In this post we will see how to model hyperelasticity in a large deformation problem.
This case is taken from a publicy available example on the internet, but the original source is probably this one, for all due credit.
To read this article one will need some knowledge both in Nastran and in Code_Aster.
The translation between Nastran and Code_Aster can be made by using the following correspondances :
| Nastran keyword | Code_Aster keyword |
| BEGIN | DEBUT |
| SOL 106 + SUBCASE | STAT_NON_LINE(EXCIT=_F(FONC_MULT)) |
| TIME 30 | See “prob5.export” file, line “A tpmax 30“ |
| NLPARM | DEFI_LIST_REEL, DEFI_LIST_INST |
| PARAM LGDISP | STAT_NON_LINE(COMPORTEMENT) |
| SPC, SPCD | AFFE_CHAR_MECA(DDL_IMPO) |
| MPC | AFFE_CHAR_MECA(LIAISON_DDL) |
| MATHP | DEFI_MATERIAU(ELAS_HYPER), STAT_NON_LINE(COMPORTEMENT) |
| CHEXA | See “prob5.mail” file: HEXA8 |
| PLSOLID | AFFE_CARA_ELEM(MASSIF=_F(GROUPMA)), STAT_NON_LINE(COMPORTEMENT) |
| GRID | See “prob5.mail” file: COOR_3D |
| ENDDATA | FIN |
Here are Code_Aster results :
Here is a table of comparison between Nastran and Code_Aster results for this case (Nastran values are taken from the pdf file above) :
| Node | Nastran Disp | Code_Aster Disp | Diff % |
| N2 DY N3 DY N6 DY N7 DY | -0.619702 | -0.61746740002 | 0.36% |
| N5 DZ N6 DZ N7 DZ N8 DZ | 0.619702 | 0.61746740002 | 0.36% |
First of all, let’s see the Nastran code (file “prob5.dat”) for this example :
ID NAS103 WORKSHOP 5 SOLUTION
SOL 106
TIME 30
CEND
TITLE = SIMPLE TENSION
SUBTITLE = DISPLACEMENT CONTROL MPCs + 1 SPCD
DISP = ALL
MPC=100
SUBCASE 100 $ UNIAXIAL TENSION
NLPARM=10
SPC=100
LOAD=1000
BEGIN BULK
CHEXA 1 1 1 2 3 4 5 6 +00000P
++00000P7 8
GRID 1 0. 0. 0. 123456
GRID 2 1. 0. 0. 23456
GRID 3 1. 1. 0. 3456
GRID 4 0. 1. 0. 13456
GRID 5 0. 0. -1. 12456
GRID 6 1. 0. -1. 2456
GRID 7 1. 1. -1. 456
GRID 8 0. 1. -1. 1456
MATHP 1 1.52238 .25472 1777.1 0.0 0.0 0.00000 +000001
++000001 2 1 +000002
++000002-.001955
MPC 100 2 1 1. 7 1 -1.
MPC 100 3 1 1. 7 1 -1.
MPC 100 3 2 1. 7 2 -1.
MPC 100 4 2 1. 7 2 -1.
MPC 100 5 3 1. 7 3 -1.
MPC 100 6 1 1. 7 1 -1.
MPC 100 6 3 1. 7 3 -1.
MPC 100 8 2 1. 7 2 -1.
MPC 100 8 3 1. 7 3 -1.
NLPARM 10 48 AUTO 1 YES
PARAM LGDISP 1
PARAM POST -1
PLSOLID 1 1
SPC 100 7 1
SPCD 1000 7 1 6.
ENDDATAn Code_Aster, you will need to create distinct files for the mesh and the commands. We will need to treat this problem as a two-dimensional one and create contact zones.
Let’s start with the main mesh file (file “prob5.mail”) :
TITRE
prob5
SIMPLE TENSION
FINSF
COOR_3D
N1 0.00000000000000E+00 0.00000000000000E+00 0.00000000000000E+00
N2 0.00000000000000E+00 1.00000000000000E+00 0.00000000000000E+00
N3 1.00000000000000E+00 1.00000000000000E+00 0.00000000000000E+00
N4 1.00000000000000E+00 0.00000000000000E+00 0.00000000000000E+00
N5 0.00000000000000E+00 0.00000000000000E+00 -1.00000000000000E+00
N6 0.00000000000000E+00 1.00000000000000E+00 -1.00000000000000E+00
N7 1.00000000000000E+00 1.00000000000000E+00 -1.00000000000000E+00
N8 1.00000000000000E+00 0.00000000000000E+00 -1.00000000000000E+00
FINSF
HEXA8
M9 N1 N4 N3 N2 N5 N8 N7
N6
FINSF
GROUP_MA
PROP_1
M9
FINSF
FINThen, the command file (file “prob5.comm”) :
#Vega++ version 2.5
#Aster version STABLE
DEBUT(PAR_LOT='NON', IGNORE_ALARM=('SUPERVIS_1'))
MAIL=LIRE_MAILLAGE(FORMAT='ASTER',VERI_MAIL=_F(VERIF='OUI',));
MODMECA=AFFE_MODELE(MAILLAGE=MAIL,
AFFE=(
_F(GROUP_MA='PROP_1',
PHENOMENE='MECANIQUE',
MODELISATION=('3D',)),
),
);
# Material original id 1
M42=DEFI_MATERIAU(
ELAS_HYPER=_F(
C10=1.52238,
C01=0.25472,
C20=-0.001955,
RHO=0,
K=1777.1,
),
);
CHMAT=AFFE_MATERIAU(MAILLAGE=MAIL,
AFFE=(
_F(MATER=M42,GROUP_MA=('PROP_1',),),
),
);
CAEL=AFFE_CARA_ELEM(MODELE=MODMECA,
MASSIF=(
_F(GROUP_MA='PROP_1',
ANGL_REP=(0.,0.,0.,),),
),
);
BL66=AFFE_CHAR_MECA(MODELE=MODMECA,
DDL_IMPO=(
_F(NOEUD=('N1', ),DX=0, DY=0, DZ=0 ),
_F(NOEUD=('N3', ),DZ=0 ),
_F(NOEUD=('N4', ),DY=0, DZ=0 ),
_F(NOEUD=('N8', ),DY=0 ),
_F(NOEUD=('N6', ),DX=0 ),
_F(NOEUD=('N2', ),DX=0, DZ=0 ),
_F(NOEUD=('N5', ),DX=0, DY=0 ),
),
);
# ConstraintSet original id : 100
BL67=AFFE_CHAR_MECA(MODELE=MODMECA,
LIAISON_DDL=(
_F(NOEUD=('N2', 'N7', ),
DDL=('DY', 'DY', ),
COEF_MULT=(1, -1, ),
COEF_IMPO=0),
_F(NOEUD=('N3', 'N7', ),
DDL=('DY', 'DY', ),
COEF_MULT=(1, -1, ),
COEF_IMPO=0),
_F(NOEUD=('N7', 'N8', ),
DDL=('DX', 'DX', ),
COEF_MULT=(-1, 1, ),
COEF_IMPO=0),
_F(NOEUD=('N3', 'N7', ),
DDL=('DX', 'DX', ),
COEF_MULT=(1, -1, ),
COEF_IMPO=0),
_F(NOEUD=('N4', 'N7', ),
DDL=('DX', 'DX', ),
COEF_MULT=(1, -1, ),
COEF_IMPO=0),
_F(NOEUD=('N6', 'N7', ),
DDL=('DY', 'DY', ),
COEF_MULT=(1, -1, ),
COEF_IMPO=0),
_F(NOEUD=('N6', 'N7', ),
DDL=('DZ', 'DZ', ),
COEF_MULT=(1, -1, ),
COEF_IMPO=0),
_F(NOEUD=('N7', 'N8', ),
DDL=('DZ', 'DZ', ),
COEF_MULT=(-1, 1, ),
COEF_IMPO=0),
_F(NOEUD=('N5', 'N7', ),
DDL=('DZ', 'DZ', ),
COEF_MULT=(1, -1, ),
COEF_IMPO=0),
),
);
CHMEC62=AFFE_CHAR_MECA(MODELE=MODMECA,
DDL_IMPO=(
_F(NOEUD=('N7',),DX=6, ),
),
);
# Analysis original id : 100
LST00036=DEFI_LIST_REEL(
DEBUT = 0,
INTERVALLE = _F(JUSQU_A = 1,
NOMBRE = 48
),
);
LAUTO32=DEFI_LIST_INST(METHODE='AUTO', DEFI_LIST=_F(LIST_INST=LST00036,),);
RAMP32=DEFI_FONCTION(NOM_PARA='INST', PROL_DROITE='LINEAIRE', VALE=(0,0.0,1,1.0,));
RESU32=STAT_NON_LINE(MODELE=MODMECA,
CHAM_MATER=CHMAT,
CARA_ELEM=CAEL,
EXCIT=(
_F(CHARGE=CHMEC62,FONC_MULT=RAMP32),# Original id:1000
_F(CHARGE=BL66),# Original id:0
_F(CHARGE=BL67),# Original id:100
),
COMPORTEMENT=(
_F(GROUP_MA='PROP_1',RELATION='ELAS_HYPER',DEFORMATION='GROT_GDEP',),
),
INCREMENT=_F(LIST_INST=LAUTO32,),
ARCHIVAGE=_F(LIST_INST=LST00036,),
NEWTON=_F(REAC_ITER=1,),
SOLVEUR=_F(RENUM='PORD',METHODE='MUMPS'),
);
IMPR_RESU(FORMAT='RESULTAT',
RESU=(
_F(RESULTAT=RESU32, NOM_CHAM='DEPL', VALE_MAX='OUI', VALE_MIN='OUI',),
),
);
IMPR_RESU(FORMAT='MED',UNITE=80,
RESU=(
_F(RESULTAT=RESU32, NOM_CHAM='DEPL',),
),
);
FIN()You will also need a file to keep everything together ( file “prob5.export”). This file is the one needed to start the calculation on command line (“as_run prob5.export”) :
P actions make_etude
P mode interactif
P mpi_nbcpu 1
P mpi_nbnoeud 1
P ncpus 1
P version stable
A memjeveux 375.0
A tpmax 30
P memjob 524288
P tpsjob 6
F comm prob5.comm D 1
F mail prob5.mail D 20
F mess prob5.mess R 6
F resu prob5.resu R 8
F rmed prob5.rmed R 80
Code_Aster for Windows 