yade-users team mailing list archive

[Jerome Duriez <jerome.duriez@xxxxxxxxxxxxxxx>]

Hello Chiara,

From a very general and quite simple (or the contrary...) point of 
view, you can give a look to the two attached figures, if you ask you 
questions about time steps. It deals about a simple mass (m)-spring (k) 
system (with constitutive laws similar as those we use, thus).
The figures show the evolutions of this system (including the one of the 
total mechanical energy), as it is planned with a discrete (with respect 
to time) scheme. The influence of the value of the timestep (which is 
compared to tc = sqrt(m/k) ) appears quite well.
I guess nothing more complicated is required to let you understand for 
example that you have to use tangential stiffnesses, as Vaclav told you.

chiara modenese a écrit :
> Hi all,
>
> I am having some thoughts about the suitable time step to choose in a 
> simulation. A the moment in Yade we have two (three) possibilities:
>
> 1) PWave time step (could you give me some references on this, please)
>
> 2) GSTS
>
> 3) A fixed constant value set by the user
>
> Now I am not sure that for the explicit scheme we are using and for 
> the case of non linear relationship between forces and displacements 
> (that is of my interest) we end up with the critical time step for the 
> system using one of the above. Has anyone tested this aspect before? 
> Do you have any references to suggest me that eventually touch this 
> issue (if any)?
> I am not even sure why, if I use the GSTS, I should give the 
> tangential stiffnesses and not the secant values as input.
> In summary, do you see any limit of applicability for the use of GSTS?
>
> Thanks for your comments,
> Chiara
>
>
>
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--
Jérôme Duriez
ATER Iut 1 Grenoble, département GMP - Laboratoire 3S-R
04.56.52.86.49 (ne pas laisser de messages sur le répondeur)