In the case of the

kinetic friction, the slip force opposes the relative movement between the contact points (which may differ from the relative movement between the bodies).

[4] carried out a research in the framework of the theory of plasticity, considered internal friction and cohesion as the variables of the plastic strain function, and proposed a hyperbolic hardening function for

kinetic friction and a mixed parabolic exponential equation for kinetic cohesion.

The static friction coefficient and

kinetic friction coefficient of each fiber were recorded at the standard testing conditions (i.e., 20[degrees]C and 60% RH).

As these four equations show the coefficient of

kinetic friction [[micro].sub.k] and the wall-normal restitution coefficient [e.sub.n] have to be known to calculate the particle velocity after the wall collision.

However, most FE models above did not realize the modelling of real asphalt pavement and failed in considering the fact that the

kinetic friction coefficient varied with different vehicle speed.

Tanaka, "

Kinetic friction and dynamic elastic contact behaviour of polymers," Wear, vol.

Static and

kinetic friction coefficients are fundamental parameters for friction force simulation of drilling string.

Static friction coefficients for a given pair of surfaces usually are higher than those for

kinetic friction. Most dry, clean surface combinations, including coatings, have SCOF values between 0.2 and 0.6.

In order to have a model that considers both rolling and sliding interaction between the gear teeth, a modification of Coulomb's law is applied to obtain the equivalent

kinetic friction coefficient.

That said, the authors did an excellent job of compiling an in-depth appendix of coefficients of static and

kinetic friction. It is by far the most complete collection I have ever seen in a theatrical textbook.

The

kinetic friction coefficient is a useful indicator for describing tribological performance of a solid lubricant coating.