yade-dev team mailing list archive

[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

I just tried your script with r2260 and CohFric law (with moment law). I 
don't see any problem, except that the automatic timestep is too high. 
After reducing it, I see no problem.

B.

luc scholtes a écrit :
> Hi guys,
>
> After few investigations about CohesiveFrictionalPM in latest version, 
> I must admit that I still do not have any idea where to look for, so 
> if one of you could have any suggestion, it would be very kind.
>
> 1- CohesiveFrictionalPM seems to work well when it is used in basic 
> simulations (say two elements, sphere/sphere or sphere/box) and 
> without the moment law (the moment law produces the same "explosive 
> behaviour" when used with CohesiveFrictionalContactLaw, so it is 
> probably due to some problems with quaternion computation in Eigen as 
> it worked well with wm3... Unless there was something wrong with wm3...)
>
> 2- I don't understand why, but when CohesiveFrictionalPM is used in a 
> TriaxialTest or a uniaxial test (without the moment law, though), 
> everything explodes. Since there have been a lot of changes during the 
> last weeks (I use rev2185 without any problem), I don't really know 
> where to check first... I have attached a script that I use for 
> Triaxial Testing. I tested it with CohesiveFrictionalPM as well as 
> with CohesiveFrictionalContactLaw. RESULTS -> if the moment law is 
> desactivated, it works for CohesiveFrictionalContactLaw but not for 
> CohesiveFrictionalPM.
>
> The first thing I have noticed is that, if the timestep is fixed with 
> O.dt=-0.2*utils.PWaveTimeStep() (see the - before 
> 0.2*utils.PWaveTimeStep()), GlobalStiffnessTimeStepper() does not 
> update the timestep for CohesiveFrictionalPM (it does for 
> CohesiveFrictionalContactLaw), and, the walls just go through the 
> assembly.
>
> Then, fixing the timestep with O.dt=0.2*utils.PWaveTimeStep() (without 
> the -), I could see that after few iterations, everything explodes 
> again. Having a look into the TriaxialRecorder file, I could see that 
> the kinematic energy, as well as the unbalanced force increase 
> dramatically.
>
> The only (!!!!) difference between the two laws is that, one uses the 
> penetration depth as the interacting distance, whereas the other 
> initializes the interacting distance to the penetration depth when an 
> interaction is detected, and I saw this: 
> https://bugs.launchpad.net/yade/+bug/399963. Do you think it could be 
> related?
>
> Please... help
>
>   Luc
>
>
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--
_______________
Bruno Chareyre
Associate Professor
Grenoble INP
Lab. 3SR
BP 53 - 38041, Grenoble cedex 9 - France
Tél : 33 4 56 52 86 21
Fax : 33 4 76 82 70 43
________________