Time-domain and frequency-domain eddy current simulations by the finite element method

In this study, the numerical simulations of swept-frequency eddy current (SFEC) and pulsed eddy current (PEC) by means of the finite element method (FEM) are demonstrated. Finite element simulations carried out to analyze the interactions of magnetic fields with two-layer magnetic metal structures (i.e., a bulk metal with coating) are also discussed. The closed-form analytical solutions of swept-frequency eddy current and pulsed eddy current techniques have been successfully applied to the predications of many nondestructive testing (NDT) phenomena. But the analytical solutions are only applicable to simple geometric situations. To predict the EC signals of complicated material structures, numerical methods like boundary element method (BEM) or finite element method are used. The numerical study of single-frequency eddy-current phenomena for NDT purposes has been applied to many practical inspection situations for which analytical solutions are either difficult or impossible to obtain. Since coating inspection and the influence of materials parameters (electrical conductivity, magnetic permeability) are the main concern of NDT applications, we will compare and discuss the numerical prediction results of the frequency-domain swept-frequency eddy current and the time-domain pulsed eddy current by the finite element method.