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Shear Localization in a Model Glass

F. Varnik, L. Bocquet, J.-L. Barrat, and L. Berthier
Phys. Rev. Lett. 90, 095702 – Published 3 March 2003
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    Abstract

    Using molecular dynamics simulations, we show that a simple model of a glassy material exhibits the shear localization phenomenon observed in many complex fluids. At low shear rates, the system separates into a fluidized shear band and an unsheared part. The two bands are characterized by a very different dynamics probed by a local intermediate scattering function. Furthermore, a stick-slip motion is observed at very small shear rates. Our results, which open the possibility of exploring complex rheological behavior using simulations, are compared to recent experiments on various soft glasses.

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    • Received 13 August 2002

    DOI:https://doi.org/10.1103/PhysRevLett.90.095702

    ©2003 American Physical Society

    Authors & Affiliations

    F. Varnik1, L. Bocquet2, J.-L. Barrat2, and L. Berthier3

    • 1CECAM, ENS-Lyon, 46 Allée d’Italie, 69007 Lyon, France
    • 2Département de Physique des Matériaux, Université Lyon I and CNRS, 69622 Villeurbanne CEDEX, France
    • 3Theoretical Physics, Oxford University, 1 Keble Road, Oxford, OX1 3NP, United Kingdom

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    Issue

    Vol. 90, Iss. 9 — 7 March 2003

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    • Figure 1
      Figure 1
      Filled symbols: rescaled velocity profiles, u(z)/Uwall, from two independent simulation runs. In both cases, the left wall is moved with a constant velocity Uwall=3.33×10−3 (γ˙tot=0.83×10−4). Because of Galilean invariance, the sheared region may be located at either the moving or immobile wall. Open symbols: rescaled velocity profiles obtained at higher wall velocities Uwall=3.33×10−2 and 3.33×10−1 corresponding to overall shear rates of γ˙tot=0.83×10−3 and 0.83×10−2. Note that the local shear rate of the sheared region is smaller at smaller Uwall.Reuse & Permissions
    • Figure 2
      Figure 2
      Left panel: Intermediate scattering function, ϕq(t;z), computed within layers of thickness dz=2. From bottom to top, z=−17,−15,…,15,17. The temperature is T=0.2, and γ˙tot=0.83×10−4. The vertical dashed line marks the time τ0=5754≈0.5/γ˙tot. Right panel: plot of ϕq(τ0;z) (connected diamonds), velocity profile (filled circles), local shear stress σxz(z) (connected triangles), normal pressure PN(z) (open diamonds) , and density profile ρ(z) (connected stars).Reuse & Permissions
    • Figure 3
      Figure 3
      Connected diamonds: σxz versus γ˙ under homogeneous flow conditions at T=0.2. Connected circles: σxz versus γ˙tot in the boundary-driven shear flow. The vertical dashed line is an estimate of the global shear rate below which shear localization is expected.Reuse & Permissions
    • Figure 4
      Figure 4
      Shear stress versus time for γ˙tot=0.83×10−6 at T=0.2. The stress rises up to a value close to σy≃0.65, before suddenly dropping to a value smaller than the one obtained in a homogeneous flow (σxz≃0.4).Reuse & Permissions
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