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[Kieran Fung <question691584@xxxxxxxxxxxxxxxxxxxxx>]

Question #691584 on Yade changed:
https://answers.launchpad.net/yade/+question/691584

Kieran Fung posted a new comment:
Hi Jan Stránský!

I'm hoping to hi-jack this question thread and expand upon the amazing
discussion you and Lei Hang have had above. Seriously, the above
conversation was an amazing review of the opensource code.

To start off my questions, why does the code first simulate a constant
isotropic compression of O.cell.velGrad=Matrix3(-.1,0,0, 0,-.1,0,
0,0,-.1)?

Does this step ultimately cause the periodic boundary condition to be
flush with the particle regularHexa pack? Because without it, the
periodic boundary condition seems to simulate a regularHexa pack within
the representative volume element but it is suspended inside of it at
iteration 0.

I am asking because I am interested in a periodic simple shear
simulation as well ... I just cannot connect the dots on why this step
is logical. Is isotropic compression necessary prior to the simple shear
of O.cell.velGrad=Matrix3(0,0,.1, 0,0,0, 0,0,0)?

Another question I have is about the section:
plot.addData(exz=O.cell.trsf[0,2],szz=stress[2,2],sxz=stress[0,2],tanPhi=(stress[0,2]/stress[2,2]) if stress[2,2]!=0 else 0,i=O.iter)
	# color particles based on rotation amount

The outputted data takes on the form (via columns):
#        exz      i      sxz     szz     tanPhi

Based on the conversation above, I recognize that sxz = shear stress in the xz plane and szz = normal stress in the zz direction.
I am confused about exz, i, and tanPhi:

To my understanding, exz represents the current transformation matrix of
the cell at the given iteration step. Would this definition be analogous
to the cell strain or deformation at a given time step?

I am fairly lost on what the data column 'i' could represent - so no
guesses there.

Finally, I am curious about tanPhi. For my simulations I have the particle rotations blocked via:
b.state.blockedDOFs='XYZ'
Why is a change in angle being outputted when the rotational DOFs are being blocked? Does tanPhi represent something else here?

Thanks for all of the help Jan. Your assistance has and always is,
greatly appreciated.

Cheers,
Kieran

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