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Title: Assessment of defects in ferromagnetic metals with eddy currents
Authors: Oaten, Susan Rosemary
Advisors: Blitz, J
Issue Date: 1989
Publisher: Brunel University Institute for the Environment PhD Theses
Abstract: A study was made to identify and size surface breaking defects in ferromagnetic materials with eddy currents, whilst eliminating unwanted signals due to changes in magnetic permeability and probe lift-off. The former was overcome by the use of high frequencies and the latter by utilising the lift-off to characterise the defects. The lift- off or "touch" method was shown to be advantageous in that one could test steel objects having irregular surfaces, such as occurring with the presence of welds. In addition a theoretical investigation was undertaken to relate changes in the magnetic permeability, electrical conductivity and values of lift-off to the components of impedance of a detecting coil located above the plane surface of a ferromagnetic metal. The resultant theory was confirmed by experimental measurements.
Description: This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.
Appears in Collections:Institute for the Environment

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