Influence of free surface environment on the shear zone in metal cutting : P. L. Barlow, Preprint Inst. Mech. Engrs. London, No. P 26/67

Abstract

Rehbinder effect on ductile materials is observed when surfactant is applied on the material surface, which reduces the strength of material due to reduction in surface energy. Application of Rehbinder effect in conventional machining of ductile materials was studied previously which resulted in significant reduction in chip thickness and cutting forces. In this paper, the Rehbinder effect on ultraprecision microcutting of ductile materials is presented. Microcutting experiments were conducted on annealed copper, hardened copper, aluminium alloys AA-6061-T6 and RSA-6061 of different grain sizes at varying uncut chip thickness and cutting speed. Permanent metal marker ink was used as a surfactant to induce Rehbinder effect. As a result, cutting and thrust forces were reduced by 50% for pure copper whereas a 30% reduction was observed on aluminium alloys along with a reduction in chip thickness for the sections where ink was applied. It is also evident that the Rehbinder effect contributes towards an improvement in surface roughness. The underlying mechanism responsible for the reduction in cutting forces and chip thickness is explained in relation to a dislocation density model and explored further by a finite element method simulation. Positive results of Rehbinder effect on microcutting demand further studies to characterise the effect on other surfactant-material pairs for the applications in ultraprecision machining.