Science · 6 pages · 12 min

Why lubricants reduce friction

A lubricant makes the surfaces shear a film instead of grinding on each other.

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From the opening

Lubricants reduce friction by keeping the high points of two solids from locking together. The surfaces shear a film of oil, grease, or another slippery material, and shearing that film costs less force than tearing solid asperities. The opening covers shearing a film instead of metal, full film versus boundary contact, and why oil pressure lifts a shaft.

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Inside

Shearing a film instead of metal
Full film versus boundary contact
Why oil pressure lifts a shaft
When more oil is not the point
Where the idea stops applying
A distinction worth keeping

Sources

Reynolds hydrodynamic lubrication and the oil wedge
Boundary lubrication when film is thinner than roughness

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Why lubricants reduce friction

From the opening

Inside

Sources

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