Investigating Shearing, Ploughing, and Particle Fracture Forces in Turning of Low Percent Reinforcement Al/B4C Metal Matrix Composites

Abstract

This paper presents a study on forces generated due to different mechanisms in turning low reinforcement Al/B4C composites. Forces due to shearing, ploughing and particle fracture/debonding mechanisms have been determined based on experimental data and latest models from literature. These mechanisms form the basis of the different kinds of forces generated during machining of metal matrix composites. This study analyses force behaviour due to the above-mentioned mechanisms under varying machining conditions and material compositions. Primary findings establish the relative dominance of shearing mechanism over ploughing and particle fracture under all conditions. Secondly, ploughing and particle fracture forces' estimates respond in tune with the increasing particle reinforcement fractions in the metal matrix compositions. However, shearing forces do not necessarily follow such trends. It is found that chip thickness increments with rising feed rates are better indicators of augmentation in composite reinforcement levels. Thirdly, cutting forces and material flow strengths may exhibit contradictory trends under exactly same machining conditions. Fourthly, flow stresses are found to be more strain rate sensitive for low reinforcement composites. Lower reinforcement composites are relatively less ductile at low cutting speeds and more ductile with varying feeds and depths of cut. These results establish better machinability of metal matrix composites having lesser particulate inclusions at higher cutting speeds and feed rates. Composites reinforced with higher percentage of boron carbide particles do not necessarily generate higher shearing forces, although increased tool wear can certainly be expected due to the higher ploughing and particle fracture/debonding forces.