Fractal dimension analysis of machined surface depending on coated tool wear

The surface topography is characterized by parameters, such as a centerline average roughness Ra and a maximum height roughness Rmax. While such parameters are useful to define the quality of surface, they are not sufficiently descriptive characteristics of surface. The reason is that the surface topography is nonstationary and multiscaled. It suggests that fractal dimension which can describe surface roughness invariant with length scale than conventional roughness parameters should be used in characterizing surface topography. Up to now, many fractal models have been developed and applied for the elastic-plastic contact, tribology, surface text and so on. However, no discussion has been made on the characteristics of tool wear. In this paper, the relation between surface roughness and fractal dimension depending on coated tool wear using a generalized formula is identified. The work-piece material used in the experiments was high-hardened die steel and machined surface were obtained with high-speed cutting conditions. The new fractal analysis is an effective tool for in-process monitoring of tool wear using the fractal characteristics of machined surfaces.