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Sub-Surface Defect Detection with Motion Induced Eddy Currents in Aluminium

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

Sub-Surface Defect Detection with Motion Induced Eddy Currents in Aluminium, Proc IEEE International Instrumentation and Technology Conf. - I2MTC, Pisa, Italy, Vol. 0, pp. 0 - 0, May, 2015.

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Abstract
Nondestructive testing in situations where there is a
moving media has always been a challenging task. Motion
induced eddy current testing is a good solution for testing
metallic surfaces, as it does not require contact with the sample.
This work presents a method to detect sub-surface defects in nonferromagnetic
material with motion induced eddy currents. A
numerical model was used to verify the progression of eddy
currents along the depth of a conductive plate and to obtain the
magnetic field perturbation in the presence of sub-surface
defects. A probe, including a permanent magnet to induce eddy
currents and a magnetic sensor was moved in the vicinity of an
aluminium plate with sub-surface defects to obtain experimental
data and the results compared to those obtained with the
numerical model. At higher speeds, the time of diffusion of
deeper eddy currents takes, makes it possible to also estimate the
depth of a sub-surface defect by measuring how far away the
perturbation is from the moving magnet.