摘要:

AbstractA theoretical hydrodynamic lubrication analysis of piston rings is presented. A numerical scheme is developed to solve the Reynolds' equation and the load equilibrium equation simultaneously. The hydrodynamic effects are examined in detail by considering solutions to the problem of lubricating the top compression ring in a two‐stroke diesel engine. The minimum film thickness is computed throughout a complete cycle. The pressure profiles and film shapes at different crankshaft angles are presented. In the method proposed, the camtation boundary condition within the lubricated conjunction is included in the analysi

ISSN:0954-0075    

DOI:10.1002/ls.3010100402

出版商:John Wiley&Sons, Ltd    

年代:1998

数据来源: WILEY

摘要:

AbstractA theoretical model is presented to calculate the lubricant film thickness in an unsteady hydrodynamic lubrication of cup‐shaped products to be formed by the ironing process. The model covers the development of hydrodynamic lubrication in various phases of the ironing process. The model provides equations for estimating the lubricant film thickness for each phase.Experiments were conducted to study the effect of lubricant viscosity on die expansion and punch force in making cup‐shaped products by the ironing process. It was found that the die expansion varied between unlubricated and lubricated cups and depended on the lubricant viscosity. The film thickness was estimated from the difference between the increased die/punch clearance, which was calculated from the expansion, and the lubricated cup wall thickness. The theoretical film thickness was compared with the estimated film thickness based on the die expansion measurem

ISSN:0954-0075    

DOI:10.1002/ls.3010100403

出版商:John Wiley&Sons, Ltd    

年代:1998

数据来源: WILEY

摘要:

AbstractThe effect of the nature and alkyl chain length of zinc dialkyldithiophosphate (ZDDP) (R = C4to C8) on its interactions with polyisobutenyl succinimide (PIBS) has been investigated using31P‐NMR and infrared spectroscopy.31P‐NMR spectra of ZDDP in the presence of PIBS showed both broad (35–850 Hz) and sharp (50–100 Hz) resonance signals due to different modes of interaction, mainly cluster formation and specific complexation, respectively. Single‐ended mono‐PIBS exhibit stronger interactions compared to the double‐ended bis‐PIBS. The proportion of sharp signals due to specific complexes in31P‐NMR spectra of ZDDP—PIBS blends are in the order: C8>C5>C4+C8>C6= aryl ZDDP. The effect of PIBS concentration on the strength of complexes ha

ISSN:0954-0075    

DOI:10.1002/ls.3010100404

出版商:John Wiley&Sons, Ltd    

年代:1998

数据来源: WILEY

摘要:

AbstractIn the present work, we report on the analysis of the deterioration of lithium greases used in rolling‐element bearings by X‐ray diffractometry (XRD), X‐ray fluorescence spectrometry (XRFS), and atomic absorption spectrometry (AAS). These techniques give reproducible, reliable data with which to establish the severity of deterioration of greases recovered from the active zone of bearings. XRD appears more suitable for diagnosing quickly the chemical changes that have occurred in the soap residue of greases, even in small quantity, than other analytical and performance evaluation techniques.Fresh lithium greases, their chemical composition, and the formation of new compounds in the greases have been investigated after use in rolling‐element bearings run in the presence of electric fields, and also under pure rolling friction conditions without electric fields on a roller‐bearing test rig. The deteriorated greases recovered from various motor bearings have also been analysed and the results are compared with those for the greases from the test bearings.X‐ray diffraction analysis shows that the chemical composition of the soap residue of the fresh lithium grease, lithium stearate (C18H35LiO2), does not change in bearings operated without the effect of electric fields, under pure rolling friction. However, lithium iron oxide (Li5FeO2) peaks were detected after prolonged operation of the bearings. On the other hand, under the influence of electric fields, the chemical composition of the grease changed to lithium palmitate (C16H31LiO2), and peaks of gamma lithium iron oxide (Γ‐LiFeO2) and lithium zinc silicate (Li3.6Zn0.2SiO2) were detected. The surface of the bearings was found to be corroded after operation under electric fields. AAS showed a considerable increase in the lithium percentage, and lithium carbonate and lithium hydroxide in the used greases in aqueous solution, compared to the fresh greaseThe investigations reported in this paper, together with study of damaged/corrugated bearing surfaces, offer potential in diagnosing the cause of bearing failure in teh presence of electric fields, and in establishing the severity of deterioration of the lithium greases used i

ISSN:0954-0075    

DOI:10.1002/ls.3010100405

出版商:John Wiley&Sons, Ltd    

年代:1998

数据来源: WILEY

摘要:

AbstractThe viscometric properties of multigrade oils containing base stocks with increased aromatic content have been studied. Various types of viscosity index improvers (VIIs) have been incorporated in these formulations. Viscosity measurements were carried out over a wide temperature range (from −10°C to 150°C).The results show that increasing the aromaticity of blends induces a greater thickening effect with all types of VIIs incorporated, but by different magnitudes. This thickening effect is more pronounced at low temperatures. At high temperature and high aromaticity, the VIIs tended to acquire high swelling behaviour, which serves to mask the differences between them.Limited changes were noticed for the viscosity index, thickening tendency, and specific viscosity of the blends tested. The shear stability of the VIIs was found to decrease with the increasing aromaticity of the blends. Such behaviour can be attributed to the swelling of the VIIs and the increase in their molecular volume, which consequently facilitated their shear

ISSN:0954-0075    

DOI:10.1002/ls.3010100406

出版商:John Wiley&Sons, Ltd    

年代:1998

数据来源: WILEY

摘要:

AbstractThe effect of additive chemistry on the surface fatigue of gears was investigated using an FZG gear tester and fluids based on an API GL‐5 grade gear oil. Surface fatigue lives were determined as a function of load and additive chemistry. At 1.52 GPa, the removal of the primary extreme pressure (EP) additive from the fully formulated gear oil decreased the fatigue life of gears slightly (4%). However, the removal of the primary antiwear (AW) additive decreased the fatigue life of gears significantly (83%). At 1.86 GPa, the removal of the EP additive from the fully formulated gear oil decreased the gear fatigue life by 27%. However, the removal of the primary AW additive decreased the fatigue life of gears significantly (75%). Micro‐pitting was the dominant surface morphology in the dedendum of the gears tested with two oils at load stage eleven: one using the complete additive package, and a second where the EP additive had been removed. However, spalling was the primary failure mode of gears tested without an AW additive, independent of whether an EP agent was present. Surface analysis of the pinion gears showed the formation of a mixed phosphate/phosphite—oxide layer on the surface of gears tested with fluids containing an AW additive. Formation of this layer seems to be the key to a long fatigue

ISSN:0954-0075    

DOI:10.1002/ls.3010100407

出版商:John Wiley&Sons, Ltd    

年代:1998

数据来源: WILEY

ISSN:0954-0075    

DOI:10.1002/ls.3010100401

出版商:John Wiley&Sons, Ltd    

年代:1998

数据来源: WILEY