针对电站锅炉及压力管道中带台阶的异形结构焊缝超声检测工艺设计及其有效性缺乏评价的问题, 基于超声检测数值模型和检出率模型(Model assisted probability of detection, MAPOD), 构建了不同K值传感器检出率的分析与评价方法。利用该方法对主蒸汽管道带台阶的异形结构焊缝常用检测工艺进行分析。结果表明, 现有以K1和K2探头为组合的检测工艺存在较大的未覆盖区域, 当壁厚为89 mm时, 对应未覆盖区域深度为12 mm;异形结构焊缝中台阶的存在对位于焊缝上部的缺陷回波存在较大影响, 未熔合缺陷自身高度必须大于5 mm, 才能保证检出率达到90%。

A Model assisted probability of detection (MAPOD) method used for reliability analysis of the ultrasonic testing procedure with different angle beam probes for the weld of step-like irregular structure in the power unit is developed based on the ultrasonic numerical model and POD model. The proposed method is used to analyze the conventional inspection procedure of main steam pipe with steps and the result shows that there is an uncovered zone by the composition of K1 and K2 probes. The depth of the uncovered zone is 12 mm when the thickness of pipeline is 89 mm. The echo of defect on the top of weld is influenced by the steps of the weld of irregular structures, and the size of the lack of fusion must be greater than 5 mm to guarantee the 90% of POD.