Schmierregime

Schmierregime, or lubrication regime, describes the state of lubrication at the contact between two surfaces in a tribological system. It depends on the thickness of the lubricant film relative to surface roughness, the contact geometry, and the operating conditions such as speed and load. The regime determines whether surfaces touch directly or are separated by a film of lubricant, with a direct impact on friction, wear, and energy loss.

The main regimes are boundary lubrication, mixed lubrication, hydrodynamic lubrication, and elastohydrodynamic lubrication. Boundary lubrication occurs when the film is very thin and asperity contact dominates; additives in the lubricant (such as anti-wear and extreme-pressure additives) help reduce wear. Mixed lubrication is a transition regime where both film formation and asperity contacts occur, making friction and wear sensitive to film development and surface interactions. Hydrodynamic lubrication features a fully developed lubricant film that separates the surfaces completely, typically at higher speeds and with smoother surfaces. Elastohydrodynamic lubrication applies to highly loaded contacts where elastic deformation of the surfaces and high pressures thickens the film; this regime is common in gears and rolling bearings.

Additional regimes include starvation or dry running, where lubricant supply is insufficient and load is carried mainly by asperity contacts. The Schmierregime is often analyzed using concepts like the Stribeck curve and film thickness estimations (lambda ratio) and governed by dimensionless numbers such as the Sommerfeld number. Factors influencing the regime include lubricant viscosity and temperature, speed, load, surface roughness and geometry, and lubricant chemistry.

Understanding the Schmierregime guides lubricant selection, surface finish, and operating limits to optimize wear protection, efficiency, and noise performance.