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
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