Aug
13
2012
Articles

Factors affecting the friction between surfaces

Author An article by Yarina Gao    Comments No Comments
    Dry surfaces

  1. For low surface pressures the friction is directly proportional to the pressure between the surfaces.  As the pressure rises the friction factor rises slightly. At very high pressure the friction factor then quickly increases to seizing
  2. For low surface pressures the coefficient of friction is independent of surface area.
  3. At low velocities the friction is independent of the relative surface velocity.  At higher velocities the coefficent of friction decreases.
    Well lubricated surfaces

  1. The friction resistance is almost independent of the specific pressure between the surfaces.
  2. At low pressures the friction varies directly as the relative surface speed
  3. At high pressures the friction is high at low velocities falling as the velocity increases to a minimum at about 0.6m/s.  The friction then rises in proportion the velocity 2.
  4. The friction is not so dependent of the surface materials
  5. The friction is related to the temperature which affects the viscosity of the lubricant

Other effects also have an effect on the surface friction values including

  • Surface adhesion between pure metal surfaces which probably contributes little to surface friction under normal conditions because of the effect of surface films and contaminants. In vacuum conditions surface adhesion probably has a significant effect on the friction.
  • Ploughing- This is the ploughing of one surface by the asperities on the other surface
  • Elastic deformation of the surfaces as relative movement takes place
  • Junction growth resulting in an increase in the contact area as relative motion takes place

If the surface films can be eliminated then the coefficient of friction can be increased by an order of magnitude. This has be done experimentally by heating test metals in a vacuum

About the Author: Yarina Gao

Marketing Specialist in Labthink Instruments Co., Ltd. which a professional designer and manufacturer of testing instruments for plastic films, sheetings, paper and paper board and other flexible packaging material and finished packages.

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