Which form of lubrication is described as a rolling contact application?

• A. Solid-film
• B. Elastohydrodynamic
• C. Hydrodynamic
• D. Boundary

Answer: (B)

Rolling-contact lubrication is elastohydrodynamic lubrication. In rolling bearings and gears, the contact pressures are very high and the surfaces deform elastically under load. The lubricant film forms because the rolling motion entrains lubricant into the contact and the lubricant’s viscosity rises under pressure, so a thin film develops that keeps the surfaces apart even under heavy load. This combination of rolling motion, high pressure, and elastic surface deformation is what characterizes the elastohydrodynamic regime. Hydrodynamic lubrication involves film formation mainly from sliding motion and can be thicker but without the same elastic deformation; boundary lubrication refers to very thin films where surface interactions dominate, and solid-film lubrication uses a solid lubricant layer rather than a fluid film.