Séminaire Liquides/Mat. molle

Mardi 15 Novembre 2016 à 11h00.

Playing around the granular jamming transition: from advantages of the change in behavior to dramatic limitations

''Granular media are surprising kinds of materials: on a large scale they have the ability to behave as a solid (walking on wet sand on a beach), a liquid (flowing sand between fingers), or even a gas (sandstorm in a desert) depending on their local properties (grain scale) or on their macroscopic loading. For simple sphere or cylindrical particles the transition between these different phases, more particularly the jamming transition (between liquid and solid behaviors) has been widely studied during the two past decades and is now well understood. However, there is a growing interest in functionalizing particles at the micro-scale to tune the global properties of the material. This change in behavior from the local scale to the system size as well as the stability of these specific properties need to be understood to improve and secure applications. In this seminar, I will present results from 2D and 3D experimental and numerical set-ups that permit to change grain properties and measure their effect at the global scale under different loadings. Using photo-elastic method and 3D-scan reconstruction, I will first present how the local interactions and particle geometry change the properties of the jamming point. Then, in the simple case of 2D discs, I will describe the statistics of rearrangement of a sheared granular material using crackling statistical physics tools.''