4. Operands#

4.1. General information on operands#

The operands under the key factors MECA_IMPO, THER_IMPO, and ACOU_IMPO have two forms:

operands specifying the geometric entities on which the loads are assigned (keywords GROUP_MA, GROUP_NO…). The arguments of these operands are the same for both operators.
operands specifying the values affected (DX, DY, DZ, etc…). The meaning of these operands is the same for both operators. The arguments to these operands are all of the real type for the AFFE_CHAR_CINE operator and of the function (or formula) type for the AFFE_CHAR_CINE_F operator.

This is true with one exception: the factor keyword ACOU_IMPO (which does not exist in the AFFE_CHAR_CINE_F command) is always of a complex type.

We will therefore not distinguish in this document, unless otherwise expressly stated, between the two operators AFFE_CHAR_CINE and AFFE_CHAR_CINE_F.

In general, the entities on which values should be assigned are defined by nodes:

or by the operand TOUT = “OUI” which allows you to designate all the nodes of the mesh,
or by the GROUP_NOpermettant operand to designate a list of node groups,
or by the operand GROUP_MApermettant to designate all the knots carried by the meshes designated by the lists in GROUP_MA.

4.2. Behaviour in case of overload:#

4.2.1. Overload within a single command AFFE_CHAR_CINE#

When using several occurrences of MECA_IMPO (or THER_IMPO,…) within the same command and when certain nodes are affected several times, the last occurrence takes precedence. For example:

chine= AFFE_CHAR_CINE (MECA_IMPO =(

_F (TOUT =” OUI “, DX= 1.,…)

_F (GROUP_NO =” GN3 “, DX= 3.,…)

In this case, the imposed displacement DXpour the node GN3vaut: 3.

4.2.2. Overload between multiple commands AFFE_CHAR_CINE#

If you use several different commands, the behavior is different. For example:

chcin1= AFFE_CHAR_CINE (MECA_IMPO = _F (TOUT =” OUI “, DX= 1.,…)

chcin2= AFFE_CHAR_CINE (MECA_IMPO = _F (GROUP_NO =” GN3 “, DX= 3.,…)

In this case, the imposed displacement DXpour the node GN3vaut: 4 (because 1+3)

4.2.3. Overload between AFFE_CHAR_CINE and AFFE_CHAR_MECA#

If we « mix » the AFFE_CHAR_MECA and AFFE_CHAR_CINE commands, the code will stop in a fatal error (FACTOR_41) by explaining that there is an over-abundant blocking relationship (NOEUDN3/DX).

4.3. Operand MODELE#

♦ MODELE = mo

Concept produced by the operator AFFE_MODELE [U4.41.01] where the types of finite elements affected on the mesh are defined.

4.4. Keyword MECA_IMPO#

4.4.1. But#

A factor keyword that can be used to impose, on nodes, a displacement value, defined component by component in the global coordinate system.

These boundary conditions will subsequently be treated by the method known as the elimination of imposed degrees of freedom (i.e. without dualization, unlike the treatment of the same type of limit condition by the use of operators AFFE_CHAR_MECA or AFFE_CHAR_MECA_F [U4.44.01]).

4.4.2. Syntax#

AFFE_CHAR_CINE

AFFE_CHAR_CINE_F

),),

function (*): function or formula

List of keywords available under MECA_IMPO in AFFE_CHAR_CINE:

List of keywords available under MECA_IMPO in AFFE_CHAR_CINE_F:

These are the names of the degrees of freedom carried by the finite elements of the model. The meaning of these names can be found in the documentation for AFFE_CHAR_MECA [U4.44.01].

4.4.3. Operands#

/MECA_IMPO

DX = ux or uxf DY = uy or uyf DZ = uz or uzf

Value of the displacement component in translation imposed on the specified nodes

Only for the nodes of a 3D model including beam, plate, shell, discrete elements:

DRX = drx or drxf DRY = dry out DRZ = drz oudrzf

Value of the displacement component in rotation imposed on the specified nodes

For more « exotic » degrees of freedom: GRX, TEMP,, PRESet PHI, refer to the documentation for the command AFFE_CHAR_MECA [U4.44.01 §3.9].

Attention:

We check that the specified degree of freedom exists in this node for at least one of the elements of the model (keyword MODELE) that rely on this node.

In addition, the overload rule is applied when the same degree of freedom of the same node is imposed several times: only the last value is retained.

4.5. Keyword THER_IMPO#

4.5.1. But#

Keyword factor that can be used to impose a nodal temperature value on nodes.

These boundary conditions will be treated, subsequently, by the method known as the elimination of imposed degrees of freedom (i.e.: without dualization unlike the treatment of the same type of limit condition by the use of operators AFFE_CHAR_THER or AFFE_CHAR_THER_F [U4.44.02])

4.5.2. Syntax#

For AFFE_CHAR_CINE

For AFFE_CHAR_CINE_F

function (*): function or formula

4.5.3. Operands#

Temperature imposed on the knots (or on the middle sheet for thermal shells)

Temperature imposed on the underside for thermal shell elements.

Temperature imposed on the upper side for thermal shell elements.

For shells, the lower and upper faces are defined, mesh by mesh, by the direction of the external normal deduced from the numbering of the nodes: see FACE_IMPO of AFFE_CHAR_MECA [U4.44.01].

4.6. Keyword ACOU_IMPO#

4.6.1. But#

Keyword factor that can be used to impose a sound pressure value on nodes.

4.6.2. Syntax#

For AFFE_CHAR_CINE

/ACOU_IMPO = (_F (♦//TOUT = “OUI”, | GROUP_NO = lgno, [l_gr_node] | GROUP_MA = lgma, [l_gr_mesh] ♦ PRES = p, [C] ),),

For AFFE_CHAR_CINE_F:

No ACOU_IMPO keyword because there is no complex function yet.

4.6.3. Operands#

PRES

Value of the complex sound pressure imposed on the specified node (s).

4.7. Keyword EVOL_IMPO#

/EVOL_IMPO = evoimp/[evol_ther]

/[evol_elas] /[evol_noli] ◊ NOM_CMP = lcmp [l_ TXM]

This keyword allows « structural zoom » (see for example the zzzz230a test).

The effect of this keyword is to impose all the ddls of evoimpevolution as if they were functions of time. This possibility is offered for the evol_elas, evol_noli, and evol_ther data structures.

To do a « structural zoom », you must only impose the ddls on the nodes at the edge of the « zoom » model. This means that it is generally necessary to project the « rough » calculation onto the mesh at the edge of the « zoom » model.

If, in addition, you do not want to impose all the components, you must use the keyword NOM_CMP to choose the components to impose (by default: all).

Notes:

Be careful not to use multiple EVOL_IMPO on common areas (otherwise there will be accumulation of imposed values)
Attention to the use of FONC_MULT with EVOL_IMPO : the result may not be what you expect!
The EVOL_IMPO will be used for any time value between \(\mathit{tmin}\) and \(\mathit{tmax}\) (extreme values of the transient instants EVOL_IMPO ). Outside this interval, a fatal error is emitted (extrapolation forbidden) .
If the EVOl_IMPO only has a moment, we allow the « constant » extension and we issue an alarm.