4. Study tools#

4.1. Complements and operations on the mesh#

The notion of mesh used by code_aster is reduced to a very simple one: list of nodes and their coordinates, list of meshes and their topology (connectivities). To these entities is added the concept of groups of nodes and groups of elements. These groups make it possible to assign various modeling characteristics (finite elements, materials, boundary conditions, loads, etc.) and to conduct the analysis of the results (selective extraction of components).

The user can create groups of nodes or meshes at any time during the calculation, using logical or geometric criteria. You can also modify the data structure containing the mesh: change of coordinate system, addition of additional nodes on cells, creation of new cells or groups of cells, destruction of cells, etc. The addition and removal of material can therefore be simply modelled.

The construction of a complex mesh can only be done through the use of a tool more adapted to this use such as Salome and its integrated donors (Netgen, BLSurf, Hexotic, etc.) or GMSH.

4.2. Material data catalog#

A material data catalog under QA provides access to values of behavioral laws parameters for various materials commonly used in studies. Material characteristics can be directly included in the order file thanks to a specific operator. For the free version, all the equipment in the catalog is available but the database is empty.

4.3. Treatment and exploitation of results#

4.3.1. Field operations#

Calculated fields can be used in all sorts of algebraic combinations. In linear analysis, for example, we can deduce the response to a complex load from the responses to the unit loads on which they break down.

4.3.2. Statement of values#

Operations to extract result fields are available on nodes or meshes. It is also possible to define any observation path independent of the initial mesh. Various calculations are proposed on the extracted fields (mean, standard deviation, tensor invariants, transition to local axes, etc.). For temporal or frequency evolutions, it is possible to extract the deformation at a moment (a frequency) or the response of a particular quantity.

4.3.3. Printing the results#

The results can be printed in an easily searchable form or in the format of the visualization tools (MED, I- DEAS, GMSH). code_aster communicates with Salomé using the format MED.

You can also draw curves in various formats (postscript or other image formats) using the xmgrace plotter.

4.4. Quality control of results#

Numerous functionalities make it possible to control the quality of the results of a study or to facilitate its implementation.

4.4.1. Error estimators and adaptive meshing#

Two error estimator categories are available. Coupled with the refinement/de-refinement software HOMARD (internal chaining to code_aster via macro-commands), they make it possible to adapt the mesh during calculation in order to achieve a given precision, for an optimal calculation cost.

4.4.3. Use of incompatible meshes#

Projection operators make it possible to continue a calculation performed on a first mesh on a second mesh. It is thus possible to use meshes that are different in thermal and mechanical terms (by including for example a crack block in the structure only at the time of its analysis in operation, after having calculated on a simpler mesh the residual stresses due to its method of manufacture).

4.4.4. Automatic redistribution of the time step and control of the load#

In the event of non-convergence of the global resolution algorithm, the user can ask that the code itself initiate a redistribution of the time steps in order to allow convergence. An event-based management mechanism is also available.

Moreover, in order to facilitate the convergence of calculations, it is also possible to control the gradual application of loading by the value of a degree of freedom or a deformation (continuation methods).

4.4.5. Radiality discharge and loss indicators#

These indicators make it possible to verify the validity of the hypotheses formulated on the non-linear behavior of a structure, and the relevance of the mode of application of the load selected (no load).