Abstract
Real-time external alteration of the internal properties of lubricants is highly desirable in all mechanical systems. However, fabricating a suitable and effective smart lubricant is a long-lasting experimental process. In this study, the film thickness and frictional response of ionic liquid-lubricated non-conformal contacts to an electric field excitation under elastohydrodynamic conditions were examined. Film thickness was evaluated using a “ball-on-disc” optical tribometer with an electric circuit. Friction tests were carried on a mini traction machine (MTM) tribometer with a “ball-on-disc” rotation module and an electric circuit for contact area excitation. The results demonstrate that there is a difference in the behaviour of the ionic liquid during electric field excitation at the evaluated film thicknesses. The results of evaluated film thicknesses demonstrate that there is a difference in the behaviour of the ionic liquid during electric field excitation. Therefore, the ionic liquids could be a new basis for the smart lubrication of mechanical components. Moreover, the proposed experimental approach can be used to identify electrosensitive fluids.
Highlights
In recent decades, an effort has been made to minimize friction in mechanisms to facilitate higher durability of contact surfaces and less energy consumption
The main assumption for excitation of the fluid film was to achieve a complete separation of contacting bodies with a coherent lubricating film; all measurements were designed for the lubrication parameter λ ≈ 7
A stronger response to a lower electric field was observed in the minimum film thickness compared with the central film thickness of the [BMIM]PF6 ionic liquid owing to the higher intensity of the electric field in the smaller gap between the contacting bodies
Summary
An effort has been made to minimize friction in mechanisms to facilitate higher durability of contact surfaces and less energy consumption. The performance of a mechanism is strongly dependent on the composition, structure, and interaction of the lubricant with surrounding surfaces. Smart liquid lubricants are fluids whose rheological properties such as apparent viscosity change in the presence of a magnetic or electric field. ER fluids, especially natural ER fluids [2], such as ionic liquids, seem to be more suitable lubricants for the parts with non-conformal elements and mechanisms with thin-film lubrication regimes [2]. For natural ER fluids, a high external voltage was required to create sufficient electric intensity to induce changes [3]. Because the lubricating layer thickness is in the nanometre scale, a laboratory voltage supplying with the range of 20 V was satisfactory to induce noticeable changes in film thickness [4]
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