考虑表面粗糙度的接触式超声衰减系数校正方法

材料的表面质量会显著影响超声衰减系数的准确测量。根据表面粗糙度对垂直入射的超声波束传播的影响，提出了考虑表面粗糙度的接触式超声衰减系数校正方法。首先基于未耦合时粗糙界面反射系数校正理论和光滑界面耦合时的反射系数计算公式，推导出耦合时粗糙界面的反射系数表达式。在此基础上结合衰减系数计算公式提出了包含粗糙度信息的接触式超声衰减系数校正方法。最后，制备了不同表面粗糙度的45钢和304不锈钢柱体试件，搭建了衰减系数超声测量平台，通过实验分析了表面粗糙度对信号时域和频域的影响，验证了提出的校正方法的有效性和实用性。实验结果表明，提出的衰减模型能有效补偿粗糙度引起的超声背散射信号衰减，透射法相对测量误差在6%以内。

Method of contact ultrasonic-attenuation coefficient correction considering surface roughness

The surface quality of material significantly affects the accurate measurement of the ultrasonic attenuation coefficient. According to the influence of surface roughness on the propagation of a vertical incident ultrasonic beam, a method of contact ultrasonic-attenuation coefficient correction considering surface roughness was proposed. Firstly, based on the correction theory of reflection coefficient of rough interface in the case of uncoupling and the calculation formula of reflection coefficient of smooth interface in the case of coupling, the formula of reflection coefficient of rough interface in the case of coupling was derived. Then, a method of contact ultrasonic attenuation coefficient correction including roughness information based on the formula of attenuation coefficient was proposed. Finally, cylinder specimens of 45 steel and 304 stainless steel with different surface roughness were prepared, and the ultrasonic measurement platform of attenuation coefficient was established. The influence of surface roughness on signal time domain and frequency domain was investigated to verify the validity and practicability of the proposed correction method. Experimental results show that the proposed attenuation model can effectively compensate the attenuation of ultrasonic backscattered signal caused by roughness, and the relative measurement error of transmission method is less than 6%.