1. Presentation#

When you add a component to one of the quantities DEPL_R, TEMP_R, or PRES_C, you often have to impose kinematic boundary conditions on this new degree of freedom. For example, we want to be able to block it.

Users who want to constrain this degree of freedom can do so, for example, using the following commands and keywords:

Order

Factor key

AFFE_CHAR_MECA (_F)

DDL_IMPOFACE_IMPO

AFFE_CHAR_MECA_C

DDL_IMPO

AFFE_CHAR_THER (_F)

TEMP_IMPO

AFFE_CHAR_ACOU

PRES_IMPO

AFFE_CHAR_CINE

MECA_IMPO

AFFE_CHAR_CINE

THER_IMPO

For the program to be able to constrain this new degree of freedom, it is necessary to modify/add three types of catalogs. There is no Fortran to change.

  • The first step is to register this new degree of freedom in the catalog of quantities of this new degree of freedom in the mechanical DEPL_Ren quantity, in the thermal TEMP_Ren quantity, or in the acoustic PRES_Cen quantity.

  • The second step is to update the order catalogs AFFE_CHAR_XXX

  • The third step is to create the new Lagrange element associated with its new degree of freedom. The only difference between these different elements is the name of the degree of freedom (it’s almost a copy).

Note:

Step number 3 is necessary in order to be able to dualize the boundary conditions involving the new degree of freedom. It would be useless if you only wanted to use the AFFE_CHAR_CINE command (elimination)

As far as Lagrange elements are concerned, the finite element that makes it possible to introduce conditions on a degree of freedom must have the name:

D_ DEPL_R_nom_ddl

in mechanics

D_ TEMP_R_nom_ddl

in thermal

D_ PRES_C_nom_ddl

in acoustics

The name of a degree of freedom is therefore limited to 7 characters so that the name of the element is limited to 16 characters.

Once these 3 operations have been performed, the new degree of freedom can be used for boundary conditions.