Brookfield DV2+Pro Viscometer Uživatelský manuál stáhnout pdf (Strana 63)

Brookeld Engineering Labs., Inc. Page 63 Manual No. M03-165-F0612

V1.3.5 Other Common Rheological Models

The NCA/CMA Casson Model

(1 + a) √τ = 2√τ + (1 + a) √ηγ

⋅

( τ=shearstress,

=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 V1-18

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 DV2+Pro Viscometer Uživatelský manuál Strana 63