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Lubrication

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of the contacting bodies generates a flow induced pressure, which acts as the bearing force over the contact area. In such high pressure regimes, the viscosity of the fluid may rise considerably. At full film elastohydrodynamic lubrication, the generated lubricant film completely separates the surfaces. Due to the strong coupling between lubricant hydrodynamic action and the elastic deformation in contacting solids, this regime of lubrication is an example of
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Besides supporting the load the lubricant may have to perform other functions as well, for instance it may cool the contact areas and remove wear products. While carrying out these functions the lubricant is constantly replaced from the contact areas either by the relative movement (hydrodynamics) or
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Elastohydrodynamic lubrication: Mostly for nonconforming surfaces or higher load conditions, the bodies suffer elastic strains at the contact. Such strain creates a load-bearing area, which provides an almost parallel gap for the fluid to flow through. Much as in hydrodynamic lubrication, the motion
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Boundary film lubrication: The hydrodynamic effects are negligible. The bodies come into closer contact at their asperities (high points); the heat developed by the local pressures causes a condition which is called stick-slip, and some asperities break off. At the elevated temperature and pressure
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In hydrodynamic lubrication, the motion of the contacting surfaces, as well as the design of the bearing, pump lubricant around the bearing to maintain the lubricating film. This design of bearing may wear when started, stopped or reversed, as the lubricant film breaks down. The basis of the
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conditions, chemically reactive constituents of the lubricant react with the contact surface, forming a highly resistant tenacious layer or film on the moving solid surfaces (boundary film) which is capable of supporting the load and major wear or breakdown is avoided.
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Mixed lubrication: This regime is in between the full film elastohydrodynamic and boundary lubrication regimes. The generated lubricant film is not enough to separate the bodies completely, but hydrodynamic effects are
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Fluid film lubrication is the lubrication regime in which, through viscous forces, the load is fully supported by the lubricant within the space or gap between the parts in motion, relative to one another, is avoided.
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etc. where without lubrication the pressure between the surfaces in close proximity would generate enough heat for rapid surface damage which in a coarsened condition may literally weld the surfaces together, causing
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In some applications, such as piston engines, the film between the piston and the cylinder wall also seals the combustion chamber, preventing combustion gases from escaping into the crankcase.
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Popova, E.; Popov, V. L. (2015). "On the history of elastohydrodynamics: The dramatic destiny of Alexander Mohrenstein-Ertel and his contribution to the theory and practice of lubrication".
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Boundary lubrication is defined as the regime in which the load is carried by the surface asperities (high points) rather than by the lubricant. This is the effect that makes
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As the load increases on the contacting surfaces, distinct situations can be observed with respect to the mode of lubrication, which are called lubrication regimes:
398: 508:. Laboratory for Surface Technology and Tribology, Faculty of Engineering Technology, University of Twente, P.O. Box 217, NL 7500 AE Enschede, The Netherlands. 359:
San Andrés. L. "Introduction to pump rotordynamics, Part i. Introduction to hydrodynamic lubrication". ("MEEN626 Lubrication Theory Class:Syllabus FALL2006").
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and the elastic deflection equation to solve for the pressure and deformation in this lubrication regime. Contact between raised solid features, or
540:"On a Model for the Prediction of the Friction Coefficient in Mixed Lubrication Based on a Load-Sharing Concept with Measured Surface Roughness" 139:
pressure, which reduces solid body interactions (and consequently friction and wear). Depending on the degree of surface separation, different
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Singh, Kushagra; Sadeghi, Farshid; Russell, Thomas; Lorenz, Steven J.; Peterson, Wyatt; Villarreal, Jaret; Jinmon, Takumi (2021-09-01).
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If the information is appropriate for the lead of the article, this information should also be included in the body of the article.
185:. The governing equations of the hydrodynamic theory of lubrication and some analytical solutions can be found in the reference. 67: 274: 307:- A system that delivers controlled amounts of lubricant to multiple locations on a machine while the machine is operating. 336: 89: 582: 192: 304: 48:. The two bottles of lubricant are attached to the piston and move while the engine is operating. 445: 117:
in a contact between two surfaces. The study of lubrication is a discipline in the field of
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In hydrostatic lubrication, external pressure is applied to the lubricant in the
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to maintain the fluid lubricant film where it would otherwise be squeezed out.
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Akchurin, Aydar; Bosman, Rob; Lugt, Piet M.; Drogen, Mark van (2015-05-31).
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Lubrication is required for correct operation of mechanical systems such as
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are designed so that the applied load is partially or completely carried by
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The presence of a material to reduce friction between two surfaces.
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contains information that is not included elsewhere in the article
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Adequate lubrication allows smooth, continuous operation of
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Microscopic Mild Wear in the Boundary Lubrication regime
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If an engine required pressurised lubrication to, say,
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Index

Elastohydrodynamic lubrication
grease (networking)

steam engine
crankshaft
lead section
Learn how and when to remove this message
lubricant
friction
wear and tear
tribology
hydrodynamic
hydrostatic
machine elements
bearing
Reynolds equation
Fluid-structure interaction
Reynolds equation
Ultra-high-molecular-weight polyethylene
pistons
pumps
cams
bearings
turbines
gears
roller chains
cutting tools
seizure
plain bearings
oil pump

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