基于刀片式激励线圈旋转的脉冲涡流探头

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

脉冲涡流检测裂纹时,微裂纹在感应涡流中产生的扰动微弱,检测信号的信噪比低;另一方面,单向扫查下的常规脉冲涡流探头难以获得多向裂纹检测的最大灵敏度和判断裂纹方向。提出一种采用机电旋转脉冲涡流激励线圈的检测方法,实现了多方向微裂纹的高灵敏度检测。刀片式激励线圈具有明显的聚磁性与方向性,机电旋转激励线圈后可以获得不同转角下的接收信号,将该接收信号与基准信号进行差分,提取出微小的峰值变化量,得到角度与峰值变化量之间的图谱。试验验证与测试结果表明:基于刀片式激励线圈在空心接收线圈内旋转的脉冲涡流探头不仅具有亚毫米级裂纹深度区分的检测能力,且能有效分辨裂纹方向,误差为±5°。

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°.