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.

A New Postulation of Viscosity and Its Application in Computation of Film Thickness in TFL1

2002 ◽  
Vol 124 (4) ◽  
pp. 811-814 ◽  
Author(s):  
Chaohui Zhang ◽  
Jianbin Luo ◽  
Shizhu Wen
Keyword(s):  
Thin Film ◽  
Experimental Data ◽  
Film Thickness ◽  
Solid Surface ◽  
Contact Area ◽  
Elastohydrodynamic Lubrication ◽  
Thin Film Lubrication ◽  
Lubrication Film ◽  
Viscosity Modification ◽  
Film Lubrication

In this paper, a viscosity modification model is developed which can be applied to describe the thin film lubrication problems. The viscosity distribution along the direction normal to solid surface is approached by a function proposed in this paper. Based on the formula, lubricating problem of thin film lubrication (TFL) in isothermal and incompressible condition is solved and the outcome is compared to the experimental data. In thin film lubrication, according to the computation outcomes, the lubrication film thickness is much greater than that in elastohydrodynamic lubrication (EHL). When the velocity is adequately low (i.e., film thickness is thin enough), the pressure distribution in the contact area is close to Hertzian distribution in which the second ridge of pressure is not obvious enough. The film shape demonstrates the earlobe-like form in thin film lubrication, which is similar to EHL while the film is comparatively thicker. The transformation relationships between film thickness and loads, velocities or atmosphere viscosity in thin film lubrication differ from those in EHL so that the transition from thin film lubrication to EHL can be clearly seen.

scholarly journals Molecular Dynamics Simulation on Thin-Film Lubrication of a Mixture of Three Alkanes

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3689
Author(s):  
Run Du ◽  
Anying Zhang ◽  
Zhihua Du ◽  
Xiaoyu Zhang
Keyword(s):  
Thin Film ◽  
Molecular Dynamics ◽  
Film Thickness ◽  
Md Simulation ◽  
Dynamics Simulation ◽  
Thin Film Lubrication ◽  
Thickness Change ◽  
Density Peaks ◽  
Initial Film ◽  
Film Lubrication

We used the COMPASS forcefield to perform molecular dynamics (MD) simulation of a mixture composed of three alkanes as the lubricant for the thin-film lubrication. The viscosity of the lubrication film in the non-working state, the final film thickness, and density distribution were investigated. The results reveal that the viscosity error among different initial film thicknesses in the non-working state is within 5%, which confirms the applicability of the model and the forcefield. The viscosity decreases oscillating as temperature increases. Whatever the initial film thickness is, the film thickness change rate with respect to pressure load is almost the same. When pressure increases, the density peaks increase. As the initial film thickness increases, the normalized thicknesses of adsorption and ordered layers decrease. In nanoscale, the density predicted by the MD simulation is higher than the prediction of the Tait equation, even if the adsorption layers is excluded.

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.

Integration of a Molecular Viscosity Model and a Continuum EHL Solution for Simulation of Thin Film Lubrication

2005 ◽  
Author(s):  
A. Martini ◽  
Y. Liu ◽  
R. Q. Snurr ◽  
Q. Wang
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
Molecular Model ◽  
Viscosity Model ◽  
Simulation Approach ◽  
Thin Film Lubrication ◽  
Molecular Film ◽  
Lubricated Contact ◽  
Molecular Viscosity ◽  
Film Lubrication

We present a simulation approach for thin film lubrication that integrates a molecular model of the film thickness-viscosity relationship in thin films with a continuum elastohydrodynamic (EHL) lubricated contact solution. Molecular simulation is used to characterize the effect of film thickness on viscosity in terms of solidification, shear thinning, and oscillation. This relationship is then incorporated into a traditional, continuum EHL solution. Film thickness distributions predicted by this integrated model are evaluated. It is found that the effect of the molecular film thickness-viscosity model is small compared to the increase in viscosity with pressure predicted by the Barus equation.

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.

Sign in / Sign up

Export Citation Format

Share Document