Friction Coefficients

  • Thread starter Sturk200
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Where do I find a good comprehensive table of friction coefficients between various materials? I'd like, in particular, to be able to compare the coefficient of static friction between tungsten carbide and sapphire and that between sapphire and sapphire. Tables that I have found tend to have sapphire on sapphire, but not tungsten carbide on sapphire. Is there some master table of these things that engineers know about or am I just going to have to get my hands on these materials and test them myself?

Thanks!
 
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This is a murky area, I think in part because there is so much variation in the data. The question depends on much more than just which materials are in contact. It is particularly dependent on the surface conditions, and these conditions are non-repeatable.

Imagine that you set up a test to measure the coefficient of friction, using the same two specimens for 5 different tests. Each time you run the test, you wear away a small amount of material and change the lubrication state on the contact surfaces. So even though you are using exactly the same two specimens, they really are not quite the same from one test to the next. If you use five different pairs, you can expect even more spread in your data.

The short answer is any tabulated data you find is only an experience based estimate that may, or may not, apply in your particular case.
 

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