A Parametric Study on Fatigue Life for Mixed Elastohydrodynamic Lubrication Point Contacts

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Xiao-Liang Yan ◽  
Xiao-Li Wang ◽  
Yu-Yan Zhang
Keyword(s):  
Shear Stress ◽  
Fatigue Life ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
Newtonian Flow ◽  
Lubrication Regimes ◽  
Close Relationship ◽  
Lubrication Characteristics ◽  
Effect Of Surface

The lubrication characteristics and fatigue life are numerically analyzed under full film and mixed lubrication regimes, in which the three-dimensional sinusoidal surfaces with changeable wavelengths in x and y directions are used, the geometry changes of the contact areas are described by the various ellipticity, and the non-Newtonian flow of lubricant is described by the sinh-law rheology model. The results show that the influences of characteristic shear stress, wavelength ratio, and ellipticity on lubrication characteristics and fatigue life are remarkable. The effect of surface topography on lubrication characteristics has a close relationship with speed. Increasing the ellipticity and decreasing wavelength ratio and characteristic shear stress can prolong the fatigue life.

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.

Effects of spinning on the mixed thermal elastohydrodynamic lubrication and fatigue life in point contacts

2019 ◽  
Vol 233 (12) ◽  
pp. 1820-1832 ◽  
Author(s):  
Xiaoliang Yan ◽  
Yuyan Zhang ◽  
Guoxin Xie ◽  
Fen Qin ◽  
Xuewen Zhang
Keyword(s):  
Fatigue Life ◽  
Power Loss ◽  
Numerical Study ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
Lubrication Characteristics ◽  
Sinusoidal Surface ◽  
Lubrication Conditions ◽  
Film Lubrication ◽  
Effect Of Surface

This paper presents a numerical study on the fatigue life for the non-Newtonian mixed thermal elastohydrodynamic lubrication (TEHL) of elliptical contacts with spinning. Sinusoidal surface is used to consider the effect of surface roughness, and the influences of spinning on the mixed TEHL characteristics and fatigue life are investigated. The results show that the temperature, friction coefficient and power loss increase monotonously with the increase of spinning. The spinning motion with moderate velocity is beneficial for improve the lubrication characteristics and fatigue life. However, the fatigue life can be reduced significantly by spinning under severe mixed lubrication conditions. The effects of spinning become weak or even negligible in the full-film lubrication state.

Plasto-Elastohydrodynamic Lubrication in Point Contacts for Surfaces With Three-Dimensional Sinusoidal Waviness and Real Machined Roughness

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Tao He ◽  
Ning Ren ◽  
Dong Zhu ◽  
Jiaxu Wang
Keyword(s):  
Plastic Deformation ◽  
Rough Surface ◽  
Mechanical Design ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Von Mises Stress ◽  
Asperity Contacts ◽  
Lubrication Characteristics ◽  
Von Mises

Efficiency and durability are among the top concerns in mechanical design to minimize environmental impact and conserve natural resources while fulfilling performance requirements. Today mechanical systems are more compact, lightweight, and transmit more power than ever before, which imposes great challenges to designers. Under the circumstances, some simplified analyses may no longer be satisfactory, and in-depth studies on mixed lubrication characteristics, taking into account the effects of 3D surface roughness and possible plastic deformation, are certainly needed. In this paper, the recently developed plasto-elastohydrodynamic lubrication (PEHL) model is employed, and numerous cases with both sinusoidal waviness and real machined roughness are analyzed. It is observed that plastic deformation may occur due to localized high pressure peaks caused by the rough surface asperity contacts, even though the external load is still considerably below the critical load determined at the onset of plastic deformation in the corresponding smooth surface contact. It is also found, based on a series of cases analyzed, that the roughness height, wavelength, material hardening property, and operating conditions may all have significant influences on the PEHL performance, subsurface von Mises stress field, residual stresses, and plastic strains. Generally, the presence of plastic deformation may significantly reduce some of the pressure spikes and peak values of subsurface stresses and make the load support more evenly distributed among all the rough surface asperities in contact.

Analysis of isothermal elastohydrodynamic point contacts lubricated by Newtonian fluids using multigrid methods

1997 ◽  
Vol 211 (7) ◽  
pp. 493-508 ◽  
Author(s):  
P Ehret ◽  
D Dowson ◽  
C M Taylor ◽  
D Wang
Keyword(s):  
Smooth Surface ◽  
Multigrid Method ◽  
Integration Method ◽  
Large Range ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
Dimensional Surface ◽  
Good Agreement

A multigrid multi-integration method has been used to solve the elastohydrodynamic lubrication (EHL) point contact problem over a large range of loads. Solutions obtained with the multigrid method are compared with those computed with an effective influence Newton method. Good agreement has been obtained, which validates the results obtained by both of these independent methods. Smooth surface problems have been used to test the multigrid method, but an example that takes into account a wavy surface has demonstrated the robustness and the large potential of the multigrid method to analyse EHL problems with three-dimensional surface roughness.

scholarly journals Predicting Fatigue Life for Finite Line Contact under Starved Elastohydrodynamic Lubrication Condition

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Mingyong Liu ◽  
Haofeng Ku ◽  
Jinxi Zhang ◽  
Peidong Xu ◽  
Chenhui Wu
Keyword(s):  
Fatigue Life ◽  
Contact Fatigue ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Line Contact ◽  
Finite Line Contact ◽  
Lubrication Performance ◽  
Finite Line ◽  
Lubrication Condition ◽  
Lubrication Characteristics

Surface contact fatigue is the main failure mode in many mechanical components, such as gears, bearings, and cam-followers. A fatigue life prediction model is proposed for finite line contact under starved thermal elastohydrodynamic lubrication (TEHL) condition in this paper. Then, the effects of inlet oil-supply thickness, slide-to-roll ratio (SRR), and operating conditions on the lubrication performance and fatigue life are investigated. The results show that the lubrication characteristics and fatigue life of finite line contact are obviously different from those of fully flooded situation by introducing the starved lubrication condition. For example, the severe starved conditions lead to a significant increase in friction coefficient and decreased fatigue life. The variation of SRR has an important influence on the fatigue life. With the increase of SRR, the fatigue life decreases firstly and then increases. The stress concentration occurs near the surface when speed is low. In addition, under the low-speed situation, rotation speed variation has little effect on the fatigue life.

Fatigue Life and Traction Modeling of Continuously Variable Transmissions

2002 ◽  
Vol 124 (4) ◽  
pp. 689-698 ◽  
Author(s):  
George K. Nikas
Keyword(s):  
Fatigue Life ◽  
Three Dimensional ◽  
Bulk Temperature ◽  
Continuously Variable Transmissions ◽  
Life Model ◽  
Variable Transmission ◽  
Ellipticity Ratio ◽  
Effect Of Surface ◽  
Generalized Reynolds Equation ◽  
Contact Efficiency

A model was developed to study the elastohydrodynamics and contact mechanics of toroidal Continuously Variable Transmission (CVT) type contacts. The aim is to predict the fatigue life, traction and efficiency of such contacts with the intention of making optimizations based on design criteria and constraints. A generalized Reynolds equation was developed for isothermal, transient lubrication of elliptical rough contacts with mixed rolling, two-dimensional sliding, and spinning conditions, incorporating any non-Newtonian model, roughness asperity isothermal elastoplastic interactions, and a three-dimensional subsurface stress analysis. The output is in the form of film thickness and traction maps, including contact efficiency, three-dimensional stress fields, and, finally, the predicted fatigue lives of CVT contacts, based on the Ioannides-Harris life model. A parametric study reveals the effect of surface roughness, lubricant bulk temperature, contact ellipticity ratio, slide-roll ratio, and contact load on the fatigue life, traction and contact efficiency of CVTs, and allows for design optimizations based on a compromise between life, traction and efficiency.

Influence of Roughness Parameters Skewness and Kurtosis on Fatigue Life Under Mixed Elastohydrodynamic Lubrication Point Contacts

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Xiao-Liang Yan ◽  
Xiao-Li Wang ◽  
Yu-Yan Zhang
Keyword(s):  
Fatigue Life ◽  
Elastohydrodynamic Lubrication ◽  
Von Mises Stress ◽  
Maximum Pressure ◽  
Point Contacts ◽  
Roughness Parameters ◽  
Numerical Studies ◽  
Non Gaussian ◽  
Von Mises ◽  
Skewness And Kurtosis

The numerical studies on the influences of surface parameters skewness and kurtosis on tribological characteristics under mixed elastohydrodynamic lubrication (mixed EHL) conditions are extended to fatigue life. Non-Gaussian rough surfaces are generated numerically with given autocorrelation function, skewness, and kurtosis. The results show that the maximum pressure increases as the skewness increases, however its variation with kurtosis is closely related to skewness. Similar trends to that of the maximum pressure are observed for the maximum von Mises stress. The fatigue life decreases as the skewness increases, however it undergoes apparent fluctuations with the increase of kurtosis. As the kurtosis increases, the influence of skewness on fatigue life becomes more significant, and vice versa.

Pulsatile Non-Newtonian Flow Characteristics in a Three-Dimensional Human Carotid Bifurcation Model

1991 ◽  
Vol 113 (4) ◽  
pp. 464-475 ◽  
Author(s):  
K. Perktold ◽  
M. Resch ◽  
H. Florian
Keyword(s):  
Shear Stress ◽  
Carotid Sinus ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Outer Wall ◽  
Maximum Diameter ◽  
Newtonian Flow ◽  
Pulse Cycle ◽  
Flow Phenomena ◽  
Human Carotid

Numerical analysis of flow phenomena and wall shear stresses in the human carotid artery bifurcation has been carried out using a three-dimensional geometrical model. The primary aim of this study is the detailed discussion of non-Newtonian flow velocity and wall shear stress during the pulse cycle. A comparison of non-Newtonian and Newtonian results is also presented. The applied non-Newtonian behavior of blood is based on measured dynamic viscosity. In the foreground of discussion are the flow characteristics in the carotid sinus. The investigation shows complex flow patterns especially in the carotid sinus where flow separation occurs at the outer wall throughout the systolic deceleration phase. The changing sign of the velocity near the outer sinus wall results in oscillating shear stress during the pulse cycle. At the outer wall of the sinus at maximum diameter level the shear stress ranges from −1.92 N/m2 to 1.22 N/m2 with a time-averaged value of 0.04 N/m2. At the inner wall of the sinus at maximum diameter level the shear stress range is from 1.16 N/m2 to 4.18 N/m2 with a mean of 1.97 N/m2. The comparison of non-Newtonian and Newtonian results indicates unchanged flow phenomena and rather minor differences in the basic flow characteristics.

Experimental and Numerical Investigations of the Stribeck Curves for Lubricated Counterformal Contacts

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Tao He ◽  
Dong Zhu ◽  
Jiaxu Wang ◽  
Q. Jane Wang
Keyword(s):  
Shear Stress ◽  
Elastohydrodynamic Lubrication ◽  
Stribeck Curve ◽  
Boundary Lubrication Friction ◽  
Lubrication Regimes ◽  
Limiting Shear Stress ◽  
Wide Range ◽  
Basic Characteristics ◽  
Stribeck Curves ◽  
Film Lubrication

The Stribeck curve is an important means to demonstrate the frictional behavior of a lubricated interface during the entire transition from boundary and mixed to full-film lubrication. In the present study, a new test apparatus has been built that can operate under rolling–sliding conditions at a continuously variable speed in an extremely wide range, approximately from 0.00006 to 60 m/s, covering six orders of magnitude. Hence, a complete Stribeck curve can be measured to reveal its basic characteristics for lubricated counterformal contacts. The measured curves are compared with numerical simulation results obtained from an available unified mixed elastohydrodynamic lubrication (EHL) model that is also capable of handling cases during the entire transition. A modified empirical model for the limiting shear stress of lubricant is obtained, and a good agreement between the measured and calculated Stribeck curves is achieved for the tested base oils in all the three lubrication regimes, which thus well validates the simulation methods employed. Both the experimental and numerical results indicate that the Stribeck curves for counterformal contact interfaces behave differently from those for conformal contacts. When the rolling speed increases at a fixed slide-to-roll ratio, the friction continuously decreases even in the full-film lubrication regime due to the reduction of the lubricant limiting shear stress caused mainly by the rise of the surface flash temperature. In addition, the test results indicate that the boundary additives in a commodity lubricant may have considerable influence on the boundary lubrication friction but that on the friction in the mixed and full-film lubrication appears to be limited.

The Effects of Surface Texture on EHL Point Contacts

1996 ◽  
Vol 118 (1) ◽  
pp. 59-66 ◽  
Author(s):  
Xiaolan Ai ◽  
Herbert S. Cheng
Keyword(s):  
Surface Texture ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Point Contact ◽  
Maximum Pressure ◽  
Point Contacts ◽  
Random Roughness ◽  
Minimum Film Thickness ◽  
Transverse Roughness ◽  
Effect Of Surface

The effect of surface texture on EHL point contact is studied numerically by using the multigrid method. Numerical simulations have been performed for waviness and random roughness with three different orientations, transverse, oblique and longitudinal. Results reveal a strong domination of unidirectional Couette flow in the EHL conjunction. The geometrical variations at inlet of the contact are transported downstream throughout the EHL conjunction. As a consequence, the oblique surface roughness striations are largely distorted, forming nearly longitudinal wavy passages. Results show that the oblique roughness induces local three dimensional EHL pressure fluctuations. The maximum pressure is higher than that of the transverse roughness. For sinusoidal waviness, oblique orientation gives the smallest minimum film thickness as compared with those of longitudinal and transverse waviness.

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