Help needed with strain extraction for DKT

k_zurawski

Hi,
I'm trying to extract strains and I'm continuously running into some more interesting problems. Could someone look at the EPSI_ELGA, EPSI_ELNO and EPSI_NOEU fields and check where am I making a mistake?

The goal is to extract those fields for bottom and top of the DKT model.
I'm using POURSUITE() command to run the post processing.
Please help.

https://1drv.ms/u/c/e60d0835cd2adf12/EeuUEnVkrYNLpdOZeQTZa6sBavWeqdZjVb2CNalo2fKsRA?e=RwfJdf

k_zurawski

The model consists of plate DKT elements and 6 beams POU_D_E as bolts holding shells together. From the documentation I read that only EPSI field is possible to extract for DKT. So when I add to the result:
Result=CALC_CHAMP(reuse =Result, RESULTAT=Result, CONTRAINTE=('SIGM_ELNO','EFGE_ELNO','SIPO_ELNO','EFGE_NOEU','SIPO_NOEU','SIPM_ELNO',), DEFORMATION='EPSI_ELGA', FORCE=('FORC_NODA','REAC_NODA',), )
I'm getting fatal error related to beam elements not yet supporting calculation of EPSI_ELGA field:

OK, so then let's limit the field to all DKT elements only (ALL_2D group):
Result=CALC_CHAMP(reuse =Result, RESULTAT=Result, CONTRAINTE=('SIGM_ELNO','EFGE_ELNO','SIPO_ELNO','EFGE_NOEU','SIPO_NOEU','SIPM_ELNO',), FORCE=('FORC_NODA','REAC_NODA',), ) Result=CALC_CHAMP(reuse =Result, RESULTAT=Result, GROUP_MA = 'ALL_2D', DEFORMATION='EPSI_ELGA', )
Then I'm getting another fatal error, this time programming related:

So another try was store the result in Result2. This gives the same error.

Does anyone know the way to extract strains?

jeanpierreaubry

k_zurawski
one point:
the .mess is quite clear you are trying to calculate some values at nodes
and some nodes are shared by elements forming a very large angle (here 116.679 degrés)
at these nodes the criteria is meaningless it is not an error just a warning
for example with two beams at 90 degrees at the common node some the bending monent one one beam is a twisting couple in the other one
this is not code_aster it is finite element basics

another one:

in POST_CHAMP to post calculate EPSI_ELGA that is a deformation you need to have calculated some deformation in the previous CALC_CHAMP

k_zurawski

Hello.
The first one we discussed before and as you said, there is no solution to that. So I didn't dig more into details. I obtained displacement and stress results without any problems. But I need information about strain in the joint. Which leads us to the second problem.
This is the only calc champ, I have no more defined before poursuite command. Shouldn't the displacement field automatically calculated and stored by stat_non_line be enough to calculate the deformation? Or maybe I used wrong name of the field for total strains?

jeanpierreaubry

k_zurawski
try that

CALC_CHAMP(
	DEFORMATION=('EPSG_ELGA','EPSG_ELNO','EPSG_NOEU',),#maybe only one of 3
);

an then POST_CHAMP

k_zurawski

jeanpierreaubry sorry, I don't understand. I have calc_champ defined and I'm requesting for EPSI_ELGA.
Then in post champ I'm requesting for EPSI_ELNO and EPSI_NOEU. those two can't be used in calc champ, they exist on 3 couches of the shell.
So after getting error after error I decided to go step by step. I commented out the elno and noeu fields and storing of the fields. I wanted to check if any of the fields can be calculated and eded up with this thread. I'll post later original study file plus the ones related to poursuit(). I'd really appreciate if you could look into it and check what I did wrong. I compared it with the documentation, my old studies and some examples I got during a course. All seems to be ok, but it does not work. I ran out of options.

k_zurawski

This is the content of study file. I saved database.
`DEBUT()
Mesh=LIRE_MAILLAGE(FORMAT='MED',)

Model = AFFE_MODELE(AFFE=(_F(MODELISATION='DKT', TOUT='OUI', PHENOMENE='MECANIQUE', ),
_F(MODELISATION='POU_D_E', GROUP_MA='BOLTS', PHENOMENE='MECANIQUE', ), ),
MAILLAGE=Mesh)

ELAS = DEFI_MATERIAU(ELAS=_F(E=208000, NU=0.28),)

S235 = DEFI_MATERIAU(ELAS=F(E=208000.0, NU=0.28,),
ECRO_LINE=F(D_SIGM_EPSI=1.0, SY=235.0,),)

MatField = AFFE_MATERIAU(AFFE=(_F(TOUT='OUI', MATER=S235),
_F(GROUP_MA='BOLTS', MATER=ELAS),),
MODELE=Model)

Cara = AFFE_CARA_ELEM(MODELE=Model,
COQUE=(
_F(GROUP_MA='11mm_web', EPAIS=11.0,),
_F(GROUP_MA='19mm_v', EPAIS=19.0, VECTEUR=(0,1,0),),
_F(GROUP_MA='19mm_h', EPAIS=19.0,),
_F(GROUP_MA='20mm_stiffeners', EPAIS=20.0, VECTEUR=(0,1,0),),
F(GROUP_MA='20mm_endplate', EPAIS=20.0, VECTEUR=(0,1,0),),
),
POUTRE=F(CARA=('R', ), GROUP_MA='BOLTS', SECTION='CERCLE', VALE=(10.0, ),),
ORIENTATION=_F(CARA='VECT_Y', GROUP_MA=('BOLTS',), VALE=(0, 1, 0),),
)

Pinned=AFFE_CHAR_MECA(MODELE=Model,
DDL_IMPO=_F(GROUP_MA='Pinned',
DX=0,
DY=0,
DZ=0,), )

Rigid=AFFE_CHAR_MECA(MODELE=Model,
LIAISON_SOLIDE=(
_F(GROUP_NO=('HE1','N1',),),
_F(GROUP_NO=('HE2','N2',),),
_F(GROUP_NO=('HE3','N3',),),
_F(GROUP_NO=('HE4','N4',),),
_F(GROUP_NO=('HE5','N5',),),
_F(GROUP_NO=('HE6','N6',),),
_F(GROUP_NO=('HE7','N7',),),
_F(GROUP_NO=('HE8','N8',),),
_F(GROUP_NO=('HE9','N9',),),
_F(GROUP_NO=('HE10','N10',),),
_F(GROUP_NO=('HE11','N11',),),
_F(GROUP_NO=('HE12','N12',),),
),
)
Force=AFFE_CHAR_MECA(MODELE=Model,
FORCE_ARETE=(
_F(GROUP_MA='LOADD_X', FX=11862.4,),
F(GROUP_MA='LOADD-X', FX=-11862.4,),
),
)

thick19=DEFI_CONSTANTE(VALE=9.5)
thick20=DEFI_CONSTANTE(VALE=10.0)
cnt_thck=DEFI_CONTACT(MODELE=Model,
FORMULATION='DISCRETE', # 'CONTINUE' contact, with distance
ZONE=F(GROUP_MA_MAIT='MASTER',
GROUP_MA_ESCL='SLAVE',
DIST_MAIT=thick19,
DIST_ESCL=thick20,
),
)
List=DEFI_LIST_REEL(DEBUT=0.0, # REEL to zwykła lista liczb rzeczywistych ustawionych rosnąco, tu start jest z wartości zero
INTERVALLE=F(JUSQU_A=1.0, NOMBRE=100,), #ilość stepów #JUSQU-until, czyli do 1
)

times=DEFI_LIST_INST(DEFI_LIST=_F(LIST_INST=List,),) #DEFI_LIST_INST w przeciwieństwie do REEL ma możliwość dodatkowego, automatycznego podziału listy na mniejsze kroki, np w przypadku, gdy są problemy ze zbieżnością

LoadRamp=DEFI_FONCTION(NOM_PARA='INST', #INST to jest czas
VALE=(0.0,0.0,
1.0,1.0, ), )

try:
Result=STAT_NON_LINE(MODELE=Model,
CHAM_MATER=MatField,
CARA_ELEM=Cara,
EXCIT=(
_F(CHARGE=Pinned,),
_F(CHARGE=Rigid,),
_F(CHARGE=Force, FONC_MULT=LoadRamp,),
),
CONTACT=cnt_thck,
COMPORTEMENT=(
_F(RELATION='ELAS', DEFORMATION='PETIT', TOUT='OUI',),
F(RELATION='VMIS_ISOT_LINE', DEFORMATION='PETIT',GROUP_MA=('ALL_2D',),),
),
CONVERGENCE=F(ARRET='OUI',
ITER_GLOB_ELAS=25,
ITER_GLOB_MAXI=20),
INCREMENT=_F(LIST_INST=times,),
)
except:
pass

FIN()
`

k_zurawski

This is the content of second comm file used to extract fields for post processing. Most of the lines are commented out, to be reused in the future on some other example or to check where the problem is.
As I said before, placing EPSI in first calc champ is impossible, because of POU_D_E does not support this field. So I added second calc_ champ containing only EPSI field and limited it to be extracted from DKT elements only. This gave me the programming error mentioned in the first post.

POURSUITE()

Result=CALC_CHAMP(reuse =Result,
               RESULTAT=Result,
               CONTRAINTE=('SIGM_ELNO','EFGE_ELNO','SIPO_ELNO','EFGE_NOEU','SIPO_NOEU','SIPM_ELNO',),
               FORCE=('FORC_NODA','REAC_NODA',),
               )
Result2=CALC_CHAMP(reuse =Result,
               RESULTAT=Result,
               GROUP_MA = 'ALL_2D',
               DEFORMATION='EPSI_ELGA',
               )

# NUME_COUCHE = number of layer (there is only 1 layer here)
# NIVE_COUCHE = Level inside the layer: INF=bottom, SUP=top of elm
ResInf=POST_CHAMP(RESULTAT=Result,
                  EXTR_COQUE=_F(NOM_CHAM=('SIGM_ELNO','SIEF_ELGA',),#'EPSI_ELGA','EPSI_ELNO',),
                                NUME_COUCHE=1,
                                NIVE_COUCHE='INF',),
                  )

ResSup=POST_CHAMP(RESULTAT=Result,
                  EXTR_COQUE=_F(NOM_CHAM=('SIGM_ELNO','SIEF_ELGA',),#'EPSI_ELGA','EPSI_ELNO',),
                                NUME_COUCHE=1,
                                NIVE_COUCHE='SUP',),
                  )

# calc more output fields for each of the both results, ResInf and ResSup
ResInf=CALC_CHAMP(reuse =ResInf,
                  RESULTAT=ResInf,
                  CONTRAINTE='SIGM_NOEU',
                  CRITERES=('SIEQ_ELNO','SIEQ_NOEU',),
                  # ~ DEFORMATION='EPSI_NOEU',
                  )

ResSup=CALC_CHAMP(reuse =ResSup,
                  RESULTAT=ResSup,
                  CONTRAINTE='SIGM_NOEU',
                  CRITERES=('SIEQ_ELNO','SIEQ_NOEU',),
                  # ~ DEFORMATION='EPSI_NOEU',
                  )

# ~ #---------------------------------------------------
# ~ # PRINT RESULTS to .resu
# ~ #---------------------------------------------------
# ~ INFO_RESU(RESULTAT=Result)

# ~ IMPR_RESU(FORMAT='RESULTAT',
          # ~ RESU=(_F(RESULTAT=Result,NOM_CHAM='DEPL',                    VALE_MAX='OUI',VALE_MIN='OUI',),
                # ~ _F(RESULTAT=Result,NOM_CHAM=('EFGE_ELNO','SIPO_ELNO','EFGE_NOEU','SIPO_NOEU','SIPM_ELNO',), VALE_MAX='OUI',VALE_MIN='OUI',),
                # ~ _F(RESULTAT=ResInf,NOM_CHAM='SIGM_NOEU',               VALE_MAX='OUI',VALE_MIN='OUI',),
                # ~ _F(RESULTAT=ResInf,NOM_CHAM='SIEQ_ELNO',NOM_CMP='VMIS',VALE_MAX='OUI',VALE_MIN='OUI',),
                # ~ _F(RESULTAT=ResInf,NOM_CHAM='SIEQ_NOEU',NOM_CMP='VMIS',VALE_MAX='OUI',VALE_MIN='OUI',),
                # ~ _F(RESULTAT=ResSup,NOM_CHAM='SIGM_NOEU',               VALE_MAX='OUI',VALE_MIN='OUI',),
                # ~ _F(RESULTAT=ResSup,NOM_CHAM='SIEQ_ELNO',NOM_CMP='VMIS',VALE_MAX='OUI',VALE_MIN='OUI',),
                # ~ _F(RESULTAT=ResSup,NOM_CHAM='SIEQ_NOEU',NOM_CMP='VMIS',VALE_MAX='OUI',VALE_MIN='OUI',),),)

#---------------------------------------------------
# PRINT RESULTS to .rmed
#---------------------------------------------------

IMPR_RESU(FORMAT='MED',
          RESU=(_F(RESULTAT=Result,   NOM_CHAM='DEPL', NOM_CMP=('DX','DY','DZ',),),
				# ~ _F(RESULTAT=Result,NOM_CHAM=('EFGE_ELNO','SIPO_ELNO','EFGE_NOEU','SIPO_NOEU','SIPM_ELNO',),),
				# ~ _F(RESULTAT=ResInf,NOM_CHAM=('SIGM_ELNO','SIGM_NOEU',),),
                _F(RESULTAT=ResInf,NOM_CHAM='SIEQ_ELNO',NOM_CMP='VMIS', NOM_CHAM_MED='VMIS stress at element nodes for BOTTOM [MPa]',),
                _F(RESULTAT=ResInf,NOM_CHAM='SIEQ_NOEU',NOM_CMP='VMIS', NOM_CHAM_MED='VMIS stress nodal values for BOTTOM [MPa]',),
                # ~ _F(RESULTAT=ResInf,NOM_CHAM='EPSI_ELNO',NOM_CHAM_MED='strains at element nodes for BOTTOM [%]'),
                # ~ _F(RESULTAT=ResInf,NOM_CHAM='EPSI_NOEU',NOM_CHAM_MED='strains at nodes for BOTTOM [%]'),
                # ~ _F(RESULTAT=ResSup,NOM_CHAM=('SIGM_ELNO','SIGM_NOEU',),),
                _F(RESULTAT=ResSup,NOM_CHAM='SIEQ_ELNO',NOM_CMP='VMIS', NOM_CHAM_MED='VMIS stress at element nodes for TOP [MPa]]',),
                _F(RESULTAT=ResSup,NOM_CHAM='SIEQ_NOEU',NOM_CMP='VMIS', NOM_CHAM_MED='VMIS nodal values for TOP[MPa]',),
                ),)
# ~ IMPR_CONCEPT(UNITE=80, 
			 # ~ FORMAT='MED',
			 # ~ CONCEPT=(_F(CARA_ELEM=Cara,
                        # ~ #REPERE_LOCAL='NON',  	# default
                        # ~ MODELE=Model, REPERE_LOCAL='ELEM',	#  to visualize local coord systems. MODELE is required
                        # ~ #MODELE=Model, REPERE_LOCAL='ELNO',	#  to visualize local coord systems. MODELE is required
						# ~ ),
                      # ~ _F(CHAM_MATER=MatField,),
					# ~ ),
			# ~ )


FIN()

k_zurawski

I tried to append EPSI field to Result concept and when it failed, to Result2 concept. It doesn't matter. The problem is in the way I'm extracting EPSI_ELGA for DKT elements. The rest is not important yet.
Having stress field and Young modulus the EPSI_ELGA can be calculated, I think.

jeanpierreaubry

k_zurawski
why don't you try what i suggested
i believe i have to add a practical and simple example in my web side!!!

k_zurawski

Now I noticed EPSG, not EPSI...sorry. I'll try that.

k_zurawski

And according to https://codeaster.gitlab.io/doc/docaster/manuals/man_u/u2/u2.01.05/Cin_matique.html#deformations
EPSI_ELGA (_ELNO, _NOEU) are the only strain fields available for all shells and plates (except DKTG and Q4GG, which I haven't used ever)

So what can we do about EPSI and my example?

jeanpierreaubry

k_zurawski
right i did not remember that trouble with DKT element
i have to investigate that

k_zurawski

jeanpierreaubry
so was I unaware that only total strain is possible to extract for shells and plates. I really need information about plastic strain as well, but I know I won't get it.

Thank you for looking into it.

jeanpierreaubry

k_zurawski
maybe with DKTG, i have never done that
complete set of file would help!!

vishwas

Hello,
DKT is meant for small strains. EPSG_ indicates you want plastic strain which is not possible with DKT because it supports only ELASTIC behavior.
DKTG is related to concrete I guess.
Maybe you need to try COQUE_3D.

Anirudh

k_zurawski

vishwas DKT because it supports only ELASTIC behavior.

but I used DKT with F(RELATION='VMIS_ISOT_LINE', DEFORMATION='PETIT',GROUP_MA=('ALL_2D',),) and elasto-plastic material. There's no information VMIS_ISOT_LINE it's possible.

On the other hand U4.51.11 doesn't list DKT and somehow calculation was done:

COQUE_3D is not listed also, but I'm 100% sure I run few simulations using bi-linear material:

This is from the beam above:

try:
    Res=STAT_NON_LINE(MODELE=Model,
                  CHAM_MATER=MatField,
                  CARA_ELEM=Cara,
                  EXCIT=(_F(CHARGE=Fixed,),
								 _F(CHARGE=Sliding,),
								 _F(CHARGE=Fix_Y,),
                         _F(CHARGE=Force,FONC_MULT=LoadFunc,),
                         ),
                  # ~ NEWTON=_F(
                            # ~ PREDICTION='ELASTIQUE',
                            # ~ REAC_ITER=1,
                            # ~ ),
                  COMPORTEMENT=(
				_F(RELATION='VMIS_ISOT_LINE', DEFORMATION='PETIT', GROUP_MA=('ALL_2D',),),
				 ),
                  CONVERGENCE=_F(ARRET='OUI',
                                 ITER_GLOB_ELAS=25,
                                 ITER_GLOB_MAXI=20), 
                  INCREMENT=_F(LIST_INST=times,),
                  # ~ PILOTAGE=_F(TYPE ="LONG_ARC",),
                  )
except:
    pass

k_zurawski

Thanks for the reply.
The reason I used DKT instead of COUQE_3D was limiting number of nodes. This study has been running for 7 hours but using only one core. I read in the documentation that small strains mean up to 5% which is ideal in most of the cases.

AsterO'dactyle

Hello,

The first error "<F> <DVP_1> ... len(tim(cha)) .le. 32" ....
is not from CALC_CHAMP but from IMPR_RESU.

EPSG_ELGA is only for non-linear geometric problems. Not available (but you model is "PETIT", so small strain hypothesis).

k_zurawski

AsterO'dactyle
Hello,
Thank you for your response. I was trying to extract EPSI_ELGA, _ELNO and _NOEU. EPSG was proposed later, but I found in the documentation that for shells and plates only EPSI is possible.
Let's get back to the core of the problem.
How to extract correctly EPSI field for DKT elements from my simulation?