Circular ring

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Circular ring with designations

A circular ring is the area between two concentric circles , i.e. H. between two circles with a common center. Its area is


where is the number of circles and and mean the radii as well as and the diameter of the outer and inner circle.

The area can also be calculated from the inside diameter or outside diameter and ring width :

This information can be found e.g. B. with pipe cross-sections; where is the wall thickness.

Furthermore, the area can be calculated using the annulus width and the mean annulus diameter


The effective hydraulic diameter for a circular ring for hydraulic applications is


Should z. For example, for brake discs , a frictional torque to the axial force and the coefficient of friction by

are determined, the friction-relevant radius calculated or diameter by

or .

See also

Torus , hollow cylinder , spherical shell

Web links

Commons : Circular Rings  - Collection of images, videos and audio files
Wiktionary: Kreisring  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  2. ^ H. Hinzen: machine elements . Volume 2. Oldenbourg Verlag, 2001