Lubrication Science 

About: Lubrication Science is an academic journal published by Wiley-Blackwell. The journal publishes majorly in the area(s): Lubrication & Lubricant. It has an ISSN identifier of 0954-0075. Over the lifetime, 983 publications have been published receiving 10989 citations.

Low- and zero-sulphated ash, phosphorus and sulphur anti-wear additives for engine oils

Abstract: Modern engine lubricant specifications include compositional constraints in terms of the permitted level of sulphated ash, phosphorus and sulphur (SAPS). This necessitates a reduction in the concentration of the additive zinc dialkyldithiophosphate (ZDDP) used in engine oils, and there is currently great interest in identifying anti-wear additives that contain low or zero SAPS to partially or wholly replace ZDDP. This paper reviews the main chemical classes that are reported in the literature as potential low- or zero-SAPS anti-wear agents. There are many such possible additives, although none appears to be quite as versatile as ZDDP. Instead, combinations of anti-wear and extreme pressure additives are likely to be employed in the future. The literature reveals a strong imbalance in the amount and depth of research carried out on the various additive types, with a great deal of research on a few classes of additives and very little recent work on most others. Copyright © 2007 John Wiley & Sons, Ltd.

An evaluation of antioxidants for vegetable oils at elevated temperatures

Abstract: The antioxidant efficacy of various oxidation inhibitors in low erucic acid rapeseed oil has been studied in a screening test at 130°C by an induction period method. Hindered monophenols, sulphides, phosphites, aromatic amines and zinc dithiophosphates yielded no or only marginal stabilising effects. Remarkably increased oxidation stabilities were observed with certain hindered bisphenols, polyhydroxybenzenes, zinc and bismuth dithiocarbamates. In high oleic sunflower oil with a lesser portion of multiple unsaturation, these additives induced relatively longer induction periods. Mixtures of zinc dithiocarbamates and 4,4′-methylenebis-(2, 6-di-tert-butylphenol) or octylated di-phenylamine, as well as compositions of all three compounds, exhibited synergistic effects. Under the conditions employed these additives were distinctly superior to commercially recommended formulations. A mechanistic concept of the antioxidant action of zinc dithiocarbamate is briefly discussed.

Mixed lubrication — an overview

Abstract: The regime known as ‘mixed’ lubrication lies between those of hydrodynamic and elastohydrodynamic. This paper reviews work on this subject, in order to recognise the key areas of progress, and of ignorance. Film thickness and surface roughness are discussed, to conclude that below certain values of λ, there are limitations to earlier models. Computational solution of the micro-EHD problem has largely succeeded, as well as more analytical approaches. The mixed lubrication regime has been studied by electrical contact resistance, friction measurement, and, more recently, analysis has been aided by optical interferometry — the implications of this work, and future prospects, are addressed.

Sixty years of EHL

Abstract: It is now 60 years since Ertel produced the first solution to the elastohydrodynamic lubrication (EHL) problem. There has been enormous progress since then, both in numerical modelling and in experimental research on EHL. The moving, rough surface EHL problem can now be solved on laptop-level computers, while maps of film thickness, pressure and temperature can be obtained experimentally from within rolling/sliding contacts. However, there remain some important questions that have not been fully resolved. One of the most contentious is how to describe the rheological properties of lubricants under the very severe conditions present in thin film EHL contacts. A second is how to model mixed lubricated contact, where the fluid film can break down at asperity conjunctions. But perhaps the greatest challenge to researchers in EHL is to produce useful design equations for predicting the performance of machine components operating in EHL and thereby ensure that EHL theory becomes an integral part of the design process. Copyright © 2006 John Wiley & Sons, Ltd.

Dimple patterns design for different circumstances

Abstract: The appealing and enigmatic properties of biological surfaces inspire people that a smooth surface is not always the best. Currently, the patterns of microdimples have attracted more attentions since such closed texture cells are supposed to generate hydrodynamic pressure easily. The advanced manufacturing techniques provide precision and freedom for the fabrication of microdimples, which enables the optimisation of dimple geometry and distribution to obtain better tribological performances. Over the past decade, experiments were carried out to investigate the effects of microdimples on various materials under different operating conditions. Analytical models were established to evaluate the hydrodynamic effect of the dimple patterns. The results suggest that the design of dimple pattern following hydrodynamic principle would obtain good tribological performance under high-speed low-load conditions; however, for the case of low-speed high-load conditions, shallow and small dimples would have more obvious friction reduction effect than those designed based on hydrodynamic pressure generation. Copyright © 2011 John Wiley & Sons, Ltd.