Elastohydrodynamic Film Thickness Mapping by Computer Differential Colorimetry

This paper describes a new experimental technique for the study of elastohydrodynamic (EHD) lubricant films. This technique, which is based on the computer processing of EHD chromatic interferograms, uses a combination of image analysis and differential colorimetry for film thickness evaluation. This approach overcomes some major limitations of conventional optical interferometry and allows the precise mapping of lubricant film thickness distribution in EHD contacts, including transient and quasistatic phenomena. The technique has been used for the evaluation of chromatic interference patterns obtained from a conventional optical test rig for rolling point contacts. Three-dimensional representations of lubricant film thickness and shape with high accuracy and spatial resolution have been obtained. The technique's accuracy has been checked and a comparison with conventional monochromatic interferometry has been done for validation. The technique's resolution has been confirmed through the observation of local film thickening just before the EHD exit constriction for both pure rolling and sliding conditions.     

A New Method for Measuring the Film Thickness of Mixed Lubrication in Line Contacts

In the present paper, an optical method, called frustrated total reflection (FTR), for measuring the film thickness of mixed lubrication in line contacts is proposed. The principles of FTR are analyzed. The relationship between the reflectivity and the film thickness is derived. The measuring methods and procedures are described.     

The Development of a Spacer Layer Imaging Method (SLIM) for Mapping Elastohydrodynamic Contacts

Optical interferometry has proved to be a valuable experimental tool in the study of elastohydrodynamic lubrication (EHD). It is a technique that gives detailed information on the lubricant film distribution within the contact; however, the sensitivity is limited and it is only recently, with the development of the spacer layer optical technique, that the study of the thin film lubrication regime has been possible. The limitation of the spacer layer technique is that generally only one measurement is taken from the center of the contact. The next logical step in the development of this technique is, therefore, a system that combines the mapping capabilities of the original optical method with the thin film capabilities of the spacer layer approach.

This paper describes the development of a contact mapping technique that uses the spacer layer approach to visualize, and measure, thin lubricant films in concentrated contacts. The development of the technique is described and its application to both static and moving contacts reported. Thin EHD films (down to 10 nm) have been measured and mapped.     

Microprocessor Control of Running-in of Plain Bearings

Correct running-in procedures have a major influence on the subsequent life and performance of a plain bearing. With very large bearings, the process can be both time-consuming and expensive.

It is necessary to control the running-in conditions very carefully, since too thick a lubricant film, will retard the running-in, while too little lubrication will lead to overheating and possible damage or even seizure. Since the surface topography is changing continuously during running-in, the optimum lubrication condition also changes.

This paper describes a new bearing rig in which running-in parameters are monitored and fed to a microprocessor which, in turn, controls the loading and speed conditions. The objective is to obtain correct running-in, in the minimum possible time.     

The Formation of Viscous Surface Films by Polymer Solutions: Boundary or Elastohydrodynamic Lubrication?

The film-forming properties of a range of polymer solutions have been studied down to very thin film thickness using ultrathin film interferometry.

It has been found that, at very slow rolling speeds, some polymers generate much thicker films than predicted from theory. It appears that these polymers form adsorbed layers between three and 15 nanometers thick on the two solid surfaces. These layers have a viscosity many times higher than that of the bulk solution. Therefore, under slow speed, low film thickness conditions, the contact effectively operates within a viscous boundary layer, generating an elastohydrodynamic-type film much thicker than predicted from the viscosity of the bulk lubricant. As the speed is raised the contact emerges from this boundary layer and reverts to elastohydrodynamic behavior based upon the viscosity of the bulk polymer solution.     

Analysis on Isothermal Elastohydrodynamic Lubrication of Orthogonal Face Gear

Face-gear drives have been applied in aviation transmissions, in particular, helicopter transmissions, and the lubrication characteristics are an important indicator for estimating the load-carrying capacity of face-gear teeth. In order to analyze the lubrication performance of the face gear under load, equations for the contact path of the face gear loaded tooth contact analysis (LTCA) were established on the basis of the load equivalent error of alignment (LEEA) and the load distribution among the teeth was calculated. Then a method for calculating the contact area and tooth surface velocity of face-gear drives was studied. Face-gear isothermal elastohydrodynamic lubrication (EHL) dimensionless equations are presented. A multigrid algorithm was used to complete the solution of the minimum film thickness and film pressure of face-gear drives. The lubricant film thickness and film pressure variation in the mesh cycle are expressed using example calculations that provide a theoretical basis for face-gear lubrication design.     

齿轮几何参数对齿轮传动弹流润滑性能的影响

本文采用热弹性流体动力润滑理论对渐开线直齿轮传动进行热弹流数值分析;计算分析了在给定传动比和中心距条件下,齿轮模数、齿数以及变位系数等几何参数对齿轮润滑性能的影响,获得了齿轮传动沿啮合线的中心油膜厚度、压力、温度以及轮齿表面摩擦系数等分布规律。     

水润滑橡胶轴承的弹流润滑分析

本对水润滑橡胶套筒轴承进行了弹流润滑分析。橡胶衬层多沟槽机理的几何结构由有限元软件MARC产生．以近似不可压缩的线弹性体为力学模型,应用MARC产生了橡胶衬层的柔度矩阵,流体润滑方程采用的是紊流雷诺方程。计算了水润滑模胶轴承的水膜压力分布、厚度分布和承载能力,揭示的变形特征和实验结果相一致。     

粘塑性流体弹流润滑的研究进展

介绍了粘塑性流体弹流润滑产生的背景、国内外的研究现状,阐述了粘塑性流体弹流润滑未来亟待解决的问题。     

弹性流体动力润滑发展的拐点研究

本文通过总结研究弹性流体动力润滑（以下简称弹流）自创立以来近半个世纪的发展历程,找出了对其发展起着重大作用的四个拐点,分析并揭示了其内在规律。     

Rheology of Perfluoropolyalkylether Fluids in Elastohydrodynamic Lubrication

The rheological characteristics of two branched and two linear, commercial perfluoropolyalkylether (PFPAE) fluids were studied under high pressures and temperatures. The effects of branching and carbon-to-oxygen (C:O) ratio on the pressure-viscosity-temperature behavior and on the non-Newtonian behavior of these fluids were studied experimentally under high pressures and temperatures. The branching and the higher C:O ratio seemed to increase the pressure-viscosity coefficients of these fluids. The effects of the viscosity and the pressure-viscosity coefficient on the capabilities of these fluids to generate elastohydrodynamic lubrication (EHL) film thickness were studied and compared with experimental measurements. All of the fluids studied seemed to follow the Roelands viscosity model and classical EHL theory (1). The C:O ratio also influenced the temperature dependence of the limiting-shear-strength proportionality constant. The results show that for similar-viscosity fluids, the linear PFPAE with higher C:O ratio is most desirable for wide temperature use.     

基于弹性流体动压润滑条件的滚动轴承耐磨损设计

分析了弹性流体动压润滑的理论和条件,阐述了基于弹性流体动压润滑的圆柱滚子轴承耐磨损设计的方法和步骤。     

Lubrication of Aluminum Rolling by Oil-in-Water Emulsions

The dynamic concentration model for lubrication by oil-in-water emulsions proposed by Wilson el al. (1) is applied to strip rolling to derive a relatively simple equation for inlet film thickness. The predictions of the new model are supported by rolling experiments using emulsions as lubricants, where the film thickness is inferred from the surface roughness that is generated on the workpiece during rolling. The experiments also seem to suggest that the efficiency of oil droplet capture increases with increasing rolling speed.     

Some Implications of Surface Texture in Partial Elastohydrodynamic Lubrication

A simplified, semianalytical model has been developed to analyze the effect of centrifugal inertia in two-phase face seals. The model is based on the assumption of isothermal flow through the seal, but at an elevated temperature, and takes into account heat transfer and boiling. Using this model, seal performance curves are obtained with water as the working fluid. It is shown that the centrifugal inertia of the fluid reduces the load-carrying capacity dramatically at high speeds and that operational instability exists under certain conditions. While an all-liquid seal may be starved at speeds higher than a “critical” value, leakage always occurs under boiling conditions.     

凸轮弹性流体动力润滑油膜厚度计算的新方法

本文先给出了全膜线接触弹流膜厚计算的统一公式，应用弹性流体动力润滑理论，探讨了凸轮油膜厚度的计算方法，利用MATLAB软件编制的程序可计算凸轮弹性流体润滑油膜厚度，凸轮膜厚比λ，从而能判断摩擦副之间的润滑状态，并对判断凸轮表面损伤坏形式，减少两接触表面的磨损，凸轮参数优化设计和使用寿命预测等具有重要意义。     

卷吸速度为任意方向的椭圆接触弹流润滑分析

以往的点接触弹流润滑研究往往局限于分析卷吸速度方向与接触椭圆短轴相重合的工况。但在实际工程问题中,有时卷吸速率方向与接触椭圆长轴相重合,有时卷吸速度方向与接触椭圆的对称轴成一夹角,针对这一问题,本文提出了一种独特的解决方法,压力和膜厚分析分别采用多重网格和多重网格积分法,无论卷吸速度的方向如何,总让Ｘ轴与速度方向一致,而Ｙ方向速度永远等于０。这样任意卷吸速度方向的工况和卷吸速度与接触椭圆短轴相重合     

Approaching Mixed Elastohydrodynamic Lubrication of Smooth Journal-Bearing Systems with Low Rotating Speed

When a conformal interface is under low velocity and heavy load conditions, solid contact (or dry contact) may occur even in a system with smooth surfaces. This paper presents two approaches for solving steady-state and transient mixed elastohydrodynamic lubrication problems of journal bearings with smooth surfaces under low rotating speed. The first approach uses the reduced Reynolds equation with a combined finite element–backward finite difference scheme and the second applies a zero film thickness equation to describe the mechanical behavior of mating surfaces at solid contact points. The major advantages of these two approaches are (1) no division of the solution domain into a lubricated area and a solid contact area is necessary and (2) the solid contact pressure, lubricant pressure, and eccentricity ratio can be solved simultaneously. Numerical examples are presented for the application of these approaches. For the steady-state cases under low velocity studied in this work, pressure distributions approach those found in a dry contact state. This comparison confirms that the contact treatments are proper. Moreover, a transient case under sinusoidal loading was analyzed with these two approaches, and the results showed good agreement. This comparison further supports the use of these approaches.     

非对称聚合物齿轮的瞬态弹流润滑分析

聚合物齿轮质轻而耐腐蚀,可降低噪声,提高经济效益.相对地,聚合物轮齿强度低于金属轮齿,故采用非对称设计提高聚合物齿轮的强度.为探究非对称聚合物齿轮的弹流润滑特性,在水润滑条件下,采用多重网格法对非对称聚合物齿轮进行了瞬态弹流润滑分析:对比非对称齿轮与传统对称齿轮的水膜压力与厚度;改变齿轮运行工况及考虑轮齿的表面粗糙度,...     

An Investigation of Seal Materials for High-Temperature Application

Novel rotating seal materials were developed by powder metallurgy techniques for potential aircraft applications at high speeds and high temperatures.

A systematic wear study without lubrication included several commercially available materials and the following types of experimental materials: (a) pure refractory hard metals, (b) binary alloys of refractory hard metals bonded with nickel and, (c) ternary alloys of refractory hard metals bonded with nickel and infiltrated with silver.

Two ternary alloys, containing nickel bonded WB or CrN and infiltrated with silver, showed superior wear qualities against either tool steel or a nickel—chromium—iron alloy at a sliding speed of 29,000 ft/min under a 14 lb/in² load and at ambient temperatures as high as 1300 F. A commercial titanium carbide composition showed excellent wear characteristics in contact with an identical composition at a sliding speed of 14,000 ft/min under a 16 lb/in² load and at an ambient temperature of 1050 F.