Stribeck v.s. Coulomb friction law

[qnach]

TL;DR

Compare Stribeck and Columb law

The friction law I learnt in high-school is Coulomb law, to my understanding.
But what is Stribeck law? What is the difference from Coulomb's law?

 

[Arjan82]

It seems that the Stribeck law is a law firm concerning real estate located in Indianapolis... ;)

There is a Stribeck curve though. Coulomb's law is about dry friction. Stribeck's curve is about lubricated friction. The curve tells you in what lubrication regime you are, whether the surfaces still make contact, whether the surfaces are fully separated by a hydrodynamic film (very low friction and wear!) or somewhere in between.

That it was possible for lubricated surfaces to be separated entirely was kind of a big deal when first discovered. It means that with proper design and lubrication the wear and tear on bearings dramatically decreases. This is how the field of tribology came about (more or less, I'm not a historian ;)).

Some anecdote I remember from my study:
The forces involved in the hydrodynamic film are enormous by the way. I remember how my tribology professor tried to replicate an experiment done during the time of this discovery. There was a flat surface with a rather large and heavy (think 100/200kg) cylindrical surface on top of it. In the center of that cylindrical surface there was a hole in which lubricant could be added. (I also vaguely remember that the contact surfaces were somehow etched with some spiral shape to draw the lubricant under the cylinder, but I'm not entirely sure). To get the cylinder rotating on the surface was hard to start, but once going the cylinder would just go on an on.
At the same time lubricant would run out of that hole in the center of the cylinder. As the story goes the experimenter (not my professor, he tried to replicate this) tried to stop the lubricant to come out. Eventually he hammered some kind of cork or wooden peg into the hole with some force. After rotating a bit that peg came out with a huge BANG shooting the peg into the ceiling of the room!
Unfortunately my professor was never able to replicate this properly...