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Influence of temperature on boundary lubrication
SYSTEMATIC
the length of life cycle to that of the vertical force component is not sensitive to the presence of lubricants in cases where the cone tips are in line or nearly in line with the direction of relative motion: but the ratio is substantially lowered in the presence of lubricants when the cone tips are far from being in line with the direction of relative motion. The former cases are always accompanied by the formation of macroscopic wear debris. (2) By increasing the internal angle of cones, the ratio defined above is decreased, but its value does not seem to approach zero for the angle approaching IBOO, a flat surface. (3) Size effect as discussed by Morrison and Shaw is evidenced in this experiment. The mutual inclusiveness of the classical interlock theory and the popular adhesion theory of friction is discussed. Moreover, the coefficient of friction for a pair of idealized surfaces with asperities in the form of go’ cones and randomly distributed is calculated from a considerable amount of test data. While actual surfaces have asperities roughly in the form of cones with internal angles much larger than go’. right circular cones were used, nevertheless, for simplicity and for amplifying the effects noted. Methods of Predicting Laminar Heat Rates on Hypersonic Vehicles. Richard J. Wisniewski. NASA Technical
ABSTRACTS
249
Note D-201, December 1959. 36 pp., diagrs. OTS price, $I .oo. A summary of some of the simplest and best available laminar heat-transfer theories for flow in thermodynamic equilibrium is presented. In some cases the effects of frozen flow are included. Emphasis is placed on the proper methods of obtaining heating rates to hypersonic bodies, wings, and control surfaces. The effects of yaw and the determination of the inviscid flow field are also considered. The Determination of Local Turbulent Skin Friction from Observations in the Viscous Sub-Layer. P. Bradshaw and N. Gregory. Aeronautical Research Council (Gt. Brit.), March 26, 1959. 20 pp., diagrs. ARC 20,895; FM 2802; Perf. 1753. (Ask for N-77424*) Observations made in the viscous sublayer of turbulent shear flows with small surface pitot tubes and hot wires show that such instruments give accurate values of boundary-layer skin friction, at least in zero pressure gradient, but only when calibrated in turbulent flow; calibration in laminar flow gives incorrect results. It is further shown that the region of universality of turbulent velocity profile is confined to the viscous sublayer and an upper limit u,d/v = 30 is suggested for the height d of a surface tube if reasonable accuracy is to be obtained in skin friction measurements.
3. LUBRICATIONAND LUBRICANTS Transition Temperatures in Sliding Systems. R. S. Fein, C. N. Rowe, K. L. Kreuz. ASLE Transactions, v. 2 no. 1, 1959, p. 50-57; 13 fig., 5 tables, 18 ref. A pin-on-disk type of apparatus is used to study the effect of operating variables on transition temperatures with dilute solutions of pure fatty acids in pure paraffinic hydrocarbons and with a straight paraffinic mineral oil. It is found that the temperature at which the sudden transition from low to high friction and wear occurs increases with sliding speed, decreases with load, and is otherwise independent of operating variables. Empirically, the reciprocal of the absolute transition temperature varies linearly with the logarithm of the ratio of load to speed. The absence of conventional hydrodynamic lubrication in this system is demonstrated.
Influence of Temperature on Boundary Lu* brication C. W. Cowley, C. J. Ultee, and C. W. West. ASLE Transactions, v. I, no. 2, 1958, p. 281286; 8 fig., 5 tables, r7 ref. The effects of temperature on the lubricity of a number of lubricants are studied. An apparatus designed to study lubricants under boundary conditions, with provisions for varying temperature, load, and speed, is described. Sharp transitions from smooth sliding to severe galling and seizure are observed at a specific temperature whichis characteristic of the lubricant and the test conditions. These “failure temperatures” are useful in understanding the lubrication lubricant mechanism and in predicting performance.
4. BEARINGS A Theoretical Study of the Effect of Offset Loads on the Performance of a 120’ Partial Journal Bearing. A. A. Raimondi. ASLE Transactions, v. 2, no. 1, 1959, p. 147-157; 20 fig., I table, 15 ref. Reynold’s equation for a 120~ partial journal
bearing of the clearance type having an L/D ratio of 1 is solved numerically to determine the effect of positioning circumferentially the line of action of the load at various points along the bearing arc. The influence of the load position (a/B) on film Weav, 3 (1960) 249
the length of life cycle to that of the vertical force component is not sensitive to the presence of lubricants in cases where the cone tips are in line or nearly in line with the direction of relative motion: but the ratio is substantially lowered in the presence of lubricants when the cone tips are far from being in line with the direction of relative motion. The former cases are always accompanied by the formation of macroscopic wear debris. (2) By increasing the internal angle of cones, the ratio defined above is decreased, but its value does not seem to approach zero for the angle approaching IBOO, a flat surface. (3) Size effect as discussed by Morrison and Shaw is evidenced in this experiment. The mutual inclusiveness of the classical interlock theory and the popular adhesion theory of friction is discussed. Moreover, the coefficient of friction for a pair of idealized surfaces with asperities in the form of go’ cones and randomly distributed is calculated from a considerable amount of test data. While actual surfaces have asperities roughly in the form of cones with internal angles much larger than go’. right circular cones were used, nevertheless, for simplicity and for amplifying the effects noted. Methods of Predicting Laminar Heat Rates on Hypersonic Vehicles. Richard J. Wisniewski. NASA Technical
ABSTRACTS
249
Note D-201, December 1959. 36 pp., diagrs. OTS price, $I .oo. A summary of some of the simplest and best available laminar heat-transfer theories for flow in thermodynamic equilibrium is presented. In some cases the effects of frozen flow are included. Emphasis is placed on the proper methods of obtaining heating rates to hypersonic bodies, wings, and control surfaces. The effects of yaw and the determination of the inviscid flow field are also considered. The Determination of Local Turbulent Skin Friction from Observations in the Viscous Sub-Layer. P. Bradshaw and N. Gregory. Aeronautical Research Council (Gt. Brit.), March 26, 1959. 20 pp., diagrs. ARC 20,895; FM 2802; Perf. 1753. (Ask for N-77424*) Observations made in the viscous sublayer of turbulent shear flows with small surface pitot tubes and hot wires show that such instruments give accurate values of boundary-layer skin friction, at least in zero pressure gradient, but only when calibrated in turbulent flow; calibration in laminar flow gives incorrect results. It is further shown that the region of universality of turbulent velocity profile is confined to the viscous sublayer and an upper limit u,d/v = 30 is suggested for the height d of a surface tube if reasonable accuracy is to be obtained in skin friction measurements.
3. LUBRICATIONAND LUBRICANTS Transition Temperatures in Sliding Systems. R. S. Fein, C. N. Rowe, K. L. Kreuz. ASLE Transactions, v. 2 no. 1, 1959, p. 50-57; 13 fig., 5 tables, 18 ref. A pin-on-disk type of apparatus is used to study the effect of operating variables on transition temperatures with dilute solutions of pure fatty acids in pure paraffinic hydrocarbons and with a straight paraffinic mineral oil. It is found that the temperature at which the sudden transition from low to high friction and wear occurs increases with sliding speed, decreases with load, and is otherwise independent of operating variables. Empirically, the reciprocal of the absolute transition temperature varies linearly with the logarithm of the ratio of load to speed. The absence of conventional hydrodynamic lubrication in this system is demonstrated.
Influence of Temperature on Boundary Lu* brication C. W. Cowley, C. J. Ultee, and C. W. West. ASLE Transactions, v. I, no. 2, 1958, p. 281286; 8 fig., 5 tables, r7 ref. The effects of temperature on the lubricity of a number of lubricants are studied. An apparatus designed to study lubricants under boundary conditions, with provisions for varying temperature, load, and speed, is described. Sharp transitions from smooth sliding to severe galling and seizure are observed at a specific temperature whichis characteristic of the lubricant and the test conditions. These “failure temperatures” are useful in understanding the lubrication lubricant mechanism and in predicting performance.
4. BEARINGS A Theoretical Study of the Effect of Offset Loads on the Performance of a 120’ Partial Journal Bearing. A. A. Raimondi. ASLE Transactions, v. 2, no. 1, 1959, p. 147-157; 20 fig., I table, 15 ref. Reynold’s equation for a 120~ partial journal
bearing of the clearance type having an L/D ratio of 1 is solved numerically to determine the effect of positioning circumferentially the line of action of the load at various points along the bearing arc. The influence of the load position (a/B) on film Weav, 3 (1960) 249