StribeckKurve

StribeckKurve, commonly known in English as the Stribeck curve, is a graphical representation of the relationship between the coefficient of friction and a dimensionless parameter that characterises lubrication conditions in tribological contacts. The curve was first introduced by the German engineer Richard Stribeck in the early 20th century and has since become a fundamental tool for analysing and designing lubricated machine elements such as bearings, gears and journal interfaces.

The horizontal axis of the StribeckKurve typically plots the Hersey number, also called the lubrication parameter, which is defined as η V / P, where η denotes the dynamic viscosity of the lubricant, V the relative sliding speed, and P the normal load per unit length (or per unit area in line contacts). The vertical axis shows the steady‑state coefficient of friction μ. The curve exhibits three distinct regimes. At low values of the Hersey number the contact operates in boundary lubrication, where surface asperities are in direct contact and μ is relatively high and relatively constant. As the Hersey number increases, the curve descends into the mixed‑lubrication region; here partial separation of the surfaces occurs, leading to a gradual reduction in μ. At higher Hersey numbers the curve reaches its minimum, indicating the regime of elastohydrodynamic (or full film) lubrication, where a continuous fluid film separates the surfaces and friction is lowest. Beyond this minimum, further increases in speed or viscosity cause a slight rise in μ due to fluid‑film thickening.

The StribeckKurve is employed to select appropriate lubricants, operating speeds and load capacities, and to predict performance limits of tribological systems. Its shape depends on lubricant rheology, surface roughness, temperature and material properties, making it a versatile descriptor of real‑world friction behaviour.