Effect of three-dimensional surface crack on the elastohydrodynamic lubrication performance of ellipsoid contact

2018 ◽  
Vol 233 (6) ◽  
pp. 975-991 ◽  
Author(s):  
Fanming Meng ◽  
XueFang Cui ◽  
Cao Pu
Keyword(s):  
Crack Width ◽  
Rolling Direction ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Reduced Form ◽  
Contact Center ◽  
Transform Method ◽  
Film Pressure ◽  
Fluid Field ◽  
Lubrication Performance

The elastohydrodynamic lubrication model for the ellipsoid contact considering three-dimensional crack effect is established and solved with an under-relaxation algorithm. In doing so, the fluid field is divided into the two computation domains, in which the usual Reynolds equation and its reduced form are solved for the film pressure with the crack effect. Meanwhile, a fast Fourier transform method is adopted to accelerate the deformation calculation. Simulation model is verified. Numerical results show that the crack can cause jumps for the film pressure and film thickness. Increasing the crack length along the rolling direction and the depth at the crack's open end, and decreasing the crack tip inclined angle all result in an increment in the maximum film pressure. In addition, increasing the crack width can make the film pressure within the crack shift towards both ends of the crack width. The crack close to the contact center brings out a large film pressure.

Simulation of Plasto-Elastohydrodynamic Lubrication in a Rolling Contact

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Tao He ◽  
Dong Zhu ◽  
Jiaxu Wang
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Rolling Direction ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Surface Plastic Deformation ◽  
Rolling Contact ◽  
Surface Plastic ◽  
Contact Center ◽  
Elastic Plastic

Surface plastic deformation due to contact (lubricated or dry) widely exists in many mechanical components, as subsurface stress caused by high-pressure concentrated in the contact zone often exceeds the material yielding limit, and the plastic strain accumulates when the load is increased and/or repeatedly applied to the surface in a rolling contact. However, previous plasto-elastohydrodynamic lubrication (PEHL) studies were mainly for the preliminary case of having a rigid ball (or roller) rotating on a stationary elastic–plastic flat with a fixed contact center, for which the numerical simulation is relatively simple. This paper presents an efficient method for simulating PEHL in a rolling contact. The von Mises yield criteria are used for determining the plastic zone, and the total computation domain is discretized into a number of cuboidal elements underneath the contacting surface, each one is considered as a cuboid with uniform plastic strain inside. The residual stress and surface plastic deformation resulted from the plastic strain can be solved as a half-space eigenstrain–eigenstress problem. A combination of three-dimensional (3D) and two-dimensional (2D) discrete convolution and fast Fourier transform (DC-FFT) techniques is used for accelerating the computation. It is observed that if a rigid ball rolls on an elastic–plastic surface, the characteristics of PEHL lubricant film thickness and pressure distribution are different from those of PEHL in the preliminary cases previously investigated. It is also found that with the increase of rolling cycles, the increment of plastic strain accumulation gradually approaches a stable value or drops down to zero, determined by the applied load and the material hardening properties, eventually causing a groove along the rolling direction. Simulation results for different material hardening properties are also compared to reveal the effect of body materials on the PEHL behaviors.

Mixed Elastohydrodynamic Lubrication With Three-Dimensional Machined Roughness in Spiral Bevel and Hypoid Gears

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Wei Pu ◽  
Jiaxu Wang ◽  
Rongsong Yang ◽  
Dong Zhu
Keyword(s):  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Strength Prediction ◽  
Flash Temperature ◽  
Hypoid Gears ◽  
Lubrication Performance ◽  
Lubrication Condition ◽  
Spiral Bevel ◽  
Film Lubrication

Spiral bevel and hypoid gears are key components widely used for transmitting significant power in various types of vehicles and engineering machineries. In reality, these gear surfaces are quite rough with three-dimensional (3D) topography that may significantly influence the lubrication formation and breakdown as well as components failures. Previous spiral bevel and hypoid gears lubrication studies, however, were limited mostly to cases under the full-film lubrication condition with smooth surfaces. In the present study, a comprehensive analysis for gearing geometry, kinematics, mixed lubrication performance, and friction and interfacial flash temperature in spiral bevel and hypoid gears is developed based on a recently developed mixed elastohydrodynamic lubrication (EHL) model that is capable of handling practical cases with 3D machined roughness under severe operating conditions and considering the effect of arbitrary entrainment angle. Obtained results from sample cases show that the simulation model developed can be used as an engineering tool for spiral bevel and hypoid gears design optimization and strength prediction.

Modeling and Analysis of Mixed Lubrication in Automotive Valve Train

2014 ◽  
Author(s):  
Ning Ren ◽  
Frances E. Lockwood ◽  
Ilya Piraner ◽  
Amit Gabale
Keyword(s):  
Driving Forces ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Mixed Lubrication ◽  
Valve Train ◽  
Engine Oil ◽  
Modeling And Analysis ◽  
Low Viscosity ◽  
Lubrication Performance ◽  
Engine Components

Environmental regulation and high fuel cost are among the leading driving forces behind the demand of energy efficient vehicles. Together with new engine hardware technologies, engine oil is expected to significantly contribute to improving vehicle fuel economy. New fuel-efficient engine oils are often formulated with advanced additives and low viscosity base oils. Understanding the lubrication performance at key engine components such as the cam and follower in valve train systems becomes critically important to ensure engine durability with the new fuel-efficient low viscosity oils. A full numerical mixed lubrication analysis of the cam and roller follower pair is conducted using the three dimensional line contact mixed elastohydrodynamic lubrication (EHL) model. The results show significant effects of surface roughness, topography, slide-to-roll ratio, and viscosity grade on lubricant film, contact pressure, and subsurface stress.

Debris Denting Effects on Elastohydrodynamic Lubricated Contacts

1997 ◽  
Vol 119 (3) ◽  
pp. 579-587 ◽  
Author(s):  
Gang Xu ◽  
Farshid Sadeghi ◽  
J. David Cogdell
Keyword(s):  
Finite Element ◽  
Rolling Direction ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Element Model ◽  
Von Mises Stress ◽  
Internal Stresses ◽  
Element Analysis ◽  
Lubricated Contacts

A finite element model was developed to investigate the effects of a spherical debris on elastohydrodynamically lubricated rolling/sliding contacts. Three dimensional dent profiles were obtained using finite element method showing horseshoe shape material pile-up along the rolling direction. The dent profiles obtained from the finite element analysis (FEA) were compared with the experimental results. There is good qualitative agreement between FEA and experimental dent profiles. The FEA dent profiles were then used in a time dependent thermal elastohydrodynamic lubrication (EHL) point contact model to analyze the dent effects on the pressure, film thickness and temperature profiles. The presence of a dent in lubricated contacts generates high pressure spikes and increases the peak temperature. The internal stresses were calculated based on the pressure and traction data obtained from the EHL analysis. The results indicate that a dent created by a debris will cause the internal maximum Von Mises stress to occur near the surface, which contributes to surface initiated failures.

Effects of Texture Orientation on the Mixed Thermal Elastohydrodynamic Lubrication and Fatigue Life in Point Contacts

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Xiao-Liang Yan ◽  
Yu-Yan Zhang ◽  
Guo-Xin Xie ◽  
Xiao-Qiong Du ◽  
Fen Qin
Keyword(s):  
Fatigue Life ◽  
Load Capacity ◽  
Three Dimensional ◽  
Point Contact ◽  
Texture Feature ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
Lubrication Regimes ◽  
Lubrication Performance ◽  
Close Relationship

Predicting the mixed thermal lubrication performance and fatigue life of point contact components becomes more and more important with the increasing demand for the load capacity of machinery. To achieve this, a deterministic mixed thermal elastohydrodynamic lubrication (TEHL) model in point contacts considering surface roughness is developed in this study. This model is capable of determining the pressure and temperature under different lubrication regimes from mixed to full-film lubrication. Then, the established model is extended to the subsurface stress and fatigue life predictions. Numerical simulations are conducted to analyze the lubrication characteristics and fatigue life for the three-dimensional (3D) sinusoidal surfaces with variable directions. Results show that increasing entraining velocity contributes to the reduction of pressure fluctuation and prolongation of fatigue life. However, the resulting temperature increases with the entraining velocity. As for the influence of lubricant viscosity, increasing it prolongs the fatigue life, especially under mixed TEHL conditions. What's more, the effect of rough surface texture feature on fatigue life has a close relationship with the lubrication regime.

Influences of transient impact and vibration on the lubrication performance of spur gears

2020 ◽  
pp. 135065012092597
Author(s):  
Xingbao Huang ◽  
Bintang Yang ◽  
Youqiang Wang
Keyword(s):  
Film Thickness ◽  
Thermal Effect ◽  
Surface Deformation ◽  
Load Condition ◽  
Elastohydrodynamic Lubrication ◽  
Minimum Thickness ◽  
Film Pressure ◽  
Lubrication Performance ◽  
The Coefficient Of Friction ◽  
The Impact

In this paper, the mathematical model of gear elastohydrodynamic lubrication is presented. The transient impact operating condition and underdamped load condition are considered. Taking thermal effect and squeeze effect into account, the full numerical solution of gear pairs is obtained. In this numerical calculation, multigrid method is applied to compute the film pressure; multigrid integration technique is used to calculate the solid surface deformation; column by column scanning technique is employed to calculate temperature. The simulation results show that an entrapped film dimple forms under transient impact condition; transient impact causes remarkable increases in film pressure and film temperature. Compared with the normal case the minimum thickness of the impact case is smaller, which is not beneficial to teeth lubrication. Thermal effect induces some decreases in film thickness because of the viscosity–temperature relationship. Vibrational load with high damped frequency causes greater increases in film thickness and greater decreases in the coefficient of friction than that of low damped frequency. However, the film temperature of high damped frequency is higher than that of low damped frequency.

Plasto ‐elastohydrodynamic lubrication performance of greased ellipsoid contact

2021 ◽  
Author(s):  
Yong Zheng ◽  
Changqing Wang ◽  
Chao Pu ◽  
Jiayu Gong ◽  
Fanming Meng
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Lubrication Performance

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.

Simulation of Plasto-Elastohydrodynamic Lubrication in Line Contacts of Infinite and Finite Length

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Tao He ◽  
Jiaxu Wang ◽  
Zhanjiang Wang ◽  
Dong Zhu
Keyword(s):  
Surface Roughness ◽  
Finite Length ◽  
3D Model ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Axial Direction ◽  
Contact Length ◽  
Line Contact ◽  
Line Contacts ◽  
3D Surface Topography

Line contact is common in many machine components, such as various gears, roller and needle bearings, and cams and followers. Traditionally, line contact is modeled as a two-dimensional (2D) problem when the surfaces are assumed to be smooth or treated stochastically. In reality, however, surface roughness is usually three-dimensional (3D) in nature, so that a 3D model is needed when analyzing contact and lubrication deterministically. Moreover, contact length is often finite, and realistic geometry may possibly include a crowning in the axial direction and round corners or chamfers at two ends. In the present study, plasto-elastohydrodynamic lubrication (PEHL) simulations for line contacts of both infinite and finite length have been conducted, taking into account the effects of surface roughness and possible plastic deformation, with a 3D model that is needed when taking into account the realistic contact geometry and the 3D surface topography. With this newly developed PEHL model, numerical cases are analyzed in order to reveal the PEHL characteristics in different types of line contact.

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