A statistical approach to acoustic monitoring of laser welding

Abstract

Acoustic emission at frequencies between 20 Hz and 20 kHz during laser welding of steel contains important diagnostic information related to weld morphology, depth of penetration and the heat-affected zone. We have recorded acoustic spectra under a variety of welding conditions with mild and galvanized steel sheet and find that a well-defined spectrum is obtained under conditions that lead to an optimization of these weld characteristics. A statistical approach is developed which yields a predictive measure of weld quality, based on a comparison between real-time acoustic spectra, and that obtained under optimized conditions. This technique is applied to an analysis of bead on plate, lap and butt laser welds in mild and galvanized steel.

In-process sensing in selective laser melting (SLM) additive manufacturing

“…Acoustic signature monitoring Acoustic monitoring is widely practiced in laser welding processes due to the simplicity and low cost of acoustic sensors [41,42,50,51]. The basic process requires comparison of the acoustic signature of a "known good" standard with that from welds to be evaluated and is described in ASTM E749.…”

“…The basic process requires comparison of the acoustic signature of a "known good" standard with that from welds to be evaluated and is described in ASTM E749. While the intensity of a weld acoustic signature has not been shown to be a strong indicator of weld quality [50], the frequency response has been correlated to several weld quality metrics and process phenomena, including keyhole formation, plasma formation, and crack propagation [42]. Acoustic monitoring has been discussed as a potential monitoring technology for laser additive processes [42], but to date there have been no published studies of this monitoring approach applied to the SLM process.…”

Optical Methods for On-line Quality Assurance of Welding Processes in Nuclear Steam Generators

“…It has been proved that the arc and laser welding produces acoustic emission in the audible and ultrasonic ranges that can be correlated with the onset of defects (Wang & Zhao, 2001). As with the previous technique, it is however difficult to discriminate among different defects, although a statistical analysis applied to the spectra of sound has demonstrated some success in predicting the weld quality (Gu & Duley, 1996). Thermography is also a powerful monitoring technique.…”

In-situ acoustic signature monitoring in additive manufacturing processes

“…High energy acoustic emissions are often associated with events such as crack initiation and propagation [8]. Weld quality during laser welding under different conditions (overheated, full penetration, and non/partial penetration) has been previously correlated with the acoustic power spectrum standard deviation in low frequency bands (20 Hz-20 kHz) [9].…”