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#1 2016-04-11 14:03:32

highpressuretube
Member
From: Werther
Registered: 2014-12-02
Posts: 48

[SOLVED] Mass point connection to mesh

Hi all,

I am having trouble connecting a mass point with the rest of the mesh. I have imported a solid plus single point and generated a mesh with NETGEN 1D-2D-3D with a submesh for the single point.

That does not seem to work as I want since aster later on tells me
  !  le GROUP_MA  mp1  ne fait pas partie du maillage :  MAIL !

What is the best/quickest/easiest/most efficient way to generate an additional mass for modal analysis that which does not have its center point anywhere near the mesh?

I tried with LIASON_RBE3 however without solving my mesh-problem I won't even get close to trying.

Mesh file attached

Comm file as follows:

DEBUT(IGNORE_ALARM='UTILITAI4_2',);

# ignore this alarm when computing modal stresses, because :
# - for modal analysis, there is no external force
# - boundary conditions are already embedded in the data structure
#       produced by CALC_MODES
##########################################


# MESH AND MODEL
##########################################


MAIL=LIRE_MAILLAGE(UNITE=20,
                   FORMAT='MED',);

MODELE=AFFE_MODELE(MAILLAGE=MAIL,
                   AFFE=(_F(GROUP_MA='solid',
                            PHENOMENE='MECANIQUE',
                            MODELISATION='3D',),
                         _F(GROUP_MA='mp1',
                            PHENOMENE='MECANIQUE',
                            MODELISATION='DIS_T',),),);
#########################################


# ELEMENTS' CHARACTERISTICS
#########################################
#########################################


# MATERIAL
#########################################


MAT=DEFI_MATERIAU(ELAS=_F(E=2.1e+11,
                          NU=0.3,
                          RHO=7800.0,),);

CHMAT=AFFE_MATERIAU(MAILLAGE=MAIL,
                    AFFE=_F(TOUT='OUI',
                            MATER=MAT,),);

ELEMCAR=AFFE_CARA_ELEM(MODELE=MODELE,
                       DISCRET=_F(REPERE='GLOBAL',
                                  CARA='M_T_D_N',
                                  GROUP_NO='mp1',
                                  VALE=2.0,),);
##########################################


# BOUNDARY CONDITIONS
##########################################


BLOCAGE=AFFE_CHAR_MECA(MODELE=MODELE,
                       DDL_IMPO=(_F(GROUP_MA='hold',
                                    DY=0.0,),
                                 _F(GROUP_MA='screw',
                                    DX=0.0,
                                    DY=0.0,
                                    DZ=0.0,),),
                       LIAISON_RBE3=_F(GROUP_NO_MAIT='MP1',
                                       DDL_MAIT=('DX','DY','DZ',),
                                       GROUP_NO_ESCL='rail',
                                       DDL_ESCL='DX-DY-DZ',),);
###############################################


# COMPUTATION OF MASS AND STIFFNESS MATRICES
###############################################


ASSEMBLAGE(MODELE=MODELE,
           CHAM_MATER=CHMAT,
           CARA_ELEM=ELEMCAR,
           CHARGE=BLOCAGE,
           NUME_DDL=CO('NUMEDDL'),
           MATR_ASSE=(_F(MATRICE=CO('RIGIDITE'),
                         OPTION='RIGI_MECA',),
                      _F(MATRICE=CO('MASSE'),
                         OPTION='MASS_MECA',),),);
######################################


# MODAL ANALYSIS
######################################


MODES=CALC_MODES(OPTION='PLUS_PETITE',
                 MATR_RIGI=RIGIDITE,
                 MATR_MASS=MASSE,
                 CALC_FREQ=_F(NMAX_FREQ=8,),);
######################################


# MODAL STRESSES
######################################


MODES=CALC_CHAMP(reuse =MODES,
                 RESULTAT=MODES,
                 CONTRAINTE='SIEF_ELGA',);
######################################


# PRINT THE RESULTS
######################################


IMPR_RESU(FORMAT='MED',
          RESU=_F(RESULTAT=MODES,),);

FIN();
#CHECKSUM:2a4ed86a53edfee3997453734a6c82a4  -:FIN CHECKSUM

Last edited by highpressuretube (2016-04-12 11:53:28)

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#2 2016-04-12 08:05:49

highpressuretube
Member
From: Werther
Registered: 2014-12-02
Posts: 48

Re: [SOLVED] Mass point connection to mesh

Hi all,

just looked into the exported mesh file with other tools than salome-meca (i.e. gmsh etc) and the single point node mp1 is not exported. I know tried to manually add a single node (Menu:Modification:Add:Node) in the mass center but salome does not accept the addition. It only creates and empty group.

Anybody, any idea as to how to get that node into the mesh with salome?

Regards,
highpressuretube

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#3 2016-04-12 09:18:04

jeanpierreaubry
Guru
From: nantes (france)
Registered: 2009-03-12
Posts: 3,773

Re: [SOLVED] Mass point connection to mesh

hello

you have to:
1- in Salome, create a group on the node
2- in the .comm file use CREA_POI1 to create a 0D element on this node
3- give the DIS_T property and M_T_D_N value to this element (it is an element, not a node)

this is explained in appendix 4.1 of my book

jean pierre aubry


consider reading my book
freely available here https://framabook.org/beginning-with-code_aster/

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#4 2016-04-12 09:20:47

highpressuretube
Member
From: Werther
Registered: 2014-12-02
Posts: 48

Re: [SOLVED] Mass point connection to mesh

Well, getting closer. I added aster code:

MAILMP=CREA_MAILLAGE(MAILLAGE=MAIL,
                     CREA_POI1=_F(NOM_GROUP_MA='mp1',
                                  GROUP_NO='mp1',),); 

Now GROUP_MA mp1 is found and may be used. However GROUP_NO mp1 still does not exist!

In order to apply my LIAISON_RBE I need to access a node group. What can I do???!!!

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#5 2016-04-12 09:26:07

highpressuretube
Member
From: Werther
Registered: 2014-12-02
Posts: 48

Re: [SOLVED] Mass point connection to mesh

Thanks for the hint to the book, I saw you answer just after my last post. But exactly from your book I got the idea :-)

So my status is:

MAIL=LIRE_MAILLAGE(UNITE=20,
                   FORMAT='MED',);

MAILMP=CREA_MAILLAGE(MAILLAGE=MAIL,
                     CREA_POI1=_F(NOM_GROUP_MA='mp1',
                                  GROUP_NO='mp1',),);

MODELE=AFFE_MODELE(MAILLAGE=MAILMP,
                   AFFE=(_F(TOUT='OUI',
                            PHENOMENE='MECANIQUE',
                            MODELISATION='3D',),
                         _F(GROUP_MA='mp1',
                            PHENOMENE='MECANIQUE',
                            MODELISATION='DIS_T',),),);

MAT=DEFI_MATERIAU(ELAS=_F(E=2.1e+11,
                          NU=0.3,
                          RHO=7800.0,),);

CHMAT=AFFE_MATERIAU(MAILLAGE=MAILMP,
                    AFFE=_F(TOUT='OUI',
                            MATER=MAT,),);

ELEMCAR=AFFE_CARA_ELEM(MODELE=MODELE,
                       DISCRET=_F(CARA='M_T_D_N',
                                  GROUP_MA='mp1',
                                  VALE=2.0,),);
BLOCAGE=AFFE_CHAR_MECA(MODELE=MODELE,
                       DDL_IMPO=(_F(GROUP_MA='hold',
                                    DY=0.0,),
                                 _F(GROUP_MA='screw',
                                    DX=0.0,
                                    DY=0.0,
                                    DZ=0.0,),),
                       LIAISON_RBE3=_F(GROUP_NO_MAIT='mp1',
                                       DDL_MAIT=('DX','DY','DZ',),
                                       GROUP_NO_ESCL='rail',
                                       DDL_ESCL='DX-DY-DZ',),);

I applied the characteristics on group_ma instead of group_no just because on group_ma I did not get an error message but without understanding why I could not use group_no mp1. And then for the boundary condition I am stuck, because LIAISON-RBE does not offer me group_MA_MAIT :-(

Regards,
highpressuretube

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#6 2016-04-12 11:52:39

highpressuretube
Member
From: Werther
Registered: 2014-12-02
Posts: 48

Re: [SOLVED] Mass point connection to mesh

I have know used LIAISON_SOLIDE instead of LIAISON_RBE3 and as such avoided the problem.

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#7 2016-04-12 12:10:34

jeanpierreaubry
Guru
From: nantes (france)
Registered: 2009-03-12
Posts: 3,773

Re: [SOLVED] Mass point connection to mesh

SOLVED ? are you sure ?
do you really understand what LIAISON_SOLID implies
it is very different from RBE3


consider reading my book
freely available here https://framabook.org/beginning-with-code_aster/

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#8 2016-04-13 07:49:22

highpressuretube
Member
From: Werther
Registered: 2014-12-02
Posts: 48

Re: [SOLVED] Mass point connection to mesh

Hi jeanpierreaubry,

I put it solved, because the original question, how to include the mass point into the mesh was solved by looking into your book and if I need to continue with that topic because LIAISON_SOLIDE is to far off, I would open a new thread in the Code_Aster usage forum because the salome problem obviously is solved, isn't it?

Thanks again,
Katrin

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