Elastohydrodynamic modelling of heat partition in rolling-sliding point contacts

This paper describes a comprehensive model of Elastohydrodynamic piston lubrication, incorporated the crown lands into solution domain to characterize the effect of crown-liner interactions on piston motion. Elastohydrodynamic Lubrication (EHL) analysis of a piston skirt-liner conjunction is in general a useful methodology for design analysis of pistons. The diameters of piston crown lands are much less than those of skirt and liner for typical piston designs. Therefore crown lands normally do not interact with liner under usual operating conditions and hence most of the researchers exclude crown lands from the EHL analysis and mainly focus on piston skirt. However, under some of the engine operating conditions piston crown lands play important role in the secondary dynamics and tribology aspects of pistons. During the thermodynamic cycle when piston is hot and cylinder liner is relatively colder, piston thermal expansion leads to crown-liner interaction, which necessitates EHL, asperity contact and wear considerations of piston crown along with piston skirt. The simulation methodology for piston EHL analysis uses a mass-conserving algorithm for the finite volume method solution of Reynolds equation, which is coupled to elasticity relations and Greenwood-Tripp asperity contact model. Elrod’s mass conserving algorithm enables to model and analyze partially lubricated piston-liner interface by the input of oil supply and moreover rigorously handles cavitated zones, and takes into account piston ring grooves, piston cut-outs and unlubricated areas due to piston geometry. Results are presented from parametric studies that show comparisons between the analyses of the models with piston skirt lubrication only and piston lubrication, which incorporates the crown lands to the EHL domain.

Steady-state elastohydrodynamic lubrication analysis of a metal-on-metal hip implant employing a metallic cup with an ultra-high molecular weight polyethylene backing.

Multilevel solution for thermal elastohydrodynamic lubrication of rolling/sliding circular contacts

A study for wear and fatigue on engine bearings by using EHL analysis

A numerical solution to the elastohydrodynamic lubrication (EHL) problem of two coated elastic bodies in line contact is introduced. The non-Newtonian behavior of the lubricant is incorporated into EHL analysis using Eyring's nonlinear viscous model. The surface elastic deformations are computed from full elasticity analysis of layered elastic half-space. The iterative Newton–Raphson technique is used in the numerical solution. Subsurface stresses are calculated using two different techniques, the numerical integral scheme based on Fourier transformation and the finite element method. The effects of surface coating (material and thickness) on the pressure profile and subsurface stresses are presented and discussed. Copyright © 2006 John Wiley & Sons, Ltd.

There is presently a heated debate within the field of elastohydrodynamic lubrication (EHL). Some have attributed this to a controversy regarding the shear dependence of viscosity. However, the real nature of the debate is, as it has been for more than 40 years, whether or not to correctly describe the piezoviscous effect. If real pressure dependence of viscosity were to be employed in all EHL analyses, then the true nature of shear dependence would become apparent and the debate would end.

Elastohydrodynamic lubrication analysis of a functionally graded layered bearing surface, with particular reference to 'cushion form bearings' for artificial knee joints.

The purpose of this paper is to analyze and discuss the effects of surface roughness by comparing the elastohydrodynamic lubrication(EHL) analysis of smooth surface and rough surface as the ball bearing. In order to do this, The average flow model is adapted for the interaction of the flow rheology of lubricant and surface roughness. The average Reynolds equation and the related flow factor which describes the coupled effects of surface roughness and flow rheology, the viscosity-pressure and density-pressure relations equations, the elastic deformation equation, and the force balance equation are solved simultaneously. The results show that effects of surface roughness on the film thickness and pressre distribution should be considered especially in EHL contact problems.

An elastohydrodynamic model of ferrofluid‐lubricated involute spur gears was established, and transient thermal elastohydrodynamic lubrication (EHL) analysis was conducted using multigrid method and multigrid integral method. The transient lubricant film thickness, pressure, and friction coefficient characteristics of the spur gears were compared under different carrier fluid ferrofluids. Ester‐based H01 ferrofluid was selected to further examine the lubricant film elastohydrodynamic characteristics of the involute spur gears under different loads and speeds. The results indicated that the film thickness and the inlet area pressure were the largest when hydrocarbon‐based E02 ferrofluid was used for lubrication and were the smallest when ester‐based ferrofluid H01 was used for lubrication. When ester‐based H01 ferrofluid was used, the film thickness, the inlet area pressure, and the second pressure peak increased with the increase of speed, and the second pressure peak shifted toward the inlet area. The friction coefficient and the maximum temperature gradually decreased with the increase of speed, and the second pressure peak, the friction coefficient, and the maximum temperature gradually increased with the increase of load, while the film thickness gradually decreased.

Numerical analysis of elastohydrodynamic squeeze film lubrication of total hip prostheses

This is an inceptive attempt to replace the classical Bingham fluid model with a continuous double Newtonian power law-based constitutive equation for smart lubricants like magneto-rheological, electro-rheological, and ferro-fluids. The implementation of Bingham model in hydrodynamic (HD) and elastohydrodynamic (EHD) lubrication analyses is highly challenging and inconvenient due to its inherent discontinuity. Therefore, the present work demonstrates the use of an already existing rheological model with an appropriate set of parameters to describe the flow behavior of smart lubricants in a soft-EHD lubrication algorithm based on the generalized Newtonian approach. The formation of both floating and adherent cores validates the proposed model. An extensive parametric study is also performed to explore the effects of operating speed, load, and slide-to-roll ratio on the soft-EHL characteristics. The results are very promising, showing that it's possible to customize smart lubricants to match specific operating conditions. This is achieved by adjusting the yield stress value accordingly, allowing for the desired variation in lubrication characteristics.

A simplified treatment of roughness effects in rolling-sliding elastohydrodynamic lubricated (EHL) contacts was developed by the author [4]. This analysis predicted that the original amplitude would be attenuated under the conjunction and that a decaying, complementary wave would be generated at the inlet. This complementary wave would be carried through the contact at the entrainment velocity and, for sinusoidal roughness, its wavelength would be given by λ u/v, where λ is the wavelength of the original roughness, u the entrainment velocity, and v the velocity of the rough surface. This simplified analysis predicted the degree of attenuation of the original roughness and the decay rate of the complementary wave but did not determine the amplitude of the complementary wave. This paper presents a more detailed account of this analytical approach including compressibility effects together with a more accurate allowance for the coupling between the decay of the complementary wave and its wavelength. It also extends the work, using a perturbation analysis, determining accurate values for the pressures and clearance variations produced, under rolling-sliding conjunctions, by low-amplitude roughness. The perturbation results are compared with the predictions of the simplified analysis. It will be shown that the analysis is remarkably accurate. In addition, it appears to be relatively straightforward to determine the magnitude of the complementary wave for any given operating condition. The effect of low-amplitude, sinusoidal roughness on EHL contacts can then be expressed in terms of the operating conditions together with a single value for the amplitude of the complementary wave. This simplification suggests that it may be possible to produce a method for the rapid analysis of roughness effects in rolling-sliding conjunctions without the need for any detailed EHL calculations.

In this study, an interfacial slip model including the limiting shear stress is proposed and applied to the thermal elastohydrodynamic lubrication (EHL) analysis of a helical gear pair. The main difference between the proposed model and the classical EHL model is that, the term of entrainment velocity in Reynolds equation is modified. The influences of interfacial slip, thermal effect, initial limiting shear stress and operating conditions on the tribological properties are evaluated. Due to the interfacial slip, the pressure distribution moves towards the inlet region, and the fluctuation distributions of entrainment velocity and film thickness are similar to the trigonometric function. The influence of thermal effect on interfacial slip cannot be ignored, especially in the case of high speed and heavy load. As the input torque and input rotational speed increase, the interfacial slip gradually extends to the whole meshing process.

A stiffness model for EHL contact on smooth/rough surfaces and its application in mesh stiffness calculation of the planetary gear set

Based on the Reynolds equation considering the temperature, the effection of non-newtonian and the magnetic field, the elastohydrodynamic lubrication(EHL) analysis of water-based ferrofluid journal bearing were carried out. The influence of roughness peak height and wavelength on the journal bearing surface with cosine roughness model were analysed. The results reveal that the pressure and film thickness of water-based ferrofluid wave apparently with roughness fluctuation; The fluctuation range of pressure and film thickness increase with the increase of roughness peak height, the minimal film thickness decreases; The pressure and film thickness fluctuation range become more and more sparse with the increase of roughness wavelength, the minimal film thickness increases.