Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Mihalache, O.; 山本 郁夫*
International Journal of Applied Electromagnetics and Mechanics, 78(1-3), p.141 - 146, 2025/07
被引用回数：0 パーセンタイル：0.00(Engineering, Electrical & Electronic)The paper reports the progress to obtain accurate simulations of amplitude of EMAT signal from defects in metallic plates by means of FEM simulations. The simulations results are applied to a FEM model based on a two-dimensional coupled eddy-current (ECT) and ultrasound (UT) formulation, by using various numerical integration methods as Crank-Nicolson, Backward Euler and Newmark-beta method. The paper presents the methodology to acquire convergence of the large variation in the EMAT signal from a defect to the same final EMAT signal, not only in the defect amplitude but also in the shape of the time transient EMAT signal when using different methods. Accurate EMAT signals can be obtained by means of the combination of high order finite elements (FEM) and advanced numerical time integration, to reach the converged EMAT signal in the shortest time, opening the way to simulate accurate signals form faraway defects.
山口 智彦; Mihalache, O.
Nuclear Engineering and Design, 401, p.112084_1 - 112084_14, 2023/01
被引用回数：6 パーセンタイル：62.05(Nuclear Science & Technology)This paper investigated a new method based on a combination of electromagnetic and ultrasonic sensors for inspecting the core support structure of the reactor vessel in sodium-cooled fast reactors from a position located outside of the vessel. Using an electromagnetic acoustic transducer (EMAT) sensor with a Halbach magnet, the feasibility of the detection of the defects in the reactor core support structure was investigated via experimental measurements using a reduced half-scale mock-up model in a sodium-free environment. The amplitude of the signal from various small slits was enhanced using a combination of EMAT sensor geometry, Halbach magnet configuration, and signal processing methodology in view of increasing the signal-to-noise ratio when the EMAT continuously scanned the area of interest for defects deep inside the metallic structure.
山口 智彦; Mihalache, O.
International Journal of Applied Electromagnetics and Mechanics, 64(1-4), p.895 - 903, 2020/09
被引用回数：0 パーセンタイル：0.00(Engineering, Electrical & Electronic)Using an EMAT based on a Halbach magnet system it is reported smaller defect detection in thick metallic plates. The visualization of the EMAT signal using a novel C-scan procedure, based on a continuous moving of transducer and off-line signal processing, is enhanced and optimized for detection of small defects on the opposite side of thick metallic plates (50 mm). The feasibility and performance of the method, validated through experimental tests, showed an optimized two-dimensional (2D) visualization technique for EMAT signal, which can be used for surface scans of thick metallic plates with higher inspections speed.
Mihalache, O.; 山口 智彦
International Journal of Applied Electromagnetics and Mechanics, 64(1-4), p.905 - 912, 2020/09
被引用回数：0 パーセンタイル：0.00(Engineering, Electrical & Electronic)The paper presents a fast and accurate algorithm reconstruction of the magnetization model of a Halbach magnet array used in an EMAT transducer. The model error accuracy is validated against experimental measurements of magnetic field distributions through use of both theoretical formulas and 2D/3D FEM simulations based on the non-uniform distribution of reconstructed magnetization model.
山口 智彦; Mihalache, O.
非破壊検査, 68(11), p.527 - 534, 2019/11
高速炉の蒸気発生器伝熱管検査に適用できる高感度の内挿型センサ技術の研究開発成果として、小径厚肉の強磁性管に生じる微小欠陥の検出を目的にマルチコイル型渦電流探傷センサを開発した。当該センサの特徴は、渦電流の直接磁場と間接磁場を同時に利用できる点や従来検出が困難とされる疲労き裂欠陥の検出が可能としたことである。さらに、直接磁場と間接磁場を同時に利用するハイブリッド型ECTでは効率的な検査が可能となり、検査のニーズに合わせることができる。
Mihalache, O.; 山口 智彦; 白濱 卓馬; 上田 雅司
International Journal of Applied Electromagnetics and Mechanics, 59(3), p.1161 - 1168, 2019/03
被引用回数：6 パーセンタイル：31.26(Engineering, Electrical & Electronic)The paper presents applications of window multi-frequency algorithms using eddy currents to the in-service inspection of fast breeder reactor (FBR) steam generator (SG) tubes in the presence or absence of sodium. Detection of defects filled with sodium in various percentages are investigated based on three dimensional (3D) finite element (FEM) simulations, using an in-house developed code, of remote field eddy current (RFEC) multi-coil sensors system. Various sources of noises (sodium percentage, sensors lift-off and speed and others) and their impact on the algorithms accuracy is compared with the application to previous measured data of SG tubes in mock-up tanks before and after several sodium draining.
山口 智彦; Mihalache, O.; 上田 雅司
International Journal of Applied Electromagnetics and Mechanics, 59(4), p.1469 - 1477, 2019/03
被引用回数：8 パーセンタイル：35.53(Engineering, Electrical & Electronic)The paper presents the progress in the developments of an electro-magnetic acoustic transducer (EMAT) based on a Halbach magnet system optimized for detection of defects in thick plates with application to the inspection of fast breeder reactors (FBR) vessel. The defects are located far or near weld lines in small austenitic stainless steel plates or in large thick (50 mm) plates mounted in a FBR vessel mock-up. Performance of single or double units EMAT are investigated and optimised for working in industrial conditions and with cables long up to 45 m. Experimental measurements focussed on increased signal/noise ratio for detection signal from defects near or far from welds of reactor vessel.
山口 智彦; Mihalache, O.
Journal of Nuclear Science and Technology, 54(11), p.1201 - 1214, 2017/11
被引用回数：0 パーセンタイル：0.00(Nuclear Science & Technology)A new design has been adopted for the steam generators (SG) tubes of the Japan Sodium-cooled Fast Reactor (JSFR) using double-wall tubes. This paper estimates and assesses the effectiveness of detecting defects in SG double-wall tubes of the JSFR by using combined high-frequency eddy current testing (ECT) and low-frequency remote field eddy current (RF-ECT) sensors. We confirm that the proposed hybrid ECT sensor is highly sensitive to small defects, fatigue cracks, and other defects even when located under support plates of tubes. The parameters of the hybrid ECT sensor are designed and optimized to detect small defects using accurate numerical simulations based on the finite element method (FEM), using an in-house developed code. The sensitivity and high performance of the hybrid ECT sensor was validated with experimental measurements.
Mihalache, O.; 山口 智彦; 白濱 卓馬; 上田 雅司
E-Journal of Advanced Maintenance (Internet), 9(2), p.60 - 65, 2017/08
The adherence of sodium on the external surface of steam generator tubes (SGs) of Fast Breeder Reactors (FBR) adds an additional level of complexity in the in-service inspection (ISI) of SGs using eddy current testing (ECT). The paper focusses on research and development (R&D) of novel multi-frequency (MF) algorithms, based on ECT signals, special developed and tuned to enhance the signal from defects located on external SG tube surface and to suppress electromagnetic noise from the conductive sodium and SG support plates. The application of the MF algorithm is investigated using both three-dimensional finite element (FEM) simulations and experimental measurements from SG tubes soaked and then drained of sodium, in a sodium tank mock-up.
Mihalache, O.; 山口 智彦; 白濱 卓馬; 上田 雅司
Proceedings of 3rd International Conference on Maintenance Science and Technology (ICMST 2016) (Internet), 2 Pages, 2016/11
The adherence of sodium on the external surface of steam generator tubes of Fast Breeder Reactors (FBR) adds an additional level of complexity in the in-service inspection (ISI) of SGs using eddy current testing (ECT). The paper focusses on research and development of novel multi-frequency algorithms, based on ECT, special developed and tuned to enhance the signal from defects located on external SG tube surface and to suppress electromagnetic noise from the conductive sodium and SG support plates. The application of the method is investigated using both three-dimensional finite element (FEM) simulations and experimental measurements from SG tubes soaked and then drained of sodium, in a sodium tank mock-up.
Mihalache, O.; 山口 智彦; 白濱 卓馬*; 上田 雅司
International Journal of Applied Electromagnetics and Mechanics, 52(1-2), p.659 - 666, 2016/09
被引用回数：3 パーセンタイル：19.07(Engineering, Electrical & Electronic)The paper presents application of novel multi-frequency eddy currents algorithms to helical steam generator tube of FBR to improve defect detection even when sodium partially fills the volume of the defect. The task is accomplished using three dimensional (3D) finite element (FE) numerical simulations that can take into account full circumferential and partial outer tube defects located near a tube support plate.
Mihalache, O.; 山口 智彦; 上田 雅司
Electromagnetic Nondestructive Evaluation (XVII), p.109 - 119, 2014/00
被引用回数：3 パーセンタイル：83.63(Engineering, Electrical & Electronic)The present paper focuses on multi-frequency ECT algorithms applied specifically to the magnetic SG tubes of Monju FBR. The algorithms optimum parameters for either two and three frequencies are determined using 2D and 3D numerical Finite Element Simulations (FEM) based on codes previously developed in-house by authors.
山口 智彦; Mihalache, O.; 上田 雅司
Electromagnetic Nondestructive Evaluation (XVII), p.144 - 154, 2014/00
被引用回数：3 パーセンタイル：83.63(Engineering, Electrical & Electronic)強磁性体の蒸気発生器伝熱管の外表面に導電性物質であるナトリウムが付着すると渦電流探傷試験において欠陥の検出性能に影響を与えることから、著者らはナトリウム浸漬試験と電磁場解析を行い、伝熱管や構造物支持板や溶接部にナトリウムが付着した場合の試験結果を確認したので、本会議にて発表する。
Garcia Rodriguez, D.; Mihalache, O.; 上田 雅司
Proceedings of 16th International Symposium on Applied Electromagnetics and Mechanics (ISEM 2013), p.219 - 220, 2013/07
This work presents the development of a new approach to EMAT finite element method (FEM) simulations by using a coupled electromagnetic-mechanical equation system. Validation is performed within the limits of the un-coupled equations using commercially available FEM codes. The advantages and drawbacks of the new method versus the traditional un-coupled approach are evaluated for various EMAT time-transient patterns. Numerical FEM analyses using either a sparse direct solver or an iterative one are investigated with both implicit and explicit time integration methods.
Mihalache, O.; 山口 智彦; 上田 雅司
Abstracts of Electromagnetic Nondestructive Evaluation Series, p.42 - 43, 2012/07
The present paper focuses on electromagnetic simulations of ECT for helical SG tubes and large SP models. Large scale 3D simulations are validated by comparison with experimental measurements conducted in a mock-up test in our laboratory. State of the art parallel numerical simulations using an electromagnetic code developed with a hybrid OpenMP-MPI approach for very large FEM models are conducted using up to 1024 CPUs in Fujitsu BX900 supercomputer. The availability of large models offers new insights into ECT for large structures in FBR, where electromagnetic interference can appear due to close proximity of multiple tubes.
西村 昭彦; 菖蒲 敬久; 岡 潔; 山口 智彦; 島田 幸洋; Mihalache, O.; 田川 明広; 山下 卓哉
レーザ加工学会誌, 17(4), p.207 - 212, 2010/10
高速増殖炉の熱交換器伝熱管に発生する微小亀裂を検査し補修するため、複合型光ファイバスコープを用いたプローブ試作機を開発した。本プローブはレーザー加工ヘッドと渦電流探傷装置も構成品に加えられている。超短パルスレーザー蒸発は、材料表層の加工硬化層の除去に用いることができる。加えて、スポットレーザー溶接が微小亀裂の補修に用いられた。このプローブシステムは、熱交換器の寿命を延ばすことにより、安全かつ経済的な選択肢を高速増殖炉の保守保全に与えることができる。
Mihalache, O.; 山口 智彦; 上田 雅司; 宮原 信哉
International Journal of Applied Electromagnetics and Mechanics, 33(3-4), 6 Pages, 2010/00
被引用回数：12 パーセンタイル：54.31(Engineering, Electrical & Electronic)高速増殖原型炉「もんじゅ」の蒸気発生器伝熱管は、140本の伝熱管がヘリカル形状に密接に配置され、蒸気発生器の中に格納されている。伝熱管の検査には、渦電流探傷試験(ECT)を適用する。このように伝熱管が密集した環境では、渦電流が隣の管にも流れることから検出感度に影響を与えることが懸念される。著者らは、複数の伝熱管が存在した場合や伝熱管サポート部での影響について3次元の電磁場解析で定量的に明らかにした。
西村 昭彦; 岡 潔; 山口 智彦; 赤津 朋宏*; 関 健史*; Mihalache, O.; 島田 幸洋; 田川 明広; 山下 卓哉
日本保全学会第6回学術講演会要旨集, p.250 - 253, 2009/08
高速増殖炉の熱交換器伝熱管の保守保全のため、新型のプローブシステムの設計及び製作を行った。本報告ではシステムの要素技術のうち、複合型光ファイバスコープとレーザー及び画像撮影システムを結合させるカップリング装置及びレーザー加工ヘッドとECT探勝システムを動作させるソフトウェアの開発について述べる。
Mihalache, O.; 上田 雅司; 山口 智彦; 山下 卓哉
Proceedings of 15th International Conference on Nuclear Engineering (ICONE-15) (CD-ROM), 9 Pages, 2007/04
渦電流探傷(ECT)と多重周波数演算を用いて「もんじゅ」の蒸気発生器伝熱管(SH管)と支持板にナトリウムが付着した場合の検出性に関する解析結果について報告する。筆者らが開発した2次元の有限要素法渦電流解析コードを使って、キズや支持板,ナトリウムに流れる磁場を計算し、ナトリウム付着環境下におけるキズ検出のための最適な多重周波数演算法を検討した。多重周波数演算法を用いることで、キズ信号が明確となり、検出性(S/N)が向上することがわかった。
Mihalache, O.; 山口 智彦; 伊達 公司*; 上田 雅司; 山下 卓哉
Proceedings of 12th Asia-Pacific Conference on Non-Destructive Testing 2006 (APCNDT 2006) (Internet), 9 Pages, 2006/11
マルチコイル型リモートフィールド渦電流探傷法を用いた「もんじゅ」の強磁性体である蒸気発生器伝熱管の溶接部付近に存在する微小な欠陥の検出性能について報告する。筆者らが開発した3次元の渦電流解析コードを用いてマルチコイルを試作し、溶接部付近の微小な欠陥を従来式のボビン型より検出性が高いことがわかった。さらに伝熱管の外表面に存在する微小欠陥を鳥瞰図で表現できるようになった。
