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[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

Hi Vaclav, I have big connection problems here. I couldn't do much. I'm 
commiting before next disconnection.
> > meanStress = ...
> > isoVelGrad += dt.(goal - meanStress)/mass;//or the "stiffness" one
> > velGrad[0][0] = velGrad[1][1] = velGrad[2][2] = isoVelGrad;
> >     
> I wanted to introduce matrix that would express the cross-dependencies.
> It would also make it possible to apply strain where εe=.5εy and so on.
>
>   
I finally found this "old" mail (12/08/09) :

> > For instance: goal=(1e6,0,0.1), computed variables comp=(σx,σy,εz), i.e.
> > stressMask=3 (first 2 components are stress, the last one is not)) and
> > the matrix

> > 1  0 0 
> > 1 -1 0
> > 0  0 1

> > then the system comp=M*goal gives

> > σx=1e6
> > σy=σx
> > εz=0.1.


One remark : implementing this for arbitrary deformation needs 9 
"goals", compared to 9 components of F or stressTensor. A typical 
example : compression along z axis with imposed dεzz/dt while σxz is 
kept constant (i.e. velgGradxz will be assigned by the engine to keep 
sxz constant, and velGradzz will be defined to make log(Fzz) reach goalzz ).

One question : how can it be adapted to isotropic compression, where 
goal is (sx+sy+sz)/3 and the constraint is ex=ey=ez?

>>(BTW don't look at the stiffness computation there, it is wrong, I know;
>>the average stress is right, though)

This is why I implemented cell inertia. Did you fix this or it was not 
really a problem?

>>Well, I still managed to separate them ;-) If you normalize transformed
>>axes, then transformation from physical (normalized) axes to the
>>transformed ones is just shear and rotation without scaling. It is Hsize
>>with columns normalized (as vectors), if you wish.

I'll have a look. I'm curious.
If you apply a (non-isotropic) scaling on normalized Hsize vectors, it 
will "shear" them (the angles between axis will change), right?

Bruno






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