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#1 2019-10-30 20:09:27

marcelo
Member
Registered: 2017-06-20
Posts: 56

Stress analysis on a symmetrical shaft

Hi,

I'm having trouble setting my Aster_Study problem with respect to my model's attachment point (Fixed). Link: encurtador.com.br/hw237.

I am trying to reproduce the behavior of a bearing, but when I will analyze the deformation of the shaft, I see that the condition is not set correctly, mainly because it has a similar analysis as comparative (link: encurtador.com.br/fmuFW).

The difference to the analysis made in commercial software is the use of the '' Remote Displacement '' (link: encurtador.com.br/bBPU7) condition on the opposite side of the shaft symmetry condition. Could someone tell me if it is possible to use such condition in Aster_Study?

Initially I am doing a linear analysis, later I intend to do the nonlinear analysis and later the fatigue analysis.

.comm:

DEBUT(LANG='EN')

mesh = LIRE_MAILLAGE(FORMAT='MED',
                     UNITE=20)

model = AFFE_MODELE(AFFE=_F(MODELISATION=('3D', ),
                            PHENOMENE='MECANIQUE',
                            TOUT='OUI'),
                    MAILLAGE=mesh)

mater = DEFI_MATERIAU(ECRO_LINE=_F(D_SIGM_EPSI=0.0,
                                   SY=579.0),
                      ELAS=_F(E=210000.0,
                              NU=0.3,
                              RHO=7.85e-06))

fieldmat = AFFE_MATERIAU(AFFE=_F(MATER=(mater, ),
                                 TOUT='OUI'),
                         MAILLAGE=mesh)

Load = AFFE_CHAR_MECA(FORCE_FACE=_F(FY=18392.0,
                                    GROUP_MA=('Force', )),
                      MODELE=model)

Fixed = AFFE_CHAR_MECA(DDL_IMPO=_F(DX=0.0,
                                   DY=0.0,
                                   DZ=0.0,
                                   GROUP_MA=('Fixed', )),
                       MODELE=model)

g = AFFE_CHAR_MECA(MODELE=model,
                   PESANTEUR=_F(DIRECTION=(0.0, 0.0, -1.0),
                                GRAVITE=9.8066,
                                GROUP_MA=('Eixo', )))

Symmetry = AFFE_CHAR_MECA(DDL_IMPO=_F(DX=0.0,
                                      GROUP_MA=('Symmetry', )),
                          MODELE=model)

reslin = MECA_STATIQUE(CHAM_MATER=fieldmat,
                       EXCIT=(_F(CHARGE=Load),
                              _F(CHARGE=Fixed),
                              _F(CHARGE=g),
                              _F(CHARGE=Symmetry)),
                       MODELE=model)

reslin = CALC_CHAMP(reuse=reslin,
                    CONTRAINTE=('SIGM_NOEU', 'SIGM_ELNO'),
                    CRITERES=('SIEQ_NOEU', 'SIEQ_ELNO'),
                    FORCE=('REAC_NODA', ),
                    RESULTAT=reslin)

IMPR_RESU(FORMAT='MED',
          RESU=_F(INFO_MAILLAGE='OUI',
                  RESULTAT=reslin),
          UNITE=80)

FIN()

mesh: encurtador.com.br/pxDR9

Last edited by marcelo (2019-10-30 20:12:40)

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#2 2019-10-31 09:09:44

dezsit
Member
Registered: 2012-06-27
Posts: 51
Website

Re: Stress analysis on a symmetrical shaft

Hello,

I did not check your model, but if you want to achieve something like Remote displacement and Remote load, you should check LIAISON_SOLIDE and LIAISON_RBE3.

BR.
dezsit

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#3 2019-11-03 19:01:47

marcelo
Member
Registered: 2017-06-20
Posts: 56

Re: Stress analysis on a symmetrical shaft

Hello,

I tried the LIAISON_RBE3 function, apparently it fits the case I commented, but I am getting errors. I don't know if I'm using the function incorrectly. I attached the files so if possible take a look.

error:

   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
   ! <S> Exception user raised but not interceptee.                                 !
   ! The bases are fermees.                                                         !
   ! Type of the exception: error                                                   !
   !                                                                                !
   !  Erreur utilisateur:                                                           !
   !     On cherche ? imposer une condition aux limites sur le ddl DRY du noeud N8. !
   !     Mais ce noeud ne porte pas ce ddl.                                         !
   !                                                                                !
   !     Conseils :                                                                 !
   !      - v?rifiez le mod?le et les conditions aux limites :                      !
   !         - le noeud incrimin? fait-il partie du mod?le ?                        !
   !         - le noeud porte-t-il le ddl que l'on cherche ? contraindre ?          !
   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Case: encurtador.com.br/gsvJU

EDIT1: I believe the error is related to the node that I 'forced' into geometry. Because when I tried to add a node to the mesh and run the case... I was given the orphan node error, not belonging to the mesh. When I saw the geometry, I saw that this node I had inserted (at 0,0,0) was in the center of one element and not at the junction of both.

Last edited by marcelo (2019-11-03 19:20:50)

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#4 2019-11-04 08:01:52

jeanpierreaubry
Guru
From: nantes (france)
Registered: 2009-03-12
Posts: 3,614

Re: Stress analysis on a symmetrical shaft

hello

the message is very clear
in 3D elements rotational  DOF are not supported
and this is basic in finite element analysis

jean pierre aubry

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#5 2019-11-04 13:14:00

marcelo
Member
Registered: 2017-06-20
Posts: 56

Re: Stress analysis on a symmetrical shaft

jeanpierreaubry wrote:

the message is very clear

Yes, the message from the .mess file is clear. However, I don't know what is wrong or what I should adjust to avoid the mistake...
I made my adjustments based on work I read in the forum.

EDI1: 3D has 6 DOF (3 of translation and 3 of rotation).

Last edited by marcelo (2019-11-04 13:27:41)

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#6 2019-11-04 15:34:43

jeanpierreaubry
Guru
From: nantes (france)
Registered: 2009-03-12
Posts: 3,614

Re: Stress analysis on a symmetrical shaft

without the message file it is impossible to tell what is happening

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#7 2019-11-04 18:15:25

marcelo
Member
Registered: 2017-06-20
Posts: 56

Re: Stress analysis on a symmetrical shaft

jeanpierreaubry wrote:

without the message file it is impossible to tell what is happening

.mess, .comm and .med: encurtador.com.br/gsvJU (Google Drive link)

EDI1: The Fixed condition is not necessary (I unintentionally added it to MECA_STATIQUE, as I had created it only to be able to use it for testing), but... removing it, the same error happens.

Last edited by marcelo (2019-11-04 20:13:43)

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#8 2019-11-04 21:34:07

dezsit
Member
Registered: 2012-06-27
Posts: 51
Website

Re: Stress analysis on a symmetrical shaft

Hi,

I did not check your case deeply, only the message file, but as JeanPierre said, it is clear: 3D solid does not have rotational DOF (it is not aster specific, 3D solid does not have rotational dof in any common mechanical fea package!) so you should remove the '-DRY-DRZ' from yout DDL_ESCL definition. A second thing related to the orphan node: yes aster does not able to handle orphan nodes. But as it was discussed many times, you can define a 0D element on your orphan node, and use a DIS_T or DIS_TR modelisation, depending on your needs, and attach a zero stiffness spring to this 0D element (AFFE_CARA_ELEM -> K_T_D_N or K_TR_D_N or whatever, again depending on the problem you modeling). So you have to provide stiffness for every node, even if it is zero stiffness.

BR,
dezsit.

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#9 2019-11-05 18:46:24

marcelo
Member
Registered: 2017-06-20
Posts: 56

Re: Stress analysis on a symmetrical shaft

dezsit wrote:

3D solid does not have rotational DOF (it is not aster specific, 3D solid does not have rotational dof in any common mechanical fea package!) so you should remove the '-DRY-DRZ' from yout DDL_ESCL definition.

Yes, I know.
I'm just trying to reproduce what I did in commercial software, and the problem, I believe, is precisely trying to reproduce the condition of Remote Displacement (I'll leave this image out of curiosity: encurtador.com.br/lmC23 - pay attention to 6 DOF). Or is it the condition of symmetry?

dezsit wrote:

...and use a DIS_T or DIS_TR modelisation, depending on your needs, and attach a zero stiffness spring to this 0D element (AFFE_CARA_ELEM -> K_T_D_N or K_TR_D_N or whatever, again depending on the problem you modeling).

Yes, on the node I created I added the condition of DIS_TR (6 DOF), but apparently something is wrong. And I made that node not 'orphaned' but in the center of the face.

DEBUT(LANG='EN')

mesh = LIRE_MAILLAGE(FORMAT='MED',
                     UNITE=2)

mesh0 = CREA_MAILLAGE(CREA_POI1=_F(GROUP_NO=('Node', ),
                                   NOM_GROUP_MA=('Node', )),
                      MAILLAGE=mesh)

model = AFFE_MODELE(AFFE=(_F(MODELISATION=('3D', ),
                             PHENOMENE='MECANIQUE',
                             TOUT='OUI'),
                          _F(GROUP_MA=('Node', ),
                             MODELISATION=('DIS_TR', ),
                             PHENOMENE='MECANIQUE')),
                    MAILLAGE=mesh0)

mater = DEFI_MATERIAU(ECRO_LINE=_F(D_SIGM_EPSI=0.0,
                                   SY=579.0),
                      ELAS=_F(E=210000.0,
                              NU=0.3,
                              RHO=7.85e-06))

fieldmat = AFFE_MATERIAU(AFFE=_F(MATER=(mater, ),
                                 TOUT='OUI'),
                         MAILLAGE=mesh0)

Load = AFFE_CHAR_MECA(FORCE_FACE=_F(FY=18392.0,
                                    GROUP_MA=('Force', )),
                      MODELE=model)

g = AFFE_CHAR_MECA(MODELE=model,
                   PESANTEUR=_F(DIRECTION=(0.0, 0.0, -1.0),
                                GRAVITE=9.8066,
                                GROUP_MA=('Eixo', )))

Symmetry = AFFE_CHAR_MECA(DDL_IMPO=_F(DX=0.0,
                                      GROUP_MA=('Symmetry', )),
                          MODELE=model)

Remote = AFFE_CHAR_MECA(LIAISON_RBE3=_F(COEF_ESCL=(1.0, ),
                                        DDL_ESCL=('DX-DY-DZ-DRY-DRZ', ),
                                        DDL_MAIT=('DX', 'DY', 'DZ', 'DRY', 'DRZ'),
                                        GROUP_NO_ESCL=('Remote', ),
                                        GROUP_NO_MAIT=('Node', )),
                        MODELE=model)

reslin = MECA_STATIQUE(CHAM_MATER=fieldmat,
                       EXCIT=(_F(CHARGE=Load),
                              _F(CHARGE=g),
                              _F(CHARGE=Symmetry),
                              _F(CHARGE=Remote)),
                       MODELE=model)

reslin = CALC_CHAMP(reuse=reslin,
                    CONTRAINTE=('SIGM_NOEU', 'SIGM_ELNO'),
                    CRITERES=('SIEQ_NOEU', 'SIEQ_ELNO'),
                    FORCE=('REAC_NODA', ),
                    RESULTAT=reslin)

IMPR_RESU(FORMAT='MED',
          RESU=_F(INFO_MAILLAGE='OUI',
                  RESULTAT=reslin),
          UNITE=80)

FIN()

Last edited by marcelo (2019-11-05 18:49:04)

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#10 2019-11-08 12:55:21

marcelo
Member
Registered: 2017-06-20
Posts: 56

Re: Stress analysis on a symmetrical shaft

Can anybody help me?

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