A fatigue life prediction method of rolling bearing under elliptical contact elastohydrodynamic lubrication

In order to more accurately predict the contact fatigue life of rolling bearing, a prediction method of fatigue life of rolling bearing is proposed based on elastohydrodynamic lubrication （EHL）, the 3-paameter Weibull distribution ad fatigue strength. First,the contact stress considering elliptical EHL is obtained by mapping film pressure onto the Hertz zone. Then,the basic strength model of rolling bearing based on the 3-parameter Weibull distribution is deduced by the series connection reliability theory. Considering the effect of the type of stress, variation of shape and fuctuation of load, the mathematical models of the 尸 -tS-TV curve of the minimum life and the characteristic life for rolling bearing are established, respectively, and thus the prediction model of fatigue life of rolling bearing based on the 3-paameter Weibull distribution and fatigue strength is further deduced. Finally, the contact fatigue life obtained by the proposed method ad the latest international standard （IS0281： 2007） about the fatigue life prediction of rolling bearing are compared with those obtained by the statistical method. Results show that the proposed prediction method is effective and its relative error is smaier than that of the latest international standard （IS0281： 2007） with reliability R 〉 0. 93.

ELASTOHYDRODYNAMIC LUBRICATION OF LOGARITHMIC PROFILE ROLLER CONTACTS

An account of numerical solutions to the isothermal and flooded elastohydrodynamic lubrication(EHL)of a logarithmic profile roller,which is rolling over a flat plane,is given The analysis takes account of sideways flow of lubricant in the inlet region of the contact When the results are presented in suitable non dimensional groups,it is shown that more uniformly pressure and shape of the film distributing in axial direction is taken place under light loading As the increase of the load,the end closure is displayed and the oil pressure rises sharply at the ends The seal action formed by the end closure makes the film thickness a little And the minimum film thickness is transferred from the central to the ends and the value is reduced rapidly As the increase of the speed,the end closure becomes much serious The optimum crowning value obtained in EHL state is larger than the design value obtained in elastostatic contact state for the same working conditions In order to verify the correctness of theory,optical interferometry is applied to measure the oil film thickness between a logarithmic profiled roller and a glass plate under pure rolling conditions It is found the agreement between numerical solutions and experiments is very good.

Elastohydrodynamic Lubrication Studies on Effects of Crowning Value in Roller Bearings

The purpose of this paper is to present a comparison of numerical calculations and experiment results of optical interferometry in finite line contact for the elastohydrodynamic lubrication(EHL) problem of Lundberg's profiled cylindrical roller under the conditions of flooded state, moderate load and material parameter. It shows clearly the effects of crowning value on the variations of oil film shape and thickness. The agreement between numerical analysis and experiment results is very good. The results indicate there must be an optimum crowning value that will induce the thickest and most even oil film in EHL state for a given working condition, and this value is larger than the design value in dry contact state for the same working conditions.

Jacobian-free Newton-Krylov subspace method with wavelet-based preconditioner for analysis of transient elastohydrodynamic lubrication problems with surface asperities

This paper presents an investigation into the effect of surface asperities on the over-rolling of bearing surfaces in transient elastohydrodynamic lubrication(EHL) line contact. The governing equations are discretized by the finite difference method. The resulting nonlinear system of algebraic equations is solved by the Jacobian-free Newtongeneralized minimal residual(GMRES) from the Krylov subspace method(KSM). The acceleration of the GMRES iteration is accomplished by a wavelet-based preconditioner.The profiles of the lubricant pressure and film thickness are obtained at each time step when the indented surface moves through the contact region. The prediction of pressure as a function of time provides an insight into the understanding of fatigue life of bearings.The analysis confirms the need for the time-dependent approach of EHL problems with surface asperities. This method requires less storage and yields an accurate solution with much coarser grids. It is stable, efficient, allows a larger time step, and covers a wide range of parameters of interest.

The size-dependent elastohydrodynamic lubrication contact of a coated half-plane with non-Newtonian fluid

Based on the couple-stress theory,the elastohydrodynamic lubrication(EHL)contact is analyzed with a consideration of the size effect.The lubricant between the contact surface of a homogeneous coated half-plane and a rigid punch is supposed to be the non-Newtonian fluid.The density and viscosity of the lubricant are dependent on fluid pressure.Distributions of film thickness,in-plane stress,and fluid pressure are calculated by solving the nonlinear fluid-solid coupled equations with an iterative method.The effects of the punch radius,size parameter,coating thickness,slide/roll ratio,entraining velocity,resultant normal load,and stiffness ratio on lubricant film thickness,in-plane stress,and fluid pressure are investigated.The results demonstrate that fluid pressure and film thickness are obviously dependent on the size parameter,stiffness ratio,and coating thickness.

STUDY ON THE LUBRICATION FACTOR OF INVOLUTE SPUR GEARS

Based on a lot of numerical solutions to the problems of the thermalnon-Newtonian elastohydrodynamic lubrication and some fatigue tests with rollers, the lubricationfactor of involute spur gears (called gear for short) is investigated. The results suggest that gearlubrication effects bear close relations to a dimensionless parameter D which is syntheticallydetermined by gearing rotational speed, load, material, dimension and lubricant viscosity. When D<=8, the gear fatigue life increases as the lubricant viscosity is increased; When D>8, however, thelife decreases with the viscosity addition, which is in marked contrast to the lubrication factorZ_L recommended by the International Standard for Computing Cylindrical Gear Strength. At the end, aset of formulae for calculating gear lubrication factors suitable for different working conditionsare advanced.

Influence of Lubrication Performance on the Service Life of Rolling Mill Bearings

In order to confirm the early failure cause of a four-row cylindrical roller bearing at the backup roll position of a six-high cold sheet mill, its lubrication behavior under harsh operating conditions is investigated. Through establishing and solving the Elastohydrodynamic Lubrication （EHL） model of the roller-inner raceway contact region, the minimum oil film thickness and the real lubrication performance are achieved. The results show the bearing failures come from the poor oil film thickness in the case of high temperature and low rotational speed, which leads to contact wear. So various approaches to improve bearing life via improving lubrication are compared. It has been proved decreasing surface roughness of both contact bodies is an effective way.

A GENERALIZED REYNOLDS EQUATION BASED ON NON-NEWTONIAN FLOW IN LUBRICATION MECHANICS

A generalized Reynolds equation based on non-Newtonian flow is derived in this paper.This equation is suitable for a number of non-Newtonian flow models and can be solved numerically to obtain pressure fields in thermalhydrodynamically or elastohydrodynamically lubricated fluid films.A mathematical ap- proach is given for solving simultaneously the shearing stress,shearing rate,velocity and equivalent viscosity.To show the application of this equation,two rheological models which have been widely used in lubrication mechnaics are incorporated into this equation to obtain numerical solutions to the line contact thermal elastohydrodynamic lubrication problem.

A new general rheological model for rheological lubrication

Limitation and deficiency of main thcoogical models at present are descrital and analyzed, and seteralgeneral rheological models are discussed and compared with each other, and basic demands for a general model aresummarized. The constitutive eqUation is proposetl for a new general theobocal model. The general medel feaaressimple structure and wide coverage, and can take the Place of many edsting thcofogical ed. The whel has suc-cessfully been used for Elastohydrodynamic lubrication calculation.

Influence of water evaporation on elastohydrodynamic lubrication with water-containing polyalkylene glycols

The reduction of frictional power losses in power transmitting gears takes a crucial role in the design of energy-and resource-efficient drivetrains.Water-containing lubricants like glycerol and polyalkylene glycols have shown great potential in achieving friction within the superlubricity regime with coefficients of friction lower than 0.01 under elastohydrodynamic lubrication.Additionally,a bio-based production of the base stocks can lead to the development of green lubricants.However,one challenge associated with the application of water-containing lubricants to gearboxes is the evaporation of water and its impact on the lubricant properties.In this study,the influence of water evaporation on elastohydrodynamic friction and film thickness was investigated for three water-containing polyalkylene glycols.Two nominal water contents of 20 wt%and 40 wt%and two viscosities were considered.The results show that the friction increases continuously with higher evaporated water content,while the overall friction level remains low in nearly water-free states.A similar trend is observed for film thickness,where the strong increase in viscosity results in a notable increase in film thickness.Nevertheless,the sensitivity of friction and film thickness to water evaporation is low for small amounts of evaporated water.This allows generous thresholds for permissible variations in water content.

NUMERICAL ANALYSIS OF ELAS－TOHYDRODYNAMIC LUBRICATION WITH TRANSIENT VISCOSITY

The transient vistosity response of a lubricant following the pressure charge in a EHDcontact is consideied in the line-contact isothermal elastohydrodynamic lubrication analyses. Soobtained pressure distribution and the oil film thickness are different from those obtained with equi-librium viscosity.

Influence of thermal effects on elastohydrodynamic(EHD) lubrication behavior at high speeds

This paper describes a study of point contact elastohydrodynamic(EHD)lubrication behavior at high speeds(up to 20 m s1).Central film thicknesses were measured by optical interferometry device.The influence of slide-roll ratio and operating temperature on the central film thickness was determined.The influence of thermal effects on the reduction of film thickness was discussed via the analysis of numerical simulation method considering thermal effects.Subsequently,the experimental data was used to amend a set of unified parameters for the thermal corrections for different types of oil at high speeds.

内燃机主轴承EHD模拟计算研究

在充分考虑轴承座、瓦背、减摩合金层的弹性变形及轴颈、轴瓦表面粗糙度因素的影响基础上,对某4100QB柴油机主轴承进行了综合的EHD模拟计算研究。采用有限差分法与有限元法相结合对轴承的油膜压力、油膜厚度、弹性变形、表面粗糙度进行了耦合分析,并将EHD耦合算法结果与刚性分析结果及仅考虑轴瓦弹性变形的分析结果进行了比较分析。结果表明,综合考虑轴承座、瓦背、减摩合金层弹性变形及轴颈、轴瓦表面粗糙度因素影响的弹流润滑研究更符合实际工况,其油膜厚度增大,油膜压力减小,油膜承载区扩大,且在轴承载荷峰值处表现最为明显。

一个空间用球轴承 EHD 润滑设计的 CAD 程序

编制了一个适用于空间用球轴承 EHD 润滑设计的机辅软件.

空间用球轴承EHD润滑设计中的几个问题

提出了对空间用长寿命球轴承进行EHD润滑设计时须特别注意的两个问题,即润滑剂的选择和预载的确定,并深入分析了它们对轴承使用性能与寿命的影响.

Grease film evolution in rolling elastohydrodynamic lubrication contacts

Although most rolling element bearings are grease lubricated,the underlying mechanisms of grease lubrication has not been fully explored.This study investigates grease film evolution with glass disc revolutions in rolling elastohydrodynamic lubrication(EHL)contacts.The evolution patterns of the grease films were highly related to the speed ranges and grease structures.The transference of thickener lumps,film thickness decay induced by starvation,and residual layer were recognized.The formation of an equilibrium film determined by the balance of lubricant loss and replenishment was analyzed.The primary mechanisms that dominate grease film formation in different lubricated contacts were clarified.

Elastohydrodynamic lubrication properties and friction behaviors of several ester base stocks

This paper reports a series of studies on the lubricant properties,elastohydrodynamic film thickness,and coefficients of friction of several commercially available ester base stocks,i.e.,diisooctyl phthalate(DIOP),diisodecyl phthalate(DIDP),diisotridecyl phthalate(DITDP),diisooctyl sebacate(DOS),diisotridecyl sebacate(DTDS),trihydroxymethylpropyl trioleate(TMPTO),and pentaerythritol tetraoleate(PETO).The results include densities and viscosities from 303 to 398 K,and elastohydrodynamic lubricant film thicknesses and friction in the boundary,mixed and full-film lubrication regimes measured at several temperatures,loads,and speeds.These ester base stocks have different lubrication abilities owing to their chain lengths,geometric configurations,and molecular rigidity.This study provides quantitative insight into the use of ester-based lubricants for low friction through the entire lubrication regime(boundary to full film)by utilization of suitable type and size of the ester base stocks.

State of the art of friction modelling at interfaces subjected to elastohydrodynamic lubrication(EHL)

Elastohydrodynamic lubrication(EHL)is a type of fluid-film lubrication where hydrodynamic behaviors at contact surfaces are affected by both elastic deformation of surfaces and lubricant viscosity.Modelling of contact interfaces under EHL is challenging due to high nonlinearity,complexity,and the multi-disciplinary nature.This paper aims to understand the state of the art of computational modelling of EHL by(1)examining the literature on modeling of contact surfaces under boundary and mixed lubricated conditions,(2)emphasizing the methods on the friction prediction occurring to contact surfaces,and(3)exploring the feasibility of using commercially available software tools(especially,Simulia/Abaqus)to predict the friction and wear at contact surfaces of objects with relative reciprocating motions.

Influence of electric double layer on thin film lubrication and elastohydrodynamic lubrication

In the present paper, the influence of electric double layer (EDL) on thin film lubricationand elastohydrodynamic lubrication is studied. With modified Reynolds equation for electric doublelayer, the effect of zeta-potential on the film thickness and pressure is numerically calculated. Theresults show that the influence of electric double layer on the lubrication film thickness is significantonly for thin film. The minimum film thickness will increase greatly if the influence of EDL is con-sidered. As the initial film thickness increases, the effect will greatly decrease. The existence ofEDL will decrease the friction coefficient of the lubrication film. Furthermore, the above tendency isstill applicable even if the materials of the friction pair are different.

ON THE TRACTION BEHAVIOR OF 4109 CHINESE AVIATION LUBRICANT

Based on improved test rig with cooling system, the traction experiments for 4109 Chinese aviation lubricant are tested under various simulated working conditions. Both the experimental data thanks to their accuracy and stability and the better cooling effect of the electric shafts has given the rationality of the experimental rig a strong support. An empirical equation for calculating the traction coefficient of 4109 lubricant, which may be conveniently used for engineering application,is obtained. Furthermore, the rheological properties of the lubricant are investigated.