Regensburg 2016 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 60: Pattern Formation (Joint Session with DY)

BP 60.1: Hauptvortrag

Donnerstag, 10. März 2016, 09:30–10:00, H46

Patterns formation through elastic instabilities, from thin sheets to twisted ribbons — •Pascal Damman — Université de Mons, Mons, Belgium

Hydrodynamics instabilities, such as Bénard-Marangoni convection, Rayleigh-Plateau, Rayleigh-Taylor and many others, are well known to produce beautiful patterns. Capillary, viscous and/or inertial forces conspire to generate very regular morphologies. In this seminar, we will see that elasticity can also produce complex structures, either regular or fully random, provided that slender objects are used. These objects are usually classified as rods, shells or sheets.

In the "classical picture", thin sheets constrained by external forces minimize the elastic energy through focalization of deformation in singularities. We will see that, due to geometric constraints, these origami structures cannot always be obtained. In the second part, the formation of very regular wrinkles in sheets "glued" on a soft foundation will be discussed. At the threshold, these wrinkles reflect the competition between various forces. For large deformations, however, the morphology is surprisingly determined by the nature of the foundation. Fold localization or period-doubling bifurcations are indeed observed for liquid or solid substrate, respectively. Finally, the effect of specific geometrical constraints produced by twisting thin ribbon of elastic materials will be discussed.

Finally, these various studies also highlight the effort of this growing interdisciplinary researcher community to the emergence of a global picture of elastic instability.