Elastohydrodynamic Lubrication Boundary Lubrication Lubricant Viscosity Heat Removal Suspension of Contaminants Friction Reduction Simply stated, friction is reduced by maintaining a film of lubricant between surfaces that are moving with respect to each other, thereby preventing the surfaces from coming into contact and subsequently causing surface damage.
Friction is a common element in daily life.
One can walk up a steep ramp without slipping back because of high friction between shoe soles and the ramp surface. One can slide down a ski run because friction between packed snow and skis is low. Both cases illustrate friction between ordinary surfaces. The coefficient is roughly constant for any pair of surfaces. For nonlubricated metal of ordinary surface finish and cleanliness, exposed to the atmosphere, the value may be about 1.