静压滑环摩擦转矩的研究

本文在静压滑环简化模型的基础上，给出了变粘度下静压滑环摩擦转矩的关系式，并对比了变粘度和定粘度下的摩擦转矩随缝隙值变化的规律，最后应用实验研究验证了该关系式的正确性。     

轴向柱塞泵滑靴静压支承的设计探讨

本文介绍的轴向柱塞泵滑靴静压支承,是用柱塞中心的阻尼管构成供油节流器的静压支承。文中分析了滑靴、阻尼管和静压支承的性能以及影响油膜厚度的因素,给出了滑靴性能随半径比α变化的关系曲线及支承性能随特性值β变化的关系曲线,并针对ZB-75泵的有关参数举例说明如何利用这些关系曲线进行滑靴静压支承的设计计算。     

变粘度条件下静压支承出油液阻的研究

以静压止推轴承为例，研究了变粘度条件下静压支承的出油液阻，提出了出油液阻比影响系数的概念，得出了静压支承的出油液阻比不仅与油膜厚度的3次方成反比，而且还与出油液阻比影响系数有关的结论。利用计算机仿真在不同工况下，对出油液阻影响系数进行了对比研究，为变粘度流体特性的研究提供了一定的理论基础。     

变粘度条件下静压支承出波液阻的研究

以静压止推轴承为例，研究了变粘度条件下静压支承的出油液阻，提出了出油液阻比影响系数的概念，得到了静压支承的出油液阻比不仅与油膜厚度的3次方式反比，而且还与出油液阻比影响系数有关的结论，利用计算机仿真有不同工况下，对出流液阻影响系统数进行了对比研究，为变粘度流体特性的研究提供了一定的理论基础。     

流体静力润滑在天文望远镜上的应用

介绍了应用于天文望远镜上的静压支承型式。阐述了毛细管节流的、具有双层油膜的凹透镜式、方形四油池静压油垫系统的性能。首先简要讨论影响单油垫油膜厚度变化的各种因素,用电子计算机计算了载荷、供压、阻尼、油膜刚度与油膜厚度的关系曲线。进而探讨极轴静压油垫系统的刚度与油垫中心角θ、地理纬度φ之间的定量关系,得到了各种φ值下的最佳θ值,对极轴采用球面或柱面轴颈两种型式的支承系统作了比较。     

径向柱塞泵中滑靴摩擦副的设计分析

该文介绍了静压支承工作原理，并利用静压支承原理对新型径向柱塞泵的滑靴结构进行了设计。分析了滑靴摩擦副的油膜刚度、漏损及影响油膜厚度的因素。     

轴向柱塞泵配流副短阻尼孔效应研究

在间隙径向压力对数分布的条件下,进行了短阻尼孔型配流副静压支承的受力分析,得出了油膜厚度是工作压力、结构系数及油液粘度的函数;建立了配流副静压支承在突变载荷下的动态方程和模型,对静压支承的动态特性进行了仿真研究,仿真结果表明短阻尼孔型配流副静压支承具有较好的动态特性,且油膜厚度能在很短时间内恢复到平衡位置,具有很小的超调量.     

基于Fluent的静压支承油膜仿真计算研究

以静压支承结构为研爱对象,利用Fluent工具对整个静压支承结构进行了数值仿真,验证了静压支承油膜的形成。仿真分析的结果表明,初始尺寸的静压支承结构压力油膜能够形成,油腔部分压力场基本稳定,油膜部分压力场逐渐减小：油膜部分流速较大,固定阻尼部分流速变化较大;初始油腔的厚度值较大,会在油腔内部形成涡流;最后根据分析结果对结构尺寸作了局部优化。     

液黏传动摩擦副软启动过程承载特性研究

以刮板输送机可控启动装置液黏传动软启动过程为研究对象,考虑摩擦副表面粗糙度及工作油的离心力,基于平均流量模型求解了油膜厚度及油膜压力的变化规律。基于Greenwood-Tripp接触模型建立了摩擦副粗糙接触压力和转矩方程,利用转矩平衡原理对软启动过程中摩擦副承载特性的时变性进行了分析。结果表明：当启动时间10 s,额定输出转速45 r/min,启动过程遵循S形曲线变化时,油膜厚度按照反S形曲线逐渐减小,并趋于恒定值;油膜压力随时间先增大后减小,且沿径向的分布与启动时间密切相关;摩擦副间压力按照S形曲线增大;负载越大,启动时油膜越薄,摩擦副间压力越大。研究结果为准确地分析摩擦副热特性提供了先决条件,同时也为控制策略的制定奠定了理论基础。     

天文光学望远镜的静压油垫支承系统

目前,我国口径最大的2.16米天文光学望远镜的跟踪轴采用了五个静压油垫的支承系统。跟踪轴的微调机构亦采用了静压油垫。现把其支承的结构设计、运行性能以及跟踪轴晃动与油膜厚度变化之间的关系介绍如下。     

Starting and Steady-State Friction Torque of Grease-Lubricated Rolling Element Bearings at Low Temperatures—Part II: Correlation with Less-Complex Test Methods

Today, torque measurements are conducted in full-scale test rigs, either standardized or specially designed. This is a time-consuming approach, especially at low temperatures, and it is therefore of high priority to find some less complex test method(s) correlating with bearing friction at different temperatures. The paper deals with five possible candidate test methods to predict low temperature starting and running friction: apparent viscosity, base oil viscosity, sliding friction, base oil traction properties and yield stress. The pros and cons of these methods are discussed and empirical expressions are presented for the methods where good correlation was found.

It is stated that base oil viscosity at the temperature of interest is the best method to predict bearing friction torque at low temperature starting.     

Friction torque in grease lubricated thrust ball bearings

Thrust ball bearings lubricated with several different greases were tested on a modified Four-Ball Machine, where the Four-Ball arrangement was replaced by a bearing assembly. The friction torque and operating temperatures in a thrust ball bearing were measured during the tests. At the end of each test a grease sample was analyzed through ferrographic techniques in order to quantify and evaluate bearing wear.A rolling bearing friction torque model was used and the coefficient of friction in full film lubrication was determined for each grease, depending on the operating conditions.The experimental results obtained showed that grease formulation had a very significant influence on friction torque and operating temperature. The friction torque depends on the viscosity of the grease base oil, on its nature (mineral, ester, PAO, etc.), on the coefficient of friction in full film conditions, but also on the interaction between grease thickener and base oil, which affected contact replenishment and contact starvation, and thus influenced the friction torque.     

液黏传动可控启动过程混合摩擦转矩特性研究

为了研究矿用重型刮板输送机可控启动装置中液黏传动可控启动过程混合摩擦阶段的转矩特性，基于雷诺方程建立了油膜承载力和剪切转矩数学模型，并根据G-W模型建立了微凸峰接触转矩模型，最终以刮板输送机实现S形曲线，得到了可控启动过程中摩擦副的承载特性和转矩特性。结果表明，可控启动过程中，摩擦副间油膜厚度按反S曲线随时间增大而减小；摩擦副的承载力和转矩不断增大，其中微凸峰为总承载力和转矩的主要承担部分，并且不断增大，而油膜承载力和转矩则只占据小部分并不断减小。研究结果为可控启动装置可控启动过程转矩特性预测和控制部分设计提供了理论依据。     

液压往复密封的摩擦特性分析

基于往复式密封的弹性流体动力润滑的数学模型,对影响密封性能的因素进行了综合分析。综合考虑了形变理论、接触力学理论以及流体-固体耦合理论,采用MATLAB数值分析法,通过数学迭代计算完成最终求解。深入研究了润滑油黏度、界面摩擦系数以及密封圈的表面粗糙度对密封性能的综合影响。结果表明:随着耦合界面摩擦系数的增加,接触摩擦力都呈现出增大的趋势;总摩擦力随着粗糙度的增加呈现出抛物线式变化趋势;润滑油的黏度存在一个临界值,当润滑油黏度小于此临界值时,随着润滑油黏度的增加,总摩擦力先增加后降低;当润滑油黏度超过此临界值时,接触摩擦力呈现出单调增加的趋势;润滑油黏度和界面粗糙度的增加会导致流体泄漏的增大。     

Reduction in axle oil operating temperatures by fluids with optimized torque transfer efficiencies

Effective axle oils must efficiently transfer torque from the drive‐train to the wheels, while maintaining low axle oil operating temperatures. Previous studies have shown that fluids, which form thicker elastohydrodynamic (EHD) films and have lower EHD friction, have higher torque transfer efficiencies (TE) and lower axle oil operating temperatures (OT). In general, oils with higher viscosities form thicker films and those with lower viscosities have lower EHD friction. Therefore, optimizing oil's rheological properties to maximize TE and minimize OT is difficult. In this paper, we examine two approaches to maintaining high TE while reducing OT. One approach is to minimize boundary friction since previous studies have shown that the boundary frictional properties of oils influence OT and not TE. A second approach is to more thoroughly examine the effect of rheology on film thickness and EHD friction. Film thickness and EHD friction are related to the high temperature high shear viscosity and pressure‐viscosity coefficient of oils. We have found that oils with high pressureviscosity coefficients and low high temperature high shear viscosities will form thick films and have low EHD friction. This optimized combination of physical parameters, along with lowering the boundary friction coefficient of axle oils, results in oils with high TE and low OT. Copyright © 2006 John Wiley & Sons, Ltd.     

The Effect of Lubricant Viscosity and Composition on Engine Friction and Bearing Wear

This paper investigates the effect of lubricant composition on engine friction and connecting-rod bearing wear. Special attention has been given to polymer-thickened (VI improved) oils since these oils are characterized by shear-dependent viscosity and a simultaneous occurrence of viscous and elastic properties. The variables investigated in this study included lubricant viscosity, polymer type, and concentration.

Two sets of engine studies were conducted, one to determine engine friction, the other to measure connecting-rod bearing wear, using irradiated bearings. For Newtonian fluids, the engine friction and wear response can be predicted from classical lubrication theory—that is, (a) friction decreases with increaing viscosity until a viscosity is reached where friction is a minimum; beyond this viscosity, further increases in viscosity result in increased friction. (b) Bearing wear decreases with increasing viscosity, but as a step function, not linearly, and the transition viscosity (of the step) corresponds to the viscosity which gives a minimum engine friction.

The addition of polymeric VI improvers (non-Newtonian fluids) to mineral oil base stocks reduces engine friction and lowers bearing wear—the amount of friction and wear reduction depending on the polymer type and concentration. This paper demonstrates that polymer-thickened oils actually give better bearing wear performance than their comparable mineral oil counterparts despite the fact that they have a lower apparent viscosity at high rates of shear. In addition, it appears that temporary viscosity loss is not the sale cause of the reduced engine friction of polymer-thickened oils.     

基于正交试验的旋转轴唇形密封可靠性影响因素研究

为探讨多因素相互作用对油封可靠性的影响,以某减速器中输入轴与轴承端盖间的油封为研究对象,基于有限元软件获得不同结构参数时油封的静态压力分布曲线和影响系数矩阵,并将分析结果集成到油封的混合数值计算模型,分析并计算油侧唇角、空气侧唇角、理论接触宽度、过盈量、弹簧劲度系数、腰厚、腰长7个结构参数对油封泵送率和摩擦扭矩值的影响;将油封的7个结构参数作为变量因素,以油封泵送率和摩擦扭矩作为响应目标进行正交试验,研究各结构参数对油封密封可靠性的灵敏性。结果表明:各因素对油封泵送率敏感性影响程度由大到小依次为油侧唇角、理论接触宽度、空气侧唇角、腰厚、过盈量、腰长、弹簧劲度系数,各因素对摩擦扭矩的敏感性影响程度由大到小依次为油侧唇角、理论接触宽度、腰厚、弹簧劲度系数、过盈量、空气侧唇角、腰长,表明油侧唇角和理论接触宽度是影响油封可靠性的最主要因素。确定油封参数的最优组合,油封优化后的摩擦扭矩比优化前的更低,因而能够减少油封工作时的摩擦生热量,从而延长油封的使用寿命。     

基于旋转法的发动机润滑油黏度检测技术研究

在传统旋转法基础上,提出一种新型的旋转式黏度在线测量方法。该方法利用流体力学相关理论对转子旋转时的黏滞力矩进行分析,通过建立传感器直流电机电流和油液黏滞力矩的关系来仿真计算油液黏度。研发一种发动机润滑油黏度在线检测传感器,通过高低温试验测试传感器对润滑油黏度的响应,并对传感器进行标定。结果表明,该传感器对油液黏度变化具有较快的响应与较高的灵敏度,结构简单,稳定可靠,克服了传统黏度计测量时间长、对环境要求苛刻、尺寸较大且价格昂贵的缺点。     

Tribological effects of fullerene (C60) nanoparticles added in mineral lubricants according to its viscosity

In this study, the tribological behaviors of fullerene nanoparticles-added mineral oil were investigated as a function of viscosities (e.g., 12, 30, 55, 96 and 145 mm²/s). Extreme pressure and anti-wear properties were evaluated using a four-ball tester, respectively. The lubrication tests were performed with a disk-on-disk tester for different normal loads. Tribological properties were evaluated by measuring friction surface temperature and the friction coefficient, and interpreted in terms of the Stribeck curve. We note that the weld points of the raw- and nano-oil increased as the oil viscosity increased and weld points for all nano-oil were higher than those of raw oil. Also the wear scar diameters of the raw- and nano-oil decreased as the oil viscosity increased and wear scar diameters for all nano-oil were less than those of raw oil. Also, we have found that the difference of friction coefficient between raw oil and nano-oil was outstanding when the viscosity of raw oil was low and the normal load is high. Our results indicate that the addition of fullerene additives in lubricant was more effective when the viscosity of raw oil was low under the higher normal load conditions.