This paper presents an integral formulation for the calculation of the eddy-current problems in moving conductors in the presence of magnetic media. The quasistationary Maxwell equations are written in local reference frames associated with moving bodies. Only the conducting and ferromagnetic domains are discretized. The eddy current is described in terms of a two component electric vector potential for which edge elements are used along with the tree-cotree decomposition. The magnetization is assumed to be uniform in each element of the ferromagnetic domain. Time stepping is used for time integration. The nonlinear problem is solved using Picard iteration, for which convergence is guaranteed. Only a part of the relevant matrices must be formed at each time step. The features of the method are illustrated with the aid of some numerical results
Pulse eddy currents are proposed as a nondestructive testing (NDT) technique to detect flaws in conductive structures with large thickness. The harmonic component of a pulse is rich, the pickup signal containing the amount of information corresponding to multifrequency analysis. Due to the short time length of the pulse, the amplitude of the excitation increases up to 100 times of the amplitude for an ac signal. Both direct simulation of pulse eddy-currents phenomena using an A-FEM-BEM code and neural networks-based inversion techniques are performed. Numerical results for the inversion of signals due to outer defects are shown.
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