Hi Bruno and Vincent,
thanks for your answers.
I have PFC manual on my desk (though I never directly used that code)
and they do define also contact viscous damping. In order to modify
the time step to account for damping effects, they re-define the
tangential and normal stiffness such that their values are increased
by some factors. Hence, the critical time step for viscous contacts
should result be smaller than the one for non-viscous contacts (do you
agree?). I could not find out where the PFC formulas come from, that
is why I asked to you about that so to have an alternative.
I appreciate your help (Sergei, perhaps you have also been using
viscous contacts, any ideas about the critical time step?).
Chiara
