Computational model for determination of dynamic load capacity of large three-row roller slewing bearings

In the presented paper a calculation procedure for determination of dynamic load capacity of large three-row roller slewing bearings is presented. The calculation procedure consists of three main parts: (i) determination of internal contact force distribution in a large three-row roller slewing bearing with consideration of bearing clearances and ring support deformations, (ii) determination of stress field in the contact area between raceway and rollers as a consequence of contact forces and (iii) determination of the bearing’s fatigue life due to contact fatigue of the raceway. The internal contact force distribution is determined numerically by using a symmetry 3D FEM-model of a large three-row roller slewing bearing. Another numerical procedure is used to determine the stress field in the contact area between rollers and raceway. This problem is studied on different roller types: cylindrical roller (without profile correction), fully crowned roller (logarithmic-profile) and partially crowned roller (ZB-profile). Numerically determined contact stresses then serve as a basis for fatigue analyses, where the bearing’s service life of the bearing is determined by using the stress-life approach, considering typical material parameters of the bearing’s raceway.     

Effect of the rheological properties of a lubricant on the carrying capacity of hydrostatic bearings

On the basis of computational results an analysis is performed of the influence of the rheological properties of plastic lubricants on the carrying capacity of a hydrostatic bearing.Volgograd Polytechnical Institute. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 64, No. 2, pp. 195–198, Febuary, 1993.     

基于小波的滚动轴承故障诊断

滚动轴承是机械设备中极易损坏的零部件.旋转机械的故障有百分之三十是由轴承故障引起的,因此引入轴承故障诊断对于机械化生产和作业来说是十分必要的.在对轴承故障的机理和特征全面了解的基础上,利用了离散小波变换对不同工矿下的原始信号进行分解,然后对小波分解出的近似和细节信号进行Hilbert变换,利用得出的信号可以较好地提取故障特征.     

Reliability evaluation and selection of rolling element bearings

A procedure based on graph theory and matrix approach has been developed for the reliability evaluation and selection of a rolling element bearing for an application. The reliability of the bearing is evaluated considering reliability of its elements and their connections. This is modeled in terms of Reliability Graph of a Rolling Element Bearing. This graph is represented by an equivalent matrix called Rolling Element Bearing Reliability Permanent Matrix to obtain a matrix function-Reliability Permanent Function. This function is the characteristic of reliability of the rolling element bearing for the application. Reliability Index (R_I) of the bearing is also defined. It is a numerical measure of the bearing reliability and is obtained by substituting reliability value of the bearing elements and their connections in the matrix function. The paper also suggests how to assess these reliability values to obtain the index. The proposed procedure is useful for designers and practicing engineers for selection of an optimum bearing for a given application. The methodology is illustrated by means of an example.     

Investigation of rolling contact fatigue cracks in ball bearings

Rolling contact fatigue in a ball bearing is studied using the experimental method. Fatigue pits and spallings on the rolling surface are investigated, and the strain-hardening beneath the contact surface is studied using the microhardness profile. Moreover, surface and subsurface crack layouts and the effect of inclusions on crack nucleation are studied by optical and electron microscopy. Additionally, a simulated model is used to study the influences of the crack inclined angle and the inclusion’s hardness on fatigue damage in bearings.     

Apparatus for determining the starting moment of rolling bearings

Summary The described apparatus for measuring the starting moment of rolling bearings is distinguished by its automatic operation, which excludes the human errors which may occur in the direct reading of an instrument scale, the absence of a ponderable pendulum, the great stability of the readings, the exclusion of friction effects of any other mechanical systems, high sensitivity, which makes it possible to record moments differing by 0.005 g · cm, smooth and continuous increase of the external torque, the possibility of installing the apparatus in an airtight chamber in which the atmosphere can be varied (vacuum, various gases, increased pressure, etc.): and thus it possesses significant advantages over other known instruments.     

滚动轴承局部故障数学模型的建立与应用

在前人所建立的模型基础上,引入了滚动体的随机滑动和周期性变化的振动传递函数,并综合考虑了静态载荷分布和故障点的位置,建立了滚动轴承局部故障的随机振动数学模型。模型使用MATLAB语言编程实现,并通过给其混入噪声进行故障诊断试验,验证了该模型在轴承故障机理分析和故障诊断方面的实效性。     

滚动轴承复合故障振动建模及Lempel-Ziv复杂度评价

故障建模是探寻机械诊断中认知规律的关键环节。为了更能准确地预知振动特征,研究滚动轴承结合面间的多体接触与传递过程的耦合作用,根据Hertzian理论建立一种详细的计及内圈-外圈-轴承座传递过程的6DOF振动模型。从轴承实际运动学的角度刻画故障的形成及渐进发展过程,进而实现单点、复合故障的有效模拟,并与实验结果进行了比较。轴承运行过程中故障状态的变化,必然导致振动信号复杂性的变化。基于非线性动力系统理论,引入Lem-pel-Ziv复杂度指标评价运行状态。结果表明,单点及复合故障的信号具有不同的复杂度,反映了不同故障状态的动力学响应的差异。Lempel-Ziv复杂度能有效描述轴承振动信号的复杂性,可作为量化指标用于滚动轴承状态评价。     

Mechanical behaviour of nitrogen-alloyed austenitic stainless steel hardened by warm rolling

This investigation deals with the hardening effect, by warm rolling, of the alloy Uranus B66^®, a nitrogen-alloyed austenitic stainless steel produced by Creusot-Loire Industrie. The warm rolling process leads to substructural changes from the appearance of planar slips at low deformation, the micro-twins formation followed by sequences of their bending, breaking and disappearance at intermediate deformation, and finally to the formation of heavily deformed domains at the highest warm rolling reduction. The mechanical behaviour of the warm rolled Uranus B66, under quasi-static tensile and quasi-static and dynamic compression tests, has been analysed. Warm rolling increases the mechanical resistance to a saturation level and decreases the ductility when compared to that of the as-received material. The dynamic flow stress after warm rolling up to 85% increases to such a level that brittle fracture occurs after small plastic deformation. The origin of the strength saturation is related to the terminal microstructure derived from the warm rolling deformation.     

Ultimate fracture capacity of pressurised pipes with defects - Comparisons of large scale testing and numerical simulations

In this paper results from large scale 4-point bending tests of pipe-segments are compared with numerical analyses using LINK_pipe. The experiments were carried out as a part of the joint industry project Fracture Control - Offshore Pipelines. The comparisons between large scale testing of pipelines and numerical analyses also address the effect of biaxial loading on the strain capacity. The defect is positioned on the tension side of the pipe when applying the load. A parametric study on changing the nominal wall thickness of the pipe is carried out. Due to variation in the yield stress, a parametric study to see the effect of this variation was also performed. The results demonstrate that ductile crack growth and biaxial loading are important elements in fracture assessment procedures for pipelines.     

一种滚动轴承特征频率的自动识别方法研究

为解决传统滚动轴承故障诊断及状态监测中依赖单一故障特征频率,以及诊断过程中人为主观因素造成诊断结果的不定性与效率低等问题,以包络谱与共振解调技术为例,提出一种自动识别滚动轴承故障特征频率及其倍频与调制频率的方法。该方法对信号进行包络谱或共振解调分析,在此基础上通过迭代算法依次找出转频与故障频率成分,并依据各成分在识别结果中的比例来进行故障诊断。人为仿真故障及滚动轴承加速寿命实验证明了文章方法的有效性。     

基于分类器组的轴承故障识别方法研究

提出一种基于设备运行数据构造分类器组用于滚动轴承故障识别的方法。在决策表上使用属性约简的遗传算法找出构成候选基分类器的较好约简,再使用多样性筛选的遗传算法找出最终的约简,以此为基础结合加权投票策略构建分类器组用于模式分类。通过轴承正常情况、内圈、外圈和滚动体故障的识别实验验证了方法的有效性,得到了较好的实验结果。     

Fault analysis of the wear fault development in rolling bearings

Signal processing methods are required to extract the features related to the wear process and how to track its evolution. Several signal processing methods are commonly applied in the experimental and real field tests. The generated signals of these tests are quite complex due to the dynamic nature of wear process, i.e., interaction among different wear mechanisms. Therefore, a dynamic model is required to explain the physical phenomena behind the detected signals. However, the current dynamic models in the literature lack to model the dynamic response under wear deterioration process over the whole lifetime, due to the complexity. Therefore, the purpose of this paper is to illustrate the evolution of the fault features with respect to the wear evolution process. It utilities a newly developed dynamic model and applies different commonly used signal processing methods to extract the diagnostic features of the whole wear evolution progress. The statistical time domain parameters and spectrum analysis are used in this study. Numerical results illustrate several issues related to wear evolution i.e., capabilities, weaknesses and indicators. The results show the extracted fault features and how they change with respect to the wear evolution process i.e., how the topological and tribological changes influence the extracted defect features. In this sense, the study helps to justify the experimental results in literature. The study provides a better understanding of the capability of different signal processing methods and highlights future enhancement.     

基于约束独立成分分析的轴承复合故障特征提取方法

为从复合故障信号中提取各故障特征,提出一种离散小波变换(DWT)和约束独立成分分析(CICA)相结合的单通道复合故障诊断方法。首先通过DWT方法将单通道振动信号进行小波分解后,利用小波重构函数重构各层分解信号。然后取重构信号的包络信号作为CICA算法的输入矩阵,基于滚动轴承先验知识建立参考信号,从而分离出轴承各故障信号,提取故障特征。最后,在滚动轴承故障模拟实验台上进行了方法验证。结果表明:该方法可有效分离滚动轴承外圈和滚动体故障,实现了轴承复合故障的诊断。