18 research outputs found
Creep and flow of glasses:strain response linked to the spatial distribution of dynamical heterogeneities
Mechanical properties are of central importance to materials sciences, in
particular if they depend on external stimuli. Here we investigate the
rheological response of amorphous solids, namely col- loidal glasses, to
external forces. Using confocal microscopy and computer simulations, we
establish a quantitative link between the macroscopic creep response and the
microscopic single-particle dy- namics. We observe dynamical heterogeneities,
namely regions of enhanced mobility, which remain localized in the creep
regime, but grow for applied stresses leading to steady flow. These different
behaviors are also reflected in the average particle dynamics, quantified by
the mean squared dis- placement of the individual particles, and the fraction
of active regions. Both microscopic quantities are found to be proportional to
the macroscopic strain, despite the non-equilibrium and non-linear conditions
during creep and the transient regime prior to steady flow.Comment: 10 pages, 6 figure
One- and two-component colloidal glasses under transient shear
In concentrated colloidal mixtures different caging mechanisms exist and result in different arrested states: repulsive, attractive and asymmetric glasses as well as gel-like states. We discuss their microscopic structure, dynamics and rheological response. Special attention is given to the non-linear mechanical behaviour, in particular the transient rheological response after shear is started. Steps in both, shear rate and shear stress (creep test), are considered. The macroscopic viscoelastic response is related to the microscopic structure and dynamics on the individual-particle level