Elastohydrodynamische

Elastohydrodynamische Schmierung, commonly referred to in English as elastohydrodynamic lubrication (EHL), describes a lubrication regime in which the elastic deformation of contacting surfaces and the hydrodynamic pressure in a thin lubricant film interact. The film separates the surfaces under high load, yet its thickness is small enough that surface roughness and material deformation significantly influence the pressure distribution and film shape.

Key features of EHL include entrainment of lubricant between moving surfaces, generation of a high-pressure fluid film, and elastic deformation of the contacting bodies. The governing physics combine hydrodynamics, via the Reynolds equation, with elasticity theories (often Hertzian) to predict film thickness and pressure. Contacts can be line-type (as in cylindrical gears) or point-type (as in rolling bearings). Film thickness in EHL is typically in the nanometer to micrometer range, while contact pressures can reach hundreds of megapascals to gigapascals, depending on load, speed, viscosity, and material properties. Temperature rise from viscous heating is also an important consideration.

Modeling EHL requires coupled fluid-structure analysis. Numerical methods are standard, and semi-empirical models (such as those developed by Hamrock and Dowson) provide practical estimates for minimum film thickness and peak pressure under various conditions. The regime often lies between fully hydrodynamic lubrication and boundary/mixed lubrication, with transitions driven by load, speed, and temperature.

Applications of elastohydrodynamic lubrication are common in gears, rolling-element bearings, and cam-follower mechanisms where high contact stresses demand very thin, highly pressurized lubricant films. Material systems typically involve steel or alloys and high-viscosity mineral or synthetic oils, with additives tailored to wear resistance and film stability.