elastohydrodisk

Elastohydrodisk, more commonly referred to as elastohydrodynamic lubrication (EHL), is a regime of lubrication in which the contact between two relatively moving, non-conforming surfaces is separated by a thin lubricant film. In EHL, the surfaces deform elastically under high contact pressures, and the lubricant film is formed primarily by hydrodynamic pressure generated as the surfaces entrain lubricant during motion. The viscosity of the lubricant often increases with pressure, further thickening the film.

Geometries such as the contact between mating gears, cam followers, and rolling bearings create high Hertzian stresses (often hundreds of megapascals to gigapascals) that deform the surfaces and maintain separation at film thicknesses typically from tens of nanometers up to a few micrometers, depending on speed, load, lubricant, and materials.

Key features include a coupled problem: solving the Reynolds equation for the pressure field in the lubricant while accounting for elastic deformation of the contacting bodies and the pressure dependence of viscosity. The result is an elliptical contact area with pressure peaks and a film that reduces metal-to-metal contact, but stores energy in the elastic deformation of the surfaces.

Typical conditions for EHL occur at moderate to high speeds and high loads, where boundary and mixed lubrication would otherwise suffer metal contact. The term is often used interchangeably with elastohydrodynamic lubrication; non-Newtonian effects and traction mechanisms (rolling resistance) are important for power transmission applications.

Applications include gears, rolling-element bearings, hybrid bearings, cam followers, and other high-load, high-pressure contacts. Pioneering work in this field by Dowson, Hamrock, and colleagues established the theoretical and practical framework for EHL film thickness predictions and traction estimates. Modern practice relies on numerical simulation and experimental measurements for lubricant selection and component design.