Nonlinear mechanical response of supercooled melts under applied forces

Abstract

We review recent progress on a microscopic theoretical approach to describe the nonlinear response of glass-forming colloidal dispersions under strong external forcing leading to homogeneous and inhomogeneous flow. Using mode-coupling theory (MCT), constitutive equations for the rheology of viscoelastic shear-thinning fluids are obtained. These are, in suitably simplified form, employed in continuum fluid dynamics, solved by a hybrid-Lattice Boltzmann (LB) algorithm that was developed to deal with long-lasting memory effects. The combined microscopic theoretical and mesoscopic numerical approach captures a number of phenomena far from equilibrium, including the yielding of metastable states, process-dependent mechanical properties, and inhomogeneous pressure-driven channel flow.

Amorphous Order & Non-linear Susceptibilities in Glassy Materials

“…Following up on these non-linear dielectric susceptibilities experiments, non-linear mechanical responses have been studied in glassy colloids [36]. In that case, one can probe experimentally a milder regime of super-cooling in which the growth of nonlinear responses can be well explained by Mode Coupling Theory and its extensions [36,37].…”

Recent advances on glass-forming systems driven far from equilibrium

“…As one of the highlights reported here, the structure of the critical clusters at the thermodynamic glass transition could be revealed [9]. The dependence of the breakdown of linear response to the chosen external field variable for the different experimental protocols needs careful consideration from the theoretical perspective as described in reference [3]. Furthermore, in reference [8] the breakdown of linear response when approaching the critical point in Lorentz gases is monitored, revealing where the impact of increasing correlation lengths can be studied.…”

“…In reference [1], stresses are applied macroscopically to metallic alloys ('creep under load'), while reference [2] describes the behavior of mixtures of colloids under load. Reference [3] continues with colloidal dispersions from a theoretical point of view, comparing macroscopic creep with theory and simulation of pressure driven flow confined in channels. There a characteristic inhomogeneity in the flow field is the formation of a plug.…”

“…Micro-rheology in dense granular fluids also records spatial correlations around pulled intruders [5]. Reference [3] reports inhomogeneities which originate from the boundary conditions of flows through confinements. The effects of nonlocal terms in constitutive equations are tested comparing to simulations.…”

“…Also, the response under different applied external drivings is studied, shear-rate controlled vs stress-controlled, and differences in the transient approach to the stationary state are related to the microscopic particle motion and to (intermediate) heterogeneous structural dynamics. The link between the (overdamped) motion of individual particles and the macroscopic mechanical response is picked up from the view point of theory in the report by Cárdenas et al [3]. Motion enforced by large forces, yielding under static load, and pressure-driven inhomogeneous flow through narrow channels are studied.…”