Authors: Anthony D Stickland Ashish Kumar Tiara E Kusuma Peter J Scales Amy Tindley Simon Biggs Richard Buscall
Publish Date: 2015/03/21
Volume: 54, Issue: 5, Pages: 337-352
Abstract
Measuring yielding in cohesive suspensions is often hampered by slip at measurement surfaces This paper presents creep data for strongly flocculated suspensions obtained using vaneincup tools with differing cuptovane diameter ratios The three suspensions were titania and alumina aggregated at their isoelectric points and polymerflocculated alumina The aim was to find the diameter ratio where slip or premature yielding at the cup wall had no effect on the transient behaviour The large diameter ratio results showed readily understandable material behaviour comprising linear viscoelasticity at low stresses strainsoftening close to yielding timedependent yield across a range of stresses and then viscous flow Tests in small ratio geometries however showed more complex responses Effects attributed to the cup wall included delayed softening slip multiple yielding and stick–slip events and unsteady flow The conclusion was that cups have to be relatively large to eliminate wall artefacts A diameter ratio of three was sufficient in practice although the minimum ratio must be material dependent
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