The effects of progressive wear on the frequency characteristic of acoustic emission acquired during face milling

Acoustic emission (AE) provides a non-intrusive means of monitoring insert flank wear in face milling. Progressive wear tests of carbide inserts in eight-point milling of annealed En24 steel were instrumented with piezoelectric AE transducers and a non-contact optical interferometer, from which AE frequency information could be extracted. Mean AE frequency was found generally to decrease with wear in agreement with other published studies. Tool indexed measurements enabled the time evolution of the frequency content to be studied on the timescale of a single pass of the insert. The results may be explained by a simple analytical model for AE frequency associated with plastic deformation. The observed AE decay time constants following insert entry decreased with cutting speed, consistent with thermal models of the cutting process. Whereas the results of this study alone would not constitute an independent means of tool wear monitoring, they could provide a diagnosis of tool wear when supplemented with other AE measures and with knowledge of the specific cutting process. © IMechE 2005.