3. Operands#

3.1. Operands MODELE/CARA_ELEM#

♦ MODELE = model,

◊ CARA_ELEM = caraelem,

These keywords are used to provide information on:

  • the name of the model (model) whose elements are the subject of mechanical calculation.

  • the name of the characteristics of the structural elements (plates, beams, discretes,…) if they are used in the model.

3.2. Keyword factor MATER_ELAS#

◊ MATER_ELAS = _F (

♦/MATER = matt /♦ E = e ♦ AMOR_HYST = amorhyst ♦ RHO = rho ♦ NU = naked ♦ GROUP_MA = GMA )

This keyword makes it possible to assign an elastic material without frequency dependency to elements belonging to GROUP_MA.

The material can be defined before the macro-order using the operator DEFI_MATERIAU [U4.43.01]; in this case, this material is recalled with the keyword MATER. The material can also be defined here by its properties: Young’s modulus E, density RHO, Poisson’s ratio NU, and hysteretic damping AMOR_HYST.

This keyword factor can be repeated as many times as there are elastic materials with no frequency dependence in the structure.

3.3. Keyword factor MATER_ELAS_FO#

♦ MATER_ELAS_FO = _F (

♦ E = l_e ♦ AMOR_HYST = l_love ♦ RHO = rho ♦ NU = naked ♦ GROUP_MA = GMA )

This keyword makes it possible to assign a viscoelastic material with frequency dependence to elements belonging to GROUP_MA.

The mechanical properties of viscoelastic material are of two types:

  • those that depend on frequency: Young’s modulus E and damping factor AMOR_HYST; they are provided by functions indexed by frequency, produced by DEFI_FONCTION/NOM_PARA =” FREQ “[U4.31.02]);

  • those that are constant: density RHO and Poisson’s ratio NU.

This keyword factor can be repeated as many times as there are visocelastic materials with frequency dependence in the structure.

3.4. Keyword TYPE_RESU#

◊ TYPE_RESU =/'HARM' [DEFAUT]

/”MODE”

This keyword is used to define the type of calculation to be performed:

  • the choice “MODE” makes it possible to calculate the natural modes of the structure;

  • the calculation “HARM”, makes it possible to obtain the frequency response of the structure to a given excitation; it is also possible to recover the natural modes calculated using the keyword MODE_MECA.

3.5. Keywords FREQ/LIST_FREQ#

♦/FREQ = l_f

/LIST_FREQ = lfreq

In the case of a modal calculation of the structure (TYPE_RESU =” MODE “), this keyword makes it possible to define the frequency band for searching for the modes. The list must then contain exactly 2 values (strictly increasing).

In the case of a harmonic calculation of the structure (TYPE_RESU =” HARM “), this keyword makes it possible to define the discrete frequencies for which the structure response is calculated. The list must then contain at least 2 strictly increasing values.

3.6. Keywords TYPE_MODE/RESI_RELA#

◊ TYPE_MODE =/'REEL' [DEFAUT]

/”BETA” /”COMPLEXE”

Several choices for calculating natural modes are possible: real modes, beta-modes (which are improved real modes giving better precision of the results, cf. [R5.05.09]), as well as complex modes.

The calculation of complex modes makes it possible to obtain modal depreciations. However, this type of mode cannot be used to carry out a harmonic calculation (TYPE_RESU =” HARM “).

Note:

If you calculate complex modes, you can get the modal depreciations in a Python list with this function: liste_python=modes. LIST_PARA () [“AMOR_REDUIT”] (this requires using PAR_LOT =” NON “in the DEBUT command).

◊ RESI_RELA =/1.E-3 [DEFAUT]

/eps

The calculation of natural modes with the iterative method has a convergence criterion called RESI_RELA. An eigenmode is retained in the modal base when the relative difference between the natural frequencies calculated between two successive iterations is less than RESI_RELA.

3.7. Keyword factor EXCIT#

♦ EXCIT =_F (

♦ CHARGE = load )

This keyword allows the assignment of loads (boundary conditions, excitation forces,…) that were previously defined by the operator AFFE_CHAR_MECA [U4.44.01].

Note:

Currently, for external excitations, only excitations of type FORCE_NODALE are compatible with the command DYNA_VISCO .

For harmonic calculation, the natural mode base is enriched, in a manner that is transparent to the user, by the static modes associated with the excited nodes.

3.8. Keyword NOM_CHAM (if TYPE_RESU =” HARM “)#

◊ NOM_CHAM =/'DEPL' [DEFAUT]

/”VITE” /”ACCE”

This keyword allows you to define which fields will be saved in the result concept (movement, speed or acceleration). It is possible to save several fields by giving a list, for example NOM_CHAM =( “DEPL”, “ACCE”).

3.9. Keyword MODE_MECA (if TYPE_RESU =” HARM “)#

◊ MODE_MECA = CO (“modes”)

If this keyword is present, two concepts will be produced by the macro command:

  • the modes_meca concept

  • the visco concept like dyna_harmo

For example, the concept modes can be printed classically with the IMPR_RESU [U4.91.01] command.

3.10. Keyword COEF_FREQ_MAX (if TYPE_RESU =” HARM “)#

◊ COEF_FREQ_MAX = cfmax [R]

During a harmonic calculation, the multiplier coefficient COEF_FREQ_MAX makes it possible to obtain more accurate frequency response values, by multiplying by COEF_FREQ_MAX the value of the maximum calculation frequency of the modal projection base.

The minimum value for this parameter is 1.5.

3.11. Keyword INFO#

◊ INFO =/1 [DEFAUT]
/2

Indicates the print level in file MESSAGE.