Transient Elastohydrodynamic Lubrication Film Thickness During Normal Approach Considering Shear-Thinning and Linear Piezoviscous Oils

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Punit Kumar ◽  
Tapash Jyoti Kalita
Keyword(s):  
Film Thickness ◽  
Impact Loading ◽  
Elastohydrodynamic Lubrication ◽  
Shear Thinning ◽  
Line Contact ◽  
State Behavior ◽  
Lubrication Film ◽  
Film Collapse ◽  
Low Pressures ◽  
Viscosity Dependence

Transient film thickness behavior is investigated using full elastohydrodynamic lubrication (EHL) line contact simulations during film collapse due to sudden halt and impact loading. Due attention is given to realistic shear-thinning behavior and comparisons are made with a largely ignored class of EHL lubricants that exhibit linear pressure–viscosity dependence at low pressures. The EHL film collapse is found to be governed by the piezoviscous response and the linear P–V oils exhibit rapidly collapsing EHL entrapment. Under impact loading, the transient film thickness deviates markedly from the corresponding steady-state behavior and this departure is a function of lubricant rheology.

Effect of Roughness Orientation on the Elastohydrodynamic Lubrication Film Thickness

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Dong Zhu ◽  
Q. Jane Wang
Keyword(s):  
Film Thickness ◽  
Stochastic Models ◽  
Deterministic Model ◽  
Elastohydrodynamic Lubrication ◽  
Contact Problems ◽  
Operating Conditions ◽  
Orientation Effect ◽  
Line Contact ◽  
Lubrication Film ◽  
Dry Contact

Effect of roughness orientation on lubricant film thickness has been an important issue of surface design, attracting much attention since the 1970 s. A systematical study, however, is still needed for various contact types in an extended range of operating conditions, especially in mixed lubrication cases with film thickness to roughness ratio (λ ratio) smaller than 0.5. The present study employs a deterministic mixed elastohydrodynamic lubrication (EHL) model to investigate the performance of lubricating films in different types of contact geometry, including the line contact, circular contact, and elliptical contacts of various ellipticity ratios. The speed range for analyzed cases covers 11 orders of magnitude so that the entire transition from full-film and mixed EHL down to dry contact (corresponding λ ratio from about 3.5 down to 0.001 or so) is simulated. Three types of machined surfaces are used, representing transverse, longitudinal, and isotropic roughness, respectively. The line contact results are compared with those from the stochastic models by Patir and Cheng (“Effect of Surface Roughness Orientation on the Central Film Thickness in EHD Contacts,” Proc. 5th Leeds-Lyon Symp. on Tribol., 1978, pp. 15–21) and the influence of roughness orientation predicted by the deterministic model is found to be less significant than that by the stochastic models, although the basic trends are about the same when λ > 0.5. The orientation effect for circular or elliptical contact problems appears to be more complicated than that for line contacts due to the existence of significant lateral flows. In circular contacts, or elliptical contacts with the ellipticity ratio smaller than one, the longitudinal roughness may become more favorable than the isotropic and transverse. Overall, the orientation effect is significant in the mixed EHL regime where theλratio is roughly in the range from 0.05 to 1.0. It is relatively insignificant for both the full-film EHL (λ > 1.2 or so) and the boundary lubrication/dry contact (λ < 0.025 ∼ 0.05).

Effect of Load Variation on Elastohydrodynamic Lubrication Film Collapse

2014 ◽  
Vol 592-594 ◽  
pp. 1366-1370
Author(s):  
Tapash Jyoti Kalita ◽  
Punit Kumar
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Elastohydrodynamic Lubrication ◽  
Transient Behavior ◽  
Computer Code ◽  
Practical Situation ◽  
Lubrication Film ◽  
Newton Raphson ◽  
Simulation Results ◽  
Film Collapse

Elastohydrodynamic line contact simulations have been carried out in the present study. A practical situation of transient EHL film collapse has been analyzed. The aim is to observe the effect of variation of maximum Hertzian pressure (PH) on transient behavior of EHL film thickness (H).The analysis is based upon classical Reynolds equation considering time variation. The simulation results pertaining to EHL film thickness calculated using linear pressure-viscosity relationship have been compared for different values of load. It has been observed that film thickness reduces with increase in load. Similar results are obtained using exponential pressure-viscosity relationship and compared with those for linear pressure-viscosity. The EHL equations are solved by discretizing Reynolds equation and load equilibrium equation along with other equations using Newton-Raphson technique with the help of a computer code.

On the elastohydrodynamic analysis of shear-thinning fluids

2007 ◽  
Vol 463 (2088) ◽  
pp. 3271-3290 ◽  
Author(s):  
J.Y Jang ◽  
M.M Khonsari ◽  
S Bair
Keyword(s):  
Film Thickness ◽  
Numerical Solutions ◽  
Elastohydrodynamic Lubrication ◽  
Shear Thinning ◽  
Line Contact ◽  
Carreau Model ◽  
Shear Thinning Fluids ◽  
Realistic Prediction ◽  
Comparison With Experiments ◽  
Ehl Contact

Realistic prediction of the characteristics of the elastohydrodynamic lubrication (EHL) contact requires consideration of the appropriate constitutive equation for the lubricant. In many applications, the lubricant exhibits a shear-thinning behaviour which significantly affects the film thickness. In this paper, we present a generalized formulation that can efficiently treat shear-thinning fluids with provision for compressibility in the EHL line contact. Specifically, the Carreau model and the sinh-law model are investigated. An extensive set of numerical solutions and comparison with experiments reveal that the Carreau equation properly captures the film thickness behaviour under both rolling and sliding conditions.

Effect of arbitrary entrainment angle in elastohydrodynamic lubrication elliptical and circular contacts

2019 ◽  
Vol 234 (3) ◽  
pp. 424-434
Author(s):  
Puneet Katyal ◽  
Punit Kumar
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Shear Thinning ◽  
Surface Velocity ◽  
Rheological Models ◽  
Lubrication Film ◽  
Lubrication Performance ◽  
Cam Follower ◽  
Machine Elements ◽  
Lubrication Characteristics

Conventional elastohydrodynamic lubrication models assume parallel surface velocities such as in cam-follower and ball bearing systems. However, many important machine elements like hypoid gear and spiral bevel, the sliding and entrainment velocities are along different directions that could possibly influence the elastohydrodynamic lubrication performance characteristics significantly. For such complex conditions, the existing film thickness formulae and shear-thinning correction factors available in the literature are not suitable. Therefore, this paper investigates the effect of arbitrarily oriented surface velocity vectors on elastohydrodynamic lubrication characteristics considering realistic rheological models and experimentally established viscosity–pressure and compressibility laws. The Reynolds equation employed herein includes the surface velocity components along both the reference axes in the plane of contact. The elastohydrodynamic lubrication film thickness is found to deviate up to a maximum of 61% with respect to its conventional value. This deviation in film thickness behavior is shown to be a function of ellipticity and shear-thinning parameters.

Professor Duncan Dowson, a source of inspiration

2021 ◽  
pp. 135065012110507
Author(s):  
Ton Lubrecht ◽  
Nans Biboulet ◽  
Kees Venner
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Current Paper ◽  
Line Contact ◽  
Lubrication Film ◽  
Pure Rolling ◽  
Thickness Prediction ◽  
Elliptical Contact

The current paper highlights the contribution of the Dowson and Higginson work to numerical line contact elastohydrodynamic lubrication film thickness prediction and the Hamrock and Dowson contribution to the film thickness prediction in elliptical contacts. This paper shows that, even by today’s standards, both the numerical pressure and film thickness results and the curve-fitted film thickness predictions are very accurate. As for the elliptical results, the authors show that the original predictions remain surprisingly accurate for moderately elliptical contact. For very long elliptical contacts, their prediction does not tend to a line contact asymptote. This paper then concludes that the predicted pressure spikes by Dowson, Higginson, and Hamrock are correct in shape and amplitude, at least near pure rolling conditions.

Scale Effects in Generalized Newtonian Elastohydrodynamic Films

2008 ◽  
Author(s):  
I. I. Kudish ◽  
P. Kumar ◽  
M. M. Khonsary ◽  
S. Bair
Keyword(s):  
Film Thickness ◽  
Scale Effects ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Viscosity Coefficient ◽  
Shear Thinning ◽  
Effective Pressure ◽  
Practical Advantage ◽  
Inlet Zone ◽  
Real Machine

The prediction of elastohydrodynamic lubrication (EHL) film thickness requires knowledge of the lubricant properties. Today, in many instances, the properties have been obtained from a measurement of the central film thickness in an optical EHL point contact simulator and the assumption of a classical Newtonian film thickness formula. This technique has the practical advantage of using an effective pressure-viscosity coefficient which compensates for shear-thinning. We have shown by a perturbation analysis and by a full EHL numerical solution that the practice of extrapolating from a laboratory scale measurement of film thickness to the film thickness of an operating contact within a real machine may substantially overestimate the film thickness in the real machine if the machine scale is smaller and the lubricant is shear-thinning in the inlet zone.

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.

Calculation of Elastohydrodynamic Lubrication Film Thickness for Hip Prostheses During Normal Walking

1990 ◽  
Vol 33 (2) ◽  
pp. 239-245 ◽  
Author(s):  
Cheng-Tao Wang ◽  
Yi-Ling Wang ◽  
Qing-Li Chen ◽  
Min-Run Yang
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Normal Walking ◽  
Hip Prostheses ◽  
Lubrication Film

Size effect on thermal elastohydrodynamic lubrication of industrial chain bush-pin hinge pair

2019 ◽  
Vol 71 (9) ◽  
pp. 1080-1085 ◽  
Author(s):  
Mingyu Zhang ◽  
Jing Wang ◽  
Yi Liu ◽  
Longjie Dai ◽  
Zhaohua Shang
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Temperature Rise ◽  
Elastohydrodynamic Lubrication ◽  
Curvature Radius ◽  
Line Contact ◽  
Content Type ◽  
Oil Film ◽  
Industrial Chain ◽  
Infinite Line

Purpose The purpose of this paper is to use elastohydrodynamic lubrication (EHL) theory to study the variation of the equivalent curvature radius “R” on the change of oil film thickness, pressure, temperature rise and friction coefficient in the contact zone between bush-pin in industrial chain drive. Design/methodology/approach In this paper, the contact between bush and pin is simplified as infinitely long line contact. The lubrication state is studied by numerical simulation using steady-state line contact thermal EHL. The two constitutive equations, namely, Newton fluid and Ree–Eyring fluid are used in the calculations. Findings It is found that with the increase of equivalent curvature radius, the thickness of oil film decreases and the temperature rise increases. Under the same condition, the friction coefficient of Newton fluid is higher than that of Ree–Eyring fluid. When the load increases, the oil film thickness decreases, the temperature rise increases and the friction coefficient decreases; and the film thickness increases with the increase of the entraining speed under the condition “R < 1,000 mm”. Research limitations/implications The infinite line contact assumption is only an approximation. For example, the distances between the two inner plates are 5.72 mm, by considering the two parts assembled into the inner plates, the total length of the bush is less than 6 mm. The diameter of the pin and the bore diameter of the bush are 3.28 and 3.33 mm. However, the infinite line contact is also helpful in understanding the general variation of oil film characteristics and provides a reference for the future study of finite line contact of chain problems. Originality/value The change of the equivalent radius R on the variation of the oil film in the contact of the bush and the pin in industrial chain drive was investigated. The size effect influences the lubrication characteristic greatly in the bush-pin pair.

Sign in / Sign up

Export Citation Format

Share Document