A Numerical Analysis for TEHL of Eccentric-Tappet Pair Subjected to Transient Load

2003 ◽  
Vol 125 (4) ◽  
pp. 770-779 ◽  
Author(s):  
J. Wang ◽  
P. Yang
Keyword(s):  
Numerical Analysis ◽  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Surface Layers ◽  
Transient Load ◽  
Working Cycle ◽  
Pair Comparisons ◽  
Frictional Coefficients ◽  
Wedge Pressure

A full numerical analysis is carried out to simulate the thermal elastohydrodynamic lubrication (TEHL) of an eccentric-tappet pair. Comparisons between thermal and isothermal results are given to reveal the role of the thermal effect. Under various eccentricities, the influences of two surfaces moving in opposite directions on pressure and film thickness profiles are analyzed and explained by the mechanism of the temperature-viscosity wedge. Pressure and film thickness profiles, the temperature and velocity distributions at zero entraining velocity are discussed fully. Particular analyses are given on the entrapped immobile surface layers that influence the velocity distribution at zero entraining velocity. Furthermore, in a working cycle, variations of central and minimum film thicknesses and frictional coefficients, under different eccentricities, are discussed.

Influence of Surface Waviness on the Thermal Elastohydrodynamic Lubrication of an Eccentric-Tappet Pair

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
J. Wang ◽  
C. H. Venner ◽  
A. A. Lubrecht
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Surface Waviness ◽  
Film Pressure ◽  
Oil Film ◽  
Working Cycle ◽  
Temperature Oscillations ◽  
Minimum Film Thickness ◽  
Traction Coefficient ◽  
Oil Film Pressure

The effect of single-sided and double-sided harmonic surface waviness on the film thickness, pressure, and temperature oscillations in an elastohydrodynamically lubricated eccentric-tappet pair has been investigated in relation to the eccentricity and the waviness wavelength. The results show that, during one working cycle, the waviness causes significant fluctuations of the oil film, pressure, and temperature, as well as a reduction in minimum film thickness. Smaller wavelength causes more dramatic variations in oil film. The fluctuations of the pressure, film thickness, temperature, and traction coefficient caused by double-sided waviness are nearly the same compared with the single-sided waviness, but the variations are less intense.

Paper 9: The Role of Lubrication in Gear Design

1969 ◽  
Vol 184 (15) ◽  
pp. 72-78 ◽  
Author(s):  
D. Dowson
Keyword(s):  
Film Thickness ◽  
Research Work ◽  
Elastohydrodynamic Lubrication ◽  
Lubrication Mechanism ◽  
Engineering Material ◽  
Design Procedures ◽  
Gear Design ◽  
Surface Durability ◽  
Surface Distress

The paper gives an account of the way in which the results of fundamental studies of the lubrication mechanism in gears are now being incorporated in gear design procedures. The background to elastohydrodynamic lubrication is summarized and the importance of film thickness calculation is noted. The role of the lubricant in gear lubrication and its effect upon scuffing and pitting are considered. The importance of a film thickness ratio in determining the resistance to both forms of surface distress is emphasized. An improvement in surface durability is likely to lead to important increases in the ratings of many gear sets. The results of many years of research work on gear lubrication can now be embodied in design procedures for the optimization of resistance to scuffing and pitting, and the designer should be encouraged to treat the lubricant as an engineering material and a component in the gear system.

Numerical Analysis on Starved Elastohydrodynamic Lubrication Characteristics of Spiral Bevel Gears

2009 ◽  
Vol 16-19 ◽  
pp. 254-258 ◽  
Author(s):  
Yu Tao Yan ◽  
Zhi Li Sun ◽  
Qiang Yang ◽  
Yan Zhong Wang
Keyword(s):  
Numerical Analysis ◽  
Film Thickness ◽  
Gear Tooth ◽  
Elastohydrodynamic Lubrication ◽  
Analysis Model ◽  
Film Pressure ◽  
Spiral Bevel Gears ◽  
Bevel Gears ◽  
Spiral Bevel ◽  
Lubrication Characteristics

The spiral bevel gears of attack helicopter transmission systems are taken as an object in this paper. The numerical analysis model for starved elastohydrodynamic lubrication (SEHL) of spiral bevel gears is established on the basis of the analysis of load tooth contacts analysis and SEHL in elliptical contacts. The SEHL characteristics of spiral bevel gears are also analyzed. The results are as follows: during the course of a gear-tooth meshing cycle of the spiral bevel gear, the extremum of minimal film thickness and maximal film pressure occurs near midpoint of the path of contact, and leans to dedendum. The minimal value of the minimal film thickness is 0.39 um, and the maximal value of the maximal film pressure is 0.69 GPa. The value of minimal film thickness gradually increases with the increasing of meshing point velocity. When the velocity of meshing point exceeds 110 m/s, the increase became tardiness. As the load of meshing point increases, the value of minimal film thickness gently diminishes.

Influence of Micro-Morphology on Thermal Elatohydrodynamic Lubrication of Water-Lubricated Tenmat Bearing

2015 ◽  
Vol 743 ◽  
pp. 85-90 ◽  
Author(s):  
Ning Dong ◽  
You Qiang Wang ◽  
Qian Liu ◽  
Xing Bao Huang
Keyword(s):  
Numerical Analysis ◽  
Film Thickness ◽  
Partial Pressure ◽  
Reynolds Equation ◽  
Elastohydrodynamic Lubrication ◽  
Single Peak ◽  
Sine Function ◽  
Lubricating Film ◽  
Pressure Peak ◽  
Micro Morphology

The elastohydrodynamic lubrication numerical analysis of water-lubricated tenmat bearing with single sine-type peak, single V-type valley and single rectangular-type valley was carried out by using the Reynolds equation. The results show that, for the bearing with single peak, the partial pressure peak appears and the corresponding film thickness increases rapidly and then decreases; With the increase of the amplitude of the sine function, the partial pressure of the lubricating film is also increased, the partial film thickness is decreased, as the wavelength increases, the pressure and the film thickness of the convex portion widened, the peak remains substantially unchanged. For the bearing with single V-type valley and single rectangular-type valley, the partial pressure are decreased, the partial film thickness are increased; with the amplitude of the roughness function increases, the partial pressure are decreased, on the contrary ,the partial film thickness are increased; with the wavelength increases, the pressure and the film thickness of the convex portion widened.

Effect of Surface Roughness and Lubricant on Scuffing Initiation

2012 ◽  
Author(s):  
Jiman Han ◽  
Qian Zou
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Contact Area ◽  
Thickness Distribution ◽  
Research Work ◽  
Elastohydrodynamic Lubrication ◽  
Area Ratio ◽  
Contact Area Ratio ◽  
Effect Of Surface

Scuffing failure generally occurs at oil film breakdown and large amount of metal-to-metal interaction between the contacting surfaces, where the role of surface roughness and lubricant becomes prominent. In order to evaluate the effect of surface roughness and lubricant on scuffing, scuffing simulation was carried out using contact mechanics and plasto-elastohydrodynamic lubrication model (MixedPEHL) by taking into account the plastic deformation in the contact area. The evolution of pressure, film thickness, contact area ratio, and subsurface effective plastic strain (EPS) was performed with three types of surface roughness and two different lubricants. Comparisons of pressure distribution, film thickness distribution, film thickness to surface roughness ratio (λ ratio), and contact area ratio were described to investigate the effect of surface roughness and lubricants on scuffing behavior. A better understanding on the effect of surface roughness and lubricant on scuffing processes was obtained through the research work.

Rough Air-Soft Elastohydrodynamic Lubrication

2013 ◽  
Vol 420 ◽  
pp. 30-35
Author(s):  
Khanittha Wongseedakaew ◽  
Jesda Panichakorn
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Modulus Of Elasticity ◽  
Contact Region ◽  
Elastohydrodynamic Lubrication ◽  
Multilevel Methods ◽  
Inlet Temperature ◽  
Film Pressure ◽  
Air Inlet ◽  
Air Film

This paper presents the effects of rough surface air-soft elastohydrodynamic lubrication (EHL) of rollers for soft material under the effect of air molecular slip. The time independent modified Reynolds equation and elasticity equation were solved numerically using finite different method, Newton-Raphson method and multigrid multilevel methods were used to obtain the film pressure profiles and film thickness in the contact region. The effects of amplitude of surface roughness, modulus of elasticity and air inlet temperature are examined. The simulation results showed surface roughness has effect on film thickness but it little effect to air film pressure. When the amplitude of surface roughness and modulus of elasticity increased, the air film thickness decreased but air film pressure increased. However, the air inlet temperature increased when the air film thickness increased.

Thermal Elastohydrodynamic Lubrication of an Optimized Cam–Tappet Pair in Smooth Contact

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
W. Wu ◽  
J. Wang ◽  
C. H. Venner
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Temperature Profiles ◽  
Cam Mechanism ◽  
Basic Segment ◽  
Order Polynomial ◽  
Isothermal Analysis ◽  
Base Circle ◽  
Smooth Contact ◽  
Oil Characteristics

A high-order polynomial gas distribution cam mechanism is investigated theoretically from the viewpoint of thermal elastohydrodynamic lubrication (EHL). First, a cam with a larger base circle radius is employed, which results in slide–roll ratio 2.0 < S < 9.0 when the two surfaces move oppositely. The pressure, film thickness, and temperature profiles at a number of angular positions of the cam are presented, together with the isothermal results. The comparison between thermal and isothermal oil characteristics is also shown. It is revealed that the isothermal analysis partly overestimates the actual film thickness and it also misses some essential local phenomena. Second, a cam with a smaller base circle radius is studied, which leads to drastic variations in the slide–roll ratio which encounters four times’ occurrences of infinity in one working period. The pressure, film thickness, and temperature profiles at some angular cam positions together with the oil characteristics are given, showing much dramatic variations. A very small film thickness is observed at the contact of the tappet with the start of the cam basic segment, which suggests a possible risk of direct contact of both surfaces.

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.

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