Abstract: The paper presents a new method of describing signal complexity using fractal dimension according to the change characteristic of the cutting force in the drilling process. From the point of view of engineering application, it introduces the algorithm of box dimension and information dimension for discrete time series and reveals the inherence relation between the fractal dimension and signal complexity by calculating the fractal dimensions of three simulating signals. It also researches into the changing rules of the fractal dimension in the whole course of tool wear through experiments. The results show that along with the increase of tool wear, the fractal dimension of the cutting force signal assumes the falling trend, and the tool wear monitoring can be realized effectively by using the fractal dimensions as the feature of the cutting force signal.

Key words: tool wear, fractal, box dimension, information dimension