Question #163253 on Yade changed:
https://answers.launchpad.net/yade/+question/163253
Status: Open => Answered
honzik proposed the following answer:
Hi Janaka,
>1. Why I don't get stress 0 at time=0 during isotropic consolidation
>(hydrostatic pressure) when I run peri3dController_triaxialCompression.py with
>the parameters as given below (It seems that there is 300kPa pressure at t=0,
>I don't know how this high pressure is applied at t=0).
The pressure is probably because of residual stress from packing phase of
simulation (the initial packing is not "stress-free"), maybe someone else could
confirm this?
>2. Its also not clear why stresses in xx and yy directions change during axial
>compression (those should be constants).
In the case of periodic cell, we cant (or at least I dont know about it)
prescribe stress directly, so we estimate deformation such that the stress is
as close as possible to the prescribe value. The smaller is the time step, the
smaller should be the difference between actual and prescribed stress.
>3. How can I change/know strain rate? It seems the original script attached
>herewith doesn't have any parameter to change strain rate. Is that so?
in O.engines there is Peri3dController(....,label='p3d'), so you can use this
label to acces Peri3dController values, i.e.
strainRate = p3d.strainRate
The strain rate is updated automatically to satisfy prescribed goal values.
>4. Whats stressMask? How is stressMask related to goal?
Stress mask determines in which components is prescribed deformation and in
which components is prescribed stress (although not directly as mentioned
above). 0b000011 means prescribed stress in xx and yy direction and prescribed
strain in all other directions. The format is 0b(txy)(tzx)(tyz)(szz)(syy)(syy)
where instead of (..) you write 0 (for prescribed strain) or 1 (for prescribed
stress). Google python binary format for more details if you are interested..
Goal is prescribed value at the end of simulation, corresponding to stress or
strain declared in stressMask
>5. How can I access to original data of the tests (here, I just see graphs but
>I prefer to take data and use them in my analysis)
The data are stored in plot.data
>6. Are there any publications used peri3dController_triaxialCompression.py
>script to test triaxial tests?
I wrote this example script to demonstrate basic usage of Pari3dController, but
I think there is no serious publication using this specific file..
Hopefylly at least some of my explanations are understandable :-)
Regards
Jan
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