电磁超声检测钢板厚度实验的参数优化∗

摘要

In order to improve the SNR of the thickness measurement testing,study the effects caused by the excita-tion signal and transducer lift-off distance, setting the electromagnetic ultrasonic experiment system. Using the system RITEC-SNAP 5000 produced high-energy sine wave to excite the electromagnetic ultrasonic transducer ( EMAT) ,by adjusting the frequency of the excitation signal,pulse width,change the lift-off distance to observe the change of the ultrasonic echo amplitude. The experiment results showed that,when the excitation frequency was e-qual to the inherent frequency of EMAT,the transducer high worked efficiency;using six cycles of pulse sequence, the wave boundary between before and after was apparent;in order to obtain larger echo amplitude,the lift-off dis-tance should be minimized.%为提高电磁超声检测信号的信噪比，研究激励信号频率、脉宽及换能器提离距离对厚度测量结果的影响，搭建了电磁超声实验系统。该系统利用RITEC-SNAP 5000产生高能正弦波激励电磁超声换能器EMAT ( Electromagnetic Acoustic Trans-ducer)，通过调节激励信号的频率、脉宽，改变提离距离来观测超声回波幅度的变化。实验结果表明：当激励频率和EMAT固有频率相同时其换能效率最高，采用6个周期的脉冲串时前后波包之间分界明显，为获得较大的回波幅度应尽可能减小提离距离。