Flow anisotropy effects

Although the Izod and Charpy tests are widely used for plastics, other types of test are also popular. These include tensile impact tests and flexural plate (falling weight) tests. The latter is particularly useful in situations where the effects of flow anisotropy are being assessed. In addition, arbitrary end-product tests are widely used to provide reassurance that unforseen factors have not emerged to reduce the impact performance of the product. 

Differences in coke behaviour in the blast furnace (not detectable by cold testing prior to the charging of the blast furnace) may be attributable to differences in the mode of gasification of the coke as a result of combined effects of thermal and gasification fissuring. These results indicate that mosaic optical textures are preferable to flow anisotropy in terms of fissure containment and also show that inert particles can act as centres of fissure generation. 

The use of the Knox plots to study the causes of micellar reduced efficiencies leads to the following conclusions. The micellar phase flow anisotropy seems to be much higher than the flow anisotropy obtained with a hydro-organic phase of comparable viscosity (increased A term). This is only partly due to the micellar viscosity. The main reason of such differences in flow patterns is the partial clogging of the stationary phase pores by adsorbed surfactant molecules [19, 22]. A temperature raise decreases the mobile phase viscosity and the amount of adsorbed surfactant [22]. Both effects decrease the flow anisotropy and the A term. It will be exposed thereafter that alcohol additions to a micellar phase dramatically reduce the amount of adsorbed surfactant. 

The most striking change is in the A-term that accounts for multipath dispersion (Equation [3.33] in the van Deemter theory) and decreases rapidly with decreasing i.d. This effect was interpreted (Karlsson 1988) as reflecting a decrease in the extent of the flow rate variation over the column cross-section as the i.d. decreases, together with shorter time for solute molecules to diffuse radially through the flow velocity profile (parabolic in the case of a nonpacked column) together these phenomena will decrease the effect of flow anisotropy that is reflected in... 

The basic factor which causes a decrease in the viscosity in the transition into the LC state is thus the cooperative orientation of the major axes of the macromolecules along the direction of flow (anisotropy of viscosity), but the scale of this decrease will be a function of the presence of phase heterogeneity, the amount of inhomogeneities (disclinations), the range of the effective stress, and in particular, the concentration of the solution. 

Flow induced anisotropy effects in filled rubber compounds. (Drawn using data from K. Nakashima, H. Fukuta, M. Mineki, /. Appl. Polym. Sci., 17, 769-778,1973.)... 

Wallace [15], [16] gives details on effects of nonlinear material behavior and compression-induced anisotropy in initially isotropic materials for weak shocks, and Johnson et ai. [17] give results for infinitesimal compression of initially anisotropic single crystals, but the forms of the equations are the same as for (7.10)-(7.11). From these results it is easy to see where the micromechanical effects of rate-dependent plastic flow are included in the analysis the micromechanics (through the mesoscale variables and n) is contained in the term y, as given by (7.1). 

The flow velocity, pressure and dynamic viscosity are denoted u, p and fj and the symbol (...) represents an average over the fluid phase. Kim et al. used an extended Darcy equation to model the flow distribution in a micro channel cooling device [118]. In general, the permeability K has to be regarded as a tensor quantity accounting for the anisotropy of the medium. Furthermore, the description can be generalized to include heat transfer effects in porous media. More details on transport processes in porous media will be presented in Section 2.9. 

Figure 5. Effect of anisotropy on flow decay of 0.45pM Tyrann-M/E and conventional membranes with 0.01% Triton X-400 solutions. Relative pore size adjacent to feed 1 = Tyrann-M/E, large 2 — Tyrann-M/E, small 3 = conventional, large 4 = conventional, small.

All electrooptical effects known to the present time for polymeric liquid crystals may be divided into two groups. First of all there are so called orientational effects, which are due solely to the effect of the electric field (field effect) on LC polymers, but are not a result of a current flowing. The second group of electrooptical effects is attributed to the phenomena ascribed to the anisotropy of electrical conductivity (Act) of liquid crystals. These are called electrohydrodynamic effects. 

Rheological properties are particularly sensitive and for some solubilizates, such as a-methylnaphthalene, the solutions may become viscoelastic the appearence of viscoelasticity often depends on subtle effects in chemical structure29). Certain spectroscopic features are strongly influenced. Thus the H and 13C NMR line widths show large increases, the 81 Br quadrupole relaxation may be strongly affected and there may be the appearance of linear dichroism, birefringence and conductance anisotropy for flowing systems. 

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