About Leonardo Da Vinci
Leonardo da Vinci carried out some of the very earliest experiments on friction and wear. In his notebooks he made the following observations about friction:
- The friction made by the same weight will be of equal resistance at the beginning of its movement although the contact may be of different breadths and lengths
- Friction produces double the amount of effort if the weight be doubled
From his experiments, Da Vinci had deduced what we commonly call Amontons laws of friction, or Coulomb friction, that is, that friction is independent of area and directly proportional to the normal load. From his experiments he observed that every frictional body has a resistance of friction equal to one-quarter of its weight, or in other words, the friction coefficient is equal to 0.25. Of course this is not universally true but for the kinds of experiments Leonardo was likely to have been doing, using boundary lubricated rough wood or iron for instance, 0.25 is a realistic value.
Leonardo also showed an understanding of the need for lubrication:
“All things and everything whatsoever however thin it be which is interposed in the middle between objects that rub together lighten the difficulty of their friction”
He carried out some wonderful experiments on the wear of axles and shafts, demonstrating the shapes that would be formed as a wooden wheel wore against an iron axle. He also showed that the presence of debris particles could lead to wear of the harder iron surface, a process that we today call Three-Body-Abrasive wear.
Leonardo's notebooks contain beautiful sketches of machines and devices, including designs for bearings, screws and gears; all of which can be found in most modern day machines.
We have put together a page of links to some of the best web sites with a tribological flavour. This page also includes links to several professional bodies and learned societies that represent the interests of tribologists around the world.
Our own Research pages contain details of some of the research caarried out by the Leonardo Centre into several aspects of tribology, especially wear and lubrication.
Or you may like to look at the Tribology of Machine Elements Course that we teach to undergraduate students at the University of Sheffield.