Introduction to tribology

The name tribology originated in England, and was first used in a report [1] presented to the Minister of State for Education and Science on November 23, 1965, and published in February 1966. The name comes from the Greek τρβειν (tribein: to rub) and λóγος (logos: speech, study or science ); thus tribology is the study or science of friction. More generally, tribology concerns the study of surfaces in contact and in relative motion, and thus encompasses lubrication, friction and wear of machine components. It should be noted that the notion of friction was defined in the remarkable studies [2] of Leonardo da Vinci, Guillaume Amontons and Charles Coulomb in the 19th century. xv ^e , xvi ^e and xviii ^e centuries. Friction involves many different phenomena, but can be simply defined as the action that tends to oppose the relative movement of two solids in contact. Similarly, wear, which can take many different forms, corresponds to the deterioration of surfaces during use.

Tribology is present in most human activities, and over the last fifty years its field has developed considerably. We can cite, among others, human walking with its adherence to the ground, the behavior of joints and the development of prostheses, the holding of objects in the hand, or even the holding of the fetus in the placenta, the road holding of car wheels that are paralyzed on icy or snowy days, downhill skiing, figure skating, the production of musical sounds by rubbing a bow against the taut strings of a violin, computer magnetic disk read heads, anti-scratch varnish on spectacle lenses, the shaping of materials... and even research into man's activities in prehistoric times. This list is by no means exhaustive.

To underline the importance of tribology, it should be noted that, in developed countries, losses due to friction and wear represent between 3.5 and 4% of GDP, and that in a modern car more than 25% of the engine's power output is lost to friction. Finally, according to a recent study by CETIM, 80% of mechanical part failures begin on the surface, which means that the surface is currently a real technological stumbling block.

Nomenclature

A

apparent contact area (m ² )

A _r

actual contact area (m ² )

C

radial clearance (m)

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