Automatic scanning with multi-frequency eddy current on multilayered structures
2001 (English)In: Insight (Northampton), ISSN 1354-2575, Vol. 43, no 3, 163-166 p.Article in journal (Refereed) Published
Eddy current testing is a frequently used NDT method at Saab/CSm but until recently only single frequency testing has bern used. Through the participation of Saab/CSM in a Brite-Euram project, 'CANDIA', it has been possible for Its to learn about multi-frequency testing and also to combine it with a flexible scanner developed in a preceding Brite-Euram project. The purpose of our work was to increase both testing speed and sensitivity ht: using multi-frequency eddy current testing, combined with a scanning system for corrosion detection in multi-layered structures. The wing of the Saab 2000 aircraft was one specific example for which several samples were manufactured with both artificial (chemically etched) corrosion of various severity and cracks. After optimising single frequencies, multi-frequency testing was adopted Using the previously determined optimal single frequency as a start, frequency combinations were determined to give increased detectability for the different structures and defects. The influence of different disturbing signals, for example signals from rivets, thickness variations, noise, and how to reduce them using the multi-frequency technique, was studied. A scanner was adapted to make it compatible with the eddy current instrument, resulting in a complete scanning system. During the project, tests were also made in 'field' conditions to evaluate the system. Components with real corrosion have also been tested with promising results. The possibility to produce scans from the mixed multi-frequency signals was very fruitful. The goals to increase testing speed and sensitivity have been reached. The combination of an advanced multi-frequency instrument with a scanning system will result in faster inspections and yield better results than could be achieved previously at Saab and CSM. These developments will increase the use of eddy current inspections.
Place, publisher, year, edition, pages
2001. Vol. 43, no 3, 163-166 p.
IdentifiersURN: urn:nbn:se:liu:diva-49341OAI: oai:DiVA.org:liu-49341DiVA: diva2:270237