International Journal of Applied Electromagnetics and Mechanics - Volume 52, issue 3-4

Authors: Yang, Yun | Li, Long | Feng, Bo | Kang, Yihua

Article Type: Research Article

Abstract: The micro-crack is always difficult to discover in the widely applied magnetic flux leakage (MFL) inspection because of the weak leakage magnetic field. Hence, a novel method for enhancing the micro-crack signal based on the magnetic particle adsorption is proposed. The mechanism of magnetic field distribution in the vicinity of the micro-crack based on the new method is analyzed from the angle of magnetic refraction. The confirmation for the signal enhancement and further discussion are presented with the finite element simulation. Simulation results indicate that the signal of the micro-crack is significantly enhanced based on the magnetic particle adsorption which …confirms the feasibility of the novel method. In addition, the ability of the signal enhancement is more relevant to the maximum height than the maximum width of the magnetic particle indication, and the signal increases when the relative permeability of the gathered magnetic particles is bigger. Show more

Keywords: Magnetic flux leakage (MFL) inspection, magnetic particle testing (MT), micro-crack, signal enhancement

DOI: 10.3233/JAE-162165

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 1107-1113, 2016

Authors: Jiang, Jinhui | Li, Hongqiu | Zhang, Fang | Han, Ming

Article Type: Research Article

Abstract: The identification (or reconstruction) of dynamic load is the second kind of the inverse problem in structural dynamic analysis, which is a process of reconstructing load applied to structure in case of structural dynamic model and information of structural response. When it is difficult to measure the load applied to the structure with acquisition equipment, the identification technology of dynamic load makes it possible for obtaining external load, so its researches have an important theoretical value and practical prospects. The elastic thin plate is the common load-carrying structures in engineering, and the identification of dynamic load on the plate is …very meaningful. The paper presents a new method called method of moment for identification of distributed dynamic load on the plate structure. At first, the two-dimension orthogonal polynomial is constructed, which is employed as base functions for Generalization Fourier Expansion, and then the infinite dimensions function is transformed into finite dimension parameters. Secondly, the relationships are built between the finite dimension parameters and the structural response. Thirdly, the parameters can be obtained by the inverse algorithm or optimization algorithm. At last, the distributed dynamic load can be reconstructed by the finite dimension parameters. The results of computation simulations and experiment show the method is correct theoretically, effective and feasible in engineering practice. Show more

Keywords: Dynamic distributed load, identification, method of moment

DOI: 10.3233/JAE-162221

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 1115-1122, 2016

Authors: Zhao, Minghua | Yuan, Yongqin | Shi, Zhenghao | Zhao, Jinwei | Wang, Yinghui

Article Type: Research Article

Abstract: A novel approach to the construction of motion graphs based on a new similarity measurement method is proposed in this paper. The main contributions of this paper are: i) to improve the accuracy of motion similarity computing, a new similarity measurement method is presented which combines frame distance based on dynamic time warping (DTW) with uniform warping window and motion distance based on motion features; ii)to avoid illogical jump of standard motion graph, a new automatic construction strategy of motion graphs based on similarity of motion clips is proposed, transition points of which are matched based on the path with …the minimum cost and motions are synthesized based on motion transition points. Experimental results based on the CMU MoCap human motion database show that the proposed method can confirm the logical correctness and naturalness in the junction of two human locomotion sequences and its efficiency is two or three times faster than the standard motion graph. Show more

Keywords: Computer animation, motion graph, motion synthesis, interpolation, motion capture

DOI: 10.3233/JAE-162130

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 1123-1131, 2016

Authors: Li, Hongmei | Chen, Zhenmao | Zhang, Dongli | Sun, Hongxia

Article Type: Research Article

Abstract: The equivalent magnetic-dipole model is widely used in magnetic flux leakage testing by assuming that some nonzero surface magnetic charges are concentrated in the walls of the breaking flaw, thus the distribution of the magnetic charges in testing structure conceives information about the edge of flaw, which can be utilized to evaluate the size of the breaking flaw by reconstructing the magnetic charges distribution in structures with measured magnetic flux leakage signals. However, the magnetic flux leakage signals above testing structure are usually influenced not only by the magnetic charges concentrating in the flaw walls, but also by which locating …in the continuum below the flaw, and the magnetic charges distribution in the continuum layer is totally different from that of flaw layer, which reduces the estimation precision of flaw size. To strip away the magnetic charge influences in continuum layer and achieve high degree of accuracy in reconstructing the magnetic charge distribution around a flaw, increase the estimation precision of flaw size in magnetic flux leakage testing, a two-layer algorithm is proposed in this paper. In this algorithm, a structure with a flaw is divided into two layers according to the difference of the magnetic charge distribution, the layer 1 contains flaw and the layer 2 is the continuum of base materials, the magnetic flux leakage densities above the upper and lower surface of structure are measured. A scheme based on a new initial value regularization method and steepest descent method is proposed to reconstruct the magnetic charges distributing in flaw layer with the measured magnetic flux leakage signals. The simulation result shows that it can reconstruct the magnetic charges in flaw layers precisely; the experimental results show that it can improve the estimation precision of flaw in magnetic flux leakage testing clearly. Show more

Keywords: Two-layer reconstruction algorithm, flaw evaluation, magnetic charge distribution

DOI: 10.3233/JAE-162148

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 1133-1139, 2016

Authors: Ahn, Hyun-Mo | Kim, Seong-Yun | Kim, Joong-Kyoung | Oh, Yeon-Ho | Hahn, Sung-Chin

Article Type: Research Article

Abstract: A power transformer has complex geometry comparing with other electric machines. So it needs a lot of computing time when we deal with the transient problem such as short-circuit characteristics of a power transformer. In this paper, we proposed an efficient numerical technique to compute transient electromagnetic force of a power transformer during three-phase short-circuit condition. In order to analyze the transient electromagnetic force acting on every disk of transformer windings, we made a simplified axi-symmetric model. First, the transient short-circuit current is calculated by using a short-circuit equation. Next, the transient short-circuit electromagnetic force due to the short-circuit current …is computed by finite element method with a simplified axi-symmetric model. The proposed numerical technique is expected to be useful in the short-circuit duty design and structure design of the power transformers. Show more

Keywords: Numerical modeling, short-circuit electromagnetic force, short-circuit characteristic, power transformer

DOI: 10.3233/JAE-162093

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 1141-1149, 2016

Authors: An, Siguang | Yang, Shiyou | Bai, Yanan | Wu, Xiushan

Article Type: Research Article

Abstract: Multi-objective design is very common in electrical engineering, and the development of new multi-objective optimizers becomes recently a topical issue in computational electromagnetics because of the unavailability of a universal multi-objective optimizer. In this regard, an improved physical programming (PP) method is presented to solve multi-objective electromagnetic inverse problems. The improvements include: (1) the multi-pseudo preference concept is introduced to overcome the deficiency of existing PP method in finding only one Pareto solution in a simulation and enhance the usage rate of sampling points; (2) a novel dynamically guiding mechanism is proposed to improve the computational efficiency and to provide …the evolutionary direction; (3) some new rules for algorithm parameter updating are proposed to realize the two ultimate goals of an idea multi-objective optimizer of finding as many as possible Pareto optimal solutions and having them uniformly distributed on the Pareto Front. The results of typical mathematic test functions and a practical optimization design demonstrate the validity and advantages of the proposed method. Show more

Keywords: Physical programming method, multi-objective optimization, inverse problem, Pareto optimization

DOI: 10.3233/JAE-162123

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 1151-1159, 2016

Authors: Kitayama, Fumiya | Hirata, Katsuhiro | Yamada, Tatsuro

Article Type: Research Article

Abstract: Active vibration control engine mounts are installed in automobiles to reduce vibration and improve ride quality. Previous control methods could be only applied when the phase difference is between -π/2 and π/2. In this paper, a new method that can be used at any phase difference, and that uses step delays so that pre-modelling of the device becomes unnecessary, is proposed. The effectiveness of the method is demonstrated through experimental results.

Keywords: Active vibration control engine mounts, least means square adaptive control, phase compensation

DOI: 10.3233/JAE-162100

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 1161-1168, 2016

Authors: Oka, Mohachiro | Sato, Yuki | Yakushiji, Terutoshi | Enokizono, Masato

Article Type: Research Article

Abstract: It is well-known that the fatigue process is different depending on various kinds of applied stresses. To prevent accidents caused by material degradation such as fatigue, it is important to know the difference between causes of the fatigue process, such as pulsating tension stress as opposed to plane bending stress. The relationship between fatigue damage and remnant magnetization has been extensively researched using a thin-film flux-gate (FG) magnetic sensor for semi-stable austenitic stainless steel (SUS304 or ANSI304). Therefore, in this paper, the difference between the fatigue processes by pulsating tension fatigue and plane bending fatigue was investigated using the remnant …magnetization method with a specimen made of SUS304. The remnant magnetization method with the FG magnetic sensor was non-destructively able to clarify the difference between the fatigue processes of SUS304 and the applied stress. Show more

Keywords: Remnant magnetization, SUS304, fatigue, pulsating tension stress, plane bending stress

DOI: 10.3233/JAE-162098

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 1169-1176, 2016

Authors: Fukuoka, Katsuhiro

Article Type: Research Article

Abstract: Nonuniform permeability distribution in ferromagnetic materials creates noise in eddy current testing (ECT). To overcome this problem, ferromagnetic materials are magnetized and inspected in the magnetic saturation state to reduce noise. In this study, I targeted a spring steel material that is not easily magnetized and developed an ECT system with an encircling coil probe that was able to detect microcracks. Clear signals for 70 μm deep microcracks were obtained with a signal-to-noise ratio of 3.5 by magnetizing a test object using the optimal exciting current.

Keywords: Eddy current testing (ECT), encircling coil probe, spring steel, magnetic noise, magnetization

DOI: 10.3233/JAE-162108

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 1177-1183, 2016

Authors: Yamaguchi, Toshihiko | Mihalache, Ovidiu | Ueda, Masashi

Article Type: Research Article

Abstract: The paper presents application of a multi-coil eddy current testing (ECT) system to detect defects in steam generator (SG) tubes of Fast Breeder Reactors (FBRs). The defects are located near SG tube support plates. The SG tubes were immersed in liquid sodium at temperature above 500°C and then drain several times. Three dimensional (3D) Finite Element Method (FEM) numerical simulations, using an in-house developed code, are validated with experimental measurements in both cases of absence or presence of sodium on the outer SG tubes surfaces. Validations of FEM simulations of multi-coil ECT system with experimental measurements, for helical tubes, …are conducted for a large model of SG tubes support plate and three SG tubes attached to it. Show more

Keywords: SG tubes, RF-ECT, multi-coil sensor, support plate, sodium

DOI: 10.3233/JAE-162225

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 1185-1191, 2016