An attempt to categorize yield stress fluid behaviour - Moller, Peder and Fall, Abdoulaye and Chikkadi, Vijayakumar and Derks, Didi and Bonn, Daniel
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES 367, 5139-5155 (2009)
Abstract : We propose a new view on yield stress materials. Dense suspensions and
many other materials have a yield stress-they flow only if a large
enough shear stress is exerted on them. There has been an ongoing debate
in the literature on whether true yield stress fluids exist, and even
whether the concept is useful. This is mainly due to the experimental
difficulties in determining the yield stress. We show that most if not
all of these difficulties disappear when a clear distinction is made
between two types of yield stress fluids: thixotropic and simple ones.
For the former, adequate experimental protocols need to be employed that
take into account the time evolution of these materials: ageing and
shear rejuvenation. This solves the problem of experimental
determination of the yield stress. Also, we show that true yield stress
materials indeed exist, and in addition, we account for shear banding
that is generically observed in yield stress fluids.