三角齿型摩擦轮与柔性轨道小变形接触下滚动摩擦力分析

研究三角齿型摩擦轮与柔性轨道在小变形接触条件下的滚动摩擦力,根据Crook的弹塑性滚动摩擦理论,将柔性轨道简化为弹塑性变形体建立有限元模型,分析得到的滚动摩擦力和滚动摩擦因数。设计滚动摩擦力测量试验,测定滚动摩擦力矩,对比理论值和计算值,得出齿形摩擦轮与轨道小变形接触下合适的滚动摩擦模型。     

滚动摩擦机理和滚动摩擦系数

指出古典滚动摩擦定律存在着一定的局限性，对滚动摩擦机理从摩擦学观点进行了探讨，分析了滚动阻力来自微观滑动和弹性滞后。通过一系列金属和非金属材料的摩擦试验，测得滚动摩擦系数值及其变化规律，从而指出了影响滚动摩擦系数的主要因素。最后认为，滚动摩擦系数还须靠实测来确定。     

PV值对尼龙PA66滚动摩擦阻力的影响

利用自行设计的滚动摩擦试验台,考察了PA66-HT200轮轨副在不同载荷、速度下的滚动摩擦阻力和滚动摩擦系数,分析了滚动摩擦机理。结果表明:随速度增加,滚动摩擦阻力和滚动摩擦系数均增大;随载荷增加,滚动摩擦阻力增大,滚动摩擦系数减小;随PV值的增加,滚动摩擦阻力几乎呈线性增长。理论分析显示这一现象与PA66的粘弹性密切相关。     

周动力滚动摩擦系数的计算方法

通过以一定法向压力相互接触的滚子与平面在摩擦过程中的物理变化和几何关系，揭示滚动摩擦原理，推导和建立滚动摩擦系数的计算公式，在完成中心动力作用下的摩擦系数计算公式后，继续用计算法确定周动力作用下的滚动摩擦系数。     

铸铁HT200、45~#钢、聚四氟乙烯、尼龙PA66滚动行为的对比分析研究

针对滚动摩擦中的弹性滞后效应问题,利用自行设计的滚动摩擦实验台,考察了HT200、45#钢、PTFE、PA66与HT200配副在不同载荷、速度下的滚动摩擦行为,利用CETR UMT-2型试验机及LKDM-2000轮廓摩擦磨损仪考察了PTFE和PA66的蠕变行为。对不同速度、载荷下滚动摩擦阻力及滚动摩擦系数的变化情况进行了研究,重点分析了滚动摩擦阻力与速度、载荷之间的耦合关系,从弹性滞后效应的角度分析了材料的黏弹性质对滚动摩擦行为的影响机理。研究结果表明:滚动摩擦系数随速度增加而增大,HT200、45#钢、PTFE和PA66的滚动摩擦系数之比约为1∶0.99∶1.03∶1.05;滚动摩擦阻力随PV值增加而增大,且二者间存在线性关系,PTFE和PA66拟合直线的斜率显著高于HT200、45#钢。     

滚动摩擦力的产生机理及其计算

本文讨论了滚动摩擦力的产生机理及计算方法。利用能量理论导出了不同材质及相同材质滚动副的滚动摩擦系数和滚动摩擦阻力系数计算公式。说明了滚动摩擦阻力不仅与法向载荷有关,而且与滚动体的几何尺寸、机械性能、表面特性有关。经过实验验证,说明所得公式比较接近实际,可以做为工程中计算滚动摩擦的近似公式。     

打印机分纸胶辊的摩擦特性

胶辊的摩擦特性直接影响打印机的分纸效果,文中在橡胶的粘弹性标准线性固体模型理论上,建立了胶辊与纸张间的滚动摩擦接触模型,推导出胶辊的接触应力分布函数与滚动摩擦系数表达式。matlab数值分析及实验结果表明:胶辊的滚动摩擦接触应力成不对称分布;压力和转速对胶辊的滚动接触区宽度、宽度比与摩擦系数有影响。     

石墨烯润滑油润滑下摩擦副摩擦因数预测模型

轴承摩擦状态很复杂，且以滚动摩擦为主，滚动摩擦因数的精确计算或者测量都很困难。针对轴承滚动摩擦因数难以测量的问题，对与滚动摩擦因数密切关联的滑动摩擦因数进行了试验和预测研究，提出了一种最佳滑动摩擦因数的预测网络模型。首先，在石墨烯润滑油润滑工况下，进行了Si₃N₄-GCr15摩擦副的摩擦磨损试验，获得了不同工况下石墨烯质量分数下的滑动摩擦因数；然后，提出了广义回归神经网络(GRNN),并运用遗传算法(GA)优化得到了光滑因子(σ),获得了最佳滑动摩擦因数的预测网络模型GA-GRNN;最后，对测试集预测结果与其他预测模型预测结果进行了预测效果验证，并结合验证集预测结果进行了预测模型的应用验证。研究结果表明：与常规GRNN模型以及误差反馈(BP)神经网络模型相比，GA-GRNN模型的摩擦因数预测准确度更高，且其预测误差更小；GA-GRNN模型的验证集预测值很接近真实值，预测值平均准确率达到了92.30%,预测相对误差在[0.000 990 17,0.008 324 9]区间内，对滑动摩擦因数预测效果良好。该结果可为轴承滚动摩擦因数的预测提供基础。     

滚动摩擦副打滑理论的研究

研究了圆柱型滚动摩擦副微观打滑机理，建立了接触区应力应变的理论模型，利用边界元法编制计算程序对打滑率进行数值计算，得到稳态滚动摩擦副打滑率的变化规律。对打滑率的修正方法作了简要分析。     

滚柱轴承离合器滚动摩擦功耗分析

利用摩擦理论分析了国外新产品滚柱轴承离合器滚动摩擦功率消耗，推导了滚柱轴承离合器弹性滞后和粘着效应引起功耗的表达式，并讨论了有摩擦时工作扭矩Ｍ与轴向位移量ΔＬ之间的关系。     

冷轧塑性加工中的摩擦性质

根据轧制时轧件金属发生塑性变形特点及摩擦副间的介质实际情况，经理论分析认为冷轧塑性加工中的摩擦性质是混合摩擦或边界摩擦，并得到了实验的验证。     

轧制塑性加工中的摩擦机理

针对轧制塑性加工中轧件金属发生塑性变形之特点,本文经过理论分析,建立一个新的摩擦机理：滚－滑摩擦机理。     

车轮滚动接触疲劳与磨耗耦合关系数值模拟

滚动接触疲劳和磨耗是车轮失效的主要方式。通过三维弹性体非赫兹滚动接触理论得到接触斑内的法向、切向应力和材料上不同深度处的最大切应力分布,以CL60钢和贝氏体车轮钢为例,基于"layer"滚动接触疲劳失效模型和Zobory车轮磨耗模型,分析LM型车轮踏面和75 kg.m–1钢轨型面匹配时轮轨接触条件和车轮材质对车轮滚动接触疲劳和磨耗竞争关系的影响。计算结果表明,摩擦因数为0.3时,CL60钢在小蠕滑条件下会发生滚动接触疲劳损伤,在大蠕滑条件下只有轴重大于30 t时才会出现滚动接触疲劳损伤,而贝氏体车轮钢只有在大蠕滑条件且轴重为30 t时,载荷循环次数小于1×105的情况下才会出现滚动接触疲劳损伤;摩擦因数为0.6时,CL60钢和贝氏体车轮钢在各种工况下的滚动接触疲劳损伤速度都小于相同条件下的磨耗速度。     

A 3-D finite element method analysis of cold rolling of thin strip with friction variation

In this paper, a three-dimensional rigid-plastic finite element method (FEM) model to simulate the cold rolling of thin strip with different friction models is described. The effects of rolling parameters, such as work roll diameters and reductions, are analysed in this study. The simulation and experimental values of rolling pressure and spread (the difference of strip width before and after rolling) show a good agreement when friction variation in the roll bite is considered. The roll separating force, spread and forward slip for constant friction and friction variation models are also compared. The friction variation in the roll bite has a significant effect on the simulation results.     

Simulation of transient friction of a cylinder between two planes

The need for good friction models for transient motions has increased as a consequence of the increased use of mechatronics and control engineering principles in precision mechanics. The machine elements in such equipment often involve rolling and sliding contacts. Most studies of friction in rolling and sliding contacts running under dry or boundary lubricated conditions have examined steady-state conditions.This paper describes simulations of the motion of a cylinder between two planes, first with a step change in velocity and then with an oscillating motion of the upper plane. The motion of the cylinder is determined by the friction in the contacts and the inertia. The friction in the rolling and sliding contacts is simulated with a brush model. The surfaces are assumed to be ideally smooth.For the step change in velocity, there is initially a period of complete sliding in the upper contact. During the sliding period, the friction force is the maximum possible, but it decreases as the complete sliding ends. The simulations show heavily damped oscillations, with frequencies corresponding to the natural translatory and torsional frequencies of the system. For the oscillating motions the sliding increases with the frequency of the motion, as expected.     

Friction torque in grease lubricated thrust ball bearings

Thrust ball bearings lubricated with several different greases were tested on a modified Four-Ball Machine, where the Four-Ball arrangement was replaced by a bearing assembly. The friction torque and operating temperatures in a thrust ball bearing were measured during the tests. At the end of each test a grease sample was analyzed through ferrographic techniques in order to quantify and evaluate bearing wear.A rolling bearing friction torque model was used and the coefficient of friction in full film lubrication was determined for each grease, depending on the operating conditions.The experimental results obtained showed that grease formulation had a very significant influence on friction torque and operating temperature. The friction torque depends on the viscosity of the grease base oil, on its nature (mineral, ester, PAO, etc.), on the coefficient of friction in full film conditions, but also on the interaction between grease thickener and base oil, which affected contact replenishment and contact starvation, and thus influenced the friction torque.     

3D Analysis of cold rolling using a constitutive model for interface friction

Full three-dimensional numerical analyses are carried out for the cold rolling of plates of finite width, to study the effect of the width spread during rolling. The contact and friction between roll and plate is modeled in terms of an interface constitutive model that accounts for the friction forces in the rolling direction as well as those in the transverse direction that give resistance to the width spread. At low normal pressures Coulomb friction is represented while at high normal pressure a yield stress limitation of the maximum tangential stress is incorporated, and slip as well as no slip is accounted for. Finite strain elasto-plasticity is applied for the plate material, using mostly isotropic hardening or in a few cases kinematic hardening to represent the effect of a rounded vertex on the yield surface. In addition, for a given plate thickness and degree of reduction the effect of different values of the roll radius and the effect of different values of the plate width are analysed.     

冷连轧机轧制力的影响因素

通过将轧制变形区划分为微单元,对变形区内轧制力影响因素的变化规律进行研究。根据微单元塑性变形方程式,建立单位轧制压力的计算模型。针对变形抗力、摩擦因数等非线性因素,建立基于神经网络校正系数和工作参考点方法的数学模型,分析其在变形区内的变化规律。针对轧辊压扁和轧制力计算的耦合现象,采用计算机迭代计算的模型完成轧制力的解耦计算。工业轧机实际数据验证了采用微单元方式计算轧制力预报精度高,可用于生产实践。     

滚动轴承摩擦力矩动态误差的实验研究

以测量滚动轴承摩擦办矩试验装置的结构为实例,研究了测量误差,分析了试验装置的某些参数对误差的影响,提出了减少误差的途径.