Effect of Normal Pressure on Kinetic Friction Coefficient: Myth or Reality?

Analysis of a number of friction experiments, mostly between ice and various materials, has shown that in all cases the frictional force is a linear function of the normal load rather than proportional to some fractional power of it as predicted by Oksanen's theoretical equation. This could indicate that Oksanen's basic assumption that "the only cause of friction is the water layer formed by frictional heating between the ice and any given surface on which it is sliding” may be invalid, in particular when the roughness height of the surfaces is greater that the water layer thickness. Other processes, gouging or mechanical abrasion, may then become predominant.