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[Eugen Kubowsky <question225776@xxxxxxxxxxxxxxxxxxxxx>]

Question #225776 on Yade changed:
https://answers.launchpad.net/yade/+question/225776

    Status: Answered => Open

Eugen Kubowsky is still having a problem:
Thanks Nguyen.
if you look at [1] there is one thing I dont understand. 
I give you an example:
in [1] you see a box which is placed on a plane. Mass of the box causes force N on the plane. Now I push the box with an increasing force T.
using the maximal possible T for which the box wont start sliding gives me a frictionAngle. (static friction)

If we assume that the box is already moving (with constant speed) there
is an T for which acceleration will be zero - so velocity stays
constant. This T gives an dynamic frictionAngle.

This leads to my second question from above: Does yade use static or
dynamic frictionAngle

Concerning my first question - let us enhance this little example.
may the box be made of material1 and the plane of material2.
If you determine the frictionAngle it is valid for this pair of materials only.

Think of a different plane made of material3. 
The experiment from above will give you a diffrent frictionAngle. But when you simulate this box on a plane in Yade both materials must be given a frictionAngle, from which the matchmaker [2] will use the lowest for calculation of interactions[3].

This leads to a problem: if frictionAngle of material1 is lower than
material2 and material3 than the matchmaker will use its frictionAngle
whatever plane it will be placed on. Hence force T would be equal for
both planes. This does not go in hand with real experiments.

As I mentioned earlier - in my eyes frictionAngle cant be defined for a
single material but for a pair of two materials.

---
[1] http://www.geotechdata.info/parameter/angle-of-friction
[2] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.MatchMaker
[3] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.Ip2_FrictMat_FrictMat_FrictPhys

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