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This paper is devoted to numerically study the sheet metal blanking process using elastic-visco-plastic model fully coupled with ductile damage and 3D adaptive remeshing procedure. The proposed constitutive theory aims to capture the effects of irreversible damage associated with the failure mechanisms that occur in sheet metal forming under large deformation. The isotropic ductile damage fully coupled into an elasto-viscoplastic flow stress model and stress state parameters (stress triaxiality and Lode angle) are proposed to control the damage evolution under multi-axial loading path. When a sheet metal is sheared by large elastic-viscoplastic strains, the propagation of macroscopic cracks induces severe changes of topology and frequent remeshing must be performed in order to avoid large mesh distortion and element quality. An h-adaptive Constraint Delaunay kernel remeshing scheme (refinement and coarsening) dedicated to the simulation of macroscopic ductile cracks initiation and propagation during blanking processes is proposed. Cracks are represented using a procedure based on fully damaged elements deletion. Optimal adaptive element size is driven by error indicators based on both geometrical considerations (tool geometry, deformed part) and the derivatives of physical field (plastic strain or damage localization). The proposed methodology was successfully verified comparing the predicted evolution of material ductility with the experimental data relative to several metals. The procedure for the blanking simulation is also discussed in details.

A simulation strategy combining an octree-AMR and an HRL turbulence model with overset grids is investigated in FLUSEPA™, the Finite-Volume solver developed by ArianeGroup. The turbulence model used is a \(k- \varepsilon \) with a Delayed Detached Eddy Simulation [14] treatment for the destruction term of k. First, we study the influence of the refinement criteria on the pressure fluctuations in the recirculation area of a cylindrical backward facing step. Using an initially coarse grid, we compare the results with those from a fixed fine grid calculation. Then, the methodology is applied to the numerical simulation of the buffeting of an Ariane 5 model.

International audience; This paper introduces the notion of a metric for a simplex. Such a metric is a key ingredient when solving a PDE system by means of a Finite Element Method. Both mesh generation methods and error estimates (as far as interpolation error is considered) are concerned. Moreover, this metric gives information about the geometry of the corresponding element, typically about its shape quality in any Euclidean space.; Ce papier introduit la notion de métrique liée à un élément géométrique simplicial (un simplexe). Cette métrique est utilisée dans la résolution par la méthode des éléments finis d'équations aux dérivées partielles, à la fois pour la génération de maillages et les estimateurs d'erreur basés sur l'erreur d'interpolation. En outre, cette métrique renseigne sur la géométrie de l'élément et, en particulier, sur sa qualité en forme dans un espace euclidien quelconque.

International audience; In CAD (computer aided design) environments, a surface is commonly modeled as a collection of connected regions represented by parametric mappings.For meshing such a composite surface, a parallelized indirect approach with dynamic load balancing can be used on a shared memory system.However, this methodology can be inefficient in practice because most existing CAD systems use memory caches that are only appropriate to a sequential process.Two solutions are proposed, referred to as the Pirate approach and the Discrete approach. In the first approach, the Pirate library can be efficiently called in parallel since no caching is used for the storage or evaluation of geometric primitives.In the second approach, the CAD environment is replaced by internal procedures interpolating a discrete geometric support.In both cases, performance measurements are presented and show an almost linear scaling.

International audience; Multi-point forming MPF is an innovative technology of manufacturing complex thick sheet metal products without the need for solid tools. The central component of this system is a pair of the desired discrete matrices of punches, and die surface constructed by changing the positions of the tools though CAD and a control system. Because reconfigurable discrete tools are used, part-manufacturing costs are reduced and manufacturing time is shorten substantially. Firstly, in this work we develop constitutive equations which couples isotropic ductile damage into various flow stress based on the Continuum Damage Mechanic theory. The modified Johnson-Cook flow model fully coupled with an isotropic ductile damage is established using the quasi-unilateral damage evolution for considering both the open and the close of micro-cracks. During the forming processes severe mesh distortion of elements occur after a few incremental forming steps. Secondly, we introduce 3D adaptive remeshing procedure based on linear tetrahedral element and geometrical/physical errors estimation to optimize the element quality, to refine the mesh size in the whole model and to adapt the deformed mesh to the tools geometry. Simulation of the MPF process (see Fig. 1) and the unloading spring-back are carried out using adaptive remeshing scheme using the commercial finite element package ABAQUS and OPTIFORM mesher. Subsequently, influencing factors of MPF spring-back are researched to investigate the MPF spring-back tendency with the proposed remeshing procedure.

In this paper, a new reverse engineering method is proposed for 3d surface reconstruction without contact. This method is based on the combination of stereovision and structure light methods. The originality of the proposed technique is that the pattern is a two-dimensional Delaunay triangulation. A key characterizing the vertices is computed for each vertex. The pattern matching between two images is reduced to the comparison of two meshes. The three dimensional triangulation of the surface can then be obtained by using the geometric properties of the acquisition devices.

International audience; The present paper aims to couple an unstructured Finite Volume formulation using a multi-level grid overlapping methodology based on geometric intersection algorithms with an adaptive remeshing strategy for aerodynamics applications. A general high-order repartition of the variables for any subdivision of a cell is presented and then applied to an Adaptive Mesh Refinement module and a disassembling one for the intersected cells: a third-order accurate and conservative projection of the variables has been implemented. An assessment of the accuracy is performed on the advection of a vortex with and without a geometric intersection of grids. Finally a more complex functional test case is studied, it is the resolution of the wake structure of a transonic square cylinder

International audience; The inverse engineering of open-cell aluminum foams CAD were numerically investigated. The process is accomplished using mathematical programming MATLAB software. The basic principles are: first, in a certain range, a series of objects (spheres or ellipsoids) is randomly generated. The positions and sizes of the objects are both random. It is found that the mechanical parameters, such as collapse stress and absorbed energy, are dependent on the porosity of aluminum foams. A macroscopic model was chose to predict the compression behavior of open-cell foams. The procedure integrates Explicit solver of ABAQUS, OPTIFORM mesher and python script program transfer to execute step by step the incremental deformation process. At each step, the meshes are refined and coarsened automatically based on geometrical and physical error estimations; the physical fields are transferred from old to the new one using advanced algorithm.