VC轧辊的承载特性研究

对控制压力与轧制力共同作用下的VC(variable crown)轧辊的承载特性进行了研究。基于所开发的VC轧辊系统,分析了辊缝形状和辊缝凸度与轧制力及控制压力的关系,提出了临界最大控制轧制力的概念。研究结果表明:当轧制力小于轧辊系统的最大临界控制轧制力时,其板形控制能力优于同规格的实心平辊;当控制压力较大且轧制力较小时,轧辊系统可以实现零凸度或负凸度的负载辊缝。     

Simulation of roller guide wear in a high temperature test rig

Simulation of roller guide wear in rod or wire rolling mills has been performed in a high temperature test rig where the specimen rollers are in intermittent contact with the periphery of a heated rotating steel disc.By varying the time in contact during each cycle and deliberately superimposing a sliding component on the rolling contact, three components of guide roller wear were separated and quantified. The dominant component is wear due to sliding at the contact surface during rolling, followed by the isolated contribution from absolute rolling, while wear during roller acceleration is of less importance.Surface studies and the observed linear increase in wear vs. number of test cycles together with the linear increase in wear rate with normal force clearly show that abrasion by disc oxides is the dominant wear mechanism at elevated temperatures. The influence of disc temperature on the operating wear mechanisms as well as the resulting wear are also evaluated.A quantitative classification of four guide roller materials, a high chromium tool steel, two grades of high chromium cast iron and a cermet, has also been made. The hard cermet, containing about 50 vol.% titanium carbides, proved to be the outstanding material in roller guide applications.     

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...     

FEM Comparison of Ball and Roller Bullgears

A structural finite element model has been developed for calculating the forces transmitted through the rolling elements (load distribution) in a bullgear assembly. The elastic structural model consists of 3-D beam elements used to approximate the global race deflection and non-linear springs that approximate the combined rolling element/raceway contact deflections. For rollers, an upperbound on the contact stress (assuming linear variation of force along the length of the roller) is estimated by modeling the rollers as pairs of nonlinear springs. The finite element approach iteratively solves the contact forces at each, rolling element. Contact stresses are then calculated from the contact, forces using Hertz contact theory. This approach is applied to analyze two proposed designs of ball and crossed roller bearing, bullgear assemblies used for rotating the radar antenna on top of a ship's mast. The loads analyzed include those arising from wind loading and from out-of-flatness of the inner race of the bearings due to deflection of the mast. The distribution of the load and the maximum contact stresses for the proposed bullgear assemblies are estimated and compared. It is found that the maximum contact stress in the crossed roller bearing is less than that in the ball bearing for both types of loads. Furthermore, the analysis shows that the out-of-flatness loading produces significantly higher stresses than wind loading.     

Failure Mechanisms in High-Density Polyethylene Rollers

This paper describes failure processes in plastic rollers that undergo rolling contact, and the effect of initial surface roughness upon wear and rolling fatigue. Experiments were performed with mating cylindrical rollers of high-density polyethylene (PE rollers) and chrome-plated cylindrical driving rollers. Surface roughness of the PE roller is affected by three successive transition processes. In the first period, the amount of wear can hardly be measured, although a reduction of surface roughness is noted. During the second period, wear occurs in proportion to the initial surface roughness. In the third period, wear becomes independent of the initial surface roughness, and increases in a manner exponential to load. At the end of this period, small cracks appear randomly, and grow into pits. Roller fatigue Life, defined by the time when cracks appear, is shown by an S-N curve. It is found that fatigue limiting stress, represented by Hertz stresses, is about 10⁷pa.     

内燃机排气凸轮-滚轮副异常工况下热弹流润滑分析

以某型号内燃机排气凸轮-滚子副为研究对象，建立有限长线接触条件下瞬态热弹流润滑数学模型及完全数值求解方法。依据实际载荷谱等工作参数下，给出凸轮-滚子间的滑动模型，获得凸轮-滚子副在凸轮旋转周期内润滑特性，并分析凸轮与滚子之间的打滑、滚轮偏斜和滚轮凸度对接触副润滑的影响。结果表明：打滑导致接触区温度和摩擦因数明显升高，从而弱化接触区润滑状态；滚子偏斜时油膜厚度明显减小，增加润滑失效的可能性。研究表明，在设计滚子凸度时考虑滚子偏斜问题的影响，可以在一定程度上缓解其负面影响。研究结果为凸轮-滚子副的润滑设计提供了一定的理论依据。     

Study on design and simulation of a novel isolator cylindrical roller bearing

The sliding friction of the cylindrical roller bearing makes the internal resistance of the bearing large. Thus, this paper proposes to replace the cage with rolling isolators being placed between the cylindrical rollers, making the rub of all the elements be rolling friction. Therefore, the driving torque of the bearing is greatly reduced. First, the structure and working principle of this kind of bearing are described, the geometric parameter relationship of the roller and the isolator is analyzed, the feasible range of the parameters of the isolator is deduced based on the NFL203V type cageless bearing is proposed. Then, the ADAMS software is used for motion simulation of this novel cylindrical roller bearing. The best design plan is obtained through a comparison of the different schemes. Finally, experiments of bearing temperature are conducted, which shows the working temperature of the isolator cylindrical roller bearing is lower than that of the traditional roller bearings.

     

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.     

A study on the sound of roller bearings operating under radial load

The purpose of the paper is to numerically investigate the sound characteristics of roller bearings operating under radial load. For the sake of simplifying the analysis, it was assumed that the roller bearings are infinitely long, a noise source due to pressure fluctuation of oil film is taken as a line noise source, and acoustic energy losses in the bearing are neglected. To obtain sound characteristics of the bearing, the rolling contact load and the sound pressure level distributions were calculated for various operating conditions, and the results were compared with each other. How much the bearing noise can be affected by the design parameters, such as radial clearance of the bearing, viscosity of lubricant, and the number of rollers was also investigated. The results and discussions of the present paper could aid in the design of low-noise roller bearings and to solve the noise problems related to such bearings.     

The effect of changing the rolling direction on the rolling contact fatigue lives of annealed and case-hardened steel rollers

The effects of changing the rolling direction and of repeated loading on the rolling contact fatigue lives of annealed 0.45% carbon steel rollers and case-hardened nickel-chromium steel rollers under conditions of sliding rolling contact were studied. The influence of plastic flow in the subsurface layer on the rolling fatigue life was examined. The increase in the rolling fatigue life of an annealed steel roller due to a change in the rolling direction was significant, especially when the rolling direction was changed just before the formation of macroscopic surface cracks and pits. The effect with case-hardened steel rollers was negligible. The varying effects of changing the rolling direction on the rolling fatigue life were due to differences in work-hardening and the extent of plastic flow in the rollers.     

On The Dynamic and Thermal Performance of a Zero Clearance Auxiliary Bearing(zcab) for a Magnetic Bearing System

Structural and thermal analysis of a zero clearance auxiliary bearing (ZCAB) for magnetic bearing systems is presented. The ZCAB consists a series of rollers whose centers are initially placed on a circle. At the open condition all rollers have an initial clearance about the rotating shaft. As the shaft drops on the ZCAB rollers, either due to failure of the magnetic bearing system or a transient shock, the centers of the rollers move circumferentially along a curve path and after eliminate the initial clearance by closing around the shaft and re-centering it. This is known as the closed condition. The overall stiffness of the ZCAB will then depend on the stiffness of each single roller and the initial clearance between the rollers and the shaft. This is affected by the number of rollers that will touch the shaft which will also vary the load applied on the rollers. The low shaft-rollers traction coefficient and overall dynamic support characteristics obviate the possibility of backward whirl, however this traction and the generated heat in the rolling element embedded in the rollers are sources of heat generation. This paper presents the results of a transient analysis for the ZCAB structural stiffness. A preliminary thermal model of the ZCAB and comparison between the predictions and test results are also discussed. Some design guidelines are presented to help improve the performance of the ZCAB in the case of high temperature working conditions.     

航空自润滑关节轴承的内锥面滚铆工具设计

依据航空标准的规定要求,研究了一种新型的翻边固定的滚铆工具,以实现滚轮纯滚动、表面质量好、对轴承启动力矩影响小的质量目标。根据速度合成定理研究了滚轮实现纯滚动的条件,设计了内锥面的滚轮;以滚铆MS14101-9关节轴承为例,研究了两种滚轮对轴承外圈座圈之间的贴合度、轴承内外圈等效应力、轴向推出力、翻边表面质量的影响;最后,通过虚拟正交试验,以航空标准规定的轴承启动力矩范围为约束,以翻边固定后的轴承内圈外球面位移变化量为优化指标,研究了内锥面滚轮的滚铆工具的翻边载荷和公转转速的参数优化。研究结果表明：内锥面滚轮的工具可实现良好的工艺质量;当翻边工具的翻边载荷4000 N、公转转速200 r/min时,可以保障翻边固定后工艺质量指标和轴承启动力矩在航空标准规定范围内。     

Estimation of Generated Axial Force Considering Rolling–Sliding Friction in Tripod-Type Constant Velocity Joint

ABSTRACT

This study proposes a new generated axial force (GAF) estimation model of tripod-type constant velocity (CV) joints. For development of the model, kinematic analysis was performed to derive the relative coordinates of components and contact points. Through the analysis, the normal load that acts on contact points was also obtained. This study employs two friction models—pure sliding and rolling–sliding—to obtain the friction coefficients on the contact points. Particularly for the rolling–sliding model, this study used the experimental analysis on rolling–sliding ratio and friction coefficients were studied using a tribometer. By introducing two models, this study considers not only the pure sliding friction but also the rolling–sliding friction that occurs between spherical rollers and tracks.

This study verifies the GAF estimation model by comparing the simulation results with the experimental results. A tripod-type CV joint was set as a target and its GAF was derived by the model. Then, its actual GAF was measured and the results were compared with each other. A GAF measurement system was set up for the measurement in this study. The estimated results show similar trends with the measured results under low-resistance torque condition and the GAF model provides very accurate estimation under high-resistance torque conditions.     

四辊轧机有载辊缝解析模型研究

针对轧制过程中轧辊的弹性变形和轧辊与轧件间的相互作用，通过对四辊轧机辊系变形和受力状况的分析，从理论上详细推导了直观的有载辊缝形状函数，明确了有载辊缝形状函数与相关因素的对应关系。同时，为了验证辊缝解析模型的准确性，采用该模型对某铝热连轧机的精轧末机架的出口板凸度进行了理论计算，并与在线测得数据进行比较，结果表明：该模型计算精度高，相对误差较小(低于15％)。该模型不但为板形的控制以及轧制板凸度的建模提供了理论基础，还为预报板形、研究板带截面上任一点的板凸度提供了方便。     

对数母线滚子光弹流润滑的实验研究

为了研究对数母线滚子凸度量对滚子摩擦副润滑油膜的影响 ,本文在自制的有限长线接触光干涉弹流试验机上 ,测量了中载、富油润滑和纯滚动工况下对数修形圆锥滚子与玻璃盘之间的油膜形状与膜厚。实验结果表明对数母线轮廓滚子的凸度量对其端部的油膜厚度和膜形分布有较大的影响 ,在给定的工况条件下 ,存在一个使滚子轴向油膜厚度最为均匀的最佳凸度量 ,此最佳凸度量比在相同工况条件下用静弹性接触力学方法求得的最佳凸度量大     

三辊行星轧制空间模型建立研究

根据三辊行星轧机的运动规律和轧辊设计原理,利用坐标变换的方法,建立起既有倾斜角β又有偏转角α的空间轧辊模型,研究了三辊行星轧机轧辊建模和定位的方法,确定了轧辊和轧件接触点计算的方法和轧件模型,在此基础上建立了三辊行星轧制空间模型.     

基于ANSYS的四列圆柱滚子轴承接触应力和刚度分析

对四列圆柱滚子轴承的接触应力、变形以及径向刚度进行了研究.建立了四列圆柱滚子轴承的有限元三维模型,基于ANSYS和Hertz接触理论,阐述了建模过程中的关键步骤,结合短应力线轧机的应用实例,计算了轴承滚子、内圈的接触应力与变形分布,直观表达了交错排列滚子之间的应力分布情况,计算结果和Hertz理论值相比较,具有较好的一致性.通过计算不同载荷下的轴承变形（轴承内孔轴线的相对位移）,获得了轴承刚度随径向载荷变化的规律.     

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。     

Wear properties of DLC-coated steel rollers running with highly contaminated lubrication

The presence of hard contaminants in lubrication can lead to the premature failure of rolling bearings. To reduce the negative effect of such contaminants, hard carbon-based coatings (diamond-like carbon; DLC) can be applied to the surfaces of steel bearings. DLC coatings generate a low friction and a high sliding wear resistance to enhance the tribological properties and improve the durability of running components. This work explores the merits of DLC coatings for use in very demanding applications, such as in highly contaminated environments. The wear properties of DLC-coated bearing rollers were evaluated by comparing them with uncoated rollers. The degree of wear found on the coated rollers was serious, especially under relatively high contaminant concentrations. The three-body abrasive wear produced a relatively coarse scoring of the coating surface, which caused the corresponding disc to suffer more damage than the disc running against an uncoated roller under the same operating conditions. The results indicate that supposedly wear-protective coatings cause even more damage to running surfaces once they have been broken up by hard contaminants, and highlight the importance of keeping the bearing coating intact. In practise, it is important to eliminate contaminants from the lubricant of rolling bearings, in particular for bearings with a DLC anti-wear coating.     

三排滚子转盘轴承的校核计算方法

针对现有转盘轴承在工程应用中所出现的滚道塑性变形、滚道疲劳剥落和套圈结构断裂这三种失效形式,利用转盘轴承的数值分析模型和有限元分析模型建立了联合载荷作用下三排滚子转盘轴承的校核计算方法。数值分析模型借助于变形协调条件和受力平衡条件解决了滚动体负荷分布的静不定求解问题;有限元分析模型将滚子简化为弹簧单元,而套圈仍然采用实体单元,避免了实体滚子与滚道接触的大量非线性数值求解计算。利用所建立的校核方法计算得出了滚道的抗塑性变形安全系数、滚道的疲劳寿命和套圈的结构强度安全系数,为判定该轴承满足给定应用工况要求的程度提供了依据。