This article deals with numerical simulation of necking. It draws the attention onto the importance of the description of strain-hardening and the effects on the evolution of necking. In order to compare necking evolution in relation with different plasticity models, a tracking procedure which consists in determining the evolution over time of discharged volumes of the sample is adopted. Models that take into account physical phenomena at the microscopic level and especially the heterogeneities of materials from a mechanical point of view seem well suited to fit experimental evidence connected to necking.

International audienceNowadays, numerical simulation by finite element analysis is an essential tool that allows performing virtually sheet metal forming processes, and therefore to reproduce various phenomena such as springback (SB) and necking that are generated by plastic deformation. However, the quality of the model used to represent the mechanical behaviour is a determining factor for the realism of numerical simulations. To perform well, the model must reproduce all the properties of the material such as the anisotropy and the strain hardening induced by plastic deformation. The main purpose of this work is to show, by means of numerical simulations, the influence of constitutive modelling on the prediction of the degree of SB in the case of a stretch bending test. Tests have been carried out on titanium sheets which have a wide range of applications for high tech industries because of specific mechanical and physical properties. At the same time, we have investigated the dependence of some process parameters such as the clamping force on SB. In order to prove the accuracy and reliability of the proposed finite element model, experimental data were used to compare with the numerical results

No abstract

Generally, the sheet metal forming processes by plastic deformation are difficult to control owing to the multiple phenomena that can occur and disrupt the operation: the springback, the localization, the wrinkling, etc. The springback is a physico-mechanical phenomenon due to the return of the elastic energy stored during the loading phase, which leads to a change in the dimensions of the formed part. In fact, the improvement of the operation presents some complications because an important number of parameters that affect the springback and that can be accurately understood by the use of finite element analysis. In particular, the springback appears so prominent in the bending operations; this mode of deformation is the focus of this work which consists of two main parts: - Mechanical characterization of two alloys frequently used in aerospace manufacturing: aluminum 1050A and titanium T40 commercially available in the form of cold-rolled thin sheets. The conventional and rational curves are obtained by using a tensile test machine (Instron 50kN). - Finite element simulation of a V-bending operation of sheet metal with both materials. This study allows us to calibrate the numerical procedures that could be included in more complex operations.