基于差分脉冲涡流的大提离下坑蚀检测方法研究

Detection Method Research for the Pitting Corrosion under Large Lift-off Based on Differential Pulsed Eddy Current

针对大提离下铁磁性材料坑蚀检测的难题,提出基于差分脉冲涡流的线圈结构。通过实验定性分析3种差分布置方式对信号的影响,表明外部差分可保证信号对称性。进而对比不同提离下外部180°、90°差分结构缺陷信号幅值,表明外部180°差分结构更优。最后在100 mm提离下采用外部180°差分接收线圈3检测直径20 mm、深2.4 mm平底孔,其幅值为0.3 mV,表明该结构可在大提离下检测坑蚀。

Aiming at the difficulty in detecting the pitting corrosion of ferromagnetic materials under large lift-off,a coil structure based on differential pulsed eddy current was proposed.In addition,the effect of three differential arrangements on the signal was qualitatively analyzed through experiments to show that,the external differential can guarantee the symmetry of the signal.Comparing the signal amplitude of the external 180°and 90° differential structures under different lift-offs shows that,the external 180° differential structure is better;making use external 180° differential receiving coil 3 detect both 20-mm-diameter and 2.4-mm-deep flat bottom hole under 100 mm lifting indicates that when the amplitude stays at 0.3 mV,this structure can detect pitting corrosion under large lifting.