NDTnet 1998 Aug, Vol.3 No.8

Abstract

The dynamic Eddy Current with rotating probes is a recognized procedure for crack inspection of holes in aircraft structures made from aluminum. Typically, the inspection is carried out with single frequency equipment.

This lecture presents the results from the basic investigations concerning the crack analysis during inspection of bore holes on aircraft structures made from aluminum, using the multi-frequency eddy current technique. The realized technique allows for the dynamic eddy current inspection with rotating probes at 4 simultaneously employed frequency channels with high signal dynamics. As an addition to the conventional high inspection frequency, the low frequencies show advantages for the evaluation of crack lengths using the signal amplitudes, as well as for the detection of hidden defects.

The equipment used allows storage of the inspection results with high signal dynamics and offers the possibility to carry out an analysis and signal improvement (optimization) also retroactively on stored signals. The manually placed rotating probe with integrated position encoder together with the image-creating recording of the rivet hole signals allows simple on-line identification and evaluation of the defects with improved reliability and a reduced human factor compared to conventional single frequency techniques.

Results will be presented from the combined evaluation of the signal parameters at the different inspection frequencies to analyze the type of the defect in order to be able to classify the defect, as well as for the direct determination of the crack geometry (Reliable determination of crack length up to 2mm).

References:

1. Schiller, D., Meter, Th., Scheer, G. Detection and Analysis of Fatigue Cracks on Holes of Typical Aircraft Structures by Means of Multifreguency Eddy Current Inspection, 1997 A TA NDT Forum
2. Scheer, G., Tober G., Meter, Th. Rissanalyse an Flugzeugstrukturen mittels Wirbelstrom-Mehrfrequenztechnik Tagungsband der DGZfP Jahrestagung 1997, Dresden
3. Scheer, G., Hanemann, P., Kelb, W.Qualitätssicherung an rotationssymmetrischen Prüfoberflächen mit der Wirbelstrom C-Scan-Technik, Tagungsband der DACH Jahrestagung 1996, Lindau

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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