Efficient numerical simulation of eddy current pulsed thermography NDT signals based on FEM-BEM method and energy equivalent principle

The numerical simulation of eddy current pulsed thermography (ECPT) signals can be divided into two parts, the computation of electromagnetic field and the simulation of thermal field. It is difficult to obtain accurate ECPT signal efficiently due to the high excitation frequency and the short heating stage. In this study, due to the linear characteristic of the electromagnetic field numerical simulation, the eddy current field has been obtained rapidly through the superposition of eddy current response signals of harmonic excitation current based on the FEM-BEM method. The heat source of temperature field has been obtained by the equivalence of eddy current filed based on energy equivalent principle. The temperature signals of ECPT are computed using the time step iteration algorithm. The proposed method is proved to be accurate and significantly efficient through numerical validation and ECPT experiments. Finally, the quantitative analysis of the temperature decay in SUS 304 plate shows that, at the skin depth of eddy current, the temperature difference decays to 90.22% of the plate surface, while the eddy current decays to 1/e.