Casson’s equation

In the second method, the data were fitted to Casson s equation (7), ie.,... 

Carcass method Carnot cycle Carothers Casson s equation Catalyst (general)... 

Equation 7.48 described the extensional viscosity behavior of a PE/mica system well, after subtracting the yield stress using Casson s equation (Utracki and Lara 1984). 

A typical feature of filled polymers in a mixture is the appearance of the yield stress which is due to the formation of the structural network formed by filler particles. For the LC polymer-PSF mixtures the yield stress Tq was determined from Casson s equation [19] ... 

For foods, such as chocolates, that can be described by the Casson model (Equation 2.5), Steiner (1958) chose not to develop an explicit expression for the non-Newtonian shear rate, but related j>n to the Casson model parameters Koc,Kc, and shear stress, (7. Steiner s approach is valid for values of a = (n/ro) between 0.5 and 0.9, and j>n values greater than 0.1 s when a — 0.9 and 0.01 s when a = 0.5. 

The rheological curves of thixotropic fluids, such as IP 680 in Figure 21, show that there is a yield stress tq to overcome before shear can take place. This phenomenon is taken into account in Casson s model represented by the equation = (tq) - - [tioldy/dt)] , where the yield stress tq is usually determined by extrapolating to zero shear the curve representing the variation of the shear stress at different shear rates. For the sake of convenience, conductive adhesive pastes are often characterized by a thixotropy index, which is the ratio of the viscosities... 

The rheological curves of thixotropic fluids, such as IP 680 in Fig. 12.20, show that there is a yield stress To to overcome before shear can take place. This phenomenon is taken into account in Casson s model represented by the equation +... 

The three-dimensional forms of the Herschel-Bulkley (eq. 2.5.6) and Casson (eq. 2.5.5) equations, with Papanastasiou s modiflcation, are as follows. 

In this chapter we have developed the general constitutive equation for a viscous liquid. We found that by using the rate of deformation or strain rate tensor 2D, we can write Newton s viscosity law properly in three dimensions. By making the coefficient of 2D dependent on invariants of 2D, we can derive models like the power law. Cross, and Carreau. We also showed how to introduce a three-dimensional yield stress to describe plastic materials with models like those Bingham and Casson. We saw two ways to describe the temperature dependence of viscosity and the importance of shear heating. 

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