Fractal dimension in tribology – an overview

Abstract

Friction and wear in tribological systems are phenomena that can be interpreted on a macroscopic scale. The emergence of micro and nano-sized systems requires the treatment of tribological phenomena through the concept of fractals. Thus, to perceive the tribological phenomena occurring in a macro-system, it is fundamental to think about them at the micro-scale and nano-scale, that center, for case, on the level of hardness and atomic composition. This article realizes a survey of the main concepts about treating the tribological issues in terms of fractals. It is clear that the continuous change of the micro and nano topography of the friction surfaces during the dynamic functioning of various mechanisms and the tribological processes taking place can be treated using the fractals and chaos theory. To this end, it is concluded that all the existing theories in tribology should be adapted to include fractal dimension and fractal roughness.

Evaluation of the Feasibility of the Prediction of the Surface Morphologiesof AWJ-Milled Pockets by Statistical Methods Based on Multiple Roughness Indicators

“…Given that these parameters only provide information about the amplitude of the roughness but not regarding its complexity or anisotropy, such as parameters related to direction or orientation of surface roughness, the effect of a machining process on the functionality of a surface cannot be totally explained by the height parameters [56]. For that reason, advanced methods for surface roughness profile analysis, such as fractal analysis, can provide a deeper insight into the nature of the surfaces under different conditions and also lead to the establishment of correlations between them and friction and wear properties [57,58]. For example, the analysis of the fractal characteristics of surfaces can provide details about the lubrication characteristics [59], such as the resistance to the flow or lubrication film thickness [30].…”