There are a number of sources of acoustic emission generated during laser processing. Due to the “silent” manner in which optical energy is transmitted to the reaction zone most of these signals give information on the “health” of the process. Some of these signals are transmitted through the surrounding atmosphere, it is these signals which are the concern of this paper. They fall into three classes those generated by pressure waves emanating from the work piece, those from impacting jets and those generated on an elastic by reflected, remodulated laser power from the interaction zone. These three signal sources lead to two different in-process monitoring devices which are discussed in this paper - the Acoustic Emission Nozzle (AEN) and the Acoustic Mirror (AM). Both are non contact devices and totally non intrusive into the process. The potential application of the AEN as a weld monitor is described.

Topics
Acoustic phenomena, Laser materials processing
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1993
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