Pulsed eddy current probe based on rotating blade-shaped excitation coils

When using pulsed eddy current for crack detection, the disturbances generated by microcracks in the induced eddy currents are weak, resulting in a low signal-to-noise ratio in the detection signal. On the other hand, when scanning cracks in multiple directions with a conventional pulsed eddy current probe, it is difficult to achieve maximum sensitivity and determine the crack orientation. This paper proposed a detection method using a mechatronic rotating pulse eddy current probe, which achieved high-sensitivity detection of microcracks in multiple directions. The blade-shaped excitation coil exhibited significant magnetization and directionality. After the mechatronic high-speed rotation of the excitation coil, detection and receiving signals were obtained at different angles. These received signals were then differentially compared with a reference signal to extract small peak variations, creating a map of the relationship between angle position and peak variation. The results of experiment verification and testing indicated that the probe based on the blade-shaped excitation coil rotating within a hollow receiving coil not only had the capability to distinguish crack depths at the sub-millimeter level but also can determine the orientation of cracks with an error of ±5°.