Elastohydrodynamically

Elastohydrodynamically refers to a regime of lubrication where the deformation of elastic solid surfaces significantly influences the lubricating film's behavior. This is distinct from purely hydrodynamic lubrication, where fluid pressure alone supports the load, and boundary lubrication, where direct surface contact occurs. In elastohydrodynamic lubrication (EHL), the lubricant film is very thin, often on the order of nanometers to micrometers.

The key characteristic of EHL is the combined effect of fluid film pressure and the elastic deformation of the contacting surfaces. As two surfaces move relative to each other under load, the lubricant is entrained into the converging gap between them. This entrainment, along with the high pressures generated within the lubricant, causes the elastic surfaces to deform. This deformation, in turn, alters the geometry of the converging gap, which influences the lubricant pressure distribution and the film thickness.

EHL is typically observed in highly loaded, low-speed contacts, such as in rolling element bearings, gears, and cams. The pressure within the EHL film can be extremely high, reaching gigapascals, leading to significant changes in the lubricant's viscosity and density. Despite the extremely thin film, it is often sufficient to prevent direct metal-to-metal contact, thus reducing wear and friction. Understanding EHL is crucial for designing and analyzing the performance of many mechanical components subjected to demanding operating conditions.