- Email: [email protected]
Materials for gears
Conclusions Although it is impossible in a short article to discuss all the factors which affect the selection of gear materials, it is hoped that this summary of tribological data drawn from many sources will be useful in giving initial guidance.
Acknowledgements The author would like to thank Fulmer Research Institute Ltd., for
permission to publish this article: much of the data presented is from the Fulmer Materials Optimizer's + Section on Wear which was prepared for Fulmer by Michael Neale and Associates. Thanks are also due to the author's colleagues for their invaluable
comments and suggestions. As this data was initially drawn from many sources, the list of references would be longer than the article itself: nevertheless the author would like to thank all those who have contributed by publishing the results of their work.
+ The Fulmer Materials Optlmtzer is pubhshed by the Fulmer Research Institute Lid, Stoke Poges, Slough SL2 4QD, UK. The Optimizer costs £350, whtch includes an updatmg subscription which covers a period o f 12 months f r o m the date o f purchase.
September 13-16, 1977, Lyon, France
Effects of Surface Roughness in Lubrication
Evidence is growing that 'single subject' conferences are more attractive than general meetings. This year's Leeds-Lyon Symposium, the fourth in an annual series, attracted over 80 delegates from 11 countries to the Institut National de Sciences Applique de Lyon: 40 papers were presented during the three day symposium.
surfaces. If the surface roughness is of the same order of magnitude as the film thickness, assumption of 'Reynolds' conditions is not valid. Dyson7 reviewed theoretical work on the effect of roughness in classical hydrodynamic and elasto-hydrodynamic lubrication. He concluded that little progress has been made in solving problems of technological interest.
Dowson ~ set the tone of the meeting with a review of early concepts of surface topography. He reviewed developments from the 16th to the 19th century and showed that they " . . . modelled satisfactorily the major tribological problem of the day - friction". The meeting discussed the latest attempts to characterise surfaces and to model and understand tribological problems of the 20th century.
Lebeck 6 presented a study of mixed lubrication in contacting mechanical face seals. He argued that waviness of the seal faces is a major source of hydrodynamic load support: a twodimensional model incorporating Christensen's approach to mixed friction was developed and applied to a heavily loaded water seal. The model predicted 980/0 hydrodynamic load support, but the author noted that the assumptions used may have given a "significant overestimate".
Hydrodynamics Four papers 5-5 discussed the effect of surface roughness in hydrodynamic lubrication. The detail of various mathematical analyses of fluid film lubricated contacts with no asperity interaction was reviewed. While the work is no doubt of some academic interest, it is hard to see the practical significance: indeed Saibel remarked that his paper was "more a manipulation of stochastic variables than of value to the engineer". In most applications of technological interest, there is some degree of contact or interference between the
ChengSdiscussed three aspects of microelastohydrodynamic lubrication: normal approach of asperities, sliding, and asperity-asperity collisions. Tonder 9 outlined the basis of his analysis of the lubrication of a surface with cross-striated roughness.
Running-in Thomas '° opened the session on running-in with a review of problem of "putting numbers to pictures". A survey of a number of published papers found 12 parameters and two functions in use to describe changes in topography. Thomas suggests that
most of the information needed to characterise running-in is contained in two functions, the power spectrum and the height distribution. He noted, however, that there are experimental and computational problems such as relocation, changes in skewness that may be due to the effect of random sampling, and non-stationarity. Berthe" described techniques used at INSA to characterise surface microgeometry and illustrated their application to a running-in situation. Raffy '~ presented three-dimensional images of the surfaces of XC48 steel spur gears and showed the changes of topography during running-in and running. Barwell 's described ferrographic and spectrographic monitoring of the running-in wear of a diesel engine. Since the spectrometer's detection level depends on particle size, it did not indicate the high initial wear which was shown by the ferrograph.
Asperity interactions Two papers t3 ,s described computer simulation of the contact of rough surfaces. Bowyer discussed a development of the technique" to simulate stick-slip motion. A paper by Pavelescu and Tudor ~3 also discussed stick-slip. Greenwood" reviewed developments in the theory of surface topography, concentrating on features of most applicability to tribology. He took the opportunity to point to a frequent,
TRIBOLOGY mternational December 1977
331
fallacious, assumption that the height distribution of a surface roughness is Gaussian: the assumption is only true for certain surface preparation methods. He also cast some doubt on the validity of the assumed relationship between mechanical contact and electrical contact. Leather ~ argued that, despite some difficulties, electrical measurements may be used to monitor film thickness, surface topography changes, and wear rate in lubricated contacts. Winer '4 described experiments in which steel balls of different roughness were rubbed against sapphire fiats. Infrared temperature measurements, surface profilometry, and ferrographic analysis were used to monitor asperity interactions in the EHD contact. In such contacts it is suggested that ~,, the ratio of film thickness to surface roughness, is of some importance. Wirier stated that, on the basis of their data, the rms surface roughness to be used in calculating ~. should consider only wavelengths in the range d / 4 ~ . ~ 2d, where d is the Hertz diameter. In practical terms, if wavelengths shorter than 0.25d are not significant, the final stages of lapping and polishing may not be important for contacts with a large Hertz diameter.
Scuffing Dyson 20 surnmarised recent theoretical results on the elastohydrodynamic lubrication of rough surfaces in which the principal dimensions of the asperities are oriented in the direction of motion. The theory is based on the analysis of a single pair of surfaces, and similar analyses of other surfaces are obviously necessary. However, scuffing is predicted from first principles and the analysis may be applicable to smearing of rolling contact bearings. Dyson acknowledges that the treatment is purely physical, and does not include chemical and metallurgical factors, which are known to be important in scuffing. Ku 2' presented experimental data on scuffing in a twin disc machine at low slide-roll ratios with various material combinations, heat treatments, oil supplies, etc. He stated that he had " . . . lost some interest in the mecha n i s m . . . " and that he hopes " . . . to solve the engineering problem". In this context, and given the variation of experimental results for a given set of conditions, the paper states: "when a large volume of data are treated statistically, the assumption of a constant critical contact temperature for a given oil--metal--surface treatment - atmosphere combination is a good engineering approximation over a wide range of design and operating conditions."
Czichos gave an unscheduled presentation on the IRG work on scuffing. He proposed a stepwise mechanism: breakdown of the EHD film; breakthrough of surface layers; and establishment of strong metal metal adhesion. He showed a plot of critical load as a function of both sliding velocity and temperature, and suggested two possible failure modes: at low velocity, a stepwise approach and at high velocity all thre e steps occurring simultaneously. Berthe 22 described theoretical and experimental work on load division in an EHD contact. The paper suggests that ep additives perform two functions: formation of a protective film when hydrodynamic lubrication falls and modification of the surface to allow film formation at higher loads than the original surface could withstand.
Fatigue wear Pnueli23 discussed the choice between a continuum model and a discrete two temperature gradient model for contacting rough surfaces. Phillips25 described experiments on an Amsler disc-on-disc machine and a Unisteel rolling contact fatigue rig: he showed that for D ratios (surface roughness: lubricant film thickness) less than 1.5, ep additives decrease pitting life. Above this ratio, the converse is true. Godet presented two related papers 2',26 describing wear mechanisms in a disc machine. Micropits, sponges, fiats, macropits, surface wear, and spalls were discussed.
Bearings Heath 29 discussed the effect of machining method on marginally lubricated wear. While describing the work as "exploratory", he stated that it showed a significant difference between "real" machine finishes on standard engineering materials used in plain bearings. Hailing3' outlined a study of journal motion and bearing wear during start up of hydrodynamic bearings, illustrating the importance of shaft surface finish, clearance, and the soft metal film thickness. I-Ioppe 32 discussed film thickness, surface quality, and running-in effects in hydrodynamic journal bearings. Poon discussed the effect of waviness and surface roughness of balls and races in vibration noise of rolling contact bearings. He suggested that waviness may have been the predominant source of noise 10 - 20 years ago, but that this is probably not true of modern bearings. Decreasing waviness attributable to improved
332 TRIBOLOGY international December 1977
production techniques has placed greater emphasis on random surface roughness associated vibration.
General roughness effects George 2' described a correlation between leakage past a static elastomer joint seal and surface profile measurements. Moore ~' discussed scale effects in elastohydrodynamic lubrication for rubber-like materials and Mathia 3. discussed the role of roughness in boundary lubrication. King*°, in the final paper at the meeting, returned to the problem of describing surface changes in lubricated wear. He discussed the effect of truncation of a near Gaussian surface on parameters such as kurtosis, skewness, and autocorrelation function.
Comment The range of presentations gave the impression that the latest work in the field was reviewed. At times there was real controversy: unfortunately the shortage of time for discussion, due to the full programme, resulted in debate continuing in small groups long into the night, rather than in the conference sessions.
Papers presented* 1
Dowson D. Early concepts of
surface topography and their role in tribology 2
Etrod H. A Review of theories for roughness effects on laminar lubricating films Part 1 and Part 2
3
Chow P.L. and Saibel E. The
roughness effect in hydrodynamic lubrication 4
Rhode S.M. and Whicker D. Some
mathematical aspects of the hydrodynamic lubrication of rough surfaces 5
Sun D.C. and Chen K.K. On the
statistical treatment of rough surface hydrodynamic lubrication problems 6
LebeekA.O. A study of mixed lubrication m contacting mechamcal face seals
7
Dyson A. Hydrodynamic lubrication of rough surfaces. A review of theoretical work
8
Cheng H. On some aspects of microelastohydrodynamic lubrication
9
Tonder K. The lubrication of surfaces having a cross-striated roughness pattern
10
Thomas T.R. The charactensation of changes in surface topography in running-m
11
Foucher D., Flamand L., and Berthe
D. Variation of surface roughness parameters during running-m of lubrtcated Hertzlan contacts
12
Raffy J.C. Evolution of surface roughness of gear teeth
13
Bowyer A. and Cameron A. A computer sliding model of rough surfaces
14
Nagaraj H.S., Sanborn D.M., and Winer W.O. Asperity interactions in EHD contacts
15
23
Pnueli D. Role of surface roughness in the choice between a continuum model and a discrete twotemperature-gradient model for friction system
24
Berthe D., Michau B., Flamand L., and Godet M. Effect of roughness on pits and micropits in pure rolling lubrication
33
Paveleseu D. and Tudor A. Influence of the microgeometry on the ratio of static to dynamic coefficient of friction at low velocities
34
Lak S. Transport of solid lubricants by rough surfaces
35
Felder E. Interaction between friction, lubrication and surface roughness in metal working
36
POOhS.Y. Surface roughness and the rolling element bearing vibration
Jones M.H., Sastry V.R.K., and Youdan G.H. Study of running-in of diesel engines using particle analysis and spectrography oil analysis
25
16
MacPherson P.B. and Leather J.A. The practical use of electrical measurements in lubricated contacts
26
Flamand L. and Berthe D. Different forms of wear at low slide/roll ratio
37
Moore D.F. Scale effects in elastohydrodynamic lubricatio~t for rubberlike materials
17
Greenwood J. and Williamson J.P.E. Developments in the theory of surface topography
27
George A. Correlation of leakage past elastomer joint seals with surface profile measurements
38
Georges J.M., Kapsa P., and Mathia T. Roughness in boundary lubrication
18
Sayles H.S. and Thomas T.R. The plastic contact of two rough surfaces
28
Wileoek D. A look at the interaction between turbulence and surface roughness
39
19
Mirsid W. and Stupnieki J. Effects of surface roughness on the state of stresses of solids in contact
29
Stout K.J., Heath H.H., and King T.G. Ground surface finish. Its influence on marginally lubricated wear
Jones D.A. and Tate D. The investigation of various design factors intended to control distortion in a simple gas hearing machine
40
King T.G., Watson W., and Stout K.J. Modelling of microgeometry of lubricated wear
20
Dyson A. Failure of circumferentially ground discs
21
Ku P.M. Effect of surface topography on sliding-rolling disc scuffing
22
Berthe D., Flamand L., Foueher D., and Hassoun M. Theoretical and experimental investigation of load division in partial EHD. Effects of oil nature and roughness on surface failure
30
Quinn F.J. and PhUips M.R. The effect of surface roughness and lubricant film thickness upon contact fatigue
Rozeanu L. and Snarsky L. Physicochemical characterisation of surface roughness and its tribological implications
31
Halting J. The role of surface topography in the friction and wear of plain hydrodynamic bearings
32
Hoppe J. Minimum allowable film thickness, surface quality and running-in effect in journal bearings
July 12-15, 1977, Manchester, UK
18th Corrosion Science Symposium relevance were r a n d o m l y distributed t h r o u g h o u t the 31 days, m a k i n g selective a t t e n d a n c e difficult.
This a n n u a l event, n o w organised by the C o r r o s i o n Science Division o f the I n s t i t u t i o n o f C o r r o s i o n Science a n d Technology, a t t r a c t e d a record 44 papers. T h o u g h a f o r u m for postg r a d u a t e researchers to present their first work, p e r h a p s the greatest value to delegates f r o m i n d u s t r y is still keeping abreast with current developments a n d meeting people working in their field o f interest. 148 delegates a t t e n d e d the s y m p o s i u m , with representatives f r o m Australia, U S A a n d Europe.
Surface films
The s y m p o s i u m was divided into 9 sessions which included ' C o r r o s i o n in P o w e r G e n e r a t i o n ' a n d the ' I n f l u e n c e of Corrosion on Tribology'. Though the bulk o f the papers on those topics were g r o u p e d together, others o f
Chadwick and Hashemi's paper. ' N a t u r e o f Surface Films F o r m e d by C o r r o s i o n Inhibitors a n d Lubricating Additives' was the first tribological c o n t r i b u t i o n . Dr. C h a d w i c k stated that a l t h o u g h corrosion inhibitors a n d
O f the five papers concerned with tribology, the titles of four presentations indicated a m u c h b r o a d e r subject coverage t h a n was realised 'in c o n f e r e n c e ' ; availability o f abstracts b e f o r e the s y m p o s i u m , r a t h e r t h a n on arrival at the venue, would have avoided possible d i s a p p o i n t m e n t of delegates.
*Proceedings o f the conference will be pubhshed by Mechamcal Engineering Publicattons, P.O. Box 23, Bury St Edmunds, Suffolk 1P32 6B W, UK. The fifth Leeds-Lyon Symposium on Elastohydrodynamics and Related Topics will be held m Leeds from 19-22 September, 1978
o t h e r additives, are widely used, their surface chemistry is o f t e n not well u n d e r s t o o d . He d e m o n s t r a t e d h o w X - R a y p h o t o e l e c t r o n spectroscopy (XPS) identified the o x i d a t i o n state o f copper in the c o p p e r - b e n z a t r i a z o l e (BTA) system, a n d s h o w e d that over a wide variety o f conditions the surface film consists o f a C u ( I ) B T A complex, which is t h o u g h t to consist o f linear polymeric chains. A b s o r p t i o n o n copper-nickel also produces a C u ( I ) B T A surface complex, the time t a k e n to f o r m being a f u n c t i o n o f the alloy composition. However, this simple picture does not extend to brass, as b o t h copper a n d zinc were detected in the film. In contrast, 2-mercaptobenzothiazole (MBT) f o r m s exclusively a C u ( I J M B T complex o n copper a n d the two alloy systems investigated. A l t h o u g h n o actual work had been carried out on oil additions, the a u t h o r s considered that the use of X P S to o b t a i n the c o m p o s i t i o n of surface films may be usefully extended to o t h e r m e t a l - - a d d i t i v e c o m b i n a t i o n s . However, the i n f o r m a t i o n o b t a i n e d for copper
TRIBOLOGY international December 1977
333
Acknowledgements The author would like to thank Fulmer Research Institute Ltd., for
permission to publish this article: much of the data presented is from the Fulmer Materials Optimizer's + Section on Wear which was prepared for Fulmer by Michael Neale and Associates. Thanks are also due to the author's colleagues for their invaluable
comments and suggestions. As this data was initially drawn from many sources, the list of references would be longer than the article itself: nevertheless the author would like to thank all those who have contributed by publishing the results of their work.
+ The Fulmer Materials Optlmtzer is pubhshed by the Fulmer Research Institute Lid, Stoke Poges, Slough SL2 4QD, UK. The Optimizer costs £350, whtch includes an updatmg subscription which covers a period o f 12 months f r o m the date o f purchase.
September 13-16, 1977, Lyon, France
Effects of Surface Roughness in Lubrication
Evidence is growing that 'single subject' conferences are more attractive than general meetings. This year's Leeds-Lyon Symposium, the fourth in an annual series, attracted over 80 delegates from 11 countries to the Institut National de Sciences Applique de Lyon: 40 papers were presented during the three day symposium.
surfaces. If the surface roughness is of the same order of magnitude as the film thickness, assumption of 'Reynolds' conditions is not valid. Dyson7 reviewed theoretical work on the effect of roughness in classical hydrodynamic and elasto-hydrodynamic lubrication. He concluded that little progress has been made in solving problems of technological interest.
Dowson ~ set the tone of the meeting with a review of early concepts of surface topography. He reviewed developments from the 16th to the 19th century and showed that they " . . . modelled satisfactorily the major tribological problem of the day - friction". The meeting discussed the latest attempts to characterise surfaces and to model and understand tribological problems of the 20th century.
Lebeck 6 presented a study of mixed lubrication in contacting mechanical face seals. He argued that waviness of the seal faces is a major source of hydrodynamic load support: a twodimensional model incorporating Christensen's approach to mixed friction was developed and applied to a heavily loaded water seal. The model predicted 980/0 hydrodynamic load support, but the author noted that the assumptions used may have given a "significant overestimate".
Hydrodynamics Four papers 5-5 discussed the effect of surface roughness in hydrodynamic lubrication. The detail of various mathematical analyses of fluid film lubricated contacts with no asperity interaction was reviewed. While the work is no doubt of some academic interest, it is hard to see the practical significance: indeed Saibel remarked that his paper was "more a manipulation of stochastic variables than of value to the engineer". In most applications of technological interest, there is some degree of contact or interference between the
ChengSdiscussed three aspects of microelastohydrodynamic lubrication: normal approach of asperities, sliding, and asperity-asperity collisions. Tonder 9 outlined the basis of his analysis of the lubrication of a surface with cross-striated roughness.
Running-in Thomas '° opened the session on running-in with a review of problem of "putting numbers to pictures". A survey of a number of published papers found 12 parameters and two functions in use to describe changes in topography. Thomas suggests that
most of the information needed to characterise running-in is contained in two functions, the power spectrum and the height distribution. He noted, however, that there are experimental and computational problems such as relocation, changes in skewness that may be due to the effect of random sampling, and non-stationarity. Berthe" described techniques used at INSA to characterise surface microgeometry and illustrated their application to a running-in situation. Raffy '~ presented three-dimensional images of the surfaces of XC48 steel spur gears and showed the changes of topography during running-in and running. Barwell 's described ferrographic and spectrographic monitoring of the running-in wear of a diesel engine. Since the spectrometer's detection level depends on particle size, it did not indicate the high initial wear which was shown by the ferrograph.
Asperity interactions Two papers t3 ,s described computer simulation of the contact of rough surfaces. Bowyer discussed a development of the technique" to simulate stick-slip motion. A paper by Pavelescu and Tudor ~3 also discussed stick-slip. Greenwood" reviewed developments in the theory of surface topography, concentrating on features of most applicability to tribology. He took the opportunity to point to a frequent,
TRIBOLOGY mternational December 1977
331
fallacious, assumption that the height distribution of a surface roughness is Gaussian: the assumption is only true for certain surface preparation methods. He also cast some doubt on the validity of the assumed relationship between mechanical contact and electrical contact. Leather ~ argued that, despite some difficulties, electrical measurements may be used to monitor film thickness, surface topography changes, and wear rate in lubricated contacts. Winer '4 described experiments in which steel balls of different roughness were rubbed against sapphire fiats. Infrared temperature measurements, surface profilometry, and ferrographic analysis were used to monitor asperity interactions in the EHD contact. In such contacts it is suggested that ~,, the ratio of film thickness to surface roughness, is of some importance. Wirier stated that, on the basis of their data, the rms surface roughness to be used in calculating ~. should consider only wavelengths in the range d / 4 ~ . ~ 2d, where d is the Hertz diameter. In practical terms, if wavelengths shorter than 0.25d are not significant, the final stages of lapping and polishing may not be important for contacts with a large Hertz diameter.
Scuffing Dyson 20 surnmarised recent theoretical results on the elastohydrodynamic lubrication of rough surfaces in which the principal dimensions of the asperities are oriented in the direction of motion. The theory is based on the analysis of a single pair of surfaces, and similar analyses of other surfaces are obviously necessary. However, scuffing is predicted from first principles and the analysis may be applicable to smearing of rolling contact bearings. Dyson acknowledges that the treatment is purely physical, and does not include chemical and metallurgical factors, which are known to be important in scuffing. Ku 2' presented experimental data on scuffing in a twin disc machine at low slide-roll ratios with various material combinations, heat treatments, oil supplies, etc. He stated that he had " . . . lost some interest in the mecha n i s m . . . " and that he hopes " . . . to solve the engineering problem". In this context, and given the variation of experimental results for a given set of conditions, the paper states: "when a large volume of data are treated statistically, the assumption of a constant critical contact temperature for a given oil--metal--surface treatment - atmosphere combination is a good engineering approximation over a wide range of design and operating conditions."
Czichos gave an unscheduled presentation on the IRG work on scuffing. He proposed a stepwise mechanism: breakdown of the EHD film; breakthrough of surface layers; and establishment of strong metal metal adhesion. He showed a plot of critical load as a function of both sliding velocity and temperature, and suggested two possible failure modes: at low velocity, a stepwise approach and at high velocity all thre e steps occurring simultaneously. Berthe 22 described theoretical and experimental work on load division in an EHD contact. The paper suggests that ep additives perform two functions: formation of a protective film when hydrodynamic lubrication falls and modification of the surface to allow film formation at higher loads than the original surface could withstand.
Fatigue wear Pnueli23 discussed the choice between a continuum model and a discrete two temperature gradient model for contacting rough surfaces. Phillips25 described experiments on an Amsler disc-on-disc machine and a Unisteel rolling contact fatigue rig: he showed that for D ratios (surface roughness: lubricant film thickness) less than 1.5, ep additives decrease pitting life. Above this ratio, the converse is true. Godet presented two related papers 2',26 describing wear mechanisms in a disc machine. Micropits, sponges, fiats, macropits, surface wear, and spalls were discussed.
Bearings Heath 29 discussed the effect of machining method on marginally lubricated wear. While describing the work as "exploratory", he stated that it showed a significant difference between "real" machine finishes on standard engineering materials used in plain bearings. Hailing3' outlined a study of journal motion and bearing wear during start up of hydrodynamic bearings, illustrating the importance of shaft surface finish, clearance, and the soft metal film thickness. I-Ioppe 32 discussed film thickness, surface quality, and running-in effects in hydrodynamic journal bearings. Poon discussed the effect of waviness and surface roughness of balls and races in vibration noise of rolling contact bearings. He suggested that waviness may have been the predominant source of noise 10 - 20 years ago, but that this is probably not true of modern bearings. Decreasing waviness attributable to improved
332 TRIBOLOGY international December 1977
production techniques has placed greater emphasis on random surface roughness associated vibration.
General roughness effects George 2' described a correlation between leakage past a static elastomer joint seal and surface profile measurements. Moore ~' discussed scale effects in elastohydrodynamic lubrication for rubber-like materials and Mathia 3. discussed the role of roughness in boundary lubrication. King*°, in the final paper at the meeting, returned to the problem of describing surface changes in lubricated wear. He discussed the effect of truncation of a near Gaussian surface on parameters such as kurtosis, skewness, and autocorrelation function.
Comment The range of presentations gave the impression that the latest work in the field was reviewed. At times there was real controversy: unfortunately the shortage of time for discussion, due to the full programme, resulted in debate continuing in small groups long into the night, rather than in the conference sessions.
Papers presented* 1
Dowson D. Early concepts of
surface topography and their role in tribology 2
Etrod H. A Review of theories for roughness effects on laminar lubricating films Part 1 and Part 2
3
Chow P.L. and Saibel E. The
roughness effect in hydrodynamic lubrication 4
Rhode S.M. and Whicker D. Some
mathematical aspects of the hydrodynamic lubrication of rough surfaces 5
Sun D.C. and Chen K.K. On the
statistical treatment of rough surface hydrodynamic lubrication problems 6
LebeekA.O. A study of mixed lubrication m contacting mechamcal face seals
7
Dyson A. Hydrodynamic lubrication of rough surfaces. A review of theoretical work
8
Cheng H. On some aspects of microelastohydrodynamic lubrication
9
Tonder K. The lubrication of surfaces having a cross-striated roughness pattern
10
Thomas T.R. The charactensation of changes in surface topography in running-m
11
Foucher D., Flamand L., and Berthe
D. Variation of surface roughness parameters during running-m of lubrtcated Hertzlan contacts
12
Raffy J.C. Evolution of surface roughness of gear teeth
13
Bowyer A. and Cameron A. A computer sliding model of rough surfaces
14
Nagaraj H.S., Sanborn D.M., and Winer W.O. Asperity interactions in EHD contacts
15
23
Pnueli D. Role of surface roughness in the choice between a continuum model and a discrete twotemperature-gradient model for friction system
24
Berthe D., Michau B., Flamand L., and Godet M. Effect of roughness on pits and micropits in pure rolling lubrication
33
Paveleseu D. and Tudor A. Influence of the microgeometry on the ratio of static to dynamic coefficient of friction at low velocities
34
Lak S. Transport of solid lubricants by rough surfaces
35
Felder E. Interaction between friction, lubrication and surface roughness in metal working
36
POOhS.Y. Surface roughness and the rolling element bearing vibration
Jones M.H., Sastry V.R.K., and Youdan G.H. Study of running-in of diesel engines using particle analysis and spectrography oil analysis
25
16
MacPherson P.B. and Leather J.A. The practical use of electrical measurements in lubricated contacts
26
Flamand L. and Berthe D. Different forms of wear at low slide/roll ratio
37
Moore D.F. Scale effects in elastohydrodynamic lubricatio~t for rubberlike materials
17
Greenwood J. and Williamson J.P.E. Developments in the theory of surface topography
27
George A. Correlation of leakage past elastomer joint seals with surface profile measurements
38
Georges J.M., Kapsa P., and Mathia T. Roughness in boundary lubrication
18
Sayles H.S. and Thomas T.R. The plastic contact of two rough surfaces
28
Wileoek D. A look at the interaction between turbulence and surface roughness
39
19
Mirsid W. and Stupnieki J. Effects of surface roughness on the state of stresses of solids in contact
29
Stout K.J., Heath H.H., and King T.G. Ground surface finish. Its influence on marginally lubricated wear
Jones D.A. and Tate D. The investigation of various design factors intended to control distortion in a simple gas hearing machine
40
King T.G., Watson W., and Stout K.J. Modelling of microgeometry of lubricated wear
20
Dyson A. Failure of circumferentially ground discs
21
Ku P.M. Effect of surface topography on sliding-rolling disc scuffing
22
Berthe D., Flamand L., Foueher D., and Hassoun M. Theoretical and experimental investigation of load division in partial EHD. Effects of oil nature and roughness on surface failure
30
Quinn F.J. and PhUips M.R. The effect of surface roughness and lubricant film thickness upon contact fatigue
Rozeanu L. and Snarsky L. Physicochemical characterisation of surface roughness and its tribological implications
31
Halting J. The role of surface topography in the friction and wear of plain hydrodynamic bearings
32
Hoppe J. Minimum allowable film thickness, surface quality and running-in effect in journal bearings
July 12-15, 1977, Manchester, UK
18th Corrosion Science Symposium relevance were r a n d o m l y distributed t h r o u g h o u t the 31 days, m a k i n g selective a t t e n d a n c e difficult.
This a n n u a l event, n o w organised by the C o r r o s i o n Science Division o f the I n s t i t u t i o n o f C o r r o s i o n Science a n d Technology, a t t r a c t e d a record 44 papers. T h o u g h a f o r u m for postg r a d u a t e researchers to present their first work, p e r h a p s the greatest value to delegates f r o m i n d u s t r y is still keeping abreast with current developments a n d meeting people working in their field o f interest. 148 delegates a t t e n d e d the s y m p o s i u m , with representatives f r o m Australia, U S A a n d Europe.
Surface films
The s y m p o s i u m was divided into 9 sessions which included ' C o r r o s i o n in P o w e r G e n e r a t i o n ' a n d the ' I n f l u e n c e of Corrosion on Tribology'. Though the bulk o f the papers on those topics were g r o u p e d together, others o f
Chadwick and Hashemi's paper. ' N a t u r e o f Surface Films F o r m e d by C o r r o s i o n Inhibitors a n d Lubricating Additives' was the first tribological c o n t r i b u t i o n . Dr. C h a d w i c k stated that a l t h o u g h corrosion inhibitors a n d
O f the five papers concerned with tribology, the titles of four presentations indicated a m u c h b r o a d e r subject coverage t h a n was realised 'in c o n f e r e n c e ' ; availability o f abstracts b e f o r e the s y m p o s i u m , r a t h e r t h a n on arrival at the venue, would have avoided possible d i s a p p o i n t m e n t of delegates.
*Proceedings o f the conference will be pubhshed by Mechamcal Engineering Publicattons, P.O. Box 23, Bury St Edmunds, Suffolk 1P32 6B W, UK. The fifth Leeds-Lyon Symposium on Elastohydrodynamics and Related Topics will be held m Leeds from 19-22 September, 1978
o t h e r additives, are widely used, their surface chemistry is o f t e n not well u n d e r s t o o d . He d e m o n s t r a t e d h o w X - R a y p h o t o e l e c t r o n spectroscopy (XPS) identified the o x i d a t i o n state o f copper in the c o p p e r - b e n z a t r i a z o l e (BTA) system, a n d s h o w e d that over a wide variety o f conditions the surface film consists o f a C u ( I ) B T A complex, which is t h o u g h t to consist o f linear polymeric chains. A b s o r p t i o n o n copper-nickel also produces a C u ( I ) B T A surface complex, the time t a k e n to f o r m being a f u n c t i o n o f the alloy composition. However, this simple picture does not extend to brass, as b o t h copper a n d zinc were detected in the film. In contrast, 2-mercaptobenzothiazole (MBT) f o r m s exclusively a C u ( I J M B T complex o n copper a n d the two alloy systems investigated. A l t h o u g h n o actual work had been carried out on oil additions, the a u t h o r s considered that the use of X P S to o b t a i n the c o m p o s i t i o n of surface films may be usefully extended to o t h e r m e t a l - - a d d i t i v e c o m b i n a t i o n s . However, the i n f o r m a t i o n o b t a i n e d for copper
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