- Email: [email protected]
A proposed mechanism for ice friction
SYSTEMATIC ABSTRACTS Adhesion of Metal Films to Glass. P. Benjamin and C. Weaver. Royal Society, Proceedings, v. 254, ser. A, Feb. 9, 1960, p. 177-183. The adhesion of metal films produced by vacuum evaporation has been measured by drawing a smoothly rounded chrome-steel point across the surface and gradually increasing the load on the point until the film was removed. Results are presented for Au, Fe, and Al. Zur Physik des Haftens fester Kijrper. The Physics of Adhesion of Solid Bodies. H. Krupp, G. Sandstede and K.-H. Schramm. Chemie-Ingenieur-Tech&k, v. 32, February, 1960, pp. 99-105. The nature of dispersion forces as one of the main causes df adhesion processes is explained and using a very simple model the magnitude of the adhesion forces is estimated. Further, the possibilities for improvement of the model employed are indicated so that the influence of the molecular structure of the boundary surface can be taken into account. Elastic Contact of Rough Surfaces. (in Russian) N. B. Demkin. Izvestiia Vysshikh Uchebnykh Zavedenii, Mashinostroenie, 1959, no. 6, p. 44-51. Models of the surfaces are obtained by means of a collection of spherical projections with an absolutely smooth hard surface. The model selected is connected with the bearing curves of real surfaces. Calculation reveals the relationships expressing the actual area of contact and-the ;pproacIh through the geometry of the surfaces and the mechanical properties of the material. (See also Wear, 3 (1960) 170.) 2.2.
Friction
LOW Friction of Metals in Reciprocating Sliding. Yasukatsu Tamai. Journal of Applied Physics, v. 30, Dec. 1959, p. 1874-1875. A very low friction, about 10-2, has been unexpectedly observed in reciprocating sliding with Au, Ag, Cu, and Pt. It was found that the characteristics common to those metals were soft metal substrate and no surface oxide or soft oxide. Hysteresis Losses in the Friction of Lubricated Rubber. David Tabor. Rubber Chemistry and Technology, V. 33, no. I, Jan.-Mar. 1960, p. 142-150. (Reprinted from the Proceedings of the First International Skid Prevention Conference, Virginia Council of Highway Investigation and Research, Charlottesville, Va., 1959, p. 211-218.)
Resistance to sliding on wet or slippery road surfaces may be considerably increased by
405
using a tire rubber which maintains a high hysteretic loss over the range of speeds and temperatures developed during operation. In order to reduce the tendency to overheat, a duplex structure is suggested in which the body of the tire has low losses while the tread has high losses. A Proposed Mechanism for Ice Friction. C. D. Niven, National Research Council, Ottawa. Can. J. Phys., v. 37, 1959, p.247; (I fig., 14 ref.) The collapsible structure of ice is stressed. The adhesion bond is visualized as being associated with a readjustment of a partially collapsed or distorted molecular structure when cooling sets in after plastic flow has occurred in the asperity. With this general idea in view the friction mechanism on ice is compared in detail with that on a non-collapsible material, and explanations for observations are suggested. The Effect of High Loading on the Kinetic Friction of Ice. C. D. Niven, National Research Council, Ottawa. Can. J. Phys., v. 32, 1954, p. 782789; (5 fig., 9 ref.) The kinetic friction of stainless steel on ice decreased very markedly at high loadings of 30 to 50 kg/cmz. This constituted a violation of Amontons’ law. At low loading the material of a slider is of far greater importance than at higli loading, which suggests that in the explanation of the friction of ice at least two important factors are involved, which are related respectively to (a) pressure and (b) adhesion. Rolling Friction of Polymeric Materials. I. Elastomers. Donald G. Flom, J. Appl. Phys., v. 31, no. 2, 1960, p. 306-314; (17 fig., I table, 2g ref.) Coefficients of friction for the rolling of steel balls on butyl, silicone and Neoprene elastomers have been measured in the temperature range of 25 to IOO’C. For equivalent amounts of deformation, rolling friction is directly proportional to dynamic mechanical losses measured by a rebound method. In addition, the coefficients of friction vary directly with (load) ~3 and inversely with (ball radius) 218.These results are in agreement with recent theoretical predictions. The high mechanical losses and rolling friction for the butyl elastomer at 25’C drop sharply on increasing the temperature to IOO”C. For the silicone and the Neoprene the losses and the friction decrease only slightly with increase in temperature. Investigation of Tandem-Wheel and AirJet Arrangements for Improving Braking Friction on Wet Surfaces. Eziaslav N. Harrin. NASA Technical Note Wear, 3 (1960) 404-409
Friction
LOW Friction of Metals in Reciprocating Sliding. Yasukatsu Tamai. Journal of Applied Physics, v. 30, Dec. 1959, p. 1874-1875. A very low friction, about 10-2, has been unexpectedly observed in reciprocating sliding with Au, Ag, Cu, and Pt. It was found that the characteristics common to those metals were soft metal substrate and no surface oxide or soft oxide. Hysteresis Losses in the Friction of Lubricated Rubber. David Tabor. Rubber Chemistry and Technology, V. 33, no. I, Jan.-Mar. 1960, p. 142-150. (Reprinted from the Proceedings of the First International Skid Prevention Conference, Virginia Council of Highway Investigation and Research, Charlottesville, Va., 1959, p. 211-218.)
Resistance to sliding on wet or slippery road surfaces may be considerably increased by
405
using a tire rubber which maintains a high hysteretic loss over the range of speeds and temperatures developed during operation. In order to reduce the tendency to overheat, a duplex structure is suggested in which the body of the tire has low losses while the tread has high losses. A Proposed Mechanism for Ice Friction. C. D. Niven, National Research Council, Ottawa. Can. J. Phys., v. 37, 1959, p.247; (I fig., 14 ref.) The collapsible structure of ice is stressed. The adhesion bond is visualized as being associated with a readjustment of a partially collapsed or distorted molecular structure when cooling sets in after plastic flow has occurred in the asperity. With this general idea in view the friction mechanism on ice is compared in detail with that on a non-collapsible material, and explanations for observations are suggested. The Effect of High Loading on the Kinetic Friction of Ice. C. D. Niven, National Research Council, Ottawa. Can. J. Phys., v. 32, 1954, p. 782789; (5 fig., 9 ref.) The kinetic friction of stainless steel on ice decreased very markedly at high loadings of 30 to 50 kg/cmz. This constituted a violation of Amontons’ law. At low loading the material of a slider is of far greater importance than at higli loading, which suggests that in the explanation of the friction of ice at least two important factors are involved, which are related respectively to (a) pressure and (b) adhesion. Rolling Friction of Polymeric Materials. I. Elastomers. Donald G. Flom, J. Appl. Phys., v. 31, no. 2, 1960, p. 306-314; (17 fig., I table, 2g ref.) Coefficients of friction for the rolling of steel balls on butyl, silicone and Neoprene elastomers have been measured in the temperature range of 25 to IOO’C. For equivalent amounts of deformation, rolling friction is directly proportional to dynamic mechanical losses measured by a rebound method. In addition, the coefficients of friction vary directly with (load) ~3 and inversely with (ball radius) 218.These results are in agreement with recent theoretical predictions. The high mechanical losses and rolling friction for the butyl elastomer at 25’C drop sharply on increasing the temperature to IOO”C. For the silicone and the Neoprene the losses and the friction decrease only slightly with increase in temperature. Investigation of Tandem-Wheel and AirJet Arrangements for Improving Braking Friction on Wet Surfaces. Eziaslav N. Harrin. NASA Technical Note Wear, 3 (1960) 404-409