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Inspection Of Ferromagnetic Materials Using High-Field Double Pulse Eddy Currents

Ramos, H. ; Rocha, T. ; Pasadas, D. ; Ribeiro, A. L.

Inspection Of Ferromagnetic Materials Using High-Field Double Pulse Eddy Currents, Proc Electromagnetic Nondestructive Evaluation International Workshop on Electromagnetic Nondestructive Evaluation ENDE, Lisbon, Portugal, Vol. proceedings, pp. 32 - 39, September, 2016.

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The inspection of ferromagnetic materials for surface defects is usually made using the Magnetic Flux Leakage (MFL) technique. By magnetically saturating the specimen, some magnetic flux lines will escape the material in the presence of a defect, which can be used to detect and characterize the defect. However, the saturation of the ferromagnetic specimen when motion is involved can be troublesome, which can be a disadvantage in cases such as railroad inspection. This work proposes a new technique to inspect the surface of ferromagnetic materials based on eddy currents. The technique creates two consecutive pulses of currents (up to 1500 A) in a coil that generates a high magnetic field (peak around 3.5 T) in the vicinity of the sample. Simulations were made to show the method is able to detect defects in a ferromagnetic sample. Signal processing was applied to the obtained data in order to reduce the MFL component and give emphasis to the eddy currents perturbations.