弹性接触问题的快速算法及其在圆锥滚子接触应力分析中的应用

介绍了一种求解弹性接触问题的快速直接迭代算法,并运用此方法对圆锥滚子的接触应力进行了求解,得到了不同载荷下圆锥滚子中心平面的接触应力分布。     

空心圆锥滚子轴承接触特性分析

圆锥滚子轴承对于重载旋转机械的静动态性能有着重要的影响,空心滚子轴承正在逐渐被用于重要的工程实际中。基于Hertz接触理论和有限元方法,运用ANSYS分别建立了实心和空心圆锥滚子轴承的单滚子-套圈等效三维仿真模型,对比分析不同空心率和载荷等参数对实心和空心圆锥滚子轴承的弹性变形和接触应力等的影响规律,运用理论计算值验证了圆锥滚子轴承的接触应力值。分析结果为圆锥滚子轴承的优化设计和工程应用提供了参考依据。     

基于有限元法的推力圆锥滚子轴承动态接触分析

为了用推力圆锥滚子轴承代替推力圆柱滚子轴承,并应用于盾构机主轴承,根据接触力学理论,用有限元方法对应用于盾构机主轴承的推力圆锥滚子轴承进行了静态和动态接触分析,分析了套圈和滚动体的接触力、接触应力、速度和摩擦损耗等。针对轴承的特点和应用工况,重点研究了滚子和动圈的速度、接触力和接触应力,滚子和套圈挡边之间存在的滑动摩擦。研究结果表明:滚子与套圈接触应力在滚子两端存在由"边缘效应"引起应力集中;轴承的摩擦损耗主要来自于滚子和套圈挡边之间存在的滑动摩擦,并计算出了相应的摩擦损耗量;为推力圆锥滚子轴承应用于盾构机主轴承提供了研究基础和参考。     

垂直轴风机圆锥滚子轴承有限元分析

基于有限元法在接触问题中的应用,对垂直轴风机顶部双列圆锥滚子轴承进行非线性分析.以轴承外圈的内表面和内圈的外表面为目标面,以滚子为接触面创建接触对。得到轴承Mises应力趋势及接触应力的变化规律,最大应力值出现在距外载最近的滚子上。对最大承载滚子环向接触应力的路径分析表明,应力分布曲线呈抛物线状,符合赫兹弹性体接触理论的分布规律。     

轴向游隙对圆锥滚子轴承应力分布的影响

针对轴向游隙对圆锥滚子轴承接触应力及其应力区域的变化情况的影响,基于ABAQUS建立了圆锥滚子轴承的有限元模型,计算了圆锥滚子轴承在径向载荷作用下最大受力滚子滚道母线上的应力分布值,并与基于Hertz理论的切片法做出对比,两者的计算结果具有较好的一致性.在整体分析的基础之上,调整圆锥滚子轴承的正负轴向游隙,分析了在轴向游隙变化的情况下圆锥滚子轴承最大应力和接触区域的变化,结果显示圆锥滚子轴承的最大接触应力会在较小的负游隙的情况下出现最小值,从而为下一步研究圆锥滚子轴承的疲劳寿命和结构优化提供依据.     

圆锥滚子轴承凸度设计

利用仿真软件及有限元分析，以JRM3939/JRM3968XD轴承为例，对圆锥滚子轴承滚子和滚道的凸度进行设计，选定合适的滚子素线，确定滚子与滚道的接触状态及凸度匹配关系，并计算接触应力，为轴承的改进设计提供依据。     

轻窄系列圆锥滚子轴承滚子球基面与大挡边的接触关系分析

分析了圆锥滚子轴承球基面与挡边的接触关系,根据理论设计及实际加工能力分析L860049/L860010圆锥滚子轴承使用过程中可能出现滚子与挡边磨损及失效。鉴于此,提出改进轴承内圈大挡边倾角的改进措施,通过理论分析得到最优解。并分析了3种不同接触状态下球基面与挡边的接触应力,采用改进挡边倾角后的轴承挡边接触应力减小,说明可采用改进挡边倾角的措施改善挡边与球基面的接触状态。     

滚子凸度偏移对圆锥滚子轴承接触应力的影响

滚子的凸度偏移对圆锥滚子轴承的寿命有显著影响。通过有限元分析,讨论了圆锥滚子轴承在一定载荷条件下,滚子凸度中心分别向两端偏移时,滚子与轴承内外圈滚道的接触应力变化情况。结果表明:圆锥滚子凸度中心可向滚子大端偏移一定范围,若超出该范围,滚子两端会出现严重的应力差值,使轴承提前失效;且滚子的凸度中心不宜向滚子小端偏移。为提高轴承的接触疲劳寿命,需确定所允许滚子凸度偏移量。     

基于多体动力学的齿轮箱圆锥滚子轴承温度场分析

为研究齿轮箱圆锥滚子轴承在不同实际运行工况下的温度分布,对圆锥滚子轴承进行热分析并建立其有限元模型;采用ADAMS对圆锥滚子进行动力学分析,得到滚子在不同转速下的接触正压力和摩擦力,将结果导入ANSYS进行静力学分析后得到滚子的平均接触应力,在此基础上求得摩擦热流量,进而获得轴承的稳态温度场,并通过试验验证了模型的正确性。结果表明,随着转速的增加,轴承温度不断升高;轴承滚动体与内圈接触时的温度高于与外圈接触时的温度,最大值出现在滚子与轴承内圈的接触处。     

滚子凸度偏移对圆锥滚子轴承接触应力的影响北大核心

滚子的凸度偏移对圆锥滚子轴承的寿命有显著影响。通过有限元分析,讨论了圆锥滚子轴承在一定载荷条件下,滚子凸度中心分别向两端偏移时,滚子与轴承内外圈滚道的接触应力变化情况。结果表明:圆锥滚子凸度中心可向滚子大端偏移一定范围,若超出该范围,滚子两端会出现严重的应力差值,使轴承提前失效;且滚子的凸度中心不宜向滚子小端偏移。为提高轴承的接触疲劳寿命,需确定所允许滚子凸度偏移量。     

Macroscopic and microscopic changes in the surface layers of annealed and case-hardened steel rollers due to rolling contact

Measurements of the residual stress and observations of the microstructure at the surface and in the subsurface of rollers were performed during rolling contact fatigue tests of annealed 0.45% carbon steel and case-hardened nickel-chromium steel rollers. Compressive residual stresses in annealed rollers were induced by the rolling contact. With case-hardened rollers they were induced by heat treatment prior to the rolling contact fatigue tests. After the rolling contact fatigue tests the compressive residual stresses on the surface of the annealed rollers and in the subsurface of the case-hardened rollers relaxed; a characteristic substructure was formed by the stress cycles, which caused surface failure. It was confirmed that the microcracks leading to surface failure initiate on the surfaces of annealed rollers and in the subsurface of case-hardened rollers.     

Effect of hardness difference on the surface durability and surface failure of steel rollers

Experiments with pairs of rollers of different hardnesses designed to assess the effect of hardness difference on surface durability and surface failure are described. Sliding-rolling contact fatigue tests were performed with combinations of thermally refined, through-hardened and induction-hardened 0.45% C steel rollers. The mode of failure is discussed in relation to the hardness difference between the rollers and the presence of residual stresses. The effect of hardness on the modulus of elasticity was also examined. An empirical equation was devised to describe the relationship between the rolling contact fatigue limit under hertzian stress and the surface hardness.     

Relative fatigue life estimation of cylindrical hollow rollers in general pure rolling contact

Solid and hollow cylindrical rollers in pure rolling contact have been modelled. The two rollers are subjected to a combined normal and tangential loading. The tangential loading is one‐third of the normal loading value. The finite element package, ABAQUS, is used to study the stress distribution and the resulting deformations in the bodies of the rollers. Then the Ioannides–Harris fatigue life model for rolling bearings is applied on the ABAQUS numerical results to investigate the fatigue life of the solid and hollow rollers. Using the fatigue life of the solid rollers as the reference fatigue life, the relative fatigue lives of hollow rollers are determined. Four main different hollowness percentages are been studied: 20, 40, 60 and 80%. The hollowness percentage is the ratio of the diameter of the hole to the outer diameter of the cylinder. For each of those hollowness percentages, two cases are studied – when the two rollers in contact are hollow and when one hollow roller is in contact with a solid roller. This study includes two main models: Model 1, where the two cylindrical rollers in contact are of the same size, and Model 2, where the two rollers in contact are not of the same size. The estimated relative fatigue lives of hollow rollers showed a great improvement of the fatigue life compared with solid rollers under the same loading conditions. This was a result of the redistribution of stresses in the contact zone in the case of hollow rollers. Redistribution of stresses over a larger volume of the roller body decreased the peak stress and reduced the volume under risk. Increasing the hollowness percentage from 20 to 60% increased the flexibility of the roller, and better stress distribution was achieved, which resulted in improving the fatigue life. Although 80% of hollowness rollers have more flexibility than 60% of hollowness rollers, the bending stresses (σ_b) on the inner surface of the rollers tend to decrease the fatigue life. Copyright © 2007 John Wiley & Sons, Ltd.     

圆柱滚子凸度设计应用

分析了我国圆柱滚子轴承使用寿命比国外发达国家低的主要原因之一是滚子凸度设计应用问题,讨论了滚子凸型对接触压力分布的影响,指出滚子凸度的设计应用必须避免接触压力的奇异分布,并减小压力集中问题,通过理论分析和寿命对比试验得出:对数母线凸型是滚子凸度设计优先选用的凸型.     

Effect of Surface Pattern on Stribeck Curve

The effect of surface pattern on frictional characteristics of lubricated contact is studied. An algorithm based on the load-sharing concept is developed which assumes that the total transmitted load is carried by the asperities as well as the fluid film. Surface roughness for specified values of surface pattern number is generated assuming a Gaussian height distribution and Stribeck-type curves are obtained for isotropic, transverse, and longitudinal surfaces. The predictions of the model are verified by comparing published results on non-conformal contact of rollers and also a heavily loaded, conformal pin-bushing assembly. The results reveal that surfaces with transverse pattern generate larger friction than those with longitudinal surfaces. Transverse surfaces perform a higher film-forming capacity compared to isotropic and longitudinal surfaces.     

Experimental Study of the Smoothing Effect of a Ceramic Rolling Element on a Bearing Raceway in Contaminated Lubrication

The effects of steel and ceramic rolling elements on protrusions from the raceway of a bearing were experimentally investigated. Such protrusions, which are normally caused by solid contaminants in the lubricating oil, create stress concentrations and lead to a reduction in the rolling contact fatigue life of the bearing. To compare the over-rolling effects of steel and ceramic rollers, experiments with steel discs with artificial dents on the surfaces were performed using a modified twin-disc machine. The results show that ceramic rollers can reduce the height of the protruded edge of an artificial dent more than steel rollers, which means that they are more effective in smoothing a damaged surface. The stresses at the contact were calculated by finite element analysis based on the deformed profile of the dented surface. The reduction in the stress level due to the smoothing effect of ceramic rollers is greater than that of steel rollers. According to the Lundberg–Palmgren bearing fatigue model, that smoothing ensures a significantly longer rolling contact fatigue life for a bearing. To put the idea into practice, a rolling ball bearing with two of its nine steel balls replaced with silicon nitride balls (referred to as a “partial hybrid bearing”) was run, together with a full steel bearing of the same model, on a bearing tester in a highly contaminated lubrication condition. The results show that the partial hybrid bearing suffers from less damage in terms of wear. The post-experiment examination of the damaged surface of the bearing raceway found that the surface of the partial hybrid bearing was smoother than that of the full steel bearing. This reveals the smoothing effect of the rolling ceramic element on the contaminant-damaged bearing surface.     

Fatigue life investigation of solid and hollow rollers under pure normal loading

Two solid and hollow cylindrical rollers in pure rolling contact subjected to pure normal loading have been modelled. Using a finite element package called ABAQUS, the stress and strain distributions in the two rollers in contact have been determined. The relative fatigue life of the hollow rollers compared to solid rollers has been investigated using the fatigue life model for rolling bearings developed by Ioannides and Harris. Different hollowness percentages have been studied: 20, 40, 60 and 80%. The hollowness percentage is the ratio of the diameter of the hole to the outer diameter of the cylinder. Both cases were studied – when the two rollers in contact are hollow and when only one of them is hollow while the other one is solid. Making the rollers hollow will result in redistribution of stresses over a larger volume in the contact zone due to the flexibility of the hollow rollers. That decreases the peak stress in the contact zone of the hollow cylinder when compared to the solid cylinder. Hollow cylinders have more flexibility when subjected to normal loading. And so, the stresses are redistributed so that the fatigue life is improved. The best stress redistribution and so fatigue life improvements have been found when both cylinders have around 60% hollowness. Copyright © 2007 John Wiley & Sons, Ltd.     

大型回转窑支承系统的力学行为分析

对操作工况下大型回转窑支承系统的力学行为规律进行理论分析和接触非线性有限元仿真.根据轮带结构和运行特点,解析导出轮带内壁受简体的压力分布公式,修正了长期以来前人轮带压力公式的不妥之处.基于Ansys及其APDL( Ansys parametric design language)编程,实现对支承系统的多体接触模型在分布压力、摩擦转矩和预紧配合作用下的复杂加载及其边界非线性有限元模拟,获得回转窑支承系统的变形与应力分布规律.结果表明,轮带与托轮之间是循环挤压过程;每回转一周,轮带内外表面的等效应力经历五次脉冲循环,在与托轮接触处的峰值应力达最大.托轮外表面也存在较高接触应力.循环应力集中是使轮带与托轮发生表面疲劳失效的根本原因.过盈配合与支承载荷的双重作用,导致轮孔在与轮轴的配合端面成为托轮强度的最薄弱部位,可解释轮孔开裂或喇叭口失效现象.摩擦转矩使载荷偏置,导致支承系统应力分布非对称,故左右对称模型只适用于停工状态,对操作工况是不准确的.这些认识对回转窑支承系统的设计、检修和窑线调整具有参考价值.     

三排柱式回转支承非理想Hertz接触特性分析

传统方法对三排柱式回转支承的滚柱与滚道间的接触分析都是基于Hertz接触理论,然而滚柱与滚道的实际接触超出了Hertz接触理论的范围。针对该问题,重点研究了滚柱与滚道的非理想Hertz接触特性,得出了接触变形及接触应力沿滚柱轴向的变化规律。结合McEwen关于圆柱体法向接触理论,推导了滚柱与滚道接触区内部的应力场各应力分量解析表达式,并讨论了滚道失效与应力之间的关联。最后,建立了滚柱与滚道接触的3D有限元模型,仿真结果表明,接触区的应力分布与解析解基本吻合,结论可为三排柱式回转支承的设计与制造提供参考。     

考虑轧辊非均质特性的辊间接触应力分布规律研究

考虑轧辊表面淬硬层与其心部金属材料组织性能的差别，采用非线性有限元方法对四辊轧机的工作辊与支撑辊间接触应力及辊内剪应力分布进行模拟，并将模拟结果与传统强度校核方法进行了对比分析，研究了轧辊淬硬层厚度对辊间接触应力的影响规律。该项研究对于深入分析轧辊的失效行为具有重要的意义，为制定准确、可靠的轧辊强度校核判据提供了新的思路。