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[Chareyre <question256400@xxxxxxxxxxxxxxxxxxxxx>]

Question #256400 on Yade changed:
https://answers.launchpad.net/yade/+question/256400

    Status: Open => Answered

Chareyre proposed the following answer:
On 31/10/14 10:46, Mario Reyes wrote:
> I think the script you are referring me to is this
> https://github.com/yade/trunk/blob/master/examples/test/periodic-simple-
> shear.py.
Yes and no. Better don't download scripts from internet, they may be no
compatible with the version of yade you are using.
When you install yade (and depending on how you do it) the example
scripts are installed somewhere on your hardrive (you can use the
"locate" command).

>  I understand that I can can set my required stress or strain
> through the parameter "goal", in every direction. If stress or strain is
> specified depends of "stressMask", but I have been checking the mailing
> list and the PeriTriaxController class reference and I don't understand
> how to set stress or strain through "stressMask".

Please read the explanations in examples/triax-tutorial/script-
session1.py

> I got more confused with the following lines in the documentation:
>
> "The following creates periodic cloud of spheres and compresses to
> achieve \sigma_x=-10 kPa, \sigma_y=-10kPa and \eps_z=-0.1. Since stress
> is specified for y and z, stressMask is 0b011 (x→1, y→2, z→4, in decimal
> 1+2=3)"

I don't understand it very clearly either... please see script-
session1.py

> I also have problems to understand the meaning of the parameter
> "relStressTol".
It defines how much stress can deviate from the target value for
considering that target is reached.


>  Finally, in the same example script this line is
> present:
>
> O.cell.velGrad=Matrix3(0,6,0, 0,0,0, 0,0,0)
>
> Just before the conditions for the shearing. I think it is related to
> the periodic boundary conditions, but I am not sure. If you can give any
> insight in these topics would be of great help. Thanks again for your
> answer.
Since periodic boundaries are actually not boundaries, we need to define
deformation as a mean-field quantity.
The component "xy" of the velocity gradient (the one with the value 6)
is the constant shear rate.
BTW, this is the classical velocity gradient called "simple shear" that
you see here.
Yet the component "zz" will not be constantly zero. It will be adjusted
dynamicaly as soon as you impose a stress in "zz".

Bruno

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