滚动轴承寿命理论的发展

从机理上把滚动轴承寿命预测模型分为统计学寿命模型、基于断裂力学的寿命模型和经验寿命模型3大类.对目前主要的寿命预测模型进行了评述和定性分析,最后对滚动轴承寿命理论研究的发展趋势和方向进行了探讨.     

滚动轴承和滚珠丝扛中润滑油脂的外溅性

滚动轴承或直线运动轴承中的润滑油脂,可能飞溅出颗粒,粘附在液晶制品或硬盘上,导致设备失效。所以,这种设备轴承所使用的润滑油脂尽可能降低飞溅性。但低飞溅性的润滑油脂可能带来耐磨性、噪声、阻力矩等问题。因此,我们需要一种油脂,它既具有低飞溅性,又有较高的性能和使用寿命。为了开发低飞溅性的油脂,作者研究了油脂成分和飞溅性的关系。一些数据下面会提到。飞溅颗粒的多少和基油成分有很大关系,例如,润滑油脂基油是矿物油或合成碳化氢油,它们极性低,飞溅颗粒少;相反,如果是酯油,它的极性高,飞溅性也高。飞溅颗粒的多少也取决于增稠剂的类型和含量,例如浓的润滑油脂的飞溅数量少。作者证实了飞溅出来的颗粒不仅有基油颗粒,而且有细小的油脂颗粒,油脂颗粒的直径范围在０．１１ 到０．２μｍ 。     

Compression Heating and Cooling in Elastohydrodynamic Contacts

In this study, the infrared temperature mapping technique, originally developed by Sanborn and Winer (Trans ASME J Tribol 93:262–271, 1971) and extended by Spikes et al. (Tribol Lett 17(3):593–605, 2004), has been made more sensitive and used to study the temperature rise of elastohydrodynamic contacts in pure rolling. Under such conditions lubricant shear heating within the contact is considered negligible and this allows temperature changes due to lubricant compression to be investigated. Pure rolling surface temperature distributions have been obtained for contacts lubricated with a range of lubricants, included a group I, and group II mineral oil, a polyalphaolefin (group IV), the traction fluid Santotrac 50 and 5P4E, a five-ring polyphenyl-ether. Resulting maps show the temperature rise in the contact increases in the inlet due to compression heating and then decreases and in most cases becomes negative in the exit region due to the effect of decompression. Temperature changes increase with entrainment speed but in the current tests are always very small, and less than 1 °C. Contact temperature rises from compression were compared to those from sliding contacts (where a slide-roll ratio of 0.5 was applied). Here the contribution to the contact temperature from compression is shown to decrease dramatically with entrainment speed. The lubricant 5P4E is found to behave differently from other lubricants tested in that it showed a peak in temperature at the outlet. This effect becomes more pronounced with increasing speed, and has tentatively been attributed to a phase change in the exit region. Using moving heat source theory, the measured temperature distributions have been converted to maps showing rate of heat input into each surface and the latter compared with theory. Qualitative agreement between theory and experiment is found, and a more accurate theoretical comparison is the subject of ongoing study.     

滚动轴承新理论与新设计

本文对滚动轴承传统计算方法与新计算方法计算的轴承寿命进行了对比分析。结果表明，滚动轴承材料和工作条件（润滑和污染等）对其寿命有重要影响，证明材料的精化、合理的润滑和密封设计的重要性。     

Traction of Lubricated Rolling Contacts between Thin-Film Coatings and Steel

Tribological thin-film coatings can enhance the performance of mechanical components such as bearings and gears. Although a lubricant is present in most applications, the interactions of the lubricant with the coated surfaces are not always well understood. In the present study, Stribeck curves (i.e., traction coefficient vs. dimensionless film thickness λ) were generated for lubricated rolling contact between coated and uncoated surfaces. Chromium nitride, tungsten carbide–reinforced amorphous hydrocarbon, and silicon-incorporated diamond-like carbon coatings were evaluated. Compositions, hydrogen concentrations, Raman spectra, and surface energies are reported for the films. A ball-on-flat test configuration was used in 5%, 50%, and 100% slide-to-roll conditions. The test lubricant was a polyalphaolefin containing rust and oxidation inhibitor additives only. Differences in traction performance were observed for different coating types. Traction coefficients decreased at high λ with increased hydrocarbon content in the coating. Coating micro-texture and composition were believed to influence traction as λ became small.     

A Coupled Euler-Lagrange Model for More Realistic Simulation of Debris Denting in Rolling Element Bearings

Abstract

The objective of this study is to investigate the effects of the contamination of lubricants on denting in rolling element bearings. A dynamic, explicit finite element model (FEM) is developed to reproduce and analyse the elastic–plastic response of the surfaces when a spherical particle passes through a heavily loaded contact area. To cope with mesh distortion issues due to the high deformation of the debris along the process, a novel Eulerian approach is used to model the particle. A parametric study is conducted with the coupled Euler-Lagrange (CEL) model to determine the influence of the debris size, bearing loading, friction coefficient, material properties, and relative sliding between the surfaces on the indentation features. The FEM results emphasize the major role of the material properties of the three bodies on the dent geometry, pointing out that the softer surface undergoes more severe damage. In the same way, the protection of one of the surfaces by a specific heat treatment such as nitriding leads to more severe damage on the other one. The results exhibit a direct link between the particle and dent sizes. For large particles, a change in the dent geometry is observed when the deformed particle size overcomes the contact width because the particle is no longer enclosed in the contact and is therefore spread more easily. The model reproduces two important aspects of the indentation in rolling element bearings, which are the asymmetry of the dent and the residual stresses distribution, providing interesting prospects for future work on the fatigue failure caused by these defects.     

The Influence of W-DLC and CrxN Thin Film Coatings on Impact Damage between Bearing Materials

In this work, the effect of hard tribological coatings was studied in terms of mitigating impact damage between tungsten carbide spherical elements and two different types of steel substrates. The coatings included a hard, highly elastic Tungsten-incorporated diamond-like carbon (W-DLC) coating at two different thicknesses and a harder, less elastic Cr_xN coating. Impacts were created using a drop-test rig described herein and characterized in three ways: a measure of the coefficient of restitution during impact, investigation of the impact site using an optical interferometer, and fixed ion beam cross sections of select impacts for observation of subsurface damage within the coating and substrate. It was found that hard coatings on softer substrates such as 440C steel were able to mitigate surface damage up to a certain impact speed, depending on the coating, but were unable to influence the coefficient of restitution. On harder substrates like 52100 alloy steel, the coatings were found to increase the coefficient of restitution, indicating a reduction in energy loss due to plastic deformation, and to reduce damage at each tested speed. These effects and their potential influence on bearing performance are discussed in regard to impact mechanics, surface metrology, and the material properties of the coating and substrate acquired by nanoindentation.     

汽车发动机系滚动轴承润滑脂动态可靠性测试及评价

介绍了汽车发动机系滚动轴承润滑脂动态可靠性的测试及评价方法,包括SKF Emcor润滑脂动态抗腐蚀测试,FAG FE8润滑脂动态抗极压和磨损性能测试以及FAG FE9润滑脂动态润滑寿命测试,对正确选用润滑脂以及汽车发动机系滚动轴承可靠度设计等提供参考.     

A New Form of Rolling Contact Damage in Grease-Lubricated,Deep-Groove Ball Bearings

A new form of rolling contact damage was discovered in the fatigue tests of series 6206 deep groove ball bearings under pure radial load with grease lubrication. The appearance of the damage reveals a few cracks at right angles to the rolling direction of the ball, along with the formation of a dent about 20 μ m deep in the raceway surface. This is found to occur only on the stationary outer ring raceway and the ball surface and is distributed widely within the load zone. Furthermore, under the raceway surface several cracks propagating into the substrate at an angle of about 60-80 degrees relative to the raceway surface are observed not only under the damage site but also in other nearby locations. Only the cracks at the damage position open up to the surface. The grease used for the test contained a lithium complex thickener with mineral oil as the base oil with a kinematic viscosity of 141 mm²/s at 40°C. On the test bearings two pure radial load levels of 9.14 and 12.13 kN were applied. In order to prevent the occurrence of seizure at each load, the speed of the inner ring of the test bearing was maintained at 1800-2500 min^{? 1} and 600-800 min^{? 1}, respectively, to keep the outer ring circumference temperature below 65°C. It is suggested that the damage is caused by metal-to-metal contacts due to lubricant starvation under grease lubrication and to a decrease in oil film thickness due to local increases in temperature.     

基于双尺度柔性原型迁移网络的空间滚动轴承寿命阶段识别

针对变工况条件下样本分布差异较大、不同寿命阶段样本数量不均衡导致现有空间滚动轴承寿命阶段识别方法的寿命阶段识别精度较低问题,提出基于双尺度柔性原型迁移网络（Dual scale flexible prototype transfer network,DSFPTN）的空间滚动轴承寿命阶段识别方法。在所提出的DSFPTN中,构造双尺度柔性域感知模块并将其嵌入特征提取器来增强特征提取器对不同领域私有特征的探索能力,提高特征提取器对空间滚动轴承源域和目标域样本特征的学习能力;设计同域泛原型学习以防止跨域样本不加区分的特征学习和不正确聚类,增加两域异类样本的区分性;构建两域原型迁移机制来获得域不变原型,实现从源域原型到目标域原型的迁移;利用加载域不变原型后的双分类器对齐两域之间的分布并计算目标域待测样本与域不变原型之间相似度完成对空间滚动轴承目标域待测样本分类,该分类方式在不同寿命阶段样本数量不均衡条件下能提高对各寿命阶段样本的识别精度。地面模拟空间环境下空间滚动轴承寿命阶段识别实例验证所提出的基于DSFPTN的寿命阶段识别方法的有效性。总之,构建双尺度柔性域感知模块、同域泛原型、两域原型迁移机制和加载域不变原型的双分类器使得DSFPTN在样本分布差异较大以及不同寿命阶段样本数量不均衡条件下,仅利用空间滚动轴承源域的非均衡有标签样本就能对目标域待测样本进行较高精度的寿命阶段识别。     

Investigating the Effect of Surface Finish on Mixed EHL in Rolling and Rolling-Sliding Contacts

Surface finish may significantly affect the lubrication performance of a tribological interface through the influence of topography on micro/nanoscale fluid flows around localized contacts at surface asperities. This paper aims to study the mixed lubrication performance of a group of engineered surfaces, including turned, isotropically finished, ground, and dimpled surfaces, under different operation conditions by means of a deterministic mixed elastohydrodynamic lubrication (EHL) model. The honed surface was used to mate with other surfaces. The results indicate that a longitudinal contact ellipse favors longitudinally oriented mating surface roughness and that a transverse contact ellipse, as well as a line contact, prefers a transversely orientated mating surface roughness for lubrication enhancement.     

安钢1780热连轧油膜轴承密封防护措施的改造及应用

随着油膜轴承在冶金、重型机械行业的广泛应用,对油膜轴承密封的研究日益深入。油膜轴承的密封状态直接关系到油膜的形成、轴承的运行、润滑油的防漏、污染的控制等方面。安钢1780热连轧油膜轴承密封防护措施经过改造应用,效果良好,对于油膜轴承密封的安装、维护、使用具有一定的指导意义。     

AR模型和SVM在机床滚动轴承故障诊断中的应用

将自回归模型(AR)和支持向量机(SVM)应用到机床滚动轴承的故障诊断中,根据滚动轴承的振动信号建立自回归模型,以自回归参数和残差的方差作为特征向量,然后建立基于支持向量机的多故障分类器,进而判断滚动轴承的故障类型.通过实例分析和与神经网络方法对比,表明该方法能有效地判别机床滚动轴承的故障类型.     

Three-Dimensional Simulation of Rolling Contact Fatigue Crack Growth in UIC60 Rails

In this article, a UIC60 rail with accurate geometry is studied by employing the finite element method. For this purpose, a three-dimensional elastic-plastic finite element model is conducted using model. In addition, the stress distribution of wheel-rail operation is acquired, and its effects on fatigue life are specified by damage mechanic methods. In the finite element model, the displacements and stress intensity factors (SIFs) are computed on the crack near the leading edge to calculate crack propagation trajectories and crack growth rate. The modified Paris model is used to estimate fatigue crack growth rates.     

有利于提高硬态切削滚动轴承疲劳寿命的残余应力临界条件

超精硬态切削在滚动轴承表面形成的残余压应力 ,经工作应力衰减后才成为影响滚动接触疲劳寿命的应力状态。基于此 ,本文在考虑特定滚动轴承使用条件的基础上 ,推导出滚动轴承采用超精硬态切削加工工艺时 ,已加工表面的残余应力需要满足的两个临界条件 ,即在接触区的每一离散点的残余应力必须与工作应力符号相同 ,且随时间变化残余应力的幅值应小于或等于工作应力幅值的两倍时 ,才有利于提高滚动轴承的使用寿命。该结论澄清了长久以来文献中所提出的残余压应力总是有利于提高工件疲劳寿命的这个似是而非的概念。     

机车滚动轴承再生选配法及专业化集中修观点

针对机车滚动轴承使用寿命浪费的问题,结合目前机务部门检修的普遍情况,提出了机车滚动轴承再生选配法及专业化集中修观点。     

独立分量分析在货车轴承故障诊断中的应用

提出基于独立分量分析的故障诊断方法,数值试验结果表明,基于独立分量分析的故障诊断方法能有效地诊断滚动轴承的外圈、内圈和滚动体的故障,而且比传统的共振解调法的性能更好。     

Service Loading of Rolling Bearings in Wind Turbine Gearboxes: X-ray Diffraction Material Response Analysis of White Etching Crack Premature Failures

Rolling bearings in wind turbine gearboxes occasionally fail prematurely due to white etching cracks. The appearance of preparatively opened fracture faces indicates damage initiation from the surface in most cases due to brittle spontaneous tensile stress–induced cracking. Under the influence of decomposition products of the penetrating lubricant, branching crack growth is subsequently driven by corrosion fatigue. The material response analysis of rolling bearings from all gearbox locations, based on X-ray diffraction residual stress measurements, reveals vibrations in service as the root cause of surface crack initiation. The occurrence of high local friction coefficients in the rolling contact is described by a tribological model. Depth profiles of the equivalent shear and normal stresses are respectively compared with the measured residual stress patterns and a relevant fracture strength. White etching crack failures are experimentally reproduced on a rolling contact fatigue test rig under increased mixed friction. Causative vibration loading is evident from material response analysis. The generation of compressive residual stresses by cold-working the surface is proven to be an effective countermeasure.     

In Situ Quantification of Oil Film Formation and Breakdown in EHD Contacts

Abstract

A measurement method using electrical impedance has been developed for simultaneous quantifications of the thickness (h) and breakdown ratio (α) of oil films in elastohydrodynamic (EHD) contacts. First, based on simplified geometrical and electrical models of EHD contacts, theoretical expressions of h and α were derived as explicit functions of the measured electrical impedance by using the Lambert function. Then, to verify the proposed measurement principle, oil film thickness measurements were conducted by using the electrical method together with the optical interferometry method in a ball-on-disc-type apparatus, which utilized the lubricated contact between a steel ball and a glass disc with a transparent conductive layer (i.e., an indium tin oxide layer). As a result, it was confirmed that the measured h-values obtained by the electrical method agreed well with those obtained by the optical method, under various test conditions with changing the entrainment speed, slide-to-roll ratio, normal load, and viscosity. Besides, it was also confirmed that the measured α-values obtained by the electrical method showed consistent correlations with the film parameter and the friction coefficient. It is hoped that the developed electrical method will be applied to practical metal-to-metal contacts (e.g., the contacts in practical ball bearings) to understand invisible behaviors of oil films in EHD contacts.     

高速列车转向架构架损伤、等效应力及寿命分布特性研究

为分析高速列车转向架构架损伤、等效应力及寿命分布特性,对构架疲劳关键测点进行动应力线路实测并对测点实测时域数据波形进行解析;基于实测应力时间历程及雨流计数法编制二维应力谱,利用Goodman等寿命方程将二维应力谱等效转换为一维应力谱;阐述线性累积损伤及非线性累积损伤模型的建立方法并对实测数据的线性累积损伤及非线性累积损伤进行了计算及对比分析;分别基于线性累积损伤理论及非线性累积损伤理论推导出各理论下的等效应力,基于实测数据对两种等效应力进行了计算及对比分析;通过结合非线性累积损伤及线性累积损伤理论计算的等效应力及不同可靠度下的材料S-N曲线计算并对比分析构架结构的疲劳寿命。研究结果表明,与非线性疲劳分析理论相比,线性疲劳分析理论对高速列车转向架构架的疲劳特性评估偏于保守。