yade-users team mailing list archive

[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

I developped the TriaxialCompressionEngine, precisely, to solve the 
problem that you explain here.
This engine can still be made a lot more versatile. But, its purpose is 
to handle transitions between different loading paths, and to be easily 
configurable by editing the xml.
If you edit the xml, and - for instance - change manually the value of 
sigma_iso, the packing will converge to a different confining pressure. 
If you play with other flags/values you can also fix some walls, or 
launch a compression test (or extension if the strain rate is set negative).
If you want to simulate some loading paths and you think you can't with 
the current engine, it means you have to code some new features in 
TriaxialCompressionEngine source code (example : proportional strains 
test). In that case, I suggest that you tell me what you need to do and 
we decide how to implement it (which should be relatively easy based on 
what already exists). Note that, at the end, you (or me) can commit the 
change to svn.

Remark1 : TriaxialCompressionEngine can, by default, compress a packing 
and start a compression test when the assembly is dense and stable. You 
can run a first simulation in compression, then edit the intermediate 
file that is saved at the end of the compaction stage, change  
strainRate=x to strainRate=-x, and run the extension test.

Remark2 : The save/edit/modify/load procedure is not exactly 
user-friendly... It would be usefull sometimes to change the loading 
path, or anything else, in real time, in one simulation. Vaçlav is 
developping something to do this from a command line. It probably works 
already. It means that we can completely avoid the load/save operations 
if we use this feature.

Remark3 : Vaçlav is also working on the triaxial engines now for his PhD 
research, so he will probably participate in the future discussions 
about this. Janek is also starting to use those engines for simple 
compression (no lateral stress) on snow. I guess you just dived in at 
the right moment. :)

Bruno


Luc SIBILLE a écrit :
> Hi,
>
>  First, I am discovering Yade, so I think I will have a lot of questions...
>
> By looking the structure of the file called scene.xml (created, for
> instance, by the generator TriaxialTest), I understand that in the same
> file are defined  the media (the bodies, here spheres) with the
> geometrical and physical (or mechanical) properties and the simulation
> that we want to perform (with is specific parameters).
>
> My problem is the following one: a given simulation is linked here to a
> given media, so can we do different simulations from a unique given media
> ? I give an example here after based on a triaxial test:
>
> I perform an isotropic compression, after I stop the simulation and save
> the result. I don't go further because I want to do different things with
> this consolidated granular assembly.
> Then I want to do a compression and an extension both from the state of
> the media after the isotropic compression. So I perform a first simulation
> (the compression) by using the consolidated granular assembly (the result
> saved), then I perform a second simulation (the extension) by using the
> consolidated granular assembly (always the same result saved).
> I imagine that I cannot do that with Yade since the kind of simulation is
> saved in the scene.xml file and reused (here the simulation "isotropic
> compression" is saved and reused whereas I want to perform a "compression"
> or an "extension").
>
> Am I right ? What would be the different steps (in few words) to perform
> the simulations described above?
>
>   Best,
>
>    Luc
>
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>
>   


-- 
 
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Chareyre Bruno
Maitre de conference

Institut National Polytechnique de Grenoble
Laboratoire 3S (Soils Solids Structures) - bureau E145
BP 53 - 38041, Grenoble cedex 9 - France
Tél : 33 4 56 52 86 21
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