Real-time acoustic emission monitoring for surface damage in hard machining

Hard machining is a competitive finishing process with substantial benefits in manufacturing precision mechanical components. However, hard machining applications have been remaining slow due to the existence of surface damage such as white layer. The process-induced white layer may have detrimental effect on component life. However, the white layer on a machined component surface could be found only after machining. This post-process scenario imposes a great potential danger to subsequent product performance such as fatigue life. Therefore, real-time monitoring of white layer formation during hard machining has significant economical and durability importance. In this study, a real-time acoustic emission (AE) monitoring system was developed to investigate the sensitivity of a broad AE signal parameters including RMS, frequency, amplitude, and count rate to white layer and corresponding surface finish and tool wear. The experimental results show that AE RMS, frequency, and count rate have good correlation with white layer formation and, thus, may be used to monitor surface integrity factors. The findings provide fundamental information to develop practical on-line AE monitoring system for surface integrity in hard machining.