Coulomb effects friction laws

However, some theoretical treatment considers only the special case of friction sliding of a single fiber along a mechanically bonded interface, particularly for some ceramic matrix composites, where the Coulomb friction law applies. See for example Zhou and Mai (1995) and Shetty (1988). Assuming a constant friction at the fiber-matrix interface and neglecting the Poisson effects, Shetty (1988) reported a simple force balance equation for the frictional shear strength, Tfr... 

Friction is the tangential resistance offered to the sliding of one solid over another, due to dry friction. Friction is an apparently simple phenomenon with very complex mechanisms that take place on a variety of length scales, from atomic to nano and up. The study of friction is part of the engineering-scientific discipline of tribology,3 which is the scientific study of friction, wear, and lubrication (6). It was Leonardo da Vinci (1452-1519) who discovered the first two laws of friction, namely, that the area of contact has no effect on friction and that friction is proportional to the load. These two laws were rediscovered later by Guillaume Amontons (1663-1705), and later Charles-Augustin Coulomb (1736-1806), added the third law ... 

Friction force is proportional to the normal load as stated by Amontons-Coulomb s law. For microloads less than 1 mN, which are often found in mechanisms such as microelectromechanical systems (MEMS), Amontons-Coulomb s law is not valid due to the effect of the adhesion force between the contacting surfaces [1]. Studies show that, at such microloads, either the attraction force (adhesion force) caused by the surface tension of water condensed on the surface or the van der Waals force dominates the friction force, and that the friction force is proportional to the sum of the adhesion force (pull-off force) and the normal load [2, 3],... 

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