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#1 2008-05-08 14:50:06

Mawkish1983
Member
Registered: 2008-05-08
Posts: 25

[RESOLU] How to model a CT specimen with elastic-plastic properties?

Hello all,

I have just began my PhD in materials science and I don't have a materials background, so please be patient with me if I'm asking a rediculously easy and obvious question.  My supervisor has asked me to use Code_Aster to model a CT specimen with elastic-plastic properties.  I have been sucessful at running a purely elastic case, but when I've included some plastic properties (taken from a collegue) code_aster generates an error.

My .comm file is listed here:

DEBUT();

Traction=DEFI_FONCTION(NOM_PARA='EPSI',VALE=(0.0,185.28,
                             0.000247,249.39,
                             0.000573,299.33,
                             0.00129,348.83,
                             0.00218,389.91,
                             0.004034,441.8,
                             0.007741,490.4,
                             0.011849,523.06,
                             0.016085,548.64,
                             0.020404,568.18,
                             0.024775,586.2,
                             0.029161,602.76,
                             0.033572,615.24,
                             0.038044,627.87,
                             0.04252,639.88,
                             0.047018,648.36,
                             0.051554,657.59,
                             0.056118,666.71,
                             0.060696,672.47,
                             0.065329,679.39,
                             0.069958,686.72,
                             0.07459,690.57,
                             0.079285,695.96,
                             0.083974,702.05,
                             0.088709,704.7,
                             0.093506,708.98,
                             0.098334,714.0,
                             0.10325,715.75,
                             0.108335,718.91,
                             0.113599,722.93,
                             0.119069,723.07,
                             0.124769,724.24,
                             0.130567,725.36,
                             5.0,1258.0,
                             ),INTERPOL='LIN',PROL_DROITE='LINEAIRE',PROL_GAUCHE='EXCLU',);

MA=DEFI_MATERIAU(ELAS=_F(E=210e12,
                         NU=0.3,),
                 TRACTION=_F(SIGM=Traction,),);

MAIL=LIRE_MAILLAGE(FORMAT='MED',);

MODE=AFFE_MODELE(MAILLAGE=MAIL,
                 AFFE=_F(TOUT='OUI',
                         PHENOMENE='MECANIQUE',
                         MODELISATION='3D',),);

MAIL=MODI_MAILLAGE(reuse =MAIL,
                   MAILLAGE=MAIL,
                   ORIE_PEAU_3D=_F(GROUP_MA='Load',),);

MATE=AFFE_MATERIAU(MAILLAGE=MAIL,
                   AFFE=_F(TOUT='OUI',
                           MATER=MA,),);

CHAR=AFFE_CHAR_MECA(MODELE=MODE,
                    DDL_IMPO=(_F(GROUP_MA='YReflect',
                                 DY=0,),
                              _F(GROUP_MA='ZReflect',
                                 DZ=0,),
                              _F(GROUP_MA='Load',
                                 DX=0,
                                 DZ=0,),),
                    PRES_REP=_F(GROUP_MA='Load',
                                PRES=160e12,),);

RESU=MECA_STATIQUE(MODELE=MODE,
                   CHAM_MATER=MATE,
                   EXCIT=_F(CHARGE=CHAR,),);

RESU=CALC_ELEM(reuse =RESU,
               MODELE=MODE,
               CHAM_MATER=MATE,
               RESULTAT=RESU,
               OPTION=('SIGM_ELNO_DEPL','EQUI_ELNO_SIGM',),
               EXCIT=_F(CHARGE=CHAR,),);

RESU=CALC_NO(reuse =RESU,
             RESULTAT=RESU,
             OPTION=('SIGM_NOEU_DEPL','EQUI_NOEU_SIGM',),);

IMPR_RESU(FORMAT='MED',
          UNITE=80,
          RESU=_F(MAILLAGE=MAIL,
                  RESULTAT=RESU,
                  NOM_CHAM=('SIGM_NOEU_DEPL','EQUI_NOEU_SIGM','DEPL',),),);

FIN();

I am receiving the following error message when code_aster tries to execute the MA=DEFI_MATERIAU command:

<F> <DEFI_MATERIAU> <RCSTOC_03> ERREUR LORS DE LA DEFINITION DE LA COURBE DE                                                       
     TRACTION :SIGM

   !--------------------------------------------------------------------------------!
   ! <F> <JEVEUX_16>                                                                !
   !                                                                                !
   !                                                                                !
   !   Ecrasement aval, l'objet :< ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿ      31 > est peut etre !
   ! écrasé                                                                         !
   !                                                                                !
   !                                                                                !
   !                                                                                !
   ! Cette erreur est fatale. Le code s'arrete.                                     !
   !--------------------------------------------------------------------------------!

I don't know why this is happening but, to be honest, I'm not sure how the plastic properties were imputted.  The list of numbers I assume relate to the relationship between the stress and strain of the material, other than this I have no idea what units are involved!

Units have proven to be a problem for me before.  The dimentions of the specimen I'm modelling are in mm, so I had to be careful when selecting my values for stress etc to take into account this --- I haven't checked the units of the values I inputted for the plastic properties because I don't know what they are to begin with, but could a discrepancy between the elastic and elastic-plastic properties cause this error?

If not, what can?

I'm sorry for being vague and ammeteur-esque --- I really appreciate your help.

Many thanks

-Mawkish

Last edited by Mawkish1983 (2008-09-09 10:05:23)

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#2 2008-05-13 08:13:41

Thomas DE SOZA
Guru
From: EDF
Registered: 2007-11-23
Posts: 3,066

Re: [RESOLU] How to model a CT specimen with elastic-plastic properties?

This is likely a bug, we would need the command file and mesh to reproduce it.

Regards,

TdS

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#3 2008-05-13 08:13:49

sgeniaut
Member
Registered: 2007-12-12
Posts: 169

Re: [RESOLU] How to model a CT specimen with elastic-plastic properties?

The first line of your traction curve seems odd : 0.0,185.28,
that means that, when no deformations occur, the stress is none zero.

You should check your data.

Normally, the first point of a traction curve is (0,0).

Note that in Code_Aster, when defining a traction curve with the command DEFI_FONCTION, the first point (0,0) must not be defined.


Errors should never pass silently

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#4 2008-05-13 08:22:13

Mawkish1983
Member
Registered: 2008-05-08
Posts: 25

Re: [RESOLU] How to model a CT specimen with elastic-plastic properties?

sgeniaut wrote:

You should check your data.

Thanks sgeniaut,

I've posted another question on the forum using the data that I will actually want to use (the data used in this example was from a Code_Aster elastic-plastic tutorial I'd downloaded).  I still can't get it working!  Any help would be very much appreciated!

Thomas DE SOZA wrote:

This is likely a bug, we would need the command file and mesh to reproduce it.

To whom should I send these files?

Many thanks all!

-Mawkish

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#5 2008-09-09 10:04:14

Mawkish1983
Member
Registered: 2008-05-08
Posts: 25

Re: [RESOLU] How to model a CT specimen with elastic-plastic properties?

Date checked and changed, runs fine now.  Silly me!

Thank you all smile

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