Photoelastic analysis of stresses and forces in steady cutting

Abstract

The results are presented of tests conducted at three different depths of cut and a velocity of 3.1 m/min on a work-hardening lead-alloy workpiece with a 10-degree-rake photoelastic tool. In addition to examining the behaviour of the chip-tool contact stresses, the paper considers the forces acting on the tool and distinguishes three areas: rake, nose, and flank. It evaluates the rake forces from the photoelastic results directly, estimates the nose forces by making certain assumptions with regard to the distribution of stresses, and neglects the stresses on the flank. The sum of the forces so obtained is then compared with the measured resultant cutting force; there is good agreement. There is a particularly significant observation which, contrary to previously published results, shows that the frictional stresses vary linearly in the so-called sticking zone and tend towards a constant only at relatively high depths of cut. This is discussed in relation to the general concept of plastic friction and the variation of the coefficient of friction on the rake face. The significance of the measured resultant coefficient of friction is also considered.