a b s t r a c tIn this paper, we present some novel results and ideas for robust and accurate implicit representation of geometric surfaces in finite element analysis. The novel contributions of this paper are threefold: (1) describe and validate a method to represent arbitrary parametric surfaces implicitly; (2) represent arbitrary solids implicitly, including sharp features using level sets and boolean operations; (3) impose arbitrary Dirichlet and Neumann boundary conditions on the resulting implicitly defined boundaries. The methods proposed do not require local refinement of the finite element mesh in regions of high curvature, ensure the independence of the domain's volume on the mesh, do not rely on boundary regularization, and are well suited to methods based on fixed grids such as the extended finite element method (XFEM). Numerical examples are presented to demonstrate the robustness and effectiveness of the proposed approach and show that it is possible to achieve optimal convergence rates using a fully implicit representation of object boundaries. This approach is one step in the desired direction of tying numerical simulations to computer aided design (CAD), similarly to the isogeometric analysis paradigm.

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Résumé :Nous présentons une approche prometteuse afin de réduire les difficultés liées aux maillages de géométries avec frontières courbes pour l'analyse avec deséléments finis d'ordre supérieur. Une analyse par XFEM d'ordre supérieur dans le cas de la modélisation des interfaces matériau-vide est testée sur un ensemble représentatif de problèmes d'élasticité linéaire. Les frontières implicites courbes sont approximéesà l'intérieur d'un maillage grossier non structuré en utilisant les informations paramétriques extraites de la représentation paramétrique (la plus populaire en conception CAO). Cette approximation génère un sous-maillage gradué (SMG)à l'intérieur deséléments traversés par la frontière qui sera utiliséà des fins d'intégrations numérique. Exemples de géométries et des expériences numériques illustrent la précision et la robustesse de l'approche proposée. Abstract :We present a promising approach to reduce the difficulties associated with meshing complex curved domain boundaries for higher-order finite elements. In this work, higher-order XFEM analyses for strong discontinuity in the case of linear elasticity problems are presented. Curved implicit boundaries are approximated inside an unstructured coarse mesh by using parametric information extracted from the parametric representation (the most common in Computer Aided Design CAD). This approximation provides local graded sub-mesh (GSM) inside boundary elements (i.e. an element split by the curved boundary) which will be used for integration purpose. Sample geometries and numerical experiments illustrate the accuracy and robustness of the proposed approach.