摘要:

Optical interferometry is used to measure the elastohydrodynamic (EHD) film thickness associated with artificially produced, nonsmooth surfaces. The nonsmooth surfaces are produced by modifying the surfaces of highly-polished balls with irregularities in the form of multiple grooves and dents. By closely spacing these irregularities, it is possible not only to produce depressions on the surface of the balls but also to generate pseudo asperities. The average “roughness” wavelength of this artificially-produced, nonsmooth surface approximates the average fundamental roughness wavelength, found on surfaces of some mechanical elements operating under concentrated contact. By comparing the measured film thickness profiles to the stylus traces of the irregularities, it is possible to observe the local deformations associated with micro-EHD pressure generation. In both pure rolling and pure sliding conditions, the artificially-produced “asperities” are deformed and complete separation exists between them and the mating surface. Such findings demonstrate the importance of local surface topography and resulting micro-EHD effects on the film thickness between rough surfaces in concentrated contact. In addition, sliding data are presented which demonstrate a severe constriction, caused by the irregularities, at the exit of the Hertzian region.Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Dayton, Ohio, October 16–18, 1979

ISSN:0569-8197    

DOI:10.1080/05698198108982992

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

A series of experiments describing the wear of steel rollers during lubricated pure rolling contact are presented. A four-roller machine is used for the experiment; the velocity difference between the mating rollers is maintained equal to zero, while the surface roughness and oil film thickness are varied. Even under the lubricated pure rolling condition, a finite amount of wear is observed when the oil film thickness is comparable to or less than the resultant surface roughness. A common, feature is found in the wear characteristics when either the surface roughness or oil film thickness is varied: the effective surface roughness, defined as the difference between the resultant roughness and the oil film thickness, is found to correlate with both the amount of wear and strain hardening. Results are discussed from a mechanical point of view that wear is a phenomenon of fracture in surface layer resulting from repetition of stresses around contact points.Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Dayton, Ohio, October 16–18, 1979

ISSN:0569-8197    

DOI:10.1080/05698198108982993

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The leak rates through shaft seals with large pressure drops were simulated using gaseous hydrogen, or nitrogen, flowing through an annulus with a nonrotating centerbody. The flows were choked. For concentric or eccentric position of the rotor and parallel or convergent tapered flow passages, data and analysis revealed that mass flux or leak rate can be determined from a relation whose normalizing parameters depend on the thermodynamic critical constants of the working fluid and an average flow area expressed in terms of the inlet and exit cross-sectional areas. Using these normalized relations, the flow data for parallel and three convergent, tapered, shaft-seal configurations are in good agreement. Generalization to any simple gas or gas mixture is implied and demonstrated in part.Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Dayton, Ohio, October 16–18, 1979

ISSN:0569-8197    

DOI:10.1080/05698198108982994

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Using linearized turbulent lubrication theory of Ng and Pan, the modified Reynolds equation has been solved by finite element method using Galerkin's technique. Static and dynamic performance characteristics of the noncircular (two-lobe) bearings have been studied, both for laminar and turbulent flow, in terms of load support, oil flow, fluid film stiffness coefficients, damping coefficients, and critical mass for various Reynolds numbers.

ISSN:0569-8197    

DOI:10.1080/05698198108982995

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Current emphasis on fuel economy has evoked the desire to reduce lubricant viscosity both to improve fuel mileage and make starting easier with lighter starter systems. The present study was conducted to determine the effect of viscosity on wear under conditions associated with boundary lubrication. Measurements were obtained in a laboratory test designed to simulate the camshaft-lifter contact in an automobile or light truck engine. Viscosity reduction was shown to have a profound effect on wear once a critical viscosity had been reached. In the simulated camshaft-lifter contact, wear prevention appears to be due to a mixture of localized elastohydrodynamic lubrication and surface films formed from the antiwear additive. Loss of either results in excessive wear. The break in the wear-viscosity relationship occurred at 4–5 cSt @ 100 °C. Since this viscosity corresponds to the low end of the SAE 10 grade, it is possible that a 7-1/2W or 5W oil could result in excessive wear. These results suggest that any proposed low viscosity oil should undergo careful testing for its wear properties.Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Dayton, Ohio, October 16–18, 1979

ISSN:0569-8197    

DOI:10.1080/05698198108982996

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Effects of melamine-cyanurate (MCA) in liquids and in greasel compounds on load-carrying capacity, wear rate and coefficient of friction were examined. It was found that MCA was effective in improving the lubricative properties of some kinds of carrier. It especially improved the load-carrying capacity when added in water and was effective in reducing the wear of brass specimen. The effects of MCA largely depended on the kinds of carrier material and bearing specimen material.Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Dayton, Ohio, October 16–18, 1979

ISSN:0569-8197    

DOI:10.1080/05698198108982997

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Hydrodynamic effects in end-face seals with diametral tilt and coning are analyzed. A closed-form solution for the axial separating force and the restoring and transverse moments is presented that covers the whole range from zero to full angular misalignment at various degrees of coning. Both low-pressure seals with cavitating flow and high-pressure seals with full fluid film are considered. The effect of coning is to reduce the axial force and the restoring and transverse moments compared to their magnitude in flat-face-seals. Strong coupling between diametral tilt and transverse moment is demonstrated. This transverse moment which is entirely due to hydrodynamic effects can be the source of dynamic instability in the form of seal wobble.Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Dayton, Ohio, October 16–18, 1979

ISSN:0569-8197    

DOI:10.1080/05698198108982998

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Usually the lubricating effectiveness of loud-carrying additives in mineral oils is tested by measuring friction and wear of the lubricated machine elements. In most cases, these additives react with the metallic surface under the influence or frictional heating forming a complex film on the surface. This wear- and friction-reducing layer is continuously rubbed off and rebuilt.

ISSN:0569-8197    

DOI:10.1080/05698198108982999

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The oil-soluble degradation products formed in heated samples of oil containing zinc di(n-, iso- or s-butyl)dithiophosphate (ZDTP) additives have been identified using1H and31P nuclear magnetic resonance spectroscopy. The final degradation product in each case is S,S,S-trialkyltetrathiophosphate, SP(SR)3. The intermediate degradation products are O,S,S-trialkyltrithiophosphate, SP(SR)2(OR) and O,O,S-trialkyldithiophosphate, SP(SR)(OR)2. The rate of thermal degradation of the ZDTPs follows the order s-butyl > > n-butyl > isobutyl. A white, noncrystalline precipitate is formed in the heated oils which is rich in zinc and oxygen and low in phosphorus and sulfur compared with the original ZDTP.

ISSN:0569-8197    

DOI:10.1080/05698198108983000

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

A mechanism for the thermal decomposition of zinc dialkyldithiophosphate additives has been proposed that accounts for the major degradation products and their dependence on the nature of the alkyl group. The proposed mechanism generally follows well-known rules of phosphorus chemistry. The major points are as follows.

ISSN:0569-8197    

DOI:10.1080/05698198108983001

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor