弹流润滑高速角接触球轴承旋滚比分析

为了提高主轴轴承的高速性能,提出弹流润滑高速角接触球轴承的数学计算与分析模型.针对实际生产工况建立弹流润滑高速角接触球轴承分析计算模型.并将弹流润滑高速角接触球轴承的旋转打滑分析转化为旋滚比的分析.通过计算与分析,得出弹流润滑高速角接触球轴承在不同工作条件下或选用不同轴承参数时,轴承旋滚比的变化规律及旋滚比与各参数之间的关系.为实际生产中高速角接触轴承的选择使用和轴承的参数优化设计提供了理论依据,并为机床高速主轴用支撑轴承的设计与优化提供分析计算模型.     

水润滑条件下速度对车轮钢磨损特性的影响

在JD-1轮轨模拟试验机上,利用赫兹模拟准则研究了水润滑条件下速度对车轮钢滚动磨损性能的影响,利用扫描电子显微镜等分析了车轮钢磨损表面的变化情况.结果表明:随速度的增加,车轮钢试样磨损量呈现减小的趋势,滚动接触表面间润滑状态从边界润滑转变为部分弹流润滑;车轮钢磨损机制主要由微切削、微断裂磨损向轻微塑性变形磨损转变.     

限制空间中的弹性流体动压润滑

在经典的弹性流体动力润滑理论分析中,油膜压力的计算要满足载荷平衡条件,而这一条件并不适用于发生在限制空间中的弹流润滑,当弹流润滑发生在限制间隙中,油膜的承载力会随工作参数的变化而变化。对限制间隙条件下等温线接触弹流润滑问题进行数值分析,研究油膜厚度及压力的变化规律。结果表明:在限制间隙等温线接触弹流润滑条件下,油膜厚度及压力随速度参数以及材料参数的增加而增加,而限制间隙增加时,膜厚增加,压力减小。根据数值分析结果,拟合出限制间隙条件下的膜厚计算公式,该公式有较小的计算误差。     

脂润滑点接触副混合润滑模型研究

考虑润滑脂非牛顿特性和粗糙表面微凸体接触几何,基于润滑脂Herschel-Bulkey流变模型和微凸体K-E弹塑性接触模型,确定了润滑介质弹流作用和微凸体接触作用的并行处理方案,并提出了一种流体动压区和微凸体接触区的压力边界条件假设,建立了脂润滑点接触副混合润滑的确定性模型.结合处理边界条件的虚压力替代法,构建了混合润...     

限制空间中的弹性流体动压润滑分析

在经典的弹性流体动力润滑理论分析中,油膜压力的计算要满足载荷平衡条件,而这一条件并不适用于发生在限制空间中的弹流润滑,当弹流润滑发生在限制间隙中,油膜的承载力会随工作参数的变化而变化。对限制间隙条件下等温线接触弹流润滑问题进行数值分析,研究油膜厚度及压力的变化规律。结果表明:在限制间隙等温线接触弹流润滑条件下,油膜厚度及压力随速度参数以及材料参数的增加而增加,而限制间隙增加时,膜厚增加,压力减小。根据数值分析结果,拟合出限制间隙条件下的膜厚计算公式,该公式有较小的计算误差。     

等温点接触弹流润滑典型特征的数值分析

随着航空制造业的发展,对润滑技术及润滑理论研究提出了更高的要求.点接触弹流润滑广泛存在于滚动轴承等高副接触的零件中.润滑本身的工况十分复杂,实际上是润滑、接触和磨损的耦合.研究点接触弹流润滑,对研究摩擦副的润滑状态,提高其润滑能力具有重要的理论意义和实用价值.采用多重网格技术,运用Fortran语言编制相应的计算程序,...     

滚动轴承部分弹流润滑的研究

介绍一种在部分弹流润滑状态下测量滚动轴承金属接触时间比率的方法。对油润滑条件下椭圆接触滚动表面的粗糙峰接触作了理论分析。该理论应用于柔性滚动轴承的润滑分析,取得计算与实验相吻合的结果。所介绍的实验方法可以用于部分弹流润滑的研究和滚动轴承润滑状态监测等方面。附图4幅,参考文献9篇。     

橡胶滑块与镀镍钢环的水润滑机理分析

对水润滑橡胶轴承在完全水润滑条件下的标准实验模型进行了弹流理论建模,应用多重网格技术对理论模型进行了数值计算和结果分析。结果表明:完全水润滑条件下,在高速轻载时形成了弹流润滑,而在低速重载时,即使在完全水润滑条件下橡胶滑块与镀镍钢环之间也较难形成稳定的弹流润滑。计算结果与实验结果基本一致。     

载荷对凹陷表面的动态微弹流润滑特征的影响

研究了表面凹坑在不同接触载荷和滚滑率的情况下,通过弹流润滑区时对油膜压力和形状产生的干扰现象。根据对微弹流润滑特征分析发现,只有在表面存在相对滑动的条件下,进入弹流接触区的表面凹坑才随接触载荷 的增加被逐渐地压平变浅;而在纯滚动条件下,进入弹流接触区的表面凹坑深度几乎与载荷大小无关保持不变;所有条件下因表面凹坑进入弹流接触区产生的油膜干扰凹陷深度与载荷大小无关而保持一个稳定的值。     

两波动表面间的椭圆接触热弹流润滑数值分析

研究滚滑工况下两波动表面间的椭圆接触微弹流润滑问题,建立两接触表面均有连续波动的粗糙度模型,求得热条件下的完全数值解。假设卷吸速度沿接触椭圆短轴方向,快速运动表面的速度是另一表面的4倍,表面纹理相似的两波动表面间的微弹流润滑大多是周期性时变问题,以准稳态解为初始条件,逐个周期求得时变热解。讨论不同方向的表面微观连续波动对润滑性能的影响,并将牛顿和非牛顿模型的数值结果进行比较。结果表明,波动表面间接触区里的压力、膜厚、温升等呈现特定的特征,两表面波动皆为纵向纹理时,润滑膜厚度最小润滑条件最恶劣;热效应和非牛顿效应在微弹流问题中都很明显。     

Impact Wear Study of Lubricated Contacts

Pivotal hammer type impact testers are used in an experimental study of repetitively impacted lubricated contacts. Various steels are used in one- and two-body wear modes; the rate process of wear is investigated with respect to the impact parameters (normal and tangential approach velocity), and lubricant viscosity. For normal impact, a boundary lubrication system forms, but superimposed sliding speeds with a viscous lubricant tend to create an elastohydrodynamic lubrication (EHL) condition, greatly resisting wear. Approximate measurable wear equations are derived for cylindrical striking surfaces.     

Remarks on the wear of a journal bearing lubricated by a grease containing a powdered PTFE additive

This paper presents the results of tests on wear of a journal bearing lubricated by a grease containing a powdered polytetrafluorethylene (PTFE) additive. The wear of the bearing lubricated by such a grease is initially greater than the wear of the bearing lubricated by the grease without the PTFE additive, but the total wear of the bearing lubricated by the PTFE loaded grease is almost 2.8 times less than the wear on a similar bearing lubricated by the unloaded grease. An explanation of this phenomenon is suggested.     

Material selection criteria for water lubrication

The unusual degree of interaction between service performance parameters and material selection for water lubricated contacts is developed. The importance of exploring the full range of variation in operation is stressed. The problems of corrosion, dirt and thin films associated with water lubricants in valves, bearings and seals are discussed. Examples are shown of some benefits gained through the use of water lubrication. The theory of elastohydrodynamic lubrication is shown to be of little use for water lubrication as a result of the negative and small positive (depending on temperature) pressure coefficient of viscosity. The properties of some successful water lubricated contact materials are reviewed with emphasis on water swell, abrasive wear resistance and minimum Hersey Variable values.     

Sliding Wear of an Al Alloy SiC Whisker Composite

The tribological properties of a well-studied powder metallurgy metal-matrix composite, i.e., 20 volume percent SiC whiskers in 2124-T6 Al alloy matrix, were measured for the three principal orthogonal orientations under dry and lubricated sliding contacts. The sliding wear mechanisms were identified through analyses of wear tracks and subsurface microstructure by scanning and transmission electron microscopy techniques. The results for sliding wear of this 2124 Al-SiC whisker composite indicate a much higher wear when dry than when lubricated, and a strong wear anistropy, which is correlated with the ureal fraction of SiC whiskers on the wear plane. SEM and TEM analyses show direct evidence of adhesive wear through plastic deformation for dry sliding and abrasive wear through plowing and polishing for lubricated sliding.     

表面具有焊层的45~#钢冲击磨损的实验研究

使用杠杆原理式冲击磨损实验台及表面形貌仪等研究冲击载荷作用下表面具有不锈钢焊层的45#钢的表面损伤行为。实验工况分干接触及2种不同黏度的润滑油润滑3种接触方式,研究在不同冲击次数条件下,材料表面的损伤情况,并探讨不同黏度润滑油对冲击磨损机制的影响。结果表明:不锈钢焊层对45#钢基体起到了良好的保护作用,润滑油的存在会在一定程度上抑制冲击所造成的塑性变形,使冲击凹坑呈现出与干接触时不同的表面形貌;随冲击次数的不同,材料的损伤机制主要是黏着磨损、疲劳破碎及疲劳剥落;在材料损伤的各个阶段均伴有塑性变形的出现。     

Microstructural and sliding wear behaviour of a heat-treated zinc-based alloy

The effect of heat treatment on microstructure, hardness, tensile properties, fracture mode and wear behaviour during lubricated and dry sliding of the zinc-based alloy with 25 wt.%Al was studied. Microstructural investigation and chemical analysis of as-cast and heat-treated specimens, the fracture and worn surfaces, as well as wear debris were performed by scanning electron microscopy and energy dispersive spectroscopy. Wear tests were carried out using a disc-on block-type wear machine. By a relatively simple heat treating consisting of a short-term annealing in the single-phase region followed by water-quenching, the elongation has been markedly improved, while the strength was maintained high. The results indicate that the wear rate strongly depends on the microstructure, applied load and sliding conditions. The wear rate increases with load, and under dry sliding conditions the wear rate is approximately two orders of a magnitude higher than under lubricated conditions. During dry sliding the best wear behaviour was displayed by the water-quenched specimens, whereas slowly cooled specimens showed the higher wear rate. Lubrication strongly affects the wear behaviour. Contrary to dry sliding, slowly cooled specimens exhibit the best wear properties under lubricated conditions. The wear mechanisms were proposed for dry and lubricated sliding. An erratum to this article can be found at     

Wear mechanisms in oil-lubricated and dry fretting of silicon nitride against bearing steel contacts

The wear and friction behaviour of silicon nitride against bearing steel was investigated under lubricated and dry fretting conditions as a function of amplitude and test duration. Tests were performed on a high frequency fretting tester. Silicon nitride bearing balls were used as the upper oscillating specimens while the lower stationary flats were standard specimens of bearing steel. Amplitudes in the intermediate 5 to 50 μm range and a test duration from 10 to 360 min were studied. In lubricated conditions a commercial lubricant. ISO VG 220, was used. Light microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Auger spectroscopy (AES) and transmission electron microscopy (TEM) were employed to determine the wear mechanisms.

Under lubricated conditions transition from high to low wear volumes was recognised with increasing amplitude. At lower amplitudes and in the early stage of fretting tests at moderate amplitudes, mechanical wear dominated. Cracks on the stick-slip boundary and spalling of a thin tribolayer was observed. Under these conditions the highest wear in lubricated fretting was obtained. In the final stage of fretting tests at moderate amplitudes, and from the beginning at higher amplitude, tribochemical wear is suggested as the dominant wear form. A 0.2 μm thick tribolayer was observed on the contact, containing inclusions with different Fe and Si contents. A very high concentration of carbon, formed by oil degradation, was also determined in this layer, confirming the critical influence of oil on the wear behaviour.

Quite a different wear mechanism is proposed for dry fretting conditions. Results of AES analysis showed a layer an order of magnitude thicker than in lubricated fretting, also having a remarkably different chemical composition. TEM analysis confirmed that the reaction layer consisted of a silica-rich amorphous phase containing small inclusions of Fe₂O₃ and Fe₃O₄. In contrast to lubricated conditions, where the layer created was ductile, in the case of dry fretting the layer was brittle. The continuous process of forming and spalling the brittle tribolayer caused much higher wear rates and wear losses than under lubricated fretting conditions. No transition in wear behaviour was observed as was the case in lubricated fretting.     

Wear mechanisms of K2Ti4O9 whiskers reinforced Al20Si aluminum matrix composites with lubrication of water and tetradecane

The tribological properties of K₂Ti₄O₉ whisker reinforced Al20Si aluminum matrix composites were investigated in a mode of low amplitude reciprocal sliding. The ball-on-disk tests were performed at applied loads of 20–100 N and sliding velocity of 0.09 m s⁻¹. The water lubricated composites demonstrated higher wear resistance and friction coefficient than the tetradecane lubricated composites did. The main wear mechanism is microgrooving at low applied loads and tribochemical wear at high applied loads for the pairs lubricated with water, microgrooving at all test loads for the pairs lubricated with tetradecane.     

超声振动对不同黏度润滑油摩擦学性能的影响

研究GCr15/45#钢摩擦副在4种不同黏度的润滑油润滑时,有和无超声振动下的摩擦磨损性能,采用扫描电子显微镜分析磨痕表面形貌,探讨在不同黏度润滑油作用下,超声振动对润滑油摩擦学性能的影响机制。结果表明:超声振动对不同黏度润滑油摩擦学性能的影响是不同的;超声振动可以提高低黏度润滑油润滑的减摩抗磨性能,如在6#白油润滑时施加超声振动后,摩擦副间的摩擦因数和磨损体积分别减小了13.6%和17.5%;高黏度润滑油润滑时,超声振动会加剧摩擦副的摩擦磨损,如在150BS润滑时施加超声振动后,摩擦副间的摩擦因数和磨损体积分别增加了10.4%和50%。     

Wear of gear of circular-arc tooth-profile: effect of helix angle and oil viscosity

The results are presented of an experimental investigation carried out at Mansoura University Laboratories aimed at studying the effect of change of helix angle and lubricating oil on wear of a relatively new type of gearing of circular-arc tooth-profile. Eighteen pairs of gears of 6 DP, 91.5 mm pitch diameter and different helix angles were run in power circulating gear test rig at different speeds and transmitting different loads, and the gears were lubricated with oils of different viscosities. It was found that wear increases with increasing helix angle and decreases with increase of oil viscosity. Variations of amount of wear with all the test variables are presented.