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[Luc Scholtès <question290129@xxxxxxxxxxxxxxxxxxxxx>]

Question #290129 on Yade changed:
https://answers.launchpad.net/yade/+question/290129

Luc Scholtès proposed the following answer:
Thanks Bruno for your answer.

As I said, I probably missed something since, in the version I use, the
external work is only computed in

TriaxialStressController::controlExternalStress()

with this line:

externalWork +=
previousTranslation[wall].dot(getForce(scene,wall_id[wall]));

Then, according to these lines in TriaxialStressController::action(),
externalWork is thus computed only when the walls are stress controlled
(these are the lines for bottom wall only, the same structure applies
for all other walls):

if (wall_bottom_activated) {
			if (stressMask & 2)  controlExternalStress(wall_bottom, wallForce, p_bottom, max_vel2);
			else p_bottom->vel[1] += (-normal[wall_bottom][1]*0.5*goal2*height -p_bottom->vel[1])*(1-strainDamping);
}

In order to have the external work computed under strain control, I had
to modify the code according to the following lines:

if (wall_bottom_activated) {
			if (stressMask & 2)  controlExternalStress(wall_bottom, wallForce, p_bottom, max_vel2);
			else { p_bottom->vel[1] += (-normal[wall_bottom][1]*0.5*goal2*height -p_bottom->vel[1])*(1-strainDamping);
			 // LS: update of external work?
			 externalWork += (p_bottom->vel.dot(getForce(scene,wall_id[wall_bottom])))*scene->dt;
			}

Without this change, I just cannot explained where the elastic energy
that is stored in my sample during the deviatoric phase is coming from.

So, 2 possibilities here:

1) I miss something conceptually for not considering these additional lines (and then no work is produced when walls are strain controlled) -> this is why I ask if I missed something
2) I use an outdated version where the external is only computed in ControlExternalStress (my version is not the latest one)

In any of these 2 cases, I just cannot verify the energy balance in my
system and I will then stick to my changes to do so.

Unless you have another explanation?

Thanks

Luc

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