Modeling of friction in the presence of cooling lubricants

Abstract

High pressure cooling lubricant (CL) supply is associated with high electrical energy consumption. With a reduced CL-supply the energy efficiency of cutting processes can be increased while maintaining the material removal rate and surface quality of the workpiece. In order to design adapted CL strategies, basic knowledge of the fundamental mechanisms of CL is necessary. However, due to high normal stresses and small contact areas of the chip and the cutting wedge, the analysis of the mechanisms of CL is challenging. In this paper high-speed video recordings and force measurements are used for in-situ analysis to model the velocity-dependent effects of CL on friction at the tool-chip considering CL. Different rake angles γ = [-6 °, 0 °, +6 °] are being set in order to investigate a wide variety of relative velocities between the tool and the chip. Using local normal- and tangential stresses as well as local relative velocities, which are measured using Digital Particle Image Velocimetry (DPIV), the velocity depended effects are investigated. The interaction of the tool and chip on the rake face is modeled using local force coefficients µ* as the quotient of the local tangential and normal stresses in dependency of the relative velocity and the CL pressure p.