Elastohydrodynamic Behavior of Rolling Elliptical Contacts: Part II: Oil Film Thickness and Contact Profile

1985 ◽  
Vol 107 (3) ◽  
pp. 352-357 ◽  
Author(s):  
M. O. A. Mokhtar ◽  
A. A. Abdel-Ghany
Keyword(s):  
Film Thickness ◽  
Contact Zone ◽  
Circular Disk ◽  
Rolling Contact ◽  
Thickness Variation ◽  
Relative Speed ◽  
Oil Film ◽  
Sliding Motion ◽  
Pure Rolling ◽  
Experimental Findings

A spherically crowned circular disk in contact with a mating plain cylindrical one has been used in a two disk machine to conduct elastohydrodynamic (EHD) investigations with the contact zone describing elliptical shape. The oil film thickness variation has been accurately measured and herein presented under several contact situations with disks running with either pure rolling or combined rolling and sliding motion. Results confirmed that the introduction of a percentage slip over a rolling contact by either changing disks relative speed or skewing disks axes relative to each other, would affect the resultant oil film thickness by reducing it. However, the contact profile retained its shape with a mean oil film passage followed by a reduction at the trailing exit end. Compared with previous EHD theoretical and experimental findings, the present results come in line with previous predictions and confirm the importance of adopting thermal solutions in solving EHD situations.

Thermal EHL Analyses of Point Contacts With Surface Roughness

2005 ◽  
Author(s):  
J. Wang ◽  
P. Yang ◽  
M. Kaneta
Keyword(s):  
Surface Roughness ◽  
High Temperature ◽  
Film Thickness ◽  
Temperature Rise ◽  
Point Contacts ◽  
Oil Film ◽  
Sliding Motion ◽  
Pure Rolling ◽  
Thermal Ehl ◽  
High Temperature Rise

The Newtonian thermal EHL analyses of point contacts with two-sided surface roughness have been performed under pure rolling, sliding/rolling and simple sliding conditions. Thermal results are compared with isothermal ones. It has been found that the sliding motion produces high temperature rise and reduces the film thickness greatly. The influence of amplitude and wavelength of the surface roughness on variation of tribo-characteristics of oil film is also discussed.

A thermal EHL investigation for size effect of finite line contact on bush-pin hinge pairs in industrial chains

2020 ◽  
Vol 72 (5) ◽  
pp. 695-701
Author(s):  
Mingyu Zhang ◽  
Jing Wang ◽  
Peiran Yang ◽  
Zhaohua Shang ◽  
Yi Liu ◽  
...  
Keyword(s):  
Film Thickness ◽  
Peer Review ◽  
Contact Zone ◽  
Line Contact ◽  
Equivalent Radius ◽  
Content Type ◽  
Oil Film ◽  
Finite Line Contact ◽  
Finite Line ◽  
Thermal Ehl

Purpose This paper aims to study the influence of the dimension change of bush-pin on the pressure, oil film thickness, temperature rise and traction coefficient in contact zone by using a thermal elastohydrodynamic lubrication (EHL) model for finite line contact. Concretely, the effects of the equivalent curvature radius of the bush and the pin, and the length of the bush are investigated. Design/methodology/approach In this paper, the contact between the bush and pin is simplified as finite line contact. The lubrication state is studied by numerical simulation using steady-state line contact thermal EHL. A constitutive equation Ree–Eyring fluid is used in the calculations. Findings It is found that by selecting an optimal equivalent radius of curvature and prolonging the bush length can improve the lubrication state effectively. Originality/value Under specific working conditions, there exists an optimal equivalent radius to maximize the minimum oil film thickness in the contact zone. The increase of generatrix length will weaken the stress concentration effect in the rounded corner area at both ends of the bush, which can improve the wear resistance of chain. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-10-2019-0448.

Application of dynamic mesh technology in the oil film flow simulation for hydrostatic bearing

2019 ◽  
Vol 71 (1) ◽  
pp. 146-153
Author(s):  
Yanqin Zhang ◽  
Zhiquan Zhang ◽  
Xiangbin Kong ◽  
Rui Li ◽  
Hui Jiang
Keyword(s):  
Film Thickness ◽  
Flow Velocity ◽  
Manufacturing Industry ◽  
Dynamic Mesh ◽  
Lubricating Oil ◽  
Thickness Variation ◽  
Content Type ◽  
Oil Film ◽  
Rotating Speed ◽  
Hydrostatic Bearing

Purpose The purpose of this paper was to obtain the lubrication characteristics of heavy hydrostatic bearing in heavy equipment manufacturing industry through theoretical analysis and numerical simulation. Design/methodology/approach This paper discusses the influence of oil film thickness variation on velocity field, outlet-L and outlet-R flow velocity under the hydrostatic bearing running in no-load 0 N, load 400 KN, full load 1,500 KN and rotating speeds of 10 r/min, 20 r/min, 30 r/min, 40 r/min, 50 r/min and 60 r/min, by using dynamic mesh technology and FLUENT software. Findings When the working table rotates clockwise, in the change process of oil film thickness, the fluid flow pattern of the lubricating oil at the edge of the sealing oil is the rule of laminar flow, and the oil cavity has a vortex. The outlet-R flow velocity becomes higher and higher by increasing the bearing load and working table speed, and the flow velocity increases with the decrease in oil film thickness; the outlet-L flow velocity increases with the decrease in oil film thickness under low rotating speed (less than 10 r/min) condition and decreases with the decrease of oil film thickness under high rotating speed (more than 60 r/min) condition. Originality/value The influence of the oil film thickness on the flow state distribution of the oil film was analyzed under different working conditions, and the influence rules of oil film thickness on the flow velocity of hydrostatic bearing oil pad was obtained by using dynamic mesh technology.

Optical Measurement of EHL Film under Oscillating Needle Roller Contacts

2015 ◽  
Vol 642 ◽  
pp. 270-274
Author(s):  
Xue Jin Shen ◽  
Zhen Min Song ◽  
Xiao Yang Chen
Keyword(s):  
Film Thickness ◽  
Working Conditions ◽  
Applied Load ◽  
Optical Measurement ◽  
Rotation Velocity ◽  
Optical Interferometry ◽  
Oil Film ◽  
Pure Rolling ◽  
Rectangular Glass

In this paper, the EHL oil film thickness and shape between a needle roller and a flat rectangular glass in pure rolling oscillated working conditions had been measured based on optical interferometry. The EHL behavior affected by the applied load, oscillating frequency was investigated. The typical film shape varies of interference pictures on the maximum needle roller rotation velocity was obtained and compared each other. It is found the side constrictions are always the most severe and they are strongly speeds and loads dependence.

Effect of Longitudinal Mini-Grooves on Flow Stability and Wave Characteristics of Falling Liquid Films

2007 ◽  
Author(s):  
Klaus Helbig ◽  
Ralph Nasarek ◽  
Tatiana Gambaryan-Roisman ◽  
Peter Stephan
Keyword(s):  
Wave Propagation ◽  
Film Thickness ◽  
Linear Stability ◽  
Propagation Speed ◽  
Wave Theory ◽  
Liquid Films ◽  
Transport Processes ◽  
Thickness Variation ◽  
Experimental Findings ◽  
Falling Liquid Films

Falling liquid films are used in many industrial apparatuses. In many cases the film flow along a wall with topography is considered advantageous for intensification of the transport processes. We use the shadow method and the chromatic white light sensor (CHR) method to study the wavy structure of falling films on flat walls and on walls with longitudinal grooves. We show that the wavy pattern substantially changes on walls with topography. The wave frequency, the wave propagation velocity and the area of the liquid-gas interface decrease on grooved walls. The linear stability of the film has been analyzed using the long-wave theory, which relies on the assumption that the average film thickness is much smaller than the scale of the film thickness variation. The linear stability analysis predicts that the disturbance growth rate, the frequency of the fastest growing disturbance mode and the wave propagation speed decrease on a tube with longitudinal mini-grooves in comparison with a smooth tube. These results agree well with the experimental findings.

Fatigue Life Investigation of Solid and Hollow Rollers in Pure Rolling Contact

2005 ◽  
Author(s):  
W. Abu Jadayil ◽  
D. Flugrad ◽  
A. Qamhiyah
Keyword(s):  
Fatigue Life ◽  
Contact Zone ◽  
Peak Stress ◽  
Rolling Contact ◽  
Solid Cylinder ◽  
Rolling Bearings ◽  
Pure Rolling ◽  
Life Model ◽  
Finite Element Package ◽  
Hollow Cylinders

Two solid and hollow cylindrical rollers in pure rolling contact have been modeled. The two rollers are subjected to a combined normal and tangential loading. The Stress distribution in the contact zone has been determined using a finite element package called ABAQUS. Then fatigue life model for rolling bearings developed by Ioannides and Harris has been used to study the relative fatigue life of the hollow rollers compared to solid rollers. Different hollowness percentages have been investigated; 20%, 40%, 60% and 80%. Two cases were studied- when both rollers are hollow and when only one of them is hollow while the other one is solid. It has been found that making the rollers hollow will result in redistribution of stresses in the contact zone. That decreased the peak stress under the surface when compared to the solid cylinder. Hollow cylinders have more flexibility when subjected to normal and tangential loading. And so, the stresses are redistributed so that the fatigue life is improved. The best fatigue life improvements have been found when both cylinders have almost 60% hollowness.

Lubrication Phenomena in Spur Gears: Capacity, Film Thickness Variation, and Efficiency

1965 ◽  
Vol 87 (3) ◽  
pp. 655-663 ◽  
Author(s):  
R. Wayne Adkins ◽  
E. I. Radzimovsky
Keyword(s):  
Shear Stress ◽  
Film Thickness ◽  
Pressure Distribution ◽  
Power Loss ◽  
Hydrodynamic Lubrication ◽  
Thickness Variation ◽  
Spur Gears ◽  
Oil Film ◽  
Lubrication Conditions ◽  
Lubricant Viscosity

In this paper the oil film separating the mating surfaces of involute spur gears operating under hydrodynamic lubrication conditions is analyzed. This analysis surpasses previous analyses in as much as the actual motion of the involute profiles (rolling, sliding, and squeezing motion) and the total number of teeth engaged at any one time are considered. Expressions are derived for the pressure distribution, shear stress, and power loss in the oil film at any phase of tooth engagement. A method is developed by which these expressions can be applied to determine the film thickness at any instant and the power loss for a given load, speed, and lubricant viscosity.

Numerical Model of Journal Bearing Lubrication Considering a Bending Stiffness Effect

2013 ◽  
Vol 284-287 ◽  
pp. 854-860
Author(s):  
Juh Wan Choi ◽  
Seong Su Kim ◽  
Sung Soo Rhim ◽  
Jin Hwan Choi
Keyword(s):  
Numerical Model ◽  
Film Thickness ◽  
Journal Bearing ◽  
Elastohydrodynamic Lubrication ◽  
Bending Stiffness ◽  
Thickness Variation ◽  
Lubrication System ◽  
Film Pressure ◽  
Oil Film ◽  
Oil Film Pressure

An analysis for operating characteristics of journal bearing lubrication system is performed based on the numerical model. Dynamic bearing lubrication characteristics such as oil film pressure and thickness distribution can be analyzed through a numerical model with an integration of elastohydrodynamics and multi-flexible-body dynamics (MFBD). In particular, the oil film thickness variation by elastic deformation is considered in the elastohydrodynamic analysis by applying the bending stiffness effect of journal. And the oil film thickness variation by the bending stiffness effect is applied to the fluid governing equations to calculate the oil film pressure in the elastohydrodynamic lubrication region. A series of process proposed in this study is available for the analysis of realistic elastohydrodynamic lubrication phenomenon. Also, a numerical example for the journal bearing lubrication system is demonstrated and compared with the experimental results. The numerical results considering the bending stiffness effect show a good agreement with the experimental results.

Inlet Shear Heating in Elastohydrodynamic Lubrication

1973 ◽  
Vol 95 (4) ◽  
pp. 417-423 ◽  
Author(s):  
J. A. Greenwood ◽  
J. J. Kauzlarich
Keyword(s):  
Shear Rate ◽  
Theoretical Analysis ◽  
Film Thickness ◽  
Temperature Rise ◽  
Thermal Effects ◽  
Elastohydrodynamic Lubrication ◽  
Oil Film ◽  
Comparison With Experiment ◽  
Pure Rolling ◽  
Shear Heating

In EHL, the oil film thickness of rollers is controlled by the rate at which the oil is drawn into the conjunction of the disks by the moving surfaces of the rollers. The theory often assumes isothermal conditions in the inlet although it can be shown that the maximum shear rate often exceeds 106 sec−1, even in pure rolling. A theoretical analysis is presented for the oil temperature rise in the inlet of rollers, and the result is applied to predict the consequent film thickness. It is found that thermal effects on film thickness are only negligible at low rolling speeds. A comparison with experiment supports the conclusion that the thinning of the film thickness below that predicted by isothermal theory is substantially explained by inlet shear heating of the lubricant.

Elastohydrodynamic Lubrication of a Line Contact

1974 ◽  
Vol 188 (1) ◽  
pp. 221-238 ◽  
Author(s):  
D. G. Wymer ◽  
A. Cameron
Keyword(s):  
Film Thickness ◽  
Central Region ◽  
Glass Plate ◽  
Elastohydrodynamic Lubrication ◽  
Optical Interferometry ◽  
Optical Measurements ◽  
Line Contact ◽  
Electrical Measurements ◽  
Oil Film ◽  
Pure Rolling

In Part 1, optical interferometry is used to study an elastohydrodynamically lubricated line contact between a taper roller and a glass plate under pure rolling conditions. The results give detailed information on film profiles and show the effects of end blending, lubricant starvation, deep scratches and static oil entrapments. In Part 2, oil film thicknesses in an elastohydrodynamic line contact are measured using optical interferometry and compared with theory. Two empirical formulae are derived for film thickness in the central region and at the exit constriction. In addition to the optical measurements, electrical measurements (resistance and capacitance) are made simultaneously, enabling a direct comparison to be made.

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