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EDDY CURRENT MODELING OF FERRITE-CORE PROBES, APPLICATION TO THE SIMULATION OF EDDY CURRENT SIGNALS FROM SURFACE BREAKING FLAWS IN AUSTENITIC STEEL

Abstract: The CEA has developed a fast model for the simulation of ferrite-cored probes. This model is based on the formalism of the Green's dyadic functions. It can be used for the design of new probes and for the simulation of Eddy Current (EC) signals. This paper presents the simulation of EC signal from surface breaking flaws in austenitic stainless steel. The effect of the ferrite core is analyzed in the normalized impedance diagram and the distribution of the EC in an austenitic slab is given for a ferrite-cored probe. It is shown that the responses of an absolute coil and of a transmit/receive probe can be significantly different regarding to the length of a notch. The model has been validated by comparison with experimental data in the framework of a joint project between CEA and EDF aimed at the characterization of the depth of surface breaking flaws in austenitic stainless steel 304L. The simulation of absolute, differential and transmit/receive probe with ferrite core will be integrated in the Non Destructive Testing (NDT) platform CIVA.