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Etude des phénomènes d'auto-organisation des ensembles de dislocations dans un alliage au vieillissement dynamique

Abstract : In recent years, the plastic deformation more and more often studied in terms of the dynamics of complex systems, which is characterized by self-organization and involves various scales. This work presents a multi-scale investigation of the collective behavior of dislocations in an AlMg alloy prone to the Portevin-Le Chatelier (PLC) effect. To achieve this goal we have performed simultaneous recording of tensile curves, acoustic emission (AE), and local strain field, as well as quantitative characterization of the complexity through statistical and multifractal analyses. The results obtained proved that the apparent manifestations of the plastic deformation processes depend on the scale of observation. The analysis of the AE data revealed an inherently intermittent and scale-invariant behavior in all experimental conditions. These results suggest that at the scales pertaining to the AE, the plasticity may be governed by a universal dynamics, be it related to the PLC instability or macroscopically homogeneous flow. Despite the ubiquitous nature of this observation, the local strain field uncovers wave-like deformation processes, and the statistical analysis of stress serrations reveals characteristic scales. Synchronization of dislocation avalanches is conjectured to explain (under some experimental conditions) the transition from the mesoscopic to the macroscopic scale
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Youcef Bougherira. Etude des phénomènes d'auto-organisation des ensembles de dislocations dans un alliage au vieillissement dynamique. Autre. Université Paul Verlaine - Metz, 2011. Français. ⟨NNT : 2011METZ035S⟩. ⟨tel-01749084⟩

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