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Study of external friction of polymers at transition from the highly elastic to the vitreous state
DAWIHL, W. and FRISCH, B. Wear properties of tungsten carbide and aluminium oxide sintered materials Wear,Vol 12,No 1 (July 1968) pp 1’7-25 Results obtained so far from investigations on the wear mechanism of sintered materials on tungsten carbide or aluminium oxide suggest that the wear of these materials is determined by impact loading and temperature-dependent welding phenomena. At high temperature, healing processes occur which markedly increase the mechanical resistance of both types of material and reduce their wear accordingly. It is assumed that healing processes lead to the relief of internal stresses of the second kind. It was also established that the wear of aluminium oxide is determined by mechanochemical processes. Salts of aluminium oxide are formed in the presence of organic acids used as surface,-active media. (5 figures, 3 tables, 26 references) (Tribology 1968, abstract 151)
DAWIHL, W. and KLINGLER, E. The influence of lcold-welding’ between metals and sintered alumina on their wear resistance Wear, Vol 11, No 6 (June 1968) pp 461-470 The well-known equation for wear is based mainly on the size of the real area of contact. Studies of the ‘cold-welding’ between test pieces of sintered alumina and steel, copper and brass have shown that the welding is influenced by specific reactions between the areas in contact and that ‘cold-welding’ begins only above a certain temperature range (the ‘adherence temperature’). Inasmuch as the wear of sintered alumina depends on welding influences, its superior quality (as compared with cemented carbides) is determined by its higher adherence temperature and the protection of welded metallic films. It is suggested that the welding of alumina to metals is based on oxygen atoms forming ‘bridges’ between oxide and metal. (2 figures, 5 tables, 12 references) (Tribology 1968, abstract 152)
EARLES,S. W. E. and POWELL,D. G. Surface temperature and its relation to periodic changes in sliding conditions between unlubricated steel surfaces Transactions of the American Society of Lubrication Engineers, Vol 11, No 2 (April 1968) pp 109-120 Periodic changes were previously reported in the frictional force and wear rate in unlubricated sliding between SAE 1113 steel surfaces. Moreover, the steady-state value of the coefficient of friction and the periodic time of surface breakdown were observed to be continuous functions of (normal 1oad)l’a x (sliding speed) = W1’aU. Theory predicts that the increase in temperature at the contacting asperities should vary with the coefficient of friction, and should be a function of the above product. Temperatures were measured using both microhardness and coaxial thermocouple techniques. In the steady-state the bulk surface temperature was found to be a continuous function of (Wi’sU). It was found that the bulk surface temperature rises rapidly during surface breakdowns, because of a sudden increase in the coefficient of friction. It is concluded that this temperature increase promotes the formation of a new oxide surface layer and the return to steady state conditions. (10 figures, 1 table, 18 references) (Tribology 1968, abstract 153)
EL’KIN, A. I. Stndy of external friction of polymers at transition from the highly elastic to the vitreous state Friction and Wear in Machinery, Vol 19 (1965) This article deals with the frictional properties of highly elastic polymers in the temperature range including the highly elastic and vitreous states. (11 references, 8 figures) (Tribology 1968, abstract 154) 252
TRIBOLOGY
November
1968
ESHEL, A. and WILDMANN, M. Dynamic behaviour of a foil in the presence of a lubricating film Transactions of the American Society of Mechanical Engineers, Journal of Applied Mechanics, Vol 35, Series E, No 2 (June 1968) pp 242-247 Equations for the oscillation of a foil over a lubricating fluid film are derived and are then simplified by a smallparameter expansion. A few particular cases are discussed. A linearised solution is obtained for the case of a massless, perfectly flexible foil moving over an incompressible film. The solution reveals the interesting phenomenon that small disturbances in the film thickness, as well as symmetrical large disturbances, propagate at a speed U/2, where U is the foil speed. (Tribology 1968, abstract 155) FINKIN, E. F. The sliding of copper-based sintered material against steel in paraffin mineral oil Wear, Vol 11, No 5 (May 1968) pp 341-353 The arrangement was similar to an automobile clutch unit. Surface temperature, oil temperature, load and friction were measured. The coefficient of friction under constant load and the velocity were determined. Reproducible levels of constant value were obtained as a function of temperature, decreasing with increasing temperature. Conclusion: chemical reactions are chiefly responsible. (Tribology 1968, abstract 156) GILTROW, J. P. and LANCASTER, J. K. Friction and wear properties of carbon fibre-reinforced metals Wear, Vol 12, No 2 (August 1968) pp 91-105 Composites of randomly oriented, chopped carbon fibres in lead, silver, copper, nickel and cobalt were prepared by powder metallurgical techniques, with fibre contents up to 25 vol “/,. The most satisfactory method of fabrication was hot-pressing of fibres precoated with metal by electrodeless deposition. Rates of wear of the composites, measured at room temperature during sliding against tool steel with and without lubrication, were appreciably lower than those of the parent metals. The coefficients of friction were not reduced, however, nor were the wear rates at elevated temperatures (4’70°C). It is concluded that the carbon fibres function by facilitating the development of a strengthened surface layer during sliding. The fibres do not appear to improve the bulk mechanical properties. Possible reasons for this are discussed. (8 figures, 4 tables, 13 references) (Tribology 1968, abstract 157) HARRIS, C. L., READ, J. E. and THOMPSON, J. B. Friction and wear performance of soft metal film lubricants in air and vacuum to lo-lo torr Lubrication Engineering, Vol24, No 5 (May 1968) pp 230-237 A full description of the apparatus and techniques used is given. The sliding experiments were conducted at speeds from l-230cm/s, using a s&in diameter hemispherically ended rider loaded with a force of 1Ogm against the face of a flat rotating disc specimen li/,in diameter. The effects of film application techniques, and comparative performance in both air and ultra-high vacuum were studied. Electrodeposited films of lead were shown to be effective in reducing both wear and friction of tool-steel sliding surfaces in vacuum. The performance of lead as a lubricant was found to be significantly better in vacuum than in air. (8 references, 11 figures, 1 table) (Tribology 1968, abstract 158) HARRIS, C. L., READ, J. E. and THOMPSON, J. B. Lubrication in space vacuum. Part 3-Life Test Evaluation of ba.ll bearings lubricated with oils and greases Lubrication Engineering, Vol 24, No 4 (April 1968) pp 182-188 Oil and grease lubrication of small ball bearings is discussed. Life tests were performed on a number of lubricants and bearing types operating in small, 3000rev/min induction motors at 10-7-10-s torr, and torque and life results are presented. Over 7000hr continuous operation has been achieved in many tests, which are currently still running. The effects of lubricant reservoirs, bearing load and motor component degassing have all been included as test parameters. (5 references, 6 figures, 5 tables) (Tribology 1968, abstract 159)
DAWIHL, W. and KLINGLER, E. The influence of lcold-welding’ between metals and sintered alumina on their wear resistance Wear, Vol 11, No 6 (June 1968) pp 461-470 The well-known equation for wear is based mainly on the size of the real area of contact. Studies of the ‘cold-welding’ between test pieces of sintered alumina and steel, copper and brass have shown that the welding is influenced by specific reactions between the areas in contact and that ‘cold-welding’ begins only above a certain temperature range (the ‘adherence temperature’). Inasmuch as the wear of sintered alumina depends on welding influences, its superior quality (as compared with cemented carbides) is determined by its higher adherence temperature and the protection of welded metallic films. It is suggested that the welding of alumina to metals is based on oxygen atoms forming ‘bridges’ between oxide and metal. (2 figures, 5 tables, 12 references) (Tribology 1968, abstract 152)
EARLES,S. W. E. and POWELL,D. G. Surface temperature and its relation to periodic changes in sliding conditions between unlubricated steel surfaces Transactions of the American Society of Lubrication Engineers, Vol 11, No 2 (April 1968) pp 109-120 Periodic changes were previously reported in the frictional force and wear rate in unlubricated sliding between SAE 1113 steel surfaces. Moreover, the steady-state value of the coefficient of friction and the periodic time of surface breakdown were observed to be continuous functions of (normal 1oad)l’a x (sliding speed) = W1’aU. Theory predicts that the increase in temperature at the contacting asperities should vary with the coefficient of friction, and should be a function of the above product. Temperatures were measured using both microhardness and coaxial thermocouple techniques. In the steady-state the bulk surface temperature was found to be a continuous function of (Wi’sU). It was found that the bulk surface temperature rises rapidly during surface breakdowns, because of a sudden increase in the coefficient of friction. It is concluded that this temperature increase promotes the formation of a new oxide surface layer and the return to steady state conditions. (10 figures, 1 table, 18 references) (Tribology 1968, abstract 153)
EL’KIN, A. I. Stndy of external friction of polymers at transition from the highly elastic to the vitreous state Friction and Wear in Machinery, Vol 19 (1965) This article deals with the frictional properties of highly elastic polymers in the temperature range including the highly elastic and vitreous states. (11 references, 8 figures) (Tribology 1968, abstract 154) 252
TRIBOLOGY
November
1968
ESHEL, A. and WILDMANN, M. Dynamic behaviour of a foil in the presence of a lubricating film Transactions of the American Society of Mechanical Engineers, Journal of Applied Mechanics, Vol 35, Series E, No 2 (June 1968) pp 242-247 Equations for the oscillation of a foil over a lubricating fluid film are derived and are then simplified by a smallparameter expansion. A few particular cases are discussed. A linearised solution is obtained for the case of a massless, perfectly flexible foil moving over an incompressible film. The solution reveals the interesting phenomenon that small disturbances in the film thickness, as well as symmetrical large disturbances, propagate at a speed U/2, where U is the foil speed. (Tribology 1968, abstract 155) FINKIN, E. F. The sliding of copper-based sintered material against steel in paraffin mineral oil Wear, Vol 11, No 5 (May 1968) pp 341-353 The arrangement was similar to an automobile clutch unit. Surface temperature, oil temperature, load and friction were measured. The coefficient of friction under constant load and the velocity were determined. Reproducible levels of constant value were obtained as a function of temperature, decreasing with increasing temperature. Conclusion: chemical reactions are chiefly responsible. (Tribology 1968, abstract 156) GILTROW, J. P. and LANCASTER, J. K. Friction and wear properties of carbon fibre-reinforced metals Wear, Vol 12, No 2 (August 1968) pp 91-105 Composites of randomly oriented, chopped carbon fibres in lead, silver, copper, nickel and cobalt were prepared by powder metallurgical techniques, with fibre contents up to 25 vol “/,. The most satisfactory method of fabrication was hot-pressing of fibres precoated with metal by electrodeless deposition. Rates of wear of the composites, measured at room temperature during sliding against tool steel with and without lubrication, were appreciably lower than those of the parent metals. The coefficients of friction were not reduced, however, nor were the wear rates at elevated temperatures (4’70°C). It is concluded that the carbon fibres function by facilitating the development of a strengthened surface layer during sliding. The fibres do not appear to improve the bulk mechanical properties. Possible reasons for this are discussed. (8 figures, 4 tables, 13 references) (Tribology 1968, abstract 157) HARRIS, C. L., READ, J. E. and THOMPSON, J. B. Friction and wear performance of soft metal film lubricants in air and vacuum to lo-lo torr Lubrication Engineering, Vol24, No 5 (May 1968) pp 230-237 A full description of the apparatus and techniques used is given. The sliding experiments were conducted at speeds from l-230cm/s, using a s&in diameter hemispherically ended rider loaded with a force of 1Ogm against the face of a flat rotating disc specimen li/,in diameter. The effects of film application techniques, and comparative performance in both air and ultra-high vacuum were studied. Electrodeposited films of lead were shown to be effective in reducing both wear and friction of tool-steel sliding surfaces in vacuum. The performance of lead as a lubricant was found to be significantly better in vacuum than in air. (8 references, 11 figures, 1 table) (Tribology 1968, abstract 158) HARRIS, C. L., READ, J. E. and THOMPSON, J. B. Lubrication in space vacuum. Part 3-Life Test Evaluation of ba.ll bearings lubricated with oils and greases Lubrication Engineering, Vol 24, No 4 (April 1968) pp 182-188 Oil and grease lubrication of small ball bearings is discussed. Life tests were performed on a number of lubricants and bearing types operating in small, 3000rev/min induction motors at 10-7-10-s torr, and torque and life results are presented. Over 7000hr continuous operation has been achieved in many tests, which are currently still running. The effects of lubricant reservoirs, bearing load and motor component degassing have all been included as test parameters. (5 references, 6 figures, 5 tables) (Tribology 1968, abstract 159)