slidingcontact

Sliding contact refers to the interaction between two surfaces that glide past one another, as opposed to rolling contacts. It is a central topic in tribology, the study of friction, wear, and lubrication. In sliding contact, friction arises from interfacial interactions between asperities and from plowing and deformation in the contact zone. The friction force is often characterized by the coefficient of friction, which can depend on loading, sliding speed, temperature, lubrication, and surface conditions. Contact mechanics describe how load is distributed across micro-asperity contacts; models such as Hertzian contact theory and the Greenwood-Williamson approach give predictions for contact area and contact pressure. Wear results from material removal due to sliding, with mechanisms including adhesive wear, abrasive wear, fatigue wear, and fretting.

Lubrication plays a key role in reducing friction and wear. Depending on film thickness, sliding can occur under boundary, mixed, or hydrodynamic lubrication regimes. Lubricants (oils, greases) and solid lubricants (graphite, MoS2, h-BN) are used, along with surface engineering (hard coatings like DLC, TiN), microtexturing, and surface treatments to improve endurance and reduce stick-slip.

Applications include bearings, gears, seals, linear guides, brakes, and sliding electrical contacts in relays and switches, where arcing and contact resistance are considerations. In MEMS, sliding contact poses challenges due to high surface-to-volume ratios and stiction. Ongoing research focuses on predictive wear modelling, advanced coatings, and reliable design for extreme environments.