Yade

variable properties

Asked by nicole khoueiry

Hi guys,
I have a question regarding the variation of the materials properties during the run,
In fact, I cannot change it by changing the material properties; it will be changed only for new interactions,
So I have to change the inteactions physics properties.
The problem is that I want to change the young modulus, and I am using a CohFrictMat, the stiffness interaction properties in this law are: Kn, Kr, Ks and Ktw,
How can I relate those variables to the young modulus that I introduce at the beginning in the materials properties?
Thanks

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Jérôme Duriez (jduriez) said : 		#1

Hello,

You understood correctly the problem, the solution is classical (even though I understand you ask the question !):

 you have to perform yourself, from the Python interface, the loop over interactions to update interaction properties.

Updating obviously according to the corresponding equations that apply to new interactions, which you can always find in the code source [1] in case they are not included in the doc. See in particular this line [2] for the normal stiffness from "young" material parameter.

Let us know if you need further help,

Jerome

[1] https://github.com/yade/trunk/blob/e4e757f2e98a620e3177b7a36a1d10f69f6a6a28/pkg/dem/CohesiveFrictionalContactLaw.cpp#L254 and below
[2] https://github.com/yade/trunk/blob/e4e757f2e98a620e3177b7a36a1d10f69f6a6a28/pkg/dem/CohesiveFrictionalContactLaw.cpp#L265

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Bruno Chareyre (bruno-chareyre) said : 		#2

Hi,
Contact stiffness must be scaled proportionally to material stiffness.
I would add that the python loop on interactions may take too much time if it is applied very frequently. In this case it is not very difficult to turn it into a c++ loop. It is done for instance in setContactFriction() [1].
You can check the source code.
Bruno

[1] https://yade-dem.org/doc/yade.utils.html?highlight=setcontact#yade._utils.setContactFriction

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