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[Robert Caulk <question675377@xxxxxxxxxxxxxxxxxxxxx>]

Question #675377 on Yade changed:
https://answers.launchpad.net/yade/+question/675377

Robert Caulk proposed the following answer:
Hello Mehdi,

Ok, thankyou for clearly elaborating. It seems you might be confused
about the definition of the transformation matrix in this case. Here,
O.cell.trsf, is the deformation gradient which can be used to determine
strain, but by itself simply gives you a transformation from one state
to another.

If you want to pull the natural strain from the deformation gradient,
you would do something like:

strain = .5*(O.cell.trsf+O.cell.trsf.transpose()) - I

which is conveniently provided for you as O.cell.getSmallStrain() [1].

Now, if you want the velGrad to reflect equal rates in dv_x/dy and
dv_y/dx, you will need to add that:

O.cell.velGrad=Matrix3(0,rate,0, rate,0,0, 0,0,0)

Please let me know if this answers your question or not :-)

Cheers,

Robert

[1]https://yade-
dem.org/doc/yade.wrapper.html#yade.wrapper.Cell.getSmallStrain

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