Thin-Film Lubrication Theory for Newtonian Fluids With Surfaces Possessing Striated Roughness or Grooving

1973 ◽  
Vol 95 (4) ◽  
pp. 484-489 ◽  
Author(s):  
H. G. Elrod
Keyword(s):  
Reynolds Equation ◽  
Multiple Scale ◽  
Support Pressure ◽  
Load Carrying Capacity ◽  
Transient Effects ◽  
Thin Film Lubrication ◽  
Load Carrying ◽  
Bearing Design ◽  
First Time ◽  
Film Lubrication

Earlier work by others concerning the effects of striated roughness and grooving upon the load-carrying capacity of lubricating films is summarized, substantiated, and generalized. A multiple-scale double-variable technique is used on such lubrication problems for the first time. The present analysis applies to one-face roughness having striation wavelengths sufficiently long for the applicability of Reynolds equation. Transient effects are included. The final differential equation for support pressure is simple in form. In addition to predicting the effects of striated “Reynolds roughness”, this equation can be directly used in grooved-bearing design.

The Present State of Lubrication and Its Relation to Rheology

1968 ◽  
Vol 90 (3) ◽  
pp. 526-530 ◽  
Author(s):  
J. K. Appeldoorn
Keyword(s):  
Thin Film ◽  
Reynolds Equation ◽  
Mathematical Treatment ◽  
Load Carrying Capacity ◽  
Thin Film Lubrication ◽  
Load Carrying ◽  
Viscoelastic Effects ◽  
Viscoelastic Liquids ◽  
Film Lubrication ◽  
Made In

In thick-film lubrication, Reynolds’ equation is generally satisfactory. However, the assumptions made in deriving this equation cannot be justified for non-Newtonian, viscoelastic liquids. It is concluded that no satisfactory mathematical treatment is yet available for calculating the load-carrying capacity of such liquids. In thin-film lubrication, elastohydrodynamic calculations indicate that the lubricant film may be quite thick even under heavily loaded conditions, but discrepancies exist between calculation and experiment. These can be explained by assuming non-Newtonian behavior, or unusual viscoelastic effects, but the assumptions are largely unfounded. There is virtually a complete absence of data on the behavior of liquids under impact loading. Such data are needed to resolve whether thin-film lubrication is primarily chemical or primarily physical.

Analysis and comparative study of ferrofluid lubricated circular porous squeeze film-bearings

2017 ◽  
Vol 231 (11) ◽  
pp. 1450-1463 ◽  
Author(s):  
Rajesh C Shah ◽  
Dilip B Patel
Keyword(s):  
Magnetic Field ◽  
Reynolds Equation ◽  
Variable Magnetic Field ◽  
Squeeze Film ◽  
Load Carrying Capacity ◽  
Anisotropic Permeability ◽  
Load Carrying ◽  
Design Systems ◽  
Bearing Design ◽  
Maximum Field

Based on ferrohydrodynamic theory by R. E. Rosensweig and continuity equation for film as well as upper and lower porous regions, a general modified Reynolds equation for ferrofluid (FF) lubricated circular discs porous squeeze film-bearings is derived by assuming the validity of the Darcy’s law in the porous regions. The effects of porosity, slip velocity, anisotropic permeability and rotation at both the discs are also included for the study. Here, the FF is controlled by oblique and radially variable magnetic field. The effect of porosity is included because of its advantageous property of self-lubrication, and oblique variable magnetic field is important because of its advantage of generating maximum field at the required active contact zone of the bearing design systems. Using Reynolds equation, different circular porous squeeze film-bearing design systems (e.g. exponential, secant and parallel (flat)) are studied and compared for load-carrying capacity. During the course of investigation, it is observed that uniform magnetic field does not affect on the performances of the bearing systems.

Theoretical Analysis of Externally Pressurized Air Journal Bearing

1970 ◽  
Vol 12 (2) ◽  
pp. 123-129 ◽  
Author(s):  
B. C. Majumdar
Keyword(s):  
Experimental Data ◽  
Carrying Capacity ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Design Parameters ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Dimensional Parameters ◽  
Bearing Design

A theoretical investigation is made to predict the performance of an externally pressurized air journal bearing having several pressure sources. The pressure distribution, which leads to the determination of load-carrying capacity and flow requirement, is obtained by solving Reynolds equation numerically. The load and flow, expressed in non-dimensional parameters, are presented for different bearing design parameters (dimensionless). The results predicted by this method are compared with others' experimental data.

scholarly journals MULTIGRID METHOD FOR THE SOLUTION OF COMBINED EFFECT OF VISCOSITY VARIATION AND SURFACE ROUGHNESS ON THE SQUEEZE FILM LUBRICATION OF JOURNAL BEARINGS

2017 ◽  
Vol 46 (1) ◽  
pp. 1-8
Author(s):  
Vishwanath B. Awati ◽  
Ashwini Kengangutti ◽  
Mahesh Kumar N.
Keyword(s):  
Surface Roughness ◽  
Carrying Capacity ◽  
Micropolar Fluid ◽  
Reynolds Equation ◽  
Multigrid Method ◽  
Squeeze Film ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Viscosity Variation ◽  
Film Lubrication

The paper presents, the multigrid method for the solution of combined effect of surface roughness and viscosity variation on the squeeze film lubrication of a short journal bearing operating with micropolar fluid. The modified Reynolds equation which incorporates the variation of viscosity in micropolar fluid is analysed using Multigrid method. The governing modified Reynolds equation is solved numerically for the fluid film pressure and bearing characteristics viz. load carrying capacity and squeeze time. The analysis of the results predicts that, the viscosity variation factor decreases the load carrying capacity and squeeze film time, resulting into a longer bearing life. The results are compared with the corresponding analytical solutions.

The Effects on Bearing Load-Carrying Capacity of Two-Sided Striated Roughness

1974 ◽  
Vol 96 (4) ◽  
pp. 554-558 ◽  
Author(s):  
S. K. Rhow ◽  
H. G. Elrod
Keyword(s):  
Carrying Capacity ◽  
Multiple Scale ◽  
Load Carrying Capacity ◽  
Transient Effects ◽  
Slider Bearing ◽  
Scale Method ◽  
Load Carrying ◽  
Bearing Load ◽  
Order Of Magnitude ◽  
Final Equation

The multiple-scale method which was earlier employed for lubricating films with striated roughness on one of two opposing surfaces is here extended to include striated roughness on both surfaces. In some papers, the transient effects due to the roughness have been neglected. However, the present analysis shows that the term representing these effects is of the same order of magnitude as others retained in the final equation governing the average pressure. As an example, it is shown that with the same overall roughness characteristics, the load-carrying capacity of an infinitely wide slider bearing varies according to how the same roughness is distributed on opposing surfaces.

Thermohydrodynamic Phenomena in Fluid Film Lubrication

1973 ◽  
Vol 95 (2) ◽  
pp. 187-194 ◽  
Author(s):  
A. Seireg ◽  
H. Ezzat
Keyword(s):  
Reynolds Equation ◽  
Fluid Film ◽  
Hydrodynamic Theory ◽  
Load Carrying Capacity ◽  
Isothermal Conditions ◽  
Empirical Procedure ◽  
Load Carrying ◽  
Film Lubrication ◽  
Classical Hydrodynamic ◽  
Fluid Film Lubrication

The classical hydrodynamic theory of fluid film lubrication as described by Reynolds’ equation assumes isothermal conditions in the film. Such conditions may never exist in many engineering applications. A common practice is to calculate bearing performance with isothermal conditions at an average film temperature. This paper presents results on the load-carrying capacity of the film when thermal homogeneity does not exist. An empirical procedure is proposed for the prediction of the thermohydrodynamic behavior of the film. A hysteresis-type phenomenon in the pressure-temperature relationship is also observed.

Performance of Rotating Rough Circular Step Bearing: Characteristic of Lubrication at Nano Scale

2012 ◽  
Author(s):  
G. M. Deheri ◽  
P. R. Dave ◽  
Patel Himanshu Chimanlal
Keyword(s):  
Thin Film ◽  
Magnetic Fluid ◽  
Carrying Capacity ◽  
Couple Stress ◽  
Load Carrying Capacity ◽  
Thin Film Lubrication ◽  
Nano Scale ◽  
Load Carrying ◽  
Transverse Roughness ◽  
Film Lubrication

An endeavor has been made to investigate the effect of transverse surface roughness on the behaviour of thin film lubrication at nano scale of a magnetic fluid based rough porous rotating circular step bearing. Mainly, the combination of the properties of the surfaces, the lubricant and viscosity of the lubricant are responsible for thin film lubrication between two rough surfaces in relative motion. The effects induced by the transverse roughness and the couple stress cannot be disregarded in the regime while the ordered molecules dominate the fluid field. The random roughness of the surfaces is characterized by a random variable with non zero mean, variance and skewness. The associated Reynolds’ equation is then stochastically averaged and solved with appropriate boundary conditions to obtain the pressure distribution, leading to the calculation of load carrying capacity. It is easily observed that basically, the magnetic fluid lubricant combined with the couple stress effect is responsible for the improved performance of the bearing system. It is clearly seen that the adverse effect of transverse roughness is relatively less when considered with thin film lubrication at nano scale. The increased load carrying capacity due to variance (-ve) gets further increased due to negatively skewed roughness which becomes more pronounced owing to thin film lubrication at the nano scale. It is seen that the existence of couple stress enhances the load carrying capacity. In addition, the characteristic length contributing to the couple stress increases load carrying capacity considerably. Even, size dependent effects are noticed in the lubrication with couple stress while the thinner the lubrication film the more obvious is the effect.

Failure of Thin Film Lubrication—An Expedient for the Characterization of Lubricants

1981 ◽  
Vol 103 (4) ◽  
pp. 497-501 ◽  
Author(s):  
B. J. Tabor
Keyword(s):  
Thin Film ◽  
Chemical Composition ◽  
Bulk Viscosity ◽  
Carrying Capacity ◽  
Empirical Relation ◽  
Load Carrying Capacity ◽  
Thin Film Lubrication ◽  
Load Carrying ◽  
Film Lubrication

A method has been developed to characterize lubricants, starting from the failure of thin film lubrication in sliding concentrated steel contacts. For a number of lubricants, differing in viscosity and chemical composition, the collapse of the partial EHD film is taken as a criterion of the lubrication behavior. The contribution of viscosity and chemical composition of lubricants to the load carrying capacity of the partial EHD film at a speed of 1 m/s (P1) can be separated. This is achieved by plotting the value P1 as a function of the logarithm of the bulk viscosity (η). The following linear empirical relation P1 = β log η + α is found to be valid within the viscosity range of 2–200 • 10−3 Pa.s. Lubricants with the same chemical composition have an equal value of α.

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