Brookfield DV-I Prime Uživatelský manuál stáhnout pdf (Strana 37)

Brookeld Engineering Laboratories, Inc. Page 37 Manual No. M/07-022-D0613

II.12.5 Other Common Rheological Models

The NCA/CMA Casson Model

(1 + a)

€

2 t

(1 + a)

€

(

€

= 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 II-47

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

(h = viscosity, k = consistency index, R = rotational speed, n = shear sensitivity factor)

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 DV-I Prime Uživatelský manuál Strana 37