Re: [Yade-users] [Question #402828]: Control the normal stress fluctuation in the direct shear box modeling

2016-10-07 Thread Jérôme Duriez
Question #402828 on Yade changed:
https://answers.launchpad.net/yade/+question/402828

Jérôme Duriez posted a new comment:
As a side note, KinemCNLEngine [1] is a dedicated engine for such task
for simple shear (as opposed to direct shear) boxes. The corresponding
code source [2] may also give some hints (corresponding to Bruno's
suggestions)

[1] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.KinemCNLEngine
[2] 
https://github.com/yade/trunk/blob/e4e757f2e98a620e3177b7a36a1d10f69f6a6a28/pkg/dem/KinemC__Engine.cpp

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Re: [Yade-users] [Question #402828]: Control the normal stress fluctuation in the direct shear box modeling

2016-10-07 Thread Bruno Chareyre
Question #402828 on Yade changed:
https://answers.launchpad.net/yade/+question/402828

Status: Open => Answered

Bruno Chareyre proposed the following answer:
One possible strategy is to simply impose a force on the top plate and let it 
equilibrate (it needs to have a mass).
Is is simple but it does  not offer the best control usually, due to the 
inertia of the plate.

Another strategy is to impose de velocity (or displacement): v = f(sm-st), with 
"sm" the measured force and "st" the target force.
The remaining question is how to define f. One way is to calculate the 
cumulated stiffness K of all plate-particle interactions, and to use it in:

v=(sm-st)/(K*O.dt)

which will produce a nearly constant force.

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[Yade-users] [Question #402828]: Control the normal stress fluctuation in the direct shear box modeling

2016-10-06 Thread Weimin Song
New question #402828 on Yade:
https://answers.launchpad.net/yade/+question/402828

Dear all,

I'm modeling the direct shear box right now.

I made vertical compression of the assembly with a moving wall until the 
pre-defined compressing force is reached. And then I made the shear.  However, 
during the shear, the normal force deviated from the pre-defined value. 

After I checked the references, I know during the shear process, the desired 
compressing normal force can be  regulated to stay the same by moving the upper 
plate up or down, depending on the actual compressing force value. However, how 
to adjust? Anyone can give me some hints?

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