基于热弹流的滤波减速器转臂轴承润滑性能分析

由于载荷、接触几何、粗糙表面、热效应等因素的影响,分析不同工作条件下滤波减速器转臂轴承工作界面润滑状态较为困难,为了研究转臂轴承润滑性能,本文建立了转臂轴承的热弹流混合润滑模型。以静力学和运动学建立滤波减速器转臂轴承(球滚动体-滚动轴承）力学模型,结合点接触热弹流混合润滑理论建立轴承热弹流润滑模型,使用离散卷积快速傅里叶变换方法求解弹性变形和表面温升,使用有限差分法求解雷诺方程和能量方程,分析轴承接触副物理尺寸、载荷、卷吸速度和接触副粗糙表面等外部工况对轴承润滑特性以及表面下应力的影响。从数值模拟结果中可以看出：较大滚动体半径有益于轴承润滑油膜形成,提高轴承的承载能力;不同的机械加工表面下接触副平均膜厚和温度随转速和滑滚比变化趋势相同;轴承接触副润滑状态从混合润滑进入全膜润滑状态,油膜内最大温升先减小后增大;提高机械加工表面光洁度有利于提高转臂轴承润滑状态,减小最大表面下应力,提高表面接触强度。本文建立的转臂轴承热弹流混合润滑模型可以模拟接触和流体动压润滑同时存在的混合润滑状态,可以反映转臂轴承在各种工作条件下润滑性能,可以进一步判断其工作效率和使用寿命。     

表面粗糙度幅值对点接触混合润滑的影响

建立了粗糙表面点接触混合润滑的数学模型。针对外加载荷为800N和80N,润滑油卷吸速度由静止增加到5000mm/s的工况,引入油膜厚度比、接触区域比、接触载荷比和最大压力比等混合润滑参数,分析了3种不同表面粗糙度幅值对混合润滑性能的影响。分析结果表明:接触表面的粗糙度幅值对混合润滑区域内平均油膜厚度、最大压力等均有显著影响。     

润滑油黏度对高速球轴承性能及损伤的影响

为探究高速工况下润滑油黏度对轴承润滑状态及性能的影响,试验研究了Si_3N_4陶瓷和GCr15轴承钢材质的7014C型角接触球轴承在不同润滑油黏度条件下的温升和振动特性.结果表明,轴承温升及振动随润滑油黏度的增大呈现出先下降后上升的趋势,影响程度随转速的增大而增大.同时,陶瓷轴承较钢制轴承在不同润滑油黏度条件下均表现出更优越的性能.将试验结果与轴承润滑状态分析结合,讨论了润滑油黏度、润滑状态、轴承性能三者的关系,为高速角接触球轴承适用润滑油黏度的选择提供了重要依据.此外,本文还对不同润滑条件下的轴承滚动面损伤进行了分析.结果显示,全膜弹流润滑条件下,陶瓷轴承与钢制轴承滚动面损伤较小且差异不明显.部分膜弹流润滑条件下的轴承滚动面损伤严重,表面出现大量凸峰和凹谷,轴承滚动体及外滚道表面损伤较内滚道严重,钢制滚动体的表面划痕较陶瓷滚动体密且深.     

水平转弯颗粒流的离散元模拟

为了研究水平转弯输运物料时颗粒流的动力特性以及物料颗粒对输送带的作用机理,在离散元理论基础上,采用非线性HertzMimdlin接触模型,建立了水平转弯输运的离散元模型。以不同的角速度模拟测试颗粒平均速度,与计算的带中央切向速度相比,获得了一组比较接近的数字。说明所采用的接触模型和材料的物理参数是正确的。研究了两组不同的颗粒单元、4种滚动摩擦系数下的颗粒动力特性,发现颗粒平均速度与颗粒单元、滚动摩擦系数无关。通过输送带加速运行,模拟了料流分布以及料流对输送带外侧压力分布的影响。结果表明,随着带速的增加,带外侧平均压力逐步增加,而最大压力非线性地剧增。     

油介质下轮轨粘着特性数值分析-研究生论坛

基于二维滚动接触理论和部分弹流理论,建立了微凸体接触情况下的稳态部分弹流数值模型,运用多重网格法对油介质工况下的轮轨黏着特性进行数值仿真研究。利用所建立的数值仿真模型研究了轮轨接触压力分布情况,分析了滚动速度、载荷、轮轨表面粗糙度等参数对轮轨黏着特性的影响。结果表明:油介质条件下轮轨接触区的宽度比干态下要宽,是干态下接触区宽度的1.5倍左右;油介质下的轮轨黏着系数明显小于干态下的黏着系数;轮轨黏着系数随着速度的增加逐渐减小,随接触压力的增加而降低,随轮轨表面粗糙度的增加而增大。     

Air flow patterns and noise analysis inside high speed angular contact ball bearings

The vortex formed around the rolling ball and the high pressure region formed around the ball-raceway contact zone are the principle factors that barricades the lubricant entering the bearing cavity, and further causes improper lubrication. The investigation of the air phase flow inside the bearing cavity is essential for the optimization of the oil-air two-phase lubrication method. With the revolutionary reference frame describing the bearing motion, a highly precise air phase flow model inside the angular contact ball bearing cavity was build up. Comprehensive factors such as bearing revolution, ball rotation, and cage structure were considered to investigate the influences on the air phase flow and heat transfer efficiency. The aerodynamic noise was also analyzed. The result shows that the ball spinning leads to the pressure rise and uneven pressure distribution. The air phase velocity, pressure and cage heat transfer efficiency increase as the revolving speed increases. The operating noise is largely due to the impact of the high speed external flow on the bearing. When the center of the oil-air outlet fixes near the inner ring, the aerodynamic noise is reduced. The position near the inner ring on the bigger axial side is the ideal position to fix the lubricating device for the angular contact ball bearing.     

面齿轮等温点接触弹流润滑分析

建立面齿轮等温点接触弹流润滑模型,通过F O R T R A N语言编程计算面齿轮的油膜厚度和压力;分析小齿轮转速、面齿轮所受载荷和润滑油黏度对面齿轮润滑特性的影响。研究结果表明:转速和润滑油黏度越大,油膜厚度也越大,而载荷越大油膜厚度越小;二次压力峰随转速和润滑油黏度的增大而越明显,但随载荷的增大而趋于消失。     

材料填充对滤波减速器啮合力与润滑特性的影响

为提高滤波减速器寿命,设计在齿上开槽,并在槽内填充紫铜、硬铝合金、尼龙1010、丁晴橡胶的新型结构。建立了滤波减速器在不同位置啮合的有限元模型,计算了不同填充材料齿轮在不同啮合位置的啮合力。在此基础上建立了考虑齿面粗糙度的滤波减速器混合润滑模型,分析了转速对不同填充材料滤波减速器润滑特性的影响。有限元模型计算结果表明：材料填充可以增加滤波减速器轮齿啮合对数,有效减小啮合力,齿面最大接触力随着填充材料弹性模量的减小而减小。润滑计算结果表明,材料填充可以增大齿面间平均油膜厚度,有效提高滤波减速器润滑性能。在转速小于1 500 r/min时,通过材料填充可以降低接触面积比,转速大于1 500 r/min时,材料填充对接触面积比的影响不明显;在啮入啮出点时,转速大于1 500 r/min时,材料填充可以降低滤波减速器齿面最大接触应力,转速小于1 500 r/min时,最大接触应力随填充材料弹性模量的变化规律不明显;节点啮合时,丁晴橡胶和尼龙1010可以显著降低齿面最大接触应力。     

乏油状态下准双曲面齿轮传动润滑机理分析

在工程实际中,准双曲面齿轮不可避免地因润滑剂供给不足导致乏油问题,鉴于此,综合考虑了啮合区接触几何、粗糙形貌、入口区供油量、啮合界面速度矢量任意性等因素,建立了乏油状态下准双曲面齿轮传动界面任意速度矢量润滑分析模型,开展了乏油分析模型结果与文献实验数据的对比研究,数值分析了不同入口区供油量条件下准双曲面齿轮传动界面啮入点、啮合中点和啮出点的油膜演变规律,探讨了转速对不同供油量条件下传动界面润滑性能的影响。结果表明：乏油分析模型结果与文献实验数据取得了良好的一致性;随着入口区供油量的减小,3个啮合点油膜厚度的差异逐渐减小,当供油量减小到某一值时,3个啮合位置的油膜厚度基本一致;在不同的供油量下,转速对润滑状态的影响较为显著,油膜厚度随着转速的增加而升高,但是,转速升高到某一值时,乏油条件下的油膜厚度值将趋于稳定,而充分供油条件下的油膜厚度值将会继续增大。     

粗糙软接触润滑的摩擦因数

以刚性球在PDMS圆盘上运动为背景,建立了润滑条件下的软接触数学模型,通过数据处理将接触表面粗糙度的测量结果耦合到数学模型中,并根据接触时不同润滑区域的特点,提出了整体名义接触区域的摩擦因数计算模型,利用现有实验数据验证了模型的有效性。在不同润滑条件下计算并分析表面粗糙度在软接触中的作用。当润滑油的卷吸速度与黏度的乘积(μη)值较低时,流动的润滑油与微凸体间的相互作用产生的压力增量使摩擦因数显著增加。     

多孔阵列阳极氧化铝膜润滑性能的Stribeck研究

为了研究阳极氧化铝膜的多孔结构对其润滑性能的影响,分别制备了光滑表面氧化铝膜,40 nm孔径、90 nm孔径多孔表面氧化铝膜.用接触角测试仪测试了水、机油与3种表面的接触角;在不同润滑条件下,用摩擦磨损试验机UMT-2测试了3种氧化铝膜与GCrl5钢面接触的润滑性能.结果表明:多孔结构氧化铝膜增强了材料的亲水性能和亲油性能,90 nm孔径氧化铝膜表现出超亲油特征;水润滑和机油润滑条件下,速度从0.016 m/s增至0.32 m/s过程中,光滑氧化铝表面只能形成边界润滑区域,多孔表面得到了包含边界润滑、混合润滑和流体润滑的完整的Stibeck曲线.机油润滑条件下,40 nm孔径的膜达到最小摩擦系数的临界速度为0.28 m/s,最小摩擦系数为0.083,90 nm孔径的膜达到最小摩擦系数的临界速度仅为0.2 m/s,最小摩擦系数减小为0.023;机油润滑条件下,90 nm孔径的氧化铝膜板的Stribeck曲线,谷底区域更宽.     

滤波减速器轮齿表面瞬态微观弹流润滑模型

针对滤波减速器接触齿对多、齿间润滑状况复杂这一问题,建立了滤波减速器轮齿弹流润滑模型.该模型综合考虑了啮合齿对载荷分配、齿面几何间隙以及齿面加工粗糙度等因素,并采用牛顿(有限元)法实现了该润滑模型的完全数值解,得到了齿间油膜厚度、油膜压力沿啮合线的分布规律以及粗糙度对轮齿润滑特性的影响.结果表明:齿间油膜厚度和压力沿着啮合线变化,且存在着振荡和突变现象;加工粗糙度会导致齿面油膜厚度减小,润滑情况变差;正弦波状粗糙度表面的压力、膜厚值接近于真实粗糙度表面,一定程度上可以采用正弦波状粗糙度模拟齿面真实加工粗糙度.     

GCr15球-盘点接触摩擦副的滑滚摩擦磨损特性研究

选用GCr15钢盘和GCr15球作为摩擦副,在NGY‐6纳米润滑膜测量仪上开展球‐盘点接触摩擦副在润滑状态下的滑滚摩擦磨损实验,研究不同接触应力、钢球转速、滑滚比等参数对摩擦副的摩擦因数、磨损形貌的影响规律．结果表明：当接触应力和钢球转速一定时,摩擦因数随着滑滚比的增大而逐渐增加后达到稳定状态;当滑滚比一定时,摩擦因数随接触应力的增大而逐渐增大;当钢球转速低于300 r／min时,摩擦因数随着钢球转速的增大而减小;当钢球转速高于300 r／min、接触应力大于0．84 GPa时,摩擦因数随着钢球转速的增大而呈增大趋势．Stribeck曲线表明：当滑滚比为0．01时,摩擦副处于流体动压润滑状态;当滑滚比为0．03时,润滑状态随Sommerfield参数的增加而从边界润滑过渡到混合润滑;当滑滚比分别为0．05、0．1、0．3、0．5时,润滑状态为边界润滑．滑滚比较小时,磨损机制以疲劳磨损为主,随着滑滚比的增大,磨损机制转变为磨粒磨损．     

基于响应面方法的轴承多应力加速模型建模与验证技术

针对轴承加速寿命试验中多应力加速模型欠缺、失效规律认识不到位等科学问题,首先,深入分析真空、温度、预紧力、转速、微重力环境下,液体润滑轴承的界面微观失效模式及机理;然后,推导和建立考虑上述多应力综合作用机理的微观接触统一润滑模型,研究给出基于改进牛顿-拉夫逊法的数值解算方法;其次,设计5因素5水平的正交仿真方案,开展真空、温度、预紧力、转速、微重力的失效规律仿真与分析,获得微观接触界面膜厚、压力峰值、摩擦系数、最大下表面应力随应力水平及接触区尺寸变化的失效响应值;最后,建立了基于响应面方法辨识真空、温度、预紧力、转速、微重力水平与失效响应值之间的多应力加速模型,并对其进行试验验证及工程应用,奠定了空间轴承加速寿命试验的模型基础.     

Tribological characteristics and self-repairing effect of hydroxy-magnesium silicate on various surface roughness friction pairs

Tribological characteristics and self-repairing effect of hydroxy-magnesium silicate (HMS) dispersed in lubricant oil on steel-to-steel friction pairs with various surface roughness were analyzed. The friction-reduction, anti-wear and self-repairing performance of various surface roughness friction pairs were examined by friction testing machine. An operation comparison was made between SJ10W-40 lubricant with and without HMS. The surface morphology and elementary composition of the grinding cracks were analyzed by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results show that the lubrication state changes from boundary lubrication into mixed lubrication after operation in lubricant with HMS. The friction-reduction, anti-wear and self-repairing performance of the friction pairs with various surface roughness are distinctly different. There is a repairing film whose material is different from substrate material on the grinding cracks. In addition, Si, Mg, O, Al and other elements are deposited on the repairing film which contains nanocrystals of these elements. And HMS self-repairing material possesses superior performance of friction-reduction, anti-wear and self-repairing effects.     

分形粗糙面的主轴承弹流脂润滑分析

为探究弹性流体动压润滑(弹流润滑)状态下RV减速器主轴承接触表面之间的润滑特性,基于润滑脂的非牛顿特性以及粗糙表面分形理论,提出一种主轴承的点接触弹流脂润滑数值模型。首先,对该模型进行数值求解,得到脂膜压力、脂膜厚度的分布规律;然后,将其分别与其他点接触弹流润滑模型的数值结果和实验结果进行对比,验证了所建模型的正确性;最后,分析了主轴承表面光滑和粗糙状态下流变指数、分形维数、卷吸速度、载荷和润滑脂黏度对润滑性能的影响。结果表明:润滑脂的非牛顿性越明显,脂膜厚度越小且颈缩现象愈加不明显,接触区附近脂膜压力越符合赫兹压力分布,二次压力峰逐渐消失;考虑主轴承分形粗糙表面的弹流润滑特征更切合实际,增大分形维数,接触区真实接触面积增大,有利于降低脂膜压力,增加脂膜厚度;卷吸速度、载荷和润滑脂黏度对脂膜厚度分布的影响显著,对脂膜压力分布的影响较小;脂膜厚度以及最小膜厚越大,主轴承接触区脂膜不易破坏且越容易形成动压润滑。     

Thermal contact conductance at continuous roll-casting interface

The effects of surface roughness, strain rate, friction coefficient and pressure on real contact area were analyzed based on the research of Stupkiewicz. The real contact area model taking account of the effect of friction and deformation of material was obtained. The model of contact conductance at the rolling interface was obtained by integrating the specific feature of heat transfer through the interface of continuous roll-casting. The results indicate that the real contact area increases obviously when the material is under yield, and the real contact area varies inversely with surface roughness, whereas it varies exponentially with friction coefficient, strain rate and pressure, and the power factor depends on strain rate.     

Lubrication in strip cold rolling process

A lubrication model was developed for explaining how to form an oil film in the deformation zone, predicting the film thickness and determining the characteristics of lubrication in the strip rolling process, combined with the knowledge of hydrodynamic lubrication and rolling theories. Various mineral oils with viscosities from 0.032 to 1.6 Pa.s were used to obtain different film thicknesses in the strip cold rolling. Results from the experiment and calculation show that the oil film forming in hydrodynamic lubrication is up to the bit angle and a higher rolling speed or a higher rolling oil viscosity. The mechanism of mechanical entrainment always affects the film thickness that increases with the rolling oil viscosity increasing or the reduction rate decreasing in rolling.     

Effect of Pressure on Boundary Slip of Thin Film Lubrication Using Atomistic Simulation

Mechanical systems on all length scales may be subjected to nanoscale thin film lubrication(TFL). Molecular dynamics(MD) simulations were conducted to investigate the lubrication mechanism and boundary slip of squalane confined in nanogap at 293 K with two different film thicknesses and a wide range of pressures. The molecular distribution, density and velocity profiles of squalane were analyzed. The results show that the lubricant atoms tend to form layers parallel to the wall, but the lubricant molecules orient randomly throughout the film in the directions both parallel and perpendicular to the wall. Most squalane molecules appear twisted and folded, and extend to several atomic layers so that there are no slips between lubricant layers. The distances between the lubricant layers are irregular rather than broadening far away from the walls. The boundary slip at the interface of bcc Fe(001) and squalane only occurs at high pressure because of the strong nonbond interactions between lubricant atoms and wall atoms. The tendency of boundary slip is more obvious for films with thinner film thickness. According to the simulations, the relationship between the slip length and the pressure is given.     

谐波齿轮粗糙表面薄膜润滑计算

谐波齿轮传动齿面的润滑状态,考虑到表面粗糙度影响后,用基于平均流动模型的平均雷诺方程进 一步研究,推导薄膜润滑条件下齿面压力和油膜厚度的计算关系,计算剪切膜和挤压膜的数值解,给出齿面最小油 膜厚度曲线。结果表明,齿面表面粗糙度增大,由它所引起的动压效应增强,齿面上的润滑油易存留,能够建立起足 够的油膜厚度。