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Etude de l'interaction entre endommagement ductile et striction dans les tôles minces : application à la prédiction de la formabilité.

Abstract : Sheet metal forming is undoubtedly a manufacturing process that has massive applications in numerous industrial sectors, such as automotive, aerospace, home appliance and food industry. Various defects may occur during the forming processes, such as wrinkling, and those inherent to material plastic instabilities, such as necking, which are responsible for limiting the formability. Therefore, controlling such plastic instabilities results in enhanced productivity and high quality of products during the manufacturing process. The concept of forming limit diagram (FLD) provides the limits to the deformations that sheet metals can withstand without the occurrence of undesirable defects. The current work contributes to the development of theoretical and numerical tools for the predictions of FLDs, which leads to a complementary approach to experimental tests. For this purpose, phenomenological Gurson-based damage constitutive models are considered in the present contribution. For the prediction of plastic instabilities, both diffuse and localized necking criteria, which are based on the bifurcation theory and multi-zone (initial imperfection) approach, have been implemented and compared to each other in terms of their order of prediction of critical necking strains. It has been found that the critical strains are lowered when the void size is increased for porous materials. In other words, decreasing the void size has a beneficial effect on the material formability. The predicted FLDs show that for all the considered constitutive models, the general bifurcation criterion is a lower bound to all the bifurcation criteria, in terms of necking prediction. As to the prediction of strain localization, the loss of ellipticity criterion provides an upper bound as compared to the initial imperfection approach and other bifurcation criteria.
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Submitted on : Monday, May 23, 2022 - 8:32:19 AM
Last modification on : Friday, August 5, 2022 - 2:54:00 PM

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  • HAL Id : tel-03675255, version 1

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Muhammad Waqar Nasir. Etude de l'interaction entre endommagement ductile et striction dans les tôles minces : application à la prédiction de la formabilité.. Mécanique des matériaux [physics.class-ph]. HESAM Université, 2021. Français. ⟨NNT : 2021HESAE016⟩. ⟨tel-03675255⟩

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