【作者】 王丽；

【导师】 武新军；

【作者基本信息】 华中科技大学 ， 机械电子工程， 2014， 硕士

【摘要】 电磁超声检测作为一种新型超声检测方法，具有非接触、无需耦合剂的优点，成为近年来超声无损检测领域研究的热点之一。本学位论文利用表面波单模态、无频散的特性，研制了可用于钢板表面扫查检测的电磁超声表面波检测传感器，并对其检测信号特性作了详细分析。首先基于钢板的铁磁特性，通过仿真分析和实验验证的方法研究了回折线圈垂直磁化结构传感器检测原理，给出了其在不同厚度钢板上电磁超声表面波激励参数的理论计算步骤。然后通过仿真分析确定了传感器空间布置距离、提离、磁铁数目等主要参数，在此基础上，研制了具有一定提离可在钢板表面任意方向扫查检测的电磁超声表面波检测传感器。最后搭建了扫查实验台，获取了钢板表面人工刻槽、球形孔和平底孔三种缺陷的电磁超声表面波传感器检测信号，并进行了详细分析，得到了一种基于声波干涉增强现象的检测方法。结果表明：当接收单元的位置相对刻槽满足一定条件时，刻槽缺陷通过信号增强10%~20%；通过提取线扫查信号衰减起始点可实现钢板表面球形孔截面直径反演，相对误差小于17%；而平底孔线扫查信号中的衰减起始点和信号增强点都能实现平底孔截面直径反演，相对误差均在12%以内。本学位论文的研究工作丰富了电磁超声检测方法，有利于电磁超声检测技术的推广应用。更多还原

【Abstract】 As a new ultrasonic testing method, Electromagnetic acoustic technology has been ahotspot in ultrasonic nondestructive testing field in recent years due to its non-contactcharacteristic and being free of couplant. In this thesis, an electromagnetic acoustictransducer(EMAT) is developed for surface wave scanning inspection on the steel plate basedon the signal-mode and no dispersion characteristics of surface wave. And the features of thescanning signals are discussed in detail.Firstly, according to the ferromagnetic properties of the steel plate, the testing principle ofthe tranducer with meander coil and vertical magnetization structure is investigated through themethod of simulation analysis and experimental verification. Then the theoretical calculationsteps of surface wave excitation parameters are given. Secondly, when the main structureparameters, such as spatial arrangement, lift-off and number of magnets, are determined by thesimulation analysis, a surface wave EMAT is developed with some lift-off conveniently for thescanning inspection in any direction on the steel plate surface. Finally, the scanning testingplatform is set up to conduct the experiments of slot testing, spherical hole testing and flatbottom hole testing. The detailed analysis on the scanning signals show that the steel platesurface can be tested based on interference enhancement of surface waves; when the transduceris placed in certain location from slots, the ultrasonic signal enhances10%~20%; for thespherical holes, one of the turning points that is easy to be get from the scanning signals isutilized to calculate the surface section diameters of spherical holes and the relative error iswithin17%; for the flat bottom holes, two of the turning points can be used to calculate thediameters of flat bottom holes and both the relative errors are within12%.The work in this dissertation enriches the methods of electromagnetic ultrasonic testingand is significant to promote the application of electromagnetic ultrasonic technique.更多还原