StribeckVerlauf

The Stribeck curve, or Stribeck-Verlauf, is a foundational concept in tribology that describes how the friction coefficient mu changes with relative sliding speed in lubricated contacts. Named after the researcher who documented the relationship, the curve is typically plotted with mu on the vertical axis and a dimensionless speed parameter on the horizontal axis. Its shape reflects the formation of a lubricating film as speed increases, which reduces direct surface contact and lowers friction.

In most formulations, the curve exhibits three lubrication regimes. Boundary lubrication occurs at very low speeds, where rough surfaces and asperity contacts dominate and friction is high. Mixed lubrication appears at intermediate speeds, with partial film formation and a gradual reduction in friction. Hydrodynamic or full-film lubrication dominates at high speeds, where surfaces are separated by a continuous lubricant film and friction is governed mainly by viscous shear within the lubricant.

A common dimensionless parameter used on the horizontal axis is the Stribeck number, defined as S = eta * v / p, where eta is the dynamic viscosity, v is the sliding speed, and p is the contact pressure. The mu(S) curve depends on lubricant properties, temperature, surface roughness, and load, and it is used to characterize and compare lubricants as well as to predict performance under varying operating conditions.

Applications of the Stribeck-Verlauf span bearings, gears, seals, and other lubricated sliding contacts. It informs lubricant selection, operating speed ranges, energy losses, and wear propensity, serving as a practical tool in the design and analysis of mechanical systems that rely on lubrication.