Introduction ============ The choice of modeling is made through the operator AFFE_MODELE of*Code_Aster*. For example, the user will write in their command file: .. code-block:: text MOME = AFFE_MODELE (MAILLAGE = MAIL, AFFE =_F (TOUT = 'OUI', MODELISATION = 'AXIS_JOINT_HMS', PHENOMENE = 'MECANIQUE')) In order to be able to offer the user other models, we will describe in this document a methodology for introducing new modeling in*Code_Aster*. Introducing modeling in*Code_Aster* requires asking the following questions: * In which phenomenon will I add my modeling? * What are the geometric and topological dimensions of finite elements? * What are the meshes concerned by this modeling? * What are the "main" elements and the edge elements? * What are the attributes that can be defined? * What calculations can be made with this modeling? We will answer these questions in this document. Other questions relating to finite elements are dealt with in other documents: * [:ref:`D5.02.01 `] How do I introduce a new quantity or new components (CMP) into an existing quantity? * [:ref:`D5.02.02 `] How do I introduce a new mesh type (mesh_type) or a new reference element (ELREFE)? * [:external:ref:`D5.02.05 `] How do I introduce a new elementary calculation?