一种新型相移场探头改变导体涡电流分布的理论验证

涡流检测方法广泛应用于导电材料的缺陷检测和无损评价中。受趋肤效应的影响，常规涡流检测法通常只能检测导体表面缺陷。有学者提出了一种相移场探头，并通过实验验证了该探头在满足一定激励条件时，可以达到抑制导体表面涡电流密度，而增加导体深处涡电流密度的效果，从而可以检测导体更深处缺陷。但该结论仅有实验结果，还没有理论方面的验证。本文采用解析方法研究了该相移探头与导体的相互作用，推导出导体中涡电流分布的精确理论表达式，然后分析相位、激励频率对涡电流分布的影响，并计算了导体不同深度涡电流密度分布。从理论上验证了该探头设计及激励方法具有改变导体涡电流密度分布，增加导体深处涡电流密度的效果。

Theory Verification of Changing the Distribution of Eddy Current inside Conductor by a New Phase Shifted Probe

The Eddy Current Testing(ECT)method plays an important role in the nondestructive material test. Due to the skin effect,the conventional ECT method can only detect the surface defects of conductor. Some scholars have proposed a new phase shifted fields probe and drawn a conclusion from experiments that when the probe excit?ed in certain conditions,the surface eddy current density of conductor can be suppressed and the deep eddy current density can be increased,so cracks located in deeper than standard depth of penetration can be detected. But the conclusion was only verified by experiment and without theory verification. The interaction between the phase shift?ed fields probe and the conductor is discussed using analytical method. The accurate theoretical expression of the eddy current distribution inside the conductor is derived and the influences of the phase and the exciting frequency are analysed. The results of the new probe can change the distribution of eddy current and increase the eddy current density in deep of conductor are verified using the analytical calculation method.