yade-dev team mailing list archive

[Václav Šmilauer <eudoxos@xxxxxxxx>]

What do you mean, cohesive shear force? You just change definition of
plasticity surface to get shear resistanace when the contact is in
tension. This is what you have currently:

Real maxFsSq=phys->normalForce.SquaredLength()*phys->tanFrictionAngle*phys->tanFrictionAngle;

so you change that accordingly. In attachment, there are some plasticity
surfaces used in the concrete model. Those for ω=1 (damaged) carry no
cohesion (that is what you have now), undamaged (ω=0) ones do have
cohesion, which is what you need. (Horizontal axis is normal stress,
vertical is |shear stress|). (Disregard those log surfaces, they are not
relevant here)

So if you go with this kind of linear plasticity surface, you need one
additional parameter (e.g. cohesion=max normal stress=x-coordinate of
the cone top):

Real maxFs=max((Real)0.,cohesion-sigmaN*tanFrictionAngle);
if(sigmaT.SquaredLength()>maxFs*maxFs){
	// plastic slip
}

See e.g. http://en.wikipedia.org/wiki/Yield_%28engineering%29, but they
have plasticity surfaces defined in terms of 3 principal stresses,
whereas we have to use formulation with σn vs. |σt| with DEM (at least
for 3 degrees of freedom of the contact), which corresponds to taking
σ₁=σn and σ₂=σ₃=|σt| (I think; never thought about that properly).

Cheers, Vaclav




> Hi,
> 
> I am trying to add "shear cohesive force" into the RockPM, as for now
> there are only normal cohesive forces. Has anybody an advice where to
> get such algorithm to escape write it from scratch?
> 
> Thanks for all suggestions.
> ______________________________
> 
> Anton Gladkyy
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