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[Jerome Duriez <jerome.duriez@xxxxxxxxxxxxxxx>]

Hello Janek,

I asked me the same questions as you. Here is what I made, from far not 
claiming that this is the right way to do (I realized again by typing 
this that some modifications could be made)...

Le 07/07/2010 16:12, Janek Kozicki a écrit :
> Hello,
>
> I need to add two parameters:
>
> - Rolling stiffness coefficient β
> - Moment limit coefficient η
>
>
> Currently β has a fixed value of 2.0 in Ip2_2xCohFrictMat_CohFrictPhys.cpp line 52
>
> Where to add it? Should I add it to CohFrictMat.hpp or should I
> derive from this class and name it CohFricRollMat ?
>
> How to name it? rollingStiffnessCoefficient comes to mind. But could
> be also a rollingCoefficient, bendingCoefficient and so on.
>
>    
I use a parameter named very simply "betaR". It is in fact registered in 
Ip2_2xNormalInelasticMat_NormalInelasticityPhys, not in material 
parameters... Now I re think about it, I'd have difficulties to justify 
it... Maybe it appeared me more logical because the definition of the 
torque-stifness, equal to "betaR * R_mean ^2" could suggest that this 
"BetaR" is a parameter common to all the interactions, and not the 
bodies.... Not a real justification anyway...
If you set it in a new Material class, I could be interested. For now I 
use "NormalInelasticMat", which contains an other parameter I need for 
"my" contact law. Now I re-think to put this "betaR" in this class, 
maybe I could inherit from yours ? Or maybe not because "mine" inherits 
from FrictMat, not CohFrictMat.
> Currently η has a fixed value at ∞, or am I completely unaware that
> it has been implemented in the code, by someone. It limits the
> maximum value of rolling moment proportionally to Fn.
>
>    
You are (were, now) a bit unaware. NormalInelastictityLaw.cpp (which 
contains the class Law2.....) limits the rolling moment. By 
"forMaxMoment" * Fn; "forMaxMoment" being stored in 
NormalInelasticityPhys(maybe not consistent, again) and computed in 
pkg/dem/Engine/Functor/Ip2_2xNormalInelasticMat_NormalInelasticityPhys.cpp 
l.63, with an "1.0 corresponding to ethaR which I don't know exactly 
where to define as a parameter...", as I wrote in this place
> I remember you discussing that CohesiveFrictionalContactLaw should be
> dissected somehow, into a 2-argument functor, or something else. What
> was that?
>
>    
I guess it is about the fact that now contact law are no more supposed 
to be GlobalEngine, but LawFunctor. See § surrounding 
https://www.yade-dem.org/sphinx/user.html#law2-functor-s and class 
InteractionDispatchers
> Last question, why the name Ip2_2xCohFrictMat_CohFrictPhys instead of
> Ip2_CohFrictMat_CohFrictMat_CohFrictPhys. Of course the latter is
> longer. But is there a fixed convention about that? For instance the
> file Ip2_FrictMat_FrictMat_FrictPhys.hpp  definitely breaks this convention.
>
>    
I think I asked also this question. If I remember well, the convention 
is not so strict (good thing in this case I think), that's why me I 
chose to use "Ip2_2xNormalInelasticMat_NormalInelasticityPhys"

Jerome

--
Jérôme Duriez
ATER Iut 1 Grenoble, département GMP - Laboratoire 3S-R
04.56.52.86.49 (ne pas laisser de messages sur le répondeur)