![]() ![]() The “elasto” term in EHD refers to the effect of the hertzian line or point contacts, which produce extreme pressures and therefore elastically deform the surfaces to provide small elliptical contact areas. The different geometric nature of plain and rolling bearings creates different lubrication regimes: plain bearings have hydrodynamic (and sometimes hydrostatic) lubrication conditions while rolling element bearings (also cams and gears) operate with elasto-hydrodynamic (EHD) lubrication regimes. Lubricant considerations include cleanliness, allowable water content, viscosity, viscosity index improvers, wear protection additives, oxidation inhibitors, friction modifiers, seal swell additives, corrosion inhibitors and antifoam additives.Įven if proper lubrication and operating conditions are scrupulously maintained, rolling element bearings will eventually fail by fatigue because of subsurface voids, cracks or inclusions. If ideal lubrication and operating conditions (such as load ranges, speed ranges, temperature ranges) are maintained, plain bearings will not fail. Gear drives also have nonconformal interacting surfaces and have both rolling and sliding action (on an oil film) at the tooth interfaces. Rolling element bearings have nonconformal contact surfaces (line or point contacts called hertzian contacts) that support moving parts of machinery with rolling action (on an oil film) at the interfaces. Plain, journal, sleeve or shell bearings, and piston rings and bushes, have conformal interacting surfaces (area contact surfaces) that support the moving parts of machinery with sliding action (on an oil film) at the interfaces. Also discussed are bearing failure modes due to contamination as well as results of experiments with different filtration. The work disovered that surface cracks can result in pitting only subsurface cracks result in spalling and spalling is failure caused by the material collapse at subsurface crack tip ligaments. This article summarizes the author’s findings on wear in rolling element bearings and gears. ![]()
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