Brookfield DV-III Ultra Rheometer Manual do Utilizador descarregar pdf (Página 60)

Brookeld Engineering Laboratories, Inc. Page 60 Manual No. M/98-211-B0104

Brookeld Engineering Laboratories, Inc. Page 60 Manual No. M98-211-E0912

IV.7.3 The Bingham Model

€

t =

€

(

€

= shear stress,

€

= yield stress, η = plastic viscosity, and D = shear rate)

What does it tell you?

The Bingham model indicates a product’s yield stress,

€

, which is the amount of shear stress

required to initiate ow. It also provides the plastic viscosity,

η, which is the viscosity after a

product yields.

Figure IV-50

When should you use it?

This model should be used with non-Newtonian materials that have a yield stress and then behave

in a Newtonian fashion once they begin to ow. As a result, the shear stress-shear rate plot forms

a straight line after yielding. (Products that have a yield stress only begin to ow after a certain

amount of shear stress is applied. They are also called “viscoplastic”. Their shear stress vs. shear

rate graphs intersect the y-axis at a point greater than 0.)

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Brookfield DV-III Ultra Rheometer Manual do Utilizador Página 60