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[Bettina Suhr <question275459@xxxxxxxxxxxxxxxxxxxxx>]

New question #275459 on Yade:
https://answers.launchpad.net/yade/+question/275459

Dear all,

I simulate direct shear tests using the Hertz-Mindling contact law with damping (given coefficient of restitution). By chance I saw that there exist contacts where F_t > mu F_n, which violates the Mohr-Coulomb criterion. 
When I looked at the source code (HertzMindlin.cpp lines 407-420) I found the reason: The tangential force is calculated according to Mindlin’s law. Then the Coulomb criterion is checked. If the contact is sliding, F_t=mu F_n is set. If the contact is not sliding, the damping term is added. So it can happen that a contact which was not sliding before damping force is added, violates F_t <= mu F_n after the damping part is added. 
Is this intention or is it a bug? From my understanding of the paper of (Tsuji et at., 1992), first the damping force should be added and then the check for Mohr-Coloumb criterion should be applied.

Thanks,
Bettina



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