Fractal characteristics of 3D surface topography in laser machining

Abstract

The measurement of the profile data from carbon steel surface machined by laser machining with the white light interferometer is discussed in this paper, the research of the surface topography characteristics of laser machining is based on fractal geometry analysis, and the Box-counting method is used for 3D fractal dimension calculation of the laser machining surface. The results indicate that a universal fractal dimension beyond scale range is unattainable, and only when the scale r is less than the maximum height of profile Ry, the performance of the fractal characteristics on the laser machining surface is present. When the same laser machining surface is characterized, the Ra of same scale fluctuates greatly along the thickness direction, and the fractal dimension Db can be used to stably characterize the complexity of the whole surface topography. The 3D surface fractal dimension Db is sensitive to the machining surface defects, once the Db becomes smaller, deep cracks and pronounced defects are exhibited in machining surface. In this paper, the characteristic analysis of the laser machining 3D surface is obtained by characterizing the micro-structured surface complexity using the fractal dimension, which is aided by the roughness to evaluate the profile height characteristics of laser machining surface. This study indicates that the Box-counting fractal analysis is an effective method to evaluate laser machining surface comprehensively.