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Pliage de tiges et rupture de plaques

Abstract : The deformation of elastic materials can lead to singularities, which allow to focus energy. In this work, we have been interested in two examples: folds which appear when a rod is confined and cracks in a plate. The first part of this thesis concerns the folding of an elastic rod in a 2D space. The geometry of the resulting configurations is constrained by self-avoidance as well as by the dimensionnality of both structure and container. In a first experiment, we follow the dynamics of the confinement of a ring of swelling gel. We show that the phase space becomes more and more complex when the confinement is increased. In a second experiment, an elastic rod is reversibly folded at the center of a circular Hele-Shaw cell by a centripetal force. The wide diversity of the configurations calls for a statistical approach. We show that folded patterns become ordered when the strength of confinement is increased, because of the stacking of layers of rod. Finally, we introduce the notion of the compressibility of the folded rod as a response to a mechanical perturbation and show that this quantity is a measure of the disorder. In a second part, we study cracks propagation in a thin brittle elastic plate submitted to out-of-plane shear mode. The experimental setup mimics the common way in which one tears a sheet of paper. We find that the geometry of the sheet is determined by the direction of a large scale force, applied to the crack tip. This force is perpendicular to cracked surfaces. While the material is deformed at large scales under mode III loading, the geometry of system in the vicinity of the crack tip adapts so that the material is locally broken under a pure mode I loading. In a second experiment, we consider the interaction of two cracks propagating simultaneously. We observe that the cracks paths merge and produce a strip of well-defined shape, which is driven by the elastic deformations of the plate within the central fold.
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Contributor : Elsa Bayart <>
Submitted on : Thursday, October 28, 2010 - 7:27:36 PM
Last modification on : Thursday, December 10, 2020 - 12:37:26 PM
Long-term archiving on: : Thursday, December 1, 2016 - 9:40:50 PM

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  • HAL Id : tel-00530406, version 1

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Elsa Bayart. Pliage de tiges et rupture de plaques. Physique [physics]. Université Pierre et Marie Curie - Paris VI, 2010. Français. ⟨tel-00530406⟩

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