Corrosion fatigue behavior of epoxy-coated Mg-3Al-1Zn alloy in gear oil

The corrosion fatigue behavior of epoxy-coated Mg-3Al-1Zn alloy in gear oil was investigated. The corrosion and the fracture surfaces after fatigue test were analyzed by scanning electron microscopy(SEM) and the corrosion compositions were measured by energy-dispersive spectrometry(EDS). The fatigue properties and the crack initiation mechanisms of the specimens before and after epoxy coating treatment were discussed. The results indicate that the fatigue limit after epoxy coating treatment in gear oil is higher than that of the uncoated specimens. The epoxy coating is an excellent way to prevent direct contact between the Mg-3Al-1Zn alloy and surrounding environments. The mechanical properties of the epoxy coating layer are lower than that of magnesium alloy, which is the main reason for the fatigue crack initiation on the epoxy coating layer. In addition, the gear oil lubrication could lead to the flaking off of the epoxy-coated layer.

Performance Deterioration Analysis of the Used Gear Oil

In the present paper, we have investigated the tribological properties and microstructure of the used gear oil theoretically and experimentally. The deterioration process of the in-service gear lubricant oils was also discussed. The viscosity and microstructure of oils running different mileages were analyzed by viscometer and Fourier Transform Infrared Spectroscopy (FTIR), respectively. In addition, the friction and wear behaviors of the friction pair of the GCr15 steel ball and disc were investigated using a ball on disc tribometer under different mileages’ gear oils lubrication conditions. These techniques give reproducible and reliable data with which to evaluate the severity of deterioration process of oils. The objective of this work is to understand the deterioration process of gear oil and analyze the influence of deterioration on the performance and microstructure of lubricant oils used in gear box. Possible explanations of deterioration process as well as its influence on friction and wear behaviors are also discussed. The results reveals the tribological properties of used oils depended on strongly the microstructure and its deterioration process of oil.

Development of Fuel Economy Gear Oil Technology

Vehicle fuel economy will continue to increase in importance as world vehicle production grows and fuel supplies become more limited year by year.As OEMs strive to produce cars and trucks with greater fuel efficiency and extended durability,additive technology developers are increasingly being asked to contribute to these goals from the lubricant side.Axle inefficiency can account for as much as 10% of the overall losses in an automotive driveline so improvements in axle efficiency can contribute greatly to improving vehicle fuel economy.For good durability,low axle oil operating temperatures are also needed to minimize oxidative and thermal degradation of the oil,reduce deposits and sludge formation,and extend oil drain intervals.To develop gear oils that can increase axle efficiency significantly while maintaining stable operating temperatures requires rig tests that are fast,precise and reproducible.This paper documents the development of a new axle test rig and test procedures and presents test results on several gear oils.The test results show the contributions of base oil viscosity,base oil chemistry,and additive chemistry on the fuel economy and temperature of the various oils.Having a dependable tool is enabling the development of new fuel-efficient and durable gear oil technology.

A More Precise Determination of Gear Oil Viscosity at Low Temperatures

Low temperature fluidity of gear oils is an important fluid property as it directly impacts the useful life of a gear set.This paper compares low temperature fluidity measurement precision of ASTM D6821 and ASTM D2983.Both tests are identical in the way they thermally condition the sample prior to viscosity measurement.While ASTM D2983 is cited in many current specifications,ASTM D6821 offers users and formulators a more accurate estimate of gear oil low temperature fluidity.The primary benefit in using ASTM D6821 is better precision.ASTM D6821 accomplishes this by automating the steps from prior to preheat through to viscosity measurement at end of test.

EHD friction properties of ISO VG 320 gear oils with smooth and rough surfaces

The elastohydrodynamic(EHD)friction properties of seven ISO VG 320 gear oils including three polyalphaolefins(PAOs),three polyglycols(PG)and a mineral oil have been investigated in rolling/sliding conditions at six different temperatures and three roughnesses.Film thickness,Stribeck and traction curves have been generated using a ball‐on‐disc tribometer.Film thickness results are in agreement with previous work that it is primarily controlled by pressure‐viscosity coefficient and viscosity of lubricants.The results with smooth surface show that all oils experience significant shear heating leading to friction reduction at higher strain rates or lambda ratios but only PGs reach limiting friction whereas mineral oil and PAOs do not.Friction curves obtained at different temperatures and roughnesses enable simulating an extensive range of lubrication regimes and allow isothermal friction correction for shear heating.Stribeck curves with rough surfaces show an increase in friction in the lambda range of 0.5–3.5,where asperity separation varies from partial to full–indicating that roughness effects can be expected even under full film condition.This increase in friction is attributed to formation of a micro‐EHD region,and is seen only with mineral oil and PAOs whereas not with PGs.The results also highlight how EHD friction properties of different family of fluids could be influenced by roughness effects,and the possible mechanisms are discussed.

航空发动机燃油泵动静压滑动轴承润滑特性与参数影响分析

航空发动机燃油齿轮泵的滑动轴承长期工作在高温、高压和低黏介质极端工况下,极易诱发润滑失效,其润滑性能演变规律尚未完全探明。本文通过建立动静压混合润滑条件下燃油泵滑动轴承流体润滑模型,采用超声测量原理测试了燃油泵真实服役工况下的油膜厚度,验证了多个载荷条件滑动轴承润滑模型的油膜厚度计算准确性。最后,基于试验验证的润滑计算模型,研究了宽径比、偏心率和油槽位置对轴承润滑性能的影响规律。研究结果表明:计算的油膜厚度随工况变化规律与试验测点十分吻合,两者的平均计算误差为2.3%,此外,燃油泵负载增大会使得油膜的最小厚度向进口油槽处偏转,进而导致动压能力减弱,轴承在大负载工况的承载能力主要由静压提供。宽径比B/D由0.4增大至1.2时,会导致油膜温度沿周向降低1.2℃,而沿轴向升高0.5℃,偏心率增大会导致油膜厚度变小,混合润滑轴承中间截面处的动压提升0.43 MPa,设计滑动轴承的油槽位置应开在收敛楔形结构前端或者开扩楔形结构处,能提升轴承承载性能。

油润滑和干摩擦条件下微织构对齿轮啮合噪声的影响

【目的】目前利用微织构方法降低齿轮啮合噪声的研究较少,且多停留在计算机仿真以及等效试样试验层面,未见针对微织构齿轮噪声性能的理论分析和台架试验,有必要掌握油润滑和干摩擦条件下微织构对齿轮啮合噪声的影响规律。【方法】构建了齿面啮合噪声计算模型,采用激光加工技术制作微织构齿轮,搭建了齿轮啮合噪声检测平台,并在油润滑和干摩擦条件下对微织构齿轮和无织构齿轮的啮合传动噪声进行了测试。【结果】结果表明,在油润滑和干摩擦条件下,微织构均有助于降低齿轮啮合噪声;同时,初步验证了齿轮啮合噪声计算模型的有效性。

喷油润滑内齿圈外圆面红外测温及误差分析

高速重载人字齿轮箱的摩擦功率损失会转换成为温升,齿面温度测量是评价齿轮箱润滑和冷却设计的重要手段。针对某人字齿轮箱中内齿圈外圆面温度的在线实时准确测量需求,提出了一种基于红外测温仪的旋转齿轮表面温度测量方法,并分别设计搭建了相关测试试验装置。首先,分析了基于红外测温仪的旋转齿轮表面温度测量误差的影响因素;其次,通过试验对待测齿面的发射率进行标定;最后,开展了不同转速工况下的喷油润滑齿轮表面温度测量试验,并分析了吹气压力和吹气温度对红外测温误差的影响。研究结果表明:待测齿面喷涂黑色哑光漆后的标定发射率为0.96,而红外测温光路上的光学镜片会使红外测温值低2℃左右;带有空气吹扫管的红外测温仪可以在线实时测量旋转内齿圈外圆面的温度,且红外与热电偶测温值的最大相对误差不超过7%;选择合适的空气吹扫压力和吹扫温度,可以进一步减小红外测温误差。

考虑制造误差和油膜作用力的齿轮敲击动力学分析

为准确评估变速器空套齿轮受角加速度激励的敲击表现,采用集中参数法建立了模拟变速器敲击台架试验的10自由度扭转动力学模型;在包含时变啮合刚度、间隙非线性和拖曳力矩的基础上,进一步考虑齿轮制造误差和润滑油膜作用力。敲击台架试验结果表明包含楔入和挤压效应的润滑油膜作用力模型能正确反映变速器的敲击响应;数值分析结果表明润滑油膜可以减少制造误差位移激励和时变啮合刚度参数激励产生的齿面敲击,敲击强度随制造误差幅值的增加呈凹函数变化,当制造误差的幅值增加到某一数值时,齿轮副在无角加速度激励时亦产生敲击现象。润滑油温度对敲击的影响与角加速度激励有关:无角加速度激励时,低温时较低幅值的齿轮低频圆周误差通过改变油膜作用力方向产生敲击;油膜作用力产生的敲击响应频率比齿面接触的敲击响应频率更低;当存在角加速度激励时,敲击强度随温度的升高呈凸函数增加。

80W-90车辆齿轮油低温表观黏度的相关性研究

文章在不添加黏度指数改进剂的前提下,考察了基础油对80W-90车辆齿轮油低温表观黏度的影响,并开展了基础油理化指标与80W-90车辆齿轮油低温表观黏度的相关性研究,掌握了80W-90车辆齿轮油低温表观黏度的变化规律,确定了80W-90车辆齿轮油生产过程控制指标,以降低低温表观黏度的质量风险,指导精益生产。结果表明:固定主剂和降凝剂的加入量,混合基础油的黏度指数、密度与成品油低温表观黏度的相关性较高,可较好地反映80W-90车辆齿轮油的低温表观黏度大小。

基于运动法的航空发动机高速燃油齿轮泵卸荷槽设计与验证

高压、高速、高温化使得齿轮泵固有困油问题愈发严重,传统卸荷槽结构已难以满足高性能燃油泵设计要求。为此本文提出一种基于运动法的新型卸荷槽结构设计方法,通过构建困油模型并从整泵全局角度分析齿轮参数对困油各项性能的影响规律,以确定齿轮参数并为卸荷槽设计提供约束条件;其次基于齿轮运动规律和卸荷槽设计原则进行了某型燃油齿轮泵卸荷槽的设计,并进行了多个工况下新型卸荷槽和传统卸荷槽困油特性仿真对比;最后试制了样机并通过试验验证了卸荷槽设计的有效性。研究结果表明:所设计的卸荷槽与传统矩形卸荷槽相比,同工况下最大困油压力降低63.4 MPa,流量脉动率减小33.5%,空化区域更小,工作性能更优,能够显著缓解困油带来的不利影响。采用该结构卸荷槽的齿轮泵具有高的容积效率和长时抗汽蚀能力。

泵/马达困油现象充分缓解的等排量大模数方法

为了充分缓解外啮合齿轮泵/马达困油现象,在确保产品输出能力不变的等排量前提下,分析模数对困油腔内的负荷流量、泄漏流量和卸荷流量的影响,提出了一种等排量大模数的设计方法,并基于这3种流量的瞬时平衡和同齿形参数、不同模数下卸荷面积的演绎计算,计算出困油压力并由此判断出困油现象的缓解程度。结果表明,对于给定的齿轮副和工况条件,等排量下的齿宽系数反比例于模数的3次方,模数越大,困油现象越趋于缓解,且径向力越小,但齿宽系数越小;同齿形参数、不同模数下的卸荷面积等于模数的平方乘基准模数为1下的卸荷面积,从而为同齿形参数、不同模数下的卸荷面积计算,提供了极大方便;卸荷槽外通的进出口压力互为颠倒,导致泵较马达的困油现象更严重,但等排量小模数马达同样也会出现较为严重的困油现象。得出了选择最大化/较大的模数应为泵/马达的设计准则的重要结论。

高线速度齿轮副喷油冷却特性分析

齿轮线速度越高,摩擦生热现象越显著,不利于齿轮寿命和效率提升。因此,需要开展高线速度下齿轮副的喷油冷却特性分析,探究最佳的冷却参数。基于Hertz接触理论和齿轮啮合特点,求解了齿面平均接触应力、相对滑动速度和摩擦因数;根据生热理论,得到了高线速度下齿面平均热流密度;进而将齿面热流密度作为边界条件,建立了节圆线速度达120m/s的高速齿轮喷油冷却特性仿真模型;探究了喷油速度、喷油角度以及齿轮整流罩配置对齿轮冷却特性的影响规律。结果表明,提高喷油速度能在一定程度上改善齿面冷却效果;喷油夹角为60°、轴向喷油角度为+20°时,能得到更低的齿面温度;配置轴向整流罩时的齿面降温效果比配置其他整流罩时更好。

硼酸酯润滑油添加剂的设计、制备及在齿轮油中的应用研究

为了进一步提高齿轮油CKD 320的摩擦学性能,设计、制备了3种带有不同官能团的绿色环保含硼添加剂:饱和碳链的硬脂酸二乙醇酰胺硼酸酯(C18)、带有C=C双键的油酸二乙醇酰胺硼酸酯(C18∶1)和带有极性基团羟基和双键的蓖麻油酸二乙醇酰胺硼酸酯(C18∶1OH)。通过调控硼酸酯润滑油添加剂的极性,研究硼酸酯的极性对齿轮油CKD 320摩擦学性能的影响。结果表明:3种硼酸酯添加剂可以在不改变齿轮油CKD 320理化性能的情况下,提高齿轮油的减摩和抗磨性能以及承载能力,硼酸酯的极性越强,越易在摩擦表面吸附,抗磨性越高。

风电齿轮油运行状态分析

为监测并评价某风场在用国产齿轮油使用性能及8台兆瓦级风机的运行状态,对影响齿轮油劣化和齿轮箱寿命的指标:运动黏度、水分、酸值和金属元素含量进行检测,分析在用齿轮油在不同运行时期的各指标变化情况。结果表明:在5年运行期间内各风机齿轮油的运动黏度变化率最大为0.97%、最小为0.03%,未发生明显变质,仍能形成稳定油膜确保齿轮箱和风机安全运行;酸值波动和增加趋势相对较小,油品未发生明显氧化变质,对齿轮箱运行稳定性影响较小;铁和铜元素无异常增加,油品极压抗磨性良好;水分含量均在指标范围内,对风机润滑系统的润滑性能影响较小,建议仍需定期监控齿轮油的水分含量,避免过多残留水分等杂质物存在对新油造成二次污染,延长齿轮箱使用寿命。国产在用油各项关键性能指标变化均处在正常变化范围内,该国产齿轮油满足兆瓦级风电设备的润滑要求。

风机齿轮箱润滑油抗氧化性能预测模型研究

旨在建立基于红外光谱法快速测定风机齿轮箱润滑油(齿轮油)抗氧化性能的方法。基于齿轮油的红外光谱数据,依次进行样本集划分、数据预处理、特征波长选择和机器学习等数据处理,最终采用多种评价指标对组合模型的性能进行综合评估。结果表明,采用标准正态变量变换(SNV)预处理后的光谱数据所建立的偏最小二乘回归模型性能最佳;两种特征波长提取方法中,主成分分析(PCA)降维效果优于连续投影算法(SPA);三种机器学习中,BP神经网络预测效果最佳。最终得出采用SNV+PCA+BP模型预测效果最优,可以更好地快速预测风机齿轮油的抗氧化性能。

商用车超长效齿轮油应用研究

本文致力于对商用车桥箱通用型超长效齿轮油的应用性能进行研究。通过开展油品的理化性能分析、专项台架试验和道路耐久试验,监测油品关键指标衰变情况,对变速箱及驱动桥进行拆解评分,全面考察和评估油品与硬件的配套性和耐久性。结果显示,该产品展现出卓越的氧化稳定性、高效的油泥控制能力、出色的黏度保持性以及优异的齿轴保护能力,满足至少60万km换油的技术要求,且具备进一步延长的潜力。

鱼雷减速器齿轮润滑油需求流量分析

鱼雷减速器具有短时苛刻工况的工作特点,为精确计算齿轮运行时润滑油需求流量,提出一种基于热弹流润滑模型和齿面胶合理论的齿轮润滑油量计算方法,建立斜齿轮热弹流润滑模型,得到齿轮滚滑速度、齿轮齿面油膜厚度等参数,计算齿轮生热功率,基于热弹流润滑计算的齿轮固体表面温度,结合齿轮胶合临界温度,确定给定参数内润滑油最大允许温升,进一步计算出齿轮副润滑油流量。计算得到的减速器齿轮所需供油量,相比较传统机械手册计算结果,能够节约润滑油63.8%。通过试验验证,此方法更适用于短时严苛工况下减速器齿轮的润滑油需求流量计算。

新型无困油齿轮泵齿轮副型线优化与工作过程模拟

齿轮泵齿轮副的型线对齿轮泵性能影响极大。传统的渐开线型齿轮泵齿轮存在困油现象,产生局部高压,对其运行产生极大的危害。通过型线设计,来解决齿轮泵困油现象。基于曲线啮合理论,采用圆弧和高次曲线,构建一种新型双圆弧-高次曲线齿轮副,消除了齿轮泵的困油现象。进而,建立其几何模型并推导出型线方程,通过数值模拟,分析新型无困油齿轮泵的流场变化规律,并与现有齿轮泵进行对比。结果表明:新型齿轮泵消除了困油现象,型线组成简单,便于优化设计;此外,新型齿轮泵的工作性能更佳,流场更均匀。

行星轮系周转运动过程中的润滑油液分布与搅油损耗研究

为探究行星齿轮传动系统飞溅润滑行为,基于移动粒子半隐式(Moving Particle Semi-implicit,MPS)方法建立了行星轮系飞溅润滑仿真模型,并对其进行了试验验证;研究了行星轮系周转运动过程中的减速器内部油液分布特征、轮齿啮合区润滑油液粒子数量以及各旋转部件搅油损耗的变化规律。研究结果表明,行星轮系周转运动过程中,减速器内部可划分为油池区、拖拽区和贫油区3个区间;行星轮渐次通过各区间过程中,不同啮合区域内油液粒子数量以及各部件搅油损耗力矩值均呈现周期性变化规律。其中,内啮合区与外啮合区润滑油液粒子数量在行星轮运行至油池区时达到峰值,并均在进入贫油区后迅速下降至最小值;行星轮搅油损耗力矩在进入油池区后急剧上升至峰值,在进入拖拽区后持续下降直至进入贫油区后稳定在极低水平;而行星架搅油力矩在某一行星轮进入油池区域时急剧下降,在该行星轮进入拖拽区且下一行星轮未进入油池区时快速回升。在整个周转周期内,太阳轮搅油损耗较小且变化趋势较为平缓。行星轮系总的搅油损耗功率中,3个行星轮总搅油损耗功率占比约为60%,其次是行星架,太阳轮占比最少。