Friction is important to our daily existence and is present all around us. Starting with brushing teeth in the morning, driving a car and relying on a good grip of tyres, or looking at a mechanical watch with a confidence that all miniature parts are functioning properly to show us a correct time. As a field of science, study of friction is part of tribology, is the science and engineering of interacting surfaces in relative motion.
It includes the study and application of the principles of friction, lubrication and wear. The word tribology derives from the Greek “tribo” (“I rub”) and the suffix “logos” (“study of”, “knowledge of”).
Leonardo da Vinci, understood very well that friction is a limiting factor in the design of his revolutionary machines. He worked on the subject for more than 20 years, as evidenced by his beautifully illustrated notes and sketches. Leonardo distinguished between rolling and sliding friction and made observations that surface roughness has an impact on how easy it is to move different materials. His tribological experiments were dictated by his curiosity, but perhaps mainly by his pragmatic nature, as he needed reliable mechanical solutions for the design of his components.
He was the first to record the laws of friction and he managed to achieve that by designing experiments using strings, pulleys and weights. Experiments based on the same principles are carried out on modern friction testers called tribometers.
Today, tribologists around the world are building on foundations laid by Leonardo. Modern studies confirm the importance of urgent development of low friction surfaces to control the energy consumption, economic expenditure and CO₂ emissions on a global scale. Understanding the fundamentals of friction is key for a design of reliable and efficient electrical vehicles, wind turbines, and medical implants such as hip replacements.