ADAPTATION DE MODÈLES CAO PARAMÉTRÉS EN VUE D’UNE ANALYSE DE COMPORTEMENT MÉCANIQUE PAR ÉLÉMENTS FINIS

Language: French
Year: 2008
Author: Foucault, Gilles
Supervisor: Maranzana, R., Léon, J., & Cuillière, J.
Institution: UNIVERSITÉ DU QUÉBEC
Page(s): 260

Abstract

Expressing hypotheses and simplifying an analysis domain are mandatory for current simulations in the context of finite element analyses (FEA). The adaptation of design models is achieved by the elimination of shape details and topological details in order to generate a finite elmement (FE) mesh where elements’ size is well suited to part’s mechanical behaviour and simulation accuracy goal (size map). Currently, the adaptation of large Computer Aided Design (CAD) models for FEA is a long and difficult task because of the lack of automatic tools to eliminate details and generate an adapted FE mesh. Our work contributes to the automatic generation of FEA models from CAD design models with the following points : – shape simplification of CAD models,
– topology adaptation of BREP models,
– trans-patch mesh generation over composite geometry. We propose criteria to identify form features relying on CAD design features and FE mesh ge- neration requirements (FE size map, boundary conditions). These criteria identify CAD trans- formations that are required to simplify the FEA model. The second main contribution proposes the Meshing Constraints Topology (MCT) aiming at transforming a CAD model into a FEA model featuring only faces, edges, and vertices that are relevant for meshing. Therefore, MCT models represent explicitly the topology of me- shing constraint entities. MCT operators provide high-level topological transformations (such as edge deletion), and cluster CAD faces and edges to form composite geometry. The adapta- tion process features identification criteria that determine automatically MCT operators requi- red to adapt the CAD BREP topology to meshing requirements : FE size map, sharp edges, and boundary condition zones. The last part of our contribution extends the advancing front triangulation over a single pa- rametric surface (Cuillière, 1998) to surfaces composed with multiple parametric surfaces : the triangulation is propagated over multiple parametric domains, and front collisions are pro- cessed in the parametric space of surfaces. This method uses the exact BREP geometry, and presents the advantage to be applicable to closed composite surfaces, i.e. spheres and n-torus.

Keywords: CAD, FEA, mesh generation, composite geometry, meshing constraints topology, defeaturing.

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