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Wear mechanisms and friction in metals can be investigated by the analysis of the unit event represented by the interaction of a hard particle or asperity with a softer surface. Effective friction is the result of the interaction of many such asperities which constitute the roughness of the harder of the solid surfaces. Three types of plastic deformation at the metal surface can be identified: ploughing,...
Micro-electromechanical systems (MEMS) is a rapidly growing interdisciplinary technology dealing with the design and manufacture of miniaturised machines or moving (or micro) mechanical assemblies (MMAs) with major dimensions at the scale of tens, to perhaps hundreds, of microns. Because they depend on the cube of a representative dimension, component masses and inertia rapidly become small as size...
As a result of its widespread and pervasive economic consequences wear, the almost inevitable companion of friction, has been the subject of much scientific and empirical investigation; the literature is rich with `wear equations' so that, on occasion, the practitioner can seem to have too much information rather than too little. Some guidance and reconciliation between analytical and computational...
When a hard rough surface slides repeatedly on a softer component a system of protective residual stresses may be developed in the near-surface layers of the weaker material which enable loads sufficiently large to cause plastic deformation in the early cycles of loading to be accommodated purely elastically in the later stages of the loading history. This is the process known as shakedown and limits...
A large class of tribological contacts involve two components, each carrying finite roughness, sliding over one another for many repeated cycles of operation. Although the initial contact may be plastic the steady state situation is one of elastic stress fields in each consistent with the presence of a low shear strength boundary film on one or both of the surfaces. In order to relate the overall...
A mechanism of metallic wear is proposed in which laminar wear debris is generated by a process of plastic ratchetting brought about by repeated pummelling of the softer wearing surface by the asperities on a harder mating surface. Wear rate is found to be approximately proportional to (load) and an increasing function of a single non-dimensional parameter termed the plasticity index for repeated...
The friction and wear caused by a single hard asperity in repeated sliding contact have been studied in our earlier publications. This paper outlines a method of combining all the contacts that occur between a soft surface and the asperities on a randomly rough hard surface and leads to predictions of the overall coefficient of friction and the wear rate of the soft surface. The hard asperities are...
Most work on the mechanics of shakedown has been on half-spaces which have strength properties invariant with depth. In practice, however, materials for tribological applications are often surface engineered to impart a higher hardness near the surface. In some situations, such as wheels on railway tracks, considerable plastic flow is observed near the surface and, as a result, the initial hardness...
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