When circumferential ultrasonic testing is performed on cylindrical item with thick wall, the testing sensitivity of internal surface radial defects is affected by various factors. The authors systematically analyze the characteristic of SW technique, double wave modes technique, small angle LW tangent internal surface technique, deformation SV corner-echo technique and deformation SW tangent internal surface technique, based on the investigation of technical problems of circumferential ultrasonic testing for internal surface radial defects in cylindrical item with thick wall. The formula of ultrasonic echo of internal surface radial defects detected using above techniques is presented based on theoretical analysis. The ultrasonic testing sensitivity experiments are performed on test samples with artificial internal surface radial defects, and the experimental results are analyzed and discussed.%对厚壁筒形件进行周向超声检测时，超声波对内表面径向缺陷的检测灵敏度受到多种因素的影响。在研究厚壁筒形件内表面裂纹周向超声检测的主要技术难点的基础上，系统地分析了纯横波技术、双重波型检测法、小角度纵波切内壁法、变型横波端角反射法、变型横波切内壁法等方法的技术特点。通过理论分析提出上述方法的内表面径向缺陷回波波高公式。对含有人工表面缺陷的对比试块进行了灵敏度试验，并对试验结果进行了分析与探讨。
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