Simulation numérique de la mise en forme des métaux et les phénomènes de localisation pour les polycristaux CFC
Inal, A. Kaan
In this thesis, finite element analyses based on a rate-dependent Taylor-type polycrystal model have been developed to simulate sheet metal forming processes and localized deformation phenomena. This formulation can be applied to nonhomogeneous boundary-value problems for FCC polycrystals subjected to large deformations. The analysis inherently accounts for initial textures as well as deformation-induced anisotropies due to texture evolution. Both plane strain and plane stress finite element (FE) codes incorporating parallel computing algorithms have been developed so that simulations could be performed for applications requiring fairly large numbers of elements. Using the finite element codes which have been developed, instability and localization phenomena for the rolled aluminum sheet alloy AA3004-H19 under tension have been studied. The effects of various parameters on the formation of localized deformation bands have been investigated. These include initial texture and its evolution, strain hardening, material strain-rate sensitivity, loading direction, mesh sensitivity, geometric imperfections, and boundary conditions. Instability criteria have been defined for both necking and shear banding. The large strain behaviour of the rolled aluminum sheet alloy AA3004-H19 under planar simple shear has also been simulated numerically using both the plane strain and the plane stress polycrystal FE codes. The effects of the shearing direction on the overall shear stress--shear deformation curves and deformation patterns have been investigated. The initiation and propagation of shear bands have been studied in detail. Finally, the plane strain FE code was employed to simulate earing during the deep drawing of the rolled aluminum sheet alloys AA6111-T4 and AA5754-0. Simulations based on both the polycrystal model and a phenomenological constitutive law were performed where only the flange area of the sheet was analyzed. The effects of these textures were examined, and comparisons were made with experimental data.
- Génie – Thèses