Analysis of cutting-force signals by time-frequency localization methods

In this work the force signal of a metal cutting process were analyzed by continuous wavelets and Hilbert-Huang Transformation (HHT). The main purpose was to reveal the dominant frequencies and the frequency-time functions of the vibrating sub-systems in the cutting process. Three dominating vibration modes were detected with strongly fluctuating measured frequency values confined in a relatively narrow frequency band. Here we show that this fluctuation has not only numeric but physical reasons, and one of these reasons is probably the coupling between the vibration modes. It turned out that the wavelet analysis method is capable of tracing fast varying frequencies of the signal with values close to each other by the proper choice of the central frequency parameter of the mother wavelet. In comparison with the HHT the wavelet method showed much more robust in this case.