Frictional forces and their effects have long preoccupied mankind. There are numerous indications that our ancestors were already looking for methods to utilise the power of friction very early on. The ignition of fire, levers and stone axes as the first simple tools: everything is based on friction. The first machines, fiddle drills and potter's wheels, which were created 5,000 to 6,000 years ago, are also based on the principle of friction. The use of rollers and carriages to reduce friction when transporting heavy loads are well-known tribological examples. The earliest documents on the use of wheels to reduce friction date back to 650 BC. Today's rolling bearing has its origins in the so-called "rolling elements", which were already used in Ancient Egypt to build pyramids and made it possible to transport blocks of stone weighing several tonnes over long distances. However, Leonardo da Vinci (1452-1519) was the first person to begin a targeted scientific examination of the theory of friction much later, when he carried out the first investigations into friction on horizontal and inclined planes and wear on plain bearings. Since 1966, the technical term "tribology", which is derived from the Greek terms tribein = to rub and logia = teaching, has been more commonly used in specialist circles and was first mentioned in connection with the Jost Report, an investigation into wear damage commissioned by the British government. Since then, the terms tribology and tribological systems have been used in connection with friction, wear and lubrication.
Friction and lubrication have always belonged together: This is also proven by numerous early finds. The Chinese were already looking for effective lubricants to reduce friction and initially used water as a lubricant, later a mixture of vegetable oils and lead. The ancient Egyptians were also aware of the friction-reducing effect of lubricants and reduced the number of train drivers required by 50 % by lubricating the underside of the pharaoh's throne. They also lubricated their chariots with animal fats or a combination of olive oil and lime flour. However, lubricants only experienced their real breakthrough with the start of the industrial revolution, when increasing industrial development led to a rise in demand for the volume and quality of lubricants. Vegetable and animal oils were gradually replaced by mineral oils, which were obtained from crude oil, shale and coal by distillation and refining.
Leonardo da Vinci investigated the coefficient of static friction on the inclined plane and determined its value as f = 1/4. The first and second laws of friction, the so-called laws of dry friction, can also be traced back to him. These state that the frictional force is proportional to the normal force and independent of the apparent contact area and depends not only on adhesion but also on abrasion. Abrasion has a particularly great influence if the rougher friction partner is made of a harder material or if abrasion in the form of hard oxidised metal particles is present at the joint. In 1490, he almost exclusively replaced the flexible connection between two parts of the rolling bearing with balls, thus generating considerably less friction. He discovered that friction is reduced if the balls do not touch each other and subsequently developed separating elements that enabled free ball movement.
The French physicist and governor of Lille Guillaume Amontons (1663-1705) carried out research in the field of mixed friction. He discovered that the frictional force depends on the normal force and recognised surface roughness as the cause of friction. For him, frictional forces were based on mechanical-geometric interlocking of unevenness. The form fit of the micro-elevations inhibits the relative movement so that a frictional force occurs in the opposite direction to the direction of movement. Amontons defined the coefficient of friction as f = 1/3 and presented the laws of tribology discovered by Leonardo da Vinci to the Académie Royale in Paris in 1699.
The natural philosopher John Theophilius Desaguliers (1683-1744) developed an explanatory model of friction in which he attributed frictional forces to the influence of cohesion or adhesion. He also established that a higher frictional force occurs with better polished surfaces and that two well-polished lead bodies pressed firmly together can only be separated again by very great force. He attributed the friction that occurs to the influence of cohesion and adhesion, but was not yet able to relate this idea to the quantitative tribological laws of friction.
The English natural scientist and civil servant Sir Isaac Newton (1643-1727) defined the material parameter of dynamic viscosity: the adhesion theory, or assumption of a molecular-mechanical cause of friction, emerged, which had already been assumed by Desaguliers as a partial cause of friction. These adhesion theories were later significantly expanded by Bowden and Tabor in the 1920s and 1930s.
The Swiss mathematician and physicist Leonhard Euler (1707-1783) investigated friction on inclined planes. He discovered that static friction is about twice as high as dynamic friction and introduced the coefficient of friction "µ", which is now known as "f" in tribology. The coefficient of friction for metals is measured on polished surfaces in order to largely rule out mechanical interlocking. The decisive factors are the adhesion and cohesion forces between the two materials.
The French physicist Charles Augustin de Coulomb (1736-1806) further developed Amonton's fundamental ideas regarding surface roughness and mixed friction and focussed on the correlation between the force to be applied horizontally and the proportion of weight. According to Coulomb, the coefficient of friction of a surface does not depend on the load. This means that the frictional force is proportional to the weight and independent of the surface, as it is only a function of the average angle of inclination of the roughness. In his opinion, the flatter the surface, the lower the friction should be: a theory that is only partially correct according to current research.
Today's tribology began after the First World War, when high loads, speed and temperatures characterised increasing stress on friction pairs, making it necessary to physically adapt lubricants. Pour point and viscosity index improvers, oxidation and corrosion inhibitors were created, and at the same time the development of synthetic oils began. The use of metal-ceramics is becoming increasingly important: metal-ceramic surfaces and ceramic cutting materials ensure greater efficiency and a longer service life for industrial bearings and gears. Thanks to modern and innovative oil additives such as DuraGear® or PowerShot® (link to landing page), the surfaces of bearings, gearboxes and combustion engines can even be subsequently upgraded to metal-ceramic surfaces during the friction process.
You need to load content from hCaptcha to submit the form. Please note that doing so will share data with third-party providers.
More InformationYou need to load content from reCAPTCHA to submit the form. Please note that doing so will share data with third-party providers.
More InformationYou need to load content from reCAPTCHA to submit the form. Please note that doing so will share data with third-party providers.
More InformationYou need to load content from reCAPTCHA to submit the form. Please note that doing so will share data with third-party providers.
More InformationYou need to load content from Gymnastics styles to submit the form. Please note that doing so will share data with third-party providers.
More Information