yade-dev team mailing list archive

[Vincent Richefeu <richefeu@xxxxxxxxx>]

Le 7 févr. 2011 à 18:03, Bruno Chareyre a écrit :

> ,
>> Say that you have cohesion between particles, then if you project the
>> normal contact force along the normal to the plane you can see that
>> the sign of the force could be either negative or positive (depending
>> also on the convention). Bruno, what is your opinion?
> 
> I didn't want to reply because I don't really understand what the
> "strongness" of a contact is. You could look into papers of researchers
> promoting this concept and use the same definition as them. Strongness
> of forces has been defined for cohesionless packings initialy IIRC, but
> it has probably been extended to cohesive particles since then. You
> could find examples in the litterature and see if they use norms of
> forces or algebraïc values.
> In the later case, I guess they would ignore the shear part. Radjaï
> published a lot on this subject I think.
> 
> Bruno

Right.
It is common to split the forces with a threshold value. This threshold value is often the mean normal force. 
I think that the reason is that Radjai found that the pdf of normal forces changes around this value.

Concerning the split of the fabric, it can be interesting to distinguish negative from positive forces rather that "strong" and "weak" forces. 
One can image other splitting for any reason. I hope Vaclav's function can take a threshold argument to split the fabric so that the user is free to use the mean force or something else...

Vincent