Bond break for granular bonds

Submitted by SHUBHAM AGARWAL on Thu, 10/08/2020 - 21:36

Hi
I am trying to break granular tupe bonds, by using the command:
fix bondbr3 all bond/break 1 2 ${adh_crit_dist}
2- bondtype
${adh_crit_dist} - critical distang to break the bond

I have also tried fix bondbr3 all bond/break/gran 1 2 ${adh_crit_dist}
But I am getting the following error:
Invalid fix style: "bond/break"

Can we model bond breakage for granular bonds?

Thanks

Forums:

mschramm | Fri, 10/09/2020 - 17:02

Hello,
If you are using the granular bond, the last option set in the bond_coeff command is how you tell the bonds to break

bond_coeff 1 ${OR} ${IR} ${Y} ${G} ${BoT} ${BoV} ${BrT} ${BrV1} ${BrV2}

Here ${BrT} is the break type {0, 1, 2}
Where break type 0 is a SIMPLE BREAK in which you supply a critical distance and if the two bonded atoms exceed this distance, the bond breaks
break type 1 is a stress type break in which you supply a maximum normal stress and a maximum tangential stress. If the bond sees a higher value for either, the bond is broken.
break type 2 is a stress and heat type break (must include heat properties) in which you supply a maximum normal stress, a maximum tangential stress, and a max temperature.

Rachel | Fri, 10/14/2022 - 11:37

Hi Dr. Schramm,

I am using your newest package (updated to liggghts v3.8) and I am wondering:

1. What did you mean by saying, '${OR} ${IR} ${Y} ${G} ${BoT} ${BoV} ${BrT} ${BrV1} ${BrV2}'? Where can we find the explanations?

2. I cannot see any explanation or the applied formulas on different bond types and breakage types? Could you further explain anything on that or provide any references?

3. Whether the proposed method can be directly applied to coupled CFD-DEM analysis as you posted in Youtube? Where can I get any examples on the coupled analysis for a quick guidance?

Thanks so much!
Rachel

mschramm | Sun, 10/16/2022 - 23:57

You can look at my repo's wiki for some of the info:
https://github.com/schrummy14/LIGGGHTS_Flexible_Fibers/wiki/bond_gran

You can find an example of the cfd-dem coupling with bonds here:
https://github.com/schrummy14/CFDEMcoupling-PUBLIC/tree/master/tutorials...

The issue with coupling with cfd is not the bond forces themselves but the particle definition. This can be mitigated if:
1) Using IB and having your particle definitions have high overlap as the void ratio will be correct
2) Not using IB and you do not have any overlapping spheres as if you do, your spheres can be double counted at the overlap.

SHUBHAM AGARWAL | Fri, 10/09/2020 - 23:42

Thanks
I am using "fix_modify bondcr3 every 0" after first run to stop the further bond creation.
Will it also stop the bonk breakage?