yade-dev team mailing list archive

[Jerome Duriez <duriez@xxxxxxxxxxxxxxx>]

I think I do not have my mind in the viscous framework.

But, in a general case, some of your phrases do not correspond to my 
current point of view:

> If more stiffness then more force for given overlap.
In my former simulations, I used this "NormalInelasticityLaw" which 
describes (Normal Force; overlap) states such as illustrated by attached 
figure. So, in this case, you can observe that the highest (tangent) 
stifness corresponds to lowest values of force : in unloading the 
stifness I used is higher than the one of loading; but unloading values 
of force are nevertheless lower than loading (initial loading) values of 
force, for given overlap.

Then, when you say:
> I consider only a loading because a unloading is less the loading, so 
> if loading is stable (not overestimate) then unloading is stable also.
Using this contact law I speak about, I had to decrease the time step. 
Let "K" be the ratio "unloading stifness" / "loading stifness" (= the 
ratio of the two slopes of the two type of lines you can see on the 
figure). The time step I could use with K=1 (loading = unloading), could 
not be used anymore if K>1 (the case of the figure).

I hope I could explain what I think ?
    It's completely ok for me when you say "So, for stability you need 
smaller time step for more stiffness". But I tend currently to disagree 
if you speak only of forces.

Jerome

Attachment: FnCL1.eps
Description: image/eps