In the design workflow, CAD models of complex components include more and more details. A transformation of such models into Finite Element (F.E.) models often generates a much too large number of elements to be used directly. Generally, the removal of shape details or idealization operations are required to prepare F.E. models. These modifications must preserve the analysis result and the user must control the process in order to ensure sufficient accuracy of the F.E. results. In accordance to the analysis problems, the simplification process generates different appropriate F.E. models. In this paper, we present different operators and criteria to prepare analysis models from CAD models.