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Analyse par thermographie infrarouge des effets dissipatifs de la localisation dans des aciers

Abstract : The understanding and modeling of localization mechanisms observed during the sheet forming process represent a major industrial issue. The goal of this work is to study localization phenomena appearing in steels during quasi static monotone tensile tests, through an experimental approach based on heat sources analysis. First, using heat equation and applying image processing to infrared thermal frames (effects) we propose a method able to estimate heat sources (causes) associated to the strain process. Then, we evidence on some mild steels that one or more narrow dissipative band propagate, with constant velocity, through the gauge part of the sample. Compared to this first mode (Lüders bands) where dissipative effects are very sudden, intense and strongly localized, we show that zones of mechanical irreversibility leading to localized necking are more diffuse and progressive. "Energetic localization indicators", proposed to detect the localization show that it can appear before the maximum load is reached, in various parts of the gauge sample. This result involves that the gauge part of a sample must be considered as a structure rather than a homogeneous volume element, which has important consequences on identification methods of constitutive models used, in particular, on theoretical localization approaches. Finally, some experiments performed on other materials highlight energetic manifestations associated with specific localization modes : propagation of phase transformation fronts (stainless steel A301), dissipative effects associated to glide bands (magnetic steel HiBiGO), dissipative effects localized in shear bands (polymer PVC).
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https://tel.archives-ouvertes.fr/tel-00259398
Contributor : Hervé Louche <>
Submitted on : Wednesday, February 27, 2008 - 9:51:51 PM
Last modification on : Friday, November 6, 2020 - 3:25:48 AM
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Hervé Louche. Analyse par thermographie infrarouge des effets dissipatifs de la localisation dans des aciers. Mécanique [physics.med-ph]. Université Montpellier II - Sciences et Techniques du Languedoc, 1999. Français. ⟨tel-00259398⟩

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