Drag coefficients for sphers in high reynolds number flow of dilute solutions of high polymers

blunt slider is used. This causw “pile-up” of material along ( I i 0) directions (as previously obscrvcd in copper crystals) but it does not product any appreciabIc anisotropy in the friction. The Friction of Clean Crysral Surfaces. I;. P. Rowden and A. E. Hanwell, Pvoc. Roy. Sot. (Lowdon), Ser. -4, 295 (1g66) 233-243; ro figs., 23 refs. A study is made of the frictional behaviour of crystals (diamond, magnesium oxide, sapphire) sliding on themselves in high vacuum (10-10 torr). The surface films normally present on these crystals are very tenacious but they may be worn away by repeated sliding in the same track. finder these conditions the friction of the clean crystals may increase by a factor of ten so that the coefficient of friction may rise to Jew I. The frictional rise is limited because of the elastic and brittle behaviour of the contact regions. Under these conditions subsurface deformation and fracture of the crystal occurs and this, combined with the high surface adhesion, causes pronounced wear. Adsorption of a few molecular layers of gas can again reduce the friction to a low value. The results are relevant to the operation of bearings and to the wear of surfaces in space. Mechanism of Rollins in Force Contact of Elastic Bodies. S. V. Pinegin, Tvam. ASME, 88 D (J. Basic Elag.), (I) (1966) 269-272; (Source: Appl. Meek. Rev., 19 (9) (1966) 763.) Experiments have been carried out to detern&c the displacements and strains in the extreme surface layer of the region of contact due to rolling of a ball on a block. These strains, which pIay a significant role in the surface destruction phenomenon, are compared with previously determined theoretical values. Good agreement is obtained and discrepancies are accounted for. Spontaneous Conversion of Sliding Friction to Rolling Friction inHigh-temperature Tests on Refractory Carbides. A. P. Semenov and V. V. Pozdnyakov, Soviet IO (L) (1965) rho-162. Phys.-Doklady, (Translation of Dokladv Akad. Nauk SSSR. ;60 (5) (1965) x05711060 by American Institute of Phvsics. New York, N.Y.) For abstract see A$. Mech. Rev., ;g (IO) (1966) 91.5. Directional Deformation During Friction in Rocksalt. V. D. Evdokimov, Soviet Phys.-Doklady, IO ~rrj-1115. (Translated from (11) (w66) Doklady Akad. Nauk SSSR, r65 (3) (1965) 545-547 by American Institute of Physics, Inc., New York, N.Y.) Wear,

IO

(1967) 245-259

Friction Reduction as an Estimator of Molecular Weight. J. ii:. Hoyt, ,/. I”‘olymc~~ Scz., Pt. B, Polyww~ Lefters, 4 (10) (1966) 713~m7r6; j figs., r tablt:, 7 rrfs. &car, high-molecular-weight polymers mudifv the turbulent friction characteristics of their solvents and this property can be used to estimate their molecular \veight. Drag Coefficients for Spheres in High Reynolds Number Flow of Dilute Solutions of High Polymers. II. .2. White, ;V&uw, ,218 (5059) (r966) ~77.-278; I fig., I table, 5 refs. 3. LUBJIICrlTlON 3.1.

AND LIJBRICANTS

Llrbrication

BOOK : Elasto*hydrodyna~~ Lubrication : The Fundamentals of RolIer and Gear Lubrication. II. Uowson and G. Ii. Higginson, published by I’ergamon Press, Oxford, 1966; 235 pp. Uoth theoretical and experimental studies are made of hydrodynamic lubrication of gears and rolling-contact bearings. Lubrication of rigid cylinders, film thickness in highly-loaded rigid contacts, a comparison of theory and experiment, and apparatus and measurements of film thickness and shape are some of the points considered by the authors. A bibliography of over roe items is included. On Hydrodynamic Lubrication with Special Reference to Sub-cavity Pressures and Number of Streamers in Cavitation Regions. L. Floberg, Acta Polytech. Stand., Mech. Eng. Sep., I9 (1965) 34 PP. For abstract see APpI. ~Wiicl~.Keo., ry (IO) (rgG6) grG. A Theory of Liquid-Solid Hydrodynamic Film Lubrication. H. G. Rylander, ASLE TWMS., 9 (r966f 264-271.

This investigation was undertaken for the purpose of e&ending the design theories for hydrodynamic bearings to include the effects of solid particles in a liquid base lubricant. _t set of nonlinear, coupled partial differential equations is developed to include the effects of the solid particles. Solutions of the mathematical model by numerical analysis are compared to the results obtained in actual bearing tests with a universal bearing test machine. Increased friction from the solids is shown to be limited to a certain range of operation such that at Sommerfeld numbers above or below this range there is only a slight increase in the friction above that obtained with the liquid alone. Good agreement