电磁超声测厚中，被检工件表面粗糙度对检测的稳定性和精度有较大影响。为了探究表面粗糙度对电磁超声测厚的影响，在不同表面粗糙度试件上进行电磁超声测厚试验，给出了试件耦合面和背面不同表面粗糙度下回波信号的幅值和信噪比。结果表明，超声回波幅值及信噪比随着表面粗糙度的增大而减小。从表面粗糙度对超声散射的角度分析了试件背面不同粗糙度对回波幅值的影响；最后,以矩形槽粗糙度元模拟固体粗糙表面，从试件耦合面粗糙度对涡流密度分布及其渗透深度影响的角度分析了表面粗糙度和超声回波信号的关系。

In the thickness measurement with electromagnetic ultrasonic, the surface roughness of the workpiece has a great influence on the stability and accuracy of the detection. In order to explore the influence of surface roughness on the test, the amplitude and SNR of the thickness of the specimen with different surface roughness were presented. The experimental results show that the amplitude of ultrasonic echo and the SNR decrease with the increase of the surface roughness. This paper, based on the ultrasonic scattering angle due to surface roughness, analyzes the influence of different roughness in specimen back face on echo amplitude at first; and then, the relationship between roughness of surface and ultrasonic echo signal was analyzed through establishing the rectangular groove roughness element simulation at a rough solid surface, and by approaching the problem from the effect of specimen coupling surface roughness on eddy current density distribution and on the penetration depth.