Coefficient of Friction

[VEN]

Does anyone know any good websites to find the coefficient of friction of certain materials in contact? I'm mainly looking for copper on chormium. I am assuming it would be less than copper on steel which is .36 mu

[chris31]

I found alot of other values here (http://www.school-for-champions.com/science/frictioncoeff.htm) but cant seem to find those two together.

[VEN]

Yep, I found that one too, and for some reason they don't have kinetic friction for chromium on chromium...just static

[VEN]

can i take chromium on chromium friction and copper on copper friction and average it out?

[Imajie]

If you have samples of both materials you could do a simple test to get an answer probably not most accurate but better than nothing.

If you have a smaller piece of one of the materials and put it towards the end of a longer piece of the other and raise that end until it begins to slide down at a constant rate. The tangent of the angle would be your coefficient of kinetic friction because at that angle the parallel force of gravity is equal to the force of kinetic friction. This paper (http://www.rowan.edu/colleges/lasold/physicsandastronomy/LabManual/labs/Friction.pdf) provides a better explanation of why it is.

[Stu Bloom]

can i take chromium on chromium friction and copper on copper friction and average it out?I don't think that will work ... based on information from the table (website) referenced above:

Static Friction example:
Copper / Copper - 1.0 (my source "Marks Handbook (http://www.amazon.com/Marks-Standard-Handbook-Mechanical-Engineers/dp/0070049971)" shows 1.21)
Mild Steel / Mild Steel - .74
Average would be .87, table says (Copper / Mild Steel) .53

Copper / Copper - 1.0
Cast Iron / Cast Iron - 1.1
Average - 1.05, table says 1.05 (WOW !) - except my source says Cu/Cu: 1.21

Anyway, that doesn't seem to be a reliable way to estimate the friction coefficient. Also, I am sure you are aware that MANY factors can affect your actual friction. Surface finish/roughness, Lubrication, Contamination, Oxidation ...

Your best bet is to experiment with samples of the material you are interested in and collect your own data (as Imajie just posted :p ).

[Dick Linn]

I second the experimental approach. Too many variables...

[Pavan Dave]

I should have paid more attention in physics. :(

Pavan.

[Tottanka]

Just make a test with ditance sensors =]

[VEN]

Thanks for the input guys

[Rob2713g]

Although I'm not sure how accurate this site (http://www.roymech.co.uk/Useful_Tables/Tribology/co_of_frict.htm) is, it has Cu on Cr under "Coefficient of Friction" > "Table of friction Values for elements". Also it has some links at the bottom you may want to explore. Good Luck!