1 Copyright © 2009 by ASME Proceedings of the ASME 2009 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference IDETC/CIE 2009 August 30 – September 2, 2009, San Diego, CA, USA TOWARDS CAD-LESS FINITE ELEMENT ANALYSIS USING GROUP BOUNDARIES FOR ENRICHED MESHES MANIPULATION R. Lou , * , , F. Giannini*, J-P. Pernot , A. Mikchevitch , B. Falcidieno*, P. Véron , R. Marc LSIS – UMR CNRS 6168 2 cours des Arts et Métiers 13617 Aix-en-Provence, France {ruding.lou, jean-philippe.pernot, phi- lippe.veron}@ensam.fr *IMATI – CNR 6, via de Marini 16149 Genova, Italy {falcidieno,giannini}@ge.imati.cnr.it Electricité de France Group Research and Development Direction 1, avenue Général de Gaulle 92141 Clamart cedex, France {alexei.mikchevitch, ra- phael.marc}@edf.fr ABSTRACT Nowadays, most of the numerical simulations are carried out by successively performing the following steps: CAD model definition or modification, conversion to a mesh model and enrichment with semantic data relative to the simulation (e.g. material behaviour laws, boundary conditions), Finite Element simulation and analysis of the results. Classically, the seman- tic data are attached to the mesh through the use of groups of geometric entities sharing the same characteristics. Thus, any modification of the CAD model always implies an update of the mesh as well as an update of the attached semantic data. This is time-consuming and not adapted to the context of in- dustrial maintenance. Moreover, the CAD models do not al- ways exist and should therefore be reconstructed starting from scratch or from the physical object. In this paper, we set up a framework towards the definition of CAD-less Finite Element analyses wherein enriched meshes are manipulated directly. The geometric manipulations are constrained with information extracted from the group definition. Actually, the boundaries of those groups are exploited to constrain the modifications. The concept of Virtual Group Boundaries is introduced to focus on the extension of the attached semantic information instead of the actual tessellation while generalising the ap- proach to groups of any dimension going from 0D (vertex) to 3D (e.g. tetrahedron). The notion of Elementary Group is also introduced as a mean to ease the forthcoming transfer of the semantics from the initial to the modified models. Such a framework also finds interest in the preliminary design phases where alternative solutions have to be evaluated. 1. INTRODUCTION Today, the mainstream methodology for product behaviour numerical simulations relies on the following steps: concep- tual phase, Computer-Aided Design (CAD) modeling, mesh- ing and model preparation for specific behavior study, Finite Element (FE) simulation, result analysis and optimization loops [1,2]. Such a process is illustrated in figure 1 wherein dot lines show the general workflow when performing succes- sive optimizations. For each modification, a come back to CAD modeling is required that implies an updating of the mesh as well as some adjustments in all the forthcoming steps. This is time-consuming. Actually, in such a process, most of the time is spent for the development of complex meshes adapted to specific FE simulations, for the accurate identifica- tion of the unknown parameters and for the prototyping and assessment of the proposed solution. Thus, it would be impor- tant to preserve as much as possible all the manipulations and data that have been previously set up. This is especially true when the simulation models have been tuned to fit the ground truth that can be measured on the real object. Figure 1: Classical design process (dot lines) vs. CAD-less design process adapted to the fast industrial maintenance analysis and preliminary design phases (continuous lines) [3]. DETC2009-86575