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Modelling 2D Beam

  • Christian
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9 years 11 months ago #7872 by Christian
Modelling 2D Beam was created by Christian
Hi all,

this one might be a fairly easy thing but anyways I'm somehow stuck.
I want to perform a simple verification test with CA by modeling a 2D Beam exposed to a concentrated load and the free end. When I set up the simulation I use the 'D_PLAN' model but then the results are pretty weird. Does anyone of you know if there is an other model which can be used to model a 2D Beam with no expansion in the third dimension?

Thanks very much!
Cheers H
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9 years 11 months ago #7875 by RichardS
Replied by RichardS on topic Re: Modelling 2D Beam
Hello,
It would be easier to help if you would post the files to reproduce your results,
maybe there's an other problem in your model.

Best regards,
Richard

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9 years 10 months ago - 9 years 10 months ago #7993 by Christian
Replied by Christian on topic Re: Modelling 2D Beam
Hi all,

I'm working again on the 2D beam problem.
So I want to simulate a beam with a 2D mesh (x/y-direction) and a thickness of 5mm. THe simulation should be a static non linear one with a concentrated force at a node at the free end of the beam.
DEBUT();


#######################################################################
## The following lines read in the different meshes of the flap model
Beam=LIRE_MAILLAGE(UNITE=21,
					FORMAT='MED',
					NOM_MED='beam_160x8_2D',
					INFO_MED=1,);
					
#########################################################################
## Material properties
## The material properties are adjusted to the actual physical model

stiff=DEFI_MATERIAU(ELAS=_F(E=207000, #MPa
                            NU=0,
                            RHO=2.713e-9,),); #T/mm3

######################################################################
## Physical phenomenon & type of FE
hexaQ=AFFE_MODELE(MAILLAGE=Beam,
                  INFO=1,
                  AFFE=(_F(TOUT='OUI',
							PHENOMENE='MECANIQUE',
							MODELISATION='COQUE_3D',),
                        ),);
##########################################################################                  
cara1=AFFE_CARA_ELEM(	MODELE=hexaQ,
						COQUE=_F(GROUP_MA='beam',
								 EPAIS=5,
								 ),
								 );                        
#######################################################################						
## Allocate material properties to the mesh
MATE1=AFFE_MATERIAU(MAILLAGE=Beam,
                    AFFE=(_F(TOUT='OUI',
                             MATER=stiff,),
                         ),);  								
###########################################################################
## Define boundary conditions
char1=AFFE_CHAR_MECA(MODELE=hexaQ,
						DDL_IMPO=(_F(GROUP_MA='clamp',			
									DX=0.0,
                                    DY=0.0,
                                    DZ=0.0,
                                    DRX=0.0,
                                    DRY=0.0,),),
								
					INFO=1,);


#########################################################################                  
################################Definition of load : force imposed


load1=AFFE_CHAR_MECA(MODELE=hexaQ,
						FORCE_NODALE=(_F(GROUP_NO='force_n',
									 	FX=6468.75),
									 ),
					INFO=1,);

############################################################################
## Ramp

LREEL=DEFI_LIST_REEL(DEBUT=0.0,
                     INTERVALLE=_F(JUSQU_A=1.0,
                                   NOMBRE=100,),);

LINST=DEFI_LIST_INST(DEFI_LIST=_F(METHODE='MANUEL',
                                  LIST_INST=LREEL,
                                  SUBD_PAS=10,),
                     INFO=2,);

RAMPE=DEFI_FONCTION(
                    NOM_PARA='INST',
                    VALE=(0.0,0.0,
                          1.0,1.0,
                          ),
                    INTERPOL='LIN',);

# Solve system of equations

RESU=STAT_NON_LINE(MODELE=hexaQ,
                   CHAM_MATER=MATE1,
                   CARA_ELEM=cara1,
                   EXCIT=(_F(CHARGE=load1,
                          FONC_MULT=RAMPE,),
                          _F(CHARGE=char1,),),
                   COMPORTEMENT=_F(RELATION='ELAS',
                                   DEFORMATION='GROT_GDEP',
                                   GROUP_MA='beam',),
                   INCREMENT=_F(LIST_INST=LINST,),
                   NEWTON=_F(REAC_INCR=1,
                             PREDICTION='TANGENTE',
                             MATRICE='TANGENTE',
                             REAC_ITER=1,),
                   CONVERGENCE=_F(RESI_GLOB_MAXI=1e-6,
                                  ITER_GLOB_MAXI=30,),
                   SOLVEUR=_F(SYME='OUI',),);
###Write results on a file
IMPR_RESU(FORMAT='MED',
		  UNITE=81,
          RESU=_F(MAILLAGE=Beam,
                  RESULTAT=RESU,
                  NOM_CHAM=('DEPL'),
                  ),);

FIN(FORMAT_HDF='OUI',);


So maybe one of you sees my mistake.

Cheers H
Last edit: 9 years 10 months ago by Christian.
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9 years 10 months ago - 9 years 10 months ago #7994 by RichardS
Replied by RichardS on topic Re: Modelling 2D Beam
Hello,
what is the actual problem you have?

Do you want to model a 2D-problem? If so, why do you use a 3D shell model? Why don't you use a 2D or 3D beam modelization?
Are you sure your constraints are correct (you are missing the DRZ fixation)?

Best regards,
Richard

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Last edit: 9 years 10 months ago by RichardS.
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9 years 10 months ago #7995 by Christian
Replied by Christian on topic Re: Modelling 2D Beam
Thanks for your reply!

My actual problem is, that I want to model a 2D beam but don't know what kind of model (for AFFE_MODELE) I need to use for such a problem.

Cheers,
Christian
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9 years 10 months ago - 9 years 10 months ago #7996 by RichardS
Replied by RichardS on topic Re: Modelling 2D Beam
I think then C_PLAN (plain stress) would be a correct modelization.

Also using a 3D beam element and constraining the DOFs according to a 2D deformation would be ok.

You already said that the results were "weird" in the D_PLAN modelization. I would think that plain strain would be better suited for a simple beam bending,
and of course the forces you apply, are not in N, but N/m, that means, if your beam should be 5mm thick, then your force should be (6468.75N/5mm) compared to the shell model above.

Bets regards,
Richard

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Last edit: 9 years 10 months ago by RichardS.
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