Theoretical prediction of shearing stress together with cutting forces in micro drilling

Abstract

Cutting force coefficients in existing micro drilling force models were usually identified by experimental procedures, which did not explicitly consider the influence of the rounded cutting edge. This article presents a new micro drilling force model by establishing a method to theoretically identify the cutting force coefficients. Shearing stress, which is a key item required to analytically calculate the cutting force coefficients, is theoretically modeled and solved based on the basic principle of Johnson–Cook constitutive model. Effect of the rounded cutting edge on rake angle and variation of cutting edge’s velocity along radial direction are taken into account to establish the model. Influences of the drill’s primary and chisel edges are separately considered in the model formulation. It is found that shearing stress and effective rake angle are strongly dependent on the radial position of the concerned point on cutting edge, and thus, the main advantage of this work lies in that cutting force coefficients are mathematically determined as cutting edge position-dependent values to characterize the actual cutting behavior of micro drilling. Experimental validation proves that the proposed micro drilling force model has high prediction accuracy under varying conditions.