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Advances in Condensed Matter Physics
Volume 2016, Article ID 1716598, 21 pages
http://dx.doi.org/10.1155/2016/1716598
Review Article

Normal Stress Differences and Yield Stresses in Attractive Particle Networks

1Department of Biomedical Sciences, Macquarie University, North Ryde, NSW 2109, Australia
2Department of Chemical and Biomolecular Engineering, The University of Melbourne, Parkville, VIC 3010, Australia

Received 13 August 2015; Accepted 1 December 2015

Academic Editor: Shengqiang Cai

Copyright © 2016 David I. Verrelli and Adam R. Kilcullen. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The nature of attractive particulate networks, yield stresses, and normal stress differences is systematically reviewed, each in terms of the relevant definitions, underlying mechanisms, and current measurement techniques. With this foundation, experimental observations of normal stress differences in some suspensions and colloidal systems are surveyed, along with constitutive models that allow for normal stress differences to arise prior to yielding. Yield stresses are a hallmark of attractive colloidal systems and vital in their processing. In contrast, little attention has been given to the role of normal stress differences in these systems. The presence or absence of normal stress differences necessarily affects the isotropy of the normal stress field through the solid particulate phase (treated as a continuum), in turn affecting estimation of yield stress. Given the importance of yield stresses in dealing with practical industrial problems, and in understanding fundamental behaviours, it is important to ensure that yield measurements can be relied upon.