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This review paper highlights the tribological behaviour and performance of smart fluids. Two main kinds of smart fluids, that respond to a suitable external stimulus are investigated - electrorheological and magnetorheological fluid. The excitation of an external active field significantly increases or decreases the fluidity, depending on the fluid type. First, the tribological behaviour of both types of smart fluids without the influence of an external field and under the external active field, respectively, are reviewed. Subsequently, the influence of external field activation on the lubricating layer is described. Finally, a summary of the most notable findings of investigated smart fluids performance and behaviour is provided. Possible future applications are then considered for smart lubricants technology and engineering devices. [ABSTRACT FROM AUTHOR]

This paper deals with the experimental study of an elastohydrodynamic contact under conditions of insufficient lubricant supply. Starvation level of this type of the contact may be experimentally determined based on the position of the meniscus, but this way can't determine all levels of starvation. Consequent development in the field of tribology achieved theoretical model that can determine all levels of starvation by dependency on the thickness of the lubricant film entering the contact, but it is difficult for experimental verification. The main goal of this work is an experimental study and description of the behavior of the elastohydrodynamic contact with controlled thickness of the lubricant film at the contact input. Contact was lubricated by the base oil and the grease and compared. Results were surprising because the only differences between oil and grease were observed for more viscous lubricants at thicker film layer entering to the contact. [ABSTRACT FROM AUTHOR]

A metal powder (copper, tin, lead, silver, bronze) as well as some graphite and molybdenum compounds are widely used as solid additives into oils under the high pressures and high loads. It was shown that the advantage of these additives is to reduce wear and friction as well the load between contact elements. Despite all these positives, there are inadequate rheological, anti-corrosion properties and sedimentation stability. Present studies were focused to find a new type of solid particles to create a lubricating composition with low friction. In this case, Ultra Dispersed Diamond-Graphite (UDDG) can represent the possible solution. These nanoparticles have very good physical and chemical properties, high hardness, resistance and compatibility with various types of oils and lubricants as well as environmental friendliness. This paper presents experimental investigations of the influence of UDDG on friction and wear for a highly loaded lubricated contacts using tribological ball-on-disc test rig and mini traction machine. However, experimental results show, that the UDDG have some negatively influence on the friction. It seems that chemical treatment of UDDG powder dispersed in lubricant play a great role for the case of wear and friction for heavy loaded contacts. [ABSTRACT FROM AUTHOR]