On the solid-liquid transition of concentrated suspensions in transient shear flow

Abstract.

The transition from solid-like to liquid-like behavior of suspensions of monodisperse spherical particles in a Newtonian continuous phase with varying solid volume concentrations and particle sizes was investigated in rotational shear flows. It was found that the solid-liquid transition takes place in a relatively narrow shear stress range, where the corresponding shear strain γ and the shear rate $\dot \gamma$ , respectively, increase over some orders of magnitudes. Below the transition region the material behaves like a nonlinear elastic solid with an initial linear range, i.e., $\gamma = f\left( \sigma \right)$ . The transition depends on the type of the shear loading and on the solid volume concentration. At high shear rates a nonlinear viscous behavior ($\dot \gamma = f\left( \sigma \right)$ ) with a terminal Newtonian range $\dot \gamma = {\sigma \mathord{\left/ {\vphantom {\sigma \eta }} \right. \kern-\nulldelimiterspace} \eta }$ was observed, if the solid volume concentration is below a critical value. Above this value the material behaves like a moist bulk solid material.