yade-users team mailing list archive

[Jérôme Duriez <Jerome.Duriez@xxxxxxxxxx>]

Hello Benoît,

For your information, the habit is now rather to ask questions via 
Launchpad interface (https://answers.launchpad.net/yade/+addquestion, 
have also a look at https://answers.launchpad.net/yade)


My personnal feeling is that your problem is calibration of the 
parameters of your numerical discrete model towards the experiments you 
want to simulate.

I'd recommand you first to have in mind that what is called Young 
Modulus in Yade has NOTHING to do with a Young Modulus in continuum 
mechanics... I dared to upper case "NOTHING" since the equations, and 
the roles in these equations of these two "Young Modulus", have nothing 
in common, even if correlations can be deduced.. I wouldn't be able to 
answer you why it is called "Young modulus", then...

Maybe some " " around Young's modulus in 
https://www.yade-dem.org/doc/yade.wrapper.html#yade.wrapper.ElastMat.young 
would be helpful to not mislead anyone ?


An other thing is also that 200 particles were surely too few to have a 
behaviour that depends only on the mechanical parameters of your 
numerical model. 2000 is already better, but 10000 is maybe the most 
common, I would say.

Le 10/02/2012 11:36, CHARLAS Benoit 224833 a écrit :
> Hi everybody
>
> I have some problems on YADE at the moment. I’ll try to make it clear.
>
> I did an experimental oedometric test on a metal powder with a very 
> low punch stress (~5MPa). Metal powder for gears manufacturing are 
> usually pressed up to ~900MPa.
>
> So I expect there is no plastic deformation of the grains in my case.
>
> I wanted then to reproduce this with an elastic Contact Law on YADE 
> (with “Law2_ScGeom_FrictPhys_CundallStrack()”)
>
> The *numerical results* show a higher volumetric density than 
> experimental measurements (that was expected …) but also *forces 
> around 2000 times too important.*
>
> **
>
> I checked the following:
>
>   * *Units*of my parameters
>   * *Unbalanced force*(to remain quasi-static)
>   * *Number of particle*(from 200 to 2000 and soon to 10000)
>   * Change initial *volumetric density* with friction or clumps
>   * Reduce the *velocity* of the upper punch
>   * Reduce by 1000 to 3000 times the *Young Modulus*
>
> From all the things I checked, the sole way to obtain numerical forces 
> near the experimental ones was to reduce the Young Modulus by 2000 or 
> 3000 times.
>
> My current problem is that I can’t justify such a result.
>
> Do you have an *explanation *on how to justify this*or *some*tips* on 
> what could be checked?
>
> Thanks
>
> Benoit
>
>
>
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--
Jerome Duriez
Post-Doctorant LTDS (Ecole Centrale de Lyon)
04.72.18.62.17