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This article presents a film thickness prediction, using a new analytical form of the one-dimensional Reynolds equation, for lubricants whose rheological behaviour follows a modified Carreau model proposed by Bair. The development of the new equation was presented in New Reynolds equation for line contact based on the Carreau model modification by Bair, Tribol Int 55 (2012) 141–147. Hereby the numerical calculation process is presented and the ensuing results of film thickness, mid-plane shear stress and shear rate are compared with those published by other researchers for line contact in elastohydrodynamic lubrication.

This article explores the influence of the appearance of micropitting in different types of additives added to a polyalphaolefinic low-viscosity base oil, namely a polyalphaolefin PAO6. Additives commonly used in mechanical transmissions by gears were used, i.e., extreme pressure, anti-wear and friction modifier. For the study, we have conducted a series of tests on a disc machine under various operating conditions. The temperature and surface roughness of the test specimens have been changed in order to study different lubricant specific film thicknesses, as the last is one of the most influential parameters on the appearance of micropitting. Tests have shown the important influence of the additives, and their concentration, in the development of micropitting and their associated effects, depending on the operating conditions of the contact. Along with the study of the effect of additives, the influence of specific film thickness on the friction coefficient, surface appearance, conditions of lubrication, and wear was also studied.

The combined use of smart materials, complementing each others\' characteristics and resulting in devices with optimised features, is providing new solutions in many industries. The use of ingenious combinations of smart materials has led to improvements in actuation speed and force, signal-to-noise ratio, sensor precision and unique capabilities such as self-sensing self-healing systems and energy autonomy. This may all give rise to a revival for numerous families of smart materials, for which application proposals had already reached a stationary situation. It may also provide the boost needed for the definitive industrial success of many others. This study focuses on reviewing the proposals, preliminary studies and success cases related to combining smart materials to obtain multifunctional, improved systems. It also examines the most outstanding applications and fields for the combined use of these smart materials. We will also discuss related study areas which warrant further research for the development of novel approaches for demanding applications.

This paper analyses the applicability of artificial neural networks for predicting the lubricated friction coefficient. We will consider their use as faster and simpler alternatives to simulations based on theoretical behaviour equations. The development of several different artificial neural networks is presented. They have been trained through tribological tests on a mini-traction-machine, which furnishes the friction coefficient in point contacts. Once the training has been completed the networks are applied as tools for predicting the results in different operating conditions. Their advantages and disadvantages are analysed compared with conventional simulation tools. Copyright © 2013 John Wiley & Sons, Ltd.

Surface texturing has proved to be a very useful tool for expanding the behaviour under hydrodynamic and elastohydrodynamic regimes instead of mixed or boundary lubrication regimes, and therefore for reducing the friction coefficient under high-load low-speed conditions. This article presents the texturing of different copper test-samples using photolithography and chemical etching to measure the friction coefficient using a point contact machine. The effects of texture size, texturing density, the initial roughness of the samples and the operating conditions have all been studied. Some combinations of texturing density and texture size achieve up to 30% reduction in the friction coefficient. Taking into account experimental data, artificial neural networks are used as a tool for both predicting and optimising the friction coefficient on the textured surface for any given operating condition.

This paper analyses the influence of lubricant behaviour on the appearance of pitting. It attempts to study the effect of viscosity–pressure relation, compressibility, film thickness–roughness relation and friction coefficient on pitting failure of the contacting elements. To explain these effects, we first deal with the influence of the oil on the lubrication of the contact using elastohydrodynamic theory and secondly two multiaxial fatigue criteria are used, Crossland criterion and Dang Van criterion, to evaluate the influence of the rheology on the appearance of pitting. Finally, different applications are presented together with a discussion on the results obtained.

This article presents analytical friction prediction models applicable to lubricants in point contacts under thermal elastohydrodynamic lubrication (TEHL). The types of models used consider the heat generated and its penetration into the bulk of the contacting solids. Therefore, the increase in temperature is determined, which causes important variations in the operating conditions. The article sets out the hypotheses assumed, the theoretical calculation procedures and the ensuing equations for determining the friction coefficient under TEHL. An experimental stage is performed on a mini-traction-machine, which allows the measurement of friction coefficient in ball–disc contacts under a wide range of control parameters involved in TEHL, such as lubricant bath temperature, load, average velocity, slide-to-roll ratio, and contacting materials. The experimental results for different lubricants are compared to those given by the models, and show the proposed models to be accurate for predicting the friction coefficient.

This paper presents a new form of the one-dimensional Reynolds equation for lubricants whose rheological behaviour follows a modified Carreau rheological model proposed by Bair. The results of the shear stress and flow rate obtained through a new Reynolds–Carreau equation are shown and compared with the results obtained by other researchers.

This work presents the Royal Factories promoted by the Spanish crown in the 18th and 19th centuries in the context of European industrialisation. They are classified together with the main types of factories and some specific examples are described. The article includes a discussion on the conditions that promoted their proliferation as the precursors of present-day state-owned industry, as well as the main causes that led to their decline.