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.

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.

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.

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.

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.

Study on Thin Film Lubrication With Second-Order Fluid

2002 ◽  
Vol 124 (3) ◽  
pp. 547-552 ◽  
Author(s):  
Ping Huang ◽  
Zhi-heng Li ◽  
Yong-gang Meng ◽  
Shi-zhu Wen
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
Normal Stress ◽  
Journal Bearing ◽  
Deborah Number ◽  
Second Order ◽  
Thin Film Lubrication ◽  
Stress Changes ◽  
Load Carrying ◽  
Film Lubrication

The basic lubrication equations are deduced from the original second-order fluid constitutive equations. Two examples of lubrication, a plane inclined slider and a journal bearing, are calculated respectively. The Reynolds boundary conditions are used in the calculation of the journal bearing. In this calculation, it is found that the load carrying capacities of the slider and the journal bearing are of different tendencies with the increase of the Deborah number. Furthermore, the results show that with the decrease of the film thickness, the increase of the normal stress of second-order fluid is greater than that of Newtonian fluid. Finally, it is found that the distribution of the normal stress changes significantly at a certain thickness.

scholarly journals Performance Analysis of Short Journal Bearing under Thin Film Lubrication

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Sandeep Soni ◽  
D. P. Vakharia
Keyword(s):  
Thin Film ◽  
Steady State ◽  
Performance Analysis ◽  
Layer Thickness ◽  
Journal Bearing ◽  
Adsorbed Layer ◽  
Thin Film Lubrication ◽  
Load Carrying ◽  
Film Lubrication ◽  
Steady State Performance

The steady state performance analysis of short circular journal bearing is conducted using the viscosity correction model under thin film lubrication conditions. The thickness of adsorbed molecular layers is the most critical factor in studying thin film lubrication, and is the most essential parameter that distinguishes thin film from thick film lubrication analysis. The interaction between the lubricant and the surface within a very narrow gap has been considered. The general Reynolds equation has been derived for calculating thin film lubrication parameters affecting the performance of short circular journal bearing. Investigation for the load carrying capacity, friction force, torque, and power loss for the short circular journal bearing under the consideration of adsorbed layer thickness (2δ) has been carried out. The analysis is carried out for the short bearing approximation (L/D=0.5) using Gumbel’s boundary condition. It has been found that the steady state performance parameters are comparatively higher for short circular journal bearing under the consideration of adsorbed layer thickness than for plain circular journal bearing. The load carrying capability of adsorbed layer thickness considered bearing is observed to be high for the specified operating conditions. This work could promote the understanding and research for the mechanism of the nanoscale thin film lubrication.

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