors: Takeuchi, Yuka | Hamasaki, Atom | Kawaguchi, Hideki | Matsuda, Mizushi

Article Type: Research Article

Abstract: Cellulose is a promising sustainable material due to its flexibility and high strength. The light scattering characteristics of anisotropic cellulose crystals from various angles with magnetic orientation were experimentally clarified in this study. The intensity of the light scattered from cellulose crystals is reduced by the application of a magnetic field. Therefore, it was suggested that switching the magnetic field would allow the light intensity to be controlled similarly to an attenuator.

Keywords: Magnetic orientation, light scattering, cellulose crystal, diamagnetic material

DOI: 10.3233/JAE-220172

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. S1-S7, 2022

Authors: Bergqvist, Anders

Article Type: Research Article

Abstract: A magnetic vector hysteresis model is presented using play hysterons as building blocks. The main difference compared to earlier play based magnetic hysteresis models is that instead of forming a superposition of plays with different coercivities, this work uses a set of identical plays which are connected in a chain so that the output of one play acts as input to the next. Like models using a superposition, this yields far more complex minor loop behavior than a single play is capable of. Comparisons are made with measurements on a nonoriented electric steel for BH curves and alternating and rotational …losses, showing satisfactory agreement. The approach is found to have both advantages and disadvantages compared to models using superpositions of plays. The problem of determining model parameters becomes simpler and the model can be reversed so either magnetic field or magnetization may be used as known variable. On the other hand, there is no apparent connection to underlying physical processes. Show more

Keywords: Magnetic hysteresis, vector hysteresis, electrical steel

DOI: 10.3233/JAE-220173

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. S1-S4, 2022

Authors: Mochizuki, Yuki | Gotoh, Yuji

Article Type: Research Article

Abstract: Nickel plating is used on the surface of rolling rolls in paper mills, and it is important to monitor the thickness of the nickel plating. In this research, the electromagnetic inspection method for the thickness of the nickel plating using the difference in electromagnetic properties between the nickel and the base material of S25C steel is proposed. On the other hand, the detection signal is also affected by the changing distance (lift-off: L o ) between the proposed electromagnetic sensor and the nickel plating. In this paper, by measuring the magnetic field in two directions of the electromagnetic sensor, …it is shown that both the thickness of the nickel plating and the lift-off (L o ) are evaluated. Show more

Keywords: Nickel plating, thickness evaluation, lift-off, electromagnetic field analysis

DOI: 10.3233/JAE-220202

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. S1-S7, 2022