Isoviscous point

The Breakdown of Fluid Film Lubrication in Elastic Isoviscous Point Contacts, Wear, 1980, 63, 1, 25. ... 

Medley, J.B., Strong A.B., Pilliar, R.M., Wong, E.W. The breakdown of fluid film lubrication in elastic-isoviscous point contacts. Wear 63, 25-40 (1980)... 

R.E. Robertson (University of Michigan, Ann Arbor, Michigan) Ray, you also considered the glass transition in your way of thinking, is that also an isoviscous point ... 

Tg is an isoviscous point for all glasses occurring at about 10 - Pas. The ratio of 7 to the hquidus, expressed in Kelvin, for most glasses is usually close to 0.67. This so-called two-thirds rule is a useful rule of thumb. 

Figure 10.19 Viscosity-temperature curves for [Geo.sSo./lioo-xlx glasses in the range 0 < x < 30 were measured using indentation viscometry with a cylindrical probe [36 (a) isoviscous points are found to shift to a lower temperature as the iodine content is increased (b) addition of iodine tends to break down the connectivity of the network in the supercooled melt producing an increasingly fragile liquid [8, 36 and 37). , 0at% I A, 5at% I , 10at% I A, 15at% I o, 20at% I.

FIGURE 8.11 State diagram for food materials, showing the Tg curve and isoviscous states above Tg. Maximally freeze-concentrated solids with a solute concentration of C g have Tg at T g. Ice melting within maximally freeze-concentrated materials occurs at T m. The equilibrium melting curve shows the equilibrium melting point Tm as a function of concentration. (From Roos, Y.H. and Karel, M., Food Technol., 45, 66, 1991b.)... 

The slopes of the plots in Fig. 3.10 were around —0.7 and, hence, smaller than unity as expected. Again, in all of the cases studied similar linearity was observed. On the basis of these results, we concluded that the AH model is a better description of our slow reaction systems. Now the next step is to examine whether it is possible to obtain further information on the extent of correlation of the two coordinates. Figure 3.10 gives an important hint on this point. The isoviscous tern-... 

In the plezovlscous case Che point of minimum film thickness was found to move from a position on the contact centre line at the exit constriction by dividing and following the development of side lobes parallel to the direction of entrainment. In Che Isoviscous case the development of side lobes still takes place as the radius ratio (R /R ) Is reduced but In a more localised form, prSbaBly due to the relatively large contact zone resulting from the low elastic modulus of the materials. These side lobes no longer contain the polnt(s) of minimum film thickness which remains on the semi-axis of the contact ellipse at the exit. 

The starting point for the investigation is the case of a collision of equal sized droplets with small off-set. Figure 1.19 shows such a collision of non-isoviscous droplets with a delayed coalescence. The relevant material parameters used in the simulation are summarized in Table 1.5. The computational domain has size 2 10 m X 2 10 m X 2 10 m with 256 x 256 x 128 cells using one symmetry plane. The mesh resolution of the droplets is 90 ceUs/Do. Differences of density and surface tension of the droplets are small and not considered in this work, so the arithmetic mean of the measured values is used in the simulation. This yields a deviation of 2.2 % in the density and 4.4 % in the surface tension. In the simulation, the surface tension algorithm is switched from separate droplets to standard treatment at tdeiay = 584 ps. 

In [4], Notary and Lubrecht studied the starvation behaviour of the rigid isoviscous elliptical contact. They gave a more accurate approximation of the starvation curve using a fraction of two polynomials. However, the improved precision is obtained at the cost of a dozen constants. It is unlikely that a simpler relation can be found for the piezoviscous-elastic (EHL) starvation curve. Hence we will stick with equation (l)in spite of its mediocre performance to approximate the oil ejection in all the starved regime. The rest of this paper will treat the points 2 and 3. 

C.P. Bosnyak (Dow Chemical Company, Midland, Michigan) I think another interesting point is that it appears as a very sharp transition effect, a very sharp exotherm, and this is then obviously specific to a temperature. I don t know whether this refers to a Ty temperature, or a sort of isoviscous state, or where chains just simply reach a certain energy level where they re able to revert back to their unoriented state. Do you know the answer to this ... 

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