AN EDDY CURRENT SCANNING METHOD FOR THE DETECTION OF CORROSION UNDER FASTENERS IN THICK SKIN AIRCRAFT STRUCTURES

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Authors
  1. Lepine, B.A.
  2. Holt, R.T.
Corporate Authors
Defence and Civil Inst of Environmental Medicine, Downsview ONT (CAN)
Abstract
An eddy current NDT scanning method is presented for inspecting simulated thick skin wing joints for second layer corrosion using a calibration specimen. It was found that single frequency methods are adequate for such configurations when it is known that first layer corrosion, varying air gaps, or fasteners are not present. Frequency mixing is essential, however, for detecting second layer corrosion under installed fasteners in such thick structures. With the appropriate frequency selections, corrosion under the fasteners is observable by minimizing the strong signals from the fasteners. In this case, the smallest detectable corrosion site had a diameter of 12.7 mm (0.5 inch) and a depth of 0.15 mm (6 mils) located in the second lyaer under a fastener with a 9.53 mm (0.375 inch) diameter head. The specimens, in which varying amounts of exfoliation corrosion were developed, were found to be useful for calibrating eddy current scanning inspection set-ups to detect corrosion above a set threshold. This could be useful for inspection of in-service aircraft components of the same material and structural configurations.
Report Number
DCIEM-98-P-80 — Research Paper; Reprint
Date of publication
01 Mar 1997
Number of Pages
8
Reprinted from
Can Aeronautics and Space Journal, vol 43, no 1, 1997, p 28-33
DSTKIM No
99-00207
CANDIS No
510034
Format(s):
Hardcopy;Document Image stored on Optical Disk

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