Lubrication

Lubrication is to reduce friction and wear between the two machine elements ( " friction partners " ), which move relative to each other. This is done through the use of a suitable lubricant and method of lubrication in tribology.

Lubrication can be divided similarly to friction:

Boundary layer lubrication

The lubricant penetrates into the solid state, it forms a reaction layer. The load carried by the asperities of the friction partners.

Mixed lubrication

The load is absorbed by the lubricant film and partly by the contacting asperities on the one part.

Full lubrication

The load is completely absorbed by the lubricant. The contact surfaces are separated. The full lubrication can be further subdivided into:

Hydrostatic lubrication (air: aerostatic lubrication)

The separation of the contact surfaces is done by pumping the lubricant in the lubrication gap. This form of lubrication is technically very complex and structurally very demanding. The result is a nearly smooth shift, since the hydrostatic lubrication immediately a fluid friction arises, however, come in these processes, due to the demanding production, higher costs materialize.

Hydrodynamic lubrication

The lubricant is funded by the relative movement of the contact surfaces to each other in the narrowing gap lubrication. The pressure in the lubricant is so high that the contact surfaces are withdrawn from each other. However, often occur mixed friction and / or stick-slip effects on ( stick-slip ). The result is a low sliding speed.

Elastohydrodynamic lubrication

This form of lubrication occurs in the contact of highly stressed moving rollers, for example in gears and bearings. The theory of elastohydro ( EHD theory ) takes into account the basic hydrodynamic equations and the elastic deformation of the contacting bodies. Characteristic of the EHD lubrication is a narrowing of the lubricating gap at the end of the contact zone. The EHD theory provides the basis for calculating the lubrication influence on gear damage such as pitting, galling or micro-pitting.