how SANS_GROUP_NO_FR works

jacob

Hello,

I would like to ask what actually SANS_GROUP_NO_FR does? I know that it should be used on nodes where is prescribed symmetry and that I understand, but if I exclude all the nodes on the slave surface

_F(ALGO_CONT='STANDARD',

ALGO_FROT='STANDARD',

COULOMB=0.1,

DIST_ESCL=offset,

GROUP_MA_ESCL=('sc_ring', ),

GROUP_MA_MAIT=('mt_ring', ),

SANS_GROUP_NO_FR=('sc_ring', )),

I would expect the contact to behave as it would be without friction.

But, instead all the nodes have status 1 (adhesion). Does that mean that using SANS_GROUP_NO_FR means that all the nodes which are in contact will be glued, so there is no solving for slip/adhesion but everything is assumed to be adhesive?

jacob

CONTACT = DEFI_CONTACT(ALGO_RESO_GEOM='POINT_FIXE',
CONT_STAT_ELAS=10,
FORMULATION='CONTINUE',
FROTTEMENT='COULOMB',
MODELE=MODEL,
ZONE=_F(ALGO_CONT='PENALISATION',
ALGO_FROT='STANDARD',
COEF_FROT=1.0,
COEF_PENA_CONT=50000.0,
COULOMB=0.0,
GROUP_MA_ESCL=('A_SC', ),
GROUP_MA_MAIT=('A_MT', ),
SANS_GROUP_NO_FR=('A_SC', )))

can sameone comment on that?

jeanpierreaubry

jacob
hello

could you be a little less cryptic?
what is the question?

jean pierre aubry

jacob

well, all questions are in my first post.

I don't understand the behavior of using SANS_GROUP_NO_FR.

In documentation:
If the user does not enter the DIRE_EXCL_FROT keyword in 3D, then this amounts to excluding the 2 orthogonal directions of friction and therefore no longer resolving the friction on the eliminated nodes.

But it behaves like contact with friction but with some stiffness.

jeanpierreaubry

does not look exactly the same in the transition area
COEF_FROT=1.0, is very high for true life, is not it?

jacob

very high?

COEF_FROT is just augmentation coefficient

edit (I copied here a wrong setting):

CONTACT = DEFI_CONTACT(ALGO_RESO_GEOM='POINT_FIXE',
CONT_STAT_ELAS=10,
FORMULATION='CONTINUE',
FROTTEMENT='COULOMB',
MODELE=MODEL,
ZONE=_F(ALGO_CONT='PENALISATION',
ALGO_FROT='STANDARD',
COEF_FROT=1.0,
COEF_PENA_CONT=50000.0,
COULOMB=0.2,
GROUP_MA_ESCL=('A_SC', ),
GROUP_MA_MAIT=('A_MT', ),
SANS_GROUP_NO_FR=('A_SC', )))

According:
If the user does not enter the DIRE_EXCL_FROT keyword in 3D, then this amounts to excluding the 2 orthogonal directions of friction and therefore no longer resolving the friction on the eliminated nodes.

I would expect to behave as contact without friction.

jeanpierreaubry

my mistake, i mixed up COEF_FROT and COULOMB values
i am (like you) trying to understand as i have never had to use this keyword so far as my studies gave good result
however i can see a slightly different behavior at the beginning of the friction (bottom right of the graphs)
is GROUP_NO 'A_SC' different from from all the nodes in GROUP_MA 'A_SC'?

jacob

MESH = DEFI_GROUP(reuse=MESH,

              CREA_GROUP_NO=_F(GROUP_MA=('A_SC', 'A_MT')),

              MAILLAGE=MESH)

https://forum.code-aster.org/public/assets/files/2024-11-27/1732697132-821393-contact-friction.zip