Assessment of Defects in Ferromagnetic Metals with Eddy Currents.
Abstract
Available from UMI in association with The British Library. 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.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1989
- Bibcode:
- 1989PhDT........33O
- Keywords:
-
- Physics: Condensed Matter