Abstract: When it comes to the detection of small-diameter tube defects, eddy current testing using Bobbin probe is the traditional method. But this way is not available to detect the circumferential information of the defect as its inherent disadvantage. Based on the study of eddy current testing, in order to achieve the multiple information from detecting small-diameter tube defects, a novel type of circumferential eccentric Bobbin probe has been proposed and developed. This probe has the ability for both axial scanning and eccentric hoop scanning, which can effectively detect multiple information of small-diameter tube defects. The specific research contents are as follows. With the help of the eddy current testing method, the eccentric and rotatable Bobbin probe is designed suitably for small-diameter tubes, with the model built up for signal simulation. The feasibility of this novel probe is verified by integrating the obtained simulation data, showing the advantages of axial and circumferential scanning for small-diameter tube defects when compared with traditional Bobbin probes. The probe is fabricated and the testing system is established to verify the validity of the developed probe to detect small-diameter tube defects, certifying the superiority and efficiency of the new type of probe further.

Key words: eddy current testing, circumferential eccentric probe, small-diameter tube, multiple defect information, defect location