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DEFECT DETECTION WITH VELOCITY INDUCED EDDY CURRENTS USING A PERMANENT MAGNET

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

DEFECT DETECTION WITH VELOCITY INDUCED EDDY CURRENTS USING A PERMANENT MAGNET, Proc International Workshop on Electromagnetic Nondestructive Evaluation ENDE, Bratislava, Slovakia, Vol. 00, pp. 00 - 00, June, 2013.

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Abstract
Rail flaw detection is at present an important research and development area. The increased use of railway transportation in Europe, the technological developments in trains turned out the safety of the railway network a paramount issue. One item associated with today’s rail track assessment is inspection speed. This paper presents a contribution to attain a solution for this problem. It proposes a testing method whose sensitivity increases with the moving speed of the probe in relation with the material to be tested.
In the approach described in this paper a non destructive technique (NDT) based on velocity induced eddy currents is used to inspect a machined plate. The induction of the eddy currents in the plate is performed with a DC magnetic field provided by a magnet moving in the vicinity of the plate. Very sensitive magnetoresistors (GMR) are used to measure the magnetic field resulting from the perturbation originated in the currents flow pattern by the presence of cracks.