传统激光-电磁超声对表面裂纹检测的灵敏度受表面裂纹方向的影响, 为解决这一问题, 提出了一种基于环形电磁超声探头的激光-电磁超声无损检测方法。 相比于传统的激光-电磁超声表面裂纹检测方法, 该方法不但具有更高的灵敏度, 而且不受裂纹方向的影响。为了验证该方法的有效性, 设计了一种环形电磁超声探头, 并对其线圈参数进行了优化, 提高了检出信号的信噪比; 进而利用该环形探头有效检出了试件中的不同方向表面裂纹。

With using pulsed laser to excite electromagnetic acoustic transducers (EMATs) and generate ultrasonic waves, laser-EMAT can provide a noncontact ultrasonic testing (UT) method. To overcome the drawback that sensitivity of traditional laser-EMAT UT method is dependent on the direction of defect to be measured, a modified laser-EMAT UT method with using a ring EMAT is proposed in this work. Compared to the traditional laser-EMAT method, the sensitivity of the laser-ring EMATUT is much higher, and independent to the crack orientation. To validate the feasibility of this method, a ring EMAT is firstly designed and optimized to improve the sensitivity for laser ultrasound detection. Then, the laser-ring EMAT system is applied to scan a specimen with a normal surface crack.