3. Calculation process#

This operator makes it easy to create a real dynamic macroelement (without damping) by entering only the mechanical characteristics of the model and the interfaces associated with the substructure.

It carries on the following operations:

  • creation of the stiffness and mass matrices of the substructure,

  • calculation of the normal modes of the substructure,

  • definition of the interfaces associated with the substructure,

  • calculation of static modes or interface modes,

  • definition of the projection base,

  • calculation of the dynamic macro element.

For its implementation, the user can be inspired by the « e » and « f » models from test case SDLD106. These models correspond respectively to the « b » and « d » models of the same test case.

3.1. Operand MODELE#

♦ MODELE = model

model: the model that contains the elements that make up the substructure.

3.2. Operand NUME_DDL#

◊ NUME_DDL = naked

nu: numbering of the degrees of freedom assigned to the substructure.

Note:

This numbering is necessary if we want to calculate the response of the assembled structure due to a loading applied to the substructure for example. Numbering is needed in order to be able to assemble the elementary vector according to the numbering of the degrees of freedom of the substructure.

We then write: NUME_DDL = CO (“nume”) , where*nume* designates the numbering that we want given to the degrees of freedom of the substructure. *

3.3. Operand CHAM_MATER#

♦ CHAM_MATER = chmat

chmat: name of the material field where material characteristics are defined.

3.4. Operand CARA_ELEM#

◊ CARA_ELEM = carele

carele: elementary characteristics of beam elements, shell elements or discrete elements if the substructure contains them.

3.5. Operand CHARGE#

◊ CHARGE = chg

chg: load applied to the substructure.

3.6. Keyword INTERFACE#

The keyword factor INTERFACE defines the interface (s) associated with the substructure. The keywords associated with this factor keyword are identical to the factor keyword INTERFACE in the DEFI_INTERF_DYNA [U4.64.01] operator. The frequency value used to calculate the harmonic constrained modes is also entered here. The value by default for this frequency is equal to 1.

The overload rule is applied. If the frequency value differs between the various interfaces then the user is informed using an alarm which specifies the frequency value actually taken into account.

3.7. Keyword BASE_MODALE#

The keyword factor BASE_MODALE allows you to specify the type of base on which the substructure is projected.

3.7.1. Operand TYPE#

This operand defines the type of the projection base.


♦ TYPE =/'CLASSIQUE'

/”RITZ”

A CLASSIQUE base consists of normal modes and constrained modes or attachment modes depending on the type of the interface. The calculation of the normal modes is done according to the indications provided in the keyword factor CALC_FREQ.

3.7.2. Operand TYPE_MODE#

◊ TYPE_MODE =/'INTERFACE' [DEFAUT]

/”STATIQUE”

The option TYPE = “RITZ” allows you to specify the type of modes to be added to the normal modes. The user can choose STATIQUE modes (static readings of the degrees of freedom of the interface nodes) or INTERFACE (interface modes) modes. For the particular case where we do not want to use normal modes, we choose OPTION = “SANS” in the keyword CALC_FREQ.

3.7.3. Operand NMAX_MODE_INTF#

◊ NMAX_MODE_INTF =/10 [DEFAUT]

/nmintf

NMAX_MODE_INTF corresponds to the number of interface modes to take into account. Here we consider the first nmintf interface modes (nmintf > 0).

3.8. Keyword CALC_FREQ#

This keyword factor makes it possible to choose the frequency content of normal modes. The operands associated with this factor keyword are the same as those defined for CALC_MODES [U4.52.02]. A particularity for option BANDE, the FREQ operand allows you to enter a frequency list and you perform modal calculations on the various intervals in the list.

We choose OPTION = “SANS” if we don’t want to step up normal modes.

The STOP_ERREUR keyword is used to indicate to the operator whether to stop (“OUI”) or continue (“NON”) if one of the criteria for controlling the quality of the calculated modes is not verified. This keyword is equivalent to the STOP_ERREUR keyword in the VERI_MODE factor keyword in CALC_MODES.

Note:

In order not to overload the order, this keyword factor does not allow you to enter the parameters COEF_DIM_ESPACE , NMAX_ITER_SHIFT , PREC_SHIFT , SEUIL_FREQ and STOP FREQ_VIDE . On the other hand, the user can enter the dimension of the subspace ( DIM_SOUS_ESPACE ) if necessary. The values chosen for calculating normal modes are the default values for these parameters in CALC_MODES .

3.9. Keyword SOLVEUR#

Optional keyword, see [U4.50.01].

3.10. Operand INFO#

This operand makes it possible to print more or less information on the macroelement created in the file “MESSAGE”.