Shear localization in colloidal glasses
- Event time: 1:00pm
- Event date: 26th April 2010
- Speaker: Rut Besseling (Formerly School of Physics & Astronomy, University of Edinburgh)
- Location: Room 2511, James Clerk Maxwell Building (JCMB) James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh EH9 3FD GB
We show, via simultaneous imaging and rheology, that hard sphere colloidal glasses in steady shear exhibit rate dependent and continuous shear localization. Near yielding and deep in the glass phase, shear is typically strongly localized near the walls and vanishing in the bulk, while at larger stress the nonlinearity smoothly decreases. While the data show apparent similarity with predictions for cooperative glassy flow, we argue instead that the phenomenology is due to small concentration gradients. We show theoretically that the system is unstable to growth of concentration fluctuations for vey moderate shear rates. These become 'frozen' in near yielding, which accounts for the variety of experimental observations. The instability is generic for systems with (i) a sufficient shear-induced contribution to the pressure and (ii) a strong concentration dependence of the characteristic (yield/flow) stress
This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..