Design of Unidirectional Single-Mode Electromagnetic Acoustic Transducer for Small Size Specimen Detection
Zhang Chuang1,2, Wei Qi1,2, Liu Suzhen1,2, Yang Qingxin3
1. State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of Technology Tianjin 300130 China; 2. Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei ProvinceHebei University of Technology Tianjin 300130 China; 3. Key Laboratory of Advanced Electrical Engineering and Energy TechnologyTianjin Polytechnic University Tianjin 300387 China
Abstract：For ultrasonic testing of small-size thin plate specimens, the ultrasonic echo signal collected will be very complicated due to the dispersion and multimodal properties of lamb waves,multidirectional emission of electromagnetic ultrasonic transducers and the influence of plate end surface reflection,which is not conducive to further signal analysis. Based on the traditional EMAT and the principle of wave superposition, a new EMAT using four winding coils to excite one-way single mode Lamb waves is designed in this paper. By changing the coil spacing, excitation delay time and current direction, the excitation direction and mode of Lamb wave are selectively controlled and reduce the interference wave in defect detection. The method is applied to the defect detection of small-size plate. Through simulation and experimental comparison with the traditional single-loop EMAT, the feasibility of the new EMAT in the defect detection of thin aluminum sheet with a length of 10 cm is verified. Because the defect echo signal is clear and distinguishable, it greatly reduces the difficulty of subsequent signal processing.
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2019, Vol. 34 
