Surface Roughness Effects on Fatigue in Partial EHD Lubrication

1976 ◽  
Vol 98 (4) ◽  
pp. 530-535 ◽  
Author(s):  
D. F. Li ◽  
J. J. Kauzlarich ◽  
W. E. Jamison
Keyword(s):  
Fatigue Life ◽  
Roughness Parameter ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Surface Model ◽  
Endurance Test ◽  
Roughness Effects ◽  
Surface Fatigue ◽  
Ehd Lubrication ◽  
Rolling Element

A simple surface originated fatigue theory has been developed to study the effects of surface topography on the fatigue life of rolling element bearings. The bearing surface fatigue life is assumed to relate to the magnitude of the average shearing stresses generated at the interacting asperities on the surfaces that are separated by an elastohydrodynamic lubricant film of some thickness. Utilizing a published rough surface model, it is possible to express the relative fatigue life of a bearing as a function of the lubricant film thickness to roughness ratio h/σ and a roughness parameter R. Comparison of the theory to sets of published endurance test data has been carried out. Possibilities of fatigue life prediction of both roller and ball bearings in the partial elastohydrodynamic lubrication regime are discussed.

The Effect of Piston Skirt Profile on EHD Lubrication in an Internal Combustion Engine

2013 ◽  
Vol 787 ◽  
pp. 704-710 ◽  
Author(s):  
Kellaci Ahmed ◽  
Khelidj Benyoucef ◽  
Mazouzi Redha ◽  
Lounis Mourad
Keyword(s):  
Internal Combustion Engine ◽  
Combustion Engine ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Elastic Equilibrium ◽  
Internal Combustion ◽  
Lubricant Film ◽  
Piston Skirt ◽  
Ehd Lubrication ◽  
Finite Differences Method

This investigation is concerned with the elastohydrodynamic lubrication of the piston skirt / cylinder link of an internal combustion engine. In such compliant structures, the thickness of the lubricant film depends not only on the elastic deformation elements of the mechanism but also on their profiles. We have developed a computer program to study the effect of the profile of the piston skirt on the lubricant film. This program is based on a two-dimensional description of the lubricant film flow and a three-dimensional deformation of solids. The Reynolds equation defines the behavior of hydrodynamic film of oil in the liaison piston skirt / cylinder, and the equations of static and elastic equilibrium quantify the behavior of the structure. These Equations are solved numerically by using the finite differences method.

scholarly journals Dynamic Capacity and Surface Fatigue Life for Spur and Helical Gears

1976 ◽  
Vol 98 (2) ◽  
pp. 267-274 ◽  
Author(s):  
J. J. Coy ◽  
D. P. Townsend ◽  
E. V. Zaretsky
Keyword(s):  
Fatigue Life ◽  
Gear Train ◽  
Rolling Element Bearing ◽  
Tangential Load ◽  
Dynamic Capacity ◽  
Probability Of Survival ◽  
Surface Fatigue ◽  
Rolling Element ◽  
Life Model ◽  
Life Predictions

A mathematical model for surface fatigue life of gear, pinion, or entire meshing gear train is given. The theory is based on the statistical approach used by Lundberg and Palmgren for rolling-element bearings. Also equations are presented which give the dynamic capacity of the gear set. The dynamic capacity is the transmitted tangential load which gives a 90 percent probability of survival of the gear set for one million pinion revolutions. The analytical results were compared with test data for a set of AISI 9310 spur gears operating at a maximum Hertz stress of 1.71 × 109 N/m2 (248,000 psi) and 10,000 rpm. The theoretical life predictions were very good when material constants obtained from rolling-element bearing tests were used in the gear life model.

scholarly journals Grease film thickness measurement in rolling bearing contacts

2020 ◽  
pp. 135065012096127
Author(s):  
Xingnan Zhang ◽  
Romeo Glovnea
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Rolling Bearing ◽  
Thickness Measurement ◽  
Lubricant Film ◽  
Rolling Element Bearings ◽  
Lubricant Film Thickness ◽  
Rolling Bearings ◽  
Rolling Element ◽  
Film Thickness Measurement

Rolling bearings are the second most used machine components. They work in what it is called elastohydrodynamic lubrication regime. The geometry of rolling element bearings makes the direct measurement of the lubricant film thickness a challenging task. Optical interferometry is widely used in laboratory conditions for studying elastohydrodynamic lubrication however it cannot be used directly in rolling element bearings thus the only suitable methods are electrical techniques. Of these, film thickness measurement based on electrical capacitance of the contacts has been used in the past by a number of authors. One of the limitations of the capacitance method, when used in rolling bearings, is that it cannot distinguish between the contacts of every rolling element and raceway on one hand and on the other between the inner and outer ring contacts. In the present study the authors used an original test rig which can measure the film thickness for only one ball and separately for the inner and outer rings of a radial ball bearing. This paper thus shows for the first-time results of the lubricant film thickness, at the inner and outer raceways, in grease lubricated rolling bearings.

EHL Modeling for Nonhomogeneous Materials: The Effect of Material Inclusions

2007 ◽  
Vol 129 (2) ◽  
pp. 256-273 ◽  
Author(s):  
Trevor S. Slack ◽  
Nihar Raje ◽  
Farshid Sadeghi ◽  
Gary Doll ◽  
Michael R. Hoeprich
Keyword(s):  
Film Thickness ◽  
Pressure Distribution ◽  
Fatigue Crack Initiation ◽  
Base Material ◽  
Elastohydrodynamic Lubrication ◽  
Elastic Half Space ◽  
Lubricant Film ◽  
Stress Concentrations ◽  
Rolling Element ◽  
Bearing Materials

Inclusions are common in bearing materials and are a primary site for subsurface fatigue crack initiation in rolling element bearings. This paper presents a new approach for computing the pressure, film thickness, and subsurface stresses in an elastohydrodynamic lubrication (EHL) contact when inclusions are present in the elastic half-space. The approach is based on using the discrete element method to determine the surface elastic deformation in the EHL film thickness equation. The model is validated through comparison with the smooth EHL line contact results generated using linear elasticity. Studies are then carried out to investigate the effects of size, location, orientation, and elastic properties of inclusions on the EHL pressure and film thickness profiles. Both inclusions that are stiffer than and/or softer than the base material are seen to have effects on the pressure distribution within the lubricant film and to give rise to stress concentrations. For inclusions that are stiffer than the base material (hard inclusions), the pressure distribution within the lubricant film behaves as though there is a bump on the surface, whereas for inclusions that are less stiff than the base material (soft inclusions), the pressure distribution behaves in a manner similar to that of a dented surface. Inclusions close to the surface cause significant changes in the contact stresses that are very significant considering the stress life relationship. For inclusions that are located deep within the surface, there is little change in the EHL pressure and film thickness.

scholarly journals Understanding micropitting in gears

2015 ◽  
Vol 230 (7-8) ◽  
pp. 1276-1289 ◽  
Author(s):  
A Clarke ◽  
HP Evans ◽  
RW Snidle
Keyword(s):  
Gear Tooth ◽  
Elastohydrodynamic Lubrication ◽  
Erosive Wear ◽  
Basic Mechanism ◽  
Operating Conditions ◽  
Residual Effects ◽  
Roughness Effects ◽  
Near Surface ◽  
Surface Fatigue ◽  
Tooth Surfaces

Micropitting is a serious form of erosive wear, which can occur on the teeth of transmission gears. It is associated with roughness effects and surface fatigue and has become a particular problem in the speed-increasing gearboxes of wind turbines. This paper reviews the contributions which the authors have made towards an understanding of the basic mechanism of micropitting in gears based on analysis of the contact mechanics and elastohydrodynamic lubrication (EHL) of gear tooth surfaces under realistic operating conditions. Results are presented which demonstrate the crucial influence of EHL film thickness in relation to roughness (the ‘Λ ratio’) on predicted contact and near-surface fatigue. The important effect of plastic deformation, which takes place during the initial stage of running-in of gears, has also been investigated, and it has been shown that significant residual effects occur, which can contribute to the early formation of surface-initiated cracks.

Applications of vibro-acoustic measurement and analysis in conjunction with tribological parameters to assess surface fatigue wear developed in the roller-bearing system

2021 ◽  
pp. 135065012098246
Author(s):  
Shashikant Pandey ◽  
Muniyappa Amarnath
Keyword(s):  
Roller Bearing ◽  
Operating Conditions ◽  
Rolling Contact ◽  
Stribeck Curve ◽  
Fatigue Wear ◽  
Surface Fatigue ◽  
Rolling Element ◽  
Measurement And Analysis ◽  
Contact Surfaces ◽  
Bearing System

Rolling-element bearings are the most commonly used components in all rotating machinery. The variations in the operating conditions such as an increase in the number of operating cycles, load, speed, service temperature, and lubricant degradation result in the development of various defects such as pitting, spalling, scuffing, scoring, etc. The defects that appeared on rolling contact surfaces cause surface deterioration and change in the vibration and sound levels of the bearing system. The present experimental investigations are aimed at assessing the surface fatigue wear that appears on the contact surfaces of roller bearings. The studies considered the estimation of specific film thickness, analysis of surface fatigue wear developed on the rolling-element surfaces, surface roughness analysis, grease degradation analysis using Fourier transform infrared radiation, and vibration and sound signal measurement and analysis. The results obtained from the experimental investigation provide a good correlation between surface wear, vibration, and sound signals with a transition in the lubrication regimes in the Stribeck curve.

Effects of out-of-contact lubricant channeling on friction and film thickness in starved elastohydrodynamic lubrication point contacts

2016 ◽  
Vol 231 (4) ◽  
pp. 432-440 ◽  
Author(s):  
Fadi Ali ◽  
Ivan Křupka ◽  
Martin Hartl
Keyword(s):  
Film Thickness ◽  
Digital Camera ◽  
Elastohydrodynamic Lubrication ◽  
Contact Condition ◽  
Friction Reduction ◽  
Rolling Element Bearings ◽  
Point Contacts ◽  
Practical Applications ◽  
Rolling Element ◽  
Ball On Disc

This study presents experimental results on the effect of out-of-contact lubricant channeling on the tribological performance of nonconformal contacts under starved lubrication. Channeling of lubricant was carried out by adding a slider with a limited slot for scraping the displaced lubricant on one of mating surfaces (ball). Thus, the scraped lubricant is forced to flow back into the depleted track through the limited slot resulting in robust replenishment. The measurements have been conducted using optical tribometer (ball-on-disc) equipped with a digital camera and torque sensor. The effect of lubricant channeling was compared to the original contact condition by means of measuring friction and film thickness. The results show that the out-of-contact lubricant channeling leads to a significant enhancement of film thickness and friction reduction under starved conditions. Indeed, the starved elastohydrodynamic lubrication contacts transformed to the fully flooded regime after introducing the flow reconditioning. Moreover, the film thickness decay over time, which is common with starved elastohydrodynamic lubrication contacts, has not been observed in the case of lubricant channeling. However, the beneficial effect of lubricant channeling diminishes as the original contact condition tends to the fully flooded regime. The results of this study can be easily implemented in practical applications such as radial and thrust rolling-element bearings.

Quantitative Analysis of Reynolds and Navier–Stokes Based Modeling Approaches for Isothermal Newtonian Elastohydrodynamic Lubrication

2021 ◽  
Vol 143 (12) ◽  
Author(s):  
Leoluca Scurria ◽  
Tommaso Tamarozzi ◽  
Oleg Voronkov ◽  
Dieter Fauconnier
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Thickness Distribution ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Shear Stresses ◽  
Low Viscosity ◽  
Fluid Film Thickness

Abstract When simulating elastohydrodynamic lubrication, two main approaches are usually followed to predict the pressure and fluid film thickness distribution throughout the contact. The conventional approach relies on the Reynolds equation to describe the thin lubricant film, which is coupled to a Boussinesq description of the linear elastic deformation of the solids. A more accurate, yet a time-consuming method is the use of computational fluid dynamics in which the Navier–Stokes equations describe the flow of the thin lubricant film, coupled to a finite element solver for the description of the local contact deformation. This investigation aims at assessing both methods for different lubrication conditions in different elastohydrodynamic lubrication (EHL) regimes and quantify their differences to understand advantages and limitations of both methods. This investigation shows how the results from both approaches deviate for three scenarios: (1) inertial contributions (Re > 1), i.e., thick films, high speed, and low viscosity; (2) high shear stresses leading to secondary flows; and (3) large deformations of the solids leading to inaccuracies of the Boussinesq equation.

Numerical Modeling of Mixed Lubrication and Flash Temperature in EHL Elliptical Contacts

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
Neelesh Deolalikar ◽  
Farshid Sadeghi ◽  
Sean Marble
Keyword(s):  
Surface Deformation ◽  
Elastohydrodynamic Lubrication ◽  
Mixed Lubrication ◽  
Asperity Contact ◽  
Lubrication Regime ◽  
Predicting Performance ◽  
Pure Rolling ◽  
Rolling Element ◽  
Contact Pressures ◽  
Film Lubrication

Highly loaded ball and rolling element bearings are often required to operate in the mixed elastohydrodynamic lubrication regime in which surface asperity contact occurs simultaneously during the lubrication process. Predicting performance (i.e., pressure, temperature) of components operating in this regime is important as the high asperity contact pressures can significantly reduce the fatigue life of the interacting components. In this study, a deterministic mixed lubrication model was developed to determine the pressure and temperature of mixed lubricated circular and elliptic contacts for measured and simulated surfaces operating under pure rolling and rolling/sliding condition. In this model, we simultaneously solve for lubricant and asperity contact pressures. The model allows investigation of the condition and transition from boundary to full-film lubrication. The variation of contact area and load ratios is examined for various velocities and slide-to-roll ratios. The mixed lubricated model is also used to predict the transient flash temperatures occurring in contacts due to asperity contact interactions and friction. In order to significantly reduce the computational efforts associated with surface deformation and temperature calculation, the fast Fourier transform algorithm is implemented.

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