*** This bug is a duplicate of bug 399963 ***
https://bugs.launchpad.net/bugs/399963
** Changed in: yade
Status: New => Invalid
** This bug has been marked a duplicate of bug 399963
TriaxialTest gives different results with ScGeom and Dem3DofGeom, cause is
not known
--
strange effects of Law2_Dem3DofGeom_FrictPhys_Basic in dense periodic packings
https://bugs.launchpad.net/bugs/585771
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Status in Yet Another Dynamic Engine: Invalid
Bug description:
I made comparisons between Law2_Dem3DofGeom_FrictPhys_Basic and
Law2_ScGeom_FrictPhys_Basic in periodic triaxial tests. Damping was very law
(2%), 400 spheres with identical positions.
The result is attached. You'll see in gray the curve of unbalanced force for
ScGeom, resp. pink for Dem3Dof.
Different stress curves is ok, we can get almost the same difference between
identical simulations in multithread (here, everything is run in 1 thread).
The surprising thing is unbalanced force is exploding, even with very low
strain rate, after enough deformation, even though the same unbalanced force
can go as low as 1e-8 in the initial isotropic compaction. I could repeat that
with different number of spheres and different dampings.
With ScGeom, unbalanced force stagnate at very low value (so close to x-axis
that you just see a few picks), exactly as what we would have with rigid
boundaries.
Carefull examination and comparisons with usual DEM results on spheres show
that the evolution of stress and porosity is impacted by this growing
instability (the inverse would be surprising).
I have no real explanation for this. The only thing comming to mind is
ratchetting (guess why the doc. has been updated...) but I'd give it a 10%
chance only.
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