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[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

Anton Gladky a écrit :
>     If we look at the triaxial, for instance, in the triaxial phase we
>     apply a load on the upper wall to compress the specimen and if we
>     check the stresses at the bottom wall, they are more or less the
>     same (if the strain rate is small enough).
>
>
> I think, if we have a large difference in force between bottom and 
> upper surfaces, dt should be decreased till it become more-less equal.
>   
dt will not change anything. Loading rate will (numerical vs. physical 
parameter, the problem here is Newtons law, not numerical errors).
The easiest way to check that you are looking at quasi-static (i.e. 
non-dynamic) response is to use Shop::unbalancedForce (IIRC, I don't 
have any linux in front of me atm). If it is less than 0.01, you can 
consider it is ok for basic tests. For scientific results you need even 
less in most cases.
When you show stress-srain responses in DEM, you must always proove that 
the result is not rate dependant. Many published papers could go to 
trash just because people picked an arbitrary value of loading rate and 
never checked more. You gave a very good exemple of possible flawed 
conclusions : different results in tension and compression.


Bruno