On the Negative Influence of Roller-End Axial Profiling on Friction in Thermal Elastohydrodynamic Lubricated Finite Line Contacts

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
W. Habchi
Keyword(s):  
Fatigue Life ◽  
Elastohydrodynamic Lubrication ◽  
Element Model ◽  
Negative Influence ◽  
Frictional Behavior ◽  
Minimum Film Thickness ◽  
Line Contacts ◽  
Negative Effect ◽  
Finite Line ◽  
Reducing Stress

Abstract This paper presents a finite element model for the solution of thermal elastohydrodynamic lubrication in finite line contacts, including edge effects. The model is used to investigate the influence of roller-end axial profiling on the frictional behavior of such contacts. Roller-end profiling in finite line contacts has always been used to enhance fatigue life by increasing lubricant minimum film thickness and reducing stress concentration at roller ends. The influence on friction on the other hand has often been overlooked in the literature. The current work reveals that roller-end profiling has a negative effect on friction. In fact, it turns out that the improvement in fatigue life comes at the expense of increased friction.

Thermal Elastohydrodynamic Lubrication of Axially Crowned Rollers

2021 ◽  
pp. 1-21
Author(s):  
Wassim Habchi
Keyword(s):  
Film Thickness ◽  
Design Parameter ◽  
Numerical Study ◽  
Elastohydrodynamic Lubrication ◽  
Negative Influence ◽  
Reference Case ◽  
Critical Design ◽  
Lubrication Performance ◽  
Minimum Film Thickness ◽  
Line Contacts

Abstract This work presents a comprehensive numerical study of thermal elastohydrodynamic lubrication performance in axially crowned rollers, based on a full-system finite element approach. Axial crowning has always been introduced to finite line contacts, as a mean for improving film thickness. Its influence on friction has often been overlooked though. The current work reveals that axial crowning has a negative influence on friction, increasing it significantly with respect to the reference case of straight rollers. It is shown that, with increased crowning height (or reduced crowning radius), minimum film thickness is increased, but so is friction. Therefore, film thickness enhancement comes at the expense of a deterioration in friction. Besides, achieving sufficient enhancements in minimum film thickness would require using relatively low crowning radii, which would lead to a substantial increase in friction. The frictional increase is traced back to an overall increase in contact pressures and effective contact area within the lubricating conjunction. It is also shown that, when film thickness is the most critical design parameter, the best compromise between enhanced film thickness and deteriorated friction would be to combine axial crowning with roller-end profiling. However, when friction is the most critical design parameter, a simple roller-end profiling would offer the best compromise.

Elastohydrodynamic Lubrication of Finite Line Contacts

1983 ◽  
Vol 105 (4) ◽  
pp. 598-604 ◽  
Author(s):  
A. Mostofi ◽  
R. Gohar
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Mineral Oil ◽  
Pressure Variation ◽  
Material Parameters ◽  
Line Contacts ◽  
Finite Line ◽  
Moderate Load ◽  
Infinite Line ◽  
Cylindrical Roller ◽  
Theoretical Results

In this paper, a numerical solution to the elastohydrodynamic lubrication (EHL) problem is presented for a cylindrical roller with axially profiled ends, rolling over a flat plane. Convergence was obtained for moderate load and material parameters (glass, steel, and a mineral oil). Isobars, contours, and section graphs, show pressure variation and film shape. Predictions of film thickness compare favorably with experiments which use the optical interference method, as well as with other theoretical results for an infinite line contact, or an ellipse having a long slender aspect ratio. The maximum EHL pressure occurs near the start of the profiling and can exceed pressure concentrations there predicted by elastostatic theory.

Influence of Different Viscosity Lubricant to Finite Line Contacts on Elastohydrodynamic Lubrication (EHL) under Oscillating

2012 ◽  
Vol 538-541 ◽  
pp. 1939-1944
Author(s):  
Yan Fei Wang ◽  
Tong Shu Hua ◽  
Hao Yang Sun
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Oil Film ◽  
Entrainment Velocity ◽  
Finite Line Contact ◽  
Line Contacts ◽  
Finite Line ◽  
Contact Roller ◽  
Two Parameters ◽  
Experimental Rig

To make further researches into the elastohydrodynamic lubrication properties of a finite line contact roller, oscillating experiments were carried out on made overload experimental rig for oil film measurement using optical interference technique. Film thickness and shape were measured in two kinds of viscosity polyisobutylene. This study indicates that both lubricant viscosity and roller entrainment velocity play an important role on EHL of finite line contacts. On motion, the more increase in viscosity or speed, the thicker the oil film thickness, simultaneity edge effect is distinctly intensified and film thickness increases less on roller end, difference of the film thickness is increased between roller end and the central. Above two parameters are significant for logarithmic profile roller in crowning design.

Elastohydrodynamic Lubrication Analysis of Finite Line Contact Problem With Consideration of Two Free End Surfaces

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Haibo Zhang ◽  
Wenzhong Wang ◽  
Shengguang Zhang ◽  
Ziqiang Zhao
Keyword(s):  
Contact Problem ◽  
Finite Length ◽  
Elastohydrodynamic Lubrication ◽  
Line Contact ◽  
Free Boundaries ◽  
Finite Line Contact ◽  
Line Contacts ◽  
Speed Up ◽  
Finite Line ◽  
Overlapping Method

Elastohydrodynamic lubrication (EHL) analysis in finite line contacts is usually modeled by a finite-length roller contacting with a half-space, which ignores effect of the two free boundaries existing in many applications such as gears or roller bearings. This paper presents a semi-analytical method, involving the overlapping method and matrix formation, for EHL analysis in the finite line contact problem to consider the effect of two free end surfaces. Three half-spaces with mirrored loads to be solved are overlapped to cancel out the stresses at expected surfaces, and three matrices can be obtained and reused for the same finite-length space. The isothermal Reynolds equation is solved to obtain the pressure distribution and the fast Fourier transform (FFT) is used to speed up the elastic deformation and stress related calculation. Different line contact situations, including straight rollers, tapered rollers, and Lundberg profile rollers, are discussed to explore the effect of free end surfaces.

Thermal Non-Newtonian Elastohydrodynamic Lubrication of Rolling Line Contacts

1991 ◽  
Vol 113 (3) ◽  
pp. 481-491 ◽  
Author(s):  
H. Salehizadeh ◽  
N. Saka
Keyword(s):  
Film Thickness ◽  
Contact Region ◽  
Elastohydrodynamic Lubrication ◽  
Pressure Profile ◽  
Shear Stresses ◽  
Hertz Contact ◽  
Minimum Film Thickness ◽  
Line Contacts ◽  
Pressure Spike ◽  
Heavy Loads

The two-dimensional thermal elastohydrodynamic equations were numerically solved for a Ree-Eyring type lubricant under pure rolling conditions. Profiles of lubricant pressure, film thickness, and temperature were obtained for medium to heavy loads and moderate to high rolling speeds. The pressure results generally show a small secondary peak near the outlet, but at the highest load considered no pressure spike is obtained and the pressure profile is almost Hertzian. The film thickness results show an increase in minimum film thickness with increasing rolling speeds, but at a lesser rate than those predicted for a Newtonian fluid under isothermal conditions. It is found that unless the lubricant becomes non-Newtonian in the inlet region, the reduction in minimum film thickness at high rolling speeds is completely due to thermal effect. The lubricant temperature profile and the amount of heat generated and dissipated in the contact region were also calculated. The lubricant temperature reaches a maximum just before the entrance to the Hertz contact region. Both shear and compression heating are found to be important in raising the lubricant temperature in the inlet. As the lubricant enters the Hertz contact zone, the temperature first drops rapidly, because of the rapid heat conduction to the rollers, and then remains almost constant for most of the Hertz contact. Near the exit where the pressure gradients are large, the lubricant temperature drops rapidly below the ambient because of lubricant expansion. The lubricant then heats up rapidly before leaving the contact area as a result of heat generated by shear stresses.

New equations for enhanced film thickness in line contacts under pressurized ambient conditions

2016 ◽  
Vol 231 (5) ◽  
pp. 616-622 ◽  
Author(s):  
Niraj Kumar ◽  
Punit Kumar
Keyword(s):  
Film Thickness ◽  
Ambient Pressure ◽  
Elastohydrodynamic Lubrication ◽  
Viscosity Coefficient ◽  
Ambient Conditions ◽  
Alternative Approach ◽  
Film Forming ◽  
Highly Sensitive ◽  
Minimum Film Thickness ◽  
Line Contacts

An elastohydrodynamic lubrication model is proposed for line contacts under pressurized ambient conditions often encountered in hydraulic pumps, submarine machinery and many other submerged systems. It has been demonstrated that the film forming behavior under such conditions is essentially different from that in conventional elastohydrodynamic lubrication contacts. The numerical simulation results are regressed to develop new central and minimum film thickness equations for Newtonian fluids as functions of ambient pressure, speed, load, and material parameters. An alternative approach is also discussed which involves the use of existing film thickness formulas with ambient viscosity and pressure–viscosity coefficient pertaining to the desired pressure range. A film thickness enhancement of more than 100% over conventional elastohydrodynamic lubrication case is observed. This enhancement is shown to be highly sensitive to the pressure–viscosity coefficient. Besides, the effect of shear-thinning behavior is also investigated and it is found to lower the film thickness enhancement, especially at high ambient pressures.

Influence of Lubricant Pressure Response on Subsurface Stress in Elastohydrodynamically Lubricated Finite Line Contacts

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Tobias Hultqvist ◽  
Aleks Vrcek ◽  
Braham Prakash ◽  
Pär Marklund ◽  
Roland Larsson
Keyword(s):  
Low Cost ◽  
Elastohydrodynamic Lubrication ◽  
Pressure Response ◽  
Stress Concentrations ◽  
Oil Viscosity ◽  
Lubricated Contacts ◽  
Low Viscosity ◽  
Line Contacts ◽  
Finite Line ◽  
Subsurface Stress

In order to adapt to increasingly stringent CO2 regulations, the automotive industry must develop and evaluate low cost, low emission solutions in the powertrain technology. This often implies increased power density and the use of low viscosity oils, leading to additional challenges related to the durability of various machine elements. Therefore, an increased understanding of lubricated contacts becomes important where oil viscosity–pressure and compressibility–pressure behavior have been shown to influence the film thickness and pressure distribution in elastohydrodynamic lubrication (EHL) contacts, further influencing the durability. In this work, a finite line EHL contact is analyzed with focus on the oil compressibility–pressure and viscosity–pressure response, comparing two oils with relatively different behavior and its influence on subsurface stress concentrations in the contacting bodies. Results indicate that increased pressure gradients and pressure spikes, and therefore increased localized stress concentrations, can be expected for stiffer, less compressible oils, which under transient loading conditions not only affect the outlet but also the edges of the roller.

Influence of rough surface on damage evolution and fatigue life of M50-bearing steel containing a spherical inclusion

2019 ◽  
Vol 28 (10) ◽  
pp. 1580-1604 ◽  
Author(s):  
Jian Guan ◽  
Liqin Wang ◽  
Yunfeng Li ◽  
Chuanwei Zhang ◽  
Le Gu
Keyword(s):  
Fatigue Life ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Spherical Inclusion ◽  
Frictional Coefficient ◽  
Elastohydrodynamic Lubrication ◽  
Continuum Damage Mechanics ◽  
Element Model ◽  
Bearing Steel ◽  
Hydrodynamic Effect

In this paper, a continuum damage mechanics model is incorporated into the finite element model which contains a spherical inclusion to investigate damage evolution and predict fatigue life of M50-bearing steel. Quasi-dynamic method, isothermal elastohydrodynamic lubrication analysis and non-Gaussian surface simulating technique are combined to obtain the contact pressure. The damage evolution process of the micro-domain considering roughness texture is simulated and the fatigue life is predicted. The result shows that transverse texture can weaken the damage accumulation due to the strengthening of hydrodynamic effect. The effects of surface roughness parameters on fatigue life are also analyzed. It should be noted that transverse texture, small mean square root value and kurtosis, negative skewness are helpful for enhancing the fatigue life of bearing steel. Meanwhile, the increase of frictional coefficient and radius, negative position of local region will reduce the fatigue life.

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