Hardening effects on formability limit prediction based on gurson-type damage models and bifurcation analysis

In this work, ductility limits of metallic materials, associated with the occurrence of strain localization, are predicted using the GTN damage model coupled with bifurcation theory. The resulting approach is implemented into the finite element code ABAQUS within the framework of large plastic strains and a fully three-dimensional formulation. A parametric study with respect to damage and hardening parameters is conducted in order to identify the most influential material parameters on strain localization. The analysis shows that the damage parameters have a significant impact on the predicted ductility limits, while the effect of hardening parameters on strain localization depends on the choice of void nucleation mechanism

Elastic-plastic analyses using the solid-shell finite element SHB8PS and evaluation on sheet forming applications - COMPLAS XI

In this contribution, the formulation of the SHB8PS continuum shell finite element is extended to anisotropic elastic–plastic behavior models with combined isotropic-kinematic hardening at large deformations. The resulting element is then implemented into the commercial implicit finite element code Abaqus/Standard via the UEL subroutine. The SHB8PS element is an eight-node, three-dimensional brick with displacements as the only degrees of freedom and a preferential direction called the thickness. A reduced integration scheme is adopted using an arbitrary number of integration points along the thickness direction and only one integration point in the other directions. The hourglass modes due to this reduced integration are controlled using a physical stabilization technique together with an assumed strain method for the elimination of locking. Therefore, the element can be used to model thin structures while providing an accurate description of the various throughthickness phenomena. Its performance is assessed through several applications involving different types of non-linearities: geometric, material and that induced by contact. Particular attention is given to springback prediction for a Numisheet benchmark problem

Prediction of strain localization during sheet metal forming using bifurcation analysis and Gurson- type damage - Complas XI

The strain localization phenomenon that may occur during sheet metal forming represents a major cause of defective parts produced in the industry. Several instability criteria have been developed in the literature to predict the occurrence of these instabilities. The proposed work aims to couple a Gurson-type model to the Rice’s localization criterion. The implementation of the modeling is achieved via a user subroutine (Umat) in Abaqus/std using a Runge-Kutta explicit integration scheme. Finally, we show the effectiveness of the proposed coupling for the prediction of the formability of stretched metal sheets

Comparison of bifurcation analysis and maximum force criteria in the prediction of necking in stretched metal sheets

In the present work, diffuse necking is investigated for stretched metal sheets using two different approaches, namely bifurcation theory and maximum force principle. The contribution includes a critical analysis and a systematic comparison of their respective ability to predict necking. In particular it is shown that, in contrast to bifurcation theory, which is of quite general applicability, some restrictions are associated with the application of maximum force conditions. It is noteworthy that the well-known Swift diffuse necking criterion is recovered through bifurcation analysis. Recall that Swift’s criterion has long been attributed in the literature to the maximum force principle, while it is shown here to rather originate from the bifurcation analysis, which provides it with a sound theoretical justification

A new flat shell finite element for the linear analysis of thin shell structures

In this paper, a new rectangular flat shell element denoted ‘ACM_RSBE5’ is presented. The new element is obtained by superposition of the new strain-based membrane element ‘RSBE5’ and the well-known plate bending element ‘ACM’. The element can be used for the analysis of any type of thin shell structures, even if the geometry is irregular. Comparison with other types of shell elements is performed using a series of standard test problems. A correlation study with an experimentally tested aluminium shell is also conducted. The new shell element proved to have a fast rate of convergence and to provide accurate results

Investigation of the effect of temper rolling on the texture evolution and mechanical behavior of IF steels using multiscale simulation

The main objective of this study is to simulate texture and deformation during the temper-rolling process. To this end, a rate-independent crystal plasticity model, based on the self-consistent scale-transition scheme, is adopted to predict texture evolution and deformation heterogeneity during temper-rolling process. For computational efficiency, a decoupled analysis is considered between the polycrystalline plasticity model and the finite element analysis for the temper rolling. The elasto-plastic finite element analysis is first carried out to determine the history of velocity gradient during the numerical simulation of temper rolling. The thus calculated velocity gradient history is subsequently applied to the polycrystalline plasticity model. By following some appropriately selected strain paths (i.e., streamlines) along the rolling process, one can predict the texture evolution of the material at the half thickness of the sheet metal as well as other parameters related to its microstructure. The numerical results obtained by the proposed strategy are compared with experimental data in the case of IF steels.French program “Investment in the future” operated by the National Research Agency (ANR)-11-LABX-0008-01, LabEx DAMAS (LST)

Stabilité d'une évolution visco-élastique ou visco-plastique

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