Detection of tool breakage during hard turning through acoustic emission at low removal rates

The paper deals with a new method for the detection and prediction of the catastrophic tool failure (CTF) of ceramic inserts through an acoustic emission (AE) technique and associated chip formation analysis during the hard turning of bearing steel 100Cr6. The capability of different AE sensors with respect to the different processes in the cutting zone during hard turning is discussed as an initial study. Then a new concept of process monitoring is suggested based on the application of two sensors and rationing of chosen parameters such as AErms, AEstrength and AEabsolute energy. The specific character of the formed chip is associated with raw AE signals. Conventional data processing of AE signals does not enable the different phases of tool wear to be clearly recognised or the prediction of CTF, while the new suggested concept does. This concept is based on the rationing of AE features recorded in different frequency ranges in connection with the different processes in the cutting zone during chip separation.