摘要:

AbstractCeramic materials are often used in tribological applications because of their good mechanical properties. Silicon carbide (SiC) has a low density, high Young's modulus, high corrosion resistance, and very low friction in water. It is a very good candidate for replacing waterproof oil‐lubricated bearings in water pumps and for applications when water is used as a lubricant. In such applications the SiC dissolves very slowly in water to form silicilic acid. After running in, journal and bearing surfaces look like mirrors with very low roughness and very small friction coefficient.This paper reports on a parametric study to model the cylinder—plane configuration, which is then utilised in the specific case of SiC in water. The study was carried out in order to reduce the number of parameters and to ensure good precision of the results. The numerical model is applied to an SiC contact with a very low‐viscosity lubricant (water) using elastohydrodynamic (EHD) conditions. Multigrid techniques for the Reynolds equation and multilevel, multi‐integration methods for the elasticity equations are used to solve the EHD problem. These results are given in non‐dimensional form using the Moes parameters M and L for several velocities and loads. Comparison is made between the two‐ and three‐dimensional cases in order to assess the effects for the

ISSN:0954-0075    

DOI:10.1002/ls.3010160402

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractIn large, slow, cross‐head marine diesel engines research has increasingly shown that the lubrication regime between piston rings and cylinder liner at top dead centre is of the boundary lubrication type due to the high gas pressure, low sliding speed, and high temperature. This means that the tribological properties of piston ring, cylinder liner, and cylinder lubricant in these types of engine under boundary lubrication conditions should be considered simultaneously when friction and wear between the piston ring and cylinder liner are studied. Until now there has been no standard method to evaluate boundary lubrication performance. There are a few traditional methods used in lubricant research, but their results are not correlated with service conditions. It is important to find a suitable method to evaluate the boundary lubrication performance of lubricants at the laboratory testing stage or before the engine testing stage. The important parameters, such as sliding speed, normal load, materials of the contacting pairs, and lubricant, need all to be controlled.In this paper a systematic experimental procedure, the ‘five times heating and cooling test’, is introduced to assess lubricant properties under boundary lubrication conditions. Most of the parameters mentioned above are controlled. The model contact, of pin‐on‐plate form, is made from the actual piston and liner materials used in a large‐bore, slow, cross‐head marine diesel engine. The temperature characteristics of different blends of lubricants are investigated under boundary lubrication conditions using a pin‐on‐plate reciprocating test rig. These blends of lubricants have the same additives but different base fluids; they nevertheless fulfil the physical and chemical requirements of a real marine diesel engine. The test temperature range is from room temperature to the working temperature of the top piston ring.The experiments show that there are different temperature—friction characteristics for lubricants with different bases and the same additive package and there are also different temperature—friction characteristics during heating up and cooling down for each blend. Single‐base lubricants have more promising temperature—friction characteristics than those of a blend of a high‐viscosity base and a low‐visco

ISSN:0954-0075    

DOI:10.1002/ls.3010160403

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractAdditive packages for engine oils were prepared using PIB—succinimide combinations with different properties. PIB—succinimide‐type dispersants of various average molecular weights and dominant side effects were selected for preparing multifunctional additive combinations. A high‐molecular‐weight PIB—polysuccinimide type as viscosity‐index improver, a PIB—polysuccinimide with strong basic character as a highly effective sludge dispersant, molybdenum‐containing poly‐alkylene—polysuccinic anhydride derivatives as dispersants with complementary antifriction efficiency, and some conventional detergent, antioxidant, antiwear, and anticorrosion engine oil additives were used in engine oil compositions of various viscosity grades. The technical and economic advantages of appropriately selected and balanced additive combinations were shown by bench test results of the rheological, detergent—dispersant, and antifriction prop

ISSN:0954-0075    

DOI:10.1002/ls.3010160404

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractThe present studies highlight the applications of NMR spectroscopic techniques for unravelling the unique structural features present in base oils responsible for imparting lubricant properties. The viscosity—temperature and viscosity—pressure properties of base oils of API groups I—IV, such as viscosity, viscosity index, pour point, elastohydrodynamic film thickness, and pressure—viscosity coefficient, have been correlated with the detailed hydrocarbon composition of base oils with an emphasis on the various types of methyl branched structures. Molecular dynamics parameters, such as diffusion coefficient and energy of activation, estimated from the NMR spectral studies have provided evidence of the factors responsible for the different viscosity—temperature or viscosity—pressure characteristics o

ISSN:0954-0075    

DOI:10.1002/ls.3010160405

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractLangmuir—Blodgett (LB) films of 22‐tricosenoic acid and of 22‐tricosenoic acid polymerised in the presence of an electron beam, and in situ composite LB films of 22‐tricosenoic acid/CdS were prepared. The friction and wear behaviour of the LB films were investigated with a ball‐on‐block one‐way reciprocating friction tester. The structures and morphologies of the LB films were analysed and observed using atomic force microscopy. The wear resistance of the LB films was increased after polymerisation of the acid, and the composite LB film of 22‐tricosenoic acid/CdS showed better wear resistance because the inorganic nanocores of CdS acted to resist wear and to carry load. The LB film of the acid experienced structural changes during the f

ISSN:0954-0075    

DOI:10.1002/ls.3010160406

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractChemical software (Gaussian 98w) was used to calculate the highest occupied molecular orbital (HOMO) energy level of three phenol‐type antioxidants to evaluate their oxidation resistance performance. The conclusion drawn from the quantum calculations was that the decreasing order of the oxidation resistance effectiveness was 4,4‐methylene‐di(2,6‐di‐t‐butyl‐phenol) (T511)>2,6‐di‐t‐butyl‐4‐methylphenol (BHT)>phenol. Pressure differential scanning calorimetry (PDSC) and the rotary bomb oxidation test were also used to assess the antioxidants in a methyl oleate base oil. According to the experimental results, the oxidation resistance capability of the three antioxidants decreased in the order BHT>T511>phenol. The results indicated that the quantum calculation method could be used to screen antioxidants with regard to their oxidation r

ISSN:0954-0075    

DOI:10.1002/ls.3010160407

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractAccording to the guidelines for the molecular design of traction base fluids obtained from a previous study, more than 100 chemical compounds have been synthesised. Employing 61 naphthenic compounds whose chemical structures have been clearly identified, the optimisation of molecular structure has been studied regarding the compatibility of high‐temperature traction coefficient and low‐temperature fluidity. As a result, the requirements for molecular structures for high‐performance traction base fluids have been clar

ISSN:0954-0075    

DOI:10.1002/ls.3010160408

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractA wide range of literature has been published in the period 1950–2000 concerning emerging concepts relating to the action mechanisms of boundary lubrication additives. Some of the details 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. It has been observed that the chemical constituents of boundary lubrication additives, particularly of organosulphur and organosulphur—phosphorus origin, are very complex in nature and no comprehensive details are readily available. Regarding action mechanisms, different researchers have suggested different mechanisms for different conditions. However, information on the thermodynamics of surfaces and thermal stability of additives is not readily available. Other details, such as the effect of sliding speed, operating load, surface roughness, and material design, are not covered in this paper. 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 are continuing.In this first part, the authors examine the chemical nature of boundary lubrication additives, the surface films produced, and surface temper

ISSN:0954-0075    

DOI:10.1002/ls.3010160409

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

ISSN:0954-0075    

DOI:10.1002/ls.3010160401

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY