Question

When the load on the rubbing surfaces is carried partly by a fluid viscous film and partly by areas of boundary lubrication, it is known as

(a) incomplete lubrication

(b) viscous lubrication

(c) solid lubrication

(d) none of the mentioned

The question was posed to me during an online interview.

My doubt stems from Limiting Angle of Friction in division Friction of Machine Kinematics

Answer 1

Right choice is (a) incomplete lubrication

The best explanation: When the lubrication is arranged so that rubbing surfaces are separated by a fluid film, and the load on the surfaces is carried entirely by the hydrostatic or hydrodynamic pressure in the film, it is known as viscous lubrication.

When the rubbing surfaces are separated from each other by a very thin film of lubricant it is known as boundary lubrication.

When the load on the rubbing surfaces is carried partly by a fluid viscous film and partly by areas of boundary lubrication, it is known as incomplete lubrication.