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[Jérôme Duriez <question264456@xxxxxxxxxxxxxxxxxxxxx>]

Question #264456 on Yade changed:
https://answers.launchpad.net/yade/+question/264456

    Status: Open => Answered

Jérôme Duriez proposed the following answer:
My current feeling is that your spherical aggregate explodes because of
repulsive contact forces between the spheres inside the aggregate,
depending on this "gap" parameter (I never used pack.regularHexa though,
so I hope not telling any mistake).

It is in the end a little tricky to follow your method and your goal
since you showed us (in the first version) a working script where there
was no problem. Changing the "young" parameter in this first version
would not lead to any problem I guess (especially if GSTS engine is
used)

Changing "gap" is another issue, but it can not be an attempt to solve
any problem (since there was no problem in this first version..)


Anyway, for you to understand fully what's going here, my proposal would be :
- start from your first version

- play with the "gap" parameter to see if, indeed, repulsive contact forces appear or not between the spheres inside the aggregate. To analyze the situation more easily, just fix the spheres so that there is no explosion in any case
for b in O.bodies:
   b.dynamic = 0
You know now one command to analyze contact forces. You may also use graphical ways, it is a popular question, e.g. https://answers.launchpad.net/yade/+question/266460

- in case this confirms initial repulsive forces are the reason for explosion : do you need such gap values leading to initial repulsive forces ?
     * Yes : Re-give a close look to this phys.unp, asking us a precise question about that, in case you can not use it
     * No : you do not have any problem, just go ahead with the gap value of your first version.


Maybe, or maybe not if my current feeling is wrong, this method could solve your problem. In any case, you would learn a lot about Yade and this "gap" parameter doing this.

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