CohesionMoment

Asked by Leonard on 2019-11-13

Hi,
I'd like to involve cohesion and moment for contacts, and Law2_ScGeom6D_CohFrictPhys_CohesionMoment [1] seems to be a proper one. However, I got few questions according to the introduction documents.
1. In [1], click on link ''Law2_ScGeom6D_CohFrictPhys_CohesionMoment::momentRotationLaw '', it doesn't point to any specific position. Or maybe this is not a problem:)
2. Refer to ''CohFrictMat.momentRotationLaw'' [2], since I want to involve moment, I need to define the material something like:

O.materials.append(CohFrictMat(isCohesive=True,normalCohesion=1e6,shearCohesion=1e6,momentRotationLaw=True,etaRoll=0.1)).

In [2], it asks to go to ''CohFrictPhys.cohesionDisablesFriction'' [3], it says "is shear strength the sum of friction and adhesion or only adhesion? '' and the default value of [3] is false, does it mean that when set it as false, the shear strength is the sum of friction and adhesion?

3. Refer to ''CohFrictPhys.momentRotationLaw'' [4], [4] asks to go to ''Law2_ScGeom6D_CohFrictPhys_CohesionMoment::always_use_moment_law'' [5],
I choose false (defalt value) for the purpose of computing moments only for cohesive contacts. However, in ''Law2_ScGeom6D_CohFrictPhys_CohesionMoment'' [1], it says that ''Cohesive -type moment may also be included in the future'', it gives the feeling that Cohesive -type moment can not be achieved in this model currently, which makes me confused.

By the way, I also reviewed some papers which worked based on Law2_ScGeom6D_CohFrictPhys_CohesionMoment. In general, they didn't consider cohesion and moment at the same time. This has deepened my doubt about if cohesion and moment can be taken into at the same time in terms of Law2_ScGeom6D_CohFrictPhys_CohesionMoment.

Could you please give some suggestions?
Many thanks.

Leonard

[1]https://yade-dev.gitlab.io/trunk/yade.wrapper.html?highlight=law2_scgeom6d_cohfrict#yade.wrapper.Law2_ScGeom6D_CohFrictPhys_CohesionMoment

[2]https://yade-dev.gitlab.io/trunk/yade.wrapper.html#yade.wrapper.CohFrictMat.momentRotationLaw

[3]https://yade-dev.gitlab.io/trunk/yade.wrapper.html#yade.wrapper.CohFrictPhys.cohesionDisablesFriction
[4]https://yade-dev.gitlab.io/trunk/yade.wrapper.html#yade.wrapper.CohFrictPhys.momentRotationLaw
[5]https://yade-dev.gitlab.io/trunk/yade.wrapper.html#yade.wrapper.Law2_ScGeom6D_CohFrictPhys_CohesionMoment.always_use_moment_law

Question information

Language:
English Edit question
Status:
Solved
For:
Yade Edit question
Assignee:
No assignee Edit question
Solved by:
drasszkusz
Solved:
2019-11-15
Last query:
2019-11-15
Last reply:
2019-11-13
Best drasszkusz (drasszkusz) said : #1

Hello,

> In [2], it asks to go to ''CohFrictPhys.cohesionDisablesFriction'' [3], it says "is shear strength the sum of friction and adhesion or only adhesion? '' and the default value of [3] is false, does it mean that when set it as false, the shear strength is the sum of friction and adhesion?

Yes, if false, the shear strength is the sum of friction and adhesion.

> 3. Refer to ''CohFrictPhys.momentRotationLaw'' [4], [4] asks to go to ''Law2_ScGeom6D_CohFrictPhys_CohesionMoment::always_use_moment_law'' [5],
I choose false (defalt value) for the purpose of computing moments only for cohesive contacts. However, in ''Law2_ScGeom6D_CohFrictPhys_CohesionMoment'' [1], it says that ''Cohesive -type moment may also be included in the future'', it gives the feeling that Cohesive -type moment can not be achieved in this model currently, which makes me confused.

If false, it computes the rolling and twisting moments (controlled by rolling and twisting resistance/friction coefficents aka etaRoll and etaTwist) in case of active cohesive bonds between particles. This way you can control the movement of the rolling and twisting of particles on/to each other. If it set to true, then it always calculates the moments also if there is no cohesive connection between particles. This way the particle shapes can be considered in numerical way, if the real particles are not perfectly spherical. [1]

>By the way, I also reviewed some papers which worked based on Law2_ScGeom6D_CohFrictPhys_CohesionMoment. In general, they didn't consider cohesion and moment at the same time. This has deepened my doubt about if cohesion and moment can be taken into at the same time in terms of Law2_ScGeom6D_CohFrictPhys_CohesionMoment.

There are some papers considering both at the same time [2] [3]. In the [3], you can find the mathematical background (equations) which are from the source code.

Daniel

[1] https://www.sciencedirect.com/science/article/pii/S0020768318302567
[2] https://www.sciencedirect.com/science/article/pii/S0168169918316429
[3] page 272-282 https://mercurylab.co.uk/dem8/wp-content/uploads/sites/4/2019/07/263.pdf

drasszkusz (drasszkusz) said : #2
Leonard (z2521899293) said : #3

Thanks drasszkusz, that solved my question.