[Yade-users] [Question #700748]: how to calculate the plastic part of shear displacement in law2-cohesionMoment

[Huang peilun]

New question #700748 on Yade:
https://answers.launchpad.net/yade/+question/700748

Hi,
I want to calculate the plastic shear displacement of any specific contact 
during every time step. I'm using Law2_ScGeom6D_CohFrictPhys_CohesionMoment[1]. 
In the source code, the plastic displacement is calculated by the following 
code (L140-L159):

Vector3r&   shearForce = geom->rotate(phys->shearForce);
const Vector3r& dus= geom->shearIncrement();

//Linear elasticity giving "trial" shear force
shearForce -= phys->ks * dus;

Real Fs= phys->shearForce.norm();
Real maxFs = phys->shearAdhesion;
if (!phys->cohesionDisablesFriction || maxFs == 0) maxFs += Fn 
* phys->tangensOfFrictionAngle;
maxFs = math::max((Real)0, maxFs);
if (Fs > maxFs) { //Plasticity condition on shear force
if (phys->fragile && !phys->cohesionBroken) {
phys->SetBreakingState();
maxFs = max((Real)0, Fn * 
phys->tangensOfFrictionAngle);
}
maxFs   = maxFs / Fs;
Vector3r trialForce = shearForce;
shearForce *= maxFs;
if (scene->trackEnergy || traceEnergy) {
Real sheardissip = ((1 / phys->ks) * 
(trialForce - shearForce)) /*plastic disp*/.dot(shearForce) /*active force*/;

Briefly, the plastic shear displacement is calculated by 1/ks*(trialForce - 
shearForce). However, it seems trialForce is not available during the 
simulation process. Though shearInc is available, which is dus in the source 
code, it is not exactly the same as 1/ks*(trialForce - shearForce). Therefore I 
want to ask if there is a simple way to get the plastic shear displacement 
instead of modify the source code?

Thank you!

[1] 
https://gitlab.com/yade-dev/trunk/-/blob/master/pkg/dem/CohesiveFrictionalContactLaw.cpp

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Re: [Yade-users] TODO-List for Yade

[Janek Kozicki (yade)]

Thank you Anton for creating this list. I have just added a few more
items there, including some ideas which I had in mind for a long
time. Some of them are difficult, but doable.

https://gitlab.com/yade-dev/trunk/-/issues/251

This is the TODO list at which my students will start looking at on
March 1st (in only three days). And they have to decide which item to
pick on March 15th. A bit unlucky timing, because that's just a day
before our yade-dev meeting.

They will be working in groups of 3 to 5 and they have 10 months to
complete the task. They are not forced to pick items from this list -
they can have some other unrelated ideas to work on. But we can
provide them with nice ideas, hoping that they will pick something
from this list.

If you want to add something NOW is the time. I recall that Klaus
mentioned, that you needed some students who finished a full C++ course?
That's these students. So now you can add items to this list :)

best regards
Janek

Anton Gladky said: (by the date of Sun, 20 Feb 2022 14:47:45 +0100)

> Dear all,
> 
> As discussed during the last meeting of yade-devs, I have prepared
> a list of TODO-tasks [1] for Yade, which can be completed during the student
> works, Google summer of code and other similar contests and springs.
> 
> Feel free to add new ideas (even crazy ones!) into this list. If somebody
> will work on the particular task, it will be separated into the extra-task to 
> be
> tracked.
> 
> [1] https://gitlab.com/yade-dev/trunk/-/issues/251
> 
> Thanks and best regards
> 
> Anton
> 
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-- 
--
Janek Kozicki, PhD. DSc. Arch. Assoc. Prof.
Gdansk University of Technology (Gdansk Tech)
Faculty of Applied Physics and Mathematics
Department of Theoretical Physics and Quantum Information
--
http://yade-dem.org/
http://pg.edu.pl/jkozicki (click English flag on top right)

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