An analytical model to investigate skidding in rolling element bearings during acceleration

Skidding, which occurs in rolling element bearings during shaft rotational acceleration, causes wear and incipient failure. This paper presents an analytical model to investigate skidding during rolling element bearing acceleration, taking account of the contact force and friction force between the rolling elements and the races and the cage, gravity, and the centrifugal force of the rolling elements. The Hertzian contact theory is applied to calculate the non-linear contact force. The Coulomb friction law is used to calculate the friction force. All forces above are included in force equilibrium equations to derive the non-linear governing equations of the bearing during acceleration, and are solved using a fourth-order Runge-Kutta algorithm with fixed time step. The proposed model is verified by comparison to other published results and with experimental results. The proposed model can be used to investigate skidding in rolling element bearings during acceleration and the transient motion behavior of rolling elements, and it will lay the theoretical foundations for eliminating skidding in rolling element bearings.     

An Experimental and Theoretical Study of Hybrid Bearing Micropitting Performance under Reduced Lubrication

Hybrid bearings—that is, bearings with ceramic rolling elements and steel rings—are often used in applications with reduced (i.e., boundary or mixed) lubrication conditions. The mechanisms by which hybrid bearings perform significantly better than full-steel ones in these cases are so far unclear, although a number of published works have shown experimental results in which appreciable performance benefits were obtained by the use of hybrid bearings under boundary or mixed lubrication. In this article, the reduced lubrication performance of hybrid rolling contacts, versus full-steel ones, is studied in detail by means of rolling bearing fatigue experiments and a theoretical micropitting model. It is found that the large improvement in surface fatigue resistance of hybrid contacts cannot be explained solely on the basis of the unavoidable differences in some of the roughness parameters existing between the full-steel and hybrid contacts. It is also necessary to take into account a considerable reduction in the effective boundary friction coefficient of the hybrid contact. In the numerical micropitting simulations it was found that the boundary friction coefficient of a hybrid contact must be about two times lower than that for the corresponding full-steel contact, in order to be able to predict the experimental observations reasonably well. A similar ratio of the boundary friction coefficients was obtained in a number of dedicated tests, thus confirming the results of the micropitting model. The mechanisms of the strong micropitting resistance of hybrid bearings under reduced lubrication conditions are discussed in detail, shedding new light on the operational tribology and performance capabilities of bearings with rolling elements made of silicon nitride ceramics.     

Rolling element bearings absolute life prediction using modal analysis

In this paper, the authors introduce an experimental procedure for predicting the fatigue life of each individual rolling element bearing separately using vibration modal analysis. The experimental procedure was developed based on a statistical analysis. A statistical analysis was performed to find an empirical model that correlates the dynamic load capacity of rolling bearings to their dynamic characteristics (Natural frequencies and damping). These dynamic characteristics are obtained from the frequency response function of each individual bearing that results from vibration modal analysis. A modified formula to the already known Lundberg-Palmgren life formula is proposed for rolling element bearings. Given the modified formula, one can predict the fatigue life of each individual rolling element bearing based on its dynamic characteristics. The paper compares the results from the modified formula with those from Lundberg-Palmgren formula. The modified formula provides an accurate prediction for the fatigue life of each individual bearing based on its dynamic characteristics. The experimental validation of the modified formula is considered for future work. Therefore, it can be used in various applications of rolling element bearings in machinery systems.     

基于LMD能量特征的滚动轴承故障诊断方法

针对滚动轴承故障振动信号的多载波多调制特性,提出一种基于局域均值分解(local mean decomposition,简称LMD)能量特征的特征向量提取方法,并与支持向量机相结合用于滚动轴承的故障诊断。首先,采用LMD方法将复杂调制振动信号分解为若干单分量信号乘积函数(production function,简称PF);然后,对反映信号主要特征的PF基于时间轴积分,得到各PF分量能量矩并构造特征向量;最后,将其输入多分类支持向量机中,用于区分滚动轴承的故障类型与故障程度。对滚动轴承内圈故障、外圈故障及滚动体故障振动信号的分析结果表明,该方法能有效提取滚动轴承各工作状态信号的故障特征,能准确识别故障类型,同时对故障程度的判断表现出较高的识别率。     

Experimental Analysis and Modeling of the Effects of Oil–Air Lubrication Parameters on Bearings Friction Loss of High-Speed Motorized Spindle

The friction loss of an angular contact ball bearing is a key factor restricting the development of a high-speed motorized spindle. To quantitatively calculate the effects of the oil–air lubrication parameters on the friction loss of high-speed bearings, the drag resistance and the churning resistance generated by the movement of the rolling elements in the lubricant are theoretically modeled and the percentage volume of the lubricant in the bearing cavity (XCAV) is used to characterize the effects. The friction loss of bearings is tested by two novel methods: the free deceleration method and the energy-balance method. The experimental results show that the viscous resistance loss is a major component of bearing friction loss and oil–air lubrication parameters have important influence on it. A comparison of the theoretical calculations and the experimental results is used for deriving the empirical formula of XCAV with respect to the lubricant flow, gas pressure, rotating speed, and pitch diameter. The research results of this study have important significance for the measurement, prediction and reduction of the friction loss of high-speed bearings.     

基于因素分离法的脂润滑深沟球轴承摩擦研究*

滚动轴承的摩擦是在一个复杂的系统中由多种因素共同作用而产生的。为研究轴承中各类摩擦副的摩擦占总摩擦的比重,以矿山带式运输机托辊常用的6204脂润滑深沟球轴承为例,分析脂润滑深沟球轴承摩擦阻力的主要来源,将轴承摩擦分为滚动摩擦、滑动摩擦、黏性摩擦以及密封摩擦,用因素分离法分别开展同批次6204脂润滑深沟球轴承的带密封、无密封、无润滑以及微润滑条件下的摩擦实验,通过逐次剥离部分因素分析各摩擦分量对摩擦总量的影响。实验结果表明：在实验的载荷和转速条件下,密封摩擦占轴承全部摩擦的5%~18%,黏性摩擦占无密封轴承总摩擦的64%~85%;除去这些黏性摩擦之外,滑动摩擦也是滚动轴承摩擦中的重要分量。     

滚动轴承疲劳故障在线诊断的研究

通过对滚动轴承振动信号的在线监测提取出对疲劳故障敏感的参数：峭度、功率谱故障频带能量值、小波包故障频带能量值．选择足够的具有代表性的样本数据训练神经网络,用训练好的神经网络进行在线诊断,可以得出轴承发生疲劳故障的程度,再经过共振解调法诊断出轴承具体损伤的元件,实验表明本方法对滚动轴承的疲劳故障能正确诊断。该监测和诊断方法对其他设备的监测和诊断也有重要的意义。     

Incipient fault feature extraction of rolling bearings based on the MVMD and Teager energy operator

Aiming at the problems that the incipient fault of rolling bearings is difficult to recognize and the number of intrinsic mode functions (IMFs) decomposed by variational mode decomposition (VMD) must be set in advance and can not be adaptively selected, taking full advantages of the adaptive segmentation of scale spectrum and Teager energy operator (TEO) demodulation, a new method for early fault feature extraction of rolling bearings based on the modified VMD and Teager energy operator (MVMD-TEO) is proposed. Firstly, the vibration signal of rolling bearings is analyzed by adaptive scale space spectrum segmentation to obtain the spectrum segmentation support boundary, and then the number K of IMFs decomposed by VMD is adaptively determined. Secondly, the original vibration signal is adaptively decomposed into K IMFs, and the effective IMF components are extracted based on the correlation coefficient criterion. Finally, the Teager energy spectrum of the reconstructed signal of the effective IMF components is calculated by the TEO, and then the early fault features of rolling bearings are extracted to realize the fault identification and location. Comparative experiments of the proposed method and the existing fault feature extraction method based on Local Mean Decomposition and Teager energy operator (LMD-TEO) have been implemented using experimental data-sets and a measured data-set. The results of comparative experiments in three application cases show that the presented method can achieve a fairly or slightly better performance than LMD-TEO method, and the validity and feasibility of the proposed method are proved.     

Elastic Orifices for Pressurized Gas Bearings

The merit of using an elastic orifice compensator in externally pressurized gas bearings is examined. The use of an elastic orifice in a test bearing demonstrates an increase in bearing stiffness over a conventional fixed orifice when compared at a common operating point. This attribute should be welcome wherever externally pressurized bearings are used. In addition, increased bearing stiffness may allow the use of these bearings in applications formerly restricted to pressurized liquid and rolling contact bearings. Information is included to allow construction of working models of these orifices and duplication of experimental results.     

基于产品特征的自润滑关节轴承滚压技术研究

通过对轴承滚压安装工艺和质量控制的分析,建立了自润滑关节轴承滚压收口有限元模型,利用ABAQUS分析轴承外圈唇边的形成过程并进行了试验验证,结果表明:当轴承座内孔处厚度比轴承外圈厚度小0.1～0.2 mm,倒角为外圈V形槽深度的0.6～0.7时,轴承滚压收口质量最好.     

主动电磁轴承失效后转子坠落在备用轴承过程中的非线性动力学

用有限元法建立了任意个由滚动轴承组成的固定间隙备用轴承-主动电磁轴承-多盘多质量转子系统在主动电磁轴承失效前后的动力学方程,以一个多盘转子系统为例分析了主动电磁轴承失效后转子坠落在备用轴承过程中的瞬态非线性动力学特性,讨论了柔性备用轴承的支撑刚度、支撑阻尼和间隙对转子在坠落过程中动力特性的影响。结果表明采用具有较大阻尼柔性结构的备用轴承能够显著地改善转子坠落在备用轴承上的瞬态动力特性,抑制转子在坠落过程中可能出现具有较大振动和冲击力的全间隙区的涡动运动,减小转子坠落对备用轴承寿命和可靠性的影响。柔性结构备用轴承的支撑阻尼越大,支撑刚度越小,间隙越大,转子坠落后出现全间隙区涡动运动的可能性越小。     

起重机用滚动轴承有限元分析及故障检测

针对起重机用滚动轴承故障率高且难以检测的问题,首先采用Ansys软件对起重机用滚动轴承进行基于实际接触状态的有限元分析,然后采用基于小波包能量法和Hilbert变换方法对滚动轴承进行信号处理、分析以及故障检测。结果表明:滚动轴承的滚动体与内外圈接触部位存在较大应力集中,最易在此处首先发生破坏;根据轴承故障特征频率与内圈、外圈、滚动体三种故障类型所对应的频谱特征和能量谱相比较,可有效判断轴承故障类型。研究所采用的检测方法可为起重机用滚动轴承的故障预防和检测提供一定理论依据和指导作用。     

变工况下滚动轴承静电多传感器融合监测方法研究

滚动轴承是轨道车辆中最关键的部件之一,其质量好坏直接影响轨道车辆的运行.针对滚动轴承的故障监测,基于多传感器信息融合技术,采用多个静电传感器对滚动轴承进行同时监测,通过时域算法和复杂度度量算法对特征参数进行提取,并提出MWLOF检测算法.根据滚动轴承静电综合监测平台在不同工况下对滚动轴承进行监测试验,结果表明:考虑工况...     

高速滚动轴承柔性转子试验机

支承高速柔性转子的滚动轴承的寿命、可靠性及失效形式十分复杂,很难得到准确的理论分析结果。因此新研制了高速滚动轴承柔性转子试验机,可以模拟轴承的载荷、转速、润滑等工况条件,测试支承柔性转子系统的轴承性能,为高速轴承性能分析提供准确的试验数据。对支承柔性转子的滚动轴承进行了试验,验证了试验机的可靠性,发现与刚性转子系统相比,柔性转子系统振幅增大且轴心轨迹复杂,这将影响支承轴承的动力学特性。     

Plastic Yielding and Vibrations of Rolling Element Bearings

A high degree of resistance to plastic deformation at the contacts between rolling bodies and rings is required in bearings used for equipment that must be quiet running. It is shown that, within practical bearing design limits this resistance is primarily a function of material structure variables that affect the elastic limit.

Hardness, as measured by Rockwell or Diamond Pyramid methods is a primary variable, but in itself, an inadequate measure of this resistance. A test method is described giving good correlation with conditions causing plastic deformation of bearings in applications. The effects of residual stress, surface conditions and contact configuration are discussed.

It is shown that bearings with substantially improved resistance to plastic indentation are obtainable by the use of appropriate heat treatment.     

基于STAR-CCM+的高速角接触球轴承喷油润滑研究

喷油润滑系统广泛应用于高速滚动轴承,喷油润滑条件下轴承温升特性是影响轴承动态工作稳定性的重要因素。基于两相流理论,以71904C角接触球轴承为研究对象,建立全轴承模型,采用旋转坐标系描述各组件运动,分析滚动轴承在不同参数下喷油润滑的两相流与传热效率的影响规律。结果表明：随着轴承转速增加,轴承搅拌力矩也相应增加,导致轴承内部温度升高;润滑油运动黏度增加,轴承内部流场搅拌力矩增加,导致轴承温度升高;轴承喷油速度增加,内部流场温度呈现先增加后降低趋势,因此存在一个最佳喷油速度使得轴承温升最低。     

Investigation of abrasive wear in a pair of elements of rolling friction

A physical and mathematical model of abrasive wear of heavily loaded rolling and sliding elements such as gears and rolling bearings is developed on the basis of a previously proposed fatigue theory. The various mechanisms of wear, their controlling factors and the criteria for the transition from one type to another are discussed. Comparison of the theoretical results is made with experimental results and experimental results from the literature.     

滚动摩擦:一种新的人工关节设计

针对人工关节磨损颗粒导致的骨吸收、骨溶解现象以及由此引起的假体远期松动问题,基于滚动摩擦原理,提出了一种新的无聚乙烯滚动式人工关节设计思想,并以滚动式人工髋关节和滚动式人工膝关节设计为例探讨其基本设计原理。滚动式人工髋关节通过滚动轴承将原有人工半髋关节与天然髋臼之间的滑动摩擦在屈伸运动方向变为滚动摩擦,滚动式人工膝关节则通过滚动轴承将膝关节在屈伸运动方向上的滑动摩擦变为滚动摩擦,从而能有效降低人工关节运动时的摩擦阻力和假体—骨界面间的应力,降低了金属假体的磨损。滚动式人工关节假体设计由于没有采用聚乙烯作为主要的摩擦件,从而完全避免了聚乙烯磨粒及其引起的生物毒性作用,为有效降低假体的远期松动提供了新思路。     

基于CSLBP的轴承信号时频特征提取方法

针对滚动球轴承振动加速度信号特征提取问题,提出一种基于中心对称局部二值模式(center-symmetric local binary pattern,简称CSLBP)的时频特征提取方法。首先,利用广义S变换对滚动球轴承振动加速度信号进行处理,通过采用时频聚集性度量准则自适应地确定广义S变换的调整参数,从而获取时频分辨性较好的二维时频图;然后,计算二维时频图的CSLBP,提取CSLBP纹理谱描述滚动球轴承振动加速度信号的时频特征。对滚动球轴承正常、外圈故障、内圈故障和滚动体故障4种不同状态的振动加速度信号进行了研究。结果表明,CSLBP纹理谱能有效地表达滚动球轴承振动加速度信号的时频特征,与局部二值模式(local binary pattern,简称LBP)和统一模式LBP纹理谱相比,CSLBP纹理谱具有特征维数低和区分性能好的优点。