[deprecated list] Monitoring of tangential stress ?

[Jerome Duriez]

Hello everybody.
Short question : Considering a box containing my numerical sample I'ld
want to monitor the tangential stress acting on one plate of the box and
I wonder if someone has already made it ?

Less short question : In fact I want even monitor this tangential stress
("tau") depending on the normal one ("sigma") : so that the ratio
dtau/dsigma remains constant (to a given value) during the simulation,
whereas an other control parameter would be, for example, something like
a strain rate. Would you have something to say about it ??
Thanks

Jerome

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[Václav S(milauer]

Post by Jerome Duriez
Hello everybody.
Short question : Considering a box containing my numerical sample I'ld
want to monitor the tangential stress acting on one plate of the box
and I wonder if someone has already made it ?

Hi, there is utils.sumBexForces for mutliple bodies to get sum of forces
on those.

If it is just one body that is of interest for you, you use engine like

StandAloneEngine('PeriodicPythonRunner',{'iterPeriod':1000,'command':'print
O.actions.f(plateId)'})

in your simulation (O.actions.f(id) means force from physicalActions on
body #id).

Vaclav

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[Jerome Duriez]

Thanks for your answers.
- Vaclav : if I understand well the command you indicate allow me only
to follow the evolution of the tangential stress, not to act on it ?
(and I want to act on it, but maybe my english wasn't clear enough...)

- Luc : I saw it in your thesis, yes. That seems to be of high interest
for me, with the difference that you were acting on normal components
whereas I will also focus on tangential one...

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[Luc Sibille]

Post by Jerome Duriez
Hello everybody.
Short question : Considering a box containing my numerical sample I'ld
want to monitor the tangential stress acting on one plate of the box and
I wonder if someone has already made it ?
Less short question : In fact I want even monitor this tangential stress
("tau") depending on the normal one ("sigma") : so that the ratio
dtau/dsigma remains constant (to a given value) during the simulation,
whereas an other control parameter would be, for example, something like
a strain rate. Would you have something to say about it ??
Thanks

Hi Jerome,

I did something like that but I am not sure to be able to help you.

It was with SDEC, I was able for instance to control the ratio between
the stress deviator q=sigma_1 - sigma_3 and the volumetric strain
epsilon_v. You can find the details in my thesis.

I think that all the elements are already, more or less, written in Yade
to be able to do such a control. Indeed, with the
"TriaxialStressController" engine you can impose a given normal stress
component to be equal to a given value. In your case, this value is not
a constant but is proportionnal to a tangential stress for instance (or
reciproquely).

The tricky point when you define such simulation is the following:
depending on the mechanical response of the granular assembly and
depending on the value of the ratio of the two stress or strain
components you want to monitor, the numerical loop used to control the
stress on a wall can become instable. To limit this effect I introduced
a kind of damping parameter (such as the damping wall parameter defined
in the triaxialcompressionengine), but I don't think it is a clean
solution in this case because you don't really know what is the
influence of a such damping parameter on the simulated response...

Good luck

Luc

Post by Jerome Duriez
Jerome
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--
Luc Sibille

Université de Nantes - Laboratoire GeM UMR CNRS

IUT de Saint Nazaire
58, rue Michel-Ange - BP 420
44606 Saint-Nazaire Cedex, France

Tel: [phone]

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