Influence of electric charge on numerical simulation of eddy current testing signals due to a conductive crack when using multi-media element

The multi-media finite element (MME) treating the discontinuity of the conductivity within the element was proposed by authors for fast simulation of the eddy current testing (ECT) signals of a conductive crack such as a stress corrosion crack. However, in the cases when eddy current consists of a large component perpendicular to the crack surface, the simulation accuracy is sometimes not very good because of the appearance of electric charge on the crack surface. In this paper, the influences of the surface electric charge on the implementation of the numerical method and on the simulation of the ECT signals were analyzed theoretically. A series of numerical analyses were designed to investigate the scope of feasibility of the MME. The simulation accuracy of the MME for different probe orientations and crack shapes was discussed based on the analysis of the distribution of the surface charge.