Stribeckkurvorna

Stribeckkurvorna, often translated as Stribeck curves, are graphical representations of the relationship between friction, relative speed, and lubricant viscosity in bearings. Developed by German engineer Richard Stribeck in the early 20th century, these curves illustrate the transition of a bearing from boundary lubrication to hydrodynamic lubrication.

The horizontal axis of a Stribeck curve typically represents the operating parameter, often expressed as the Sommerfeld number or a similar dimensionless group that combines load, speed, and viscosity. The vertical axis represents the coefficient of friction. At very low speeds, the lubricant film is thin, and there is significant metal-to-metal contact, resulting in high friction (boundary lubrication regime). As the speed increases, the lubricant is drawn into the bearing, and a thicker film develops. This leads to a decrease in the coefficient of friction.

A notable point on the curve is the minimum friction coefficient, achieved when the lubricant film is sufficiently thick to separate the moving surfaces. Beyond this point, as speed further increases, the coefficient of friction may slightly rise due to increased viscous drag within the lubricant itself. This phenomenon is characteristic of hydrodynamic lubrication. Stribeck curves are crucial for understanding bearing performance, predicting wear, and optimizing lubricant selection for various operating conditions.