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MolaKule

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Name the Four (4) lubrication "Regimes" with a brief description (a few sentences) of each regime.


This question is open to all, but let's please allow non-engineers, non-Tribologists and non-chemists time to research the question and respond before answering.
 
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Hint: In Tribology, there are four major categories or "Regimes" encountered in Fluid-Lubricated Systems.

Linctex has named two of those but to answer the question fully we need to name all Four (4) lubrication "Regimes" with a brief description (a few sentences) which describes each regime.
 
Boundary-- two surfaces come directly into contact because the oil film has been completely collapsed. Friction is the highest and the protection of the surfaces is down to the sacrificial AW layer.


Mixed-- the two surfaces are experiencing boundary lubrication in some areas and and hydrodynamic in other areas.


Hydrodynamic-- the two surfaces are completely separated by a full film of oil. Any friction at this stage occurs within the lubricant itself.


Elastohydrodynamic-- occurs when a rolling motion exists between two surfaces. The surfaces have a small contact area (such as a roller bearing and a race) which drastically increases the oil pressure at the point of contact, which increases the oil's viscosity. An oil film of about 1 micron is still maintained. This pressure will temporarily deform the metal at the point of contact until it elastically returns to its normal shape as it rotates. This allows the oil to cling to the bearing/gear as it continues to rotate.
 
Mixed film lubrication and full fluid lubrication


Full fluid lubrication: uses a oil wedge between shadt and bearings surfaces

Mixed film lubrication: when asperity contact reduced, film thickness is increased coefficient of friction can drop.
 
Thanks to all who responded!

ZraHamilton gets this one correct by answering all four items and giving an explanation.

The only thing I would add is this:

In Boundary Lubrication a very thin film of lubricant exists but not enough to separate the asperities. The load will be carried by the asperities alone unless there is an Anti-Wear (engines and transmissions) or an Extreme Pressure (Hypoid differential type loads) with a metallo-chemical interface between the sliding or rotating parts.

In Mixed Lubrication you have both a hydrodynamic and boundary lubrication situation where the thin film AND the asperities are carrying the load unless t[/b]here is an Anti-Wear (engines and transmissions) or there is an or an Extreme Pressure (Hypoid differential type loads) with a metallo-chemical interface between the sliding or rotating parts.

The best case of course would be Hydrodynamic Lubrication.

The virtual BITOG Cup with the
thumbsup2.gif
emblem and the XWXX Synthetic Oil goes to ZraHamilton .
 
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