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[Rohit John <question694531@xxxxxxxxxxxxxxxxxxxxx>]

Question #694531 on Yade changed:
https://answers.launchpad.net/yade/+question/694531

    Status: Needs information => Open

Rohit John gave more information on the question:
Hello,

> why?
> why the other "can be handled"?

Shear force uses an incremental formulation whereas normal force and
moment uses an absolute formulation.  (At least in the code for
Law2_ScGeom6D_CohFrictPhys_CohesionMoment)

Fn = phys->kn * (un - phys->unp)
phys->moment_bending = geom->getBending() * phys->kr
Here un is the absolute normal displacement and getBending() give the absolute bending (I think). So they can be handled as follows

Fn = (phys->kn * (un - phys->unp))^3
phys->moment_bending = (geom->getBending() * phys->kr)^3

Here I have used a cubic function as an example for a non linear function. However, the shear force is calculated as follows
Vector3r& dus        = geom->shearIncrement();
shearForce -= phys->ks * dus;

Here instead of an absolute value for shear, the code uses the
shearIncrement, dus, to increase (decrease in this case) value of shear
calculated in the previous step.

in essence
dFs = constant*dus => dFs/dus = constant => linear function.

If I have to implement a non linear function, I need the absolute value
of shear

> What actually do you ask?
I am looking for a Law2 which uses non linear shear. How do I access the value of shearDisaplacement, how do I find it?

Kind regards,
RKJ

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