The Numerical Study of Piston Ring Elastohydrodynamic Lubrication by the Multigrid Method

Numerical analysis of elastohydrodynamic lubrication of piston rings requires that the solutions are able to converge quickly. In this paper, a new powerful numerical method, the Multigrid method, has been introduced, and the numerical problem has been solved successfully. The computing process and practice are expounded. In addition, a new radial force equilibrium equation taking the internal force into account has been proposed and a more precise formula for calculating the radial displacement has been used. Both of these make the calculations more accurate. The oil film thickness values presented in this paper have been compared with those published before. It can be shown that former values are closer to the measured values.     

用动态电压法判断斜齿轮润滑状态的实验研究

本文针对斜齿圆柱齿轮的啮合特点，沿齿面接触线方向设置传感器，在GZ150型可调速调载封闭功率流高速齿轮实验台上，对斜齿圆柱齿轮多种工况条件下的齿面润滑状态进行了动态跟踪监测，并且分析了转速及载荷对润滑状态的影响。     

考虑粗糙表面特征等温弹流渐开线直齿齿轮的数值分析

采用了Patir and cheng的平均流动模型,通过联立求解弹流基本方程组,获得渐开线齿轮啮合过程的油膜压力、膜厚,并分析了啮合过程中表面粗糙度对齿轮传动最小膜厚和压力的影响。采用多重网格法,使计算具有快速收敛性和数值稳定性。     

考虑粗糙表面特征等温弹流渐开线直齿齿轮的数值分析

采用了Patir and cheng的平均流动模型，通过联立求解弹流基本方程组，获得渐开线齿轮啮合过程的油膜压力、膜厚，并分析了啮合过程中表面粗糙度对齿轮传动最小膜厚和压力的影响。采用多重网格法，使计算具有快速收敛性和数值稳定性。     

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.     

渐开线标准直齿圆柱齿轮基本参数的一种速定法

针对目前渐开线直齿圆柱齿轮设计中齿数、模数较难初定的问题，提出了一种简便可行的方法。通过采用最小二乘法拟合方式，逐步拟定相应的经验公式。给出了一个实例，并指出了本文方法确定渐开线直齿圆柱齿轮基本参数的特点。     

齿轮传动的瞬态弹性流体动力润滑

本文考虑了流体可压缩性，衙合度对轮齿荷的影响以及变曲率，变速度的瞬态效应，给出了齿轮传动瞬态弹流润滑方程及其求解方法，在引入齿轮传动的实际工况参数后进行完全数值解，得到了两齿轮在啮合线任意上的油膜压力分布和油膜形状以及最小油膜厚度沿啮合线的变化曲线。     

Anomalous Low Friction Under Boundary Lubrication of Steel Surfaces by Polyols

We present here anomalous low friction obtained with highly polished steel on steel hard contact lubricated by glycerol under severe mixed and boundary regimes (λ ratio below 1). We investigated the effects of contact pressure, sliding speed, and temperature on friction coefficient and electrical contact resistance. The mechanism of low friction (typically below 0.02) is thought to have two origins: first a contribution of an ultrathin EHL film of glycerol providing easy shear under pressure, second the chemical degradation of glycerol inside the contact when more severe conditions are attained, generating a nanometer-thick film containing shear-induced water molecules. This new mechanism, called “H-bond Network model”, is completely different from the well-accepted “Monolayer” model working with polar molecules containing long aliphatic chains. Moreover, we show outstanding superlubricity (friction coefficient below 0.01) of steel surfaces directly lubricated by a solution of myo-inositol (also called vitamin Bh) in glycerol at ambient temperature (25 °C) and high contact pressure (0.8 GPa) in the absence of any long chain polar molecules. Mechanism is still unknown but could be associated with friction-induced dissociation of inositol and H-bond interactions network of water-like species with steel surface.     

大直径渐开线斜齿轮修整数控加工技术

利用成形法磨齿高精度、高效率的优点,结合砂轮在线修整技术,提出一种具体的针对硬齿面大直径渐开线斜齿轮的数控加工技术,并对采用此加工技术磨削成形的渐开线斜齿轮精度进行测量与分析。精度测量结果表明,采用此方法加工的渐开线斜齿轮精度可达到4级。     

A Lubrication Deviation From the Classical EHL Theory by the Lubricant Viscoplasticity: Part II — Boundary of Lubrication Regimes

This paper distinguishes elastahydrodynamic lubrication (EHL) regimes in isothermal pure rolling case as three kinds according to lubricant rheology. In these regimes, the lubricants are respectively viscoelastic, viscoplastic, and non-continuum. Mathematical expressions are introduced ta describe the boundaries among these three regimes. H_c - r_it and U - W charts respectively plot the operational scopes of these lubrication regimes. The present study holds significance to understanding EHL film formation and more clearly embodies elastohydrodynamic film failure stage transitions.     

Polyethylene as an Additive for Mineral Oils — Part II: EHL Traction Behavior

In Part I of the paper ((1999), Trib. Trans., 42, pp. 851–859) we investigated the effect of the polyethylene concentration on the film forming properties in a rolling bearing. This second part presents the influence of the polymer additive concentration on the traction behavior experienced using a two-disk machine at different temperatures and contact pressures.

By using the traction data, a semi-empirical approach for determining the effective lubricant theological parameters in EHL contacts was performed. Using this approach, the effect of polymer concentration upon rheological parameters that appear in the Johnson and Tevaarwerk model with Eyring stress was quantified.     

渐开线螺旋齿轮的成形磨削研究

结合渐开线螺旋面的形成原理,推导了渐开线处于某一位置时的渐开线螺旋面方程;依据盘状刀具加工螺旋齿面的基本原理,详细推导了盘状刀具加工螺旋齿面时的接触条件;在已知渐开线螺旋面方程的情况下,利用坐标变换得到了盘状刀具和渐开线螺旋齿轮所在坐标系之间的关系;通过求解接触条件式得到了接触线上的离散点,从而得到了接触线上的点在砂轮齿廓上所对应的离散点,通过点拟合得到了砂轮的成形齿廓,为渐开线螺旋齿轮的成形磨削提供了一种新方法。     

谐波齿轮传动齿面润滑计算的研究

本文将摩擦学理论应用到谐波齿轮传动中,针对谐波齿轮传动的啮合原理、运动关系、载荷分布、柔轮及轮齿受载后产生弹性变形等特点,建立了可行的齿面最小油膜厚度计算公式,为谐波齿轮传动齿面润滑状态的分析奠定了基础。     

单粗糙峰对摆线针轮弹流润滑的影响

以弹流润滑理论为基础,利用多重网格法,研究了啮合表面单粗糙峰的存在对摆线针轮时变弹流润滑的影响,并将不同幅值和波长条件下的粗糙解与光滑解进行了比较。结果表明,粗糙峰幅值越大,波长越小,油膜压力越高;随着幅值的增加,在啮合大部分区域,中心油膜值变大,而在啮合的开始和结束阶段的膜厚值要略低于光滑解,波长变化对中心膜厚基本无影响;随着幅值和波长的增加,最小油膜值相应增大,有利于润滑状况的改善。     

大直径渐开线斜齿轮修整数控加工技术

利用成形法磨齿高精度、高效率的优点,结合砂轮在线修整技术,提出一种具体的针对硬齿面大直径渐开线斜齿轮的数控加工技术,并对采用此加工技术磨削成形的渐开线斜齿轮精度进行测量与分析。精度测量结果表明,采用此方法加工的渐开线斜齿轮精度可达到4级。     

渐开线直齿圆柱齿轮非牛顿瞬态弹流润滑分析

齿轮的润滑设计都是应用理想牛顿流体的结果,但实际上,在中、轻载荷下Ree Eyring流体更符合实际。因 此研究齿轮在非牛顿润滑下的瞬态弹流机理,对于指导齿轮润滑问题的设计更具有工程实际价值。本文应用数值 稳定性好、收敛速度快和计算精度高的多重网格算法,得到了用Ree Eyring流体润滑的齿轮瞬态弹流问题的完全数 值解。     

风力发电机组增速箱斜齿内啮合齿轮副接触强度分析

因强度不足而使齿轮磨损失效是风力发电机组增速箱中渐开线斜齿内齿轮啮合传动中常见的问题。遵循接触疲劳强度有限元分析基本流程,利用Pro/E建立斜齿内齿轮的三维立体模型并导入ANSYS分析软件中。通过对齿轮对进行接触非线性有限元分析,获得接触应力云图并判断斜齿内齿轮啮合瞬间最大应力发生的轮齿部位,确定最大应力值,并与传统齿轮强度计算方法计算出的结果进行比较,为齿轮的设计提供了理论依据,为日后风机的设计奠定坚实的基础。     

The Slow-Speed Wear Behavior of Case-Carburized Gears Lubricated with NLGI 00 Grease under Boundary Lubrication Conditions

NLGI 00 greases are often used to lubricate gears running at low pitch line velocities, such as, for example, in large open gear drives. At low pitch line velocities, sliding wear, which under these operating conditions is referred to as slow speed wear, is often the limiting factor to gear lifetime. A thorough knowledge of the effect of different grease components on the wear behavior is therefore important when selecting a grease to effectively reduce gear wear in a given gear drive. In order to systematically investigate and analyze the influence of different grease components on the slow-speed wear behavior of case-carburized gears, systematic gear tests using the Gear Research Center's (FZG) back-to-back gear test rig were conducted. Primarily, the focus of the experimental investigations is on the influence of the base oil viscosity and type, the additive type, and also the type of soap thickener on the gear wear behavior at low pitch line velocities. To experimentally determine the influence of these different grease components on the wear behavior of case-carburized gears, a modified, more stringent wear test, based on the standard DGMK slow-speed wear test for gear oils, was developed. Different NLGI 00 greases with base oil viscosities between ν₄₀ = 70 and 1,200 mm²/s were investigated.

Base oil type and base oil viscosity were shown to have only a minor effect on the wear behavior under boundary lubrication conditions. On the other hand, the thickener type and especially the additive type play an important role in determining the wear behavior.     

A Mixed Flow Model for Lubrication with Emulsions

An oil-in-water emulsion in the inlet zone of a concentrated contact is modeled by treating the oil particles as flattened cylinders surrounded by water. In an independent flow model, the oil and water flows are coupled only through the pressure gradient. However, the model leads to anomalous behavior with regard to the flow of water. To overcome this problem, corrections to the pressure gradients due to interactions between the oil and water were derived. Both models showed that the emulsion became concentrated because the higher viscosity oil was preferentially drawn into the conjunction. The net effect was similar to an inlet starved of oil. The inlet film thickness predicted by the interactive theory was in good agreement with Dow's experimental measurements for an EHL contact.     

Numerical Simulation of an Oil Particle in Emulsion Lubrication

The analogy of lateral particle migration in shear flows has been used to investigate the entrainment of oil particles in the inlet region where a Poiseuille flow is assumed. Previous researchers have studied the particle segregation positions and the particle size effect through two-dimensional simulations. In this paper, both two-dimensional and three-dimensional simulations were conducted. The two-dimensional analysis showed that there are two stable off-center segregation positions and one neutrally stable center segregation position for the small particles, while only one stable center segregation position was found for the large particles. The results are similar in three-dimensional simulations except that the center segregation position is more stable than in the two-dimensional case. It should be noted that all the segregation positions are within the backflow region, which means all the oil particles will be rejected from the contact region if the interparticle collisions are ignored. This is supported by experimental observations.