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[Jan Stránský <question689542@xxxxxxxxxxxxxxxxxxxxx>]

Question #689542 on Yade changed:
https://answers.launchpad.net/yade/+question/689542

    Status: Open => Answered

Jan Stránský proposed the following answer:
well, then we need to dive into the source code :-)

(1,2)
normalStress is a name of spheresNormalStressVec variable [1]
spheresNormalStressVec is filled with stress variable [2] defined two lines above as bodyStates[b->getId()].normStress
bodyStates are filled with stress using getStressForEachBody. In that function [4], normalStress is computed as:
sum_interactionsOfTheBody 1/A * n.fN * n
Similarly for shearStress.
So no, it is not like bodyStressTensors command (although I cannot say quickly how much it will differ, you can test yourself)

if you are interested in the bodyStressTensors results, have a look at
"bstresses" export of VTKExporter [5]

(2,3)
forceVec ... spheresForceVec variable [6], filled with f variable [7,8]
So yes, it is overall force on the body (same as python O.forcec.f(id) )

torque is overall torque (or moment) applied on the body (O.forces.t(id) ).
E.g. for sphere-sphere contact it is computed as a sum form interactions contribution, roughly something like shearForce.cross(radius), so "length" is radius.

cheers
Jan

[1] https://gitlab.com/yade-dev/trunk/-/blob/master/pkg/dem/VTKRecorder.cpp#L297
[2] https://gitlab.com/yade-dev/trunk/-/blob/master/pkg/dem/VTKRecorder.cpp#L763
[3] https://gitlab.com/yade-dev/trunk/-/blob/master/pkg/dem/VTKRecorder.cpp#L671
[4] https://gitlab.com/yade-dev/trunk/-/blob/master/pkg/dem/Shop_02.cpp#L230
[5] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.VTKRecorder.recorders
[6] https://gitlab.com/yade-dev/trunk/-/blob/master/pkg/dem/VTKRecorder.cpp#L333
[7] https://gitlab.com/yade-dev/trunk/-/blob/master/pkg/dem/VTKRecorder.cpp#L788
[8] https://gitlab.com/yade-dev/trunk/-/blob/master/pkg/dem/VTKRecorder.cpp#L782

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