what is the plastic part of normal displacement in law2-cohesionMoment

Asked by Leonard on 2019-10-09

Hi,
I am confused about the concept of the plastic part of normal displacement (un^p) in Law2_ScGeom6D_CohFrictPhys_CohesionMoment [1].
I reviewed some papers such as "Discrete modeling of granular soils reinforcement by plant roots[2]" and "Calibration of DEM material parameters to simulate stress-strain behaviour of unsaturated soils during uniaxial compression[3]".
In these two papers, they use Law2_ScGeom6D_CohFrictPhys_CohesionMoment as the contact law, but there is no un^p in their model.
Why there is a difference between Yade document and these papers?

Thanks
Leonard

[1]https://yade-dev.gitlab.io/trunk/yade.wrapper.html?highlight=cohfrict#yade.wrapper.Law2_ScGeom6D_CohFrictPhys_CohesionMoment
[2]https://www.sciencedirect.com/science/article/pii/S0925857413001936?via%3Dihub
[3]https://www.sciencedirect.com/science/article/pii/S0167198718314909

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Solved by:
Robert Caulk
Solved:
2019-10-09
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2019-10-09
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2019-10-09
Best Robert Caulk (rcaulk) said : #1

Hello Leonard,

> I am confused about the concept of the plastic part of normal displacement (un^p) in

It is the unrecoverable deformation associated with the contact. The plastic deformation occurs when adhesion is exceeded and the maximum plasticity is not exceeded [1]. This model is not active by default, it is only actived if the material is set with fragile=true [2].

>Why there is a difference between Yade document and these papers?

Either a) the papers didn't use plasticity, (i.e. fragile=false) or b) the plasticity feature was added after the papers were published.

Cheers,

Robert

[1]https://gitlab.com/yade-dev/trunk/blob/master/pkg/dem/CohesiveFrictionalContactLaw.cpp#L124
[2]https://yade-dev.gitlab.io/trunk/yade.wrapper.html?highlight=cohfrict#yade.wrapper.CohFrictPhys.fragile

Leonard (z2521899293) said : #2

Thanks Robert Caulk, that solved my question.