摘要:

AbstractThis paper reports on the influence of a polymer additive on the traction behaviour of a mineral oil investigated using a two‐disc machine at different temperatures and contact pressures. A semi‐empirical approach was used for determining the effective lubricant rheological parameters ‐ the elastic shear modulus, the viscosity of the lubricant, and the limiting and Eyring stresses ‐ in elastohydrodynamic contacts. Using this approach, the effect of polymer concentration on the rheological parameters that appear in both the Johnson‐Tevaarwerk and Bair‐Winer models was quantified. The influence of operating conditions, such as pressure, oil temperature, and polymer concentration, on the traction coefficient, limiting shear stress (from the Bair‐Winer model), Eyring stress (from the Johnson‐Tevaarwerk model), shear modulus, and apparent viscosity was al

ISSN:0954-0075    

DOI:10.1002/ls.3010170102

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractThe effect of dispersed soot in engine oils is an increasingly important issue in terms of both engine durability and fuel efficiency. Using carbon black as a soot analogue, a study has been carried out to investigate the main factors that determine the impact of soot on friction and ZDDP film formation in formulated oils. It has been found that dispersed carbon black can rapidly remove ZDDP reaction films by abrasion. However, this removal can be prevented or limited by the choice of an optimal dispersant additive.

ISSN:0954-0075    

DOI:10.1002/ls.3010170103

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractThe flow of a micropolar fluid in the clearance of a curvilinear hydrostatic thrust bearing in the presence of a cross magnetic field was considered. By solving the equations of motion for the orthogonal curvilinear coordinate system, a formula describing the pressure distribution was obtained. Plane and spherical thrust bearings were considered as examples.

ISSN:0954-0075    

DOI:10.1002/ls.3010170104

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractIn view of the increasing awareness of the need for environmental protection, it is considered important to have more low‐ or non‐phosphorus additives in engine oils. To this end, molybdenum polyisobutenyl succinate (MoPIBS) was synthesised and its structure investigated using spectroscopy. The antiwear and friction‐reducing behaviour of MoPIBS as an oil additive was investigated and compared to that of zinc dialkyldithio‐phosphate (ZnDDP) using a four‐ball tester. The results indicated that MoPIBS in white oil exhibits very good antiwear and friction‐reducing properties, better than those of ZnDDP, but that the load‐carrying capacity is poorer than that of ZnDDP. The worn surfaces were investigated using Auger electron spectroscopy (AES) and X‐ray photoelectron spectroscopy (XPS). It was found that the boundary lubrication film on the worn surfaces was mainly composed of MoO3and Fe2O3, which contributed to improving the tribological properties of MoPIBS as an additi

ISSN:0954-0075    

DOI:10.1002/ls.3010170105

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractLanthanum dialkyldithiophosphate (LaDDP) was synthesised. The tribological properties of a combination additive of LaDDP and an organo‐borate (OB) in oil were evaluated with a four‐ball test machine. The results show that the combination of LaDDP and OB gives better load‐carrying capacity and anti‐wear and friction‐reducing properties than the individual components. Rubbed surfaces after the friction tests were investigated using X‐ray photoelectron spectroscopy, Auger electron spectroscopy, and microhardness testing. The results indicate that a boundary film is composed of deposit films (including La2O3and B2O3), chemical reaction films (including FeSO4, FePO4, and FeS), and a tribodiffusion layer (including La and B). Lanthanum can promote the decomposition of OB and the tribodiffusion of boron. From a mass spectroscopy analysis a tribochemical mechanism i

ISSN:0954-0075    

DOI:10.1002/ls.3010170106

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractA wide range of literature hs been published in the period 1950–2000 concerning emerging concepts of the action mechanisms of boundary lubrication additives. Some aspects of these additives in terms of chemical nature, surface adsorption, surface film generation, thermal stability, thermodynamics of contact surfaces, and rise in surface temperature, as reported in this literature, are reviewed in the present paper.Part I of this paper appeared inLubrication Science, 16, 4 (2004) 405–19.It has been observed that the chemical constituents of boundary lubrication additives, particularly of organosulphur and organo‐sulphur‐phosphorus origin, are very complex in nature and no comprehensive details are readily available. Regarding action mechanisms, researchers have suggested different mechanisms for different conditions. However, information on the thermodynamics of surfaces and thermal stability of additives is not easily obtainable. Other details, such as the effect of sliding speed, operating load, surface roughness, and material design, are not covered here. Overall, the literature reveals that attempts to correlate additive characteristics with boundary lubrication activity have met with limited success, and efforts aimed at achieving ever‐increasing performance levels continue.In the first part, the authors examined the chemical nature of boundary lubrication additives, surface films, and surface temperature. In this second part, they look at thermal stability, and antiwear and extreme‐pressu

ISSN:0954-0075    

DOI:10.1002/ls.3010170107

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractFriction tests simulating cam follower sliding conditions were conducted using a pin‐on‐disc test rig. In the case of SAE 5W‐30 class engine oil, the friction coefficient of the combination of steel pins sliding on a steel disc increased from 0.11 to 0.12, while that of steel pins sliding on a diamond‐like carbon (DLC)‐coated disc decreased from 0.12 to 0.10. For 5W‐20 oil containing the friction modifier MoDTC (molybdenum dithio‐carbamates), the friction coefficient of steel pins sliding on a steel disc decreased markedly from 0.12 to 0.04. In contrast, that of steel pins sliding on a DLC‐coated disc decreased more moderately, from 0.11 to 0.08. In both cases, Zn, P, S, and Mo elements derived from ZDDP (zinc dialkyldithiophosphate) and MoDTC additives were not detected on the DLC‐coated disc, while these elements were detected on the steel disc and pins using electron probe microanalysis and X‐ray photo‐electron spectroscopy surface analysis. It appears that a tribochemical reaction film did not form on the DLC material due to its inactive chemical properties. Therefore, an increase in friction due to the formation of the film derived from ZDDP and a decrease in friction due to the formation of the film derived from MoDTC were clearly suppressed in the case of the steel pins sliding on the DLC‐coated disc. It is thought that the tribo‐chemical reaction film was instrumental in reducing friction substantially. The lateral force of the film formed on the steel disc was then measured using an atomic force microscopy lateral force microscopy test. The lateral force of the film resulting from the 5W‐30 oil was much higher than that of the film formed from the 5W‐20 oil with MoDTC. This result coincided well with the results of the friction tests. Judging from these results, it is thought that the high friction coefficient observed for the steel pins on the steel disc for the 5W‐30 oil was caused by the higher shear strength of the film formed from ZDDP. On the other hand, the very low friction coefficient observed for the steel pin‐steel disc combination for the 5W‐20 oil was presumably caused by the formation of a solid Mo

ISSN:0954-0075    

DOI:10.1002/ls.3010170108

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractThe tribological behaviour of a rare earth naphthenate (REN) as a lubricant oil additive in VG26 white oil and the complexes of REN and organo‐sulphur or organo‐phosphate compounds have been evaluated with a four‐ball friction and wear tester. The chemical features and elemental composition of the boundary lubricating film were examined by means of Auger electron spectroscopy (AES) and X‐ray photoelectron spectrometry (XPS). The results show that REN exhibits good antiwear, load‐carrying, and friction‐reducing properties in the base stock. When 2.0% REN is added, the wear‐scar diameter value reduces to 54.7% of that for the base stock alone and the maximum non‐seizure load increases 2.95 times. A synergistic effect is found for the load‐carrying capability of the complex of REN and organo‐sulphur while poor compatibility is exhibited for the complex of REN and organo‐phosphate. The analytical results of AES and XPS indicate that the good performance of REN is attributable to the formation of a boundary lubricating film mainly composed of naphthenic acid, rare earth oxide, and complexes of rare earth metals, which is formed on a rubbed surface when lubricated by oil contai

ISSN:0954-0075    

DOI:10.1002/ls.3010170109

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

ISSN:0954-0075    

DOI:10.1002/ls.3010170101

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY