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Lubrication is often employed in fretting contacts to reduce wear and stresses associated with high friction. Owing to the very small displacements associated with fretting, penetration of lubricating oils into the contact may not be effective. The efficacy of the penetration of the lubricant into the contact is very difficult to observe experimentally, and accordingly, this paper presents a numerical simulation of a lubricated fretting contact using a Coupled–Eulerian–Lagrangian (CEL) finite element method. Meso-scale CEL finite element models are developed to simulate the cylinder-on-flat arrangement used experimentally at the University of Nottingham in which the roughness of contact surfaces is characterized as fractal geometry by the Weierstrass-Mandelbrot (W-M) function. The fluid–solid and solid–solid contact in the lubricated fretting contact are simulated, and from these, wear and friction coefficients are determined. The effects of contact geometry on lubricated fretting contacts and lubricant on fretting wear are modelled and compared with experimental observations. Results indicate that oil lubrication reduces fretting wear and friction effectively in the less-conforming contacts but has little effect in the more-conforming contacts. • A novel approach of modeling lubricated contacts using a CEL finite element method. • The efficacy of the penetration of lubricant into the fretting contacts is simulated. • The wear and friction coefficients in a lubricated fretting contact are determined. • The effects of contact geometry on lubricated fretting contacts are simulated. [ABSTRACT FROM AUTHOR]

Two dimensional (2d) lubricant materials further explore their application in oil and gas field with the research direction of reducing friction and wear. In this study, we added multilayer graphene into water-based sand cleaning liquid to reduce friction and wear of the CT80 coiled tubing. The results showed that the addition of multilayer graphene significantly improved the anti-friction and wear resistance. Adding 0.5% multilayer graphene effectively reduced COF and wear by 75%. Additionally, the higher multilayer graphene concentration, the greater CT80 material withstood the load of severe wear. Multilayer graphene can be adsorbed on the wear debris or form a lubrication film on both worn surfaces, which facilitated the transportation of the debris. Moreover, the wear analysis indicated the main wear form of the CT80 material was abrasive wear and fatigue wear. • Multilayer graphene reduces friction and wear of CT80 coiled tubing in water-based sand cleaning liquid. • The higher multilayer graphene concentration, the greater CT80 material withstand the load. • Abrasive and fatigue wear are the main form of the CT80 material. • Multilayer graphene can be adsorbed on the debris and contact surfaces to form lubrication films. [ABSTRACT FROM AUTHOR]