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[Bruno Chareyre <question269063@xxxxxxxxxxxxxxxxxxxxx>]

Question #269063 on Yade changed:
https://answers.launchpad.net/yade/+question/269063

Bruno Chareyre proposed the following answer:
>the mesh constructed in Ansys is also not very fine

The real question is the number of nodes/gauss points in each element
times the number of elements, not the number of elements alone. Looking
at you stress field, I guess they are high order elements (i.e. many
DOFs per element).

>About regularity: should i use random packing instead of regular array
or what?

Yes certainly if you want to simulate an isotropic material. The problem
if you do that is that per-body stress tensors will become highly
heterogeneous (while it is ok to use it in the regular packing you have
now), then you will need spatial averaging of some sort and sufficiently
high discretization level for those local averages to be doable in small
regions (compared to problem size).

>And the main question is still the same: How to get something similar
to Ansys results with Yade?

To me it is still not very clear what/why you think is wrong after a quick overview of all above messages. Basically, the solution (displacement and forces - converted into strain/stress if you like) for such regular array can be derived with paper and pen, so I would suggest to divide in two sub-problems:
P1- Does the analytical match ANSYS (certainly not since a sphere array is not isotropic)?
P2- Does DEM match the analytical expressions? If not there can be a mistake in the definition of boundary condition,  a non-static state, or something like that.
For the moment it is not clear if you struggle with P1, P2, or both of them. It makes the problem solving difficult.
I understand you'd like a step by step answer on how to do things but there is no well posed problem yet in my opinion.

After reading the last messages I recognize I'm still a few steps behind
Jan, so you can waste my reply maybe. :)

@Jan
Ok for diagonal interactions, I didn't notice. It is indeed more isotropic, but on another hand isn't it what explains the special trend of stress on free boundaries? This boundary effect is still a problem in my eyes (half stress where force is applied is ok, it is a post processing artifact).

Bruno

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