非牛顿流体微观热弹流润滑理论

求得了非牛顿流体线接触微观热弹流润滑的准稳态数值解。结果显示,横向微凸体能够造成强烈的局部动压,且微凸体越高或越窄,动压效应便越强。     

齿轮传动的摩擦学设计

运用弹流理论对齿轮传动进行了分析,提出从摩擦学角度进行齿轮传动设计的原则,为降低齿轮的磨损,提高传动效率和使用寿命提供了依据。     

Effect of operational conditions and environment on lubricity of hydrophobins in water based lubrication systems

Abstract

In this study, the effect of operational conditions (normal load, sliding velocity) and environment (pH and ionic strength) on the lubrication properties of two different hydrophobin proteins were investigated using pin on disc tribometry and ellipsometry. The studied proteins were wild type HFBI and the glycosylated hydrophobin FpHYD5. It was observed that the friction of a stainless steel versus stainless steel contact lubricated with either of the hydrophobins did not depend on the normal load. However, increased sliding velocity occasionally led to a decrease in friction when the surfaces were lubricated with the glycosylated FpHYD5. The tribological behaviour of FpHYD5 was studied at pH values ranging from 3 to 9 and generally lowered friction by 31–38% and wear by 40–65% compared to the corresponding buffer solutions. An exception was pH 9, where FpHYD5 increased friction and wear compared to the buffer solution. Ionic strength affected both the amount of protein that was adsorbed and the lubrication properties of glycosylated hydrophobins.     

Initial steps in the surface chemistry of vapor phase lubrication by organophosphorus compounds

The surface chemistry of trimethylphosphite (CH₃O)₃P has been studied on Cu(111) and Ni(111) surfaces in order to model the initial steps in the reactions of vapor phase lubrication by organophosphorus compounds. The initial reactions involve scission of the P–O bonds to deposit methoxy groups (CH₃O_(ad)) on the surfaces. On the Cu(111) surface the formation of CH₃O_(ad) species occurs only after oxidation of the surface. The CH₃O_(ad) groups on Cu(111) decompose by β‐hydride elimination to produce formaldehyde (O=CH₂) and adsorbed hydrogen. CH₃O_(ad) groups are formed from (CH₃O)₃P on the clean Ni(111) surface and decompose by complete dehydrogenation to CO and adsorbed hydrogen atoms. This chemistry is very similar to that observed for CH₃OH on these surfaces. These results suggest that alkoxides are important intermediates in the decomposition of vapor phase lubricants on metal surfaces. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Role of Nickel in Ni-Containing Nanotubes and Onions as Lubricant Additives

We studied tribological properties of Ni-containing single wall carbon nanotubes and carbon nano-onions. Nickel catalyst particles are often necessary to synthesize these carbon nanoparticles. Nanoparticles were used as additives dispersed in a lubricating poly-alpha-olefin base oil. We show superior tribological properties for carbon nanoparticles containing residual nickel cores. Thus, removal of nickel catalyst from carbon particles is not necessary for excellent tribological performances. Mechanisms of friction and wear reduction are discussed in the light of analytical data. Data suggest the tribo-formation of a Ni-doped carbon-like material.     

Tribology of X-1P vapor lubricated hard disks

The tribological characteristics of vapor lubricated X-1P films on carbon coated disks were investigated as a function of lubricant thicknesses (0.2–2 nm) and compared with traditionally dip-coated X-1P and PFPE films. Glide and flyablity tests were performed and the lubricant redistribution in the ‘wear track’ was investigated using a surface reflectance analyzer (SRA). A critical lubricant thickness was found to exist for X-1P below which lubricant accumulation was observed, while lubricant loss was found to be present if the thickness of the lubricant film was greater than the critical thickness.     

Activation of the SiC surface for vapor phase lubrication by Fe chemical vapor deposition from Fe(CO)5

The feasibility is demonstrated of a new approach to the vapor phase lubrication of ceramics using organophosphorus compounds. The surface of SiC is shown to be unreactive for the decomposition of trimethylphosphite, (CH₃O)₃P, a simple model for organophosphorus vapor phase lubricants such as tricresylphosphate. In order to activate the surface of SiC it has been exposed to Fe(CO)₅ at a temperature of 600 K. Chemical vapor deposition serves as a means of depositing Fe on the SiC surface. The Fe-modified SiC surface is then shown to induce the decomposition of adsorbed (CH₃O)₃P. The mechanism of (CH₃O)₃P decomposition is similar to that observed on Fe(110) surfaces modified by the presence of oxygen. It is initiated by P–O bond cleavage to produce adsorbed methoxy groups, CH₃O_(ad), which then decompose by -hydride elimination resulting in H₂, CO, H₂CO, and CH₃OH desorption. It is suggested that chemical vapor deposition of metals using high vapor pressure metal-containing compounds such as Fe(CO)₅ can serve as a mechanism for continuous, in situ activation of ceramic surfaces for vapor phase lubrication in high temperature engines.     

不同极压抗磨剂在磨损条件下的膜特征

本文选择了磷酸三甲酚酯（ＴＣＰ）,硫代磷酸三苯酯（ＴＰＰＴ）和２－巯苯并噻唑（ＭＢＴ）三种酯类润滑油常用的极压抗磨剂进行四球磨损试验,并用俄歇电子能谱（ＡＥＳ）对磨损试验后得到的磨斑进行表面膜的表层和深层剥离分析,试验发现磨斑上的表面膜的组成和厚度与四球试验得到的润滑性能有良好的对应关系。     

喷丸齿轮弹流润滑特性分析

利用有限元软件Abaqus仿真得到喷丸强化后齿轮表面形貌,采用MATLAB分析喷丸强化后表面微观形貌对齿轮弹流润滑性能的影响,并与机加工表面的弹流润滑性能进行比较。结果表明：喷丸强化后齿轮的弹流润滑特性总体和机加工齿面保持一致,但喷丸处理后减少了粗糙峰对压力和膜厚的影响,齿面更容易建立起油膜,润滑状态较好;喷丸强化形成的橘皮凹坑有利于储存润滑油剂,齿轮的润滑性能得到了提高。     

Optimisation of a humidity chamber method for the quantitative evaluation of vapour phase corrosion inhibitors for mild steel

During manufacturing, storage and transport, corrosive substances in the environment easily attack metal items. Corrosion inhibitors are substances, which, when added to corrosive environments in relatively small dosages, will drastically reduce corrosion rates. Vapour phase corrosion inhibitors or volatile corrosion inhibitors (VCIs), also called vapour phase inhibitors (VPIs), are similar to the organic adsorption-type inhibitors but they possess a high vapour pressure.     

海水润滑塑料轴承的微观热弹流润滑分析

考虑轴承表面海水润滑膜温度场和轴承表面横向粗糙度等因素,对塑料轴承的弹流润滑问题进行了研究。利用压力求解的多重网格法和弹性变形求解的多重网格积分法以及温度求解的逐列扫描技术,得到塑料轴承微观热弹流润滑问题的完全数值解,讨论了连续波状粗糙度、载荷、轴承转速对海水润滑膜压力及膜厚的影响。数值计算结果表明：轴承表面粗糙度对润滑膜压力和膜厚分布都有一定影响,连续波状粗糙度使润滑膜压力和膜厚分布产生振荡;转速和载荷对压力分布影响较小,随转速的增大、载荷的减小,膜厚都有明显的增大。     

方向性微孔对润滑状态转化的影响

基于平均流量模型和微凸体接触模型,研究混合润滑状态下织构表面的摩擦特性,通过数值求解得到Stribeck曲线,分析法向载荷、润滑油黏度、表面粗糙度、方向因子和倾斜角对摩擦因数及名义摩擦副间隙等摩擦性能参数的影响规律。结果表明：混合润滑条件下,随着载荷的减小或润滑油黏度的增大,摩擦因数减小,名义摩擦副间隙增大,混合润滑转变为流体润滑时的临界转速降低;随着表面粗糙度的增大,摩擦因数和名义摩擦副间隙均增大,临界转速升高;随着倾斜角的减小或方向因子的增大,摩擦因数减小,名义摩擦副间隙增大,并且倾斜角越小,临界转速越低。     

柴油机缸套表面微沟槽织构润滑性能仿真分析

针对缸套表面织构微沟槽形貌,建立了缸套-活塞环摩擦副混合润滑理论模型,并采用MATLAB编程计算来分析微沟槽形貌参数对其润滑摩擦性能的影响规律。结果表明：缸套表面微沟槽可以形成很好的油膜压力,有效地改善缸套-活塞环间的润滑状态;随着微沟槽角度的增大,最小膜厚比逐渐增大,其润滑效果也越来越好,综合考虑摩擦润滑性能和机油耗性能情况下,最佳的微沟槽角度为60°。在上止点附近,面积占有率变化Sp对量纲一摩擦力影响较大;在其他区域,面积占有率对摩擦力影响不大;综合考虑油膜厚度与摩擦力,当Sp=0.15时效果最好。随着微沟槽深宽比e的增大,量纲一摩擦力不断增大,当e从0.025增大到0.150时,平均量纲一摩擦力增大了2.3倍,但深宽比过大,润滑效果将会减弱。研究结果认为,最佳深宽比的范围为0.05~0.08。
     

Adsorption and surface chemistry in tribology

Adsorption on sliding surfaces and the chemical changes occurring within a few nanometers of the surface are key to the performance of lubricants and lubricant additives in the boundary lubrication regime. By means of the methods of modern surface science, these phenomena are beginning to be elucidated on a molecular level. This knowledge will be essential, both for the development of higher-performance lubricants, capable of high-temperature operation, as well as for the design of environmentally benign alternatives to the lubricant systems in current use.     

全膜润滑到边界润滑的过渡研究

摩擦副在工作中经历不同的润滑状态,利用数值模拟的方法研究了从全膜润滑到边界润滑的过渡。数值实验显示,从全膜到边界润滑是个光滑的过渡过程。对于光滑表面,在较低速度下过渡到混合润滑;而对于粗糙表面,全膜到混合润滑的过渡发生在较高速度下。     

连续波状粗糙度对直齿轮热弹流润滑的影响

工程实践中没有理想光滑的表面,在齿轮弹流润滑中,油膜的厚度通常与某些切削工艺形成的金属表面粗糙度处于同一数量级,所以表面粗糙度对齿轮弹流润滑的影响是不应该忽略的。在考虑不同啮合点处的曲率半径、卷吸速度、轮齿载荷随时间变化的基础上,考虑轮齿表面连续波状粗糙度对弹流润滑的影响,利用多重网格技术求得齿轮瞬态微观热弹流润滑的完全数值解。结果表明,连续波状粗糙度会造成齿轮瞬态弹流润滑的油膜压力和温升产生振荡,并使最小膜厚变薄,最高压力变大,最大温升增大。轮齿间振荡的高压和高温会造成齿轮振动疲劳破坏,所以连续的波状粗糙度对齿轮的润滑是不利的。     

表面研磨对点接触弹流润滑的影响

利用计算机模拟获得磨削加工表面及其研磨后表面,完全数值求解磨削表面及研磨表面点接触弹流润滑,就研磨对润滑的影响进行分析与研究。结果得出,表面形貌的微观弹流效应导致局部油膜压力增大,研磨能有效减缓油膜压力波动,改善表面润滑性能。