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[Jérôme Duriez <question691785@xxxxxxxxxxxxxxxxxxxxx>]

Question #691785 on Yade changed:
https://answers.launchpad.net/yade/+question/691785

Jérôme Duriez posted a new comment:
> the normal stiffness coefficient "kn" in "PolyhedraPhys" can have a
variety of different units

Indeed, I missed this point.. This would greatly affect (and not
positively) the measure of packing-wall stiffness and stress servo
control by the engine.. TriaxialStressController needs true spring
force/displacement stiffness to work.. [*]

Maybe a simple solution could be to use bodies of Polyhedra shape, but stick with a classical FrictMat material (I do not know how much built-in functions for bodies creation, like utils.polyhedron or polyhedra_utils.polyhedra accommodate this behavior, but you can always create yourself the correct Body)  and FrictPhys interactions physics
Using classical ScGeom through Ig2_Polyhedra_Polyhedra_ScGeom might be necessary as well in the end (for picking an existing Law2)


As for the boundary bodies, I did not get whether you intend to use Box-shaped or Wall-shaped ones (both are possible with TriaxialStressController, just assign yourself TriaxialStressController.thickness = 0 if you want Wall s). But note that Wall-Polyhedra interaction has recently been updated / corrected [**]

(from a personal point of view, I can share I'm sometimes trying to play
with Polyhedra shapes at the moment, but never ran a triaxial test
myself. And I'm looking forward to feedback from other Polyhedra
users..)

[*] https://gitlab.com/yade-dev/trunk/-/blob/master/pkg/dem/TriaxialStressController.cpp#L73 and https://gitlab.com/yade-dev/trunk/-/blob/master/pkg/dem/TriaxialStressController.cpp#L99
[**] see the history at https://gitlab.com/yade-dev/trunk/-/merge_requests/502

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