高纯度横波蝶形线圈电磁超声换能器优化设计  

Optimization Design of High-Purity Shear Wave Electromagnetic Acoustic Transducer with Butterfly Coil

作　　者：董明[1,2] 李航辉 马宏伟[1,2] 陈渊[2] 曹现刚[1,2] Dong Ming;Li Hanghui;Ma Hongwei;Chen Yuan;Cao Xiangang(School of Mechanical Engineering,Xi’an University of Science and Technology,Xi’an,710054,China;State Key Laboratory of Mine Electromechanical Equipment Intelligent Detection and Control of Xi’an University of Science and Technology,Xi’an,710054,China)

机构地区：[1]西安科技大学机械工程学院,西安710054 [2]西安科技大学陕西省矿山机电装备智能检测与控制重点实验室,西安710054

出　　处：《电工技术学报》2024年第11期3270-3279,共10页Transactions of China Electrotechnical Society

基　　金：国家自然科学基金(51705418,52175518,52274158);陕西省自然科学基础研究计划—陕煤联合基金(2021JLM-07)资助项目。

摘　　要：蝶形线圈电磁超声换能器(EMAT)能够在铝块中同时激发出超声横波和纵波,接收信号中存在横波反射回波和纵波反射回波,纵波回波会影响缺陷检测的准确性。该文设计了一种变尺寸蝶形线圈EMAT,通过改变线圈不同位置导线的宽度与间距,改变不同位置的换能效率,以实现横波的增强和纵波的抑制。首先,考虑永磁体的空间磁场分布,分析蝶形线圈EMAT不同位置导线所受洛伦兹力与激发超声波类型的关系,结合有限元声场云图,得到EMAT接收信号中存在多个回波的原因;其次,研究线圈参数对换能效率和横波纵波幅值比的影响规律,利用有限元仿真确定变尺寸EMAT的设计参数;最后,制备常规与变尺寸蝶形线圈EMAT,采集无缺陷铝合金试块的回波,结果表明,当永磁体直径与线圈中心宽度比为1.92时,纵波幅值削弱了66.1%,横波幅值增大了36.3%,横纵波幅值比从5.8升至23.1。该文设计的变尺寸蝶形线圈EMAT实现了对纵波的削弱和横波的增强,提升了横波电磁超声内部缺陷检测的可靠性。The electromagnetic acoustic transducers(EMATs)are electromagnetically coupled ultrasonic transducers which can generate and detect ultrasonic waves on electrically conducting media.Compared with spiral coil,butterfly coil EMAT has the highest eddy current and pressure at the central axis,which has significant advantages in detection of inner defects and thickness measurement.The butterfly coil EMAT is easy to generate shear waves and longitudinal waves in an aluminum block.The echo of longitudinal wave will be judged as a defect echo,which brings a big challenge to defect identification.To improve the detect ability,an optimization design method for high-purity shear wave electromagnetic acoustic transducer with butterfly coil is prosed.Firstly,the spatial magnetic field distribution of the permanent magnet was taken into account,and the relationship between the Lorentz force and the type of excitation ultrasonic waves at different positions of the butterfly coil EMAT was analyzed.The propagation characteristics of the ultrasonic waves were examined in a 2D finite element simulation model,and the causes of multiple echoes were analyzed.The echo of the longitudinal wave will be judged as a defect echo,which can lead to inaccurate detection results.Secondly,a butterfly coil with varied size was proposed,where the wire width and spacing of the butterfly coil varies with the position,simultaneously,the transduction efficiency was altered.The longitudinal waves were suppressed while shear waves were enhanced,and high-purity shear waves were achieved.The influence of butterfly coil parameters on the excitation efficiency and the amplitudes ratio of shear and longitudinal wave was studied,and the optimized parameters were determined through finite element simulation.Finally,the equal-size and varied-size butterfly coil EMAT were prepared for the comparison experiment involving shear wave excitation and defect detection.The experimental results showed that when the magnet-to-coil width ratio reached approximately 1.92,t

关 键 词：横波电磁超声换能器 高纯度横波 变尺寸蝶形线圈 缺陷检测 

分 类 号：TB552[理学—物理] TM93[理学—声学]