He specialized in solving problems in machine design by applying his knowledge of tribology. Neale was another leader in the field during the mid-to-late 1900's. Together they wrote the seminal textbook The Friction and Lubrication of Solids (Part I originally published in 1950 and Part II in 1964). Other pioneers of tribology research are Australian physicist Frank Philip Bowden and British physicist David Tabor, both of Cavendish Laboratory. In 1953, John Frederick Archard developed the Archard equation which describes sliding wear and is based on the theory of asperity contact. In 1860, Theodor Reye proposed Reye's hypothesis. They found that coins with grit between them wore at a faster rate compared to self-mated coins. In a study commissioned by the Privy Council of the UK, they used a simple reciprocating machine to evaluate the wear rate of gold coins. In 1798, Charles Hatchett and Henry Cavendish carried out the first reliable test on frictional wear. These laws were further developed by Charles-Augustin de Coulomb (in 1785), who noticed that static friction force may depend on the contact time and sliding (kinetic) friction may depend on sliding velocity, normal force and contact area.
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He also observed that the force needed to overcome friction doubles as weight doubles. According to da Vinci, frictional resistance was the same for two different objects of the same weight but making contact over different widths and lengths.
![gstarcad cycling through overlapping objects gstarcad cycling through overlapping objects](https://www.gstarcad.gr/wp-content/uploads/2019/05/cad_collaborative_icon1.png)
3.1.4 Static and dynamic friction coefficient.