The application of the rotating magnetic field to eddy current nondestructive evaluation

The work presents the analytical solutions describing the operation of a rotating magnetic field transducer used in the eddy current testing for detecting the long flaws situated parallelly to the inspected cylindrical piece generatrix. The method uses the decaying of the real transducer's three-phase system into an infinite sequence of axial and longitudinal currents whose intensity is giving by a Fourier expansion estimating the electromotive voltage induced in the transducer by solving the equation of diffusion for the three media and considering the boundary conditions, the vector magnetic potential is determined for each medium. The work also presents the most important theoretical parameters of the transducer, as well as the experimental graphs obtained for concrete cases of transducers applications. (author) 5 figs., 4 refs