Amortissement par le branchement des structures flexibles : une approche bio-inspirée des arbres

Abstract : Extreme dynamical loads are a cause of damage of man-made structures. In nature, some plants, trees in particular, repeatedly endure extreme loads mostly caused by strong climatic events. For such living structures, it is of vital importance to efficiently dissipate mechanical energy received by such loading conditions and evolution may well have optimized their damping mechanism. The bio-inspired idea defended here is that structural branching of flexible structures brings a robust and specific damping mechanism for vibrations of large amplitude. The large amplitude dynamics of an elementary branched model with two degrees of freedom is studied, showing a non-linear energy transfer between normal modes. This transfer originates in the geometrical nonlinearities, explained by the centrifugal forces acting on branches when the trunk oscillates. The transfer is effective when the frequency ratio of the corresponding normal modes is approximately 2. This mechanism, coined \mbox{"damping by branching"}, is specifically efficient to dampen large amplitude vibrations. It appears as robust against the variety of possible sources of dissipation of the structure, including the interaction with a surrounding fluid. Using the finite element method and a flexible beam approximation, the dynamics of a continuous branched model, excited by pull-and-released or by harmonic forcing, is analysed and demonstrates the applicability of the mechanism to more complex structures. This damping mechanism is experimentally displayed on a flexible branched structure of which modal frequencies have been tuned. These results lead to the design of a branched dynamic absorber for rotating systems, which offers better performances than those of a conventional and equivalent dynamical absorber in a certain range of amplitudes. Finally, the analysis of a multiple-branched model suggests that this mechanism is actually present in trees.
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Contributor : Benoit Theckes <>
Submitted on : Friday, January 18, 2013 - 12:11:29 AM
Last modification on : Wednesday, March 27, 2019 - 4:39:25 PM
Long-term archiving on : Friday, April 19, 2013 - 4:01:00 AM

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Benoit Theckes. Amortissement par le branchement des structures flexibles : une approche bio-inspirée des arbres. Vibrations [physics.class-ph]. Ecole Polytechnique X, 2012. Français. ⟨pastel-00777733⟩

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