ON RANDOM EXPECTED VALUES VARIATIONS OF TRIBOLOGY PARAMETERS IN HUMAN HIP JOINT SURFACES

Tribologia ◽  
2021 ◽  
Vol 297 (3) ◽  
pp. 45-56
Author(s):  
Krzysztof Wierzcholski ◽  
Jacek Gospodarczyk
Keyword(s):  
Friction Coefficient ◽  
Synovial Fluid ◽  
Carrying Capacity ◽  
Dynamic Viscosity ◽  
Fluid Dynamic ◽  
Load Carrying Capacity ◽  
Friction Forces ◽  
Load Carrying ◽  
Gap Height ◽  
Human Joint

This paper presents recent progress in the knowledge concerning the stochastic theory of bio- hydrodynamic lubrication with a phospholipids bilayer. On the basis of experimental measurements and analytical solutions, the research concerns the determination of the random expectancy values of load carrying capacity, the friction coefficient, and synovial fluid dynamic variations. After numerous measurements, it directly follows that the random density function of the gap height in the human joint usually indicates a disorderly increases and decreases in the height. Such irregular gap height variations have an important influence on the random synovial bio-fluid dynamic viscosity. This finally leads to the friction coefficient and cartilage wear changes of cooperating bio- surfaces. The main topic of this paper relates to the expectancy values of the tribology parameters localized inside the variable stochastic standard deviation intervals of the human joint gap height. The results obtained finally indicate the influence of the random roughness and growth of living biological cartilage surfaces on the expectancy values of the synovial fluid dynamic viscosity, load carrying capacity and friction forces in human hip joints.

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.

Study on Tribological Performances for Textured Bearing of ICE

2013 ◽  
Vol 690-693 ◽  
pp. 1999-2002
Author(s):  
Fan Ming Meng ◽  
Tao Yang ◽  
Tao Long
Keyword(s):  
Friction Coefficient ◽  
Internal Combustion Engine ◽  
Carrying Capacity ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Load Carrying Capacity ◽  
Oil Film ◽  
Load Carrying ◽  
Inner Surface ◽  
Coupling Algorithm

The influence of dimples on the inner surface of big end bearing in internal combustion engine (ICE) on tribological performances of the bearing was investigated based on Navier-Strokes equation and other associated equations. In doing so, the CFD modulus in the software ANSYS12 version is used to analyze the dimple effect on the tribological performances of the bearing using two-way fluid-solid coupling algorithm. Some mechanisms are revealed about the dimple effect on the load-carrying capacity and friction coefficient of oil film, and the deformation and stress for the textured big end bearing.

Static characteristics of misaligned multiple axial groove water-lubricated bearing in the turbulent regime

2016 ◽  
Vol 231 (3) ◽  
pp. 385-398 ◽  
Author(s):  
Ravindra Mallya ◽  
Satish B Shenoy ◽  
Raghuvir Pai
Keyword(s):  
Reynolds Number ◽  
Friction Coefficient ◽  
Carrying Capacity ◽  
Journal Bearing ◽  
Load Capacity ◽  
Turbulent Regime ◽  
Load Carrying Capacity ◽  
Static Characteristics ◽  
Load Carrying ◽  
Turbulence Effects

The static characteristics of misaligned three-axial water-lubricated journal bearing in the turbulent regime are analyzed for groove angles 36° and 18°. Ng and Pan’s turbulence model is applied to study the turbulence effects in the journal bearing. The static parameters such as load-carrying capacity, friction coefficient, and side leakage are found for different degree of misalignment (DM). The change in flow regime of the lubricant from laminar to turbulent and the increase in misalignment, improved the load capacity of the bearing. For lightly loaded bearings, the friction coefficient of the bearing increased with the increase in Reynolds number.

Partially Textured Slider and Journal Bearing Analysis

2012 ◽  
Vol 58 (2) ◽  
Author(s):  
T. V. V. L. N. Rao ◽  
A. M. A. Rani ◽  
T. Nagarajan ◽  
F. M. Hashim
Keyword(s):  
Friction Coefficient ◽  
Coefficient Of Friction ◽  
Carrying Capacity ◽  
Journal Bearing ◽  
Load Capacity ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Bearing Analysis

The present study examines the influence of partial texturing of bearing surfaces on improvement in load capacity and reduction in friction coefficient for slider and journal bearing. The geometry of partially textured slider and journal bearing considered in this work composed of a number of successive regions of groove and land configurations. The nondimensional pressure expressions for the partially textured slider and journal bearing are derived taking into consideration of texture geometry and extent of partial texture. Partial texturing has a potential to generate load carrying capacity and reduce coefficient of friction, even for nominally parallel bearing surfaces.

Overall Characteristics of Bearings Lubricated With Ferrofluids

1983 ◽  
Vol 105 (3) ◽  
pp. 466-475 ◽  
Author(s):  
N. Tipei
Keyword(s):  
Boundary Conditions ◽  
Carrying Capacity ◽  
Magnetic Particle ◽  
Journal Bearings ◽  
Load Carrying Capacity ◽  
Pressure Center ◽  
Friction Forces ◽  
Flow Rates ◽  
Load Carrying ◽  
Side Flow

Using the results shown in some previous papers, the overall characteristics of bearings lubricated with ferrofluids are calculated. First, the load carrying capacity of infinitely long sliding and journal bearings is considered. The pressure center and the attitude angle are also determined. Then, similar characteristics of finite bearings are obtained. In both cases, the new boundary conditions and the actual film extent under magnetic stresses are taken into account. It is shown that friction forces are mainly affected by the change in viscosity due to magnetic particle suspensions, while magnetic stresses modify friction only under special conditions which usually are not met in lubrication. In addition, the flow rates and the side flow coefficients are calculated. It is shown that the lubricant leakage can be reduced and even avoided when proper measures are taken. For short bearings, diagrams are given for the film extent, the film boundaries, the load carrying capacity, and the attitude of the journal center.

JOINT CARTILAGE LUBRICATION WITH PHOSPHOLIPID BILAYER

Tribologia ◽  
2016 ◽  
Vol 266 (2) ◽  
pp. 145-157 ◽  
Author(s):  
Krzysztof WIERZCHOLSKI
Keyword(s):  
Synovial Fluid ◽  
Electrostatic Field ◽  
Dynamic Viscosity ◽  
Fluid Dynamic ◽  
Collagen Fibre ◽  
Phospholipid Bilayer ◽  
Power Exponent ◽  
Hydrodynamic Description ◽  
Fibre Concentration ◽  
Human Joint

The surface of an articular cartilage human joint, coated with phospholipid bilayers or multi-layers, plays an important role in the surface-active phospholipid lubrication, friction, and wear during human limb movement. The biological bi-layer is a thin polar membrane composed of two layers of phospholipids that have a hydrophilic phosphate head (from the outside) and a hydrophobic tail (from the inside) consisting of two fatty acid chains. These membranes are flat sheets that form a continuous barrier around all cells. Synovial fluid (SF) in the human joint gap contains glycoprotein, lubricin (proteinglycan 4), and hyaluronidase, i.e. an enzyme that produces hialuron acid and ±10% phospholipids. Because the mechanism of surface articular phospholipid lubrication (SAPL) has been a frequently controversial subject in the past decade, this fact requires showing the hydrodynamic description in the form of a mathematical model of the abovementioned problem and its particular solution. To give a description of this model, it is necessary to recognize the variations of the dynamic viscosity of synovial fluid as a function of parameters depending on the presence of many phospholipid particles. To these parameters belong power (exponent) concentration of hydrogen ions (pH), cartilage wet ability (We), collagen fibre concentration in synovial fluid, and a created electrostatic field on the phospholipid membrane. Based on the Young-Laplace-Kelvin Law, initial achievements presented in scientific papers and our own investigations illustrated in this paper, the decrements, and increments of synovial fluid dynamic viscosities versus pH and wet ability (We) increases, simultaneously taking into account the influence of the intensity of charges in the electrostatic field. Moreover, this study considers the influence of collagen fibre concentration on the dynamic viscosity of synovial fluid. Based on initial considerations performed by virtue of the developed SAPL, it may be stated that the charge increments from low to high values of the electrostatic field is connected with viscosity increases of synovial fluid but only simultaneously with the pH index and cartilage wet ability variations.

Effect of Cavitation on Tribological Performances for Textured Surfaces

2012 ◽  
Vol 472-475 ◽  
pp. 391-394 ◽  
Author(s):  
Fan Ming Meng ◽  
Ling Zhang
Keyword(s):  
Fourier Transform ◽  
Friction Coefficient ◽  
Fast Fourier Transform ◽  
Carrying Capacity ◽  
Reynolds Equation ◽  
Load Carrying Capacity ◽  
Textured Surfaces ◽  
Force Load ◽  
Cavitation Effect ◽  
Load Carrying

The influence of cavitation in a lubricant between textured surfaces on tribological performances of the surfaces was investigated based on an extended Reynolds equation and other associated equations. The tribological performances of the surfaces holding dimples with divergent-convergent shape were analyzed with the cavitation effect consideration at different dimple numbers. In doing so, the elastic deformation of the surface is evaluated using continuous convolution fast Fourier transform (CC-FFT). Some mechanisms are revealed about the cavitation effect on the friction coefficient, friction force, load-carrying capacity and cavitated area of the textured surfaces.

scholarly journals Estimation of Random Friction Forces on the Microbearing Cooperating Surfaces

2019 ◽  
Vol 26 (2) ◽  
pp. 167-174
Author(s):  
Krzysztof Wierzcholski ◽  
Andrzej Miszczak
Keyword(s):  
Dynamic Viscosity ◽  
Apparent Viscosity ◽  
Hydrodynamic Lubrication ◽  
Stochastic Theory ◽  
Superficial Layer ◽  
Mathematical Form ◽  
Friction Forces ◽  
Random Roughness ◽  
Load Carrying ◽  
Gap Height

Abstract Presented paper concerns a new mathematical form of stochastic theory of hydrodynamic friction forces occurring on the real cooperating surfaces in computer micro bearing fan and computer microbearing in hard disc driver HDD. This paper presents particularly a new-review of stochastic analytical considerations realized by the authors for friction forces estimation during hydrodynamic lubrication performed on the ground of the measurements of the gap height between two roughness surfaces. After numerous experimental measurements directly follows that the random unsymmetrical increments and decrements of the gap height of computer microbearings have important influence on the load carrying capacities and finally on the friction forces and wear of cooperating surfaces. The main topic demonstrates the influence of the variations of expectancy values and standard deviation of the computer microbearing gap height on the friction forces occurring in the HDD and microbearing fan. Moreover, it is observed the evident connection between the apparent dynamic viscosity and the features of the microbearing superficial surface. Hence after abovementioned remarks follows the corollary that the influence of the microbearing gap height stochastic variations connected with the surface roughness tend moreover indirect from the apparent viscosity into the friction forces variations. The synthetic, complex elaboration of obtained results indicates finally the influence of the random roughness in micro and nano level of microbearing surfaces on the friction forces distribution. A new results contained in this paper are obtained taking into account 3D variations of dynamic viscosity of the non-Newtonian lubricant, particularly variations crosswise the film thickness and influences of surface superficial layer features on the lubricant apparent viscosity.

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