elastohydrodische

Elastohydrodynamic lubrication, commonly abbreviated as EHL, is a specialized form of fluid film lubrication that occurs when two heavily loaded surfaces move relative to each other under conditions of high pressure and low sliding speed. The term combines "elasto," referring to the elastic deformation of solid surfaces, and "hydrodynamic," describing the formation of a fluid film between them. This phenomenon is critical in applications such as gears, bearings, and cam-follower systems, where high contact stresses and minimal wear are essential for performance and longevity.

In EHL, the applied load causes the elastic surfaces to deform slightly, creating a narrow gap filled with lubricant. Under high pressure, the lubricant’s viscosity increases dramatically due to its pressure-viscosity relationship, forming a thick, self-generating fluid film that separates the surfaces. This effect, known as the pressure-viscosity coefficient, ensures that the lubricant maintains its structural integrity even under extreme loads. The deformation of the surfaces and the resulting fluid film thickness are governed by the Hamrock-Dowson equation, a widely used model in tribology that accounts for factors such as load, surface velocity, and lubricant properties.

EHL differs from traditional hydrodynamic lubrication by its reliance on elastic deformation to sustain the fluid film. Unlike rigid surfaces, which require higher speeds to generate sufficient hydrodynamic pressure, EHL operates effectively at lower speeds due to the lubricant’s ability to thicken under pressure. This makes it particularly suitable for applications where high loads and moderate speeds are common. Poor lubrication in EHL conditions can lead to surface fatigue, pitting, or scuffing, highlighting the importance of selecting appropriate lubricants and maintaining optimal operating parameters.

The study of EHL involves experimental techniques such as optical interferometry and computational methods like finite element analysis to simulate contact mechanics and fluid flow. Advances in materials science, including the use of hard coatings and advanced lubricants, continue to enhance the performance and durability of components operating under elastohydrodynamic conditions.