yade-users team mailing list archive

[Chiara Modenese <chiara.modenese@xxxxxxxxx>]

Thanks Bruno, now I understand.

Chiara

>----Messaggio originale----
>Da: 
bruno.chareyre@xxxxxxxxxxx
>Data: 20/01/2010 9.47
>A: <yade-users@lists.
launchpad.net>
>Ogg: Re: [Yade-users] I: Re:  Porosity
>
>
>> Question: which 
value of friction angle do you use during the 
>> compaction phase? Should be 
the final one or should be lower than 
>> that? Would it be possible to run the 
analysis with a value equal to 
>> zero?
>>   
>Anything between 0 and the 
final value. Higher than the final value 
>would result in volumetric collapse 
at the beginning of the test.
>
>>  I would expect that also at a small level 
of stress on the walls, 
>> this value of unbalanced force remains quite low.

>unbF is non-dimensional, it is not affected by the level of stress. See 
>it 
as a percentage of the loading.
>
>>  I suppose that the reason you (if it were 
you) put the bool 
>> isARadiusControlIteration relays in the concept of 
maintaining a 
>> quasi-static equilibrium as much as possible during the 
analysis.   
>I see the problem now.
>The point of cycling without expanding is 
just to speed up the 
>simulation. Increasing sizes need an iteration on all 
bodies, and one on 
>interactions. It is expensive. Increasing by 1e-5 at each 
step is more 
>or less like increasing by 1e-4 each 10 steps, so...
>

>Actually, unbF _should _be close to 1 during the begining of the growth, 

>since most particles have 0 (unbF undefined) or 1 contact (unbF=1, since 
>the 
resultant force IS the contact force in this situation). The only 
>time when 
you really want it low is at  the end of the compaction. I 
>don't really care 
if the compaction is dynamic in between, and for sure 
>the interval between 
growth is too small to let the sample really 
>stabilize.
>> To make a summary 
I see that the unbalanced force reaches low values 
>> (say 0.07 or whatever) 
only after having compressed the packing. Am I 
>> escaping something?
>>
>>   

>That is correct and expected. Gaz particles can't be at static 
>equilibrium 
under pressure, dense packings with many contacts can.
>
>Cheers.
>
>Bruno
>
>

>
>
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