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#1 Code_Aster usage » Matrix singular: harmonic response - fluid structure interaction » 2015-03-28 17:37:20

lagrange
Replies: 0

Dear Code_Aster users,

I'm trying to calculate the harmonic response of a system with two nested solid domains (3D) and one nested fluid domain (3D_FLUIDE).
Unfortunately the matrix is always singular no matter which boundary conditions are used.
Do you know if such a configuration is supported by Code_Aster or if there is something wrong in the mesh or command file?

Best regards,
Lagrange

#2 Code_Aster usage » ABNORMAL_ABORT in eigenanalyis » 2015-03-21 18:14:04

lagrange
Replies: 1

Dear Code_Aster developers,

There seems to be a memory bug in Code_Aster when running an eigenanalyis.
See the attached files.

Best regards,
Lagrange

#3 Code_Aster usage » Fluid structure interaction with 3D_FLUIDE » 2015-02-15 20:07:33

lagrange
Replies: 1

Dear Code_Aster users and developers,

Some time ago I have created a simple example with fluid structure interaction (3D_FLUIDE).
The model consists of a fluid tank, a piston and a spring. Unfortunately the eigenanalysis is not working any longer.
Do you know if there were some changes in Code_Aster in that area?

Best regards,
Lagrange

#4 Code_Aster usage » Huge displacement in z-direction for a 2D model with contact » 2014-09-08 16:36:14

lagrange
Replies: 1

Dear Code_Aster developers,

If I run the simulation in the attached file, I get huge values for the displacement in z-direction in the area with unilateral contact.
Since the model is a 2D one, the displacement in z-direction should be zero in any case. So it seems to be a bug.
Nevertheless the results for the reaction force seem to be correct.

Best regards,
Lagrange

#6 Code_Aster installation » Failed to launch aster via astk (error while loading shared libraries » 2014-09-01 11:56:48

lagrange
Replies: 2

Dear Code_Aster users and developers,

I have installed SALOME-MECA-2014.2-LGPL-1.
If I try to launch aster via astk, I get the following error message:

error while loading shared libraries: libifport.so.5: cannot open shared object file: No such file or directory

The full log file output is:

###############################################
           Client name : CAE-linux-server
              Username : lagrange
-----------------------------------------------
           Server name : localhost
              Username : lagrange
                  Node : CAE-linux-server
              Platform : LINUX64
-----------------------------------------------
    Code_Aster version : /opt/salome/V2014_2/tools/Code_aster_frontend_20142/../Code_aster_stable_1160/share/aster
-----------------------------------------------
            Time (min) : 6000
           Memory (MB) : 2750.0
  Number of processors : 2   (OpenMP)
       Number of nodes : 1   (MPI)
  Number of processors : 1   (MPI)
                  Mode : interactif
-----------------------------------------------
            Debug mode : nodebug
-----------------------------------------------
            BTC script : generated
-----------------------------------------------
   Version ASTK Server : 1.13.4
   Version ASTK Client : 1.13.4
###############################################

--------------------------------------------------------------------------------
 Code_Aster execution

<INFO> prepare environment in /tmp/lagrange-CAE-linux-server-interactif.13109-CAE-linux-server
copying .../aster/elements...                                           [  OK  ]

--------------------------------------------------------------------------------
 Copying datas

copying .../KXV95-sleeve-contact/sleeve-contact.comm...                 [  OK  ]
copying .../KXV95-sleeve-contact/sleeve-contact.med...                  [  OK  ]
<INFO> Parameters : memory 2750 MB - time limit 360000 s

--------------------------------------------------------------------------------
 Content of /tmp/lagrange-CAE-linux-server-interactif.13109-CAE-linux-server before execution

total 20228
drwx------  4 lagrange lagrange     4096 2014-09-01 10:35 .
drwxrwxrwt 20 root     root         4096 2014-09-01 10:35 ..
-rw-r--r--  1 lagrange lagrange     1531 2014-09-01 10:35 13109-CAE-linux-server.export
-rw-r--r--  1 lagrange lagrange     2281 2014-09-01 10:35 config.txt
-rw-r--r--  1 lagrange lagrange 19660808 2014-09-01 10:35 elem.1
-rw-r--r--  1 lagrange lagrange     4416 2014-09-01 10:35 fort.1.1
-rw-r--r--  1 lagrange lagrange  1012694 2014-09-01 10:35 fort.20
drwxr-xr-x  2 lagrange lagrange     4096 2014-09-01 10:35 REPE_OUT
drwxr-xr-x  2 lagrange lagrange     4096 2014-09-01 10:35 RESU_ENSIGHT


--------------------------------------------------------------------------------
 Code_Aster run

<INFO> Command line 1 :
<INFO> /opt/salome/V2014_2/tools/Code_aster_frontend_20142/../Code_aster_stable_1160/share/aster/../../bin/aster /opt/salome/V2014_2/tools/Code_aster_frontend_20142/../Code_aster_stable_1160/share/aster/../../lib/aster/Execution/E_SUPERV.py -commandes fort.1  -num_job 13109-CAE-linux-server -mode interactif -rep_outils /opt/salome/V2014_2/tools/Code_aster_frontend_20142/outils -rep_mat /opt/salome/V2014_2/tools/Code_aster_frontend_20142/../Code_aster_stable_1160/share/aster/materiau -rep_dex /opt/salome/V2014_2/tools/Code_aster_frontend_20142/../Code_aster_stable_1160/share/aster/datg -suivi_batch -memjeveux 343.75 -tpmax 360000
/opt/salome/V2014_2/tools/Code_aster_frontend_20142/../Code_aster_stable_1160/share/aster/../../bin/aster: error while loading shared libraries: libifport.so.5: cannot open shared object file: No such file or directory
EXECUTION_CODE_ASTER_EXIT_13109-CAE-linux-server=127
<INFO> Code_Aster run ended, diagnostic : NO_RESU_FILE

--------------------------------------------------------------------------------
 Content of /tmp/lagrange-CAE-linux-server-interactif.13109-CAE-linux-server after execution

.:
total 20240
drwx------  4 lagrange lagrange     4096 2014-09-01 10:35 .
drwxrwxrwt 20 root     root         4096 2014-09-01 10:35 ..
-rw-r--r--  1 lagrange lagrange     1531 2014-09-01 10:35 13109-CAE-linux-server.export
-rw-r--r--  1 lagrange lagrange     2281 2014-09-01 10:35 config.txt
-rw-r--r--  1 lagrange lagrange 19660808 2014-09-01 10:35 elem.1
-rw-r--r--  1 lagrange lagrange     4416 2014-09-01 10:35 fort.1
-rw-r--r--  1 lagrange lagrange     4416 2014-09-01 10:35 fort.1.1
-rw-r--r--  1 lagrange lagrange  1012694 2014-09-01 10:35 fort.20
-rw-r--r--  1 lagrange lagrange       53 2014-09-01 10:35 fort.6
drwxr-xr-x  2 lagrange lagrange     4096 2014-09-01 10:35 REPE_OUT
drwxr-xr-x  2 lagrange lagrange     4096 2014-09-01 10:35 RESU_ENSIGHT

REPE_OUT:
total 8
drwxr-xr-x 2 lagrange lagrange 4096 2014-09-01 10:35 .
drwx------ 4 lagrange lagrange 4096 2014-09-01 10:35 ..


--------------------------------------------------------------------------------
 Size of bases


--------------------------------------------------------------------------------
 Copying results


<A>_COPYFILE       no such file or directory: fort.80

copying .../fort.6...                                                   [  OK  ]

<A>_COPYFILE       no such file or directory: fort.8


NO_RESU_FILE       Code_Aster run ended


 
 ---------------------------------------------------------------------------------
                                            cpu     system    cpu+sys    elapsed
 ---------------------------------------------------------------------------------
   Preparation of environment              0.01       0.04       0.05       0.04
   Copying datas                           0.08       0.02       0.10       0.04
   Code_Aster run                          0.06       0.00       0.06       0.01
   Copying results                         0.03       0.00       0.03       0.01
 ---------------------------------------------------------------------------------
   Total                                   0.44       0.13       0.57       0.25
 ---------------------------------------------------------------------------------

as_run 1.13.4

------------------------------------------------------------
--- DIAGNOSTIC JOB : NO_RESU_FILE
------------------------------------------------------------


EXIT_CODE=4

My plateform is Ubuntu 10.0.4:

$uname -a
Linux CAE-linux-server 2.6.32-65-generic #131-Ubuntu SMP Fri Aug 15 20:39:31 UTC 2014 x86_64 GNU/Linux

However if create a .export file and launch aster via as_run, it works.

Any idea what is the problem?

Best regards
Lagrange

#7 Re: Code_Aster usage » [Discussion] How to model a hinge bc allowing large rotations » 2014-01-13 19:58:39

RichardS wrote:

Hello  Lagrange,
I don't fully understand your approach, but it seems interesting.
Could you please clearify what you mean by "the first" and "the second" part?

Best regards,
Rochard

OK I will describe it in more detail.
The first part could be a bolt for example and the second part would be the matching part with the cylindrical hole. Let's call it hinge.

Your command file could be like ...

MODELE=AFFE_MODELE(MAILLAGE=MAIL,
                   AFFE=(_F(GROUP_MA=('BOLT','HINGE',),
                            PHENOMENE='MECANIQUE',
                            MODELISATION='3D',),
                         _F(GROUP_MA=('BOLT_BEAM','HINGE_BEAM',),
                            PHENOMENE='MECANIQUE',
                            MODELISATION='POU_D_T_GD',),),);

CHARGE=AFFE_CHAR_MECA(MODELE=MODELE,
                      LIAISON_DDL=(_F(GROUP_NO=('BOLT_HINGE1','HINGE_HINGE1',),
                                      DDL=('DX','DX',),
                                      COEF_MULT=(1,-1,),
                                      COEF_IMPO=0,),
                                   _F(GROUP_NO=('BOLT_HINGE1','HINGE_HINGE1',),
                                      DDL=('DY','DY',),
                                      COEF_MULT=(1,-1,),
                                      COEF_IMPO=0,),
                                   _F(GROUP_NO=('BOLT_HINGE1','HINGE_HINGE1',),
                                      DDL=('DZ','DZ','DZ',),
                                      COEF_MULT=(1,-1,),
                                      COEF_IMPO=0,),),);

Where BOLT and HINGE could be a groups of tetrahedrons or hexahedrons.
BOLT_HINGE1 and HINGE_HINGE1 would be two groups with exactly one node. Those nodes should be coincident and the position of those nodes should be at the centerline of the hinge.
The group BOLT_BEAM should contain SEG2 elements. The first node of each SEG2 element should be BOLT_HINGE1 and the second node should be one node at the sliding surface of BOLT. In the same way HINGE_BEAM should contain SEG2 elements with the first node HINGE_HINGE1 and the second node at the sliding surface of HINGE.
That procedure has to be repeated a second time with BOLT_HINGE2 and HINGE_HINGE2 in order to have a hinge behavior and not a spherical joint.

Best regards,
Lagrange

#8 Re: Code_Aster usage » [SOLVED] base acceleration as a load in a harmonic analysis » 2014-01-10 21:11:03

jeanpierreaubry wrote:

hello Johannes and happy new year

sorry for my last ironic answer. To be clear now: There is no acceleration load in AFFE_CHAR_MECA

of course yes!
with the keyword PESANTEUR
look here
http://www.code-aster.org/forum2/viewtopic.php?id=18760

but i wonder whether this claim holds true for a dynamic anlysis?

lagrange wrote:

Dear Mr. Ackva,

Is it possible to apply a coordinate transformation?

In the simplest case you could clamp those points where you want to apply the prescribed acceleration and apply a gravity force with the negative acceleration to the rest of the structure. In that case you will get the relative motion of the structure with respect to the clamped nodes as result.

Best regards,
Lagrange

jeanpierre aubry

I cannot see any reason why it sould not work.

For example let us consider a two degree of freedom system:
m_1 \ddot{u}_1 + d_{12} (\dot{u}_1 - \dot{u}_2) + s_{12} (u_1 - u_2) = p_1

u_1 ... the unknown displacement
\ddot{u}_2 ... the known acceleration

One coud substitude:
\Delta u = u_1 - u_2
\Delta\dot{u} = \dot{u}_1 - \dot{u}_2
\Delta\ddot{u} = \ddot{u}_1 - \ddot{u}_2

Finally one gets an equation for the relative displacement $\Delta{u}$:
m_1 \Delta\ddot{u} + d_{12} \Delta\dot{u} + s_{12} \Delta{u} = p_1 - m_1 \ddot{u}_2

Best regards,
Lagrange

#9 Re: Code_Aster usage » [Discussion] How to model a hinge bc allowing large rotations » 2014-01-10 20:46:16

Hello,

What about using beam elements (POU_DT_GD) in combination with LIAISON_DLL?

For example you could use two pairs of two coincident nodes at the axis of the hinge. For each pair of nodes one node would be connected to the first part by means of beam elements and the other node would be connected to the second part also by means of beam elements. For each pair of coincident nodes one LIAISON_DLL connection could be defined which connects only the translational DOF's but not the rotational DOF's. With that approach all the nonlinear stuff would be handled by the beam elements and only the linear constraints for translational DOF's would be handled by LIAISON_DLL.

Of course that approach always adds spurious elasticity/stiffness.
The best solution would be to use LIAISON_RB3 links instead of the beams. But they cannot be used for large rotations as far as I know.

Best regards,
Lagrange

#10 Re: Code_Aster usage » Post buckling and stabilization of singular modes » 2014-01-10 20:20:55

Hello,

As far as I understand you are interested in post buckling analysis.
In that case see for example u4.51.03 section 3.12 (Key word PILOTAGE of STAT_NON_LINE)
See also http://www.code-aster.org/forum2/viewto … 512#p16512

Best regards,
Lagrange

#11 Re: Code_Aster usage » [SOLVED] base acceleration as a load in a harmonic analysis » 2014-01-04 14:23:48

Dear Mr. Ackva,

Is it possible to apply a coordinate transformation?

In the simplest case you could clamp those points where you want to apply the prescribed acceleration and apply a gravity force with the negative acceleration to the rest of the structure. In that case you will get the relative motion of the structure with respect to the clamped nodes as result.

Best regards,
Lagrange

#12 Code_Aster installation » Segmentation fault in _PyOS_GetOpt with Code_Aster 11.4 » 2013-07-13 17:19:16

lagrange
Replies: 1

Dear Code_Aster developers,

I have tried to install Code_Aster from source with gcc-4.4.
The compilation of aster works, but if I run "aster --help" I get a segmentation fault.

The output from gdb is:

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff6b1fabf in _PyOS_GetOpt () from /usr/lib/libpython2.6.so.1.0
(gdb) bt full
#0  0x00007ffff6b1fabf in _PyOS_GetOpt () from /usr/lib/libpython2.6.so.1.0
No symbol table info available.
#1  0x00007ffff6b23e89 in Py_Main () from /usr/lib/libpython2.6.so.1.0
No symbol table info available.
#2  0x000000000049e11a in main ()
No symbol table info available.

I have provided my setup configuration and a core dump file.

Any idea what is the problem?

Best regards,
Lagrange

#13 Re: Code_Aster usage » DYNA_LINE_HARM gives incorrect results if the frequency is negative » 2013-07-13 11:13:21

boyere wrote:

But how do you come to input a negative frequency ?

I'm imposing the rotating and oscillating components of the inertia forces from a slider crank mechanism as excitation for a finite element model. As a convention, I assume that if the angular velocity of the crankshaft is negative in mathematical sense, also the frequencies of excitation are negative since I'm working in the frequency domain.

As a workaround I could use the absolute value of the angular velocity and then compute the complex conjugate value of the solution.

But I agree with you, that Code_Aster should check for negative frequencies.

Best regards,
Lagrange

#14 Code_Aster usage » CALC_MATR_ELEM fails with non symmetric damping matrix. » 2013-07-10 12:34:45

lagrange
Replies: 1

Dear all,

I would like to use a non symmetric damping matrix in my command file.
My command file contains code like that:

...
CARA_ELE=AFFE_CARA_ELEM(MODELE=MODELE,
...
                        DISCRET=(
                    _F(GROUP_NO='STATOR_1',
                       CARA='A_TR_N',
                       VALE=(...,),
                       SYME='NON'),
                      ));
...
RH=CALC_MATR_ELEM(OPTION='RIGI_MECA_HYST',...)

If I run Code_Aster, I get the following error message:

   !-------------------------------------------------------!
   ! <EXCEPTION> <DVP_1>                                   !
   !                                                       !
   !    Erreur de programmation : condition non respectée. !
   !                                                       !
   !                                                       !
   !                                                       !
   ! Il y a probablement une erreur dans la programmation. !
   ! Veuillez contacter votre assistance technique.        !
   !-------------------------------------------------------!

This error looks strange because the damping matrix should not be required in order to compute the complex stiffness matrix.

Best regards,
Lagrange

#15 Code_Aster usage » DYNA_LINE_HARM gives incorrect results if the frequency is negative » 2013-07-09 15:35:33

lagrange
Replies: 2

Dear all,

It seems that the results of DYNA_LINE_HARM are incorrect if the frequency is negative.
See the model in the attached file.

The correct result should be
u =    -1.72671
for both frequencies.

But the results from Code_Aster are:
u = -1.72671E+00 for f=0.2Hz
and
u = 3.87727E-01 for f=-0.2Hz

Best regards,
Lagrange

#16 Re: Code_Aster usage » [SOLVED] How to access stiffness from script python » 2013-07-08 12:21:04

I see, in that case a different approach is needed.

Is it possible to split your mesh into different parts?
One part will be the same for every analysis.
Other parts could contain those parts of the mesh which are present sometimes and sometimes not.

In that case you could do:

M_BASE=LIRE_MAILLAGE(UNITE=20, ...);
M_PART1=LIRE_MAILLAGE(UNITE=21, ...);
M_PART2=LIRE_MAILLAGE(UNITE=22, ...);
M_VAR1=ASSE_MAILLAGE(MAILLAGE_1=M_BASE, MAILLAGE_2=M_PART1, ...);
M_VAR2=ASSE_MAILLAGE(MAILLAGE_1=M_BASE, MAILLAGE_2=M_PART2, ...);

As an alternative some parts of the mesh could be generated manually by a python script as an ASCII .mail file.
However I'm not sure if that would work inside the same .comm file.

M_BASE=LIRE_MAILLAGE(UNITE=20, ...);
mesh_file = open('fort.21', 'w');
mesh_file.write('TITRE\n');
...
mesh_file.write('COOR_3D\n');
...
mesh_file.write('FIN\n');
M_PART1=LIRE_MAILLAGE(UNITE=21, FORMAT='ASTER');
M_VAR1=ASSE_MAILLAGE(MAILLAGE_1=M_BASE, MAILLAGE_2=M_PART1, ...);

I hope this helps.

Best regards,
Lagrange

#17 Re: Code_Aster usage » How to extract the reaction force from DYNA_LINE_HARM » 2013-07-08 11:56:28

Dear Mr. Delmas,

You can find the required files in the attachment.

Best regards,
Lagrange

#18 Code_Aster usage » How to extract the reaction force from DYNA_LINE_HARM » 2013-07-06 16:44:30

lagrange
Replies: 4

Dear all,

If I want to extract the reaction force from the result from the DYNA_LINE_HARM operator, I get the following error message:

RES_HARM = DYNA_LINE_HARM(...);
RES_HARM = CALC_CHAMP(reuse=RES_HARM,
                        FORCE=('REAC_NODA', ),
                        RESULTAT=RES_HARM,
                        CONTRAINTE=('SIEF_NOEU', ),);
   !------------------------------------------------------------------------------!
   ! <EXCEPTION> <CALCULEL2_29>                                                   !
   !                                                                              !
   !  la grandeur associée au champ  RES_HARM.012.000000 : SIEF_C                 !
   !  n'est pas celle associée au paramètre  PCONTMR : SIEF_R  (option: FORC_NODA !
   !------------------------------------------------------------------------------!

Does it mean, that a complex reaction force is not available in Code_Aster?

Best regards,
Lagrange

#19 Re: Code_Aster usage » [SOLVED] How to access stiffness from script python » 2013-07-06 16:31:16

As far as I understood, you want to modify the stiffness matrix directly.

If you want to multiply the complete stiffness matrix by a constant factor, you could use COMB_MATR_ASSE for example:

M=ASSE_MATRICE(...); # assemble the mass matrix
R=ASSE_MATRICE(...); # assemble the original stiffness matrix
R1=COMB_MATR_ASSE(COMB_R=(_F(MATR_ASSE=R, COEF_R=0.5),); # multiply the original stiffness matrix by 0.5
RES1=DYNA_LINE_HARM(MATR_MASS=M, MATR_RIGI=R1, ...); # use the modified stiffness matrix

I hope that answer was helpful for you.

#20 Re: Code_Aster usage » [SOLVED]Extract Large Sparse Matrix and then use them in Python » 2013-03-14 10:55:48

It is interesting that there are operators for matrix/vector operations like PROD_MATR_CHAM() and RESOUD().

PROD_MATR_CHAM() performs the operation y = A x.
But how can I perform an operation like y=x^T A x ?

I need such an operation in order to extract the diagonal of the mass matrix needed for an interface to the multibody software MBDyn (http://www.mbdyn.org).

The alternative would be to use getvecjev(), but that seems to be an undocumented feature.

Best regards,
Lagrange

#21 Re: Code_Aster usage » [SOLVED]For using mass or stiffness matrix in Python (Numpy) » 2013-03-11 12:57:10

Dear Mr. LI,

You could create a macro element and extract the matrices from it:

gen_model= MACR_ELEM_DYNA(BASE_MODALE = bm,
			   MATR_RIGI = matassk,
			   MATR_MASS = matassm );
gen_k = gen_model.EXTR_MATR_GENE( 'RIGI_GENE' );
gen_m = gen_model.EXTR_MATR_GENE( 'MASS_GENE' );

For a working example see http://www.code-aster.org/forum2/viewtopic.php?id=16069.

Best regards,
Lagrange

#22 Code_Aster usage » Inaccurate results: Rigid body modes of a sphere of COQUE_3D elements » 2013-03-06 17:54:14

lagrange
Replies: 1

Dear Code Aster developers,

I have recognized that the coefficient COEF_RIGI_DRZ of the COQUE_3D element can have a significant influence to the value of the rigid body modes.
For the example in the attached file, a value of COEF_RIGI_DRZ=1e-4 gives a result for the first rigid body mode of rotation of f4=11.2Hz.
A value of COEF_RIGI_DRZ=1e-7 gives a result for the first rigid body mode of rotation of f4=3Hz.

Theoretically the results for f1 to f6 should be zero because the part in that example is free and not constraint.
However the value of COEF_RIGI_DRZ can not be reduced further because MODE_ITER_SIMULT will fail in that case because of a singular stiffness matrix.

It seems that the use the COQUE_3D element is inappropriate if the rigid body modes of a very stiff shell like part with a curved surface are important.

Any help is welcome!

Best regards,
Lagrange

#23 Re: Code_Aster usage » [SOLVED] MODE_ITER_SIMULT with QZ fails with complex MATR_A and MATR_C » 2013-02-05 12:32:33

Dear Mr. Archambaud,

I know that it works with Code Aster version 11 by means of the POST_CHAMP operator.
Unfortunately POST_CHAMP does not work for a transient dynamic analysis (see http://www.code-aster.org/forum2/viewto … ?id=18485).
For that reason I have to use Code Aster version 10.

I'm using the keyword REPE_COQUE of CALC_ELEM in order to extract the stress at the surface. See the code below:

RESU_STA=CALC_ELEM(reuse =RESU_STA,
                   MODELE=MODELE,
                   CHAM_MATER=MATERIAU,
                   CARA_ELEM=CARA_ELE,
                   RESULTAT=RESU_STA,
                   OPTION=('SIEF_ELNO','SIGM_ELNO','SIEQ_ELNO',),);

RSTA_SUP=CALC_ELEM(MODELE=MODELE,
                   CHAM_MATER=MATERIAU,
                   CARA_ELEM=CARA_ELE,
                   RESULTAT=RESU_STA,
                   REPE_COQUE=_F(GROUP_MA='plate',
                                 NUME_COUCHE=1,
                                 NIVE_COUCHE='SUP',
                                 VECTEUR=(1,0,0,),),
                   OPTION=('SIEF_ELNO','SIEF_ELGA','SIEQ_ELNO',),);

RSTA_SUP=CALC_NO(reuse =RSTA_SUP,
                 RESULTAT=RSTA_SUP,
                 OPTION=('SIEF_NOEU','SIEQ_NOEU',),
                 MODELE=MODELE,
                 CHAM_MATER=MATERIAU,
                 CARA_ELEM=CARA_ELE,);

RS_SUP_P=PROJ_CHAMP(RESULTAT=RSTA_SUP,
                    MODELE_1=MODELE,
                    MODELE_2=MODELE_P,);

This is where the problem appears.

Best regards,
Lagrange

#24 Re: Code_Aster usage » [SOLVED] MODE_ITER_SIMULT with QZ fails with complex MATR_A and MATR_C » 2013-01-28 14:04:36

Dear Mr. Brie,

Thanks for the hint regarding the document U2.06.04. However the problem of the discontinuities in the stress distribution seems to be a different one.
I get the same discontinuous Von Mises stress (SIEQ_ELNO) for a linear static analysis (RESU_STA) whereas SIEF_NOEU seems to continuous.

Maybe it's a bug in Code_Aster?

Best regards,
Lagrange

#25 Code_Aster usage » [SOLVED] MODE_ITER_SIMULT with QZ fails with complex MATR_A and MATR_C » 2013-01-24 09:03:23

lagrange
Replies: 5

Dear Code Aster developers,

I would like to perform a linear transient analysis with hysteretic damping. For that purpose I run an eigenanalysis and compute modal damping values with the complex stiffness matrix. In order to save time and memory, first I solve the eigenvalue problem (A - lambda*B) * x = 0. Then I project the system matrices to that modal basis and solve (A + lambda * B  + lambda^2 * C) * x = 0.
I had troubles with the generalized eigenvalue problem with complex stiffness matrix and damping matrix.
If the damping matrix is not present at line 130, the eigenanalysis works as expected.

MODE_D=MODE_ITER_SIMULT(MATR_A=Rh_GEN,
                        MATR_B=M_GEN,
                        ## This fails!
                          # MATR_C=M_GEN,
                          # MATR_B=D_GEN,
                        METHODE='QZ',
                        CALC_FREQ=_F(OPTION='CENTRE',
                                     FREQ=min(MODE.LIST_PARA()['FREQ']),
                                     NMAX_FREQ=2*len(MODE.LIST_PARA()['FREQ']),),
                        VERI_MODE=_F(STOP_ERREUR='NON',),);

However I get the same modal damping value for all eigenvalues. This seems to be strange.

After that I run the modal transient analysis with modal damping values extracted from the eigenanalysis.
But if I compute the Von Mises stress at the surface of the shell elements, I get strange results. Despite of a regular mesh, there are major discontinuities in the stress distribution.

Best regards,

Lagrange