Written by Martin Ahner
Tribology describes°"the science and technology of interacting surfaces in relative motion".°°
Tribology means literally ‘the study of friction’. According to DIN 50 232, it describes "the science and technology of interacting surfaces in relative motion". But what does that mean exactly?
Let's take a look at the°tribosystem. Here you see which typical stresses can act on elements and how loss parameters vary depending on the properties of an element. Friction and wear acting on the components are specified as loss factors.°°
Since lubrication is used to combat friction and wear, friction, wear and lubrication are all sub-fields of tribology
Friction occurs when e.g. two moving objects come into contact at their material boundaries. This creates an interaction that counteracts the relative motion of the bodies.°°
Friction can occur between two or more separate bodies or within a body. The former is known as external friction. Friction within bodies is referred to as internal friction.
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Wear°refers to progressive loss of material due to mechanical causes.°Wear occurs when components rub against each other for too long or with too much force because e.g. the lubricating film is no longer sufficient to keep the components apart. Wear refers to the progressive loss of material caused by such mechanical factors.°
Obviously, wear is generally undesirable. In a worst-case scenario, wear can even lead to failure. You can tell whether parts are wearing out by observing changes in the material surface.
Do you have any idea what lubrication is used for? Check the lubricant to find out.°
Lubrication methods can vary from dry lubrication to full lubrication.°
Lubrication is used as a separating agent between two surfaces that are in relative motion to each other. This minimises or eliminates friction and wear, thereby maximising the service life of the components. A secondary function of lubricants is to remove heat and wear particles.
Lubricants exist in all physical states. One type may be more suitable than another, depending on the application, with liquid lubricants i.e. lubricating oils being the most common. These include mineral oils, vegetable oils, animal oils and synthetic oils.°
Advantages of the two types of lubricating oil°
Advantages of mineral oils°
▪ Universally applicable°
▪ Less toxic°
▪ Better miscibility°
▪ Higher availability°
▪ Better compatibility with materials°
Advantages of synthetic oils°
▪°3-5 times°longer service life°
▪ Higher temperature spectrum°
▪°Flame°retardant°
▪ Better flow characteristics°
▪ Lower volatility°
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Mineral oils are obtained from crude oils through selective distillation and refining and are universally applicable. Synthetic oils, on the other hand, last three to five times longer than mineral oils.°
Lubricating greases are solid or semi-solid lubricants. They consist of a liquid°oil-based lubricant, a thickening agent and other additives.°They°provide°a°barrier°against°water°and°foreign°particles.
The choice of an appropriate lubricant depends on the specific application and operating conditions. Decisive influencing factors include load, speed, temperature and ambient conditions.°
The physical state used depends on the application:°
Liquid lubricants
Liquid lubricants are used in numerous technical applications, including:°
Engine oils°
Machine lubrication°
Transmissions°
Circulation systems°
Hydraulic systems°
Textile machinery°
Compressors°
Lubrifiants solides et semi-solides
Ces lubrifiants conviennent particulièrement aux :
machines à faible vitesse
roulements, articulations et transmissions
applications sous vide
environnements agressifs
Lubrifiants gazeux
La lubrification gazeuse est utilisée pour les :
machines soumises à des charges faibles
systèmes à haute vitesse (par ex. centrifugeuses)
Le choix du lubrifiant approprié contribue de manière significative à la fiabilité, à la durée de vie et à l’efficacité des systèmes techniques.
La tribologie désigne la science du frottement, de l’usure et de la lubrification. Ces trois domaines constituent les principaux sous-domaines de la tribologie et sont directement liés au fonctionnement et à la durée de vie des composants techniques.
L’usure peut se produire lorsque des corps en contact frottent les uns contre les autres. Pour réduire les frottements et l’usure des matériaux qui en résulte, on utilise des lubrifiants. Une lubrification adéquate permet de séparer partiellement ou totalement les surfaces en contact.
En fonction des besoins, les lubrifiants sont utilisés sous différentes formes : gazeuse, liquide ou solide.