S. Yu. Tarasov

Shear Instability in the Subsurface Layer of a Material in Friction

The shear instability in subsurface layers of a material in friction has been investigated. As the friction surface is approached, several characteristic regions can be distinguished in the bulk of the metal: the region of plastic deformation and texturing (I), the region of severe fragmentation (II), the region of turbulent flow (III), and the region of laminar flow (IV). Regions I and II can be referred to as regions of conventional plastic deformation, whereas regions III and IV correspond to regions of the development of shear instability of the Kelvin-Helmholtz type at the shear boundary. The possibility of implementing this phenomenon within the hydrodynamic approach has been evaluated.

One-dimensional model of inhomogeneous shear in sliding

The paper briefly describes a one-dimensional dynamic model of plastic shear deformation in a material surface layer in sliding friction, giving grounds to the reduction of the problem dimension from 3D to 1D. A selection of simulation results is presented to illustrate the peculiarities of plastic deformation under the action of two competitive processes — work hardening and thermal softening due to frictional heating. Presented also are experimental data on which to base the conclusion on the possibility of surface layer flow similar to flow of a viscous fluid. To assess from the Reynolds number whether turbulization of the surface layer is feasible, simulation results are used.

Generation of shear bands in subsurface layers of metals in sliding

Nanostructuring of the surface of specimens during friction is investigated under the conditions of shear instability of the subsurface layers of the material due to the strong localization of deformation. It is demonstrated that the localization of deformation in the subsurface layers occurs in three stages. The structure of the localization zone is studied. The formation of a nanocrystalline material on the surface due to the shear instability is considered by analogy with the formation of the shear band. The formation of the nanocrystalline material can be responsible for the crossover from the mild wear to the adhesive wear in the absence of mechanisms providing structural adaptability.

General regularities of the microstructure formation during friction stir welding and sliding friction

A comparative metallographic analysis of the formation of the metal microstructure during sliding friction and friction stir welding is performed. It has been shown based on the example of a weld joint made of aluminum alloy fabricated by friction stir welding that the weld microstructure has all signs of the deformed layer of metal formed due to sliding friction, which is accompanied by the seizure of conjugated surfaces.

Subsurface deformation in copper single crystals during reciprocal sliding

AbstractThe deformation surface pattern generated on the faces of a copper single crystal loaded by a compression force and simultaneously sliding over the counterbody surface has been studied. The samples under study are copper single crystals with different orientations of the compression axis, which are grown by the Bridgman method. The study of the friction of single crystals with the orientations [110] and [

Effect of friction stir welding parameters on defect formation

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Application of fractals to the analysis of friction processes

11] has revealed that the shear systems whose action manifests itself on side faces are localized near the friction zones. The density of traces formed in this process decreases with the distance from the butt-end. The [110] single crystal has regions of higher density near the butt-end. Different patterns of shear on the side faces of [