# yade-users team mailing list archive

## Re: Re : Triaxial Test

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```If you generated a
simulation where you have 1 box, filled with spheres inside, it would all
totally explode, because spheres would behave is if they were INSIDE a
solid box.

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```But... I thought ImpactTest was generated using a box...
Ok, I see : in fact it uses 6 boxes...
```
There is a simpler way to represent a wall-boudary : a finite or infinite plane, no need to assign it mass/thickness, stiffness is enough. I had almost the same idea when I thought to _*one*_ box for the triax. I will probably implement one of the two solutions (if not both) in the future.
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```First (simplest
approach) will add Stiffness without checking whether it is a sphere or
a wall, so all spheres will also have their total contact stiffness
summed, not only the walls.

```
In fact the total contact stiffness of a sphere is needed to compute accuretly the critical time-step (Tc). I remember I was a bit puzzled when I looked how Tc is currentmy computed in Yade (but I can't remember exactly). So, perhaps it is not a bad thing after all to compute the total stiffness of spheres. The method I know to evaluate Tc is based on the matrix Mij so that dRi = Mij*Uj (where Ri is the resultant and Uj the displacement of the sphere).
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```3. once you have Stiffness in physicalActionContainer - you can access
it from you DeuxEx just like you can access Force.

this was a brief explanation of the idea which I have in mind. tell me
```
if you understand it :)
I understand the overall idea, but I am not sure I understand precisely this line (from ForceEngine.cpp) :
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```
static_cast<Force*>( ncb->actionParameters->find( b->getId() , actionParameterForce->getClassIndex() ).get() )->force += force;
```
Could you comment a bit on this?

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```I feel a small temptation to do it myself,
because it's interesting. But I have also other work to do (lattice and
documentation).

```
I must learn to do the job myself. If not, I will never take advantages from using Yade :).
```Your help is invaluable, it should be enough :).

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```it is
easier to modify .pro files by hand (for example with F4 from mc), than
to edit them with kdevelop3. (kdevelop3 displays scopes in a weird
manner, so better ignore it - I hope that they will fix this in near
future).
```
```"F4 from mc" ???!

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```As a general rule - when you work with yade - it is better to add new
classess than to modify existing ones :).
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Of course. When I say "modify" (previous mails), I think copy/paste in new file and modify.
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```
```"Error: Could not open /dev/nvidiactl because the permissions
```
I know how to solve it temporarily (chmod on OGL files each time I start a KDE session).
```I just change
/nvidia*:root:video:0660
/
to
/nvidia*:root:video:0666/
in udev.permissions. It should fix the problem (I did not check yet).
```
```Do you have an idea if this may be due to Yade?!
```
```

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In fact it does not apparently :-(.
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I will try what you recommend. But note that the problem is still here after I uninstalled the last version and re-installed the "official release".
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--
_______________
Chareyre Bruno
Maître de conférence
Institut National Polytechnique de Grenoble
Tél : 04.56.52.86.21
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________________________________________ bureau I 08 Laboratoire 3S (Soils Solids Structures) BP 53 - 38041, Grenoble cedex 9 - France _______________
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