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## #1 2017-07-26 10:18:43

edhage
Member
Registered: 2016-08-23
Posts: 13

### Mass normalizing eigenvectors does NOT work with hysteretic damping

When I assign material with hysteresis like so:

mat=DEFI_MATERIAU(ELAS=_F(E=210000000000.0,
NU=0.3,
RHO=7850.0,
AMOR_HYST=0.03,),); <-- hysteresis part

I can determine the eigenmodes okay with:

ASSEMBLAGE(MODELE=model,
CHAM_MATER=matfield,
CARA_ELEM=carac,
CHARGE=XY_plane,
NUME_DDL=CO('NUM'),
MATR_ASSE=(_F(MATRICE=CO('Stiffn'),
OPTION='RIGI_MECA',),
_F(MATRICE=CO('StiffHys'),
OPTION='RIGI_MECA_HYST',), <-- need this to be able to determine stiffness matrix complex part
_F(MATRICE=CO('Mass'),
OPTION='MASS_MECA',),),);

ceig=CALC_MODES(OPTION='CENTRE',
MATR_RIGI=StiffHys, <-- use the hysteresis matrix
MATR_MASS=Mass,
CALC_FREQ=_F(FREQ=0.1111,
NMAX_FREQ=6,),);

But normalizing like this does not work (and it should work for complex modes, right?):

# normalization of eig modes
ceig=NORM_MODE(reuse =ceig,
MODE=ceig,
NORME='MASS_GENE',
);

Is this a bug ?
How can I determine the mass-normalized eigenvectors ?

Error:
# ------------------------------------------------------------------------------------------
# Commande No :  0019            Concept de type : mode_meca_c
# ------------------------------------------------------------------------------------------
ceig = NORM_MODE(reuse=ceig,
NORME='MASS_GENE',
MODE=ceig,
INFO=1,)

Normalisation des modes : ceig

NUME_ORDRE             ancienne norme              nouvelle norme
1                  SANS_CMP: LAGR                   MASS_GENE
2                  SANS_CMP: LAGR                   MASS_GENE
3                  SANS_CMP: LAGR                   MASS_GENE
4                  SANS_CMP: LAGR                   MASS_GENE
5                  SANS_CMP: LAGR                   MASS_GENE
6                  SANS_CMP: LAGR                   MASS_GENE

!-----------------------------------------------------------------------------------!
! <EXCEPTION> <JEVEUX_26>                                                           !
!                                                                                   !
!      Objet JEVEUX inexistant dans les bases ouvertes : >??????ø???????????.REFA< !
!      l'objet n'a pas été créé ou il a été détruit                                 !
!-----------------------------------------------------------------------------------!

Destruction du concept 'ceig'.

Last edited by edhage (2017-07-26 10:21:34)

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## #2 2017-08-10 09:32:10

edhage
Member
Registered: 2016-08-23
Posts: 13

### Re: Mass normalizing eigenvectors does NOT work with hysteretic damping

Maybe people are interested in the answer (although no responses on my question):

In r5.01.03 par. 2.4 is described that  mass normalised eigenvector = current eigenvector /sqrt(generalized_mass)

thus the normalized eigenvector can be determined with MAS_GENE which is determined in CALC_MODES.

normalized eigenvector = current eigenvector / sqrt(MASS_GENE)

Simple solution, do not need to normalize the mass and stiffness-matrixes.

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