Brookfield DV-III Ultra Rheometer - Manual (Page 52)

Brookfield Engineering Laboratories, Inc. Page 52 Manual No. M/98-211-B0104
Brookfield Engineering Laboratories, Inc. Page 52 Manual No. M98-211-E0912
Model: HB Spindle: 34
Plastic Viscosity: 1906.3 cP
Yield Stress: 1976.88 D/CM2
Confidence of Fit: 63.6 %
The equation for each model is described below with a definition of parameters. Please contact
Brookfield or an authorized representative if further information is required.
Note: The confidence of fit parameter used in all of the models is an indication
of how well the model fits the data set. 100% indicates the best fit.
1. Casson (Standard)
The Standard Casson equation is: √τ = √τ
o + √η D where:
τ = Shear Stress
τ
o = Yield Stress (stress at zero shear rate)
η = Plastic Viscosity
D = Shear Rate
The calculated parameters for this model are:
Plastic Viscosity (cP or mPa•s)
Yield Stress (Dynes/cm2 or N/m2)
Confidence of Fit (%)
The Standard Casson method is a direct implementation of the original Casson equation.
2. NCA/CMA Casson (Chocolate)
This Casson method is derived from the standard set forth by the National Confectioners Association
(NCA) and the Chocolate Manufacturers Association (CMA). Although based on the original
Casson equation, this implementation has been tailored by the NCA and CMA specifically to
applications involving chocolate.
The Chocolate Casson equation is: (1+a)√τ = 2√τo + (1+a)√η D where:
τ = Shear Stress
τ o = Yield Stress (stress at zero shear rate)
η = Plastic Viscosity
D = Shear Rate
a = spindle (or bob) radius/ inner cup radius
The calculated parameters for this model are:
Plastic Viscosity (cP or mPa•s)
Yield Stress (Dynes/cm2 or N/m2)
Confidence of Fit (%)
3. Bingham Plastic
The Bingham equation is: τ = τ
o + η D where:
τ = Shear Stress
τ
o
= Yield Stress (stress at zero shear rate)
η = Plastic Viscosity
D = Shear Rate
The calculated parameters for this model are: