4. Integrating the element into Code_Aster

4.1. Description and use

This element is based on 3D volume meshes HEXA8.

4.1.1. Modeling

The 3D_SI modeling is assigned to the designated HEXA8 cells. The usual face elements in 3D modeling are affected on mesh QUAD4.

4.1.2. Material

All the material coefficients relating to the laws of behavior valid in small deformations for 3D models can be used.

4.1.3. Boundary conditions and loading

All loads and boundary conditions available on 3D elements and face elements are available.

4.1.4. Post-processing options

All post-processing options that are usually available for 3D models can be used.

4.1.5. Linear buckling calculation

Since option RIGI_MECA_GE is activated in the element catalog, it is possible to perform a classical buckling calculation after assembling the elastic and geometric stiffness matrices.

4.1.6. Nonlinear calculations

All the behaviors available for the usual 3D modeling can be used, in small deformations. When it comes to large deformations, the only usable option is approximation PETIT_REAC.

Numerical integration is achieved with a Gauss point, just like in hardware nonlinear.

4.2. Implantation

The options are activated in the meca_hexs8.cata catalog.

4.3. Validation

The tests validating this element are, in version 9 of*Code_Aster*:

• SSNV196: 3D beam in flexure in elasticity and in plasticity

• HSNV125G, PERFE01A, SDNV103, SSND105 use a single element to validate non-linear behaviors, thus allowing savings in calculation time (1 single Gauss point)