Brookfield DV3T User Manual

Brookeld Engineering Labs., Inc. Page 86 Manual No. M13-167-A0415
VII.4 The Casson Model
√hD
√τ =
√τ
o
+
(τ
=shearstress, τ
o
=yieldstress,h =plasticviscosity,and D =shearrate)
What does it tell you?
TheCassonmodelprovidesparameterssimilartothatoftheBinghammodel.However,unlike
theBinghammodel,itwasdevelopedformaterialsthatexhibitnon-Newtonianowafteryielding.
TheCassonmodelindicatestheproduct’syieldstress(τ
o
)whichistheamountofshearstress
requiredtoinitiateow,andtheproduct’splasticviscosity,
h,whichistheviscosityoftheproduct
afterityields.
Figure VII-4
When should you use it?
TheCassonmodelshouldbeusedwithnon-Newtonianmaterialsthathaveayieldstressandthat
donotexhibita“Newtonian-like”behavioroncetheybegintoow.Thismodelismostsuitable
foruidsthatexhibitPseudoplasticorshearthinning,owbehaviorafteryielding.
Theseuidshaveanon-linearowcurve.Thepointatwhichitcrossesthey-axisistheproduct’s
yieldstress(τ
o
).Toprotectthepointatwhichthecurvewillintersectwiththey-axis,theCasson
modellinearizesorstraightenstheplotbytakingthesquarerootofthedata.Toensureaccurate
extrapolationtoyieldstressitisbesttotakesomedataatlowshearrates.

Brookfield DV3T Specifications

General

Brand	Brookfield
Model	DV3T
Category	Measuring Instruments
Language	English