摘要:

AbstractThe addition of friction modifiers to lubricants has been the subject of study for a number of years. Two main models have emerged, a thick‐film and a thin‐film or monolayer model, but it is uncertain which materials and conditions produce which results. The present work, therefore, looked at whether certain additives form thin or thick films in rolling and/or rolling‐sliding contacts; the practical effect of any thick‐film formation behaviour; and the nature and structure of boundary films formed.Using ultrathin‐film interferometry, tests were performed on a rig, with two commercial friction modifiers, a copper carboxylate soap, and a dimerised unsaturated carboxylic acid, in hexadecane and in a solvent‐refined mineral oil. The results showed that both additives formed thick films in high‐pressure rolling and sliding contacts at slow speeds. However, the nature of the films is determined by temperature and speed, and under certain conditions they can

ISSN:0954-0075    

DOI:10.1002/ls.3010110402

出版商:John Wiley&Sons, Ltd    

年代:1999

数据来源: WILEY

摘要:

AbstractIt is well known1–5that the viscosity of crankcase lubricants decreases in the early stages of use due to shearing of the viscosity modifier (VM) and, depending upon the type of service, fuel dilution. This paper examines the effects of VM chemistry on the shearing process, and particularly how both high‐temperature and low‐temperature viscosities can change as a result of mechanical shear in the Kurt Orbahn injector test and during a passenger car fleet test. Commercial olefin copolymer, styrene/butadiene, styrene/isoprene, and radial isoprene polymers were included in this study, as a way of representing the major VM chemistries used in motor oils throughout the world. The rate of change of kinematic and high‐temperature, high‐shear‐rate viscosity with time, as well as low‐temperature cranking and pumping viscosity changes, were found to be characteristic of particular V

ISSN:0954-0075    

DOI:10.1002/ls.3010110403

出版商:John Wiley&Sons, Ltd    

年代:1999

数据来源: WILEY

摘要:

AbstractBelt‐drive continuously variable transmissions are already being increasingly used in Europe and Japan for small vehicles, but midsize vehicles will require greater torque capacity. This paper discusses the effect of ZDDP as an additive on increasing the traction obtained at the sliding interfaces between the elements and pulleys of a belt‐drive continuously variable transmission (B‐CVT). This effect stems from the higher friction coefficient at the sliding interfaces.Friction coefficients were measured in rig tests in which test pieces cut from actual CVT elements were slid against a disc in different types of CVT fluid (CVTF). After the tests, the adsorbed films on the specimen surfaces were investigated with electron probe microanalysis (EPMA), and compared with pieces cut from elements subjected to a high torque test conducted with the B‐CVT. The experimental results indicated that the higher friction coefficient at the sliding interfaces was due to the shearing of the tough adsorbed film. The film was blue in colour, and consisted mainly of zinc precipitated from the ZDDP a

ISSN:0954-0075    

DOI:10.1002/ls.3010110404

出版商:John Wiley&Sons, Ltd    

年代:1999

数据来源: WILEY

摘要:

AbstractSpherical diantimony trioxide SbOx(OH)ywith a particle size of 30–70 nm has been prepared using a technique known as ‘ethanol supercritical fluid drying’. The tribological properties of an SN500 oil containing these nanometric particles were measured using a four‐ball and block‐on‐ring tribotester. The wear resistance and load‐carrying capacity of the oil were higher, and its friction coefficient lower, than that of the base oil. An excessive nanometric particles content was found to be disadvantageous to the load‐carrying capacity of the oil. The spherical nanometric diantimony trioxide appears to work by deposition on the rubbing surfaces and through the rolling action of the sphe

ISSN:0954-0075    

DOI:10.1002/ls.3010110405

出版商:John Wiley&Sons, Ltd    

年代:1999

数据来源: WILEY

摘要:

AbstractAtomic absorption spectroscopy is widely used to determine the metal content, especially of zinc, calcium, iron, and copper, in new and used multigrade oils. Many methods involve dilution of the sample with kerosene followed by aspiration into the atomic absorption. However, results indicate that such methods are subject to matrix interferences, the factors most influencing such interferences being: the concentration of viscosity index improver incorporated into the multigrade oil formulations; chemical structure of the viscosity index improver; the molecular weight of the viscosity index improvers; and the viscosity of the solvent used.Regression equations for some commercial viscosity index improvers have been established, to permit correction of the concentrations of zinc, calcium, iron and copper measured in new and used multigrade oils.

ISSN:0954-0075    

DOI:10.1002/ls.3010110406

出版商:John Wiley&Sons, Ltd    

年代:1999

数据来源: WILEY

ISSN:0954-0075    

DOI:10.1002/ls.3010110401

出版商:John Wiley&Sons, Ltd    

年代:1999

数据来源: WILEY