Yade

how the local residual friction angle is determined

Asked by Yor1

Hi Yade users,

In the paper of Scholtès and Donzé (2013), it is shown that the shear rupture occurs when Fs > Fs,max.
The maximum shear force is calculated for a bonded interaction according to
F s,max= Fn tan(fi_b) + c Aint (1)
with Fs,max : the maximal shear force, Fn : Normal force, fi_b local friction angle, c internal cohesion and Aint the interacting surface between particles.
After the shear rupture, the interaction becoming then purely frictional between the initially bonded particles and
Fs,max= Fn tan(fi_c) (2)
with fi_c : local residual frictional angle.
When i consult the sources files (JointedCohesiveFrictionalPM.cpp/hpp), in find the the formulation of Fs,max (1) in the elastic interaction (before the shear rupture) but i don't find the formulation (2) of the Fs,max in the frictional interaction between particles (after shear rupture).
Also i don't find how the local residual friction angle is calculated.
The paper of Scholtès and Donzé : https://filex.univ-lorraine.fr/get?k=BkVd4nEPcmFqnP8eXp9
JointedCohesiveFrictionalPM.cpp : https://filex.univ-lorraine.fr/get?k=HaicRsz6ki2qTs6viev
JointedCohesiveFrictionalPM.hpp : https://filex.univ-lorraine.fr/get?k=E6gxYHx07RaoWylgXyX

Best regards.
Jabrane.

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Jérôme Duriez (jduriez) said : 		#1

Hello,

In YADE's implementation of this JCFpm model there is no such thing than a residual friction angle: "phi_b" = "phi_c".
You may also see that the above-mentionned paper lists only one "phi" value in the parameters Tables. ;-)

Jerome

PS : all YADE source code files are already on the internet at https://github.com/yade/trunk/, you maybe do not need to upload them on univ-lorraine.fr

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Yor1 (jabrane-hamdi) said : 		#2

Hello Jérôme,

Thank you for your answer.
In this case, i mean "phi_b" = "phi_c", we should have
Fs,max=Fn tan(fi_b) after the rupture and i don't find this formulation in the source file JointedCohesiveFrictionalPM.cpp.

Best regards.
Jabrane.

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Luc Scholtès (luc) said : 		#3

Hello Jabrane,

As mentioned by Jerome, in the current version of the code, phi_b = phi_c = phi, so whatever the state of the contact (cohesive or not), phi is used for the computation of the shear force:

contactPhysics->tanFrictionAngle = std::tan(std::min(phi1,phi2)

with phi1 and phi2 the friction angles defined in the material functor of your python script.

I have a version of the code where phi_b != phi_c which I may commit in the coming days.

Do you need it?

Luc

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