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[Jan Stránský <question265830@xxxxxxxxxxxxxxxxxxxxx>]

Question #265830 on Yade changed:
https://answers.launchpad.net/yade/+question/265830

Jan Stránský proposed the following answer:
>
>
> If there's only one sphere, so we're measuring the loads-displacement
> response of cohFrictPhy contacts! (Since in my model cohfrictMat,
> cohBurgersMat make a cohfrictPhys) and this is not what we want. We're
> interested in cohBurgersPhys contacts, in this case sphere-sphere ones.


sorry, you are right, but you explained the problem yourself, see your next
commet :-)


> So imagine we have two spheres vertically in contact and placed between
> two plates. If a load is applied we have a deformation which is sum of
> there components:
> 1) UpperPlate-upperSphere contact (cohFrictPhys)
> 2)sphere-sphere contact (cohBurgersPhys)
> 3) LowerPlate-LowerSphere contact (cohFrictPhys)
>

see below


>
> We're measuring the testing material's properties and so should minimize
> the plates contribution in the calculations. Thus, a high value of
> stiffness for those contacts can solve the problem.
>

exactly :-) do an analytical computation of your model represented as a rod
with length 4*radius and cross section area radius^2 - the volume
approximated by your particle model. Compare it to Yade results with two
spheres and two plates with much higher stiffness (explained by you above).
You should get the same / very similar results.

cheers
Jan

PS: radius^2 as a cross section area might be multiplied by a constant like
pi, depending on implementation

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