Nature of the deformation and flow of metals at and near the interface during abrasion, and its relation to the friction

Abstract

The direction of flow of various metals (Pb, Al, Au, Ag, 62.1 At. % Au–Ag alloy, Cu, Ni, 25.7 At. % Ni–Cu, Mo, W, U, Ti, Mg, and Zn) past the faces of a ploughing Vickers diamond pyramid of dihedral angle 136° is shown in ploughing (a) parallel to the side of the initial square indentation, (b) parallel to the diagonal, (c) in and intermediate asymmetrical direction. In all these cases, with this obtuse indenter, the metal flow at the interface is close to the direction lying in a plane through the ploughing direction, normal to the surface of the specimen. Approximate theoretical expressions are derived for the friction coefficient µ for such conditions.

The form of the flow past an indenter is also indicated by observations on the ploughing of macroscopic metal pyramids and cones in Plasticene built from superposed layers of different colours.

Observations are also made on the widths of grooves ploughed by the diamond on various metals, compared with the width of the static indentation. These are considered in relation to the theoretical expressions and the factors which may affect the groove development.