Determining mechanical characteristics of material resistance to deformation in machining

Abstract

This paper analyses experimental results and different hypotheses about the resistance of the machined material to plastic deformation in machining. It is necessary to take into account that strain rate and temperature affects the mechanical properties of the material. It is useful to describe the regularities of material resistance to plastic deformation with differential equations, determining a dependence of the specific deformation work on deformation. For machining processes, the correlations between yield point and deformation or rather flow curves are analytically deduced from the differentiation of the specific deformation work. It has been found out that the flow curves are vaulted for the adiabatic conditions of deformation in the chip forming area and the accumulation zones near the cutting edge. The yield point here reaches its maximum for deformations that are usually lower than the true final shear of the material penetrating through the chip forming area. It is suggested to take these maximum values of the yield point as mechanical properties of the material to be machined. The main goal of the theoretical and experimental investigations presented in this paper is to establish the analytical dependence of the specific deformation work and therefore also of yield point and specific tangential forces on deformation, taking account of the effect of temperature on yield point. The main advantages of applying the specific deformation work is not only its direct relation to deformation temperature but also the possibility of experimentally determining this work through specific tangential forces and true final shear. In this way it is possible to establish how deformation temperature affects yield point by means of empirical constants.