齿轮润滑中的原位聚合膜的发展与应用

齿轮润滑中的原位聚合膜的发展与应用东北大学机械工程学院陈卓君杨文通丁津原一、前言目前齿轮传动向着体积小、重量轻、功率大方向发展，因此齿面接触应力不断增大，除高速齿轮传动外，绝大多数齿面润滑状态是边界润滑（或混合润滑），齿面间不存在完整的流体润滑膜。为...     

谐波齿轮传动轮齿润滑研究

本文通过研究谐波齿轮传动柔轮和刚轮在啮合过程中的啮合状态、齿面速度和齿间载荷分布规律,分析计算了轮齿间油膜厚度和润滑状态。结果表明,对于动力传递用谐波齿轮传动减速器,其齿轮能形成正确渐开线啮合的范围很小,在啮合过程的大部分时间内是处于尖点啮合状态。在正确啮合区内有可能形成弹流油膜,但膜厚比一般小于3;在尖点啮合区内则几乎不存在流体润滑或弹流润滑效应。因此,谐波齿轮传动中轮齿的润滑状态主要为边界润滑或混合润滑。台架试验如铁谱分析结果也表明,轮齿润滑确实为边界润滑或混合润滑。     

考虑边界膜强度的滑动摩擦副混合润滑模型研究

针对边界膜对摩擦副润滑状态的影响，提出一种能够综合反映压力及剪切速率对边界膜失效综合影响的边界膜强度模型，并基于润滑状态测试结果通过拟合获得模型参数；将该边界膜强度模型与流体动压润滑模型、粗糙表面接触模型耦合，建立考虑边界膜强度的混合润滑模型，并通过轴瓦摩擦实验机润滑测试结果对模拟结果进行验证。和现有典型混合润滑模型相比较，该混合润滑模型可以更准确地反映摩擦副的实际润滑状态以及摩擦因数变化规律。运用考虑边界膜强度的混合润滑模型分析轴瓦零件润滑状态转化特性和机制。结果表明：在存在边界润滑的混合润滑条件下，当加载力小于临界载荷，边界膜几乎未发生破裂，摩擦因数随载荷增加缓慢变大，其数值均较小；当加载力加至临界载荷，边界膜破裂，摩擦副微凸体接触区域出现干摩擦，摩擦因数出现突然增加，表明该摩擦副由边界润滑为主的混合润滑状态过渡到以干摩擦为主的润滑状态。     

圆弧齿线圆柱齿轮等温弹流润滑模型建立及分析

圆弧齿线圆柱齿轮具有承载能力高、接触强度大、传动平稳等优点,但也存在齿面磨损、点蚀、胶合等失效形式,这主要是由于润滑不良造成的,因此保证其良好的润滑性能十分关键。分析圆弧齿线圆柱齿轮的啮合接触过程,简化其接触模型,并基于弹流润滑理论建立了圆弧齿线圆柱齿轮等温弹流润滑的物理模型及数学模型。通过直接迭代法和Fortran语言编程进行数值求解,得到其油膜特性曲线,并分析比较了卷吸速度、载荷以及润滑油黏度对油膜压力和膜厚的影响。结果显示,卷吸速度是影响膜厚最重要的因素,润滑油黏度对油膜压力和膜厚都有着重要的影响,载荷的影响程度则相对较小。此外,用膜厚比判断齿轮润滑状态,在进行圆弧齿线圆柱齿轮设计时,使其尽量接近完全弹流润滑状态。     

外齿轮润滑泵无困油时齿面润滑状态的研究

外齿轮润滑泵的齿轮传动有别于常规的齿轮传动,其原因主要在于油膜存在入口压力、出口压力和载荷的与众不同.从刚性等粘度润滑理论人手,针对无困油时外齿轮润滑泵的齿面润滑分析,建立出油膜包含入口压力和出口压力的压力分布公式;据此,根据实例计算出的膜厚比,判断出齿面确实存在着流体润滑状态的可能性,这与实际情况比较符合.最后,文章总结了一些结论及指出下一步继续研究的方向.     

核电循环泵行星齿轮热弹流润滑研究

核电齿轮箱的良好润滑性能是核电循环泵可靠运行的重要保障,充分考虑齿面形貌和齿廓修形等因素对内/外啮合齿轮副的影响是准确评估其润滑特性的前提。建立典型工况下核电循环泵行星传动系统斜齿轮热弹流润滑模型,首先将斜齿轮副的啮合状态几何等效为圆锥滚子的接触问题,然后考虑斜齿轮接触变形和齿廓偏差,计算得到内/外啮合齿轮副接触区域不同位置的油膜厚度、承载压力、摩擦应力和闪温等参数。考虑齿面磨合作用,采用移动平均滤波方法对未经磨合的初始形貌进行光滑处理,分析了齿面形貌对润滑行为的影响,最后采取齿廓修形改善润滑特性。结果表明：粗糙度和齿廓修形均会对润滑特性产生明显的影响,齿面粗糙形貌会造成油膜厚度减小,进而影响其润滑特性,弱化润滑油膜的承载能力;通过齿廓修形可以改善齿轮啮合边界处的几何过渡,降低该区域的应力集中和表面温度,从而明显改善啮合线终端的润滑状态。     

低速重载齿轮齿条传动机构混合弹流润滑分析

低速重载齿轮齿条传动机构广泛应用于矿山、水利等升降系统中,但由于其工况恶劣,极易发生磨损、胶合。以三峡升船机的大模数齿轮齿条传动机构为研究对象,建立瞬态混合弹流润滑模型,分析了其啮合过程中的润滑状态,并研究转速、齿面线接触载荷以及齿面粗糙度对润滑状态的影响。结果表明:在一个啮合周期中,啮入点是低速重载齿轮齿条在啮合过程中的危险点;在低速、重载工况下,齿面线接触载荷对啮入点润滑状态几乎不产生影响,而齿轮转速与齿面粗糙度对啮入点膜厚比的影响显著;另外,粗糙度纹理方向也会影响齿面润滑状态,其中横向粗糙度纹理能够使齿面具备较大的膜厚比,改善其润滑状态。     

蜗杆传动发热及齿面摩擦与润滑研究的调查

蜗杆传动的发热和温升是制约蜗杆传动承载能力的一个关键因素。本文作为中日国际合作研究课题“环面蜗杆传动承载能力的研究”的前期工作，对蜗杆传动的发热和温升，齿面摩擦与润滑的研究状况进行了调研，提出了关于蜗杆传动发热的温升，齿面摩擦与润滑研究的课题。     

螺旋槽机械密封瞬态启动过程润滑特性

建立了螺旋槽机械密封瞬态启动过程润滑特性的计算模型，耦合求解了含流量因子、接触因子及质量守恒空化边界的雷诺方程、弹塑性粗糙峰接触方程及动力学方程，比较了不同运行工况及结构参数的润滑状态转变过程。结果表明：增速阶段流体承载力与液膜厚度不断增大，粗糙峰承载力逐渐减小至消失；相比较于流体动压润滑状态，混合摩擦状态的液膜刚度较大且振荡幅值明显，在到达脱开转速时刻有较大的轴向速度突变。受挤压效应影响，较小的启动加速度可以在低转速下进入流体润滑状态，较高的外压和较低的内压均有利于润滑状态的转变。随槽数的增加，脱开转速呈先增大后减小趋势，螺旋角与槽深的减小或槽坝比的增大均对润滑状态转变能力起促进作用。     

变卷吸速度过程对直齿圆柱齿轮热混合润滑的影响

以渐开线齿轮为研究对象,建立考虑时变效应的齿轮混合润滑模型,计算得到卷吸速度随时间变化的直齿圆柱齿轮的混合润滑数值解,并分析以不同加速度起动和制动过程对齿轮润滑油膜形状和压力的变化。结果表明:起动过程开始时,由于速度较低,整个齿轮润滑系统处于混合润滑状态,随着速度的不断增加,边界润滑效应逐渐消失,接触区也由边界润滑区进入弹流润滑区,并且加速度值越大,边界润滑就会提前结束,进入全膜润滑状态;由于速度在很短时间内变化,必须考虑时变效应,变速过程及变速过程结束后的一段时间都存在时变效应;起动和制动过程的油膜压力和膜厚变化是不可逆的。     

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.     

Squeeze film characteristics between a sphere and a rough porous flat plate with micropolar fluids

The effects of surface roughness on the squeeze film characteristics between a sphere and flat plate covered with a thin porous layer are investigated in this paper. The sphere and the plate are separated with a non‐Newtonian lubricant of a micropolar fluid. The well‐established Christensen stochastic theory of hydrodynamic lubrication of rough surfaces is used to incorporate the effects of surface roughness into the Reynolds equation. The film pressure distribution is solved and other squeeze film characteristics, such as the load‐carrying capacity,and time–height relationship, are obtained. The results indicate that lubrication by a micropolar fluid will increase the load‐carrying capacity and lengthen the squeeze film time, regardless to the surface rough and porosity of the flat plate. It is also found that excessive permeability of the porous layer causes a significant drop in the squeeze film characteristics and minimises the effect of surface roughness. For the case of limited or no permeability, the azimuthal roughness is found to increase the load‐carrying capacity and squeeze time, whereas the reverse results are obtained for the case of radial roughness.     

Effect of surface roughness on the couple-stress squeeze film between a sphere and a flat plate

In this paper, a theoretical study of the effect of surface roughness on the hydrodynamic lubrication of couple-stress squeeze film between a sphere and a flat plate is presented on the basis of Christensen's stochastic theory for hydrodynamic lubrication of rough surfaces. The modified Reynolds equation accounting for the couple stresses and the surface roughness is mathematically derived. The modified Reynolds equation is solved for the fluid film pressure and the bearing characteristics, such as the load carrying capacity and the time–height relationship, are obtained. It is found that the surface roughness considerably influences the squeeze film characteristics. The load carrying capacity and squeeze film time are found to increase for an azimuthal roughness pattern as compared to the corresponding smooth case, whereas the reverse trend is observed for a radial roughness pattern.     

Effect of Micro-Dimples on Hydrodynamic Lubrication of Textured Sinusoidal Roughness Surfaces

Surface texturing has been applied to improving the tribological performance of mechanical components for many years. Currently, the researches simulate the film pressure distribution of textured rough surfaces on the basis of the average flow model, and however the influence of roughness on the film pressure distribution could not be precisely expressed. Therefore, in order to study the hydrodynamic lubrication of the rough textured surfaces, sinusoidal waves are employed to characterize untextured surfaces. A deterministic model for hydrodynamic lubrication of microdimple textured rough surfaces is developed to predict the distribution of hydrodynamic pressure. By supplementing with the JFO cavitation boundary, the load carrying capacity of the film produced by micro-dimples and roughness is obtained. And the geometric parameters of textured rough surface are optimized to obtain the maximum hydrodynamic lubrication by specifying an optimization goal of the load carrying capacity. The effect of roughness on the hydrodynamic pressure of surface texture is significant and the load carrying capacity decreases with the increase of the roughness ratio because the roughness greatly suppresses the hydrodynamic effect of dimples. It shows that the roughness ratio of surface may be as small as possible to suppress the effect of hydrodynamic lubrication. Additionally,there are the optimum values of the micro-dimple depth and area density to maximize the load carrying capacity for any given value of the roughness ratio. The proposed approach is capable of accurately reflects the influence of roughness on the hydrodynamic pressure, and developed a deterministic model to investigate the hydrodynamic lubrication of textured surfaces.     

Behavior of lubricant fluid film in gears under dynamic conditions

This paper presents a new method for modeling the fluid film lubrication in gears, considering the actual meshing conditions and gear dynamics. The model takes into account both the elastohydrodynamic lubrication (EHL) and the dynamic load between the mating tooth pair. The EHL film is described as a fully flooded elliptical contact.The present approach is validated by means of comparison with other methods found in the literature, in which dynamic effects were neglected. The effect of the gear dynamics on the fluid film is investigated. It is shown that pressure and film thickness are strongly modified by the dynamics of the gear pair.The dependence of the dynamic gear lubrication on dimensionless parameters is investigated: a new dimensionless inertia parameter is added to the standard Moes' parameters. These parameters are useful to describe the lubrication conditions in gear pairs.     

Hydrodynamic lubrication of rough slider bearings with couple stress fluids

The combined effects of couple stresses and surface roughness on the performance characteristics of hydrodynamic lubrication of slider bearings with various film shapes, such as plane slider, exponential, secant and hyperbolic, are studied. A stochastic random variable with non-zero mean, variance and skewness is used to mathematically model the surface roughness of the slider bearing’s. The Stokes couple stress fluid model is used to characterize the rheological behavior of the lubricant with polymer additives. The modified expressions for the bearing characteristics, namely pressure, load carrying capacity, center of pressure, frictional force are obtained for the general lubrication film shape on the basis of Stokes microcontinuum theory for couple stress fluids. Results are computed numerically for various film shapes under consideration. It is observed that, for all the lubricant film shapes under consideration, the negatively skewed surface roughness increases the load carrying capacity, frictional force and temperature rise, while it reduces the coefficient of friction. On the contrary, the reverse trend is observed for positively skewed surface roughness. Further, these effects are more pronounced for the couple stress fluids.     

点接触混合润滑中两种求解模型的比较

混合润滑是典型零部件主要的润滑状态,根据表面形貌表征方式的不同,混合润滑模型一般分为统计学模型和确定性模型两类.为研究2种模型求解粗糙表面点接触混合润滑性能的差异,通过基于平均流量模型和GW模型的统计模型、基于统一Reynolds方程的确定性模型,分析并比较不同表面粗糙度、卷吸速度、载荷以及润滑油环境黏度时2种模型预测...