Analysis of fractal frictional contact in machining

Abstract

A model of the interfacial frictional conditions at the secondary shear zone in oblique cutting is under development. It has been suggested that the tool-chip interface consists of sticking and sliding microcontacts, each of which exhibit dynamic variations throughout the cut. The bond strength at the interface is difficult to determine because of the unpredictable characteristic of precipitation variability and the complex behaviour of the work material under severe cutting conditions. In this research the frictional interface is investigated on a microscopic scale to shed some light on these issues. Time-dependent cutting experiments illustrate the dynamic variations in sticking and sliding. It is also proved that the sticking and sliding areas exhibit fractal characteristics. Actual contact areas for sticking and sliding were calculated by using image analysis techniques. A relationship between the fractal dimension and the area of contact is noted. A mathematical model is proposed on the basis of the measured forces and calculated contact areas.