Definition - What does Friction mean?

Friction is the reaction force resulting from surface interaction and adhesion during sliding. The friction coefficient is defined as the friction force divided by the load. Friction is a component of the science of tribology, and is an important factor in many engineering disciplines.

Friction causes wear, which may lead to performance degradation and/or damage to components.

Corrosionpedia explains Friction

Friction is the force that opposes the relative motion or tendency of such motion of two surfaces in contact. The friction force is the force exerted by a surface as an object moves across it or makes an effort to move across it. Friction results from the two surfaces being pressed together closely, causing intermolecular attractive forces between molecules of different surfaces. As such, friction depends upon the nature of the two surfaces and upon the degree to which they are pressed together.

Types of friction include:

  • Dry friction
  • Fluid friction
  • Lubricated friction
  • Skin friction
  • Internal friction

The coefficient of friction depends on the materials used, for example, ice on steel has a low coefficient of friction, while rubber on pavement has a high coefficient of friction. Coefficients of friction range from near zero to greater than one.

Friction can be reduced by using devices such as wheels, ball bearings, roller bearings and air cushions as well as by using lubricant, often dramatically lessening the coefficient of friction. Another way to reduce friction between two parts is to superimpose micro-scale vibration to one of the parts.

The work done by friction can translate into deformation, wear, and heat that can affect the contact surface properties. This can be beneficial, as in polishing. The work of friction is used to mix and join materials such as in the process of friction welding. Harder corrosion particles caught between mating surfaces in relative motion (fretting) exacerbates wear of frictional forces.

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