Étude du développement des instabilités dans un anneau en expansion dynamique

Abstract : Linear Stability Analysis has been widely used in order to describe the evolution of the dominant necking pattern in different configurations. However, experimental and numerical observations have demonstrated that a distribution of internecking lengths is obtained instead of a unique dominant pattern. In this work, an extension of the classical Linear Stability Analysis applied to the dynamic extension of a round bar case has been developed to take into account the contribution of all perturbation modes on the final necking pattern. This approach, corresponding physically to the case of thin ring expansion, is able to determine a distribution on internecking distances. Based on the same mathematical tools that was developed for the extension of the linear stability analysis, a new numerical approach has been followed to determine the number and the onset time of necking with respect to loading velocity, amplitude and cell size of the perturbations. A comparison, in terms of distributions of inter-necking distance, has been carried out between analytical and numerical results. Good correlations have been observed. An electromagnetic ring expansion experimental device has been proposed during this work. Whith some additional development, it should enable to validate experimentally the working assumptions developed in the numerical and analytical studies
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Skander El Maï. Étude du développement des instabilités dans un anneau en expansion dynamique. Matériaux. Université de Lorraine, 2014. Français. ⟨NNT : 2014LORR0076⟩. ⟨tel-01750799⟩

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