Yade

bodyStressTensors() - getStress() comparison

Asked by Jérôme Duriez

Hi everyone,

  Does someone ever use the functions - from utils module - bodyStressTensors() and getStress() to compare quantitatively such different stress measurements (at different scales) ? Comparing also with any other measurement ? (like force measurements on a rigid boundary, ...) ? In periodic and non-periodic cases ?
    Me yes, and my results differ between these two cases (periodic or not)...

Thanks,

Jérôme

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Jan Stránský
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Jan Stránský (honzik) said : 		#1

Hi Jerome,
personally I have never used these functions for non-periodic cases, but I
would expect differences. Of what order is the difference? 1%, 100%...?
cheers
Jan

2014-06-17 11:02 GMT+02:00 Jérôme Duriez <
<email address hidden>>:

> New question #250355 on Yade:
> https://answers.launchpad.net/yade/+question/250355
>
> Hi everyone,
>
> Does someone ever use the functions - from utils module -
> bodyStressTensors() and getStress() to compare quantitatively such
> different stress measurements (at different scales) ? Comparing also with
> any other measurement ? (like force measurements on a rigid boundary, ...)
> ? In periodic and non-periodic cases ?
> Me yes, and my results differ between these two cases (periodic or
> not)...
>
> Thanks,
>
> Jérôme
>
> --
> You received this question notification because you are a member of
> yade-users, which is an answer contact for Yade.
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Revision history for this message
Jérôme Duriez (jduriez) said : 		#2

In fact, the periodic case is the problematic one for me..

In non-periodic cases (using rigid boundaries) bodyStressTensors data match rather satisfactorily other stress measurements, obtained with getStress(volume) or box-force measurements (these last measurements are reasonnably equal).

Whereas, in periodic cases, bodyStressTensors data overestimate by around 50% getStress() data... This overestimation can apparently not be explained by the discrepancy existing in bodyStressTensors data (among the different particles). Could you obtain consistent data with getStress() and bodyStressTensors() in periodic cases ?

Thanks !

Revision history for this message
Best Jan Stránský (honzik) said : 		#3

Hi Jerome,

how do you compare the results? average of bodyStressTensors, taking into
account porosity (see [1])..?

the formuals for computation are derived from the assumption of static
equilibrium, so this might be other reason..

cheers
Jan

[1] https://yade-dem.org/doc/yade.utils.html#yade._utils.bodyStressTensors

2014-06-17 12:21 GMT+02:00 Jérôme Duriez <
<email address hidden>>:

> Question #250355 on Yade changed:
> https://answers.launchpad.net/yade/+question/250355
>
> Status: Answered => Open
>
> Jérôme Duriez is still having a problem:
> In fact, the periodic case is the problematic one for me..
>
> In non-periodic cases (using rigid boundaries) bodyStressTensors data
> match rather satisfactorily other stress measurements, obtained with
> getStress(volume) or box-force measurements (these last measurements are
> reasonnably equal).
>
> Whereas, in periodic cases, bodyStressTensors data overestimate by
> around 50% getStress() data... This overestimation can apparently not be
> explained by the discrepancy existing in bodyStressTensors data (among
> the different particles). Could you obtain consistent data with
> getStress() and bodyStressTensors() in periodic cases ?
>
> Thanks !
>
> --
> You received this question notification because you are a member of
> yade-users, which is an answer contact for Yade.
>
> _______________________________________________
> Mailing list: https://launchpad.net/~yade-users
> Post to : <email address hidden>
> Unsubscribe : https://launchpad.net/~yade-users
> More help : https://help.launchpad.net/ListHelp
>

Revision history for this message
Jérôme Duriez (jduriez) said : 		#4

OK, your remark let me recall that there is some sound theory behind all these binary numbers..

I was messed up by the fact that a first crude interpretation gave quite consistent results (between different stress measurements) for the non-periodic case, and not for the periodic case... Computing things more precisely corrects the periodic case (after significant changes) and improves only as much as necessary the non-periodic one.

So, it's OK now in all cases !

Revision history for this message
Jérôme Duriez (jduriez) said : 		#5

Thanks Jan Stránský, that solved my question.