Eddy current testing is a non-destructive testing method that has usually used for examination of carbon steel tubes. By using a high frequency electromagnetic field on the exciting probe, it is easy to figure out the impedance variation of the coil on impedance plane, and estimate the crack depth by measuring the angle of curve. However, different kind of tubes and electromagnetic properties resulted in different testing. The purpose of this study is to create the two dimensional axial symmetry model of eddy current testing by finite element software package FEMLAB. And it is easy to estimate the crack depth by figuring the impedance plane and evaluation curves by MATLAB. Furthermore, the research analyzed the variation of curves and angles on an impedance plane and tried to reduce testing errors. Over all, the analysis of some influence factors of eddy current testing in the present study not only provides a standard of estimating crack depth more accurately, but also reduces the evaluation errors.

Eddy current testing is a widely-used examination of the nondestructive testing method. According to the theory of electromagnetic induction, the coil impendence varies with the interaction between the coil magnetic field and the eddy current magnetic field. By observing the variations of the phase angle and the impendence plane diagram, the influence of different defects and factors are evidently presented. The purpose of this study is to analyze the three-dimensional defects of eddy current testing by means of the finite element method. To begin with, a complete 3-D electromagnetic model in eddy current testing by finite element software package COMSOL Multiphysic was created. Then the impendence plane diagram and evaluation curves are drawn by the mathematics software package MATLAB to show the variations of the impendence and the phase angle. Moreover, the results show the effect of reducing testing errors. The simulation of 3-D defect model can provide more comparable data for experimentalists. So that the problem of inappropriate judgement can be prevented, and then the accuracy in eddy current testing can be enhanced.