Elastohydrodynamic lubrication
Elastohydrodynamische Schmierung (EHD)
Elastohydrodynamic lubrication (EHD/EHL) is the lubrication regime in the rolling contact: under extreme contact pressure, an ultra-thin load-carrying lubricant film forms between rolling element and raceway. The steel surfaces deform elastically and the lubricant's viscosity rises sharply within the contact – this interplay is what enables full surface separation. Film thickness depends mainly on base oil operating viscosity, contact speed and temperature, while load has comparatively little influence. Film adequacy is assessed via the viscosity ratio, which feeds directly into modified bearing life calculation. Insufficient viscosity or speed causes mixed friction, surface distress and premature fatigue.