Viscosity liquid metals

Liquid metal selection is usually limited to the lower melting point metals in Table 15. Figure 17 shows that Hquid metal viscosity generally is similar to water at room temperature and approaches the viscosities of gases at high temperature. Hydrodynamic load capacity with both Hquid metals and water in a bearing is about 1/10 of that with oil, as indicated in Table 2. 

The viscosities of liquid metals vaty by a factor of about 10 between the empty metals, and the full metals, and typical values are 0.54 x 10 poise for liquid potassium, and 4.1 x 10 poise for liquid copper, at dreir respective melting points. Empty metals are those in which the ionic radius is small compared to the metallic radius, and full metals are those in which the ionic radius is approximately the same as tire metallic radius. The process was described by Andrade as an activated process following an AiThenius expression... 

A furtlier empiiical expression, due to Andrade, for die viscosity of liquid metals at tlreir melting points, which agrees well with experimental data is... 

It follows that since the addition of metal oxides has such a profound effect on the properties of liquid silicates such as the viscosity, that the Reynolds number of liquid silicates in metal-silicate liquid two-phase systems will influence the boundary layer thickness to a greater extent than in the liquid metals and alloys, mainly because of the higher viscosity of the silicate. 

Glasses, like metals, are formed by deformation. Liquid metals have a low viscosity (about the same as that of water), and transform discontinuously to a solid when they are cast and cooled. The viscosity of glasses falls slowly and continuously as they are heated. Viscosity is defined in the way shown in Fig. 19.7. If a shear stress is applied to the hot glass, it shears at a shear strain rate 7. Then the viscosity, ij, is defined by... 

The viscosity coefficients at dislocation cores can be measured either from direct observations of dislocation motion, or from ultrasonic measurements of internal friction. Some directly measured viscosities for pure metals are given in Table 4.1. Viscosities can also be measured indirectly from internal friction studies. There is consistency between the two types of measurement, and they are all quite small, being 1-10% of the viscosities of liquid metals at their melting points. It may be concluded that hardnesses (flow stresses) of pure... 

Intrinsic resistance to dislocation motion can be measured in either of two ways direct measurements of individual dislocation velocities (Vreeland and Jassby, 1973) or by measurements of internal friction (Granato, 1968). In both cases, for pure simple metals there is little or no static barrier to motion. As a result of viscosity there is dynamic resistance, but the viscous drag coefficient is very small (10" to 10" Poise). This is only 0.1 to 1 percent of the viscosity of water (at STP) and about 1 percent of the viscosity of liquid metals at their... 

Silvery-white metal body-centered cubic crystals ductile soft and very hght (the fourth lightest metaUic element) Mobs hardness 0.3 density 1.522 g/cm3 at 18°C melts at 39.3°C density of the liquid metal 1.472 g/mL at 39°C vaporizes at 689°C producing a blue vapor vapor pressure 1 torr at 294°C and 10 torr at 387°C electrical resistivity 11.6 microhm-cm at 0°C and 13.1 mirohm-cm at 25°C viscosity 0.484 centipoise at 100°C magnetic susceptibility 0.09x10 cgs units at 18°C thermal neutron absorption cross section 0.73 barns reacts violently with water... 

Table 4.1 Comparison of Calculated [using Eq. (4.7) with PF = 0.45] and Experimental Values of Liquid Metal Viscosities Near Their Melting Points...

Liquid metal bums are known as projections from blast furnace tap or the situation of loading with delivery of bulk into liquid metal. Metal is normally of low viscosity like water and spreads on skin and eye. Thus projections of liquid metal do not behave like viscous materials but like water and spread their enormous heat onto wide areas. When eventually cooling down, liquid metal is trapped in the conjunctival sac. When this happens, there is a maximum heat transfer with high thermoconductivity from metallic surfaces to the conjunctiva with immediate water evaporation and consecutive heat transfer from the metal to the eye up to carbonization of the tissues [16,17],... 

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