Tribochemistry of Fluorinated Fluids Hydroxyl Groups on Steel and Aluminum Surfaces

This paper describes products of tribochemical reactions of Z-Dol 2500 and 1H,1H,2H,2H-tetra-fluorooctanol, produced on steel and aluminum surfaces. The fluorooctanol was used as a model compound to study the reactions of hydroxyl groups. Tribochemical reactions were initiated by friction in the steel/steel and steel/Al contacts, using an Optimol SRV (Schwingung Reibung Verschleiβ) reciprocating sliding tester. The products of these reactions, deposited in the wear scars on steel and Al discs, were studied using reflective FTIR spectrometry (microscopy and grazing angle) and X-Ray photoelectron spectroscopy (XPS). Under boundary lubrication conditions on metal surfaces, fluorinated compounds containing hydroxyl groups formed carboxylic and alkoxyl salts. FTIR spectra indicate that Fe and Al carboxylic salts occur mainly in bidentate configuration.     

The Dynamic Properties of Annular Gas Squeeze Film Dampers

The step jump method is used to characterize the stiffness and damping of flat-faced gas lubricated squeeze film dampers. Analytic solution of a linearized form of the isothermal and compressible Reynolds equation yields closed form expressions for the step and frequency responses of the gas film. Results from the step jump method obtained both analytically and numerically are shown to be good approximations of the gas film stiffness and damping. A Prony series is proven to be an effective constitutive model capable of representing the stiffness and damping of the gas film in both the time and frequency domains in analytic form. Using the analytic constitutive model, closed form solutions for the motion of squeeze film dampers are now possible.     

Additive Mechanism Investigation of Perfluoropolyether Lubricants with a Phosphazene Additive

The tribological characteristics of magnetic thin film media coated with perfluoropolyether (PFPE) lubricants (ZDOL and AM300J) and a phosphazene additive (X-IP) were investigated in this study. The drag test results show that under ambient and hot/wet conditions the media coated with AM300J lubricant have higher retention on the test track than those coated with ZDOL 2000 PFPE lubricant. The phosphazene additive X-IP was observed to strongly anchored to the surface and was not as easily removed as PFPE lubricants alone. The retention characteristics of X-IP are independent of either AM or ZDOL. Secondary Ion Mass Spectroscopy (SIMS) depth profile data and Angle-Resolved X-Ray Photo-electron Spectroscopy (XPS) reveal that X-IP molecules were distributed near the disk surface in the X-IP and PFPE lubricants mixed layer, indicating a strong bonding/adhesion of X-IP to the disk surface. Together with the drag testing data, the authors conclude that the preferential distribution of X-IP close to the disk surface in the mixed layer helps to improve lubricant retention performance at the head-disk interface.     

Erosion Debris Particle Observations and the Micromachining Mechanism of Erosion

Erosion debris particles produced by particle impact erosion of pure Ni and a stainless steel have been examined in the scanning electron microscope for the purpose of determining whether micro-machining is an operative mechanism of erosion by alumina particles. Macroscopic machining chips generally exhibit well-defined lamellae on the side of the chip away from the tool face, and such lamellae are also observed in micromachining chips produced by abrasion or scratch testing. The aspect ratio of such chips is generally large. In the present work, the aspect ratios and shapes of erosion debris particles formed at angles of incidence below the peak erosion angle (α_c) were generally consistent with the dimensions of the impact craters formed on the eroded surface and with the hypothesis that they were formed by micromachining. However, most of the debris particles did not exhibit characteristic lamellae. This may be explained by the fact that the surface from which they are formed is very rough even on a scale similar to the size of the debris particles. This is not true in abrasion: Micromachining chips formed from such a surface would be expected to have surfaces which would obscure the existence of lamellae. However, some chips would be expected to come from the few relatively smooth areas of the surface, and these should show lamellae. Examples of such chips were, indeed, found, and micrographs of these chips are nearly indistinguishable from micrographs of micromachining chips formed by abrasion or scratch tests. It is concluded that micromachining is an operative mechanism of erosion which is of greatest importance at low angles of incidence. Debris particles formed at higher angles of incidence are generally more platelike.     

Analysis and Assessment of Agrimonia Pilosa Ledeb from Different Sources Using FT-IR Spectroscopy

To get the IR spectrums of Agrimonia Pilosa Ledeb (APL) from China and Japan areas,and to find out the characters of IR spectrums through the content of different chemical constituents,to provide a fast and effective analysis method monitor the inherent qualities of traditional Chinese medicine-APL.Fourier Transform Infrared Spectroscopy(FT-IR) was applied to detect sample of APL from China and Japan areas.This study showed that the IR spectra of APL from China and Japan areas have their unique IR fingerprint features.The contents of tannin and calcium phosphate in APL from China is different APL from Japan.So FT-IR is a very quick,effective and well repetitive method for monitoring and distinguishing the traditional Chinese medicine.     

Promotion of Anti-Wear Property of Sodium Stearate by Oxygen and Surface Active Agents

The anti-wear properties of a water-based lubricant were studied using a newly designed friction tester which enabled the rubbing with nascent surface under controlled atmospheres. Sodium stearate considerably reduced the wear of steel in oxygen rich atmospheres.

Supplementary adsorption tests were performed to identify the anti-wear film formed on the rubbed surface. Surface analysis by Fourier transform infrared spectroscopy (FTIR) revealed that metal stearate film was heavily formed on the rubbed surface in oxygen rich atmospheres. The measurement of metal elements in the protective film by atomic absorption spectroscopy clarified that the main constituent of the film was iron stearate. These results of adsorption tests could support that iron stearate might prevent the wear of steel in the wear test.

It was observed that a surface active agent prevented the formation of lubricative oxide film, but when used with sodium stearate, it synergistically promoted the anti-wear property of sodium stearate. This was attributed to the fact that the surface active agent improved the permeability of recrystallized sodium stearate to the rubbing area.     

不同产地蜜蜡及合成树脂的红外光谱和成分研究

市面上蜜蜡产地主要为波罗的海、缅甸,近年来出现一种外观似天然蜜蜡的合成树脂。本研究使用傅里叶变换红外光谱仪及Elementar vario cube元素分析仪测量了缅甸、波罗的海蜜蜡和合成树脂,分析其红外光谱差异及C、H、N、S元素含量差异,结果表明:缅甸蜜蜡的特征红外吸收在1223cm^(-1),波罗的海蜜蜡则是1258cm^(-1)附近宽而缓的吸收肩峰与1155cm^(-1)的尖峰,合成树脂则显示多种有机吸收峰,与天然蜜蜡明显不同。合成树脂N含量高于天然蜜蜡,C和H含量低于天然蜜蜡。缅甸蜜蜡、波罗的海蜜蜡及合成树脂的C、O质量分数和C、H质量分数具有很好的分区性及相关性,从化学成分上解决了产地和仿制品鉴别难点。     

Proposal of an FTIR Methodology to Monitor Oxidation Level in Used Engine Oils: Effects of Thermal Degradation and Fuel Dilution

This article describes a procedure, based on ASTM standards D7214 and E2412, that has been defined to improve quantification of oil oxidation in used engine oils. Taking into account typical problems that can be found in this type of sample, including thermal oxidation and fuel dilution, Fourier transform infrared (FTIR) spectra were analyzed also considering the effect of the oil formulation. Two zones were considered inside the typical wavenumber range for quantification of oxidation, where those problems can be detected and assessed more easily: zone A between 1725 and 1650 cm^?1, where the main oxidation products, such as aldehydes, carboxylic acids, and ketones, occur due to thermal degradation of the oil; and zone B between 1770 and 1725 cm^?1, where esters due to potential biodiesel dilution problems are detected.     

Experimental and Molecular Dynamics Simulations of Tribochemical Reactions with ZDDP: Zinc Phosphate–Iron Oxide Reaction

Zinc phosphate glass is considered to be the main constituent of tribofilms generated under boundary lubrication with zinc dialkyldithiophosphate (ZDDP), a well-known antiwear additive. The reaction occurring during friction between zinc phosphate glasses and steel native iron oxide layer is investigated by both an experimental approach and by Molecular Dynamics simulations (MD). The importance of this “tribochemical” reaction in the general ZDDP antiwear process is discussed.     

VIRR/FY-3A分裂窗波段与AIRS/AQUA和IASI/METOP-A数据的交叉辐射定标

实际应用显示搭载在风云三号A星(FY-3A)上的可见光红外扫描辐射计(VIRR)的两个分裂窗波段(IR4,~10.8μm;IR5,~12.0μm)存在定标偏差。本文选择高光谱卷积法,用AQUA卫星搭载的大气红外探空仪(AIRS/AQUA)和METOP-A卫星搭载的干涉式红外大气探测仪(IASI/METOP-A)的观测数据对VIRR/FY-3A的两个分裂窗波段进行交叉辐射定标。根据卫星轨道特点,选择北极地区(60°N~90°N,180°W~180°E)作为研究区域,并选择2010年6月、9月、12月以及2011年3月作为研究时间段。首先,分别将AIRS/AQUA和IASI/METOP-A数据与VIRR/FY-3A的第4波段和第5波段的光谱响应函数进行卷积;对观测数据进行重采样,并基于普朗克黑体辐射公式实现辐射值和亮度温度之间的转换。然后,使用两个相关的匹配条件提取VIRR/FY-3A分别与AIRS/AQUA、IASI/METOP-A在第4波段和第5波段的匹配观测点对。最后,对匹配观测点对进行回归分析,得到交叉辐射定标偏差订正方程的系数。结果表明AIRS/AQUA和IASI/METOP-A的在轨辐射定标非常一致。以AIRS/AQUA和IASI/METOP-A波段的辐射定标为标准,VIRR/FY-3A第4波段的平均定标偏差分别为2.39K和2.06K,第5波段的平均定标偏差分别为0.59K和0.44K。实验指出定标偏差与亮度温度有关。     

高压内啮合齿轮泵的三维CFD数值计算与试验研究

由于内啮合齿轮泵特殊的工作原理,其计算模型涉及微小间隙的问题和动网格的运用,计算复杂,难度较大。同时,内啮合齿轮泵在高压工作状态下,内部泄漏量较大,数值计算的精度难以保证。基于此,本文采用流体力学软件FLUENT,基于2.5D动网格技术建立了适合于高压内啮合齿轮泵的三维流体数值计算模型,对内啮合齿轮泵的流动性能进行分析。为提高高压工况下内啮合齿轮泵的CFD数值计算精度,在内啮合齿轮泵的三维数值计算模型中,利用粘性壁面边界条件的方法,模拟两齿轮之间的接触啮合,全面分析两齿轮的啮合点对数值计算结果的影响,并与试验结果进行比较。结果表明:本文提出的模型可以较好地预测内啮合齿轮泵在高压工况下的流动特性,并可为齿轮泵的数值计算提供参考。     

近红外技术快速测定裂解焦油芳烃含量

针对常用的气相色谱(GC)分析法进行焦油芳烃检测分析周期较长的问题,本文用傅里叶变换型近红外光谱仪及相关软件对石脑油蒸汽裂解焦油芳烃的含量进行了测定和实验研究。考虑焦油样品颜色差异大、芳烃含量变化大,实验通过对样品管改进、异常值判断、建模波段及光谱预处理方法优选等优化了碳六、碳七、碳八、碳九、碳十及总芳烃含量6组预测模型性能,建立了石脑油蒸汽裂解焦油样品中芳烃含量的快速分析方法,使得单个样品的分析时间缩短到2min以内。优化后6组模型的相关系数(R)分别为0.995 20,0.993 08,0.946 33,0.978 99,0.948 46,0.998 63,交叉验证均方差(RMSECV)分别为1.07,0.806,2.17,0.979,0.665,1.15。未知样6组芳烃含量的近红外光谱及气相色谱(GC)分析数据吻合良好,t-检验绝对值均小于其临界t值(t0.05(17)=2.11)。另外,近红外分析数据相对标准偏差(RSD)均小于2%,显示提出的方法具有较好的重复性。     

Atomic Force Microscopy and Raman Spectroscopy Investigation of Additive Interactions Responsible for Anti-Wear Film Formation in a Lubricated Contact

Rational formulation of lubricants requires an understanding of additive interactions that impact antiwear film qualities such as thickness, topography, and friction. In an effort to understand the complex additive interactions responsible for formation of anti-wear and friction-reducing films, atomic force microscopy (AFM) in conjunction with Raman microscopy has been used to conduct a nanoscale investigation of the wear tracks formed by a high-frequency reciprocating rig (HFRR) in the presence of various commercial lubricant additives combinations. Of the additives examined, zinc dithiophosphate (ZnDTP)-based additives are found to be solely responsible for the formation of a thick (hundreds of nm) film that exhibits a pitted topography. Addition of a molybdenum-based friction modifier to the lubricant blend reduces the film thickness considerably and reacts to produce MoS ₂ on the surface, suggesting an interaction with the zinc dithiophosphate–based additive that prevents antiwear film formation. Formation of MoS ₂ , found only in the wear track, is consistent with a dramatic reduction of friction coefficient measured in the HFRR. Subsequent addition of borated dispersants to the lubricant reveals a further reduction in friction coefficient and a modest return of anti-wear film. However, addition of detergents to the formulation increases the friction coefficient and also promotes the formation of an anti-wear film. Nanoindentation measurements on the bulk properties of the anti-wear films determined that all of the anti-wear films had similar modulus and hardness measurements which were lower than that of the parent steel material, but did not correlate with the friction measurements obtained from the HFRR. This indicates that nanoscale measurements on material properties of the film are necessary to elucidate friction properties of the interface, and that these properties cannot be determined from macroscale measurements on the bulk film.

     

Antiwear Behavior of ZDDP and Fluorinated ZDDP in the Presence of Alkylated Diphenyl Amine Antioxidants

Environmental regulations have called for a reduction of phosphorus content in engine oils in recent years. The anti-wear additive zinc dialkyl dithiophosphate (ZDDP), which is also an antioxidant, is one of the most important components of engine oil additives. ZDDP is a major source of phosphorus. One way to reduce phosphorus levels is to replace ZDDP with new environmentally friendly antiwear agents that have similar or superior wear performance compared to ZDDP. Another way to address the environmental issue is to reduce the amount of ZDDP in engine oils. At the same time, it is necessary to increase the efficiency of ZDDP by finding optimum conditions that would result in improved antiwear performance. The antiwear mechanism of ZDDP involves its degradation thermally and tribologically, leading to the formation of an antiwear film that consists of polyphosphates and sulphides. The structure of the antiwear film is almost similar in both types of degradation. But the breakdown efficiency of ZDDP is diminished by the parallel reaction of ZDDP with other additives, as well as the antagonistic effects of these additives. The new fluorinated ZDDP complex developed has shown better wear performance compared to ZDDP. This would allow the possibility of further reduction of phosphorus in engine oils compared to current levels. In this paper we study the interaction of ZDDP and fluorinated ZDDP with alkylated diphenylamine. The impact of antioxidant on wear performance was examined using a ball-on-cylinder tribometer. The interactions between ZDDP and the fluorinated ZDDP with the antioxidant were studied using NMR and the surface of the tribofilm was examined using SEM, TEM, and Auger spectroscopy.     

Theoretical and Experimental Studies of Ultraprecision Machining of Brittle Materials with Ultrasonic Vibration

Ductile machining of brittle materials, even at a high critical depth-of-cut, has been realised by applying ultrasonic vibration to a diamond tool tip. A surface roughness Ra of 100 nm at a 2 μm depth-of-cut was achieved. A discussion on fundamental principles of ultrasonic machining, the material removal mechanism and the calculation of critical factors are presented in this paper.     

三视场红外地球敏感器导航算法数值分析及实验研究

红外地球敏感器广泛运用空间飞行器,尤其是在地球轨道附近。目前最新的静态地球敏感器使用焦平面探测器来覆盖整个地球红外辐射圆。若面向飞行在70km-100km处的临近空间飞行器,他们就需要有很大的视场(>120°)且相对分辨率很低。本文针对临近空间飞行器的天文导航运用,采用线阵CCD作为探测器,设计了一个三视场红外地球敏感器。他们按照二维角度均匀分布以确保每个光学头能够均匀的指向地球红外辐射圆上。每个CCD覆盖20°以便能够精确地分辨地球辐射和空间的边界点。综合考虑地球辐射模型和地球扁率等因素,利用地球敏感器观测的向量可以获得地心矢量和飞行高度。以70-100km飞行高度为示例,建立相应的数学模型,同时提出了相应的姿态和高度确定算法并进行了仿真。综上述分析,研制了一套三视场地球敏感器原理样机并进行相关测试。仿真和实验结果表明：高度测量精度优于200m,姿态测量精度优于0.002°。     

辐射板强化喷管换热与红外抑制效果试验研究

试验研究了在发动机喷管中加装金属辐射板前后,喷管壁面温度、热喷流温度与喷管红外辐射特征的变化。结果表明,加装金属辐射板后,热喷流与喷管壁面之间的热量传递显著增强,热喷流中心温度降低,壁面温度明显升高,在90°方向上,热喷流3～5μm波段的红外辐射强度降低了38.5%。文中从热喷流、喷管壁面以及金属辐射板等相关部件的温度变化情况对红外辐射强度的变化原因进行了解释。      

Experimental and Simulation Studies on the Solid-Particle Erosion of WC-MgO Composites

This article reports our recent studies on WC-4.3 wt% MgO composites with a particular interest in the effect of grain-growth inhibitors (VC and Cr₃C₂) addition on its resistance to erosive wear. It is shown that the maximum erosion rate of the WC-MgO composite occurred at an impingement angle of 90°. With the addition of the grain-growth inhibitors (0.25 wt% VC and 0.25 wt% Cr₃C₂), the erosion resistance increased, particularly profound at the impingement angle of 90°, due to refined microstructures with improved mechanical properties. In addition, computational simulation based on a microscale dynamic model was conducted to investigate the effects of the grain boundary strength and grain size on the erosion resistance of the WC-MgO composites in order to better understand the microstructural effect on the erosive performance of the composites. It is demonstrated that the grain refinement with weak grain boundary strength has a negative effect on the erosion resistance.