Alessia]]>

Thank you so much for your answer. You confirmed what I imagined, but is this the only way to consider non-linear elastic behavior? I would like to insert a constitutive law obtained from laboratory tests to describe the behavior of a particular material, do you think it is possible?

For that case, you can define function for the material properties (copied from book by jean)

e.g.

s235elpl=DEFI_FONCTION(

NOM_PARA=’EPSI’ ,NOM_RESU=’SIGMA’ ,

VALE=(

#there should not be a point at 0.0, 0.0

#0.0000, 0.0

0 . 0 0 1 1 4 , 2 4 0 . 0 ,

0 . 0 0 1 2 , 2 4 1 . 0 ,

0 . 0 0 2 0 , 2 4 1 . 6 ,

0 . 0 0 5 0 , 2 4 4 . 0 ,

0 . 0 1 0 0 , 2 4 8 . 0 ,

0 . 0 1 5 0 , 2 5 2 . 0 ,

0 . 0 5 0 0 , 2 8 0 . 0 ,

0 . 1 0 0 0 , 3 2 0 . 0 ,

0 . 1 5 0 0 , 3 6 0 . 0 ,

0 . 2 0 0 0 , 3 8 0 . 0 ,

0 . 4 0 0 0 , 4 2 0 . 0 ,

) ,

INTERPOL=’LIN’ ,

PROL_DROITE=’LINEAIRE’ ,

PROL_GAUCHE=’CONSTANT’ ,

) ;

and define the material and apply it

steel=DEFI_MATERIAU(

ELAS=_F(E=210000 ,NU = 0 . 3 , ) ,

TRACTION=_F(SIGM=s235elpl , ) ,

) ;

mate=AFFE_MATERIAU(

MAILLAGE=mesh1 ,

AFFE=_F(TOUT=’OUI’ ,MATER=steel , ) ,

) ;

and perform analysis

resunl=STAT_NON_LINE(

MODELE=mod1 ,

CHAM_MATER=mate ,

EXCIT=(

_F(CHARGE=fix1 , ) ,

_F(CHARGE=load , TYPE_CHARGE=’FIXE_CSTE’ ,FONC_MULT=load_m , ) ,

) ,

COMPORTEMENT=_F(

RELATION=’VMIS_ISOT_TRAC’ , #U4.51.11 para 4.3.1.3

DEFORMATION=’SIMO_MIEHE’ , #U4.51.11 para 4.5.3

) ,

INCREMENT=_F(LIST_INST=linst , ) ,

NEWTON=_F(

PREDICTION=’TANGENTE’ ,

MATRICE=’TANGENTE’ ,

REAC_ITER=1 ,

) ,

CONVERGENCE=_F(RESI_GLOB_RELA=1e?4,ITER_GLOB_MAXI=3 0 0 , ) ,

) ;

Elastic non-linear with increasing stiffness is ELAS_HYPER (hyperelastic material as Mooney-Rivlin, neo-hookean or Signorini model)

You cannot use TRACTION. It's only for (visco)-plastic material (generalized standard materials) with strain hardening

I'm trying to model a material with non-linear elastic behavior with increasing stiffness for a static non linear analysis. I've tried several things but none of them work:

- DEFI_MATERIAU - TRACTION but since the stiffness increasing the software gives an error;

- I've defined a function with Young's modulus-EPSI trend, I've inserted it in ELAS_FO but it gives an interpolation error;

- I interpolated the constitutive law into a polynomial as a function of the deformations and defined it in FORMULE but the independent variable is not recognized

I would like to know if there is a possibility to insert a non-linear behavior with increasing stiffness.

Thank you in advance for sharing your knowledge

Alessia

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