The use of low-frequency eddy currents to detect subsurface cracks in aluminium aircraft structure has become a standard inspection method in the past few years. The application of this technique has become possible mainly due to recent developments in phase-sensitive cathode-ray-tube instruments, which now operate in a low-frequency range from 100 Hz to 10 kHz, and improvements in the design of surface and encircling probes. Most investigators have used low-frequency eddy currents to detect cracks extending outward from fastener holes. Similar applications are illustrated here. This paper also describes techniques used to detect cracks in a chemically milled skin splice and shear-lip cracks in multiple-layer aluminium structure. Shear-lip cracks change their orientation as they propagate through the structure, and because it is difficult to measure their length radiographically, low-frequency eddy current checks are used to determine crack length. Examples of these inspections are described in this paper.
Low-frequency eddy current inspection of aircraft structure
Niederfrequente Wirbelstrom-Pruefung von Flugzeug-Strukturen
Materials Evaluation ; 40 , 2 ; 206-210
1982
5 Seiten, 12 Bilder, 5 Quellen
Aufsatz (Zeitschrift)
Englisch
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