Acoustic Emission Characteristics of Galling Behavior from Dry Scratch Tests at Slow Sliding Speed

Galling wear, a severe form of wear, is a known problem in sheet metal forming. As the wear state is not directly observable in closed tribosystems, such as in industrial sheet metal forming processes, indirect tool wear monitoring techniques for inferring the wear state of the tool from suitable signal characteristics are the subject of intense research. The analysis of acoustic emissions is a promising technique for tool condition monitoring. This research has explored feature selection using t-tests, linear regression models, and cluster analysis of the data. This analysis has been conducted both with and without the inclusion of control variables, friction, and roughness to discriminate between the behavior of the acoustic emissions during different stages of galling wear. Scratch testing at slow sliding speed (1 mm/s) has been used to produce the galling wear between a tool steel indenter and aluminum sheet at 10 N applied load, for which the acoustic emissions were recorded. The bursts of the acoustic emission signal were processed and investigated to observe how the bursts changed with increasing galling damage (increasing material removal and transfer). Novel parameters in the field of galling wear have been identified, and novel models for observing the change in galling wear have been identified, thus furthering the development of acoustic emissions analysis as a non-invasive condition monitoring system, particularly for sheet metal forming processes.