Formation Mechanism of Steady Multi-Dimples in Thermal EHL Point Contacts

2003 ◽  
Vol 125 (2) ◽  
pp. 241-251 ◽  
Author(s):  
M. Kaneta ◽  
P. Yang
Keyword(s):  
Steady State ◽  
Flow Model ◽  
Numerical Solutions ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
Newtonian Flow ◽  
Pure Rolling ◽  
Pressure Spike ◽  
Thermal Ehl

With optical interferometry technique, an interesting multi-dimple phenomenon has been discovered under pure-sliding conditions in the point contact between a glass disk and a 3-inch diameter steel ball. At low sliding speeds, two or three stable dimples can be generated in the contact, but at higher sliding speeds, such multi-dimples become unstable. At even higher sliding speeds, however, dimples become stable again, but two dimples become single dimple, or three become two. Numerical solutions of the steady-state thermal elastohydrodynamic lubrication (EHL) theory based on the Newtonian flow model can simulate the stable multi-dimples very well. By changing the slide-roll conditions from pure-rolling to pure-sliding, the theoretical analysis shows clearly that the stable multi-dimples are produced by the thermal effect through the familiar EHL pressure spike.

Non-Newtonian Thermal Analyses of Point EHL Contacts Using the Eyring Model

2005 ◽  
Vol 127 (1) ◽  
pp. 70-81 ◽  
Author(s):  
Xiaoling Liu ◽  
Ming Jiang ◽  
Peiran Yang ◽  
Motohiro Kaneta
Keyword(s):  
Effective Viscosity ◽  
Numerical Solutions ◽  
Thermal Analyses ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Contact Problems ◽  
Point Contacts ◽  
Eyring Model ◽  
Thermal Ehl

A non-Newtonian numerical solution system for the thermal elastohydrodynamic lubrication (EHL) problems in point contacts has been developed. The Eyring rheology model has been used to describe the non-Newtonian flow of the lubricant. An effective viscosity has been defined for the Eyring fluid. The Newtonian solver can be applied easily to the non-Newtonian problems when the viscosity of the Newtonian fluid is replaced by the effective viscosity. A novel technique for the determination of the effective viscosity is proposed. Numerical solutions for the conventional point contact and normally crossing cylinders contact problems are presented and the effects of the entraining velocity, the load, the slide-roll ratio, and the characteristic shear stress of the Eyring fluid on the lubricating performance are discussed. The results indicate that the non-Newtonian thermal EHL theory predicts more realistic film temperatures and traction coefficients.

scholarly journals Transient analysis of isothermal elastohydrodynamic circular point contacts

2001 ◽  
Vol 215 (10) ◽  
pp. 1159-1172 ◽  
Author(s):  
D Jalali Vahid ◽  
H Rahnejat ◽  
Z M Jin ◽  
D Downson
Keyword(s):  
Transient Analysis ◽  
Solution Method ◽  
Numerical Solutions ◽  
Flat Glass ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
Good Qualitative Agreement ◽  
Circular Point ◽  
Good Agreement

In this paper a solution method is presented for the transient isothermal elastohydrodynamic lubrication of point contact conjunctions, based upon the Newton-Raphson scheme and low iteration relaxation. The numerical results are compared with the numerical and experimental observations of others for the circular point contact of a ball against a flat glass disc under oscillating conditions. Good agreement has been found with other numerical solutions. The comparison with the experimental results shows good qualitative agreement.

Quantitative Comparisons Between Measured and Solved EHL Dimples in Point Contacts

2002 ◽  
Vol 125 (1) ◽  
pp. 210-214 ◽  
Author(s):  
P. Yang ◽  
M. Kaneta and ◽  
S. Masuda
Keyword(s):  
Flow Model ◽  
Optical Interferometry ◽  
Numerical Results ◽  
Experimental Results ◽  
Point Contacts ◽  
Newtonian Flow ◽  
Glass Disk ◽  
Traction Coefficient ◽  
Thermal Ehl ◽  
The Relationship

Using a mineral bright stock oil as lubricant, the dimple phenomena in the circular EHL contacts composed of a glass disk and a steel ball were investigated experimentally with the optical interferometry technique. The traction coefficient was also measured. The experimental results were compared quantitatively with the numerical results of the corresponding thermal Newtonian EHL solutions. The comparisons show that the Newtonian thermal EHL theory can explain very well the relationship between the dimple phenomena and the slide-roll ratio, but cannot predict accurately the depth of the dimple and the magnitude of the traction coefficient. It has also been found that the Newtonian flow model overestimates the effect of the temperature-viscosity wedge and consequently, a non-Newtonian flow model may be necessary for a better understanding of the EHL dimple phenomena.

Non-Newtonian Elastohydrodynamic Lubrication of Point Contact

1991 ◽  
Vol 113 (4) ◽  
pp. 703-711 ◽  
Author(s):  
Kyung Hoon Kim ◽  
Farshid Sadeghi
Keyword(s):  
Film Thickness ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Two Dimensional ◽  
Point Contacts ◽  
Dimensionless Velocity ◽  
Simultaneous System ◽  
Elasticity Equations ◽  
Minimum Film Thickness ◽  
Pressure Spike

A numerical solution to the problem of isothermal non-Newtonian elastohydrodynamic lubrication of rolling/sliding point contacts has been obtained. The multigrid technique is used to solve the simultaneous system of two-dimensional modified Reynolds and elasticity equations. The effects of various loads, speeds, and slide to roll ratios on the pressure distribution, film thickness, and friction force have been investigated. Results for the dimensionless load W = 4.6 × 10−6 and 1.1 × 10−6, and the dimensionless velocity U = 3 × 10−10 and 3 × 10−11 are presented. The results indicate that slide to roll ratio has negligible effect on the minimum film thickness, however, it significantly reduces the pressure spike.

scholarly journals A thermal resistances-based approach for thermal-elastohydrodynamic calculations in point contacts

2017 ◽  
Vol 232 (11) ◽  
pp. 2088-2102 ◽  
Author(s):  
Eduardo de la Guerra Ochoa ◽  
Javier Echávarri Otero ◽  
Enrique Chacón Tanarro ◽  
Benito del Río López
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Thermal Effects ◽  
Good Accuracy ◽  
Computational Cost ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
New Approach ◽  
Ball On Disc

This article presents a thermal resistances-based approach for solving the thermal-elastohydrodynamic lubrication problem in point contact, taking the lubricant rheology into account. The friction coefficient in the contact is estimated, along with the distribution of both film thickness and temperature. A commercial tribometer is used in order to measure the friction coefficient at a ball-on-disc point contact lubricated with a polyalphaolefin base. These data and other experimental results available in the bibliography are compared to those obtained by using the proposed methodology, and thermal effects are analysed. The new approach shows good accuracy for predicting the friction coefficient and requires less computational cost than full thermal-elastohydrodynamic simulations.

Thermal Elastohydrodynamic Lubrication Analysis for Point Contact Transmission

2009 ◽  
Author(s):  
Hai-zhou Huang ◽  
Xi-chuan Niu ◽  
Xiao-yang Yuan
Keyword(s):  
Film Thickness ◽  
Numerical Solutions ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Surface Velocity ◽  
Squeeze Film ◽  
Elastic Displacement ◽  
Circular Arc ◽  
Tooth Width ◽  
Contact Transmission

To investigate the thermal EHL (elastohydrodynamic lubrication) in point contact transmission, a model considering the two-dimensional surface velocity of tooth face and the running-in is proposed. The numerical solutions for pressure, temperature and film thickness distribution in the contact zone are obtained by solving equations including the Reynolds, Energy and the elastic displacement with variable dimension meshing method. The model was used to study the point contact transmission of the circular arc gear in a windlass. The main results show that it is pure rolling along the direction of tooth width, and the rolling speed plays a leading role in improving the lubricating performance and transmission efficiency of circular arc gear. The squeeze film effect makes the pressure peak tend to be gentle and the film thickness increase slightly.

Theoretical and experimental studies of the oil film in lubricated point contact

1966 ◽  
Vol 291 (1427) ◽  
pp. 520-536 ◽  
Keyword(s):  
Surface Layer ◽  
Film Thickness ◽  
Strong Evidence ◽  
Experimental Studies ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Experimental Results ◽  
Point Contacts ◽  
Previous Theory ◽  
Oil Film

A technique using Newton’s rings for mapping the oil film of lubricated point contacts is described. A theoretical value for the film thickness of such contacts in elastohydrodynamic lubrication is derived. The experimental results give the exit constriction predicted by previous theory but never shown in detail. The comparison of theoretical and experimental oil film thicknesses, which is satisfactorily accurate, gives strong evidence for a viscous surface layer some 1000Å thick. This film agrees with the known ‘lubricating power’ of the various oils tested.

Size Effect on the Behavior of Thermal Elastohydrodynamic Lubrication of Roller Pairs

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
Xiaoling Liu ◽  
Jinlei Cui ◽  
Peiran Yang
Keyword(s):  
Size Effect ◽  
Newtonian Fluid ◽  
Effective Viscosity ◽  
Numerical Solutions ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Load Parameter ◽  
Performance Results ◽  
Thermal Ehl ◽  
Strong Size Effect

In order to investigate the size effect on elastohydrodynamic lubrication (EHL) of roller pairs, complete numerical solutions for both the Newtonian fluid and the Eyring fluid thermal EHL problems of roller pairs under steady state conditions have been achieved. It can be seen that there is no size effect on the isothermal EHL performance; however, there is a very strong size effect on the thermal EHL performance. Results show that the term of shearing heat is the most important factor for the film temperature when the size of a contact changes. Comparison between the Newtonian solution and the Eyring solution has been made under some operating conditions. It is interesting to see that the effective viscosity of the Eyring fluid is nearly the same as that of the Newtonian fluid when the size of a contact is large enough. The non-Newtonian effect, therefore, can be ignored when the size of a contact is very large. It is equally interesting to see that the thermal effect can be ignored when the size of a contact is very small. In addition, the influence of the velocity parameter, the load parameter, and the slide-roll ratio on the lubricating performance for various sizes of contacts has been investigated.

Solution of the Non-Newtonian Elastohydrodynamic Problem for Circular Contacts Based on a Flow Continuity Method

1996 ◽  
Vol 210 (4) ◽  
pp. 247-258 ◽  
Author(s):  
C A Holt ◽  
H P Evans ◽  
R W Snidle
Keyword(s):  
Film Thickness ◽  
Numerical Solution ◽  
Control Volume ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Theoretical Formulation ◽  
New Approach ◽  
Limiting Shear Stress ◽  
Pure Rolling ◽  
Stress Behaviour

The paper describes a numerical solution method for the point contact elastohydrodynamic lubrication (EHL) problem under non-Newtonian, isothermal conditions. The theoretical formulation of the non-Newtonian effect is general and may be applied to both shear thinning and limiting shear stress behaviour. The particular rheological model investigated in this work is the Eyring ‘sinh law’ relation. The numerical solution of the lubrication equations is based upon a control volume approach rather than the more usual methods that utilize a modified Reynolds equation. This new approach ensures that flow continuity is satisfied at the discretization level. Results are presented to show the effect of non-Newtonian behaviour on film thickness and pressure distribution in circular EHL contacts operating over a range of slide-roll ratios from 0 (pure rolling) to 1.5. Under conditions of pure rolling or low sliding there is found to be little effect of non-Newtonian behaviour, but at the highest degree of sliding the film thickness over the central, flattened area of the contact is reduced by up to 10 per cent at the highest rolling speed of 0.75 m/s.

Analysis of Thermal Effect on Elastohydrodynamic Lubrication in Angular Contact Ball Bearing

2015 ◽  
Vol 741 ◽  
pp. 443-448
Author(s):  
Bao Ming Wang ◽  
Xia Lun Yun ◽  
Xing Yao Liao ◽  
Xue Song Mei
Keyword(s):  
Temperature Rise ◽  
High Speed ◽  
Ball Bearing ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Oil Viscosity ◽  
Angular Contact Ball Bearing ◽  
Scanning Method ◽  
Lubrication Performance ◽  
Thermal Ehl

Based on the theory of point contact thermal elastohydrodynamic lubrication (EHL),the mathematical models for the thermal EHL of high-speed angular contact ball bearing are established. Multi-grid method and multigrid integration method are respectively used to calculate out the film pressure and film thickness respectively,and the column-by-column scanning method is used to calculate temperature rise of isothermal EHL and thermal EHL. The calculation results show that, under the pure rolling condition, temperature rise of oil film temperature is mainly caused by the compression work and shear heat at inlet and the heat in contact zone mainly comes from the inlet and the heat conduction around; the temperature rise results in oil viscosity lower and the lubricating film thinner ,in this way it reduces the lubrication performance in contact pair.

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