yade-users team mailing list archive

[chiara modenese <c.modenese@xxxxxxxxx>]

2010/3/19 Václav Šmilauer <eudoxos@xxxxxxxx>

>
> > Bruno, I still have some doubts ;( I will try to explain myself. What
> > I see regarding the shear force is simply the need of a tangent unit
> > vector exactly for the same reason we define a normal one. The
> > direction of the normal force is not dependent upon which id is which
> > because we define the normal vector, but in the shear direction we are
> > not defining any vector of reference... I can see what you mean in the
> > normal direction but not in the shear one. Can you see my point? Am I
> > completely wrong?
>
> (Unless I get you wrong) There is no local coordinate system for
> interaction ("reference vector in the shear plane"), therefore
> shearForce has to be written in global space, but at the same time
> always perpendicular to normal, as it moves during simulation.
>
> (The normal vector doesn't define local coords, just one direction.)
>
> Cheers, vaclav
>
>
> Yes Vaclav, I was wrong and probably pretty confused by the existance of a
local coordinate system that actually does not appear anywhere. Athough
maybe is possible to define it, in this case is not worthing. Last question
on this side. Sergei said that we should take rel_vel = vel_body1 -
vel_body2. Now IICR in many contact laws (say the elastic one) is the
contrary. Should we change it or it is fine anyway?

Thanks for all your explanations!
Chiara

>
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