Showing papers in "Tribology Transactions in 1971"
TL;DR: In this article, the surface energy of adhesion of metal combinations in terms of their compatibility rating was derived for pairs consisting of 20 elemental metals, and the static friction coefficients were measured for pairs.
Abstract: Static friction coefficients were measured for pairs consisting of 20 elemental metals. The 210 friction values were compared against the metallurgical compatibility ratings of the corresponding two phase alloy systems. Soft metals gave higher friction than harder metals, and at the same hardness level there was a steady trend to lower friction in going from like, to compatible, to intermediate, and then to incompatible combinations. The results are interpreted in terms of the surface energy model of friction, and used to derive values for the surface energy of adhesion of metal combinations in terms of their compatibility rating. Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE Lubrication Conference held in Cincinnati, Ohio, October 13–15, 1970
124 citations
TL;DR: In this paper, an analytic expression for the steady state interfacial temperature field in a sliding circular Hertzian contact is derived, taking into account the ellipsoidal distribution of the frictional power and the difference between the bulk temperatures of the two bodies, for the case where one surface is stationary and the other rapidly moving with respect to the contact.
Abstract: An analytic expression/or the steady-state interfacial temperature field in a sliding circular Hertzian contact is derived, taking into account the ellipsoidal distribution of the frictional power and the difference between the bulk temperatures of the two bodies, for the case where one surface is stationary and the other rapidly moving with respect to the contact. Other cases may be treated in a similar manner. It is shown that the temperature at any point on the interface can be approximated, to an accuracy improving with velocity, by half the harmonic mean of the two surface temperatures attained at that point if each body were to receive all the frictional power. The resulting maximum flash temperature is 33–38% higher than that given by Blok's widely used formula. Presented at the 25th ASLE Annual Meeting in Chicago, May 4–8, 1970
88 citations
TL;DR: Sputtered MoS2films (2000-6500 A) were deposited on highly polished metal surfaces as mentioned in this paper, and they have an extremely small particle size, less than 30 A in diameter, and are very dense and free from observable pinholes.
Abstract: Sputtered MoS2films (2000–6500 A) were deposited on highly polished metal surfaces. These films have a low coefficient of friction (0.03–0.04) at speeds of 40–80 rpm and loads of 250–1000 grams. At loads of 250 grams the wear lives are over 0.5 million cycles, but at 1000 gram loads, it decreases to 38,000 cycles. Friction experiments and tensile tests have indicated that sputtered films have a strong adherence to metal surfaces. Electron transmission, diffraction and scanning electron microscopy show that these films have an extremely small particle size, less than 30 A in diameter, and are very dense and free from observable pinholes. The high kinetic energy of these sputtered species, the submicroscopic particle size and the sputter-etched substrate surface is responsible for strong adhesion and cohesion of the sputtered film. Presented at the first ASLE International Conference on Solid Lubrication held in Denver, Colorado, August 24–27, 1971
77 citations
TL;DR: In this article, the second and third row transition metals from groups 4 through 7 have been studied for their ability to function as solid lubricants, and it has been shown that only those with the MoS2 type structure and a minimum value of the axial ratio of lattice parameters have inherent lubricating ability.
Abstract: The disulfides and diselenides of the second and third row transition metals from Groups 4 through 7 have been studied for their ability to function as solid lubricants. These materials have similar layered crystal structures. This work has shown that only those with the MoS2 type structure and a minimum value of the axial ratio of lattice parameters have inherent lubricating ability. The minimum axial ratios for low sliding friction have been experimentally established as 1.93 and 1.96, respectively, for second and third row transition metals. A rigid sphere atomic model shows that low friction sliding cannot take place unless the axial ratio exceeds 1.87. Formation of binary solid solutions between the chalcogenides of Group 5, 6 and 7 transition metals shows that the MoS2 type structure is stabilized at an average metal group number of 6, and that good lubricating properties are obtained when the axial ratio exceeds the minimum values previously stated. Presented at the 25th ASLE Annual Meeting in Chic...
60 citations
TL;DR: In this article, direct infrared spectrophotometric evidence of interactions between lubricating oil dispersants and a zinc dialkylphosphorodithioate (ZDP) was presented.
Abstract: Direct infrared spectrophotometric evidence of interactions between lubricating oil dispersants and a zinc dialkylphosphorodithioate (ZDP) is presented. Increasing the concentration of the dispersants polyamino monoalkenylsuccinimide, barium thiophosphonate, and basic barium dinonylbenzene sulfonate in a mineral oil containing 1.2% by weight of a ZDP decreased the intensity of the phosphorus-oxygen-carbon and phosphorus-sulfur infrared bands, and caused the appearance of a new band at 668 cm−1. The dispersants barium dinonylnaphthalene sulfonate, calcium petroleum sulfonate, and alkaline petroleum sulfonate decreased the intensity of the phosphorus-sulfur bands only after the solutions had aged, and independently of dispersant concentration. It is speculated that chemical reactions cause these interactions between the ZDP and the dispersants, and that ionic metal phosphorodithioates are formed. The possibility of association, isomeric, and complexation effects is also explored. Regardless of the exact mec...
49 citations
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TL;DR: In this paper, the various equations representing special cases of boundary lubrication are examined and grouped as "models", and the study indicates that there are no serious inconsistencies, but that each model is so seriously limited in its coverage that large gaps exist in coverage.
Abstract: The various equations representing special cases of boundary lubrication are examined and grouped as “models”, The study indicates that there are no serious inconsistencies, but that each model is so seriously limited in its coverage that large gaps exist in coverage. Methods for closure of these gaps are suggested and numerically explored to a limited extent. Hope is extended that in the near future it will be possible to compute wear rates from basic physical properties without actual experimentation on the specific lubricant and surfaces. This would constitute a useful new system for machine element design. Presented as an American Society pf Lubrication Engineers paper at the ASME/ASLE Lubrication Conference held in Cincinnati, Ohio, October 13–15, 1970
36 citations
TL;DR: In this paper, a two-ball sliding tester was used to investigate the role of elastohydrodynamic film of lubricant in determining the load at which smearing occurs.
Abstract: “Smearing” or “galling” type failures similar to those which occur at sliding contacts in rolling bearings were studied using a number of lubricants in a two-ball sliding tester. The rolling speed, sliding speed, oil flow rate, ambient temperature, rate of increase in load, and ball surface roughness were found to influence the load at which smearing occurred. The results suggest that an elastohydrodynamic film of lubricant plays a major role in determining the load at which smearing occurs. This conclusion was supported by measurements of the oil film thickness using an X-ray transmission technique. Extrapolation from thermocouple measurements indicated that the onset of smearing was not characterized by a constant critical value of the maximum contact temperature. Presented at the 25th ASLE Annual Meeting in Chicago, May 4–8, 1970
33 citations
TL;DR: In this paper, the effect of metallurgical compatibility of metal pairs on their friction, wear, or adhesion was analyzed and the rank correlation coefficient was computed between the compatibility and the tribological parameter.
Abstract: An analysis has been carried out of some twelve studies in the literature describing the effect of the metallurgical compatibility of metal pairs on their friction, wear, or adhesion. In each case the rank correlation coefficient was computed between the compatibility and the tribological parameter. The correlation is zero for adhesion tests, and is positive and increases in the order static friction, kinetic friction, and wear. It is hypothesized that the correlation coefficient is highest for wear studies either because they average the influence of the largest number of individual junctions or else because the contribution of surface energy is greatest during the severe conditions of a sliding test. Presented at the 26th ASLE Annual Meeting in Boston, Massachusetts, May 3–6, 1971
24 citations
TL;DR: In this article, the authors investigated the relationship between the proportions of individual surface sites and the lubricating action of graphite and MoS2 solids and found that the proportion of basal plane surface is an important factor in the anti-wear properties of both graphite solids.
Abstract: Examination of adsorptive properties of graphite and MoS2 revealed that their surfaces are composed of two distinct sites, i.e., basal plane and edge sites, having different affinities for polar compounds and paraffmic hydrocarbons. It was therefore of interest to investigate the relationship between the proportions of the individual surface sites and the lubricating action of these solids. This was done by preparing special graphite and MoS2 powders having a high proportion of basal plane surface and comparing their lubricating properties to those of the powders having a relatively high ratio of edge to basal plane surface area. It was found that the proportion of basal plane surface is an important factor in the lubricating performance of both graphite and MoS2 and that the powders having predominantly basal plane surface have significantly better antiwear properties than the powders having a high ratio of polar to basal plane surface. The basal plane surface in MoS2 plays an exceptionally important rol...
23 citations
TL;DR: In this article, various theoretical hypotheses that have been put forward to explain the effect of the thickness of solid lubricant films on the friction between relatively sliding surfaces are described, and a new explanation of this phenomenon based upon an increasing degree of film penetration is put forward.
Abstract: The various theoretical hypotheses that have been put forward to explain the effect of the thickness of solid lubricant films on the friction between relatively sliding surfaces are described. The rise in friction that occurs with decreasing thickness when the films are very thin is discussed in detail and a new explanation of this phenomenon based upon an increasing degree of film penetration is put forward. A theoretical model to describe such a process is set up. The predicted variation of the friction made on this basis is in good agreement with existing experimental data. Experiments on a pin disc machine that were carried out to provide further evidence for checking the postulated mechanism are also described. Friction coefficient results obtained from these experiments with films of different thicknesses on surfaces of different roughnesses provide further evidence to support the given interpretation of the friction process. Explanations for certain discrepancies between the theoretical and experim...
23 citations
TL;DR: In this paper, a method has been developed for recording the elastic roll body contacts in the load zone for both radial and thrust rolling element bearings subjected to various static loading conditions, and the relationship of roll body loads with theoretical values varied, depending on angular position from the radial load plane.
Abstract: A method has been developed for recording the elastic roll body contacts in the load zone for both radial and thrust rolling element bearings subjected to various static loading conditions. Employed in this investigation were a ball bearing and four types of roller bearings which included cylindrical, needle, tapered and spherical. Inspection of the contact areas, or footprints, yields a qualitative measure of the extent of loading arc, load sharing among rolling elements, contact characteristics such as end loading and effects of misalignment. Quantitative data on individual contacts permits the determination of load and stress distributions. Summation of the vertical components of individual roll body loads agrees with the total load applied to the whole bearing, thereby demonstrating the practicability and accuracy of this technique. Correlation of roll body loads with theoretical values varied, depending on angular position from the radial load plane. Finally, this paper indicates how static stress le...
TL;DR: In this article, it was shown that Cattaneo's (2) traction distribution with two slip areas is virtually attained when one to two contact widths have been traversed.
Abstract: Two cylinders of identical purely elastic materials are pressed together with parallel axes under the action of a normal force so that a contact strip forms. The cylinders are then shifted with respect to each other, which, under the influence of dry friction, gives rise to Cattaneo's (2) traction distribution with two slip areas. Subsequently they are rolled under the influence of a constant couple, reaching eventually Carter's (3) steady state with one slip area. The question arises how the former traction distribution passes into the latter as a function of time. It is answered in the framework of a more general rolling contact problem. The problem is solved numerically under the assumption of vanishing inertial effects, and results are presented. In the problem mentioned above it is found that Carter's (3) distribution is virtually attained when one to two contact widths have been traversed. Presented at the 25th ASLE Annual Meeting in Chicago, May 4–8, 1970
TL;DR: In this paper, an analytical program was conducted to establish recommended types of gas-lubricated journal bearings for use in miniature cryogenic turbomachinery, and a novel spring mounted, three shoe, porous hydrostatic bearing was discussed in terms of design and experimental results.
Abstract: An analytical program was conducted to establish recommended types of gas-lubricated journal bearings for use in miniature cryogenic turbomachinery. Very high rotative speeds, and the limiting damping properties of gas, indicated that fractional frequency whirl is prevalent, and the most difficult problem to overcome. Of the many journal bearing types investigated, the tilting pad hydro-dynamic and porous hydrostatic journal bearings were suited to the application. A novel spring mounted, three shoe, porous hydrostatic bearing is discussed in terms of design and experimental results. A 1/2 inch diameter journal bearing is subjected to loading and speeds to 700 grams and 65,000 rpm, respectively. Excellent performance in terms of load capacity, power loss, and flow are indicated. Orbit motions of the floated bearing with respect to the supported shaft demonstrate desirable stability characteristics for the range of tests. Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE Lubr...
TL;DR: In this article, the antiwear performance of 1,20-dicarbomelhoxy-9,12-dimethyl-10,11 -dithiaeicosane is compared with that of sulfurized methyl 10-undecenoate.
Abstract: Sulfurized methyl 10-undecenoate was used as the substance typifying sulfurized fatty extreme-pressure lubricant additives. The characteristic chemical structures in sulfurized methyl un-decenoate are sulfur-bridged long-chain di-esters, of which 1,20-dicarbomelhoxy-9,12-dimethyl-10,11 -dithiaeicosane is an example. The antiwear performance of this dithio-ester with respect to hardened AISI1095 steel in a pin-and-disk apparatus was indistinguishable from that of sulfurized methyl undecenoate. Esters such as methyl laurate and 1,18-dicarbomethoxyocta-decane did not show the antiwear behavior typical of sulfurized methyl undecenoate. Organic sulfides—-di-n-octyl monosulfide, di-n-octyl disulfide, di-n-octyl tetrasulfide, di-sec-octyl disulfide, d-t-octyl disulfide—behaved much differently than sulfurized methyl undecenoate. A mixture of methyl laurate and di-sec-octyl disulfide showed the same kind of antiwear behavior as sulfurized methyl undecenoate. Presented as an American Society of Lubrication Enginee...
TL;DR: In this paper, the authors showed that adding 0.02% phosphorus to a Cu-6Sn alloy reduces the desorption temperature for paraffin oil, containing 0.2% fatty acid, by more than 60 C.
Abstract: Addition of 0.02% phosphorus to a Cu-6Sn alloy reduces the desorption temperature for paraffin oil, containing 0.2% fatty acid, by more than 60 C. This means that, in the pin and ring geometry, the load carrying capacity in the boundary lubrication regime is lowered by a factor of 2 or more. Desorption is controlled by the over-all surface temperature of the bronze, rather than by the local hot-spot temperature. The desorption temperature is not influenced by viscosity and sliding speed. At conditions below critical, wear is probably of the abrasive type and the wear rate is independent of speed. Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE Lubrication Conference held in Cincinnati, Ohio, October 13–15, 1970
TL;DR: In this article, an SAE 1113 steel pin is rubbed on a similar disc at sliding speeds up to 100 m/s and loads up to 7 kgf. Measured pin sub-surface temperatures are used to predict total surface temperatures by considering the heat flow through an idealised single asperity tip.
Abstract: Tests are described in which an SAE 1113 steel pin is rubbed on a similar disc at sliding speeds up to 100 m/s and loads up to 7 kgf. Measured pin sub-surface temperatures are used to predict total surface temperatures by considering the heat flow through an idealised single asperity tip, and from the existing theories of Jaeger, Archard and Barber. The frictional coefficient and transitions in the sliding process are shown to be related to the predicted total temperatures. Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE Lubrication Conference held in Cincinnati, Ohio, October 13–15, 1970
TL;DR: In this paper, a variety of organophosphorus and other selected compounds were studied as antiwear additives for neopentyl polyol ester lubricants on 440C stainless steel rubbing surfaces using a four-ball wear test machine.
Abstract: A variety of organophosphorus and other selected compounds were studied as antiwear additives for neopentyl polyol ester lubricants on 440C stainless steel rubbing surfaces using a four-ball wear test machine. Their effectiveness as additives was compared with that of tricresyl phosphate. Although 440C steel is relatively unreactive, it was possible to improve strikingly its wear and friction characteristics with organophosphorus additives. Some of the best results were obtained with acid phosphates. Alkyl chain length also appeared to be a significant factor. It was demonstrated that small concentrations of extraneous acidic substances are responsible for the antiwear action of phosphites at high load and that larger amounts of such acidic materials are needed as the load increases. Experiments involving addition of amines to neutralize formulations containing an acid phosphate confirmed that free acids promote antiwear action at the higher loads. Vinyl stearate and selected compounds containing chlorine...
TL;DR: In this paper, a pin-on-disk type friction machine was used to investigate the wear of copper under boundary lubrication conditions, and the wear was expressed in a wear rate equation as follows: under an apparent contact pressure lower than the critical pressure of hydrodynamic lubrication, no observable wear was found.
Abstract: A pin-on-disk type friction machine was used to investigate the wear of copper under boundary lubrication conditions. The wear of copper was found to be expressed in a wear rate equation as follows: Under an apparent contact pressure lower than the critical pressure of hydrodynamic lubrication, no observable wear was found. It was also found that the above wear rate equation was applicable to wear in which chemical reactions of the frictional surfaces were involved. However, the wear curves did not follow the equation when the oil used was chemically corrosive. The wear rate in those cases was determined by the frictional surface area or the concentration of reacting materials on the surfaces. Presented at the 26th ASLE Annual Meeting in Boston, Massachusetts, May 3–6, 1971.
TL;DR: The s-triazines as discussed by the authors are a new class of fluids developed for high temperature applications in aerospace systems, which show great potential as high temperature lubricants and energy transfer fluids for future aerospace systems.
Abstract: A new class of fluids has been developed which show great potential as high temperature lubricants and energy transfer fluids for future aerospace systems. The chemical synthesis of this class of materials, the s-triazines, is briefly described and the characterization and evaluation data are presented. These fluids show excellent thermal and oxidative stability up to 650 F and are nonflammable. They exhibit improved low temperature properties over the polyphenyl ethers and are not corrosive at elevated temperatures. Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE Lubrication Conference held in Cincinnati, Ohio, October 13–15, 1970.
TL;DR: In this article, the authors describe work in which coated abrasives are used to grind a titanium alloy (6Al-4V) using water, various soluble cutting oils, and inorganic phosphate solutions as coolants and lubricants.
Abstract: Titanium alloys designed for aerospace applications are extremely difficult to grind. Although the high strength of these alloys is a major cause of poor grindability, chemical adhesion of the titanium to the abrasive grain is also a factor contributing to poor abrasive performance. These difficulties can be alleviated by proper choice of grinding fluid. This paper describes work in which coated abrasives are used to grind a titanium alloy (6Al-4V) using water, various soluble cutting oils, and inorganic phosphate solutions as coolants and lubricants. Although some of the highly compounded commercial cutting fluids substantially increase belt efficiency, far greater improvement is obtained with solutions of tri-potassium phosphate. Straight solutions of this material have the added advantage of being moderately good corrosion inhibitors but are a nuisance because of their high pH (alkalinity). Data are presented to show that these solutions retain their effectiveness at nearly neutral pH when properly buf...
TL;DR: Sliding load history effects on friction of thin burnished films of molybdenum disulfide in vacuum were studied in this paper. But the results were limited to the case of thin films.
Abstract: Sliding load history effects on friction of thin burnished films of molybdenum disulfide in vacuum
TL;DR: Friction and wear of steels, Ti, Al, Cu and copper beryllium in sliding over hardness range of steel plates in vacuum and air as discussed by the authors, and the wear and friction and wear
Abstract: Friction and wear of steels, Ti, Al, Cu and copper beryllium in sliding over hardness range of steel plates in vacuum and air
TL;DR: In this article, an analytical study of the character and magnitude of post mechanical interface separation in elastically supported rotary face seals subjected to particular types of input excitation was performed.
Abstract: Results are reported of an analytical study of the character and magnitude of post mechanical interface separation in elastically supported rotary face seals subjected to particular types of input excitation. The seal system is approximated by lump system parameters which permit simulation of its dynamic response. Input forcing functions assigned to the mating ring include harmonic axial shaft pulsation and wobble due to misalignment. The equations of motion governing the seal carrier are solved to determine the character (stable or unstable) and magnitude (relative displacement at seal interface) of post mechanical separation for combinations of system parameters (spring constants, damping ratios, preset, inertia, etc.) and operating conditions (speed, degree of misalignment, amplitude of end play, etc.). For combinations of parameters normally encountered no unstable behavior was observed. However, a reversal of the effects of system damping between pre and post separation behavior did occur. Presented ...
TL;DR: In this article, a new technique for producing adherent solid lubricant films with full control of thickness and location is described, which has applications in fundamental studies of solid-film and extreme-pressure lubrication, and also in warm wire-drawing and other metal-forming processes.
Abstract: This paper describes a new technique for producing adherent solid lubricant films with full control of thickness and location. MoS2 and FeCl2/CrCl3 coatings are formed on Mo and Fe/Cr wires respectively by electrochemical deposition from a bath of molten LiCl/KCl, and their frictional behaviour is studied at 400 C. It is suggested that this method has applications in fundamental studies of solid-film and extreme-pressure lubrication, and also in warm wire-drawing and other metal-forming processes. Presented at the first ASLE International Conference on Solid Lubrication held in Denver, Colorado, August 24–27, 1971
TL;DR: The sliding performance of polyalkenes in rubbing contact with a metal (oxide) surface is controlled by structural order and molecular symmetry as mentioned in this paper, and the ability of the conventional (branched) polyethylene to function as a low friction contact when water is the lubricant is attributed to the presence of amorphous regions also present in the linear type.
Abstract: The sliding performance of polyalkenes in rubbing contact with a metal (oxide) surface is controlled by structural order and molecular symmetry. High density polyethylene surpasses in its overall sliding performance the substituted crystalline polyalkenes. The ability of the conventional (branched) polyethylene to function as a low friction contact when water is the lubricant is attributed to the presence of amorphous regions also present in the linear type. The erratic sliding of isotactic polybutene (and other homologs) is explained by internal friction in the rubbing interface resulting from polymorphic transitions. Crosslinking with a peroxide increases friction of polyethylene but it reduces the abrasive wear of the composites containing carbon black. The use of highly reactive channel blacks requires no free radical source and a further reduction in abrasive wear can be achieved by auxiliary crosslinking agents such as ethylene imine which reacts exothermally with the acidic surface of the carbon bl...
TL;DR: In this article, the abrasiveness of molybdenum disulfide hat has been studied on a Modified LFW-1 Tester Tester, and it was found that run-in is effective in reducing surface damage and that in some cases the effect may he enhanced by burnishing prior to test.
Abstract: The abrasiveness of molybdenum disulfide hat been studied on a Modified LFW-1 Tester Tester. Test rings, coated with a special banded solid lubricant, were rotated under load against uncoated, highly polished, steel test blocks. After each test, the block surface roughness was measured using an electronic surface comparator. Results indicate that randomly oriented platelets of MoS2 embedded in a resin, can rapidly cause severe damage to hard metal surfaces, even under relatively light loads. It Was found that run-in is effective in reducing surface damage and that in some cases the effect may he enhanced by burnishing prior to test. Burnishing was found to be effective in inhibiting blister formation. Some conclusions are drawn regarding the effects of surface orientation of MoS2 particles. These conclusions are substantiated by X-ray diffraction studies, and several scanning electron photo micrographs. Presented of the 25th ASLE Annual Meeting in Chicago, May 4–8, 1970
TL;DR: In this article, the authors present a comparison of Laminar-turbulent transition conditions and performance relations for both regimes, and present an analysis of the performance relations between two regimes.
Abstract: Bearings of 350-, 363-, and 450-square-inch area and ranging up to 31.5-inch outside diameter were tested at speeds up to 5000 rpm and at loads up to 1000 psi. Laminar-turbulent transition conditions are analyzed as well as performance relations for both regimes. Presented at the 26th ASLE Annual Meeting in Boston, Massachusetts, May 3–6, 1971
TL;DR: In this article, the deformation due to the friction of a sapphire ball, rubbing in air on the principal faces of four hexagonal metals of different lattice stacking ratio c/a: Be, Co, Zn and Cd, during the preliminary displacement is compared.
Abstract: Comparison is made of the plastic deformation due to the friction of a sapphire ball, rubbing in air on the principal faces of four hexagonal metals of different lattice stacking ratio c/a: Be, Co, Zn and Cd, during the preliminary displacement. Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE Lubrication Conference held in Cincinnati, Ohio, October 13–15, 1970
TL;DR: Sealing coefficient and leakage performance model for multiple thread rarefied gas viscoseals was presented in this paper, where the leakage performance was evaluated for a multiple thread viscoseal.
Abstract: Sealing coefficient and leakage performance model for multiple thread rarefied gas viscoseals
TL;DR: In this paper, a dual-material oil seal is designed and developed in which two or more elastomeric compounds are combined so that the product utilizes efficiently the optimum properties of each.
Abstract: Optimum performance of some radial lip-type shaft seals requires a combination of properties in the elastomer: mechanical response requirements of the contact edge are different from those of the flex-section. Since this range of behavior is not available in a single elastomer, a “dual-material” oil seal has been designed and developed in which two or more elastomeric compounds are combined so that the product utilizes efficiently the optimum properties of each. One variation of the dual-material concept is a wear-resistant, low-friction material backed by a conventional elastomer. Frictional loss measurements during operation of an oil-seal is related to the degree of lubrication in the contact area, potential temperature build-up, wear rate, and sealing efficiency; and hence, furnishes a rapidly obtainable estimate of service life and long-term performance characteristics. Laboratory data expressing the dependence of the frictional losses (power consumption, W) on lubricant viscosity, T), shaft speed, N...