Papers by Author: Laurence Giraud-Moreau

Abstract: As soon as it is question of modelling the follow-up of a geometry during an operation of forming process, the difficulties of meshing and remeshing are often emphases. If the part is situated between rigid tools (case of the deep drawing), in the problems of remeshing are also added difficulties on the management of the contact between the parts. In this case, the deformations are caused by the contact with the tools whose geometry are fixed. The piece must take the shape of the tool geometries during the deformation. In this paper, we present a method coupling an adaptive remeshing strategy and a technique of projection on the tool. The remeshing is based on refinement and coarsening procedures. The projection of the new nodes on the tool allows keeping the contact between the part and the tools. Numerical examples show the efficiency of the method.

Abstract: In this study, we present an experimental/numerical methodology which aims to improve 3D thin sheet hydroforming. The experimental study is dedicated to the identification of stress-strain flow by using the Nelder-Mead simplex algorithm optimization from the global measure of displacement and force. Applications are made to the simulation of thin sheet hydroforming using different die geometry to show the efficiency of the proposed methodology to localize plastic instability, thinning of the blanks and damage initiation under different forming condition.

Abstract: In this work, an adaptive remeshing scheme is presented in order to simulate with accuracy sheet metal forming processes. During simulations of metal forming processes, large plastic deformations with ductile damage occur and severe mesh distortion takes place after a few incremental steps. Hence frequent remeshing of the part must be performed in order to carry out the finite element analysis. The necessary steps to remesh the damaged structure during the simulation of the sheet metal forming process are given. The adaptive remeshing based on refinement and coarsening techniques, is controlled by geometrical and physical size maps. This remeshing strategy has been coupled with a projection method in order to avoid problems of contact between the part and the rigid tools. The influence of the remeshing is studied on numerical examples which show the capacity of the proposed procedure.

Abstract: This paper presents an advanced numerical methodology which aims to improve virtually any metal forming processes. It is based on elastoplastic constitutive equations accounting for non-linear mixed isotropic and kinematic hardening “strongly” coupled with isotropic ductile damage. During simulation of metal forming processes, where large plastic deformations with ductile damage occur, severe mesh distorsion takes place after a finite number of incremental steps. Hence an automatic mesh generation with remeshing capabilities is essential to carry out the finite element analysis. Besides, when damage is taken into account a kill element procedure is needed to eliminate the fully damaged elements in order to simulate the growth of macroscopic cracks. The necessary steps to remesh a damaged structure in finite element simulation of forming processes including damage occurrence (initiation and growth) are given. An important part of this procedure is constituted by geometrical and physical error estimates. The meshing and remeshing procedures are automatic and are implemented in a computational finite element analysis package (ABAQUS/Explicit solver using the Vumat user subroutine). Some numerical results are presented to show the capability of the proposed procedure to predict the damage initiation and growth during the metal forming processes.