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USA gas bearing meeting
I
CONFERENCE REPORTS SLOUGH. 13-14 MARCH 1972
5th UK/USA Gas bearing meeting US Office of Naval Research and the Admiralt/ Compass Observatory
The largest yet of this international series of liaison meetings was held at Admiralty Compass Observatory in March. The meeting was jointly sponsored by the US Office of Naval Research and by ACO, acting for MOD (N) as sponsors of the British Gas Bearing Panel. Fifteen members of the ONR Gas Bearing Group came over to join fifty British delegates for two days of papers and discussions. The chair on the first day was taken by H. J. Elwertowski, Head of ACO, and on the second day was shared between S. W. Doroff, Co-Chairman, Administrator of the ONR Group and A. G. Patterson of ACO, Vice-Chairman. The meeting was opened by Mr Elwertowski who, in addition to welcoming delegates, gave a short valedictory address in view of his imminent retirement. Mr Doroff responded, emphasizing again the great technical benefits to both nations of this continuing information interchange and paying tribute to all Mr Elwertowski had done in building up international liaison in this field to its present high level. The first presentation was by J. Kerr (NEL, East Kilbride) who described a 120 000 rev/min spindle with externallypressurized thrust and self-acting journal bearings which gave very high stiffness with very low air flow. W. G. Denhard (Associate Director, Draper Laboratory, MIT, Cambridge, Mass) talked about the shortcomings encountered in the gas bearing gyro field between results experienced in practice and those theoretically computed. Although partly accounted for by assumptions and inexacti. tudes in theory and by inaccuracy of manufacture, there was still an unaccountable leeway which had to be made good in hardware at the cost of higher power consumption. A review of the general gas bearing work at the Franklin' Institute was given by W. Shapiro. In particular he discussed the merits of spiral-groove thrust bearing computations based on the narrow groove theory. P. Cooke described three air bearing projects in hand at the Cranfield Unit of Precision Engineering - an air bearing rotary table with a 72 000 line grating able to resolve 0.9 arc/s, an externally-pressurized gas bearing surfacegrinding machine for making self-acting gas bearing components and a similar machine for cylindrical components. E. Hall (Draper Laboratory, MIT, Cambridge, Mass) described work of his department for the US Navy in design and manufacturing supervision of gas bearing gyros used in such applications as Poseidon. Among new projects of his department were very successful trials of beryllia as a gyro bearing materials, which had trebled the start-stop life of some experimental gyros. Glow discharge had been added to his gyro cleaning. More work at MIT, on the use of boron carbide as a bearing material in a small gas bearing gyro accelerometer, was outlined by J. Nelson. This material is almost unique in its property of surface improvement as a result of being rubbed
against itself, and no boundary lubricant to assist starting was needed for lightweight rotors. O. Decker (MTI, Albany, NY) described two projects on the application of gas bearings to aircraft gas turbines. The first was a turbo-shaft engine for the US Army where chrome oxide/nichrome bearings would be used to deal with the static and manoevering touch-down loads. The second was a turbo-jet and ramjet in one engine for the US Air force. The high-temperature, high.speed, |ong-lffe capdb~lity of air bearings made them ideal for these engines, and between 1975 and 1985 it was planned to include turbine end, main shaft and ultimately gear boxes in the air bearing programme. Methods used by the Swansea Tribology Centre for examining the microstructure of bearing surfaces were described by A. R. Lansdoval. The microcartography system was introduced to Swansea from USA and had been further developed for tribological use to provide contoured surface maps derived by computation and plotting from a two-dimentsional Talysurf readout. The Auger Technique was a highly sensitive means of examining surfaces as thin as a few monolayers and was based on identifying by frequency secondary electrons emitted from an electron-bombarded surface. Professor H. G. Elrod (Columbia University, New York) discussed the effects of surface roughness on gas bearings, which could be significant with laminar flow in narrow clearances. Long wavelength roughness was covered by Reynolds equation, but short wavelength or 'Stokes' roughness required several effects to be taken into account Circulating eddies in lathe striation and in grooved bearings were particular cases to be considered. J. McCabe (Franklin Institute, Philadelphia, Pa) described a selection of thrust bearings being studied at Franklin for space power use in Brayton cycle turboalternators. Two presentations from the University of Southampton followed - R. Wooley reported upon the latest results obtained with March's two dimension vibration apparatus for determining whirl onset speeds in gas bearings while D. Dewar gave an account of his work in evolving a design method and performance prediction system for spiral-groove bearings using oil or grease as a lubricant. The second day was started with a presentation by D. Cooke (RAE, Farnborough) who considered a method of improving the load-to-size capability of squeeze-film bearings. The basis of the method was provision of axial grooving to provide ambient line boundaries to support areas which could, on short bearings, improve lift by a factor of 2%. R. Burton (North West University, Evanston, III) reported on some interaction effects between two sliding surfaces, taking account of friction heating, wear, thermal conductivity and changes in pressure distribution which occur.
TRIBOLOGY August 1972
177
W. Shapiro (Franklin Inst, Philadelphia, Pa) reviewed the gas bearing activity at the Franklin, mentioning particularly the turbo-machinery bearings used in space power applications, cryogenic machinery, porous bearings, seals and compliant bearings. He further discussed advantages of using numerical methods to solve gas bearing problems and outlined some new concepts such as compliant pad, leaf foil and foil rotor bearings. The consideration of using externally-pressurized bearings in instruments, especially the effects of size on mass flow rate and of turbine torques was discussed by B. Trainex (BAC, Stevenage). Two presentations on spiral-groove bearings followed C. Pan compared his 'Narrow groove theory' for spiral-groove thrust plates with the findings of earlier researchers such as Wildman, summarizing the conditions where his theory showed better validity, while T. Ellis (RAE, Farnborough) described the methods developed by RAE and Ferranti, Edinburgh, for making spiral-grooved cones for the modified Kearfott 2519 gyro. J. Publicover (MIT, Cambridge, Mass) gave an account of failure mechanisms at start-up in ceramic gyro bearings due to debris. Finely divided alumina, excess lithium stearate (used as a boundary lubricant) and products of epoy resins had all been detected by the sensitive analytical techniques employed. Prominent among these were mass spectrometry, scanning electron microscopy, electron microprobe
and X-ray diffraction. In addition to obvious corrective actions, MIT were now using domestic pressure cookers to decontaminate gyro bearing components. I. S. Donaldson (Queens University, Belfast) gave a progress report on his work with porous inserts for externallypressurized bearings and described his loading pad, porous bearing test rig and some results obtained with it. Work at Columbia on tilting-pad beatings with compliant surfaces, giving pressure distributions obtained by crystal transducers was described by G. Rightmire. Prof V. Castelfi (Columbia Univ, New York) discussed the effects of inertia and viscoelasticity in bearings with a compliant' surface such as rubber, dealing both with slider and journal configurations. P. Szego (Ampex, Redwood City, Cal) then summarized gas bearing work in progress at Ampex and described in detail air bearing applications to rotate mirror scanning systems for laser beam recorders and high speed photography. The final presentation was from A. Huxley who gave a progress report on squeeze-film bearings work at ACO, He made a comparison of the observed experimental behaviour of a number of conical and hemispherical bearing assemblies in sandwich configuration, similar crystals being used throughout. In addition, he described the driving circuits used and explained his systems of instrumentation. A. G. Patterson
HOUSTON. 1 - 4 MAY 1972
ASLE Annual meeting American Society of Lubrication Engineers
The American Society of Lubrication Engineers held its Annual Meeting from 1 - 4 May at the Rice Hotel in Houston, Texas. Over one thousand people attended the meeting. In addition to over thirty technical sessions, there were three education courses. The education courses dealt with basic lubrication, seals and pollution. In keeping with the meeting theme, a symposium held during the meeting dealt with 'Occupational safety and health'. The symposium centered itself on the topic of the Occupational, Safety and Health Act. The programme also contained a pollution symposium. Topics covered in this symposium included the pollution problems associated with the disposal of metalworking fluids, filtration systems and the means for removing oil concentrations of below 50 mg/l of water. Presentations in these areas were followed by a panel dealing with pollution control and abatement. Properties of lubricants papers dealt with such subjects as viscosity loss in fluids due to shear, the effect of high pressures on the viscosity and elasticity of lubricants and cross flow in starved e.h.d, contacts. An attempt was also made by one author to delve into the complexity of even conventional lubricants. An interesting paper in the field of solid film lubrication reviewed chemical reactions between solids. Chemical reactions were treated where the chemical activation energy is generated by mechanical forces. The formation of FeS from the reaction of MoS2 with steel surfaces and iron phosphides from the interaction of Zn2 P2 07 with steels
178
TRIBOLOGY August 1972
were discussed. Another paper dealt with the interaction of sulphur impregnated sintered iron with molybdenum and tungsten surfaces during sliding contact. The authors used differential thermal analysis and wet chemical analysis to establish that during sliding mechanical forces activated the formation of MoS2 and WS2 from the elemental interactions of molybdenum and tungsten with sulphur. An aerospace symposium addressed itself to the subject of long term versus accelerated testing. After hearing three papers on the subject, one is still forced to conclude that there are some very definite pitfalls in trying to predict long term life from short term or accelerated testing. This appears to be particularly true with solid film lubricants. In the area of lubrication fundamentals, some topics were the use of Auger analysis in dynamic friction studies, the effect of electronic structure of crystalline solids on their lubricating properties and material considerations for aircraft brakes. Auger emission spectroscopy analysis was used during sliding friction experiments to monitor the changes in surface chemistry that were occurring as a result of solid to solid interactions. Auger analysis is particularly good at detecting light elements such as carbon, sulphur, phosphorus, oxygen and chlorine. Further, it has extremely good sensitivity. Oxygen surface concentrations of as little as a hundredth of a monolayer can be readily detected. A fundamental paper discussed the relationship of electronic structure of various solids to their lubricating properties. Experimental results were used to verify a proposed model structure for solid lubrication.
CONFERENCE REPORTS SLOUGH. 13-14 MARCH 1972
5th UK/USA Gas bearing meeting US Office of Naval Research and the Admiralt/ Compass Observatory
The largest yet of this international series of liaison meetings was held at Admiralty Compass Observatory in March. The meeting was jointly sponsored by the US Office of Naval Research and by ACO, acting for MOD (N) as sponsors of the British Gas Bearing Panel. Fifteen members of the ONR Gas Bearing Group came over to join fifty British delegates for two days of papers and discussions. The chair on the first day was taken by H. J. Elwertowski, Head of ACO, and on the second day was shared between S. W. Doroff, Co-Chairman, Administrator of the ONR Group and A. G. Patterson of ACO, Vice-Chairman. The meeting was opened by Mr Elwertowski who, in addition to welcoming delegates, gave a short valedictory address in view of his imminent retirement. Mr Doroff responded, emphasizing again the great technical benefits to both nations of this continuing information interchange and paying tribute to all Mr Elwertowski had done in building up international liaison in this field to its present high level. The first presentation was by J. Kerr (NEL, East Kilbride) who described a 120 000 rev/min spindle with externallypressurized thrust and self-acting journal bearings which gave very high stiffness with very low air flow. W. G. Denhard (Associate Director, Draper Laboratory, MIT, Cambridge, Mass) talked about the shortcomings encountered in the gas bearing gyro field between results experienced in practice and those theoretically computed. Although partly accounted for by assumptions and inexacti. tudes in theory and by inaccuracy of manufacture, there was still an unaccountable leeway which had to be made good in hardware at the cost of higher power consumption. A review of the general gas bearing work at the Franklin' Institute was given by W. Shapiro. In particular he discussed the merits of spiral-groove thrust bearing computations based on the narrow groove theory. P. Cooke described three air bearing projects in hand at the Cranfield Unit of Precision Engineering - an air bearing rotary table with a 72 000 line grating able to resolve 0.9 arc/s, an externally-pressurized gas bearing surfacegrinding machine for making self-acting gas bearing components and a similar machine for cylindrical components. E. Hall (Draper Laboratory, MIT, Cambridge, Mass) described work of his department for the US Navy in design and manufacturing supervision of gas bearing gyros used in such applications as Poseidon. Among new projects of his department were very successful trials of beryllia as a gyro bearing materials, which had trebled the start-stop life of some experimental gyros. Glow discharge had been added to his gyro cleaning. More work at MIT, on the use of boron carbide as a bearing material in a small gas bearing gyro accelerometer, was outlined by J. Nelson. This material is almost unique in its property of surface improvement as a result of being rubbed
against itself, and no boundary lubricant to assist starting was needed for lightweight rotors. O. Decker (MTI, Albany, NY) described two projects on the application of gas bearings to aircraft gas turbines. The first was a turbo-shaft engine for the US Army where chrome oxide/nichrome bearings would be used to deal with the static and manoevering touch-down loads. The second was a turbo-jet and ramjet in one engine for the US Air force. The high-temperature, high.speed, |ong-lffe capdb~lity of air bearings made them ideal for these engines, and between 1975 and 1985 it was planned to include turbine end, main shaft and ultimately gear boxes in the air bearing programme. Methods used by the Swansea Tribology Centre for examining the microstructure of bearing surfaces were described by A. R. Lansdoval. The microcartography system was introduced to Swansea from USA and had been further developed for tribological use to provide contoured surface maps derived by computation and plotting from a two-dimentsional Talysurf readout. The Auger Technique was a highly sensitive means of examining surfaces as thin as a few monolayers and was based on identifying by frequency secondary electrons emitted from an electron-bombarded surface. Professor H. G. Elrod (Columbia University, New York) discussed the effects of surface roughness on gas bearings, which could be significant with laminar flow in narrow clearances. Long wavelength roughness was covered by Reynolds equation, but short wavelength or 'Stokes' roughness required several effects to be taken into account Circulating eddies in lathe striation and in grooved bearings were particular cases to be considered. J. McCabe (Franklin Institute, Philadelphia, Pa) described a selection of thrust bearings being studied at Franklin for space power use in Brayton cycle turboalternators. Two presentations from the University of Southampton followed - R. Wooley reported upon the latest results obtained with March's two dimension vibration apparatus for determining whirl onset speeds in gas bearings while D. Dewar gave an account of his work in evolving a design method and performance prediction system for spiral-groove bearings using oil or grease as a lubricant. The second day was started with a presentation by D. Cooke (RAE, Farnborough) who considered a method of improving the load-to-size capability of squeeze-film bearings. The basis of the method was provision of axial grooving to provide ambient line boundaries to support areas which could, on short bearings, improve lift by a factor of 2%. R. Burton (North West University, Evanston, III) reported on some interaction effects between two sliding surfaces, taking account of friction heating, wear, thermal conductivity and changes in pressure distribution which occur.
TRIBOLOGY August 1972
177
W. Shapiro (Franklin Inst, Philadelphia, Pa) reviewed the gas bearing activity at the Franklin, mentioning particularly the turbo-machinery bearings used in space power applications, cryogenic machinery, porous bearings, seals and compliant bearings. He further discussed advantages of using numerical methods to solve gas bearing problems and outlined some new concepts such as compliant pad, leaf foil and foil rotor bearings. The consideration of using externally-pressurized bearings in instruments, especially the effects of size on mass flow rate and of turbine torques was discussed by B. Trainex (BAC, Stevenage). Two presentations on spiral-groove bearings followed C. Pan compared his 'Narrow groove theory' for spiral-groove thrust plates with the findings of earlier researchers such as Wildman, summarizing the conditions where his theory showed better validity, while T. Ellis (RAE, Farnborough) described the methods developed by RAE and Ferranti, Edinburgh, for making spiral-grooved cones for the modified Kearfott 2519 gyro. J. Publicover (MIT, Cambridge, Mass) gave an account of failure mechanisms at start-up in ceramic gyro bearings due to debris. Finely divided alumina, excess lithium stearate (used as a boundary lubricant) and products of epoy resins had all been detected by the sensitive analytical techniques employed. Prominent among these were mass spectrometry, scanning electron microscopy, electron microprobe
and X-ray diffraction. In addition to obvious corrective actions, MIT were now using domestic pressure cookers to decontaminate gyro bearing components. I. S. Donaldson (Queens University, Belfast) gave a progress report on his work with porous inserts for externallypressurized bearings and described his loading pad, porous bearing test rig and some results obtained with it. Work at Columbia on tilting-pad beatings with compliant surfaces, giving pressure distributions obtained by crystal transducers was described by G. Rightmire. Prof V. Castelfi (Columbia Univ, New York) discussed the effects of inertia and viscoelasticity in bearings with a compliant' surface such as rubber, dealing both with slider and journal configurations. P. Szego (Ampex, Redwood City, Cal) then summarized gas bearing work in progress at Ampex and described in detail air bearing applications to rotate mirror scanning systems for laser beam recorders and high speed photography. The final presentation was from A. Huxley who gave a progress report on squeeze-film bearings work at ACO, He made a comparison of the observed experimental behaviour of a number of conical and hemispherical bearing assemblies in sandwich configuration, similar crystals being used throughout. In addition, he described the driving circuits used and explained his systems of instrumentation. A. G. Patterson
HOUSTON. 1 - 4 MAY 1972
ASLE Annual meeting American Society of Lubrication Engineers
The American Society of Lubrication Engineers held its Annual Meeting from 1 - 4 May at the Rice Hotel in Houston, Texas. Over one thousand people attended the meeting. In addition to over thirty technical sessions, there were three education courses. The education courses dealt with basic lubrication, seals and pollution. In keeping with the meeting theme, a symposium held during the meeting dealt with 'Occupational safety and health'. The symposium centered itself on the topic of the Occupational, Safety and Health Act. The programme also contained a pollution symposium. Topics covered in this symposium included the pollution problems associated with the disposal of metalworking fluids, filtration systems and the means for removing oil concentrations of below 50 mg/l of water. Presentations in these areas were followed by a panel dealing with pollution control and abatement. Properties of lubricants papers dealt with such subjects as viscosity loss in fluids due to shear, the effect of high pressures on the viscosity and elasticity of lubricants and cross flow in starved e.h.d, contacts. An attempt was also made by one author to delve into the complexity of even conventional lubricants. An interesting paper in the field of solid film lubrication reviewed chemical reactions between solids. Chemical reactions were treated where the chemical activation energy is generated by mechanical forces. The formation of FeS from the reaction of MoS2 with steel surfaces and iron phosphides from the interaction of Zn2 P2 07 with steels
178
TRIBOLOGY August 1972
were discussed. Another paper dealt with the interaction of sulphur impregnated sintered iron with molybdenum and tungsten surfaces during sliding contact. The authors used differential thermal analysis and wet chemical analysis to establish that during sliding mechanical forces activated the formation of MoS2 and WS2 from the elemental interactions of molybdenum and tungsten with sulphur. An aerospace symposium addressed itself to the subject of long term versus accelerated testing. After hearing three papers on the subject, one is still forced to conclude that there are some very definite pitfalls in trying to predict long term life from short term or accelerated testing. This appears to be particularly true with solid film lubricants. In the area of lubrication fundamentals, some topics were the use of Auger analysis in dynamic friction studies, the effect of electronic structure of crystalline solids on their lubricating properties and material considerations for aircraft brakes. Auger emission spectroscopy analysis was used during sliding friction experiments to monitor the changes in surface chemistry that were occurring as a result of solid to solid interactions. Auger analysis is particularly good at detecting light elements such as carbon, sulphur, phosphorus, oxygen and chlorine. Further, it has extremely good sensitivity. Oxygen surface concentrations of as little as a hundredth of a monolayer can be readily detected. A fundamental paper discussed the relationship of electronic structure of various solids to their lubricating properties. Experimental results were used to verify a proposed model structure for solid lubrication.