Accession Number : ADA337500

Title :   Detecting Cracks under Ferrous Fasteners Using the Nortec-30 Eddyscan Fastener Hole Inspection Instrument

Descriptive Note : Technical memo

Corporate Author : DEFENCE AND CIVIL INST OF ENVIRONMENTALMEDICINE DOWNSVIEW (ONTARIO)

Personal Author(s) : Nolan, Richard W. ; McRae, Kenneth I.

PDF Url : ADA337500

Report Date : MAR 1997

Pagination or Media Count : 12

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 in. diameter countersunk fastener holes drilled through 0.330 in. pieces of 7075-T651 aluminum alloy plate. It was found that magnetic fields caused by prior magnetization in a majority of ferrous fasteners resulted in large numbers of false indications. When nonferrous or non magnetized ferrous fasteners were used, the Nortec-30 was able to reliably detect relatively small flaws in the holes underneath the beads 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.

Descriptors :   *FASTENINGS, NONDESTRUCTIVE TESTING, CRACKING(FRACTURING), CANADA, FATIGUE(MECHANICS), IRON ALLOYS, EDDY CURRENTS.

Subject Categories : Couplers, Fasteners, and Joints

Distribution Statement : APPROVED FOR PUBLIC RELEASE