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Brookeld Engineering Labs., Inc. Page 91 Manual No. M13-2100

VII.5 Other Rheological Models

The NCA/CMA Casson Model

(1+a) √τ

2√

+ (1+a) √hD

(τ

=shearstress

, τ

=yieldstress, h =plasticviscosity,and =shearrate)

TheNCA/CMACassonmodelisdesignedbytheNationalConfectionersAssociationandthe

ChocolateManufacturersAssociationasthestandardrheologicalmodelfortheindustry.This

modeldeterminesyieldandowpropertiesunderspeciedconditionsandcloselyapproximates

theplasticbehaviorofchocolatebeforenalprocessing.

Figure VII-5

Whenchocolateisusedforenrobing,itmusthaveayieldstresshighenoughtostayinplaceonce

itenrobesthelling.Inthecaseofdecoratingchocolate,theyieldstressmustbehighenoughsoit

cankeepitsshapeonceithasbeensqueezedintoplacethroughanozzle.Formoldingchocolate,

theplasticviscositymustbelowenoughtocompletelyllthemold.

(TheNCA/CMAlistsBrookeld’sHA-springrangeviscometerwithaSmallSampleAdapter,

SC4-27spindleandSC4-13Rsamplechamberastheapprovedapparatus.)

The IPC Paste Model

h=kR

TheIPCPasteModelwasdevelopedforsolderpastes.Itcalculatestheviscosityofsolderpastes

at10rpm.TheIPCPasteModel requires thattheproductbetested with aBrookeldSpiral

Adapteratmultiplespeeds.MoredetailscanbefoundintheIPC-TM-650TestMethodsManual

(methods2.4.34.2and2.4.3).

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Brookfield DV3T Rheometer Bedienungsanleitung Seite 91