The lubrication mode of rolling bearings, gear teeth and cams, where contact pressures of 1 to 3 GPa make the oil momentarily far more viscous and squash the steel elastically into a tiny flat. The resulting film is only about 0.1 to 1 micron thick but carries the load for the instant the oil spends in the contact. Film thickness depends mostly on speed and operating viscosity and only weakly on load, which is why viscosity selection matters so much for bearing life.
That spherical roller runs in elastohydrodynamic lubrication with under half a micron of film, so ten micron dirt does real damage.
Also heard as
- EHL
- EHD lubrication
Related terms
Lambda ratio
Oil film thickness divided by the combined roughness of the two surfaces, used to judge the lubrication regime.
Mixed lubrication
Transitional regime where the load is shared between a partial fluid film and asperity contact.
Hydrodynamic lubrication
Full-film lubrication in which motion drags oil into a narrowing gap and builds enough pressure to float the load.
Micropitting
Fatigue damage made of tiny pits, about 10 to 20 microns deep, that turns gear and bearing surfaces dull gray.
Viscosity
A fluid's resistance to flow, the lubricant property that sets how thick an oil film can build.