摘要:

AbstractIt is widely acknowledged that the process of surface film formation by tribological additives is very complex, because even saturated hydrocarbons — as major components of lubricating oils — undergo chemical changes under boundary lubrication conditions. To gain a better understanding of the tribochemical changes of paraffinic hydrocarbons, research was carried out using n‐hexadecane, which is widely used as a low‐viscosity model base oil. It has been hypothesised that the interactions between the products of n‐hexadecane triboreactions and steel surfaces are mostly initiated by the mechanical action of the system. Wear tests were performed, using a pin‐on‐disc machine. Fourier transform infrared microspectrophotometry and X‐ray photoelectron spectroscopy were used to analyse the wear tracks on the steel discs. Based on the analytical data obtained, a model of boundary film formation from aliphatic hydrocarb

ISSN:0954-0075    

DOI:10.1002/ls.3010160202

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractThe hardness of various types of soot produced by heavy‐ and light‐duty diesel engines of European, Japanese, and North American designs was measured by low‐loss electron energy‐loss spectroscopy (EELS). No clear general trend can be established that shows heavy‐duty diesel engine soot is necessarily harder than light‐duty diesel engine soot. The variation in hardness among individual soot particles produced by the same diesel engine can be as large as differences between the hardest soot particles produced by heavy‐duty diesel engines and the softest soot particles produced by light‐duty diesel engines. There are heavy‐duty diesel engines that can produce soot that is softer than that produced by some light‐duty diesel engines and vice versa. Nevertheless, the hardness of all types of soot studied is close to the range of hardness of metal engine parts. Thus, the results indicate that soot is hard enough to abrade some

ISSN:0954-0075    

DOI:10.1002/ls.3010160203

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractOil‐soluble metallic sulphonate detergents have been extensively used in automobile lubricants to keep engines clean and to extend their useful life. Calcium alkylbenzene sulphonate is widely used in the lubricant industry as a detergent. However, the authors have discovered that, uniquely, linear sulphonate detergents can play another role in lubricants, namely to depress the pour point of mineral oils. The authors have studied the relationship between the molecular structures of sulphonate detergents and pour point depression, and it has been found that, in order for a sulphonate detergent to be a pour point depressant (PPD), it must have a linear hydrocarbon tail. Other factors, such as the metal type, e.g., Ca or Mg, and the degree of overbasing, are not critical for pour point depression activity. A model is proposed to explain why sulphonate detergents with linear hydrocarbon tails can function as pour point depressant

ISSN:0954-0075    

DOI:10.1002/ls.3010160204

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractThe influence of lubricating oil on the torque capacity and the efficiency of a continuously variable transmission (CVT) of metal V‐belt type were experimentally investigated using a commercial CVT unit with a belt assembly and pulley. In order to analyse the friction characteristics of each of the contacting parts in the CVT, a block‐on‐disc type friction testing machine was used. The maximum torque capacity between the belt and pulley in the actual CVT correlated with the friction coefficient under high contact pressure (200 MPa) and relatively high sliding velocity (0.1 m/s) on the friction testing machine. The transmission efficiency decreased as the load decreased. The maximum difference in the efficiency between all the commercial automotive transmission and CVT fluids tested reached 6%. It was found that the requirements for the efficiency of transmission at a lower load were in contradiction with the maximum torque cap

ISSN:0954-0075    

DOI:10.1002/ls.3010160205

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractHeavily loaded machine elements, such as gears, usually operate in the mixed lubrication regime. Surface roughness has a significant effect on the pressure distribution, the subsurface stress field, and the friction coefficient. Based on the superposition of a dry rough and a fully flooded smooth contact, a mixed lubrication model has been developed. The roughness profile is assumed to be known. Surface deformation is calculated by taking into account the pressure distribution that is built up by asperity contacts, asperity interactions, and lubricant flow. Thermal and sliding effects are incorporated into the analysis. Non‐Newtonian lubricant behaviour is considered by using a power‐law rheological model. The pressure distribution, subsurface stress field, and friction coefficient were calculated from the model at several points along the contact path for an FZG type C gear pair. It was shown that a significant part of the load is carried by the contacting asperities. The position of the maximum shear stress is very close to the surf

ISSN:0954-0075    

DOI:10.1002/ls.3010160206

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractComparative tests of more than 15 detergents (calcium sulphonates and phenates) of different basicity and dispersants (succinimides) were carried out using laboratory test methods. The effectiveness of the detergent and dispersant action of the test additives, their thermal, hydrolytic, and colloidal stability, and their influence on the antioxidant properties of engine oils were evaluated. The results obtained showed that it is possible to differentiate additives of various types, and demonstrated the relative efficiency of additives belonging to the same class. The effectiveness of certain additive packages was evaluated using a new approach: in addition to the laboratory methods, the retention of the dispersing ability of additive packages was evaluated in previously oxidised additivated engine oils. This allowed the efficiency of engine oils of different categories to be characterised.

ISSN:0954-0075    

DOI:10.1002/ls.3010160207

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractThe antioxidative actions of zinc and molybdenum dithiophosphates and their mixtures were evaluated using the RBOT (rotary bomb oxidation test) and the ISOT (Indiana stirring oxidation test). The results showed a synergistic effect on the antioxidative action with certain mixtures of the additives in mineral oil. FTIR spectra indicated the presence of some oxidation products and the degradation of the additives in the additive‐containing oil

ISSN:0954-0075    

DOI:10.1002/ls.3010160208

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractTribochemistry, the chemistry of interacting surfaces under the influence of a lubricant, helps in the appropriate selection of suitable lubricant additives for specific uses. Modern lubricants are usually formulated from a range of petroleum base oils or synthetic fluids incorporating a variety of chemical additives for performance enhancement. Extreme‐pressure (EP) and anti‐wear (AW) additives are used extensively in lubricants for hypoid gears and metal cutting and forming operations to reduce wear, modify friction, and prevent scuffing of moving metallic parts.The present paper includes the synthesis and the evaluation of the tribological properties of 0.5% (w/v) solutions of some zinc bis‐(alkyl/dialkyl/alkylaryldithiocarbamates) in paraffin oil using 12.7 mm diameter steel bearing ball specimens in four‐ball tests. All the synthesised zinc dithiocarbamate additives in general, and zinc bis‐(morpholinodithio‐carbamate) (A4) in particular, exhibited good AW, EP, and friction‐reducing properties. Additive A4especially gave low values of wear‐scar diameter and coefficient of friction at higher loads and higher values of load wear index and flash temperature parameter during EP tests (ASTM D 2783) and afforded lower values of wear‐scar diameter in a one‐hour wear test (ASTM D 2266–67).The surface topography of the wear‐scar matrix of the used ball specimens was investigated by scann

ISSN:0954-0075    

DOI:10.1002/ls.3010160209

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

ISSN:0954-0075    

DOI:10.1002/ls.3010160201

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY