Study on flux-differential type eddy-current testing technique by planar coils

提出了一种以感应电压作为传感信号的新型平面型涡流探头。作为一种先进的无损检测手段，我们研究了该ECT探头的检测特性及其应用。本课题的研究成果如下：1.曲折/网状平面探头的研制我们研制出了性能最优的平面型ECT探头，其中曲线型线圈用作激励线圈，网状线圈用作传感线圈。该探头结构灵活，可近距离扫描物体表面。2.平面电容层析成像探头的特性根据先进的电容层析成像技术，实际需要对裂纹或缺陷的形状、大小和方向进行检测。实验证明，ECT探头对1.0 mm铜板60%、10 mm的外裂纹具有足够的检测灵敏度。传感信号的二维成像模式使我们能够给出裂纹的大小、形状和方向的信息。用Inconel 600板作为核电厂的管材，对其检测特性进行了测试。3.采用ECT法检测印制线路，探讨了利用该探头检测印制线路断开的可能性。为了在印制布线上产生涡流，ECT探头的曲流激励线圈具有合适的结构。实验中，我们证实了我们可以检测到断开的信号。但为了检测复杂接线图形上的缺陷，还需要在正常的接线板上使用比较技术作为示教信号。

We proposed a new planar type eddy-current probe that detects induced voltage as sensing signal. We researched the detection characteristics and application of this ECT probe as one of the advanced non-destructive inspection. The achievements of the research project are follows ;1.Fabrication of meander/mesh planar probeWe developed the planar ECT probe as most excellent ECT structure where a meander type coil, and a mesh coil are used as exciting, and sensing coils respectively. The probe is flexible in structure and can be scanned close to the surface of object. Particularly, it is easy to fabricate it by etching techniques.2.Characteristics of the planar ECT probeRegarding the advanced ECT techniques, the detection of shape, size, and direction of crack or defect is needed actually. We confirmed experimentally that the ECT probe has the sensitivity enough to detect the 60%, 10mm outside crack with 1.0mm copper plate. The 2-D imaging pattern of the sensing signal enables us to give the information of size, shape, and direction of crack. And we measured the detecting characteristics by using Inconel 600 plate which is pipe-material at atomic power plant.3.Inspection printed wiring by using ECT approachWe discussed the possibility of using ways of this probe to inspect disconnections in printed wirings. To induce eddy currents on printed wiring, the meander exciting coil of the ECT probe has the suitable structure. Experimentally, we confirmed that we can detect the signal of disconnection. But to check the defect on the complicated wiring pattern, we also need the comparison techniques as teaching signal at the normal wiring board.