Multifrequency Eddy Current Inspection for Cracks Under Fasteners
Abstract
The experimental evaluation was conducted on two typical wing splice joint configurations used in the C5-A aircraft consisting of two aluminum layers each 3/16 to 1/4 inches thick. Notches simulating cracks were machined in a radial direction extending from the fastener hole and the faying surface between sheets. A digital eddy-current system designed around a PDP-11/40 minicomputer was utilized for the experimental evaluations. The digital system was programmed to generate the signal wave-forms that excite the test coil and perform the function of phase-sensitive detection of response signals that are received from the test coil. Special test coils were designed to induce eddy currents in the aluminum alloy that lies beneath the head of the fasteners. A series of measurements were taken on the wing-splice samples at various frequencies, excitation levels, and phase settings. These data were analyzed using the Automatic Interaction Detector, AID, computer code to indicate initial capabilities of crack detection, and to compare the various operating parameters such as excitation frequency and test coil design.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 15, 1976
- Accession Number
- ADA040591
Entities
People
- H. T. Gruber
- J. H. Flora
- R. E. Thomas
- R. P. Meister
Organizations
- Battelle Memorial Institute