Brookfield DV2+Pro Viscometer Manual de usuario descargar pdf (Pagina 59)

Brookeld Engineering Labs., Inc. Page 59 Manual No. M03-165-F0612

Figure V1-15

When should you use it?

The Herschel-Bulkley model should be used with non-Newtonian, time-dependent materials that

haveayieldstress.Productswithayieldstressonlybegintoowafteracertainamountofshear

stressisapplied.Asaresult,theowcurveintersectsthey-axisatapointgreaterthan0.After

yielding,theproductcreatesaowcurveandbehavesasaPowerLawuidsothatnindicates

where there is a shear-thinning or shear-thickening tendency. (In this case, if n=1,thematerial

isbehavingasaBinghamuid,whichisdiscussednext.)

An Example of the Herschel-Bulkley Model at Work

A company uses a gel-like substance as part of

their production process. Upon arrival they test

the material and apply the Herschel-Bulkley

model to ensure it will perform correctly during

process.TheresultsingureVI-2showthat

the consistency index is 8,550 cP, the ow

index is 0.66, and the yield stress is 51.0 dynes/

. These results indicate that this batch of

geldoesnotquitemeetspecication.Whiletheconsistencyindexiswithinspec,theyield

valueishigherthannormalsotheuidwillnotbegintoowaseasily.Withaowindex

of 0.66, this batch is also less shear thinning than normal. Pump and mixer speeds must be

adjusted before using this material.

Gel-Like Substance

n = 0.66

= 51.0 dynes/cm

k = 8550 cP

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Brookfield DV2+Pro Viscometer Manual de usuario Pagina 59