风力发电机滚动轴承多体接触有限元分析

以风力发电机圆柱滚子轴承为对象,利用有限元法对其静力学和动态特性进行分析研究,建立了滚动轴承多体接触几何及有限元力学模型,分析了不同载荷、不同滚子数目及空心度的变化对应力和变形的影响规律,最后,进行了滚动轴承的有限元模态分析。相关方法和结论为风力发电机滚动轴承的设计制造及相关接触问题的进一步研究提供了科学依据和基础数据。     

推力球轴承接触问题有限元分析

推力球轴承是被广泛应用的支承机械,用于承受转速较低的轴向载荷.它是由上下座圈、保持架和球体组成的可分离结构,分为单向推力球轴承和双向推力球轴承两种.着重分析了不同尺寸、形状的球形滚动体和橄榄球形滚动体对接触情况下的应力和变形量的影响.使用Pro/E建立实体模型,导入ANSYS进行数值模拟和计算.通过对获得的数值模拟结果和赫兹理论解进行对比,结果表明有限元分析是比较准确而且可靠的.最大接触应力和弹性趋近量取决于滚动体与滚道接触处的主曲率和、主曲率差,与滚动体形状、体积没有直接联系.     

高速客车轴箱轴承的偏载分析及轴承滚子非对称修形

通过对铁路高速客车轴箱轴承在偏载下滚动体与内外圈的接触应力和位移等所进行的有效元分析，提出了滚子非对称修形新概念。有限元分析结果表明，由于轴向载荷的影响，滚动体与内外圈的接触应力和位移等沿滚动体轴线的分布发生偏移，传统的对称修形虽然可以避免滚动体两端的边界应力集中，但无法克服“偏载效应”。为了同时避免所谓的“边缘效应”和克服“偏载效应”，必须根据偏载下滚动体与内外圈的接触应力或位移的偏移分布规律对滚子进行相应的非对称母线修形，从而使非对称修形滚子轴承有更高的可靠性和使用寿命。     

考虑滚子位置变化的圆柱滚子轴承非线性刚度特性分析

以圆柱滚子轴承为研究对象，考虑轴承运转过程中滚子周向位置分布的周期性变化，对经典圆柱滚子轴承载荷分布理论进行改进，并对由此引起的轴承刚度时变特性进行分析，同时研究圆柱滚子轴承平均刚度及平均接触滚子数随径向力的非线性变化规律。为了对改进理论算法进行验证，采用有限元接触分析方法对圆柱滚子轴承刚度及滚子接触状态进行分析。研究结果表明，改进理论算法和有限元接触法均能准确预测轴承瞬时刚度的时变特性及平均刚度随径向力的非线性变化特性，同时证明轴承平均接触滚子数的改变是轴承刚度变化的根源。基于改进理论算法进而分析轴承初始径向游隙、径向力、滚子设计数量等关键参数对圆柱滚子轴承性能的定量影响规律。     

滚动轴承弹性接触动态特性有限元分析

滚动轴承弹性滚动接触动态特性直接影响转子系统的精度及动态特性,针对滚动轴承弹性滚动接触动态特性问题,以深沟球轴承61914为例,在同时考虑内环、外环、滚珠及保持架变形的情况下,建立滚动轴承三维弹性滚动接触有限元模型,采用有限单元法计算滚动轴承在不同转速、径向力及轴向力等载荷工况下滚动轴承的接触应力及滚珠与内环的运动状态。结果表明,有限单元法能在满足高精度计算的情况下求解各种复杂工况下的滚动轴承动力学特性,为进一步研究滚动轴承弹性滚动接触动态特性提供有力的研究方法。     

圆柱滚子轴承的非对称修形

传统的修形理论仅适用于对称修形,而对称修形虽然可以避免直母线浪子引起的滚动体两端的“边缘效应”,但无法克服由偏载产生的“偏载效应”。根据接触力学理论,通过有限元方法对滚动轴承的分析,提出了浪子非对称修形新方法。有限元分析结果表明,提出的非对称修形方法既可以避免“边缘效应”,又可以克服“偏载效应”,从而使非对称修形滚子轴承有更高的承载能力和使用寿命。     

The Prediction of Contact Pressure–Induced Film Thickness Decay in Starved Lubricated Rolling Bearings

Under starved conditions the thickness and distribution of the lubricant film in an elastohydrodynamically lubricated (EHL) contact is directly related to the distribution of lubricant on the track in the inlet to the contact. In starved lubricated rolling bearings this lubricant distribution is determined by many effects. The authors have developed a model to predict the oil lost from the track induced by EHL pressure with no replenishment. A complete bearing is modeled with multiple rolling element EHL contacts and with the applied load to the rolling elements varying along the circumference of the bearing. Results of the oil layer thickness on the track are presented for a ball bearing and a spherical roller bearing for different bearing loads and rotational speeds. The predicted layer thickness decay rate for a ball bearing is significantly larger than for a spherical roller bearing and the predicted effect of the bearing load on the decay rate is small compared to the effect of the rotational speed. The predicted decay periods due to the contact pressure effect are small compared to the observed (grease) life of bearings. The results show that a bearing cannot sustain an adequate layer of oil on the running track unless significant replenishment takes place.     

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.     

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.     

Optimized Logarithmic Roller Crowning Design of Cylindrical Roller Bearings and Its Experimental Demonstration

A logarithmic profile is essentially an optimal geometry for rolling machine elements such as bearing rollers and raceways. Under most conditions of loading, it yields lower stresses to give longer endurance. Lundberg first suggested the basic profile, and some researchers followed him by modifying it to satisfy engineering requirements. In this article, the authors propose a mathematical optimization method for logarithmic profiles in roller bearing applications. Moreover, rolling contact fatigue life tests are carried out to make a comparison among logarithmically crowned, standard partially crowned, and modified partially crowned rollers. Results show that the logarithmically crowned rollers are beyond the modified partially crowned rollers in fatigue life, especially in poor lubrication conditions, although the logarithmic rollers require less workload to process the crowning.     

Determination of Static Load Distributions from Elastic Contacts in Rolling Element Bearings

A method has been developed for recording the elastic roll body contacts in the load zone for both radial and thrust rolling element bearings subjected to various static loading conditions. Employed in this investigation were a ball bearing and four types of roller bearings which included cylindrical, needle, tapered and spherical. Inspection of the contact areas, or footprints, yields a qualitative measure of the extent of loading arc, load sharing among rolling elements, contact characteristics such as end loading and effects of misalignment. Quantitative data on individual contacts permits the determination of load and stress distributions. Summation of the vertical components of individual roll body loads agrees with the total load applied to the whole bearing, thereby demonstrating the practicability and accuracy of this technique. Correlation of roll body loads with theoretical values varied, depending on angular position from the radial load plane. Finally, this paper indicates how static stress levels on the most heavily loaded element may be obtained and used as a basis for bearing life prediction.     

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。     

牙轮钻头空心圆柱滚子接触状况的有限元数值模拟

以牙轮钻头滚动轴承为研究对象,对常规直母线圆柱滚子与内圈滚道的接触状况进行三维有限元数值模拟。在验证模型正确性和算法可靠性的基础上,对不同载荷和空心度下直母线空心圆柱滚子的接触状况进行有限元分析。计算结果表明,合理空心度的滚子可以降低轴承的等效应力,从而提高轴承的疲劳寿命;合理空心度的选取往往与轴承系统的材料参数、几何结构尺寸参数以及所受的外载荷等因素有关,但采用合理的空心度仍然无法消除滚子轴向端部几何边界突变处的奇异性。研究结果发现,空心滚子的最大法向接触应力和最大等效应力相对于轴向初始接触对称中心线发生了一定程度的偏移;在相同空心度下,等效应力与载荷并非正比关系。此项研究为通用空心滚子轴承在牙轮钻头中的承载性能预测和结构优化设计以及今后的推广应用提供理论参考。     

轧机圆锥滚子轴承载荷的边界元法解析及实验研究

针对滚动轴承接触的特点,在轴承边界元法中采用赫兹接触理论对滚动体与轴承内、外圈的接触宽度进行修正。编制了三维有摩擦弹性接触的专用轴承边界元法计算程序,对轧机圆锥滚子轴承的载荷分布进行了数值模拟。采用轴承座直接测量法对轧机圆锥滚子轴承的径向和轴向载荷进行测试,并与数值模拟的结果进行了对比,实验测试结果与数值模拟的轴承载荷的分布规律基本一致,证明了边界元方法求解轴承载荷分布的正确性和有效性。     

双列调心凹面滚子轴承接触载荷分析

在考虑滚子与套圈、滚子与保持架以及保持架与引导套圈作用力的条件下,建立双列调心凹面滚子轴承动力学模型。以某双列调心凹面滚子轴承为研究对象,与静力学分析模型滚子最大接触载荷计算结果对比,验证了模型的正确性。并分析了工况条件(轴向载荷、径向载荷、倾覆力矩、转速)和结构参数(滚子数量、滚子长度、径向游隙)对滚子最大接触载荷的影响,结果表明:随轴向载荷增大,一列滚子受力增大,另一列滚子受力减小;随径向载荷增大,滚子最大接触载荷增大;随倾覆力矩增大,2列滚子接触载荷几乎不变;随转速增大,滚子最大接触载荷增大;随滚子数量增多和滚子长度增加,滚子最大接触载荷减小;随径向游隙增大,滚子最大接触载荷呈先减小后增大趋势。     

Study on Rolling Contact Fatigue in Hydrogen Environment at a Contact Pressure below Basic Static Load Capacity

A method to determine the shoulder height in an angular contact ball bearing using a 3D contact analysis is proposed. The load analysis was performed by calculating the distributions of internal loads and contact angles for each rolling element. From the results of the bearing load analysis and the contact geometry between the ball and raceways, 3D contact analyses using an influence function were conducted. The algorithm developed was applied to an angular contact ball bearing for an automotive wheel. The effects of axial load on contact pressure at the inner and outer raceways were evaluated and the critical axial loads in the present shoulder height were calculated. The critical shoulder heights were also determined when the bearing was subjected to a practical load for a steel ball bearing. The proposed methodology is generally applicable for the purpose of reducing the material cost and improving the efficiency of the bearing design process.     

深沟球轴承的载荷分布与刚度特征研究

采用有限元法计算了"奇压"与"偶压"两种受载形式下深沟球轴承的静力学响应。对比讨论了轴承内接触应力分布、轴承变形及刚度的变化特征。结果表明当外载荷达到某一值时,关键滚动体与外圈滚道接触中心的接触应力明显大于与内圈滚道接触中心的接触应力,并随着载荷的增加,这个趋势越发明显;两种受载形式下,轴承的位移与刚度表现出明显的差异,奇压形式下,轴承的径向位移小于偶压形式下的径向位移,而奇压形式下的轴承刚度则大于偶压形式下的刚度;相同载荷作用下,静力学方法计算的轴承径向位移小于有限元法计算结果。     

对数母线圆柱滚子凸度量的有限元分析

以42724QT型铁路客车圆柱滚子轴承为分析对象,对其滚子进行对数母线凸度的分析,借助有限元软件ANSYS完成了在不同凸度量下的接触应力分析及比较,得到了一定载荷下的较优凸度量区间,同时进行了相同凸度不同载荷下的接触应力比较。结果显示,为避免"边缘效应",一定的载荷对应一个较优的凸度区间,并且理论凸度近似值与分析后得到的最优凸度有一定的误差,即使是对数母线的滚子,当载荷超出正常加载范围时,仍会出现"边缘效应"。     

高速板带轧机四列滚动轴承非均匀接触力学性能及修形优化研究

针对高速板带轧机四列滚子轴承在偏载运行下滚子-滚道非均匀接触力学性能及滚子修形优化进行研究。建立了滚子-滚道接触力学模型,模拟了其偏载运行下的接触力学性能。提出滚子接触应力均匀分布原则,采用非对称对数曲线对四列滚子母线修形优化。研究表明：偏载轧制导致四列滚子承载分布严重不均,以某冷轧机四列滚子轴承为例,载荷分布偏差较常规轧制增加20%,列间接触应力差接近200MPa,单列滚子轴线方向接触应力差接近60MPa。接触应力差随修形量k₃差值减小而减小,当k₃差值减小到一定程度时,接触应力差反而变大,最终修形曲线优化参数为k₁=1.3,k₂=1,k₃=0.014-0.011。研究为延长轴承使用寿命、保证轧机安全稳定运行提供理论依据,具有重要工程意义。     

New Stress-Based Fatigue Life Models for Ball and Roller Bearings

New stress-based life models are introduced to define “dynamic stress capacity” in rolling bearings for the first time. The generalized stress capacity equations are formulated, for both point and line contacts, in terms of distinct geometrical and materials parameters while the empirical constants are now material independent. Life equations are first developed for individual rolling element to race contacts and then statistically combined to estimate lives of both races, rolling elements, and, finally, the whole bearings for both ball and roller bearings. An estimate of the empirical constant for the ball bearing equation is derived by regression analysis of available experimental data. The applicable constant for roller bearings is then derived by relating the ball and roller bearing constants to the fundamental subsurface fatigue hypothesis applicable to both point and line contacts. For AISI 52100 bearing steel at room temperature, life predictions with the new stress-based equations are in complete agreement with those currently provided by widely used load-based formulations, where the empirical constant contains the elastic properties of AISI 52100 bearing steel. In addition to these life equations based on the magnitude and depth of maximum orthogonal subsurface shear stress and the volume of material stressed, a new model that eliminates life dependence on the depth of maximum orthogonal shear stress and relates life to only the subsurface maximum shear stress and the stressed volume is presented. Though the predicted life estimates with the currently used and newly introduced life models are comparable in the contact stress range of 2 to 3 GPa, the new model provides significantly higher lives at low contact stresses.