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Message #02402
Re: DEM equations, written down.
> >
> > (16) is supposed to update shear force F_s (vector):
> >
> > F_s=F_s+K_s*ΔX_s
> >
> > but this is not correct, since you add ΔX_s (which is in the _current_
> > contact plane) to F_s (which is shear force from the previous step, i.e.
> > in the _previous_ contact plane)!!
> I don't understand the problem. F_s and ΔX_s are in the global
> coordinate system, not in any contact plane.
Yes, they are in global coordinates, but, at the same time, current F_s
must be always perpendicular to current n (in global coords); otherwise,
we wouldn't call is F_s, right?
Now, F_s from previous step is perpendicular to _previous_ n, while ΔX_s
is perpendicular to _current_ n. Summing these 2 together doesn't make
sense, since the sum not perpendicular to anything (neither current, nor
previous n).
v
Follow ups
References

DEM equations, written down.
From: Janek Kozicki, 20090930

Re: DEM equations, written down.
From: Janek Kozicki, 20090930

Re: DEM equations, written down.
From: Janek Kozicki, 20091008

Re: DEM equations, written down.
From: Janek Kozicki, 20091008

Re: DEM equations, written down.
From: Václav Šmilauer, 20100221

Re: DEM equations, written down.
From: Bruno Chareyre, 20100222