The main role of a lubricant is to form a protective, low shear strength film between rubbing surfaces and thereby reduce friction and surface damage. The science, or art, of both the lubricant and the mechanical designer is to develop combinations of lubricant and mechanical system best able to form such films. This task is not straightforward since modern technology is continually demanding lower friction and better protection over an ever-widening range of operating conditions. Furthermore, environmental concerns are also producing both design constraints and the need for rapid change.
The aim of this paper is to show how progress is being made by experimental research which looks inside rubbing contacts to see how lubricants behave therein. The paper focuses on concentrated contacts, as found in gears, cams and rolling element bearings, and describes a number of techniques for probing such contacts to observe just how a range of lubricant types, from greases to emulsions, behave in such contacts to reduce friction and form films.
Get full access to this article
View all access options for this article.
References
1.
HamrockB. T.DowsonD.Ball bearing lubrication: the elastohydrodynamics of elliptical contacts, 1981, John Wiley, New York).
2.
GoharR.CameronA.The mapping of elastohydrodynamic contacts. ASLE Trans., 1967, 10, 215–225.
3.
FoordC. A.HammanW. C.CameronA.Evaluation of lubricants using optical elastohydrodynamics. ASLE Trans., 1968, 11, 31–43.
4.
JohnstonG. J.WayteR.SpikesH. A.The measurement and study of very thin lubricant films in concentrated contacts. STLE Trans., 1991, 34, 187–194.
5.
AderinM.JohnsonG. J.CaporiccioG.SpikesH. A.The elastohydrodynamic properties of some advanced non hydrocarbon-based lubricants. Lubric. Engng, 1992, 48, 633–638.
6.
HoultD. P.LuxJ. P.WongV. W.BillianS. A.Calibration of laser fluorescence of film thickness in engines. SAE technical series, 881587, 1988.
7.
RichardsonD. A.BormanG. L.Using fibre optics and laser fluorescence for measuring thin oil films with applications to engines. SAE technical series 912388, 1991.
8.
TurchinaV.SanbornD. M.WinerW. O.Temperature measurements in sliding elastohydrodynamic point contacts. Trans. ASME, J. Lubric. Technol., 1974, 96, 464–471.
9.
AushermanV. K.NagarajH. S.SanbornD. M.WinerW. O.Infrared temperature mapping in elastohydrodynamic lubrication. Trans. ASME, J. Lubric. Technol., 1976, 98, 236–243.
10.
ChangH-S.WayteR.SpikesH. A.Infrared study of piston ring temperatures in a firing engine. STLE Trans., 1993, 36, 104–112.
11.
CannP. M.SpikesH. A.Determination of the shear stresses of lubricants in elastohydrodynamic contacts. STLE Trans., 1989, 32, 414–422.
12.
LauerJ. L.AhnY-J.Lubricants and lubricant additives under shear studied under operating conditions by optical and infrared spectroscopic methods. STLE Trans., 1988, 31, 120–127.
13.
LauerJ. L.Study of polyphenyl ether fluid (5P4E) in operating elastohydrodynamic contacts by infrared emission spectroscopy. Trans. ASME, J. Lubric. Technol., 1979, 101, 67–73.
14.
CannP. M.SpikesH. A.In lubro studies of lubricants in EHD contacts using FTIR absorption spectroscopy. STLE Trans., 1991, 34, 248–256.
15.
CannP. M.AderinM.JohnstonG. J.SpikesH. A.Orientation and film-forming properties of thermotropic liquid crystals in EHD contacts. Proceedings of Eighteenth Leeds-Lyon Symposium on Tribology, Lyon, September 1991; published in Wear particles (Eds D. Dowson et al.), 1992 (Elsevier, Barking).
16.
GardinerD. J.BairdE.GorvinA. C.MarshallW. E.Dare-EdwardsM. P.Raman spectra of lubricants in elastohydrodynamic entrapments. Wear, 1983, 91, 111–114.
17.
MansotJ. L.MartinJ. M.Measurements of local pressure in a static sphere/plane interface containing organic compounds by means of Raman spectroscopy. Proceedings of Twelfth Leeds-Lyon Symposium on Tribology, Lyon, September 1985; published in Mechanisms and surface distress (Eds D. Dowson et al.), 1986, p. 234 (Butterworths, London).
18.
WanG. T. Y.SpikesH. A.The behaviour of suspended solid in rolling and sliding elastohydrodynamic contacts. STLE Trans., 1988, 31, 12–21.
19.
SheasbyJ. S.CaughlinT. A.HabeebJ. J.Observation of the anliwear activity of zinc dialkyldithiophosphate additives. Wear, 1991, 150, 247–257.
20.
WedevenL. D.Optical measurements in elastohydrodynamic rolling-contact bearings. PhD thesis, University of London, March 1970.
21.
SpikesH. A.CannP.CaporiccioG.Elastohydrodynamic film thickness measurements of perfluoropolyethers. J. Synth. Lubric., 1984, 1, 73–86.
22.
PembertonJ. C.CameronA.An optical study of the lubricants of a cylindrical roller bearing. Trans. ASME, J. Lubric. Technol., 1979, 101, 327–337.
23.
RutlinH.Optical elastohydrodynamics for constant velocity joints. Presented at an IMechE Meeting on The mission of tribology research, December 1992 (Mechanical Engineering Publications, London).
24.
GunselS.SpikesH. A.AderinM.In-situ measurement of ZDDP films in concentrated contacts. Preprint 92-AM-3C-4, 1992.
25.
GuangtengG.CannP. M.SpikesH. A.A study of parched lubrication. Wear, 1992, 153, 91–105.
26.
BarkerD. C.JohnstonG. J.SpikesH. A.BünemannT.EHD film formation and starvation of oil in water emulsions. Presented at STLE/ASME Joint Conference, October 1992, paper 92-TC-1B-1; to be published in STLE Trans.
27.
CannP. M.SpikesH. A.Film thickness measurements of lubricating greases under normally starved conditions. NLGI Spokesman, 1992, 56, 21–31.
28.
HirstW.MooreA. J.Non-Newtonian behaviour in EHL. Proc. R. Soc. Lond., 1974, A337, 101–121.
29.
EvansC. R.JohnsonK. L.The rheological properties of elastohydrodynamic lubricants. Proc. Instn Mech. Engrs, Part C, 1986, 200(C5), 303–312.
30.
BairS.QureshiF.WinerW. O.Observations of shear localization in liquid lubricants under high pressure. Presented at ASME/STLE Joint Conference, San Diego, October 1992, ASME paper 92-TRIB-3.
31.
ChangH-S.BunemannT.SpikesH. A.The shear stress properties of ester lubricants in elastohydrodynamic contacts. J. Synth. Lubric, 1992, 9, 91–114.
32.
GardinerD. J.BairdE. M.CraggsC.Raman microspectroscopy of a working elastohydrodynamic contact. Lubric. Sci., 1989, 1, 301–313.
33.
SpikesH. A.CannP. M.CoyR. C.WardleR. W. M.An in lubro study of VI improvers in EHD contacts. Lubric. Sci., 1990, 3, 45–62.
34.
KaliopoulosM.The use of infrared emission microscopy to measure cylinder liner and piston ring temperatures in a fired diesel engine. MSc thesis, University of London, September 1992.
35.
XianL.ZhengL.A new model for the experimental investigation of contact in mixed lubrication. Wear, 1989, 132, 221–233.
36.
SafaM. M. A.AndersonJ. C.LeatherJ. A.Transducers for pressure, temperature and oil film thickness measurements in bearings. Sensors and Actuators, 1982–3, 3, 119–128.
