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or in the following form:τ1/2 = τC 1/2 + (ηC ⋅ γ ̇ )1/2

Flow curve model function with “Casson yield point” τC, i. e. where the fitting curve meets the τ-axis in a diagram on a linear scale, and “Casson viscosity” ηC (of 1959 [3.54]). For ηC the same applies as above for ηB, thus, ηC is not more than a coefficient to be used for curve fitting but it is not a real viscosity value.

This model function was originally designed for printing pastes. In 1973, OICC (Office International du Cacao et du Chocolat) or IOCCC (International Office of Cocoa, Chocolate and Confectionery), respectively, recommended for chocolate melts at T = +40 °C a testing and analysis method in the range of γ ̇ = 5 to 50 s-1 (60 s-1), by use of the Casson model. Evaluated are only the “Casson plastic viscosity“ and the “Casson yield value“ [3.55] [3.79].

Modifications of the Casson model:

1 “Generalized Casson model”: Here, instead of exponent 1/2 (which corresponds to the square root), the exponent 1/p is used.

2 Casson/Steiner : with form-factor a = (Ri/Re) = (1/δcc) of a cylinder measuring geometry, bob radius Ri (inner radius) and cup radius Re (external radius), and ratio of radii δcc (of 1958 [3.56]). For ISO cylinder measuring systems applies:

δcc = 1.0847, or a = (1/δcc) = 0.9219 (see Chapter 10.2.2.1a)

Then:

Summary: Using the Casson/Steiner model function, there is only a change in the “Casson yield point” when comparing to the original Casson model.