Indentation and scratching of iron by a rotating tool-a molecular dynamics study

Abstract

When abrasive particles interact with a surface, besides translational center-of-mass motion also rotational motion of the abrasive may be involved. We perform molecular dynamics simulations of the influence of the rotational motion in a model scenario, where both translational and rotational velocities are controlled. We find that for angular velocities corresponding to slip-free rolling, the influence of rotation is small and shows up as a decrease of hardness and of friction. The effect is somewhat more pronounced for rolling motion (rotation axis parallel to surface) than for drilling motion (rotation axis perpendicular to surface). Pile-up structures are unaffected. Only if rotational speeds strongly exceed the rolling-without-slip limit, strong effects of the rotational speed are observed: the machined material amorphizes rather than to develop dislocation plasticity, the groove develops oscillatory patterns, and the material hardness is strongly reduced.