Flow-stress anomaly

Such flow-stress anomalies have also been shown by other phases with different crystal structures—e.g. FeCo-2V (cP2, B2), CuZn (B2), TiAl (tP4, Llo), FejAl (cF16, DO3), MgjCd (hP8, DO,). NijV (tI8, DO22), Fc2B (tI12,C16)—and various mechanisms have been proposed for these phases (Stoloff and Davies,... 

Ste] Stein, F., Schneider, A., Frommeyer, G., Flow Stress Anomaly and Qrder-Disorder Transition in FesAl-Based Fe-Al-Ti-X Alios with X = V, Cr, Nb, or Mo , Intermetallics, 11(1), 71-82 (2003) (Crys. Structure, Experimental, Meehan. Prop., 53)... 

Polymer chains anchored on solid surfaces play a key role on the flow behavior of polymer melts. An important practical example is that of constant speed extrusion processes where various flow instabilities (called sharkskin , periodic deformation or melt fracture) have been observed to develop above given shear stress thresholds. The origin of these anomalies has long remained poorly understood [123-138]. It is now well admitted that these anomalies are related to the appearance of flow with slip at the wall. It is reasonable to think that the onset of wall slip is related to the strength of the interactions between the solid surface and the melt, and thus should be sensitive to the presence of polymer chains attached to the surface. 

Mass flow is a bulk movement of hydrocarbons in monophase or dissolved in water. It requires an external force (pressure gradient or structural stress) and a well-defined conduit or plumbing system. The microseepage resulting from mass flow is therefore characteristically confined to a small area or belt, within which the anomalies are of high contrast and often contain some high molecular-weight hydrocarbons. 

Experience has shown structured fluids to be more difficult to manufacture, due to the complexity of their rheological profiles. In addition to elasticity, dilatancy, and rheopexy, certain structured fluid compositions may exhibit solid-like properties in the quiescent state and other flow anomalies under specific flow conditions. For emulsions and solid particulate dispersions, near the maximum packing volume fraction of the dispersed phase, for example, yield stresses may be excessive, severely limiting or prohibiting flow under gravity, demanding special consideration in nearly all unit operations. Such fluids pose problems in... 

In the case reported above, the viscosity anomaly in the region of isotropic solutions was not taken into consideration. However, if we plot both branches for different shear stresses, it is possible to obtain the following. The viscosity increases sharply for c > c with stress Xj, corresponding to segment I of the flow curve (Fig. 9.20, curve 1). For stress Xjj (quasi-Newtonian branch), the dependence t](c) is of the usual nature for LC solutions. For stress Xjn corresponding to region III of the flow curve, the viscosity has no maximum or even a break at c, but monotonically increases with an increase in c. Although curves 1 and 2 practically require no explanation, destruction of the LC structure... 

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