Simulating the time-dependent behavior of single grain

Hello,

> I'm a new user in Yade

welcome :-)

please read [1] and provide more information about your problem and simulation:
- what is "time-dependent behavior or creep analysis or aging"? "just" dynamics? Short-time viscosity? long-term aging of concrete? ... ?
- what is "single grain"? single physical real grain? single Yade particle?
- behavior between ... grains - single grains? grains? more information needed :-)

> Is there a contact model to know the time-dependent behavior

again, more information is needed.
Generally speaking, any Yade contact model describes time-dependent behavior.

Cheers
Jan

[1] https://www.yade-dem.org/wiki/Howtoask

Hi Jan Stránský,

thank you very much for your reply and suggestions! I would like to add more information.

The single sand grain will be simulated as an agglomerate ( a group of sub-particles bonded together ). This agglomerate will be loaded between two steel plates with a small constant load for days or months. Time-dependent fracturing/deformation/force at contacts can be simulated.

Is there the Parallel-Bonded Stress Corrosion (PSC) model or any other similar model in Yade?
PSC model was proposed by Potyondy (2007) as an extension of BPM to include the time-dependent behavior of rocks (the time-dependent development of microcracks) by adding a damage-rate law to the parallel-bond formulation. If a parallel bond is under tensile stress higher than the activation stress, the bonding material will be removed at a specified rate governed by a damage-rate.

I found a class yade.wrapper.CpmMat. It has "damLaw" for damage evolution in uniaxial tension. I do not know if it is can reach my object. Could you give me some advices? Thanks a lot again.

best,
Du Zhang

> for days or months

I am afraid that then DEM (Yade) is not the tool to use..
Yade is suitable for dynamic simulations, which are "short". It uses explicit time integration, which needs "very short" time step to make the simulation stable.

You could maybe use some implicit integration scheme, but I am not sure how it would work for "non-continuous" phenomenons

Or some event-driven approach, but then there might be a problem with non-linearity..

Or some combination of above? Some "long-time-step" approach for "calm" periods without breakage, skipping to explicit time integration when breaking occurs until it stabilizes, then again "long-time-step" approach...

Are new contacts important to your problem? If not, I would consider other methods then DEM.

All in all, sounds like challenging topic :-)

> I found a class yade.wrapper.CpmMat. It has "damLaw" for damage evolution in uniaxial tension. I do not know if it is can reach my object.

Cpm was developed to simulate short-term behavior of concrete. damLaw parameter just switches between exponential or linear softening branch, so it (neither damLaw neither Cpm) is not suitable for your problem.

But, as discussed above, I see the biggest problem in "time length" of your problem (w.r.t. DEM).

Cheers
Jan

Hi Jan Stránský,

Thank you for your reply and suggestions. Sorry for the late reply, I reconfirmed the task with the instructor.

>The single sand grain will be simulated as an agglomerate ( a group of sub-particles bonded together ). This agglomerate will be loaded between two steel plates with a small constant load for days or months.
Do we have a creep contact model for the single agglomerate under constant load in Yade? My instructor thinks the creep contact model is the most important.

> long-term aging of concrete? ... ?
The first time, you reply to me, give me an example. Is there a script for " long-term aging of concrete"? Or there is only the short-term of concrete to use Cpm.

>Yade is suitable for dynamic simulations, which are "short". It uses explicit time integration, which needs "very short" time step to make the simulation stable.
>You could maybe use some implicit integration scheme, but I am not sure how it would work for "non-continuous" phenomenons
Could you please explain one more time for me, and I understand it like this: in Yade default uses explicit time integration and I can also change it into implicit integration, but maybe not good for the non-linear situations. or only uses explicit time integration? Is it due to too much computer cost?

Thank you for your time. Yade is my first choice, if it is really not suitable, I may try other DEM software.

Thanks a lot again!

best,
Du Zhang

> Do we have a creep contact model for the single agglomerate under constant load in Yade? My instructor thinks the creep contact model is the most important.

There are some models including viscosity, have a look [1] (I myself do not use and know them almost at all).
Also there were some models developed, which were not put to the Yade source code [2], you can search question history.

Yes, the contact model is of course important. But the solution approach too.
E.g. if the simulation is not feasible to compute, then the best model is "useless".

> Is there a script for " long-term aging of concrete"? Or there is only the short-term of concrete to use Cpm.

No.
I doubt there is any example of "long-term" behavior, since (as discussed), Yade is used for "short-term" scenarios.

>> You could maybe use some implicit integration scheme, but I am not sure how it would work for "non-continuous" phenomenons
> Could you please explain one more time for me, and I understand it like this: in Yade default uses explicit time integration and I can also change it into implicit integration, but maybe not good for the non-linear situations. or only uses explicit time integration? Is it due to too much computer cost?

Yes, Yade default (I would say almost "built-in") time integration is NewtonIntegrator, using explicit time integration, requiring "very short" time step. Not usable for "long term" simulations.
But you can use other integration, e.g. there is RungeKuttaCashKarp54Integrator [3], or some substepping, or event-driven approach, or .... many of the ideas are out of scope of Yade..

> Yade is my first choice, if it is really not suitable, I may try other DEM software.

I am not sure if Yade and DEM is the way to go..
Yade is nice that it is open source and you can "add anything". Assuming non-negligible time costs and some programming. So it also depends on your time, background etc.

Now you know some basic ideas, maybe you can ask new specific questions [4] for the sub-topics (model, integration scheme, general discussion about feasibility, ...).

My conclusion: from Yade (and DEM in general), I see the biggest problem the "long term" behavior.

Cheers
Jan

[1] https://yade-dem.org/doc/yade.wrapper.html#constitutive-laws
[2] https://answers.launchpad.net/yade/+question/255780
[3] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.RungeKuttaCashKarp54Integrator
[4] https://www.yade-dem.org/wiki/Howtoask