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Re: [Question #695154]: Polyhedra contact instability (potential Bug?)


Question #695154 on Yade changed:

Karol Brzezinski posted a new comment:

thank you for providing those top-notch papers! They are very general
and formalized, so I have only skim-read them. My intuitive idea seems
to be similar to the solution presented in the paper of Prof. Feng [1]:
"(...) The above conclusion has a sound physical explanation: if the
current contact state is fully described by a contact tenergy function
w, the true contact force and moment at the state will reduce the
contact energy most effectively or at the greatest rate, i.e. along the
negative gradient direction of w."

The main problem is the calculation of the contact energy function - w.
As I said, his approach is more general and can be applied to
'arbitrarily shaped particles'. Still, I think that the 'maximum area
polygon approach' presented above, can be a solution of a special case:
convex-shaped polyhedra :)

I also agree that if only contacts were more stable, the polyhedra would
be unbeatable for many applications.


I do not know if the proposed solution can be easily interpreted in 2D.
However, we can benefit from the simplicity of your 2D sketches and stay
in 3D space, by assuming axisymmetry. In all of the proposed cases, the
hull intersection of the contact will be a circle. This circle projected
on any plane other than horizontal would be an ellipse with an area
smaller than the area of the circle. So, it leaves only one choice of
the normal contact direction :)

Best wishes,

[1] https://www.sciencedirect.com/science/article/pii/S0045782520306393

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