Classification of Rheology Behavior

Figure I. Classification of rheological behavior in steady shear curve I, Newtonian curve 2, shear thickening curve 3, shear thinning curve 4, Bingham plastic and curve 5, nonlinear plastic.

The rheological properties show particularly large changes and in many cases the solutions show a non-Newtonian behavior and for a number of cases pronounced viscoelasticity has been demonstrated. That the classification of a certain surfactant depends very much on temperature is probably best illustrated by the viscosity of... 

Figure 3.2 illustrates a classification of the rheological behavior of solids and fluids. Examples of different flow behaviors are shown in the lowest boxes. Figure 3.2 also illustrates the resulting shear stress as a function of the (shear-)deformation y or, for fluids, the shear rate y. The two most important material properties for our discussion in this chapter are the viscoelastic and the Newtonian fluid circled in the figure. 

Figure 22.1 Classification of solids and liquids depending on their observed rheological behavior.

To a considerable extent, rheological properties of various disperse systems are determined by their random particle fluctuations. In the dispersed phase, these fluctuations play a leading role in the formation of a system of effective stresses that determine, in turn, the observable macroscopic flow characteristics of the dispersions. For this reason, any classification of the dispersions with respect to their hydrodynamic behavior must be based on careful consideration of the main physical mechanisms that induce particulate fluctuations, and that consequently determine fluctuation properties. 

CLASSIFICATION OF MATERIALS BASED ON THEIR RHEOLOGICAL BEHAVIOR... 

The classification of materials given here is based on the rheological properties discussed in the foregoing section. Elastic behavior is independent of the duration of the deformation but with viscous systems time-independent and time-dependent behavior may be distinguished. 

FIGURE 17.7 Rheological classification of solids (a) linear elastic, (b) nonlinear elastic, and (c) viscoelastic behavior. 

The presentation in this chapter dwells rather heavily on the classification, measurement, and interpretation of non-Newtonian behavior. These rheological fundamentals have frequently been presented in literature which is unfamiliar to the engineer and have usually included much discussion of factors which at the present time are of minor engineering interest. Accordingly, it was felt that one of the primary needs in this field was a concise summary of these fundamentals and common definitions. It is hoped that thereby future developments may be undertaken in an orderly and rigorous manner, as contrasted to the relatively fruitless empiricism which has enveloped areas of this field in the past. 

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