焊接结构件的裂纹等表面缺陷,因为应力集中而给材料强度以很大的影响。因此,准确地知道缺陷尺寸,特别是裂纹的深度,这在结构件的安全、可靠性的评价上是很重要的。在维修检查的非破坏性试验中,更要求定量检测出缺陷尺寸。在检测表面缺陷时,通常使用磁力探伤和液体浸透。这些方法能够灵敏地检查缺陷的存在,而不能知道缺陷的深度。做为定量地检查出表面缺陷深度的方法有:涡流法、 Welding structural cracks and other surface defects, because of stress concentration and the material strength to a great impact. Therefore, accurately know the size of the defect, especially the depth of the crack, which is very important in the evaluation of the safety and reliability of the structure. In the maintenance of non-destructive testing, but also require quantitative detection of defect size. In the detection of surface defects, usually magnetic testing and liquid soaked. These methods can sensitively check for the presence of a defect without knowing the depth of the defect. As a quantitative method to check the depth of surface defects are: eddy current method,