yade-dev team mailing list archive

[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

> Hi Vaclav and Bruno,
>
> I've got just one short comment (it could help... or not...):
> To avoid log, you could basically compute the natural strain as the sum of the increment strain at each time step.
>
>   
Hi Vincent,

This is more or less what we do already.
At each step (Cell.cpp l.5) :

//incremental displacement gradient
   _trsfInc=dt*velGrad;
   // total transformation; M = (Id+G).M = F.M
   trsf+=_trsfInc*trsf;

Or, say, Ftotal=Fn*Ftotal, with Fn the transformation at iteration n.

We don't directly compute eps incrementaly in 1D like below, however; no 
need, and I don't know how it could be done in the general case, or in 
e.g. simple shear (stretch applied on a continuously rotating material).

At any point, we simply get eps_xx=Log(F_xx) for a triaxial loading or 
eps_ii=Log(U_ii), with U the stretching part of F=RU and "i" an eigen 
vector (the last part is in code I did not commit).

Bruno

> eps = sum deps
>
> so that (in 1D)
>
> eps = sum  dl/l  /simeq dl/l0 for  small strain
>                             /simeq log(1+dl/l0) for large strain
>
> Vincent
>
>
> _______________________________________________
> Mailing list: https://launchpad.net/~yade-dev
> Post to     : yade-dev@xxxxxxxxxxxxxxxxxxx
> Unsubscribe : https://launchpad.net/~yade-dev
> More help   : https://help.launchpad.net/ListHelp
>
>   


--

_______________
Chareyre Bruno
Maître de Conférences

Grenoble INP
Laboratoire 3SR - bureau E145
BP 53 - 38041, Grenoble cedex 9 - France
Tél : 33 4 56 52 86 21
Fax : 33 4 76 82 70 43
________________