# yade-users team mailing list archive

## Re: [Question #670047]: Determining macro parameters in uniaxial compression

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```Question #670047 on Yade changed:

Jan Stránský proposed the following answer:
Hello,

> I'm sorry to say there are many things in your reply I don't
understand.

sorry, it is difficult to give answer to a very general question like
you gave to somebody we know nothing about :-)

first (as mentioned above) please really answer at least to yourself "what and why you simulate and what results you want to extract".
Also what is your motivation to use Yade/DEM?
For how long do you want to use it (several years for PhD or do just this simulation for a short school project...)?
What is your background?
.....

So far, your questions are independent of Yade or DEM, the main ideas
would apply also to experiments, i.e. having results from uniaxial
experiment, how can I determine this and that macro value? If you are
clear on these topics theoretically, it is much easier to determine
corresponding values from simulation.

> if I modify the test to use just compression (the original first make
tension and then compression) I can still get Young from the initial
slope of the plot??

yes

> And likewise, maximum and minimum value would correspond to tensile
and compressive strength??

since for compression only you have no tension, you only get compressive
strength

> Please, could you explain me what oedometric module is??

oedometric modulus is an elastic modulus (multiplier of strain to get stress) for uniaxial strain (similary Young's modulus is elastic modulus for uniaxial stress)
[1,2]

> So, what should I modify in the code to convert it to "uniaxial strain
conditions (oedometric test)"

basically you need completely different simulation :-) see above..
The uniaxial constrain is model e.g. by walls or by periodic boundary conditions.

Building a new simulation, consider also (as mentioned before)  to use
triaxial compression to evaluate bulk modulus. Knowing also Young's
modulus, it is easy to extract Poisson's ratio [3].

> and how could I compute oedometric module???

as an initial slope of stress-strain curve (also valid for bulk modulus)

cheers
Jan

[1] https://www.finesoftware.eu/help/geo5/en/oedometric-modulus-01/
[2] http://web.mit.edu/16.20/homepage/3_Constitutive/Constitutive_files/module_3_with_solutions.pdf (section 3.8.2)
[3] https://en.wikipedia.org/wiki/Hooke%27s_law (section Linear elasticity theory for continuous media)

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