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Circuit-field coupled finite element analysis method for an electromagnetic acoustic transducer under pulsed voltage excitation

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Chinese Physics B 2011年第6期20卷 490-497页

作者：郝宽胜黄松岭赵伟王珅 State Key Laboratory of Power Systems Department of Electrical Engineering Tsinghua University

This paper presents an analytical method for electromagnetic acoustic transducers （EMATs） under voltage excitation and considers the non-uniform distribution of the biased magnetic field. A complete model of EMATs including the non-uniform biased magnetic field, a pulsed eddy current field and the acoustic field is built up. The pulsed voltage excitation is transformed to the frequency domain by fast Fourier transformation （FFT）. In terms of the time harmonic field equations of the EMAT system, the impedances of the coils under different frequencies are calculated according to the circuit-field coupling method and Poynting＇s theorem. Then the currents under different frequencies are calculated according to Ohm＇s law and the pulsed current excitation is obtained by inverse fast Fourier transformation （IFFT）. Lastly, the sequentially coupled finite element method （FEM） is used to calculate the Lorentz force in the EMATs under the current excitation. An actual EMAT with a two-layer two-bundle printed circuit board （PCB） coil, a rectangular permanent magnet and an aluminium specimen is analysed. The coil impedances and the pulsed current are calculated and compared with the experimental results. Their agreement verified the validity of the proposed method. Furthermore, the influences of lift-off distances and the non-uniform static magnetic field on the Lorentz force under pulsed voltage excitation are studied.

关键词： electromagnetic acoustic transducer nondestructive testing circuit-field coupling finite element method

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Shear Wave Field Radiated by an electromagnetic acoustic transducer

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Chinese Physics Letters 2006年第12期23卷 3294-3296页

作者：吴迪李明轩王小民 Institute of acoustics Chinese Academy of Sciences Beijing 100080

The horizontally polarized ultrasonic shear wave field emitted by an electromagnetic acoustic transducer （EMAT） is studied by the surface force distribution on the EMAT approximately described as an inhomogeneous horizontal shear force. The shear wave directivity pattern is plotted by numerical calculations based on our strictly analytic solutions of the wave field we presented previously. An experimental system of EMAT generation and piezoelectric transducer reception is set up to check the predictions of the theoretical wave field by measuring the ultrasonic signals through aluminium block. The directivity pattern of the wave field obtained from the experimental results conforms the theoretical prediction, which lays a foundation for engineering applications of EMATs.

关键词： Shear Wave Field Radiated electromagnetic acoustic transducer

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Optimal Design of electromagnetic acoustic transducer

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Journal of Energy and Power Engineering 2012年第4期6卷 561-569页

作者： Eiji Matsumoto Shinji Kitamura Jun Abe Department of Energy Conversion Science Kyoto University Kyoto 606-8501 Japan Kyoto Research ＆ Development Center Mitsubishi Motors Corporation Kyoto 616-8501 Japan Energy Technology Laboratories Osaka Gas Osaka 554-0051 Japan

This paper considers the design of EMAT （Electro-Magnetic acoustic transducer） based on numerical simulation. The EMAT consists of an exiting coil and two permanent magnets, which transmits the ultrasonic wave by the Lorentz force between the eddy current and the static magnetic field by the magnets. From the experimental result on self-prepared EMATs, the intensity and the directivity of the transmitted wave depend on the widths of the coil and the magnets. By means of EEM analysis the authors attempt to determine the optimal values of the above widths such that both the intensity and the directivity achieve the maximum or allowable performance.

关键词： acoustics actuators eddy current electromagnetic acoustic transducer finite element methods magnetic forces sensors

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Modeling and finite element analysis of transduction process of electromagnetic acoustic transducers for nonferromagnetic metal material testing

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Journal of Central South University 2011年第3期18卷 749-754页

作者：郝宽胜黄松岭赵伟段汝娇王珅 State Key Laboratory of Power Systems Department of Electrical EngineeringTsinghua University

Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle displacements in the simulation model of electromagnetic acoustic transducer （EMAT）, a multi-field coupled model was established and the finite element method （FEM） was presented to calculate the entire transduction process. The multi-field coupled model included the static magnetic field, pulsed eddy current field and mechanical field. The FEM equations of the three fields were derived by Garlerkin FEM method. Thus, the entire transduction process of the EMAT was calculated through sequentially coupling the three fields. The transduction process of a Lamb wave EMAT was calculated according to the present model and method. The results show that, by the present method, it is valid to calculate the particle displacement under the given excitation signal and non-uniformly distributed static magnetic field. Calculation error will be brought about if the non-uniform distribution of the static bias magnetic field is neglected.

关键词： metal material nondestructive testing electromagnetic acoustic transducer multi-field coupling Garlerkin method finite element

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Micro-Sized Pinhole Inspection with Segmented Time Reversal and High-Order Modes Cluster Lamb Waves Based on EMATs

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Chinese Journal of Mechanical Engineering 2023年第1期36卷 224-236页

作者： Jinjie Zhou Yang Hu Xiang Li Yang Zheng Sanhu Yang Yao Liu School of Mechanical Engineering North University of ChinaTaiyuan030051China School of Aeronautics and Astronautics University of Electronic Science and Technology of ChinaChengdu611731China China Special Equipment Inspection and Research Institute Beijing100029China

Pinhole corrosion is difficult to discover through conventional ultrasonic guided waves inspection,particularly for micro-sized pinholes less than 1 mm in *** study proposes a new micro-sized pinhole inspection method based on segmented time reversal(STR)and high-order modes cluster(HOMC)Lamb ***,the principle of defect echo enhancement using STR is *** and STR inspection experiments were conducted on aluminum plates with a thickness of 3 mm and defects with different diameters and *** parameters of the segment window are discussed in *** results indicate that the proposed method had an amplitude four times larger than of conventional ultrasonic guided waves inspection method for pinhole defect detection and could detect micro-sized pinhole defects as small as 0.5 mm in diameter and 0.5 mm in ***,the segment window location and width(5-10 times width of the conventional excitation signal)did not affect the detection *** combination of low-power and STR is more conducive to detection in different environments,indicating the robustness of the proposed *** with conventional ultrasonic guided wave inspection methods,the proposed method can detect much smaller defect echoes usually obscured by noise that are difficult to detect with a lower excitation power and thus this study would be a good reference for pinhole defect detection.

关键词： Pinhole corrosion High-order modes cluster Lamb waves Segmented time reversal inspection electromagnetic acoustic transducer

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