基于B_z(p_(max))相轨迹的电磁涡流无损检测方法

基于电磁涡流检测的变压器等效理论,提出一种相轨迹分析方法。该方法对正弦激励下空间磁通密度信号进行相敏解调,并绘制其相轨迹图。仿真及实验结果表明,在激励线圈所在平面上,磁通密度法向分量B_z在其空间极大值点处p_(max)呈现出良好的线性特征:随提离高度变化,其R-I平面上相轨迹按固定参数线性变化;而被测铝板表面或内部的微小缺陷则会引起线性化参数的明显改变。该结论为设计对提离高度不敏感的电磁涡流检测装置提供了理论指导。

Electromagnetic eddy current nondestructive testing method based on the phase trajectory of Bz(pmax)

A phase trajectory analysis method is proposed based on the transformer equivalent theory of electromagnetic eddy current detection. The phase sensitive demodulation of the space magnetic flux density signal under sinusoidal excitation is carried out and the phase trajectory is drawn with this method. The simulation and experiment results show thatBz, the normal component of the magnetic flux density, shows good linear features at its spatial maximum value point on the plane of the excitation coil. The phase trajectory on the R I plane changes linearly with fixed parameter as the lift off changes. While the tiny defects on the measured aluminum plate surface or inside the aluminum plate can cause significant changes of the linear parameter. This conclusion provides a theoretical guidance for the design of electromagnetic eddy current testing device insensitive to lift off.