摘要:

AbstractElectrorheological (ER) fluids exhibit changes in their rheological behaviour in the presence of an external electric field. Research and development activities related to ER fluids and their applications have increased dramatically during the last few decades. If commercialised, ER fluids could have a significant impact on hydraulic equipment, and be utilised in the automotive, marine, aerospace, robotics, and machinery industries. The objective of the present study is to demonstrate the feasibility of using ER fluids to produce ‘smart’ lubricants that can control friction and wear of sliding components. The ER lubricant effect is demonstrated using a unique test machine that utilises hydrostatic lubrication. It is found that the friction torque increases by as much as 30% when a voltage of 2000 V is applied to an ER fluid in the newly developed test mach

ISSN:1354-4063    

DOI:10.1002/tt.3020110302

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractThe choice of an appropriate low‐friction coating for an industrial application is generally a difficult task. As many parameters are involved and are often unknown, selection criteria are hard to define. In order to elucidate the case of fretting conditions, a simulator has been used to reproduce the degradation mechanisms observed for real situations. Numerous experiments performed with this machine permit one to define endurance life criteria. The evolution of the life observed has been analysed as a function of the contact pressure and the film thickness. Using a Wöhler approach, endurance curves have been plotted that give useful information for selecting appropriate coatings. As other parameters may be of some interest, performance indices have been associated with them, and the results can be presented on a multi‐axis (polar) dia

ISSN:1354-4063    

DOI:10.1002/tt.3020110303

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractColloidal dispersions of calcium carbonate stabilised by overbased sulphonates are used as lubricant additives to provide detergency, remove acidity, and prevent wear. In the present work various overbased sulphonate compounds have been analysed using X‐ray diffraction (XRD). The amorphous overbased sulphonates studied displayed broad diffraction patterns while the crystalline overbased sulphonates gave well‐defined diffraction patterns, correlating with the particle size. The XRD distances of the series of Mg, Ca, and Ba overbased sulphonates shifted to greater values and displayed a clear correlation (r = 0.98) with the ionic radius of the cations u

ISSN:1354-4063    

DOI:10.1002/tt.3020110304

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractMetal‐free amorphous carbon (a‐C:H) coatings with 15% hydrogen were deposited on bearing steel surfaces. The friction and wear performance of these specimens was characterised in oscillating sliding tests with a ball‐on‐flat geometry. Balls of four ceramic and four metallic materials were investigated in tests at room temperature. Special attention was paid to the effect of moisture by testing in dry, normal, and moist air. The effect of water vapour on the friction and wear of the a‐C:H coatings was quite different for the different counterbody materials. The wear was in all cases very low, with a coefficient of wear below 10−7mm3/N m for most cases. The coefficient of friction was also very low, between 0.04 and 0.12 for most of the tests. The smallest wear and friction coefficients were found for oxide ceramics, while during tests against SiC and Si3N4the coating was worn through during the test. The effects of counterbody material and the humidity of the surrounding air are discussed in terms of friction and wear

ISSN:1354-4063    

DOI:10.1002/tt.3020110305

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractThe long‐term thermo‐oxidative stability of lubricants and greases is a prerequisite to meet today's ‘stay in grade’ and extended drain interval requirements. To achieve this goal, there is a need for a better understanding of thermo‐oxidative lubricant degradation and of how antioxidants can affect this process. In this paper a two‐stage degradation model is discussed. Primary degradation leads to the formation of very reactive species such as radicals and peroxides. These are the precursors for generating secondary degradation products, such as oligomers, sludge, or deposits. By applying the theory of reaction kinetics and the Arrhenius law, quantitative correlations may be derived between oxidation induction time (OIT) and temperature, and between OIT and antioxidant treat level. Pressurised differential scanning calorimetry (PDSC) data confirm these theoretical findings and demonstrate the benefit of the addition of aminic antioxidants in comparison with high‐molecular‐weight hindered phenol

ISSN:1354-4063    

DOI:10.1002/tt.3020110306

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractThe concept and principles of the phosphorus emission index (PEI) were introduced during 2002. This paper reviews the background of the benefits and concerns regarding phosphorus additives. In particular, the paper focuses on the two factors until recently assumed important in phosphorus volatility and catalyst contamination: oil volatility and initial phosphorus concentration.Studies of Selby—Noack data on 1300 oils collected in 1999 and 2000 by the Institute of Materials showed the invalidity of the two assumptions and this led to the concept of the PEl. Further studies in conjunction with a field taxi study by the Ford Motor Company to determine the correlation of the PEl with catalyst contamination not only showed correlation, but also proved that phosphorus volatility was independent of either oil volatility or fresh oil phosphorus levels. Rather, phosphorus volatility was, as earlier predicted, found to be highly dependent on its chemistry and the chemistry of other additives. Engine oil formulation using the PEl technique should markedly reduce phosphorus volatility and resultant catalyst contaminatio

ISSN:1354-4063    

DOI:10.1002/tt.3020110307

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

ISSN:1354-4063    

DOI:10.1002/tt.3020110308

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

ISSN:1354-4063    

DOI:10.1002/tt.3020110309

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

ISSN:1354-4063    

DOI:10.1002/tt.3020110301

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY