一种高信噪比电磁声表面波传感器及在厚壁管道检测中的应用  

A New Surface Wave EMAT with High SNR and the Application for Defect Detection in Thick-walled Pipes

作　　者：何存富[1] 邓鹏[1] 吕炎[1] 焦敬品[1] 吴斌[1] HE Cunfu DENG Peng LU Yan JIAO Jingpin WU Bin(College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology, Beijing 100124)

机构地区：[1]北京工业大学机械工程与应用电子技术学院,北京100124

出　　处：《机械工程学报》2017年第4期59-66,共8页Journal of Mechanical Engineering

基　　金：国家自然科学基金资助项目(51235001;11372016;51505013)

摘　　要：为了提高在自激自收模式下接收信号的信噪比,自行研制一种不同结构配置的电磁声表面波传感器,分析其提高信噪比的机制及影响其信噪比的因素。在自激自收模式下,由于所研制的传感器中磁铁与线圈间存在间隔,降低了磁铁中超声波的影响,进而提高了信噪比。研究结果表明,接收信号的信噪比不仅与提离距离(磁铁与线圈的间隔)有关,而且与其中心频率成正相关关系。所研制的3个不同中心频率电磁声表面波传感器性能测试结果表明,其实测中心频率与设计值一致,其指向性与理论分析相吻合。采用所研制的表面波传感器对标准样块上不同深度的缺陷进行检测,试验结果表明,当缺陷深度约达表面波波长的1/4时,即可检测到该缺陷。进一步选用中心频率1.0 MHz的表面波传感器,实现了对厚壁管道上周向矩形槽、轴向矩形槽和平底孔3种类型缺陷的检测。A type of surface wave EMATs with different configuration is developed to improve the signal to noise ratio （SNR） of receive signal in pulse-echo mode. The mechanism which improve the receive signal SNR and the influence factors are analyzed. It is the interval between magnet and meander-line coil that decrease the disturbance of the ultrasonic in magnet, and then the receive signal SNR are improved. It is shown that the SNR of receive signal is not only related with the interval between magnet and meander-line coil, but also positively correlated with the EMAT center frequency. The performance of 3 surface wave EMATs is evaluated and it is found that the measured center frequency is consistent with the design value and the directivity is agreed well with theoretical analysis. The 5 defects with different depth on the standard block are tested by the developed surface wave EMATs. The testing result shows that the defect can be detected when the depth reaches about 1/4 wavelength. What＇s more, 3 types of defect on a thick-walled pipe such as circumferential rectangular slot, axial rectangular slot and fiat-bottom hole are respectively detected by the developed EMATs with center frequency of 1.0 MHz.

关 键 词：表面波EMAT 信噪比 缺陷检测 厚壁管道 

分 类 号：TB553[理学—物理]