Analysis of ‘Boosted Lubrication’ in Human Joints

1970 ◽  
Vol 12 (5) ◽  
pp. 364-369 ◽  
Author(s):  
D. Dowson ◽  
A. Unsworth ◽  
V. Wright
Keyword(s):  
Synovial Fluid ◽  
Operating Conditions ◽  
Fluid Film ◽  
Squeeze Film ◽  
Cartilage Surface ◽  
Human Joints ◽  
Experimental Findings ◽  
Joint Behaviour ◽  
Human Joint ◽  
Good Agreement

The load-bearing human joint is a self-acting dynamically loaded bearing which employs a porous and elastic bearing material (articular cartilage) and a highly non-Newtonian lubricant (synovial fluid). The authors' understanding is that the human joint experiences fluid-film (including elastohydrodynamic), mixed and boundary lubrication in its various operating conditions. It has been recognized that squeeze-film action is capable of providing considerable protection to the cartilage surface once a fluid film is generated (6) (8)§. Furthermore, the possibility of an increasing concentration of hyaluronic acid in synovial fluid during the squeeze-film action due to the porous nature of the cartilage and its surface topography and the known relationship between this concentration and the effective viscosity (7) has led to the concept of ‘boosted lubrication’ as an important feature of joint behaviour (10). A mathematical analysis of the concept of boosted lubrication of human joints is presented in this paper. The predictions of the analysis are shown to be in good agreement with experimental findings (12).

Human Joint Performance and the Roughness of Articular Cartilage

1980 ◽  
Vol 102 (1) ◽  
pp. 50-56 ◽  
Author(s):  
T. R. Thomas ◽  
R. S. Sayles ◽  
I. Haslock
Keyword(s):  
Articular Cartilage ◽  
Heel Strike ◽  
Height Distribution ◽  
Normal Walking ◽  
Cartilage Surface ◽  
Real Area Of Contact ◽  
The Mean ◽  
Human Joints ◽  
Human Joint ◽  
Real Area

It is known that the surface of articular cartilage is rough and it has been suggested that this is likely to affect the lubrication of human joints. This paper describes the direct measurement of a cartilage surface with a stylus instrument. It is found that the height distribution is Gaussian with an inverse-square power spectrum. It is thus possible to calculate the elastic deflection of the surface under normal walking loads and it is shown that the mean separation of the cartilage surfaces in a human joint varies rather slowly with load. In one particular hip joint at heel strike the real area of contact was calculated to be about 1.3 cm2, the mean gap to be about 60 μm and the trapped volume to be about 80 percent of that when standing.

Asperity Lubrication in Human Joints

1993 ◽  
Vol 207 (4) ◽  
pp. 245-254 ◽  
Author(s):  
J Q Yao ◽  
A Unsworth
Keyword(s):  
Synovial Fluid ◽  
Static Loading ◽  
Fluid Film ◽  
Loading Conditions ◽  
Lubrication Mechanism ◽  
Physiological Loading ◽  
Human Joints ◽  
Dynamic Loading Conditions ◽  
Film Lubrication ◽  
Fluid Film Lubrication

The asperity lubrication in human joints is examined in the present paper, with particular reference to the tertiary undulation with wavelengths of around 20–45 μm. It was found that, under dynamic physiological loading conditions, the secondary waviness of the cartilaginous surface (typically 0.5 mm wavelength) could be effectively flattened to sustain a fluid film of 0.1–0.3 μm thick, while the tertiary waviness could be squashed to sustain a much thinner fluid film of 0.01 μm (10 nm) thick with normal synovial fluid as the lubricant. The calculated film thickness for the tertiary undulation was less than 5 nm when the ankle joint was lubricated by Ringer's solution or pathological synovial fluids, or when only quasi-static loading conditions were considered, while a sufficiently thick fluid film could still be formed when the secondary undulations were considered alone. It was thus suggested that the fluid film lubrication mechanism was operative for human joints with normal synovial fluid as the lubricant under physiological dynamic loading conditions and the mixed lubrication mechanism could take over when static loading conditions prevailed or when watery lubricants (n ≈ 0.001 Pas) were used.

Calculated Rotordynamic Behaviour of a Twin Spool Engine and the Comparison With Test Results

1995 ◽  
Author(s):  
B. Domes ◽  
H. Hartmüller ◽  
G. Tokar ◽  
G. Wang
Keyword(s):  
Dynamic Behaviour ◽  
Complex Structure ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Test Results ◽  
Engine Model ◽  
Damping Characteristics ◽  
Resonance Frequencies ◽  
Squeeze Film Dampers ◽  
Good Agreement

Abstract The new BR 700 series of twin spool engines, of the thrust class of 15,000 to 20,000 pounds, is being developed for business jets. In this paper the rotordynamic vibration analysis is performed with a detailed whole engine model including both rotors, bearings with oil squeeze film dampers and squirrel cages, the engine structure, the mounts and the fuselage. The analytical method is described and some calculated results are presented. The effectiveness of the oil squeeze film dampers on all main bearings will be demonstrated. The comparison of the analytical and the measured results gives a good agreement in the resonance frequencies and in the damping characteristics. It also shows that a linear analysis can describe with sufficient accuracy the dynamic behaviour of such a complex structure like a twin spool engine under normal operating conditions.

Squeeze-Film Lubrication of the Human Ankle Joint Subjected to the Cyclic Loading Encountered in Walking

2005 ◽  
Vol 127 (1) ◽  
pp. 141-148 ◽  
Author(s):  
Miroslav Hlava´cˇek
Keyword(s):  
Articular Cartilage ◽  
Synovial Fluid ◽  
Ankle Joint ◽  
Interstitial Fluid ◽  
Fluid Film ◽  
Squeeze Film ◽  
Normal Cartilage ◽  
Gel Film ◽  
Human Ankle ◽  
Film Lubrication

Squeeze-film lubrication of the human ankle joint during walking is numerically analyzed, the effect of surface sliding being neglected at this stage. Biphasic mixture models are considered for synovial fluid (an ideal and viscous fluid phases) and for articular cartilage (an ideal interstitial fluid and an elastic porous matrix). In the model, the ideal fluid phase passes through the articular surface and matrix pores. The cartilage matrix is considered both normal and pathological (with primary osteoarthrosis). Calculations show that water and small solutes of synovial fluid imbibe into the articular cartilage during the stance period, while the interstitial fluid of the cartilage exudes and enriches the lubricant during the swing period in a central part of the contact at each step. Soon after the onset of walking, repeatedly near the load culmination of each step, the synovial fluid should be turned into a synovial gel and, shortly after, changed back again into a fluid there. In the pathological case, the protective synovial gel layer is quickly depleted after several steps and the surfaces may come briefly into contact in each cycle. With normal cartilage, however, the protective intermittent gel film (formed briefly at each step) maintains its thickness for a longer time. Normal cartilage also behaves more favorably, when a long walk is broken and then resumed shortly afterwards. With normal articular cartilage, maintenance of a lubricating fluid film is much aided by the cyclic nature of the loading encountered in walking, compared with the steady loading in standing where the fluid film is quickly filtered out into a protective permanent gel film.

Cavitation and Air Entrainment Effects on the Response of Squeeze Film Supported Rotors

1990 ◽  
Vol 112 (2) ◽  
pp. 347-353 ◽  
Author(s):  
F. Zeidan ◽  
J. Vance
Keyword(s):  
Nonlinear Response ◽  
Wide Spectrum ◽  
Air Entrainment ◽  
Operating Conditions ◽  
Fluid Film ◽  
Squeeze Film ◽  
Experimental Measurements ◽  
Inertial Effects ◽  
Squeeze Film Dampers ◽  
Rigid Rotors

This paper analyzes the effects of air entrainment and cavitation on the synchronous response of squeeze film supported rigid rotors. The fluid film force coefficients are obtained from experimental measurements corresponding to a wide spectrum of operating conditions. These conditions include regimes in which air entrainment effects are dominant. Other conditions where vapor cavitation and fluid inertial effects are dominant are included for comparison. The effects of air entrainment are shown to produce a nonlinear response representative of a softening spring effect not previously known to exist in squeeze film dampers.

Features of the Synovial Fluid Film in Human Joint Lubrication

Nature ◽  
1970 ◽  
Vol 225 (5236) ◽  
pp. 956-957 ◽  
Author(s):  
P. S. WALKER ◽  
J. SIKORSKI ◽  
D. DOWSON ◽  
M. D. LONGFIELD ◽  
V. WRIGHT
Keyword(s):  
Synovial Fluid ◽  
Fluid Film ◽  
Joint Lubrication ◽  
Human Joint

On the Computation of Inertial Coefficients in Squeeze-Film Bearings

1987 ◽  
Vol 201 (2) ◽  
pp. 125-131
Author(s):  
M D Ramli ◽  
J Ellis ◽  
J B Roberts
Keyword(s):  
Differential Equation ◽  
Diameter Ratio ◽  
Fluid Film ◽  
Squeeze Film ◽  
Eccentricity Ratio ◽  
Film Pressure ◽  
Static Eccentricity ◽  
Computational Simplicity ◽  
Analytical Expressions ◽  
Good Agreement

Inertial coefficients for full squeeze-film bearings are evaluated theoretically using Smith's differential equation relating fluid-film pressure to journal acceleration (1). The variations of the non-dimensionalized inertial coefficients with static eccentricity ratio in the radial and transverse directions are compared with some corresponding values obtained from Reinhardt and Lund (2) and Szeri et al. (3). The results from these three methods show good agreement, especially for short bearings (that is bearings with low values of length–diameter ratio). However, Smith's approach has the advantage of computational simplicity and leads to fairly simple, asymptotic, analytical expressions for very short, and very long, bearings.

Mass Conserving Cavitation Effects in Squeeze-Film Journal Bearings Subjected to Fully Reversing Loads

2010 ◽  
Author(s):  
S. Boedo
Keyword(s):  
Large Range ◽  
Journal Bearings ◽  
Experimental Results ◽  
Fluid Film ◽  
Squeeze Film ◽  
Threshold Pressure ◽  
Film Pressure ◽  
Time Histories ◽  
Cavitation Threshold ◽  
Good Agreement

This paper presents a study of cavitation effects associated with the performance of fluid-film journal bearings subjected to fully-reversing sinusoidal loading. Employing an established mass-conserving cavitation algorithm, it is observed that periodic time histories of journal eccentricity and maximum film pressure are strongly influenced by the process of cavitation formation and collapse. Good agreement of predicted and experimental results is obtained over a large range of loads for cavitation threshold pressure values typically associated with vapor cavitation.

Effect of concentration dependence of viscosity on squeeze film lubrication

2020 ◽  
Vol 75 (6) ◽  
pp. 533-542
Author(s):  
Poosan Muthu ◽  
Vanacharla Pujitha
Keyword(s):  
Carrying Capacity ◽  
Iterative Procedure ◽  
Squeeze Film ◽  
Load Carrying Capacity ◽  
Convection Diffusion ◽  
Load Carrying ◽  
Newtonian Viscous Fluid ◽  
Nicolson Scheme ◽  
Human Joint ◽  
Film Lubrication

AbstractThe influence of concentration of solute particles on squeeze film lubrication between two poroelastic surfaces has been analyzed using a mathematical model. Newtonian viscous fluid is considered as a lubricant whose viscosity varies linearly with concentration of suspended solute particles. Convection-diffusion model is proposed to study the concentration of solute particles and is solved using finite difference method of Crank–Nicolson scheme. An iterative procedure is used to get the solution for concentration, pressure and velocity components in film region. It has been observed that load carrying capacity decreases as the concentration of solute particles in the fluid film decreases. Further, the concentration of suspended solute particles decreases as the permeability of the poroelastic plate increases and these results may be useful in understanding the mechanism of human joint.

scholarly journals The Role of Hyaluronic Acid in Cartilage Boundary Lubrication

Cells ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 1606 ◽  
Author(s):  
Weifeng Lin ◽  
Zhang Liu ◽  
Nir Kampf ◽  
Jacob Klein
Keyword(s):  
Hyaluronic Acid ◽  
Synovial Fluid ◽  
Surface Force ◽  
Force Balance ◽  
New Paradigm ◽  
Low Friction ◽  
Cartilage Surface ◽  
Boundary Lubricant ◽  
Lipid Layers

Hydration lubrication has emerged as a new paradigm for lubrication in aqueous and biological media, accounting especially for the extremely low friction (friction coefficients down to 0.001) of articular cartilage lubrication in joints. Among the ensemble of molecules acting in the joint, phosphatidylcholine (PC) lipids have been proposed as the key molecules forming, in a complex with other molecules including hyaluronic acid (HA), a robust layer on the outer surface of the cartilage. HA, ubiquitous in synovial joints, is not in itself a good boundary lubricant, but binds the PC lipids at the cartilage surface; these, in turn, massively reduce the friction via hydration lubrication at their exposed, highly hydrated phosphocholine headgroups. An important unresolved issue in this scenario is why the free HA molecules in the synovial fluid do not suppress the lubricity by adsorbing simultaneously to the opposing lipid layers, i.e., forming an adhesive, dissipative bridge between them, as they slide past each other during joint articulation. To address this question, we directly examined the friction between two hydrogenated soy PC (HSPC) lipid layers (in the form of liposomes) immersed in HA solution or two palmitoyl–oleoyl PC (POPC) lipid layers across HA–POPC solution using a surface force balance (SFB). The results show, clearly and surprisingly, that HA addition does not affect the outstanding lubrication provided by the PC lipid layers. A possible mechanism indicated by our data that may account for this is that multiple lipid layers form on each cartilage surface, so that the slip plane may move from the midplane between the opposing surfaces, which is bridged by the HA, to an HA-free interface within a multilayer, where hydration lubrication is freely active. Another possibility suggested by our model experiments is that lipids in synovial fluid may complex with HA, thereby inhibiting the HA molecules from adhering to the lipids on the cartilage surfaces.

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