Dresden 2017 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

DY: Fachverband Dynamik und Statistische Physik

DY 39: Particulate Matter II: From microscopic interactions to collective motion (Focus session)

DY 39.1: Hauptvortrag

Mittwoch, 22. März 2017, 15:00–15:30, ZEU 118

Granular Materials: From solid to fluid with a variable jamming density — •Stefan Luding — MSM, UTwente, Enschede, NL

Soft, disordered, micro-structured materials are ubiquitous in nature and industry, and are different from ordinary fluids or solids, with unusual, interesting static solid-like and dynamic, fluid-like flow properties.

The transition from fluid to solid (at the so-called jamming density) features a multitude of complex mechanisms, (creep, relaxation, jamming, un-jamming and shear-jamming, or shear-thickening) but there is no unified theoretical framework that explains them all. In this talk, a simple yet quantitative and predictive model is presented, which allows for a variable, changing jamming density, encompassing the memory of the deformation history and explaining a multitude of phenomena at and around jamming.

The jamming density, a new state-variable, changes due to the deformation history and relates the systems macroscopic response to its micro-structure. The packing effciency can increase logarithmically slow under gentle tapping or repeated compression, leading to an increase of the jamming density. In contrast, shear deformations cause anisotropy and change the packing effciency exponentially fast with either dilatancy or compactancy as consequence. The memory of the system near jamming can be explained by a micro-statistical model that involves a multiscale, fractal energy landscape and links the microscopic particle picture to the macroscopic continuum description, providing a unified explanation for different deformation modes.