Squeeze Film Lubrication between Rough Poroelastic Rectangular Plates with Micropolar Fluid: A Special Reference to the Study of Synovial Joint Lubrication

N B Naduvinamani,G K Savitramma

doi:10.5402/2013/431508

Abstract

The effects of surface roughness and poroelasticity on the micropolar squeeze film behavior between rectangular plates in general and that of synovial joints in particular are presented in this paper. The modified Reynolds equation, which incorporates the randomized surface roughness structure as well as elastic nature of articular cartilage with micropolar fluid as lubricant, is derived. The load-carrying capacity and time of approach as functions of film thickness during normal articulation of joints are obtained by using Christensen stochastic theory for rough surfaces with the assumption that the roughness asperity heights are to be small compared to the film thickness. It is observed that the effect of surface roughness has considerable effects on lubrication mechanism of synovial joints.

Highlights

E study of mechanism of synovial joints has recently become an active area of scienti c research. e human joint is a dynamically loaded bearing which employs articular cartilage as the bearing and synovial uid as the lubricant. nce a uid lm is generated, squeeze lm action is capable of providing considerable protection to the cartilage surface. e loaded bearing synovial joints of the human body are the shoulder, hip, knee, and ankle joints; such joints have a lower friction coe cient and negligible wear
A more general biphasic lubrication theory was subsequently proposed by Mow and Lai [3]
For a similar con guration but under cyclic loading, friction was found to be similar or even at a higher level [9]. e importance of the biphasic lubrication has been studied by enzymatic treatment of articular cartilage altering the biphasic properties and uid pressurization such as chondroitinase [10,11,12,13]

Summary

Introduction

E study of mechanism of synovial joints has recently become an active area of scienti c research. e human joint is a dynamically loaded bearing which employs articular cartilage as the bearing and synovial uid as the lubricant. nce a uid lm is generated, squeeze lm action is capable of providing considerable protection to the cartilage surface. e loaded bearing synovial joints of the human body are the shoulder, hip, knee, and ankle joints; such joints have a lower friction coe cient and negligible wear. E importance of the unique biphasic load-carrying characteristics of articular cartilage and uid ow inside has been recognized in the lubrication of synovial joints such as weeping and boosted lubrication theories. A more general biphasic lubrication theory was subsequently proposed by Mow and Lai [3] It was not until in the 1990s that the relation between friction and interstitial uid pressurization was comprehensively studied [4,5,6,7]. A number of friction studies have been carried out under a wide range of tribological conditions to investigate the biphasic lubrication of articular cartilage. A theoretical study of combined effects of surface roughness and micropolar uid in squeeze lm lubrication between poroelastic rectangular plates is presented.

Solution of the Problem

Results and Discussion

Conclusion