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## Re: [Question #707367]: Adjusting the friction angle between dynamic components (spheres) and non-dynamic components (facets)

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```Question #707367 on Yade changed:
https://answers.launchpad.net/yade/+question/707367

Status: Open => Answered

Jan Stránský proposed the following answer:
Hello,

> frictionAngle=0.65; i.e. approx. 37.5°
> the friction coefficient μ ( approx. 0.75)

μ=0.75 means frictionAngle=atan(0.75)=36.9°
Almost the same as case 1.
So the question is if to bother with two values at all :-)

> To check this friction value I wrote the script.

There are two aspects.
1) What value is actually assign
2) How it behaves in actual simulation

Your script seems to do the option 2, where many factors may influence the result (e.g. dynamic behavior of the sphere).
I suggest first the method 1, i.e. take the interaction and check the actual value, i.e.:
###
intr = O.interactions[0,1] # for example bodies 0 and 1
tanfa = intr.phys.tangensOfFrictionAngle # [4]
###

> My main question is how to set the coefficient of friction for the
facet material to 0.75.

As you do in the script

How to apply it to different material combinations, see below.

> Have I reached this friction value requested by me and an error in
this script?

As mentioned above, the "real" simulation may influence the results.
For friction measurement, I suggest making all particles with prescribed motion such that forces are just measured but do not influence the particles.

> ...

In Yade design, material does not care on what bodies or shapes it is
assigned. So there is nothing like "non-dynamic material"

setContactFriction [5] is an auxiliary function to change friction angle on all
The documentation sentence (and implementation) "The friction for non-dynamic bodies is not modified" is a bit misleading, it actually may or may not be modified, according to how the materials are shared among particles.

To use different values of certain quantity for different material
combinations, specify MatchMaker for frictAngle parameter of
Ip2_FrictMat_FrictMat_FrictPhys

Cheers
Jan

[4] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.FrictPhys.tangensOfFrictionAngle
[5] https://yade-dem.org/doc/yade.utils.html#yade._utils.setContactFriction
[6] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.Ip2_FrictMat_FrictMat_FrictPhys.frictAngle

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