Numerical Study of Film Thickness Averaging in Compressible Lubricating Films Incurring Stationary Surface Roughness

1990 ◽  
Vol 112 (2) ◽  
pp. 230-237 ◽  
Author(s):  
Y. Mitsuya ◽  
T. Hayashi
Keyword(s):  
Film Thickness ◽  
Numerical Study ◽  
Wave Number ◽  
Numerical Comparison ◽  
Load Carrying Capacity ◽  
Roughness Effects ◽  
Individual Unit ◽  
Wide Range ◽  
Load Carrying ◽  
Compressibility Effects

The compressibility effects of lubricating films incurring a roughness on film thickness averaging were studied numerically with a focus on the physical interpretation of the roughness effects. A numerical comparison between load-carrying capacities resulting from rough film thickness and from averaged film thickness are presented for a wide range of bearing numbers up to 107. It is found that currently indicated particular features such as the appearance of the maximum or minimum load-carrying capacity can be induced from the superimposition of local compressibility effects (LCEs) caused by individual unit roughness on compressibility effects owing to averaged film thickness. The most noticeable difference between the case of small LCEs and that of saturated LCEs is that the roughness phase results in a minimal effect with the increasing wave number for the former, while it creates a dominant effect for the latter. The results confirm that the same averaging method as that for incompressible films can be applied for small LCEs, and that Greengard’s method is applicable for nearly saturated LCEs. It should be noted that the averaged film thickness can be determined physically for small LCE regions, while it is defined mathematically for nearly saturated LCE regions.

The Validity of the Reynolds Equation in Modeling Hydrostatic Effects in Gas Lubricated Textured Parallel Surfaces

2005 ◽  
Vol 128 (2) ◽  
pp. 345-350 ◽  
Author(s):  
Y. Feldman ◽  
Y. Kligerman ◽  
I. Etsion ◽  
S. Haber
Keyword(s):  
Carrying Capacity ◽  
Reynolds Equation ◽  
Stokes Equations ◽  
Surface Texturing ◽  
Laser Surface Texturing ◽  
Physical Parameters ◽  
Load Carrying Capacity ◽  
Wide Range ◽  
Load Carrying ◽  
Parallel Surfaces

Microdimples generated by laser surface texturing (LST) can be used to enhance performance in hydrostatic gas-lubricated tribological components with parallel surfaces. The pressure distribution and load carrying capacity for a single three-dimensional dimple, representing the LST, were obtained via two different methods of analysis: a numerical solution of the exact full Navier-Stokes equations, and an approximate solution of the much simpler Reynolds equation. Comparison between the two solution methods illustrates that, despite potential large differences in local pressures, the differences in load carrying capacity, for realistic geometrical and physical parameters, are small. Even at large clearances of 5% of the dimple diameter and pressure ratios of 2.5 the error in the load carrying capacity is only about 15%. Thus, for a wide range of practical clearances and pressures, the simpler, approximate Reynolds equation can safely be applied to yield reasonable predictions for the load carrying capacity of dimpled surfaces.

The effect of V-shape protruded and dimple textured on the load-carrying capacity and coefficient of friction of hydrodynamic journal bearing: A comparative numerical study

2020 ◽  
pp. 135065012093500
Author(s):  
Sanjay Sharma ◽  
Aniket Sharma ◽  
Gourav Jamwal ◽  
Rajeev Kumar Awasthi
Keyword(s):  
Coefficient Of Friction ◽  
Carrying Capacity ◽  
Performance Enhancement ◽  
Numerical Study ◽  
Geometrical Parameters ◽  
Load Carrying Capacity ◽  
Enhancement Ratio ◽  
Load Carrying ◽  
The Coefficient Of Friction ◽  
Computing Performance

The present comparative numerical study is between V-shape protruded, dimple textured, and untextured bearing. The performance parameters in terms of the load-carrying capacity and coefficient of friction are computed by solving governing Reynold’s equation of the lubricant fluid flow. The governing equation is solved by the finite element method by assuming that the fluid is Newtonian and isoviscous in nature. The effect of eccentricity ratios, texture distribution, texture heights, and texture depths are considered for the analysis in both textured bearings. From simulated results, the load-carrying capacity and coefficient of friction is found to be maximum for protruded textured bearing in full textured region and first half-textured region respectively as compared to untextured bearings. Finally, optimal operating and geometrical parameters of textured bearing is obtained by computing performance enhancement ratio, which is the ratio of the load-carrying capacity to the coefficient of friction. The maximum value of the performance enhancement ratio is found for protruded and dimple textured bearing in full texturing and second half-region corresponding to the eccentricity ratio of 0.8 and 0.6 respectively at texture height and depth of 0.4.

The Performance of Hydrodynamic Lubricating Films With Viscosity Variations Perpendicular to the Direction of Motion

1972 ◽  
Vol 94 (1) ◽  
pp. 44-48 ◽  
Author(s):  
E. B. Qvale ◽  
F. R. Wiltshire
Keyword(s):  
Film Thickness ◽  
Carrying Capacity ◽  
Load Carrying Capacity ◽  
End Effects ◽  
Parametric Curves ◽  
One Dimensional ◽  
Lubricating Film ◽  
Families Of Curves ◽  
Load Carrying ◽  
The Coefficient Of Friction

The effects of prescribed viscosity variations across a hydrodynamic lubricating film are studied. The film is strictly one dimensional and end effects are neglected. The viscosity variations are given by three families of curves. The considerable decreases (in the limit 100 percent) and occasional increases in the coefficient of friction that can occur for constant film thickness and load-carrying capacity are evaluated and the results are presented in terms of parametric curves. Important physical situations where these viscosity variations may be observed or produced are described.

Stokes Roughness Effects on Hydrodynamic Lubrication. Part II—Effects Under Slip Flow Boundary Conditions

1986 ◽  
Vol 108 (2) ◽  
pp. 159-166 ◽  
Author(s):  
Y. Mitsuya
Keyword(s):  
Flow Regime ◽  
Carrying Capacity ◽  
Stokes Equations ◽  
Hydrodynamic Lubrication ◽  
Slip Flow ◽  
Load Carrying Capacity ◽  
Roughness Effects ◽  
Random Roughness ◽  
Load Carrying ◽  
Flow Effects

Stokes roughness effects on hydrodynamic lubrication are studied in the slip flow regime. Slip flow boundary conditions for Navier-Stokes equations are derived, assuming that the fluid on a surface slips due to the molecular mean free path along the surface, even if the surface is rough. The perturbation method for Navier-Stokes equations, which was derived in Part I of this report, is then applied. Slip flow effects on load carrying capacity and frictional force are numerically clarified for both Stokes and Reynolds roughnesses. In the slip flow regime, second-order quantities induced by Stokes effects, such as flow rate, load carrying capacity, and frictional force are in proportion to the wavenumber squared. This phenomenon relative to the quantities being proportional is also the same as that in the continuum flow regime. As a result of velocity slippage, the load carrying capacity in Stokes roughness is found to decrease more than in Reynolds roughness for incompressible films, while the relationship is reversed for compressible films having a high compressibility number. The simulation of random roughness, which is generated by numerical means, clarifies one important result: the average slip flow effects associated with random Stokes roughness become similar to the slip flow effects in deterministic sinusoidal Stokes roughness, whose wavelength and height are statistically equivalent to those of random roughness. Although attention should be given to the fact that Stokes effects on random roughness demonstrate considerable scattering with the continuum flow, such scattering diminishes with the slip flow.

A Theory of Liquid-Solid Lubrication in Elastohydrodynamic Regime

1989 ◽  
Vol 111 (3) ◽  
pp. 440-444 ◽  
Author(s):  
M. M. Khonsari ◽  
S. H. Wang ◽  
Y. L. Qi
Keyword(s):  
Particle Size ◽  
Film Thickness ◽  
Carrying Capacity ◽  
Theoretical Study ◽  
Solid Particles ◽  
Solid Lubrication ◽  
Load Carrying Capacity ◽  
Line Contact ◽  
Load Carrying ◽  
Bounding Surfaces

A theoretical study of the effectiveness of solid particles dispersed in oil in the elastohydrodynamic line contact is presented. The analysis includes the variation of the viscosity and density of the lubricant as a function of pressure. The deformation of solid particles and that of the bounding surfaces are taken into consideration. Results are presented for the variation of the film thickness and the load carrying capacity as a function of the particle size, concentration, and properties of various types of particles.

Applicability of Net-Section Collapse Load Approach to Maximum Load Predictions of Multiple Circumferential Cracked Pipes: Numerical Study

2015 ◽  
Author(s):  
Myeong-Woo Lee ◽  
Seung-Jae Kim ◽  
So-Dam Lee ◽  
Jun-Young Jeon ◽  
Yun-Jae Kim
Keyword(s):  
Experimental Data ◽  
Numerical Method ◽  
Test Data ◽  
Numerical Study ◽  
Maximum Load ◽  
Load Carrying Capacity ◽  
Collapse Load ◽  
Crack Geometry ◽  
Large Sets ◽  
Load Carrying

To estimate maximum load-carrying capacity of pipes with multiple circumferential cracks, the net-section collapse load approach has been proposed. Although the proposed method has been validated against pipe test data, experimental data are quite limited due to large sets of variables to be considered. In this paper, a numerical method is proposed to generate virtual pipe test data with wide ranges of crack geometry and interspacing. To get confidence of the proposed numerical method, it is firstly applied to simulate existing 4-inch diameter schedule 80 pipes with two circumferential cracks. Predicted maximum loads agree well with experimental data. Then the proposed method is applied to generate maximum loads for wider ranges of crack geometry and loading conditions. It is found that the net-section collapse load approach works well for all cases considered.

Summary 1: The Influence of Engine Component Inertia Forces on Minimum Oil Film Thickness in Connecting Rod Big-End Bearings

1966 ◽  
Vol 181 (2) ◽  
pp. 155-155
Author(s):  
J. F. Booker ◽  
F. A. Martin
Keyword(s):  
Film Thickness ◽  
Graphical Form ◽  
Load Carrying Capacity ◽  
Eccentricity Ratio ◽  
Connecting Rod ◽  
Oil Film ◽  
First Approximation ◽  
Load Carrying ◽  
The Many ◽  
Inertia Forces

when Designing steadily loaded bearings the designer can usually predict the position of the journal centre quite easily with the aid of one of the many load carrying capacity/eccentricity relationships available. With dynamically loaded bearings, however, the journal path will vary in magnitude and direction throughout the loading cycle and one of the designer's interests is in the trends of maximum eccentricity ratio and the corresponding oil film thickness for various bearing and engine conditions. From experience with journal path predictions for big-end bearings it has been found that the eccentricity ratio in the bearing due to the peak firing load seldom exceeds that obtained by the inertia load loop (although this load is smaller) and therefore, as a first approximation, it is thought justifiable to neglect the gas forces. The results of this inertia study (numerical solution) applied to big-end bearings are presented in a general graphical form. Further work can be carried out on the same basis for main bearings, but this is more difficult to present in a general fashion as there are many more variables to consider, such as the phasing and magnitude of the crank out of balance and the firing order. This report therefore concentrates on the first step, i.e. that of big-end bearings.

scholarly journals Experimental and Numerical Study of Seismic Performance of Precast Prestressed Concrete Frame Internal Connection

2015 ◽  
pp. 406-413
Author(s):  
Xiandong Liao ◽  
Xiang Hu
Keyword(s):  
Seismic Performance ◽  
Prestressed Concrete ◽  
Carrying Capacity ◽  
Numerical Study ◽  
Scale Model ◽  
Load Carrying Capacity ◽  
Concrete Frame ◽  
Internal Connection ◽  
Load Carrying ◽  
Precast Prestressed Concrete

The seismic performance of the internal connection of precast prestressed concrete frame was studied systematically, based on the experiment of full-scale model under low cyclic reversed loading. This study was mainly focused on failure pattern, load-carrying capacity, skeleton curves, and hysteresis curves. Furthermore, a nonlinear finite element analysis using Abaqus was carried out to study the characteristics of the internal connection of precast prestressed concrete frame. Results revealed that the damage was concentrated mainly on beam end owing to flexural action, while steel bars in the columns and stirrups in the core region remained elastic until failure occurred. The calculated value of the load-carrying capacity of the internal connection was similar to the experimental one. Present study can be referenced for the application of precast prestressed concrete frame in high seismic zones.

Geometry Optimization of Textured Three-Dimensional Micro- Thrust Bearings

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
C. I. Papadopoulos ◽  
E. E. Efstathiou ◽  
P. G. Nikolakopoulos ◽  
L. Kaiktsis
Keyword(s):  
Carrying Capacity ◽  
Stokes Equations ◽  
Load Capacity ◽  
Three Dimensional ◽  
Load Carrying Capacity ◽  
Thrust Bearings ◽  
Micro Channels ◽  
Wide Range ◽  
Load Carrying ◽  
Bearing Load

This paper presents an optimization study of the geometry of three-dimensional micro-thrust bearings in a wide range of convergence ratios. The optimization goal is the maximization of the bearing load carrying capacity. The bearings are modeled as micro-channels, consisting of a smooth moving wall (rotor), and a stationary wall (stator) with partial periodic rectangular texturing. The flow field is calculated from the numerical solution of the Navier-Stokes equations for incompressible isothermal flow; processing of the results yields the bearing load capacity and friction coefficient. The geometry of the textured channel is defined parametrically for several width-to-length ratios. Optimal texturing geometries are obtained by utilizing an optimization tool based on genetic algorithms, which is coupled to the CFD code. Here, the design variables define the bearing geometry and convergence ratio. To minimize the computational cost, a multi-objective approach is proposed, consisting in the simultaneous maximization of the load carrying capacity and minimization of the bearing convergence ratio. The optimal solutions, identified based on the concept of Pareto dominance, are equivalent to those of single-objective optimization problems for different convergence ratio values. The present results demonstrate that the characteristics of the optimal texturing patterns depend strongly on both the convergence ratio and the width-to-length ratio. Further, the optimal load carrying capacity increases at increasing convergence ratio, up to an optimal value, identified by the optimization procedure. Finally, proper surface texturing provides substantial load carrying capacity even for parallel or slightly diverging bearings. Based on the present results, we propose simple formulas for the design of textured micro-thrust bearings.

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