径向游隙对向心轴承性能的影响

1 引言滚动轴承的径向游隙对其运转性能及所在轴系的动态特性有重要的影响。径向游隙的大小直接影响球轴承的接触角和轴承内部的负荷分布,从而影响到轴承的支承刚度、轴系的振动特性、轴系上外载荷在各个轴承上的分配和轴承的疲劳寿命。本文是在对某航空发动机高速滚动轴承的拟静力学研究及其轴系振动分析中支承刚度研究的基础上,进一步研究径向游隙对滚动轴承性能的影响规律,以便于设计者在实际工作中能够找出适合轴承工况的最佳游隙,并且予以调整与控制。     

专用汽车举升机构支撑轴承滚道的载荷波动特性研究

传动系统的载荷波动是引发设备疲劳的重要因素,而疲劳失效是设备失效或损坏最为常见的失效模式;以某专用汽车举升机构传动系统为研究对象,建立传动系统主要零部件三维模型,运用有限元及振动频率检测的方法,系统分析了传动系统螺栓设计对传动系统支撑轴承滚道载荷波动特性的影响。研究结果表明:传动系统中的螺栓预紧力会改变支撑轴承滚道的接触变形,影响支撑轴承的接触载荷;在螺栓预紧力和外载荷共同作用下,支撑轴承接触载荷循环波动大,降低传动系统支持轴承疲劳寿命。增加支撑轴承套圈的壁厚、减小螺栓的预紧力、增加螺栓孔与支撑轴承之间距离等方面的优化,可以有效减小传动系统支撑轴承循环波动载荷,从而提升传动系统疲劳寿命;优化后的传动系统振动小于优化前。该研究为传动系统综合传动性能的提升、支撑轴承疲劳寿命的提高提供理论依据。     

基于润滑优化的重载牵引电动机轴承长寿命技术研究

随着机车朝着高速重载方向发展,牵引电动机轴承的载荷及冲击振动急剧增大,给轴承疲劳寿命周期带来了新挑战,在轴承服役寿命周期内轴承出现了早期疲劳剥落,导致轴承提前失效,给机车运行带来安全隐患。针对某款机车牵引电动机深沟球轴承外圈沟道面剥落失效进行了分析,失效原因主要为润滑不良导致的疲劳剥落,提出了改换极压型润滑脂的寿命优化技术方案,经过实车运行考核评估,优化方案有效提升了轴承寿命及润滑状况。     

UC205轴承早期失效的个例原因分析

在对外球面球轴承UC205进行寿命试验时,发现有一套轴承因早期疲劳剥落而失效。对该早期失效轴承进行了外观检验、材质检验、扫描电镜及能谱分析,找出了该轴承早期疲劳的主要原因是外圈内部存在氧化皮。     

航空发动机滚子轴承载荷分布分析及寿命计算

针对航空发动机主轴承的工作特点,在考虑径向载荷、工作弯矩、滚子在高速下的离心力和游隙的影响下,基于拟动力学法建立高速滚子轴承的载荷分布分析模型,得到了不同载荷参数对滚子载荷分布以及寿命的影响规律.     

联合载荷作用下交叉圆柱滚子转盘轴承的承载能力分析

建立了在径向、轴向和倾覆力矩联合载荷作用下交叉圆柱滚子转盘轴承的力学模型,该模型考虑了转盘轴承的游隙参数。采用Newton-Raphson法对力学模型进行了数值求解。计算了转盘轴承的安全系数和疲劳寿命两个承载能力指标,分析了转盘轴承游隙变化对转盘轴承内部载荷分布、安全系数和疲劳寿命的影响规律。结果表明:转盘轴承游隙的变化对转盘轴承内部的载荷分布和承载能力有着显著的影响。随着转盘轴承轴向游隙的增大,转盘轴承内部承担外部载荷的滚子数量逐渐减少,受载最大的滚子载荷也随之逐渐增大。在转盘轴承的轴向游隙从0 mm增大到0.24 mm的过程中,转盘轴承的承载能力安全系数下降了16%,疲劳寿命减小了26%。     

低噪声深沟球轴承仿真分析

在深沟球轴承动力学分析基础上,建立了低噪声深沟球轴承动态性能仿真数学模型,利用ADAMS多体动力学分析软件,开发了低噪声深沟球轴承仿真分析软件,对6205型低噪声深沟球轴承进行了仿真分析,探究了轴承径向游隙,内、外沟曲率半径系数,保持架兜孔引导间隙,保持架偏心距,轴向、径向载荷以及转速等参数对轴承振动的影响,结果表明:轴承径向游隙,内、外沟曲率半径系数对轴承本底振动有较大影响;合理的保持架兜孔形状以及兜孔半径均可减小轴承振动;施加一定的轴向载荷能够有效减小轴承振动,提高轴承寿命。     

某型发动机三支点轴承装配游隙的调整方法

某型发动机三支点轴承在发动机装配时处于盲装状态,故障发生率较高,而轴承工作状态游隙的大小对该轴承疲劳寿命及发动机的性能都有很大的影响。文中介绍在装配过程中控制、调整轴承游隙的方法,以确保轴承的使用寿命,保证发动机工作安全可靠。     

航空发动机主轴高速圆柱滚子轴承保持架柔体动力学仿真

在轴承动力学分析基础上,考虑保持架的柔性特性,采用修正的Craig-Bampton子结构模态综合法建立了航空发动机主轴高速圆柱滚子轴承保持架柔体动力学方程,利用ADAMS系统开发了圆柱滚子轴承刚柔耦合动力学仿真软件,并对保持架动态性能进行仿真,着重对轴承工况和结构参数与保持架动态特性的关系进行了研究。仿真结果表明:振动应力引起的疲劳失效多发生在保持架梁处;高速轻载工况下保持架易产生较大的打滑;径向游隙适当增大有利于降低打滑率;兜孔间隙与引导间隙比值大于1后保持架运动平稳性明显变差。最后,试验验证表明,柔性保持架动力学模型所得结果比刚性模型所得结果更接近试验结果。     

随机风作用下风力发电机齿轮传动系统动载荷计算及统计分析

针对风力发电机齿轮传动系统在随机风作用下失效率高的问题,在模拟真实风速的基础上,建立考虑外部随机风载及内部齿轮时变啮合刚度、轴承时变刚度及综合传递误差等激励因素的风力发电机齿轮传动系统齿轮-轴承耦合动力学模型,通过对动力学模型进行仿真计算,得到各齿轮副的动态啮合力和各支承轴承的动态接触力。结合有限单元法和赫兹接触理论,得到关键零部件的应力时间历程,采用雨流计数法对应力时间历程进行统计分析,得到传动系统各关键零部件承受载荷的应力谱及概率分布函数。研究结果为风力发电机齿轮传动系统的动态可靠性分析和疲劳寿命预测奠定基础。     

发动机转子-滚动轴承系统的振动性能研究

针对发动机转子 滚动轴承系统建立了有限元模型,将弹性轴段、刚性圆盘和弹性支承的动力方程集结后得到系统振动方程,分析计算了支承刚度对系统固有频率的影响。将转子不平衡惯性力和轴承支反力作为激励,求解了系统的稳定响应,得出了合理设计支承刚度和阻尼,可以改善转子系统的振动特性的结论。通过转子系统模拟实验,对该结论进行了验证。     

In Situ Growth of Graphene on Carbon Fabrics with Enhanced Mechanical and Thermal Properties for Tribological Applications of Carbon Fabric–Phenolic Composites

ABSTRACT

Though the premature failures of wind turbine gearboxes are often attributed to bearing fatigue from overloading, there is compelling evidence that wear from underloading is a significant contributor. Here we attempt to gain insight into the relative contributions of over- and underloading by assessing planet bearing reaction forces from the Gearbox Reliability Collaborative (GRC) standard gearbox within a typical utility-scale wind turbine under realistic conditions. The results demonstrate that non-torque load sharing by the planetary stage increases and decreases planet bearing reaction forces at different locations within each rotor cycle regardless of wind speed. Planet bearing reaction forces exceeded the fatigue limit at wind speeds above 12 m/s and fell below the minimum load rating at wind speeds below 7 m/s. Based on analyses of published wind spectra from 10 U.S. sites, the expected fatigue life of the planet bearings ranged from 42 to 529 years even after accounting for non-torque load sharing. At the same 10 sites, planet bearings were underloaded (below 2% of the dynamic load rating) once per rotor cycle 40–70% of the time. Underloaded bearings are susceptible to surface damage when suddenly exposed to common transient events, such as yaw, wind gusts, braking, and grid faults. The resulting surface damage can initiate premature failure via wear (e.g., micropitting) or by reducing bearing fatigue life. The results suggest that carrier bearing clearance, non-torque load sharing, and planet bearing underloading are significant contributors to the premature failures of wind turbine planet bearings.     

大功率发动机轴瓦失效研究

发动机轴瓦也称滑动轴承,主要功能为支撑及传递轴系转动。随着现在柴油机的强化指标越来越高,发动机的爆发压力已经达到了20MPa以上,曲轴传递给轴瓦的压力也随之增高,一旦润滑条件不充分,导致轴瓦与曲轴轴径之间发生金属硬接触,导致轴瓦磨损,甚至摩擦的高温导致轴瓦烧瓦、抱瓦失效。轴瓦的失效往往对发动机破坏性极大,容易导致曲轴的断裂失效,所以发动机轴瓦对发动机的正常运行极其重要,我们针对大功率发动机的轴瓦失效的问题进行了全面的失效原因分析,并根据分析结果提出了整改措施,很好的解决了轴瓦失效的问题。     

Auto-Eliminating Clearance Auxiliary Bearing Device for Active Magnetic Bearing Systems

An auto-eliminating clearance auxiliary bearing device (ACABD) for active magnetic bearings (AMBs) has recently been designed and a prototype system was tested in this study. ACABD mainly consists of a series of connected tilting supports. In this design, a ball bearing is directly mounted on a rotor as the auxiliary bearing in an AMB system. The outer race of this ball bearing is surrounded by these supports. In the open position, there exists an initial protective clearance between the outer race of the ball bearing and the tilting supports. When the bearing-mounted rotor drops on these supports due to an AMB failure, the friction between the outer race of the ball bearing and the tilting support rotates these supports to eliminate the clearance and recenter the rotor. Due to elimination of the clearance, the possibility of backward whirl of the rotor is eliminated. The movement mechanism of this device is analyzed kinematically. The rotation of these supports, elimination of the protective clearance, as well as the rotor rotating stability after the clearance elimination are discussed from the perspective of statics. Furthermore, a preliminary prototype experimental rig was developed to demonstrate the feasibility of the ACABD after AMB system failure. Experimental results show that, after the AMB system failed, the ACABD immediately eliminated the clearance between the outer race of the ball bearing and the supports and pushed the rotor center close to the initial position.     

基于中介轴承润滑性能改善的新结构研究

针对某型航空发动机中某中介轴承润滑和冷却性能较差的情况,采用计算流体动力学有限元技术对其原因进行了分析。在此基础上,提出了两种轴承润滑系统的新结构方案,并进行了润滑系统新结构的滑油流场仿真分析。研究结果表明,新结构可以在很大程度上增大润滑油的流动强度,提高润滑系统向轴承的供油量,改善中介轴承的润滑性能,为进一步的试验工作和中介轴承润滑系统的改型设计提供了分析基础。     

Lubrication Performance of Connecting-Rod and Main Bearing in Di erent Engine Operating Conditions

Only the lubrication performance at rated engine operating condition was generally analyzed in current design and research of engine connecting-rod and main bearing. However, the actual engine(especially vehicle engine) does not always operate in rated operating condition and its operating condition changes constantly. In this paper, a fourstroke four-cylinder engine is taken as the studying object, the load and lubrication of connecting-rod and main bearing in di erent operating conditions are analyzed. The load of connecting-rod bearing is calculated by the dynamic calculation method, the loads of all main bearings are calculated by the whole crankshaft beam-element finite element method, and the lubrication performance of connecting-rod and main bearings are analyzed by the dynamic method. The results show that there are major di erences in the changes and numerical value at corresponding moment of the loads and lubrication performance of connecting-rod and main bearings in an engine operating cycle in di erent engine operating conditions; the most unfavorable case of the lubrication performance of connectingrod and main bearings may not take place in the rated engine operating condition. There are also major di erences between the lubrication performance of connecting-rod bearing and that of main bearing and between the lubrication performances of main bearings one another. Therefore, it will not be reasonable that the lubrication performance of a certain connecting-rod bearing or main bearing is analyzed in the design of the engine bearing. It is necessary to analyze simultaneously the lubrication performances of all bearings in di erent engine operating conditions.     

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。     

考虑三维运动和相对滑动的滚动球轴承局部表面损伤动力学建模研究

滚动体通过局部表面损伤时轴承的运动参数及动力学响应是轴承疲劳损伤分析和故障诊断的有效输入和重要依据。基于GUPTA轴承模型构建具有局部表面损伤的滚动球轴承的完整动力学模型。该模型中每个轴承元件(滚球、内圈及外圈)具有6个自由度,并且考虑了元件之间的相对滑动和润滑牵引特性。在对局部表面损伤进行建模时,完整考虑了损伤出现后由于材料缺失而引入的额外间隙,以及损伤对赫兹接触刚度及接触载荷作用方向的影响。研究滚球在通过局部表面损伤时轴承的加速度与滚球/损伤之间冲击力的对应关系,以及轴承转速和损伤宽度对轴承振动响应的影响规律。仿真结果表明,由于考虑了相对滑动和滚球/损伤之间冲击力的影响,本模型能够对具有局部表面损伤的球轴承进行更为合理的动力学特性分析,可为滚动球轴承的疲劳损伤分析和故障定量诊断提供一定的理论依据。