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Effects of thermal degradation on the lubrication properties of fluids
HERREBRUGH, K. Solving the incompressible and isothermal problem in elastohydrodynamic lubrication through an integral equation. Transactions of the American Society of Mechanical Engineers, Journal of Lubrication Technology, Vol 90, Series F, No 1 (January 1968) ~262 It is shown that the hydrodynamic and elasticity equation in elastohydrodynamic lubrication can be coupled to one single integral equation of the form H(x) = f(x) - T Lb K(x, [)F{H([)]
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in which f(x) and K(x, 4) are known analytic functions inside [a, b], and F(H) is in general a nonlinear function of the dimensionless film thickness. A numerical solution of this integral equation for constant viscosity is presented for a large range of loading conditions. (Tribology 1968, abstract 64)
HERSHEY, L. E. Time rate of wear testing mechanical seal carbons. Lubrication Engineering, Vol 24, No 1, (January 1968) ~27 This paper discusses a relatively short-time test for mechanical seal carbons which indicates long-term wear results to be expected. A comparison is presented of the wear rate of carbon after a series of one-day tests and after a series of four-day tests of the same items. The results for a variety of different carbons against three different counterface materials are tabulated and discussed. It is shown that such short-time tests readily reveal differences in wear rates and that the type of counterface is an important factor in the wear rate of a specific carbon. (Tribology 1968, abstract 65)
KAUZLAVICH, J. J., WAVRIK, R. W. and FRIEDERICY, J.A. Spherical pivot bearing theory. Lubrication Engineering, Vol 24,No 1 (January 1968) p20 The previous literature on the theory of pivot bearings has neglected the effect of wear, although this type of bearing usually operates under boundary lubrication conditions. This study of a spherically tipped pivot rotating in a hemispherical seat shows that wear has a significant influence on performance characteristics, and must not be neglected in design. Theoretical results are presented for pivots with sxial loads. It is assumed that the pivot is unlubricated, and wear takes place according to the Archard wear law. (Tribology 1968, abstract 66)
KINGSBURY, E. P. Ball motion in angular contact bearings. Wear, Vol 11, No 1 (January 1968) ~41 The nature of the frictional forces and moments applied to an angular contact bearing ball are examined in terms of slip, pivoting, spin and precession. Experimental methods for determining these quantities are given, together with results which indicate that the ball is retainer-controlled for pivoting, and race-controlled for slip. (Tribology 1968, abstract 67)
LEMAR, R. L. Effects of thermal degradation on the lubrication properties of fluids. Transactions of the American Society of Lubrication Engineers, Vol 10, No 4 (OctoberDecember 1967) ~357 Fluids representative of nine chemical types of base stocks considered promising for use in high-temperature hydrauHc systems were examined for antiwear properties at 167”F, before and after exposure at 650°F and 750°F. Several mixtures of these fluids were similarly studied. Significant thermal effects on antiwear properties measured at 167°F were frequently found for the high-temperature base fluids and their mixtures after thermal stresses at 650°F and 750°F. Fluids which formed large amounts of volatile decomposition products often showed poorer sntiwear properties after thermal stress. The polysiloxane fluid appeared to have a protective effect on steel when this fluid was combined in mixtures with other fluids which were corrosive at high temperatures. The ester and silicate fluids were better lubricity additives for the unstressed polysiloxane than were the chlorinated biphenyl and phosphate fluids. Differences were noted between the 1 and 40Kg load wear test results as they monitored thermal effects on wear properties, and several fluids showed such effects most frequently at one of the two loads. (Tribology 1968, abstract 68)
LIGHT, L. An experimental study of elastohydrodynamic lubrication of foil bearings (Part l-Displacement in the central zone). Transactions of the American Society of Mechanical Engineers, Journal of Lubrication Technology, . Vol 90, Series F, No 1 (January 1968) p199 An elastic foil under tension is wrapped partly around a rotating cylinder and is supported on a thin film of air. Capacitance probes, coincident with the surface of the cylinder, scan the air gap along the arc of wrap. The cylinder can be traversed across the width of the stationary foil, so that it is possible to determine the topography of the air gap from a series of circumferential scans. Experimental results are compared quantitatively with theoretical predictions for the perfectly flexible and for the elastic foil bearing of infinite width. A comparison is also made with theory, for the case when the angle of wrap is small and the entrance and exit transition zones merge. The effect of foil and gap width on side leakage is illustrated. The last part of this study deals with elastic foil bearings of finite width and with the characteristic ‘edge effect’ in particular. The influence of various parameters on the nature of the displacement field of foils is demonstrated and related to recent analyses. (Tribology 1968, abstract 69)
LITTMAN, W. E.,WIDNER, R. L., WOLFE, J. 0. and STOVER, J. D. The role of lhbrication in propagation of contact fatigue cracks. Transactions of the American Society of Mechanical Engineers, Journal of Lubrication Technology, Vol 90, Series F, No 1 (January 1968) p89 Comparative life tests of tapered roller bearings in mineral oils and synthetic fluids, Mil L-7808-F and Mil L-23699, demonstrate the strong influence of lubrication upon bearing life and failure characteristics. Failures originating at inclusions propagate very rapidly, and this mode takes on the macroscopic appearance of the point surface origin mode when fatigue cracks interact with a lubricant having low viscosity at the operating temperature. Observations indicate that bruises from debris in the lubricant are stress raisers of severity equivalent to non-metallic inclusions in bearing materials for nucleation of contact fatigue cracking. Surface fatigue by ‘peeling’ or superficial pitting can also act as the nucleus of fatigue cracks which propagate in the same manner as the point surface origin mode. In general, any surface stress concentration in combination with low lubricant film thickness promotes surface origin modes of contact fatigue, and low lubricant viscosity at the operating temperature promotes rapid propagation by a hydraulic pressure mechanism. (Tribology 1968, abstract 70) TRIBOLOGY
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1968
125
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in which f(x) and K(x, 4) are known analytic functions inside [a, b], and F(H) is in general a nonlinear function of the dimensionless film thickness. A numerical solution of this integral equation for constant viscosity is presented for a large range of loading conditions. (Tribology 1968, abstract 64)
HERSHEY, L. E. Time rate of wear testing mechanical seal carbons. Lubrication Engineering, Vol 24, No 1, (January 1968) ~27 This paper discusses a relatively short-time test for mechanical seal carbons which indicates long-term wear results to be expected. A comparison is presented of the wear rate of carbon after a series of one-day tests and after a series of four-day tests of the same items. The results for a variety of different carbons against three different counterface materials are tabulated and discussed. It is shown that such short-time tests readily reveal differences in wear rates and that the type of counterface is an important factor in the wear rate of a specific carbon. (Tribology 1968, abstract 65)
KAUZLAVICH, J. J., WAVRIK, R. W. and FRIEDERICY, J.A. Spherical pivot bearing theory. Lubrication Engineering, Vol 24,No 1 (January 1968) p20 The previous literature on the theory of pivot bearings has neglected the effect of wear, although this type of bearing usually operates under boundary lubrication conditions. This study of a spherically tipped pivot rotating in a hemispherical seat shows that wear has a significant influence on performance characteristics, and must not be neglected in design. Theoretical results are presented for pivots with sxial loads. It is assumed that the pivot is unlubricated, and wear takes place according to the Archard wear law. (Tribology 1968, abstract 66)
KINGSBURY, E. P. Ball motion in angular contact bearings. Wear, Vol 11, No 1 (January 1968) ~41 The nature of the frictional forces and moments applied to an angular contact bearing ball are examined in terms of slip, pivoting, spin and precession. Experimental methods for determining these quantities are given, together with results which indicate that the ball is retainer-controlled for pivoting, and race-controlled for slip. (Tribology 1968, abstract 67)
LEMAR, R. L. Effects of thermal degradation on the lubrication properties of fluids. Transactions of the American Society of Lubrication Engineers, Vol 10, No 4 (OctoberDecember 1967) ~357 Fluids representative of nine chemical types of base stocks considered promising for use in high-temperature hydrauHc systems were examined for antiwear properties at 167”F, before and after exposure at 650°F and 750°F. Several mixtures of these fluids were similarly studied. Significant thermal effects on antiwear properties measured at 167°F were frequently found for the high-temperature base fluids and their mixtures after thermal stresses at 650°F and 750°F. Fluids which formed large amounts of volatile decomposition products often showed poorer sntiwear properties after thermal stress. The polysiloxane fluid appeared to have a protective effect on steel when this fluid was combined in mixtures with other fluids which were corrosive at high temperatures. The ester and silicate fluids were better lubricity additives for the unstressed polysiloxane than were the chlorinated biphenyl and phosphate fluids. Differences were noted between the 1 and 40Kg load wear test results as they monitored thermal effects on wear properties, and several fluids showed such effects most frequently at one of the two loads. (Tribology 1968, abstract 68)
LIGHT, L. An experimental study of elastohydrodynamic lubrication of foil bearings (Part l-Displacement in the central zone). Transactions of the American Society of Mechanical Engineers, Journal of Lubrication Technology, . Vol 90, Series F, No 1 (January 1968) p199 An elastic foil under tension is wrapped partly around a rotating cylinder and is supported on a thin film of air. Capacitance probes, coincident with the surface of the cylinder, scan the air gap along the arc of wrap. The cylinder can be traversed across the width of the stationary foil, so that it is possible to determine the topography of the air gap from a series of circumferential scans. Experimental results are compared quantitatively with theoretical predictions for the perfectly flexible and for the elastic foil bearing of infinite width. A comparison is also made with theory, for the case when the angle of wrap is small and the entrance and exit transition zones merge. The effect of foil and gap width on side leakage is illustrated. The last part of this study deals with elastic foil bearings of finite width and with the characteristic ‘edge effect’ in particular. The influence of various parameters on the nature of the displacement field of foils is demonstrated and related to recent analyses. (Tribology 1968, abstract 69)
LITTMAN, W. E.,WIDNER, R. L., WOLFE, J. 0. and STOVER, J. D. The role of lhbrication in propagation of contact fatigue cracks. Transactions of the American Society of Mechanical Engineers, Journal of Lubrication Technology, Vol 90, Series F, No 1 (January 1968) p89 Comparative life tests of tapered roller bearings in mineral oils and synthetic fluids, Mil L-7808-F and Mil L-23699, demonstrate the strong influence of lubrication upon bearing life and failure characteristics. Failures originating at inclusions propagate very rapidly, and this mode takes on the macroscopic appearance of the point surface origin mode when fatigue cracks interact with a lubricant having low viscosity at the operating temperature. Observations indicate that bruises from debris in the lubricant are stress raisers of severity equivalent to non-metallic inclusions in bearing materials for nucleation of contact fatigue cracking. Surface fatigue by ‘peeling’ or superficial pitting can also act as the nucleus of fatigue cracks which propagate in the same manner as the point surface origin mode. In general, any surface stress concentration in combination with low lubricant film thickness promotes surface origin modes of contact fatigue, and low lubricant viscosity at the operating temperature promotes rapid propagation by a hydraulic pressure mechanism. (Tribology 1968, abstract 70) TRIBOLOGY
March
1968
125