Compliant-poroelastic lubrication in cartilage-on-cartilage line contacts

Abstract

The mechanisms of friction in natural joints are still relatively unknown and attempts at modelling cartilage-cartilage interfaces are rare despite the huge promise they offer in understanding bio-friction. This article derives a model combining finite strain, porous and thin film flow theories to describe the lubrication of cartilageon-cartilage line contacts. The material is modelled as compliant and poroelastic in which the micro-scale fibrous structure is interstitially filled with synovial fluid. This fluid flows over the interface between the bodies and is coupled to pressure generated by relative motion in the thin-film region formed under load. A Stribeck analysis demonstrated that this type of contact is determinable to conventional elastic lubrication but that the friction performance is improved by this interfacial flow. Moreover, the inclusion of periodic flow conditions when contact is onset is a specific novelty which elucidates new observations in the lubrication mechanisms pertaining to natural joints.

Finite element investigations of the fluid-solid behaviour in a bio-inspired poroelastic bearing

“…This indicated the presence of strong three-dimensional features that have not been observed or captured before in previous models. 16,30 Fluid-load support is the portion of the total load applied to a material that is supported by the fluid phase and it is critical in determining the tribological properties of cartilage. 10 This has been primarily of interest for sliding interfaces where fluid pressures offset the loads that would be carried by the solid matrix thereby minimising the friction from solid-on-solid interactions.…”

“…This indicated the presence of strong three-dimensional features that have not been observed or captured before in previous models. 16,30…”

“…28 These have been expanded to incorporate hyperelastic material models for application to large deformation finite element modelling 29 and have been further expanded by coupling thin-film theory to describe the lubricating boundary. 16,30 This finite element study investigates the biphasic behaviour of a poroelastic bearing inspired by the function of articular cartilage. It focuses on the mechanical origins of poroelasticity, which are derived a Darcy-type diffusion mechanism.…”

“…28 These have been expanded to incorporate hyperelastic material models for application to large deformation finite element modelling 29 and have been further expanded by coupling thin-film theory to describe the lubricating boundary. 16,30…”

Synovial Joints. Tribology, Regeneration, Regenerative Rehabilitation and Arthroplasty

“…It should be noted that in recent years it has become practically the norm to represent synovial fluid as a non-Newtonian fluid, since the results of solving most problems become more plausible even with significant simplifications of other elements and parameters of lubrication models [52,[59][60][61][62][63]. The only problem that arises in this case is a certain complication of the mathematical side of the problem.…”