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IRTG / Soft Matter Science
Freiburger Materialforschungszentrum
Stefan-Meier-Str. 21
79104 Freiburg, Germany


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You are here: Home Events Prof. Thomas Voigtmann "History dependent material properties of glasses"

Prof. Thomas Voigtmann "History dependent material properties of glasses"

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Institut für Theoretische Physik, Universität Düsseldorf & Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt, Köln

  • Seminar
When Jan 25, 2017
from 02:15 PM to 03:00 PM
Where Seminarraum A, FMF, Stefan-Meier-Str. 21, Freiburg
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Long-lasting memory effects arise from slow structural relaxation in glass-forming fluids and cause material properties to depend on the preparation history, since in producing a solid from the molten state, the relaxation from the flowing nonequilibrium steady state back to equilibrium "gets stuck" [1]. For example, "residual stresses" arise, that are sometimes unintended side-effects (stress birefringence of plexiglass) and sometimes deliberately tuned to achieve optimal material properties (modern smartphone glass covers, spider silk). The material is no longer characterized by the thermodynamic control variables alone, but rather in addition by the history of past external fields. Since there is no separation of time scales between the slow microscopic dynamics and macroscopic flow fields, a multi-scale approach is needed to explain how the material properties of soft glasses depend on the past flow.

In this talk, I will discuss how this history dependence arises from microscopic theory and the principles of nonequilibrium statistical physics [2], and how it translates to the macroscopic continuum scale. For the latter, we have developed an algorithm that combines the microscopic mode-coupling theory of nonlinear glassy rheology (MCT) with the Lattice Boltzmann (LB) technique for solving the Navier-Stokes equation [3]. This hybrid-LB-MCT algorithm is able to deal with material laws that are non-stationary integral equations with long-lived memory kernels. I will demonstrate how flow in the melt imprints residual-stress patterns on the glass after solidification.

[1] Th. Voigtmann, Curr. Opin. Colloid Interf. Sci. 19, 549 (2014).
[2] M. Ballauff et al., Phys. Rev. Lett. 110, 215701 (2013); Physics 6, 60 (2013).
[3] S. Papenkort and Th. Voigtmann, J. Chem. Phys. 143, 204502 (2015).

invited by Eckart Bartsch

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