scholarly journals Transient elastohydrodynamic point contact analysis using a new coupled differential deflection method Part 2: Results

2003 ◽  
Vol 217 (4) ◽  
pp. 305-322 ◽  
Author(s):  
M. J. A. Holmes ◽  
H. P. Evans ◽  
T. G. Hughes ◽  
R. W. Snidle
Keyword(s):  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Contact Analysis ◽  
Asperity Contact ◽  
Lubrication Equation ◽  
Analysis Technique ◽  
Elliptical Contact ◽  
Surface Profiles ◽  
Film Thinning ◽  
Film Collapse

The paper presents results obtained using a transient analysis technique for point contact elastohydrodynamic lubrication (EHL) problems based on a formulation that effectively couples the elastic and hydrodynamic equations. Results are presented for transverse ground surfaces in an elliptical contact that show severe film thinning at the transverse limits of the contact area. This thinning is caused by transverse (side) leakage of the lubricant from the contact in the remaining deep valley features. Comparison is made between the elliptical contact results on the entrainment centreline and the equivalent line contact analysis. This confirms the importance of edge effects as a likely cause of film collapse and scuffing failure. The surface profiles used in the analysis are taken from test discs used in scuffing experiments and from gears used in micropitting tests. Side leakage is found to be sufficiently severe to cause microasperity contact in the numerical examples presented. This contact mainly occurs close to the edges of the corresponding Hertzian area and correlates in position with the location at which scuffing is found to first occur in the earlier experiments. Comparisons are made with other numerical results for point contact configurations with sinusoidally varying surface features obtained by Zhu (2000) and considerable differences are seen in the calculated extent of asperity contact. The differences are thought to be due to the simplified treatment of the lubrication equation adopted by Zhu.

Analysis of Microelastohydrodynamic and Mixed Lubrication Effects in Gear Tooth Contacts

2003 ◽  
Author(s):  
M. J. A. Holmes ◽  
H. P. Evans ◽  
R. W. Snidle
Keyword(s):  
Contact Area ◽  
Transient Analysis ◽  
Gear Tooth ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Contact Analysis ◽  
Line Contact ◽  
Hydrodynamic Equations ◽  
Analysis Technique ◽  
Film Thinning

The paper presents results obtained using a transient analysis technique for point contact elastohydrodynamic lubrication (EHL) problems based on a formulation that couples the elastic and hydrodynamic equations. Results are presented for transverse ground surfaces in elliptical point contact that show severe film thinning at the transverse limits of the contact area. This thinning is caused by transverse leakage of the lubricant from the contact in the remaining deep valley features. A comparison is also made between the point contact results on the entrainment centre line and the equivalent line contact analysis.

scholarly journals Analysis of Mixed Lubrication Effects in Simulated Gear Tooth Contacts

2004 ◽  
Author(s):  
M. J. A. Holmes ◽  
H. P. Evans ◽  
R. W. Snidle
Keyword(s):  
Transient Analysis ◽  
Gear Tooth ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Hertzian Contact ◽  
Asperity Contact ◽  
Hydrodynamic Equations ◽  
Contact Rates ◽  
Analysis Technique ◽  
Film Thinning

The paper presents results obtained using a transient analysis technique for point contact elastohydrodynamic lubrication (EHL) problems based on a formulation that couples the elastic and hydrodynamic equations. Results are presented for transverse ground surfaces in elliptical point contact that show severe film thinning and asperity contact at the transverse limits of the contact area. This thinning is caused by transverse leakage of the lubricant from the contact in the remaining deep valley features between the surfaces. A comparison is also made between the point contact results on the entrainment centre line and the equivalent line contact analysis. The extent of asperity contact is shown to be dependent on the Hertzian contact aspect ratio. It is also shown that transverse waviness (superimposed on the roughness) of even relatively small amplitude can lead to large increases in asperity contact rates over all waviness peaks in the contact.

scholarly journals Analysis of Mixed Lubrication Effects in Simulated Gear Tooth Contacts

2005 ◽  
Vol 127 (1) ◽  
pp. 61-69 ◽  
Author(s):  
M. J. A. Holmes ◽  
H. P. Evans ◽  
R. W. Snidle
Keyword(s):  
Transient Analysis ◽  
Gear Tooth ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Hertzian Contact ◽  
Asperity Contact ◽  
Hydrodynamic Equations ◽  
Contact Rates ◽  
Analysis Technique ◽  
Film Thinning

The paper presents results obtained using a transient analysis technique for point contact elastohydrodynamic lubrication (EHL) problems based on a formulation that couples the elastic and hydrodynamic equations. Results are presented for transverse ground surfaces in elliptical point contact that show severe film thinning and asperity contact at the transverse limits of the contact area. This thinning is caused by transverse leakage of the lubricant from the contact in the remaining deep valley features between the surfaces. A comparison is also made between the point contact results on the entrainment center line and the equivalent line contact analysis. The extent of asperity contact is shown to be dependent on the Hertzian contact aspect ratio. It is also shown that transverse waviness (superimposed on the roughness) of even relatively small amplitude can lead to large increases in asperity contact rates over all waviness peaks in the contact.

Point Contact EHL Based on Optically Measured Three-Dimensional Rough Surfaces

1997 ◽  
Vol 119 (3) ◽  
pp. 375-384 ◽  
Author(s):  
Dong Zhu ◽  
Xiaolan Ai
Keyword(s):  
Rough Surface ◽  
Rough Surfaces ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Peak Height ◽  
Machining Process ◽  
Maximum Pressure ◽  
Pressure Peak ◽  
Surface Profiles

This paper presents a numerical solution for the elastohydrodynamic lubrication in point contacts, using optically measured three-dimensional rough surface profiles as input data. The multi-grid computer program originally developed by Ai and Cheng (1993, 1994) is modified, so that both contacting surfaces can be three-dimensional measured rough surfaces moving at different velocities. Many different engineering surfaces are measured and analyzed in the present study, demonstrating that the numerical analysis is practical for real surfaces of bearings, cams, gears and other components, as long as a significant EHL film still exists. In addition, discussions are given in this paper for the effects of three-dimensional rough surface topography, which is related to machining process. It appears that, for the circular contact cases analyzed, surface roughness texture and orientation do not have a significant effect on the average film thickness, but they do affect the maximum pressure peak height and asperity deformation in the contact zone considerably.

Elastohydrodynamic Lubrication of Circumferentially Finished Rollers having Sinusoidal Roughness

1987 ◽  
Vol 201 (1) ◽  
pp. 29-36 ◽  
Author(s):  
G Karami ◽  
H P Evans ◽  
R W Snidle
Keyword(s):  
Film Thickness ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
Axial Direction ◽  
Constant Load ◽  
Asperity Contact ◽  
Asperity Contacts ◽  
Roughness Amplitude ◽  
Large Roughness

The paper describes an isothermal elastohydrodynamic lubrication analysis of rollers having circumferential sinusoidal roughness. Theoretical results are shown which demonstrate the influence of roughness amplitude on the distribution of hydrodynamic pressure and film thickness at constant load and constant roughness wavelength. At a large roughness amplitude the hydrodynamic pressure in the valleys between asperity contacts is insignificant and each asperity contact behaves as an ‘isolated’ elastohydrodynamic point contact. As the roughness is reduced, however, the valley pressures build up, the pressure becomes more uniformly distributed in the axial direction and the minimum film thickness increases.

Analysis of Micro-Elastohydrodynamic Lubrication and Prediction of Surface Fatigue Damage in Micropitting Tests on Helical Gears

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
H. P. Evans ◽  
R. W. Snidle ◽  
K. J. Sharif ◽  
B. A. Shaw ◽  
J. Zhang
Keyword(s):  
Damage Accumulation ◽  
Gear Tooth ◽  
Contact Fatigue ◽  
Elastohydrodynamic Lubrication ◽  
Tooth Surface ◽  
Asperity Contact ◽  
Surface Fatigue ◽  
Tooth Surfaces ◽  
Surface Profiles ◽  
Alternative Processes

The paper describes results obtained from the micro-elastohydrodynamic lubrication (micro-EHL) modeling of the gear tooth contacts used in micropitting tests together with a contact fatigue and damage accumulation analysis of the surfaces involved. Tooth surface profiles were acquired from pairs of helical test gears and micro-EHL simulations were performed corresponding to surfaces that actually came into contact during the meshing cycle. Plane strain fatigue and damage accumulation analysis shows that the predicted damage is concentrated close to the tooth surfaces and this supports the view that micropitting arises from fatigue at the asperity contact level. A comparison of the micropitting performance of gears finish-ground by two alternative processes (generation-grinding and form-grinding) suggests that 3D “waviness” may be an important factor in explaining their different micropitting behavior.

On the Behavior of Friction in Lubricated Point Contact With Provision for Surface Roughness

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
H. Sojoudi ◽  
M. M. Khonsari
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Numerical Solutions ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
Operating Conditions ◽  
Asperity Contact ◽  
Type Curve ◽  
Lift Off

This paper presents a simple approach to predict the behavior of friction coefficient in the sliding lubricated point contact. Based on the load-sharing concept, the total applied load is supported by the combination of hydrodynamic film and asperity contact. The asperity contact load is determined in terms of maximum Hertzian pressure in the point contact while the fluid hydrodynamic pressure is calculated through adapting the available numerical solutions of elastohydrodynamic lubrication (EHL) film thickness formula for smooth surfaces. The simulations presented cover the entire lubrication regime including full-film EHL, mixed-lubrication, and boundary-lubrication. The results of friction, when plotted as a function of the sum velocity, result in the familiar Stribeck-type curve. The simulations are verified by comparing the results with published experimental data. A parametric study is conducted to investigate the influence of operating condition on the behavior of friction coefficient. A series of simulations is performed under various operating conditions to explore the behavior of lift-off speed. An equation is proposed to predict the lift-off speed in sliding lubricated point contact, which takes into account the surface roughness.

Scuffing Theory Modeling and Experimental Correlations

1991 ◽  
Vol 113 (2) ◽  
pp. 327-334 ◽  
Author(s):  
S. C. Lee ◽  
H. S. Cheng
Keyword(s):  
Preliminary Investigation ◽  
Elastohydrodynamic Lubrication ◽  
Pressure Effects ◽  
Asperity Contact ◽  
Contact Conditions ◽  
Surface Profiles ◽  
Temperature And Pressure ◽  
Rough Surface Contact ◽  
Contact Pressures ◽  
Temperature And Pressure Effects

The scuffing behavior for contacts operating in the partial elastohydrodynamic lubrication regime is shown to be greatly affected by the asperity contact temperatures and the lubricant pressures inside the elastohydrodynamic lubrication conjunction. A scuffing model which takes into account the temperature and pressure effects for predicting the onset of scuffing failure has been developed. This model is based on the lubricant molecule physisorption theory and is capable of predicting the scuffing failures for general contact conditions including the boundary lubrication contacts and the elastohydrodynamic lubrication (ehl) contacts. A preliminary investigation into this model showed a good correlation existing between the theory and some scuffing experiment results conducted on a twin disk machine. However, more experimentation is necessary to further ascertain the validity of this new model. To validate the new scuffing theory, a method for calculating the asperity flash temperatures is formulated. The flash temperature calculations were performed using the actual digitized run-in surface profiles of the mating bodies. The necessary informations for calculating the flash temperatures such as, the real areas of contact and the asperity contact pressures were all determined using a recently developed rough surface contact simulation model.

A New Deterministic Model for Mixed Lubricated Point Contact With High Accuracy

2020 ◽  
pp. 1-33
Author(s):  
Shuowen Zhang ◽  
Chenhui Zhang
Keyword(s):  
High Performance ◽  
Deterministic Model ◽  
Contact Region ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Mixed Lubrication ◽  
Stribeck Curve ◽  
Asperity Contact ◽  
Lubrication Regime ◽  
Pressure Boundary Condition

Abstract Mixed lubrication is a major lubrication regime in the presence of surface roughness. A deterministic model is established to solve mixed lubricated point contact in this paper, using a new method to solve asperity contact region in mixed lubrication. Treatment of pressure boundary condition between elastohydrodynamic lubrication region and asperity contact region is discussed. The new model is capable of calculating typical Stribeck curve and analyzing transition of lubrication regime, from full film lubrication to boundary lubrication. Moreover, final result of the model is independent of pressure initialization. High performance in accuracy and convergence has been achieved, which is of great importance for further lubrication modelling with consideration of nano-scale roughness, intermolecular and surface forces.

Analysis of Micro-Elastohydrodynamic Lubrication and Surface Fatigue in Gear Micropitting Tests

2011 ◽  
Author(s):  
H. P. Evans ◽  
R. W. Snidle ◽  
K. J. Sharif
Keyword(s):  
Damage Accumulation ◽  
Gear Tooth ◽  
Contact Fatigue ◽  
Elastohydrodynamic Lubrication ◽  
Tooth Surface ◽  
Asperity Contact ◽  
Cycle Fatigue ◽  
Surface Fatigue ◽  
Tooth Surfaces ◽  
Surface Profiles

The paper describes results obtained from the micro-elastohydrodynamic lubrication (micro-EHL) modelling of the gear tooth contacts used in micropitting tests together with contact fatigue and damage accumulation analysis of the surfaces involved. Tooth surface profiles were acquired from pairs of helical test gears and micro-EHL simulations were performed corresponding to surfaces that actually came into contact during the meshing cycle. Fatigue and damage accumulation analysis shows that predicted damage is concentrated close to the tooth surfaces and this strongly suggests that micropitting damage arises from fatigue at the asperity contact level.

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