Plain bearing friction refers to the resistance to motion between sliding surfaces in bearings such as journal, linear and thrust bearings. The level of friction depends on lubrication conditions, load, speed and material properties.
This page provides basic equations for calculating friction torque and force in plain bearings, along with typical ranges of friction coefficients for different lubrication regimes including hydrodynamic, mixed and dry operation.
Plain bearings can be linear, journal and thrust. They can be hydrostatically, or hydrodynamically
lubricated or operated dry. These different modes of operation can all result
in very different friction factors. The coefficient of friction for plain bearings
relates to the type of bearing, the speed of rotation, the load, the amount and viscosity
of the lubrication, the friction of the seals, etc.
The friction factors provided are approximate and are only suitable for assessment of relative values.
It is very important to note that determination of reasonably accurate friction
factors for lubricated plain bearings is very complicated. Serious design
should include reference to bearing suppliers and/or reputable reference documents.
The bearing friction torque Mr = P · f · (D / 2)
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The bearing friction force Fa = P · f
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The bearing friction torque Mr = P · f · (Do + Di) / 4
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Approximate values for coefficient of friction (f):
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More accurate values should be obtained from supplier technical data and detailed reference sources.