Dynamic and rate-dependent yielding in model cohesive suspensions

Abstract

An experimental system has been found recently, a set of coagulated CaCO3 suspensions, which shows very variable yield behaviour depending upon how it is tested and, specifically, at what rate it is sheared. At Péclet numbers (Pe)>1 it behaves as a simple Herschel-Bulkley liquid, whereas at Pe<1 highly non-monotonic flow curves are seen. In controlled stress testing it shows hysteresis and shear banding and in the usual type of controlled stress scan routinely used to measure flow curves, it can show very erratic and irreproducible behaviour. All of these features appear to arise from a dependence of the solid phase, or yield stress, on the prevailing rate of shear at the yield point. Stress..