testing for coefficent of friction on wood 1

[dm3415]

I have an attorney who is looking to test the coefficient of friction on some wood for lawerly reasons. Has anyone ever seen a standardized test for measuring friction on a building material? It wouldn't be hard using engineering principles to come up with something myself, but I would like to be able to reference a standard if it goes to court and I testify.
Thanks

 

[NKT]

The coefficient of friction is easy to test, but the test is not very technically impressive.

To measure the coefficient of static friction:
1. Place a board of the wood in question on a level surface.
2. Place the other object on the board.
3. Raise the end of the board, slowly, until the object just starts to slide.
4. Measure and record the angle of the board.
5. Calculate the coefficient of static friction (the tangent of the angle between the board and the horizontal surface).

The coefficient of dynamic friction is a little tricky to measure. You have to find the angle of the board where the object maintains a constant velocity when you give it a little push. This is (almost?) always a lower angle than that measured with the test for coefficient of static friction.

I don't know of any published engineering standard for this method, but you can find it given as an example in just about any undergraduate physics text.

If you feel the need to involve expensive equipment, a direct shear machine (used for soil testing) could be used to explore several different normal force scenarios between the two surfaces.

 

[MiketheEngineer]

I found the following-

Wood on Wood - .450
Wood on Metal - .550
Wood on Concrete - .450

But these are VERY general and obviously change due to specific materials. Also - if they are wet - things change again.... Good Luck

 

[boo1]

I would consider using:
ASTM G115 - 04 Standard Guide for Measuring and Reporting Friction Coefficients

http://www.astm.org/Standards/G115.htm

ASTM D2047 - 04 Standard Test Method for Static Coefficient of Friction of Polish-Coated Flooring Surfaces as Measured by the James Machine

http://www.astm.org/Standards/D2047.htm

 

[Dinosaur]

Without knowing of a std ASTM, to measure dynamic coefficient of friction I would do the following experiment.

Place one board on a scale and record the weight. Place a second board on the first board and record the weight of both. Place a third board on top of the first two and record the total weight. Holding the first and third boards in place, pull the middle board out while measuring the force required with a fishing scale or similar calibrated scale. You now have all the values needed to compute the coefficient of sliding friction.

This test would be straight forward and repeatable but not sexy. Also, I agree the best way to determine the coefficient of static friction is to tilt one board until you begin to get motion and then compute (or measure directly) the arctan of the angle.

Good Luck.

 

[civilperson]

Coefficient of friction is dependent on the smoothness of the various surfaces. Wood and some other surface both need defining as to finish quality.

 

[dm3415]

Thanks Boo1, that answers my question