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[Jérôme Duriez <question404524@xxxxxxxxxxxxxxxxxxxxx>]

Question #404524 on Yade changed:
https://answers.launchpad.net/yade/+question/404524

Jérôme Duriez proposed the following answer:
Ok, I think then you'll indeed have to write your own Python functions.

For the stresses, I would advice you loop over the "isOnJoint" interactions
*****************
for cont in O.interactions:
     if cont.phys.isOnJoint:
*****************
and average the cont.phys.normalForce and cont.phys.shearForce (see JFCMpmPhys doc [1]). The tricky part may be to define a consistent surface average: you may use cont.phys.crossSection but most probably the sum of all cont.phys.crossSection for all interactions along a given joint would differ from the apparent joint surface.

I have no exact idea how to solve this at the moment, but you may train
using the "testingJoint.py" example [2] that defines an easy to
interpret configuration: the expected stress values are easy to figure
out on this example, enabling a comparison with the Python functions you
would wrote.


For the relative displacements, another problem is that cont.geom is of ScGeom [3] type and does not account for the joint nature of the interaction. But you may still compute yourself normal and relative displacements with some inspiration from JCFpm source code: see [4] for the normal relative displacement and [5] for the shear component. 

Again, you may validate your measurements from the testingJoint.py
example. First lines of section 3 of reference Duriez et al.,
Engineering Fracture Mechanics, 2016 (Duriez2016 in https://www.yade-
dem.org/doc/publications.html which seems to be down at the moment ?)
may also help.


As for the strains, I still have no idea what an interface strain could be ;-)


[1] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.JCFpmPhys
[2] https://github.com/yade/trunk/blob/master/examples/jointedCohesiveFrictionalPM/testingJoint.py
[3] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.ScGeom
[4] https://github.com/yade/trunk/blob/master/pkg/dem/JointedCohesiveFrictionalPM.cpp#L55
[5] https://github.com/yade/trunk/blob/master/pkg/dem/JointedCohesiveFrictionalPM.cpp#L119 to L 130

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