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[Luc Sibille <luc.sibille@xxxxxxxxxxxxxx>]

Václav S a écrit :
>> Ok. It makes sense in concrete (I guess you will define an equilibrium 
>> position with interpenetration!=0 then?), but - generally speaking, it 
>> is not necessary to create cohesion between distant bodies in order to 
>> simulate a cohesive material, cohesion at contacts is sufficient.
>>   
> Your spheres have some microscopic young's moduli, but due to the
> disctribution of interactions you get macroscopic modulus that can be
> different; and I want to compensate that). I want to make sure that
> given a plane, sum of "surfaces" of all interactions (cylinders between
> spheres with the radius of the smaller sphere, right?) is equal to
> nominal, macroscopic surface of specimen. It depends on sphere radii
> discribution, for sure; perhaps it can be calculated analytically for
> regular arrangements. For other cases, the simulated rigidity may be
> artificially higher/lower. I haven't tried to quantify that yes, though.


If I understand what you mean, you want to compute analytically the 
macroscopic young modulus as a function of the microscopic young 
modulus. I am not sure there is currently a general way to do that for 
random assembly, it is not easy at all. There were formula like that in 
SDEC: the input was a macroscopic young modulus and SDEC computed 
automatically the microscopic young modulus attributed to each 
particles. But in reality it didn't work, the macroscopic young modulus 
wanted was not reached.
The formula used were based on a paper from Cambou, but the formula, I 
think, were valid only for a given fabric corresponding to the ones 
studied by Cambou.
You can find more details in the PhD thesis of Sebastien Hentz who used 
all that to simulate concrete with SDEC (in which there was a radius of 
interaction greater than 1). In addition maybe you will find help about 
interaction laws to use etc... in this thesis, unless you have already 
read it.

   Luc
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