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[weijy <question404135@xxxxxxxxxxxxxxxxxxxxx>]

Question #404135 on Yade changed:
https://answers.launchpad.net/yade/+question/404135

    Status: Answered => Open

weijy is still having a problem:
Thank Jan Stránský  for carefully reading and testing the scipt. I was
hoping to provide a script that can easily run, so the key parts
relavent to intR may not seem emphasized. By "before reset intR" in the
script, I actually meant "before setting intR to 1.25", sorry for the
language mistake :D

To prevent confusion may I confirm this sentence:"So you will get actual
number of interactions in set_interactions() function, but the number
will be before reset of intR".  The number of interactions I get in
set_interaction() function is the number of interactions when intRadius
is 1.25, is that right?

In fact I've also noticed the 4500e10 matter. Just as Jérôme Duriez
pointed, I ran  a small script, in which 6 spheres(CohFrictMat) are
ranged like a  2*3 matrix. Two of them are bigger than others and are in
contact with each other even when intR is 1.0. Other four spheres are
smaller, do not touch any other spheres at the very beginning. So if
intR is 1.0, only two big spheres are in contact, num_intr is
1("num_intr" is short version of"number of interactions", and "intR" is
short version of "intRadius")

So I set the intR big enough for the smaller spheres to contact and count num_intr, it still remains 1. No new contacts are created. I tried by adding "setCohesionNow=True" when intR is altered, SOMETHING happens:
1. If normalCohesion of the material is a smaller value(like 4500), still nothing.
2. if normalCohesion is bigger(like 450000), two new contacts are created between the bigger sphere and the nearest small sphere. And the small spheres will be "stick" to the bigger ones.
3. If normalCohesion is even bigger(like 500000), five new contacts are created between all neighbouring spheres. And they are all "stick" together after setting cohesion.

I've got two questions about this phenomena:
1. Why is contact detection rely on mechanical behavior(In this case different normalCohesion value affect interaction number)?
2.  In my understanding, setCohesionNow() merely set a maximum tensile strength between two particles(not a strength, but a maximum strength value), but in this occasion, after setting cohesion, some "strength" are generated between particles, why is that?
As a first guess, this phenomena may have something to do with the CohFrictMat I used. Is there an "expert" in this material who can explain this?

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