yade-users team mailing list archive

[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

> I am still investigating the cohesionlessMomentRotation.
> It is written in the sources files that this code has been "verified 
> with the paper of Plassiard in GM".
>
> However, Plassiard considers in his paper "and in his thesis" only the 
> rolling part of the relative rotation of particles (and thus only 
> bending moment), whereas in the code rolling and twist part of the 
> relative rotation are considered (and thus bending and twist moment).
There would be no contradiction here, if only it was possible to set 
twist stiffness = 0 (so the law with bending and twist would "contain" 
the law with bending alone).
For now, Ktwist=Kbending=Kr, so it is indeed not possible...

> My question: is there a particular reason for that? What is the 
> motivation of the person who wrote this code? I don't say that is bad 
> or good, but I would like to have an idea about advantages and 
> disavantages, and physical meaning for considering a twist moment.
As soon as there is a finite area of contact between the solids (i.e. 
always), it makes sense to include twist resistance I think. The testing 
has been done by Boon IIRC.

By the way, I think rolling resistance, Ktwist!=Kbending, and other 
features would be ideally implemented in 
Law2_ScGeom_CohFrictPhys_CohesionMoment, which is now the cleanest, and 
shortest code for moments.
Funky factors η, α, β, would be contained in a collection of Ip 
functors, since they are not needed by the law itself, which just needs 
4 stiffnesses, and the definition of maximum values for each force/moment.

Any help on this task of unifying duplicates would be welcome.

Cheers.

Bruno