DETECTING CRACKS UNDER FERROUS FASTENERS USING THE NORTEC-30 EDDYSCAN FASTENER HOLE INSPECTION INSTRUMENT

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Authors
  1. Nolan, R.W.
  2. McRae, K.I.
Corporate Authors
Defence and Civil Inst of Environmental Medicine, Downsview ONT (CAN)
Abstract
A Nortec-30 Eddyscan Fastener Hole Inspection Instrument was used to detect known fatigue cracks under the heads of alloy steel fasteners installed in 0.258" diameter countersunk fastener holes drilled through 0.330" pieces of 7075-T651 aluminum alloy plate. It was found that magnetic fields caused by prior mangnetization in a majority of ferrous fasteners resulted in large numbers of false indications. When non-ferrous or non-magnetized ferrous fasteners were used, the Nortec-30 was able to reliably detect relatively small flaws in the holes underneath the heads of these fasteners. Since the rotating coil eddy current technique is dependent upon the magnetic condition of the fastener, the Nortec-30 is not recommended for use with ferrous fastening systems.
Keywords
Fatigue cracks;Cracks under fasteners;Non-destructive inspection;Ferrous fasteners;Nortec-30 Eddyscan
Report Number
DCIEM-97-TM-12 — Technical Memorandum
Date of publication
01 Feb 1997
Number of Pages
15
DSTKIM No
98-00145
CANDIS No
502974
Format(s):
Hardcopy;Document Image stored on Optical Disk

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