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Dynamic characteristics of a hydrostatic thrust bearing
LITERATURE
AND CURRENT EVENTS
‘49
parameters are intended to stimulate interest in basic research in this area of solidstate lubrication.
um silicate which provided a strong binder for burnished molybdenum disulphide powder.
Solid Lubrication of Gears and Bearings in a Space Environment. P. H. Bowen, ASLE Trans., 7 (1964) 227; IO figs., 4 tables, 6 refs. Results of tests on both heavily-loaded gears of r2 DP and 35 mm bore ball bearings are reported. The gears and bearings were operated at unit compressive stresses up to I 13,000 p.s.i. and rgg,ooo p.s.i. respectively, at pressures from I . 10-6 to 7. IO-@torr and temperatures from -180 to 300’F. The lubrication technique for the gears and bearings made use of composite materials containing a metal matrix, a film former, and a load-carrying component.
Effect of Conventional Lubricants upon Resin-bonded Solid Film Lubricants. R. L. Young, Lubrication Eng., ao (6) (1964) 222-225; 3 tables, 4 refs. When a resin-bonded, solid film-lubricated surface is contaminated with conventional lubricants and the contaminant is not thoroughly removed, the wear life is generally lowered. Certain of the conventional lubricants lessen the corrosion protection while others have no significant effect on the corrosion protection afforded by solid film lubricants.
4. MACHINE PARTS (BEARINGS) Long-duration Lubrication Studies in Simulated Space Vacuum. R. D. Brown, R. A. Burton and P. M. Ku, ASLE Trans., 7 (1964) 326; g figs., r7 tables, r3 refs. Tests were made at low loads and moderate temperatures with sliders and ball bearings operating in test chambers each being continuously evacuated by an ion pump. The test chamber-ion pump system was used to simulate the loss of volatile matter from a bearing envelope through an opening to the space vacuum. Unlubricated specimens, MO&-based films, soft metal films, self-lubricating materials, and oil lubrication were evaluated. In the slider tests, low friction was obtained with several MoSz-based lubricants, with no evidence of lubricant failure in up to 460 days vacuum exposure. Wear was kept minimal, so as not to obscure vacuum exposure effects. A ball bearing with an epoxyMoSz composition retainer gave the best performance-low friction without evidence of malfunction for go0 million revolutions (420 days of vacuum exposure). Pressure measurements during tests indicated that volatile matter was released by the rubbing process. Dry-film Lubrication of Highly-loaded Bearings in Vacuum. E. C. McKannan and K. E. Demorest, LubriCat&Z .&&g., 20 (4) (1964) 134-141; 15 figs., 4 tables, 13 refs. Thirteen candidate dry-film lubricants were selected for testing on a small, single degree of freedom, gimbal simulation device. The two lubricants which provided the required combination of properties were: (a) a mixture of molybdenum disulphide, graphite and gold powders with a binder of sodium silicate which was capable of being sprayed with an air gun, and (b) a flame-sprayable coating of zirconi-
4.1. Calculations Dynamic Characteristics of a Hydrostatic Thrust Bearing. J. B. Hunt, Second Convention on Lubrication and Wear, rg64, Paper 17. To be published in the Proc. Inst. Mech. E+zgrs., London, 196411965; 6 figs., 5 refs. An earlier comprehensive application of the Navier-Stokes equations to the problem of the oscillatory loading of hydrostatic thrust bearings has been linearized, and shown experimentally to be true for ratios of vibration amplitude to oil film thickness not exceeding I/IO. From the resulting expressions, the stiffness and damping constant of an oil film can be readily found. Non-linear Modes of Vibration of a Rigid Rotor in Short Journal Bearings. N. J. Huggins, Second Convention on Lubrication and Wear, 1964, Paper 18. To be published in the Proc. inst. M&t. Engrs., London, r&/1965; 8 figs., 12 refs. An unusual analytical approach to oil whirl is presented. Instead of using linearized equations for the oil forces all the non-linear terms are retained. The complex equations are solved on an analogue computer, and the more important results are given which show the unusual vibration characteristics of an oil film. It is shown that self-sustained oscillations can exist and, with an exciting force, sub-harmonics are likely. Also the frequency of response may be a sub- or super-multiple of the exciting force. Ocvirk’s short bearing approximation is used as the basis of the analysis. It is recognized that it has certain deficiencies, and the results are therefore treated as indications and not as accurate predictions. Comparison with other theoretical and experimental work supports the validity of the present analysis. Wear, 8 (1965) 143-155
AND CURRENT EVENTS
‘49
parameters are intended to stimulate interest in basic research in this area of solidstate lubrication.
um silicate which provided a strong binder for burnished molybdenum disulphide powder.
Solid Lubrication of Gears and Bearings in a Space Environment. P. H. Bowen, ASLE Trans., 7 (1964) 227; IO figs., 4 tables, 6 refs. Results of tests on both heavily-loaded gears of r2 DP and 35 mm bore ball bearings are reported. The gears and bearings were operated at unit compressive stresses up to I 13,000 p.s.i. and rgg,ooo p.s.i. respectively, at pressures from I . 10-6 to 7. IO-@torr and temperatures from -180 to 300’F. The lubrication technique for the gears and bearings made use of composite materials containing a metal matrix, a film former, and a load-carrying component.
Effect of Conventional Lubricants upon Resin-bonded Solid Film Lubricants. R. L. Young, Lubrication Eng., ao (6) (1964) 222-225; 3 tables, 4 refs. When a resin-bonded, solid film-lubricated surface is contaminated with conventional lubricants and the contaminant is not thoroughly removed, the wear life is generally lowered. Certain of the conventional lubricants lessen the corrosion protection while others have no significant effect on the corrosion protection afforded by solid film lubricants.
4. MACHINE PARTS (BEARINGS) Long-duration Lubrication Studies in Simulated Space Vacuum. R. D. Brown, R. A. Burton and P. M. Ku, ASLE Trans., 7 (1964) 326; g figs., r7 tables, r3 refs. Tests were made at low loads and moderate temperatures with sliders and ball bearings operating in test chambers each being continuously evacuated by an ion pump. The test chamber-ion pump system was used to simulate the loss of volatile matter from a bearing envelope through an opening to the space vacuum. Unlubricated specimens, MO&-based films, soft metal films, self-lubricating materials, and oil lubrication were evaluated. In the slider tests, low friction was obtained with several MoSz-based lubricants, with no evidence of lubricant failure in up to 460 days vacuum exposure. Wear was kept minimal, so as not to obscure vacuum exposure effects. A ball bearing with an epoxyMoSz composition retainer gave the best performance-low friction without evidence of malfunction for go0 million revolutions (420 days of vacuum exposure). Pressure measurements during tests indicated that volatile matter was released by the rubbing process. Dry-film Lubrication of Highly-loaded Bearings in Vacuum. E. C. McKannan and K. E. Demorest, LubriCat&Z .&&g., 20 (4) (1964) 134-141; 15 figs., 4 tables, 13 refs. Thirteen candidate dry-film lubricants were selected for testing on a small, single degree of freedom, gimbal simulation device. The two lubricants which provided the required combination of properties were: (a) a mixture of molybdenum disulphide, graphite and gold powders with a binder of sodium silicate which was capable of being sprayed with an air gun, and (b) a flame-sprayable coating of zirconi-
4.1. Calculations Dynamic Characteristics of a Hydrostatic Thrust Bearing. J. B. Hunt, Second Convention on Lubrication and Wear, rg64, Paper 17. To be published in the Proc. Inst. Mech. E+zgrs., London, 196411965; 6 figs., 5 refs. An earlier comprehensive application of the Navier-Stokes equations to the problem of the oscillatory loading of hydrostatic thrust bearings has been linearized, and shown experimentally to be true for ratios of vibration amplitude to oil film thickness not exceeding I/IO. From the resulting expressions, the stiffness and damping constant of an oil film can be readily found. Non-linear Modes of Vibration of a Rigid Rotor in Short Journal Bearings. N. J. Huggins, Second Convention on Lubrication and Wear, 1964, Paper 18. To be published in the Proc. inst. M&t. Engrs., London, r&/1965; 8 figs., 12 refs. An unusual analytical approach to oil whirl is presented. Instead of using linearized equations for the oil forces all the non-linear terms are retained. The complex equations are solved on an analogue computer, and the more important results are given which show the unusual vibration characteristics of an oil film. It is shown that self-sustained oscillations can exist and, with an exciting force, sub-harmonics are likely. Also the frequency of response may be a sub- or super-multiple of the exciting force. Ocvirk’s short bearing approximation is used as the basis of the analysis. It is recognized that it has certain deficiencies, and the results are therefore treated as indications and not as accurate predictions. Comparison with other theoretical and experimental work supports the validity of the present analysis. Wear, 8 (1965) 143-155