Surface characterisation by parameter-based technique, slicing method and PSD analysis

An effort has been made to compare the capability and results of three different surface roughness characterization methods (parameter based technique, slicing method and power spectral density analysis) through micro- and nano-scale surface roughness measurements and topography analyses of brake plungers. Although all of these surface characterization techniques are well known such a comparison has not been made yet. Measurements performed by stylus instrument and atomic force microscope concentrated on three types of surface finishing techniques (sand paper, cork wheel and rolling). For the sake of full transparency all the analyses have been performed by the authors’ homely developed computer codes. It was found that 3D surface roughness parameters widely used in practice do not shown any correlation with the surface finishing technique applied because of the inhomogenity of investigated surfaces. Contrary to this, based on parameters provided by the slicing method, such as width and orientation of asperities, ratio of major and minor axis of asperities, the different surface finishing techniques can be distinguished clearly. Fractal dimensions calculated from PSD analysis ranged from 2.22 to 2.55 with very small standard deviation. Additionally, it was found that the different machining technologies can not be properly separated, in every case, by the fractal dimension. In other words, fractal dimensions may be very similar even if they belong to two different surface finishing techniques.