Surface Roughness Anisotropy and Anisotropic Friction during Plastic Deformation

Abstract

The isotropy of friction, usually assumed when considering the issues of classical mechanics of bodies and solving engineering problems, is essentially a special case of anisotropic friction, which dominates the nature of friction. This is explained by the objectively existing difference in the properties of the self-organizing medium of the frictional interaction of bodies in different directions. Among these properties are the anisotropy of the physical and mechanical characteristics of the material and its wear, the kinematics of sliding in a friction pair, and the structure of the near-surface layer. An equally important property of the medium generating anisotropic friction is the anisotropy of the roughness of the contacting surfaces. A large number of papers have been devoted to the study of anisotropic friction. They study the friction characteristics of specific materials and friction pairs, the wear resistance of surfaces, models of the dynamics of bodies on a rough surface. Most often these works are experimental in nature. In this article, the influence of roughness anisotropy on anisotropic friction in the processes of plastic deformation of metals is considered at the phenomenological level. A deterministic model of anisotropic (orthotropic) friction is proposed, which makes it possible to determine the magnitude of the friction force and the direction of movement of the deformable metal on the contact surface by the ratio to the vector of the external shear force, depending on the quantitative and qualitative parameters of the roughness of the tool surface. The roughness of the contacting surfaces in the workpiece-tool friction pair is approximated by a set of ordered wedge-shaped protrusions. Contact interaction is considered as the process of deformation of the wedge-shaped protrusions of the workpiece by absolutely rigid wedge-shaped protrusions of the tool. In the process of plastic deformation, an asymptotic approximation of the roughness of the surface of the workpiece to the roughness of the surface of the tool occurs with the full filling of the hollows of the tool irregularities with a plastic wave of the metal of the workpiece.