yade-users team mailing list archive

[Václav Šmilauer <eudoxos@xxxxxxxx>]

> On my side, I have tons of files with coordinates of sphere packings. 
> But at the end, you will probably find something that you don't like in 
> them, and you will want to generate your own packings.
>   
> TriaxialStressController can be used for generating packings. It can 
> either 1/ squeeze the packing by moving boxes or 2/ fill the volume by 
> increasing the size of elements.
>   
I will try to find out how it works... There is bunch of Triaxial*
classes and so far I am not quite sure how to use them. Would you mind
describing their interaction at wiki?

Can you send me a few (like 4) sphere packings so that I have something
to start with?

My goal is to have somewhat automated calibration procedure, at least
for elastic properties at the beginning.
>> I will work soon on triax test which will have "true" hydrostatic
>> confinement (by using delaunay to detect the solid edge and applying
>> forces at relevant spheres) 
>>     
> Very interesting!! We have a small-scale project here to compare 
> different types of boundary conditions (periodic, walls, membranes, 
> compression/shear, loading rate, etc..) your "true" confinment can be 
> one more thing to compare.
>   
Are you implementing periodic BC in yade? I had a few ideas how to do
that, it would not be too difficult: some changes to the collider and to
the interaction dispatcher, that would be able to handle "phantom"
elements (periodic copies of existing ones) and their interactions with
real elements. I was facing the question whether to have just
xyz-periodicity or something more generic, that would allow axisymmetry,
for example. But it is no relevant to decide now.

And how about "minimum boundary conditions" we were discussing in Prague?
> For the Delaunay part, do you plan to do a real-time triangulation of 
> the packing? What library will you use? because I'm working on that at 
> the moment with the CGAL lib.
>   
For Delaunay, I am not sure. I thought trying VTK out, since it is a
possible migration path from wm3 (once it is not sufficient). Wm3 does
have Delaunay, but its interface is clumsy, I think, and wm3 itself is
not widely used. Too bad that cgal is not as whole under (L)GPL, as some
of its modules are restricted to non-commercial apps IIRC.

Supposing "small displacements", the triangulation would be done very
rarely, perhaps every 1e4 iterations or even just at the beginning. We
would have to try whether it converges. What is the principle of
membrane confinement? Isn't it the same as what I want to do?

Vaclav
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