Model a triaxial tests

Isabel Casasbuenas_21461

Hi everyone,

I am currently working on creating a triaxial compression test simulation in EDEM, since I want to use this model into the calibration toolkit and compare my results with some experimental data I have. I know triaxial test is not directly available in the calibration kit options, but I have been doing this by modifying the uniaxial compression model. I just need to applied a radially constant confining pressure (or at least that's my thoughts). What I have done is started with the uniaxial compression test template, use the sleeve geometry but disable the sleeve motion, so it remains in place during the test and add a force controller applying a force that represents he 30 kPa in X and Y directions and left z=0, and I also include a damping coefficient of 15 hz.

However, when I do that the sleeve kind of disappear in the middle of the simulation, and I don't honestly see the particles have a confinement effect. have anyone done this before?

is this the right approach to do it? or is there a better method to apply the constant radial confining pressure?

I appreciate any advice, suggestion or shared experiences. Thank you

Isabel

Stephen Cole

Hi,

EDEM doesn't have a specific module for Triaxial forces, there is some discussion here:

https://community.altair.com/discussion/25323/does-anyone-have-an-api-for-triaxial-test-dem-simulations

You could consider using the Fibers bonding model to create a skin of bonded particles around the sample:

https://help.altair.com/edem/topics/creator_tree_physics/fibers_bonding_model_c.htm

Then use the API to apply a inward force on the skin of particles to apply the pressure.

Regards

Stephen

Isabel Casasbuenas_21461

Hi Stephen,

Thank you for your reply. I definitely have seen the discussion and also the webinar, https://community.altair.com/discussion/40296/webinar-experimentally-validated-dem-model-of-a-triaxial-test-on-railway-ballast-utilizing-the-multi-sphere-approach?utm_source=community-search&utm_medium=organic-search&utm_term=Triaxial+Test

However, I still do not get how I can use the API. I have tried to following the tutorial of the intro, but I still do not get how to used and link i with EDEM, is this another app or software I should acquire?

https://www.youtube.com/watch?v=TAbvgzrGP8Y&list=PLGNemB0NFb0CieSxPqWNBFpim7EfHkXKT

Here’s the approach I’ve followed:

• I started from the Uniaxial Compression Test template in the Calibration Toolkit.
• I kept the sleeve geometry but disabled its motion so it stays fixed during the test.
• I then used a Force Controller to apply a lateral pressure equivalent to 30 kPa in both X and Y directions, and set the Z direction to 0.
• I included a damping coefficient of 15 Hz.

The issue I’ve encountered is that during the simulation, the sleeve seems to disappear partway through, and the particles don’t appear to experience any confinement. I’m not seeing the effect I would expect from a true triaxial setup.

I appreciate if you could give me a guidance.

Stephen Cole

Hi,

The API allows us to apply forces to particles, so you would have to create a skin of particles with the bonded particle model (tutorial via link below) around the sample and then apply a force based on this.

Depending on the shape I'm not sure it will be possible to do with a geometry sleeve as we can't deform the geometry, it will always be rigid and apply the force in the X and Y axis but my understanding is you would want the force to apply a radial force rather than along a specific axis, which could only be done via the API approach, however if you want to use the geometry you may need to make sure you are constraining to 2D (x and y), also that the geometry is Physical not Virtual

We have more tutorials on the API which you can see about half way down this link:

https://community.altair.com/discussion/33339/edem-tutorials

Regards

Stephen