5自由度角接触球轴承的静态特性分析

基于Demul(Author's abbreviation)理论和弹性赫兹接触理论,考虑滚珠与滚道之间的弹性接触以及滚珠与外载荷对轴承内圈的作用力,建立5自由度角接触球轴承的静态分析模型.首先利用该模型求解结果与已知文献结果相对比,验证本文模型的准确性、稳定性和通用性.接着研究外载荷(轴向力、径向力和力矩)对轴承静态接...     

保持架兜孔形状对高速角接触球轴承保持架动态性能的影响分析

分别建立了方柱形、圆柱形和球形兜孔保持架的角接触球轴承动力学数值仿真模型,试验结果验证了模型的准确性。对三种不同兜孔形状的保持架在不同间隙比下进行了分析,结果表明：球形兜孔保持架运动稳定性显著优于方柱形和圆柱形兜孔保持架,而在间隙比小于1时,圆柱形兜孔保持架运动稳定性优于方形保持架,反之则方柱形保持架更稳定;球形兜孔保持架的运动由球引导,方柱形和圆柱形兜孔保持架则由套圈引导;随着间隙比的增大,保持架的轴向摆动范围逐渐增大,且方柱形、圆柱形和球形兜孔保持架的轴向摆动范围依次减小;保持架的磨损率与其运动稳定性呈负相关,且球形兜孔保持架的磨损率高于其他两种保持架。     

角接触球轴承的动态参数建模与试验研究

针对角接触球轴承动态刚度和阻尼特性分析的问题,建立了考虑基础响应的单自由度动态参数测试力学模型;搭建了轴承动态参数识别试验装置,测试及分析了不同的载荷条件对轴承径向和轴向动态刚度及阻尼的影响。试验结果表明:随着轴向载荷增大,轴向刚度、径向刚度逐渐增大,轴向阻尼、径向阻尼先减小后增大;随着径向载荷增大,轴向刚度、径向刚度逐渐增大,轴向阻尼、径向阻尼先增大后减小再增大。     

多层圆柱结构接触预紧力失效分析

多层圆柱结构的接触预紧问题,涉及到几何非线性和材料非线性以及接触面上摩擦力的影响。当材料间的刚度差别较大时,刚度低的材料呈现大变形特征,加大了几何非线性的程度。结构内部的预紧力的大小和分布与结构的整体刚度、结合部位的局部刚度、过盈配合间隙、接触面积等因素有关。本文对三层壳体在集中力作用下的应力和变形状态进行了数值分析。在模型建立中,接触面采用直接约束模型,摩擦力的模拟选用库仑摩擦模型,在施加预紧力时,采用了虚拟温度方法。根据数值计算结果,得到预紧力失效载荷与外壳厚度、垫块厚度和宽度、过盈配合间隙等参数的非线性关系。     

轴电流损伤球轴承的载荷分布和刚度变化分析EI北大核心CSCD

基于轴电流损伤凹坑的表面形貌,提出故障表征模型,对损伤后角接触球轴承的载荷分布和刚度变化进行研究。首先,建立了考虑弹性接触和滚动体与滚道间相互作用力的角接触球轴承分析模型,并验证模型的准确性;其次,提出了具有不同长度、宽度、深度的轴电流外滚道损伤凹坑的故障模型及分段函数表达式;最后,利用该故障模型研究了具有不同大小和形状的轴电流损伤凹坑对轴承载荷分布和刚度变化的影响。结果表明:滚动体从滚入到滚出轴电流损伤凹坑过程中,将释放一定量变形,导致损伤区域轴承承载力部分或全部丧失;随着轴电流损伤凹坑变大,轴承刚度变化更大、更迅速。     

计及套圈变形的电主轴角接触球轴承动刚度分析

针对高速电主轴结构特点,应用弹性力学和滚动轴承动力学理论,建立考虑内圈弯曲变形影响的角接触球轴承动刚度分析模型,探讨不同工况下内圈的径向挠度及其对轴承动刚度的影响,最后在12MD60Y6型号电主轴上进行轴承动刚度测试。理论和实验结果表明,内圈径向挠度和轴承的轴向载荷成正比、与转速成反比,在重载条件下其值不容忽视。考虑内圈径向挠度的轴承动刚度计算结果更接近实验结果。     

四列角接触球轴承振动特性研究

基于滚动轴承动力学理论,建立了四列角接触球轴承的动力学分析模型,并以某型号四列角接触球轴承为例,对不同结构参数与工况参数下的轴承振动特性进行理论分析。结果表明:对于四列角接触球轴承,根据使用工况选择大、小球列不同的内、外沟曲率半径系数与初始接触角更有利于轴承的减振降噪;对轴承施加一定的轴向预紧量可有效减小轴承振动;存在较为合理的轴向载荷、倾覆力矩及内圈转速范围使四列角接触球轴承在使用时的振动较小。     

基于空间轴承寿命预测的预紧力优化分析

以航天机构中的精密轴系为研究对象,构建了空间轴承寿命预测的数学模型,提出适宜于固体润滑轴承初始预紧力优化的方法,为其预紧力的设计和选择提供理论指导。基于滚动轴承的运动学、拟静力学和Archard磨损模型,综合考虑支撑刚度和润滑膜抗压极限强度要求,确定了预紧力的许用范围。以使用寿命最长为优化目标,优化了空间轴承71807C的初始预紧力。研究结果表明：空间轴承初始预紧力的选择范围为70 N~200 N;在磨损过程中,磨损深度和残余预紧力相互影响、相互作用;基于使用寿命最长的优化目标,优化得到156 N的初始预紧力为精密轴系组件的最优预紧力,并探究了不同预紧力下空间轴承的失效机理。     

预紧力作用下的薄壁结构屈曲稳定性分析

本文以某弹性加载系统中的薄壁结构为分析对象,通过理论分析及有限元仿真相结合的方式计算薄壁结构受压状态下的屈曲失稳临界载荷,有限元仿真结果与理论解析计算基本一致。在屈曲分析的基础上计算薄壁结构两侧的最小预紧力,通过有限元仿真进一步验证了预紧力对屈曲稳定性的影响。仿真结果表明,预紧后的薄壁结构承载能力明显提高,证明了预紧方案及最小预紧力计算方法的正确性,屈曲分析计算及预紧方案在工程应用上具有实用性及借鉴意义。     

An improved dynamic model for angular contact ball bearings under constant preload

High-speed spindles are typically installed with angular contact ball bearings. This research has established a dynamic model for angular contact ball bearings under constant preload. By analyzing the constant preload mechanism, and the gyroscopic and centripetal forces, a dynamic non-linear model for angular contact ball bearings was proposed using Hertz contact theory. The model was solved by numerical iteration to obtain the dynamic parameters of an angular contact ball bearing which included: the dynamic normal contact force and contact angle, the maximum compressive stress and axial displacement, the contact pattern, stiffnesses, etc. To validate the model, a test device was designed which was equipped with a constant preloaded bearing group. By measuring the relative displacement of the bearings’ inner and outer rings under different conditions, the accuracy of the model was proved. This modeling method provided a theoretical basis for calculating bearing thermal characteristics, fatigue life, and an optimized radius of curvature of the bearing ring channel.     

Optimal design of thrust bearing for high-speed composite air spindles

High-speed air spindles are appropriate for high-speed and high-precision machining such as small hole drilling of printed circuit board (PCB) or wafer cutting for manufacturing semiconductors. The axial load capability and stiffness of the air spindles for drilling operation are dependent on the thrust bearings. The thrust bearings are composed of an air supply part in the housing and a rotating part. Since stresses induced in the rotating part of thrust bearing by centrifugal force are very high at high-rotational speed, the axial stiffness and load capability of an air spindle should be designed considering stresses due to centrifugal force as well as the natural frequency of the rotating shaft to avoid the resonant whip vibration of the spindle. In this work, the air supply part and the rotating part of a thin thrust bearing were designed for a high-speed carbon fibre composite air spindle using the stiffness map to maximize the stiffness of the thrust bearing under axial and centrifugal forces.     

Characterization of machined surface quality and near-surface microstructure of a high speed thrust angular contact ball bearing

Bearings are one of the most important components in modern industry.Rolling contact fatigue(RCF)initiating from surface and subsurface is the major failure mode.In this paper,a typical high speed thrust angular contact ball bearing was selected,and the machined surface quality and near-surface microstruc-ture of the race-way and rolling ball were systematically characterized by using of a probe surface profiler,white light interferometer,optical microscopy(OM),scanning electron microscopy(SEM),elec-tron backscatter diffraction(EBSD)and transmission electron microscopy(TEM)combined with focused ion beam(FIB).Two kinds of precursor,probably resulting in pitting or spalling during the following rolling contact,were detected.One is the defects on the surface of either the race-way or the rolling ball,such as heavy machining marks,scratches and slag-hole.The other is nano-crystalline layer due to machining,in the outermost layer around the surface of race-way.The results may well lay foundation for our further research on RCF with the real part of such typical rolling bearings.     

The effect of contact load reduction on the fatigue life of pearlitic rail steel in lubricated rolling–sliding contact

Twin-disc contact simulation tests were carried out to investigate the influence of contact pressure variation on rail steel fatigue life. Both a colloidal suspension of molybdenum disulphide in an oil carrier fluid (similar to a commercial flange lubrication product) and water were used as lubricants. It was found that the reduction from 1500 to 900 MPa of the maximum Hertzian contact pressure (at which a molybdenum–disulphide-lubricated and previously worn rail sample was tested) extended the fatigue life of the rail steel by over five times. For water lubrication a similar reduction in contact pressure produced only a marginal increase in fatigue life. The results were found to be in qualitative agreement with the predictions of the newly developed Three Mechanism (TM) model of rolling contact fatigue, which is introduced here. This model combines the mechanisms of ratcheting and the fracture mechanics-based mechanisms of both shear stress- and tensile stress-driven, fluid-assisted, crack growth.     

The influence of surface roughness on the starved lubrication of ball bearings

Abstract

A theoretical analysis is made for starved lubrication of a rigid point contact under the influence of surface roughness. The results show that both the directional property and the standard deviation of the combined surface roughness can affect the load carrying capacity of the lubricant film as well as the friction on the solid surfaces. The combined effects of speed ratio of the contiguous surfaces and the roughness on starved lubrication are also obtained. The results show that the effects of surface roughness may improve the starvation a little, but that they are not remarkable. A regression equation is found for determining the critically starved lubricant inlet level. Such an inlet level can indicate the minimum limit of lubricant supplied quantity, and, beyond this limit, the load carrying capacity of the lubricant film will decrease sharply. In addition, experiments have been carried out to observe the starved lubrication of a ball rolling on a flat glass disc. It is shown that higher surface speeds may make the starved condition much worse.     

类金刚石薄膜对轴承钢表面机械性能和滚动接触疲劳寿命的影响

使用等离子体浸没离子注入与沉积(PIII&D)技术在轴承钢基体表面合成类金刚石(DLC)薄膜,研究了薄膜的结构和性能,结果表明,所制备的DLC薄膜主要是由金刚石键(sp3)和石墨键(sp2)组成的混合无定形碳,且sp3键含量大于10%,DLC膜层致密均匀,与基体结合良好,DLC膜具有很高的硬度和杨氏模量,分别达到40 GPa和430 GPa;其最低摩擦系数由基体的0.87下降到0.2,被处理薄膜试件在90%置信区间下的L10、L50、La和平均寿命L较基体分别延长了10.1倍、4.2倍、3.5倍和3.4倍,PIII&D轴承钢滚动接触疲劳寿命的分散性得到了显著改善.     

Exploring the ultrahigh rolling contact fatigue life of M50 bearing steel by adjusting the cryogenic sequence

The influence of different cryogenic sequences on the rolling contact fatigue(RCF)life of M50-bearing steel has been studied.The results show that direct cryogenic treatment after quenching can effectively improve RCF life.The L10 life is strikingly 5 times longer than that with cryogenic treatment after tem-pering.This is caused by the distinct lattice construction of martensite and the transformation of retained austenite.More secondary nanocarbides and fine twins are formed via cryogenic treatment before tem-pering compared with cryogenic treatment after tempering.The improvement in the RCF life of the steel is attributed to the joint effects of the secondary nanocarbides and twin boundaries with a width of 5-13 nm,which delays significantly crack initiation and propagation.This study highlights a common method to improve the service life of high-carbon and high-alloy steels by adjusting the cryogenic se-quence.     

On the prediction of the fatigue life of thin-walled structures based on a statistical model

We present experimental results of fatigue tests of AMg6 aluminum alloy model specimens-plates with a single notch, subjected to fully reversed and asymmetric cyclic axial loading. The experimentally determined lives of model specimens are used as the results of the base experiment for predicting the fatigue strength characteristics of large-scale cylindrical shells with circumferential ring-shaped stress raisers loaded by axial forces of a cyclic nature. A numerical study has been performed of the statistical model adopted for predicting the fatigue life of such shells. __________ Translated from Problemy Prochnosti, No. 3, pp. 112–122, May–June, 2006.     

Wear behaviour and rolling contact fatigue life of Ti/TiN/DLC multilayer films fabricated on bearing steel by PIIID

In order to improve the friction and wear behaviours and rolling contact fatigue (RCF) life of bearing steel materials, Ti/TiN/DLC (diamond-like carbon) multilayer hard films were fabricated onto AISI52100 bearing steel surface by plasma immersion ion implantation and deposition (PIIID) technique. The micro-Raman spectroscopy analysis confirms that the surface film layer possess the characteristic of diamond-like carbon, and it is composed of a mixture of amorphous and crystalline phases, with a variable ratio of sp²/sp³ carbon bonds. Atomic force microscope (AFM) reveals that the multilayer films have extremely smooth area, excellent adhesion, high uniformity and efficiency of space filling over large areas. The nanohardness (H) and elastic modulus (E) measurement indicates that the H and E of DLC multilayer films is about 32 GPa and 410 GPa, increases by 190.9% and 86.4%. The friction and wear behaviours and RCF life of DLC multilayer films specimen have also been investigated by ball-on-disc and three-ball-rod fatigue testers. Results show that the friction coefficient against AISI52100 steel ball decreases from 0.92 to 0.25, the longest wear life increases nearly by 22 times. In addition, wear tracks of the PIIID samples as well as wear tracks of the sliding steel ball were analyzed with the help of optical microscopy and scanning electron microscopy (SEM). The L₁₀, L₅₀, L_a and mean RCF life L of treated bearing samples, in 90% confidence level, increases by 10.1, 4.2, 3.5 and 3.4 times, respectively. Compared with the bearing steel substrate, the RCF life scatter extent of Ti/TiN/DLC multilayer films sample is improved obviously.