yade-users team mailing list archive

[chiara modenese <c.modenese@xxxxxxxxx>]

On 25 March 2010 19:04, Sergei D. <sj2001@xxxxxxxxx> wrote:

> 25.03.2010 18:57, chiara modenese:
> > I am testing my script with the class you committed but there is
> something
> > wrong. In the contact law I used to "play" with the damping in the shear
> > direction I coded something as in the attached file. Please look at that
> (I
> > changed the terminology but it is clear what it does) so you can check if
> > you are doing well.
> > I do not commit my law simply because it is quite a mess and I was
> playing
> > with it to clarify this issue around the damping. Please update your law
> > following the procedure as I suggested.
> >
> > Thanks, Chia
> >
>
>
> Sorry, but I'm confused... You are wrote in the ViscoGlobal.cpp:
>
> > ///////////////////////////////////////// MOHR-COULOMB LAW
> >       Real maxFs =
> phys->normalForce.SquaredLength()*std::pow(phys->tangensOfFrictionAngle,2);
> >       if (shearElastic_cum.SquaredLength() > maxFs)
> >       {
> >       Real ratio = Mathr::Sqrt(maxFs)/shearElastic_cum.Length();
> >       shearElastic_cum *= ratio;
> >       phys->shearForce = shearElastic_cum;
>

Above it is to say that if the total (and updated in terms of motion)
elastic force (variable shearElastic_cum) is higher than the maximum shear
force according to Mohr-Coulomb, then set the shearForce (that one we will
apply on the bodies) equal to this maximum value. Hence we consider only
friction damping if we slip.


> >       }
> >       else
> >       {phys->shearForce = shearElastic_cum + shearViscous;} // ad
>

Above it is to say that if we have passed the criterion we add the
shearViscous force. Hence we consider friction damping + viscous damping (if
no slip occurs).


>
> So, you have only elastic friction for dynamic, and (elastic+viscous)
> for static friction. Is'n it?
>
> Exactly, if with "static friction" you mean the situation where we do not
have slip (but we are still moving).
Let me know if it is clear.
Chia

>
> --
> Best regards,
> Sergei D.
>
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