Sommaire:

A defining mechanical property of amorphous materials is the existence
of a yield stress. In the case of soft materials, flow occurs only
when the applied stress exceeds a threshold value. Understanding the
mechanisms of yielding and subsequent flow is important for a variety
of rheological applications. In this context, it has been recently
proposed that spatially correlated plastic events drive the flow,
implying that spatial confinement would impact the nature of dynamical
properties. We explore these issues by using numerical simulations to
study the response of a confined quiescent glass to different stress
fields, viz. Couette (spatially homogeneous) and Poiseuille (spatially
inhomogeneous). We demonstrate how the dynamics at the local scale is
linked to observed macroscopic rheology. Further, using complementary
experimental studies, we try to build up the scenario for the onset of
flow in such materials.

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