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Identifying the drill position in composite and metal stacks using acoustic emission signal

: Ben-Hanan, Uri; Wertheim, Rafael; Drossel, Welf-Guntram; Stoll, Andrea; Ihlenfeldt, Steffen

Seliger, Günther ; College International pour L'Etude Scientifique des Techniques de Production, Paris:
10th Global Conference for Sustainable Manufacturing, GCSM 2012. Proceedings. CD-ROM : Towards Implementing Sustainable Manufacturing; 31st October - 02nd November 2012, Istanbul
Istanbul, 2012
ISBN: 978-605-63463-1-6
Global Conference on Sustainable Manufacturing (GCSM) <10, 2012, Istanbul>
Fraunhofer IWU ()
drilling; acoustic emission; composite material

The efficiency and performance of drilling holes in stacks made of carbon fiber-reinforced plastics (CFRP) and aluminum or titanium is a major topic in the aircraft industry. High performance drilling of holes in CFRP material requires a special type of drills and process parameters, while drilling holes in aluminum or titanium requires a different type of drills and process parameters. For this reason, drilling holes in a stack made of CFRP and metal with the same drill type using the same process parameters results in compromising in the quality of the holes, including burr formation, chip flow and surface quality.
It was shown that analyzing acoustic emission (AE) signal in real time can result in determining the time when the drill is close to exit the first layer and enter the second one or exit the stack. A special algorithm has been developed for finding the time when changes in the AE signal occur, indicating that the drill is entering or coming close to the end of a layer. The results showed the possibility to identify ahead of time when the drill is coming close to the end of the CFRP layer. The AE system will enable a change of machining conditions during drilling in order to improve efficiency and performance.