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Structuration de la déformation plastique par l'effet Portevin-Le Chatelier : une analyse dynamique

Abstract : The Portevin Le Chatelier (plc) effect is one of the most fascinating forms of the plastic flow instabilities. This phenomenon consists in the repeated generation and propagation along a tensile specimen of sharply edged bands of localised plastic deformation. Experiments show that the plc effect is usually unperiodic and some models suggest that the instability might lead to determinist chaotic behaviour. In this work, this suggestion is investigated using a method of analysis based on the qualitative information contained in the temporal variations of the stress in loading with constant applied cross-head velocity. In this thecnic of a analysis, various implements are used : at first the method of delays is used to reconstruct phase trajectory of the dynamical system. The method use time series constututed from temporel variations of one state parameter of the system. The fractal structure of the reconstruction obtained suggest that the trajectory lie on a strange attractor which is the reflection of determinist chaotic dynamic. Indeed, confirmation of the existence of a strange attractor is done by calculating dimension of this attractor using the Grasseberger-Procaccia algorithm. The dimension obtained is lightly upper than three. Finally, sensitivity to initial conditions is prouved using the Gao-Zheng algorithm which give a positive value of the Lyapunov exponent. The above results permit to conclude that the underlying dynamic of the plc effect is determinist. Indeed, the dimension value of strange attractor suggests that a phenomenon description must take into account at least four state parameters of the system. This is compatible with some theories
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  • HAL Id : tel-01777212, version 1



Lahcen Quaouire. Structuration de la déformation plastique par l'effet Portevin-Le Chatelier : une analyse dynamique. Autre. Université Paul Verlaine - Metz, 1997. Français. ⟨NNT : 1997METZ027S⟩. ⟨tel-01777212⟩



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