Code_Aster can really replace in many cases traditional solvers, let’s try with a simple problem. This problem will look into a specific contact type, called CGAP in Nastran™ and unilateral contact (“LIAISON_UNIL”) in Code_Aster. 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 |
| DISPLACEMENT=ALL | IMPR_RESU(FORMAT=’RESULTAT’) |
| TIME 600 | See “prob30c.export” file, line “A tpmax 600“ |
| PARAM LGDISP | STAT_NON_LINE(COMPORTEMENT) |
| NLPARM | DEFI_LIST_REEL, DEFI_LIST_INST |
| PBEAML | AFFE_MODELE(MODELISATION=’POU_D_T‘), MACR_CARA_POUTRE, AFFE_CARA_ELEM(POUTRE=_F(SECTION=’GENERALE’)) + AFFE_MATERIAU |
| CBEAM | See “prob30c.mail” file: SEG2 + AFFE_CARA_ELEM(ORIENTATION) + AFFE_CARA_ELEM(POUTRE=_F(GROUPMA)) |
| CGAP | See “prob30c.mail” file: POI1 + AFFE_CARA_ELEM(DISCRET) + AFFE_MODELE(MODELISATION=’DIS_TR‘) + DEFI_MATERIAU(ELAS) |
| PGAP | DEFI_CONTACT(FORMULATION=’LIAISON_UNIL’) + AFFE_MATERIAU |
| MAT1 | DEFI_MATERIAU |
| GRID | See “prob30c.mail” file: COOR_3D |
| SPC1 | AFFE_CHAR_CINE |
| FORCE | AFFE_CHAR_MECA(FORCE_NODALE) |
| ENDDATA | FIN |
After the calculation, we will find the displacements at nodes and compare them with Nastran results (the contact limit is shown by a single point, label “12”) :
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 | -0.009780925 | -0.00977726747071 | 0.037% |
| N3 | -0.03698192 | -0.0369769401306 | 0.013% |
| N4 | -0.07929253 | -0.0792879790551 | 0.006% |
| N5 | -0.1344023 | -0.13439934532 | 0.002% |
| N6 | -0.2000008 | -0.2 | 0.0004% |
| N7 | -0.2737623 | -0.273762838838 | 0.0002% |
| N8 | -0.352976 | -0.352977844004 | 0.0005% |
| N9 | -0.4349158 | -0.434918932333 | 0.0007% |
| N10 | -0.5169551 | -0.516965540582 | 0.002% |
| N11 | -0.5989944 | -0.59901214883 | 0.003% |
First of all, let’s see the Nastran code (file “prob30c.dat”) for this exemple :
SOL 106 TIME 600 CEND TITLE = Non-Linear Gap Element with Non-Coincedent Nodes ECHO = NONE MAXLINES = 999999999 SUBCASE 1 NLPARM = 1 SPC = 1 LOAD = 1 DISPLACEMENT=ALL BEGIN BULK PARAM AUTOSPC NO PARAM WTMASS 1. PARAM LGDISP -1 PARAM,NOCOMPS,-1 NLPARM 1 10 AUTO 5 25 PW NO + A + A .001 1.-7 PBEAML 1 1 I + B + B 2. 1. 1. .1 .1 .1 YES + C + C 1. 2. 1. 1. .1 .1 .1 CBEAM 1 1 1 2 0. 1. 0. CBEAM 2 1 2 3 0. 1. 0. CBEAM 3 1 3 4 0. 1. 0. CBEAM 4 1 4 5 0. 1. 0. CBEAM 5 1 5 6 0. 1. 0. CBEAM 6 1 6 7 0. 1. 0. CBEAM 7 1 7 8 0. 1. 0. CBEAM 8 1 8 9 0. 1. 0. CBEAM 9 1 9 10 0. 1. 0. CBEAM 10 1 10 11 0. 1. 0. PGAP 2 .2 1.+7 CGAP 100 2 6 12 1. 0. 0. MAT1 1 1.+7 .3 .101 GRID 1 0. 0. 0. GRID 2 5. 0. 0. GRID 3 10. 0. 0. GRID 4 15. 0. 0. GRID 5 20. 0. 0. GRID 6 25. 0. 0. GRID 7 30. 0. 0. GRID 8 35. 0. 0. GRID 9 40. 0. 0. GRID 10 45. 0. 0. GRID 11 50. 0. 0. GRID 12 25. -.2 0. SPC1 1 123456 1 12 FORCE 1 9 0 50. 0. -1. 0. ENDDATA
In Code_Aster, you will need to create distinct files for the mesh and the commands and also a mesh file for calculating the section parameters. Let’s start with the main mesh file (file “prob30c.mail”) :
TITRE prob30c Non-Linear Gap Element with Non-Coincedent Nodes FINSF COOR_3D N1 0.0000000000e+00 0.0000000000e+00 0.0000000000e+00 N2 5.0000000000e+00 0.0000000000e+00 0.0000000000e+00 N3 1.0000000000e+01 0.0000000000e+00 0.0000000000e+00 N4 1.5000000000e+01 0.0000000000e+00 0.0000000000e+00 N5 2.0000000000e+01 0.0000000000e+00 0.0000000000e+00 N6 2.5000000000e+01 0.0000000000e+00 0.0000000000e+00 N7 3.0000000000e+01 0.0000000000e+00 0.0000000000e+00 N8 3.5000000000e+01 0.0000000000e+00 0.0000000000e+00 N9 4.0000000000e+01 0.0000000000e+00 0.0000000000e+00 N10 4.5000000000e+01 0.0000000000e+00 0.0000000000e+00 N11 5.0000000000e+01 0.0000000000e+00 0.0000000000e+00 N12 2.5000000000e+01 -2.0000000298e-01 0.0000000000e+00 FINSF POI1 V000012 N12 FINSF SEG2 E1 N1 N2 E2 N2 N3 E3 N3 N4 E4 N4 N5 E5 N5 N6 E6 N6 N7 E7 N7 N8 E8 N8 N9 E9 N9 N10 E10 N10 N11 FINSF GROUP_MA NOM = G1 % Original part : 1 E1 E10 E2 E3 E4 E5 E6 E7 E8 E9 FINSF FIN
And then, the section mesh file (file “poutre.mail”). This mesh does not exists in the Nastran file, it is needed because Code_Aster does not know anything about I-Beams, so we must provide a mesh for the beam section to calculate section properties :
TITRE DI-19-MARS-2017 13:15:15 FINSF % COOR_2D N1 1.00000000000000E+00 0.00000000000000E+00 N2 0.00000000000000E+00 1.11022302462516E-16 N3 0.00000000000000E+00 1.00000000000000E-01 N4 4.50000000000000E-01 1.00000000000000E-01 N5 4.50000000000000E-01 1.90000000000000E+00 N6 2.22044604925031E-16 1.90000000000000E+00 N7 2.22044604925031E-16 2.00000000000000E+00 N8 1.00000000000000E+00 2.00000000000000E+00 N9 1.00000000000000E+00 1.90000000000000E+00 N10 5.50000000000000E-01 1.90000000000000E+00 N11 5.50000000000000E-01 1.00000000000000E-01 N12 1.00000000000000E+00 1.00000000000000E-01 N13 8.00000000000000E-01 2.22044604925031E-17 N14 6.00000000000000E-01 4.44089209850063E-17 N15 4.00000000000000E-01 6.66133814775094E-17 N16 2.00000000000000E-01 8.88178419700125E-17 N17 1.50000000000000E-01 1.00000000000000E-01 N18 3.00000000000000E-01 1.00000000000000E-01 N19 4.50000000000000E-01 3.00000000000000E-01 N20 4.50000000000000E-01 5.00000000000000E-01 N21 4.50000000000000E-01 7.00000000000000E-01 N22 4.50000000000000E-01 9.00000000000000E-01 N23 4.50000000000000E-01 1.10000000000000E+00 N24 4.50000000000000E-01 1.30000000000000E+00 N25 4.50000000000000E-01 1.50000000000000E+00 N26 4.50000000000000E-01 1.70000000000000E+00 N27 3.00000000000000E-01 1.90000000000000E+00 N28 1.50000000000000E-01 1.90000000000000E+00 N29 2.00000000000000E-01 2.00000000000000E+00 N30 4.00000000000000E-01 2.00000000000000E+00 N31 6.00000000000000E-01 2.00000000000000E+00 N32 8.00000000000000E-01 2.00000000000000E+00 N33 8.50000000000000E-01 1.90000000000000E+00 N34 7.00000000000000E-01 1.90000000000000E+00 N35 5.50000000000000E-01 1.70000000000000E+00 N36 5.50000000000000E-01 1.50000000000000E+00 N37 5.50000000000000E-01 1.30000000000000E+00 N38 5.50000000000000E-01 1.10000000000000E+00 N39 5.50000000000000E-01 9.00000000000000E-01 N40 5.50000000000000E-01 7.00000000000000E-01 N41 5.50000000000000E-01 5.00000000000000E-01 N42 5.50000000000000E-01 3.00000000000000E-01 N43 7.00000000000000E-01 1.00000000000000E-01 N44 8.50000000000000E-01 1.00000000000000E-01 N45 3.82651061570731E-01 6.69924241892496E-02 N46 3.82651061570732E-01 1.93300757581075E+00 N47 7.82788561088396E-01 6.69924241892496E-02 N48 7.82788561088396E-01 1.93300757581075E+00 FINSF % SEG2 M1 N1 N13 M2 N13 N14 M3 N14 N15 M4 N15 N16 M5 N16 N2 M6 N2 N3 M7 N3 N17 M8 N17 N18 M9 N18 N4 M10 N4 N19 M11 N19 N20 M12 N20 N21 M13 N21 N22 M14 N22 N23 M15 N23 N24 M16 N24 N25 M17 N25 N26 M18 N26 N5 M19 N5 N27 M20 N27 N28 M21 N28 N6 M22 N6 N7 M23 N7 N29 M24 N29 N30 M25 N30 N31 M26 N31 N32 M27 N32 N8 M28 N8 N9 M29 N9 N33 M30 N33 N34 M31 N34 N10 M32 N10 N35 M33 N35 N36 M34 N36 N37 M35 N37 N38 M36 N38 N39 M37 N39 N40 M38 N40 N41 M39 N41 N42 M40 N42 N11 M41 N11 N43 M42 N43 N44 M43 N44 N12 M44 N12 N1 FINSF % TRIA3 M45 N2 N17 N16 M46 N16 N18 N15 M47 N45 N15 N18 M48 N16 N17 N18 M49 N17 N2 N3 M50 N41 N42 N19 M51 N19 N20 N41 M52 N12 N1 N44 M53 N13 N44 N1 M54 N47 N44 N13 M55 N47 N43 N44 M56 N42 N11 N4 M57 N4 N19 N42 M58 N45 N4 N15 M59 N45 N18 N4 M60 N15 N4 N11 M61 N11 N14 N15 M62 N14 N43 N13 M63 N47 N13 N43 M64 N14 N11 N43 M65 N29 N27 N28 M66 N27 N29 N30 M67 N46 N5 N27 M68 N29 N28 N7 M69 N28 N6 N7 M70 N36 N37 N24 M71 N24 N25 N36 M72 N8 N9 N33 M73 N48 N34 N32 M74 N8 N33 N32 M75 N48 N32 N33 M76 N46 N27 N30 M77 N5 N30 N31 M78 N35 N36 N25 M79 N25 N26 N35 M80 N26 N5 N10 M81 N46 N30 N5 M82 N10 N35 N26 M83 N31 N10 N5 M84 N48 N33 N34 M85 N31 N34 N10 M86 N31 N32 N34 M87 N23 N37 N38 M88 N37 N23 N24 M89 N22 N39 N21 M90 N40 N41 N20 M91 N20 N21 N40 M92 N21 N39 N40 M93 N38 N39 N23 M94 N39 N22 N23 FINSF % GROUP_MA BORDER M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11 M12 M13 M14 M15 M16 M17 M18 M19 M20 M21 M22 M23 M24 M25 M26 M27 M28 M29 M30 M31 M32 M33 M34 M35 M36 M37 M38 M39 M40 M41 M42 M43 M44 FINSF % FIN
Finally, the command file (file “prob30c.comm”) :
# prob30c
# Non-Linear Gap Element with Non-Coincedent Nodes
DEBUT(PAR_LOT='NON',
ERREUR=_F(ERREUR_F='ABORT',),
IGNORE_ALARM=('SUPERVIS_1','MODELISA4_6','MODELISA4_8',),);
MAIL=LIRE_MAILLAGE(FORMAT='ASTER',
VERI_MAIL=_F(VERIF='OUI',),);
MODMECA=AFFE_MODELE(MAILLAGE=MAIL,
AFFE=(_F(MAILLE='V000012',
PHENOMENE='MECANIQUE',
MODELISATION='DIS_TR',),
_F(GROUP_MA='G1',
PHENOMENE='MECANIQUE',
MODELISATION='POU_D_T',),),);
CNS00001=DEFI_CONSTANTE(VALE=0.2,);
CNS00002=DEFI_CONSTANTE(VALE=0.0,);
CNS00003=DEFI_CONSTANTE(VALE=-1.0,);
LST00001=DEFI_LIST_REEL(DEBUT=0.0,
INTERVALLE=_F(JUSQU_A=1.0,
NOMBRE=10,),);
FAUXMAT=DEFI_MATERIAU(ELAS=_F(E=1e-10,
NU=0.0,
RHO=0.0,),);
MAT00001=DEFI_MATERIAU(ELAS=_F(E=10000000.0,
NU=0.3,
RHO=0.101,),);
CHMAT=AFFE_MATERIAU(MAILLAGE=MAIL,
AFFE=(_F(MAILLE='V000012',
MATER=FAUXMAT,),
_F(GROUP_MA='G1',
MATER=MAT00001,),),);
CINE1=AFFE_CHAR_CINE(MODELE=MODMECA,
MECA_IMPO=_F(NOEUD=('N12','N1',),
DX=0.0,
DY=0.0,
DZ=0.0,
DRX=0.0,
DRY=0.0,
DRZ=0.0,),);
CHCONT=DEFI_CONTACT(MODELE=MODMECA,
FORMULATION='LIAISON_UNIL',
ZONE=_F(NOEUD='N6',
NOM_CMP=('DX','DY',),
COEF_IMPO=CNS00001,
COEF_MULT=(CNS00002,CNS00003,),),);
CHARGE1=AFFE_CHAR_MECA(MODELE=MODMECA,
FORCE_NODALE=_F(NOEUD='N9',
FY=-50.0,),);
SECT=LIRE_MAILLAGE(UNITE=21,
FORMAT='ASTER',
VERI_MAIL=_F(VERIF='OUI',),);
TB_POU=MACR_CARA_POUTRE(MAILLAGE=SECT,
ORIG_INER=(0.0,0.0,),
INFO=2,
GROUP_MA_BORD='BORDER',
NOEUD='N23',TABLE_CARA='OUI',NOM='ibeam',);
CAEL=AFFE_CARA_ELEM(MODELE=MODMECA,
POUTRE=_F(SECTION='GENERALE',
GROUP_MA='G1',TABLE_CARA=TB_POU,NOM_SEC='ibeam',),
DISCRET=_F(CARA='K_TR_D_N',
MAILLE='V000012',
VALE=(0.0,0.0,0.0,0.0,0.0,0.0,),),
ORIENTATION=_F(CARA='VECT_Y',
GROUP_MA='G1',
VALE=(0.0,1.0,0.0,),),);
LAUTO1=DEFI_LIST_INST(DEFI_LIST=_F(METHODE='AUTO',
LIST_INST=LST00001,),);
RESU1=STAT_NON_LINE(MODELE=MODMECA,
CHAM_MATER=CHMAT,
CARA_ELEM=CAEL,
EXCIT=(_F(CHARGE=CHARGE1,),
_F(CHARGE=CINE1,),),
CONTACT=CHCONT,
COMPORTEMENT=(_F(MAILLE='V000012',
RELATION='ELAS',),
_F(GROUP_MA='G1',
RELATION='ELAS',),),
INCREMENT=_F(LIST_INST=LAUTO1,),
NEWTON=_F(REAC_ITER=1,),
SOLVEUR=_F(METHODE='MUMPS',
NPREC=8,),
ARCHIVAGE=_F(LIST_INST=LST00001,),);
RESU1=CALC_CHAMP(reuse =RESU1,
RESULTAT=RESU1,
FORCE='REAC_NODA',);
TEST_RESU(RESU=(
_F(RESULTAT=RESU1,
INST=1.0,
NOM_CHAM='DEPL',
NOM_CMP='DY',
NOEUD='N11',
TOLE_MACHINE=0.05,
CRITERE='RELATIF',
VALE_REFE=-0.5989944,
PRECISION=0.05,
REFERENCE='SOURCE_EXTERNE',
VALE_CALC=-0.5989944,),),);
IMPR_RESU(FORMAT='RESULTAT',
RESU=_F(RESULTAT=RESU1,
NOM_CHAM='DEPL',
VALE_MAX='OUI',
VALE_MIN='OUI',),);
IMPR_RESU(FORMAT='MED',
UNITE=80,
RESU=_F(RESULTAT=RESU1,
NOM_CHAM='DEPL',),);
FIN(FORMAT_HDF='OUI',);
You will also need a file to keep everything together ( file “prob30c.export”). This file is the one needed to start the calculation on command line (“as_run prob30c.export”) :
P actions make_etude P memjob 262144 P memory_limit 256.0 P mode interactif P mpi_nbcpu 1 P mpi_nbnoeud 1 P ncpus 1 P testlist verification sequential P time_limit 60.0 P tpsjob 2 P version testing A memjeveux 32.0 A tpmax 60.0 F comm prob30c.comm D 1 F mail prob30c.mail D 20 F mail poutre.mail D 21 F mess prob30c.mess R 6 F resu prob30c.resu R 8 F rmed prob30c.rmed R 81
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