Title :
Measurements of surface-breaking flaws in ferromagnetic plates by means of an imaging SQUID susceptometer
Author :
Bruno, A.C. ; Ewing, A.P. ; Wikswo, J.P., Jr.
Author_Institution :
Dept. de Fisica, Univ. Catolica do Rio de Janeiro, Brazil
fDate :
6/1/1995 12:00:00 AM
Abstract :
We detected sub-millimeter surface-breaking flaws in ferromagnetic plates using an imaging SQUID susceptometer. The normal component of the field was imaged with an axial, first order gradiometer with 3 mm diameter coils and a 4 cm baseline. We mapped the field above mild steel test samples, detecting field distortions due to surface flaws with volumes as small as 0.1 cubic millimeter. A comparison is made with conventional flux leakage methods. Our method of observing distortions in a perpendicularly applied field may be more sensitive for detecting surface-breaking flaws. Image enhancement techniques successfully removed background signals with low spatial frequencies.<>
Keywords :
SQUID magnetometers; SQUIDs; ferromagnetic materials; flaw detection; image enhancement; magnetic flux; background signals; ferromagnetic plates; field distortions; first order gradiometer; flux leakage methods; image enhancement techniques; imaging SQUID susceptometer; mild steel; perpendicularly applied field; surface-breaking flaws; Coils; Extraterrestrial measurements; Magnetic field measurement; Magnetic flux leakage; Magnetic shielding; SQUID magnetometers; Spatial resolution; Steel; Superconducting magnets; Testing;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
