Critical conditions for wear in pivoted follower valve train systems

There are numerous wear problems associated with the use of pivoted cam follower valve train systems in modern high-speed automotive engines. These problems have led to the introduction of an increasing number of engines of this type as specification tests to assess the antiwear performance of lubricants. Critical conditions for wear in these systems have been identified by the application of a steady-wear process model to the kinematic analysis of the cam/follower contact cycle. The positions of maximum wear identified by this technique showed better agreement with worn engine components than the more commonly used criteria of maximum contact pressure and oil film thickness.     

Wear of aluminium bronze on steel under conditions of boundary lubrication

An investigation was conducted to examine the wear of aluminium bronze against tool steel when lubricated under a boundary lubrication regime by aviation kerosene, both with and without the inclusion of a commercially available boundary additive. The objective was to isolate the mechanisms of boundary film formation, protection and wear of the metal surfaces, through mechanical measurements and analyses of surfaces and debris.A model is proposed to explain these mechanisms in terms of material transfer and subsequent competing reactions between dissolved oxygen and long chain hydrocarbon acid molecules, and the metal surface.     

The effects of engine oil additives on valve train wear

Preventing valve train wear in automotive engines is one of the most important properties of an engine oil. However, the influence of engine oil additives on valve train wear has not been sufficiently clarified. In this investigation, the antiwear performance of additives (such as ashless dispersants, metallic detergents and zinc dithiophosphate - ZDTP) and the influence of the interaction of the additives were evaluated. Secondly, metallic detergents were considered. An overbased calcium sulphonate and an overbased phenate were found to have good anti-scuffing performance when evaluated in engine tests and in Falex wear tests. However, from the results of four-ball tests, these additives did not appear to have many extreme pressure properties. From surface analyses, it was determined that a calcium carbonate film was formed on the sliding surface of the Falex test piece, and this film provided good protection against wear. Finally, the interaction of ZDTP, succinimides and calcium detergents and their influence on valve train wear were studied. The decomosition temperature of ZDTP increased with certain additives. including the succinimide. As a result, scuffing was more prone, at temperatures below those increased temperatures. Also, changes in additive concentration on the sliding surface, due to competitive adsorption, altered the antiwear performance of the oil.     

内燃机配气机构噪声控制

为降低内燃机配气机构振动噪声,以某125型摩托车发动机配气机构为研究对象,利用高次多项式对凸轮型线进行优化设计.配气机构多体动力学仿真表明:优化后的配气机构没有出现飞脱和反跳现象,进、排气气门丰满程度有所增加,在各个转速下,气门的最大振动加速度降低了65%左右,气门与摇臂的撞击力有所降低,且气门与气门座间的撞击力明显下降.在此基础上,制作了凸轮样件并对优化前后配气机构进行声功率测试试验.结果表明:在测量转速范围内声功率级均降低1.5～2dB.     

4102BG型柴油机配气机构动力学计算

传统的配气机构动力学计算把各部件之间的连接看做是刚性的,这样的计算结果比较理想化,但不符合实际工作情况。为了分析配气机构的实际工作情况,本文对配气机构的弹性变形进行了研究。在考虑机构弹性变形的基础上,建立了4102BG型柴油机配气机构的数学模型,并给出了相应的运动微分方程。基于函数凸轮的不连续性,采用分段计算方法对该振动微分方程进行了求解,完成了对该柴油机配气机构的动力学计算。计算结果与实测结果十分接近,所以可以推断出数学模型的建立及计算方法是正确的。     

The energy pulse: A new wear criterion and its relevance to wear in gear teeth and automotive engine valve trains

The paper follows an earlier study in which the various standard test procedures for assessing the extreme pressure and anti-wear properties of lubricants were classified and evaluated in terms of a number of parameters. The significance of the frictional heating energy was apparent and a new parameter, the energy pulse, was proposed. This concept has been further developed in the present paper and applied to an analysis of contact conditions and patterns of wear in gears and valve trains.     

Tribochemistry in ceramic lubrication

Effective lubrication systems are crucial to the successful application of ceramic materials in many advanced technologies. A review is given here of the tribochemistry of ceramic lubrication, including the effects of water, water-based lubricants, hydrocarbons, additives and solid lubricants, on the friction and wear properties of ceramics, the tribochemical mechanisms of ceramics with lubricants and the wear mechanisms of ceramics. Finally, some suggestions about further study of ceramic lubrication are offered.     

Model of wear in a plain bearing under boundary lubrication

Wear in a plain bearing under boundary lubrication is described by three groups of related dimensionless numbers obtained from dimensional analysis. Experimental results verify the proposed model to a high degree of correlation     

Mechanisms of wear of metal by nitrile rubber under boundary lubrication conditions

The wear mechanisms for metal being worn by nitrile rubber under boundary lubrication conditions were investigated. We examined the surface profiles of both metal and rubber with SEM, and studied the chemical states of the elements in both surfaces with XPS. The functional groups in the rubber were analysed with FT‐IR. Under the action of shear forces, the metal lattice was disordered and new dislocations were formed; as a result, the chemical activity of the metal was increased. The macromolecular chains of the nitrile rubber and the alkane chains of the mineral oil were broken at stress concentration sites. These broken macromolecular chains produced active macromolecular free radicals, which reacted with the activated iron atoms and iron oxides, and generated a metal‐polymer film on the metal surface. This metal‐polymer film was destroyed and removed by the action of the debris on the sliding surface. Thus the rubber wore away the metal. Under boundary lubrication conditions with mineral oil, the physical processes of wear of T10 steel by nitrile rubber are microcutting and surface peeling.     

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.     

润滑系统在大型机组中的应用

润滑系统在各类机械转动设备中起着非常重要的作用,在设备的保养及维护中,都对润滑的各种参数及控制有详细的说明及应用。主要是对炼油装置大型机组的润滑系统中的主要仪表控制系统进行论述说明,从仪表方面了解润滑系统在机组中的重要作用。     

Self-lubricating polymer composites and polymer transfer film lubrication for space applications

The use of self-lubricating polymers and polymer composites in space is somewhat limited at present. In general, they are only used when other methods are inadequate. There is potential, however, for these materials to make a significant impact on future space missions, if properly utilized. This paper surveys some of the different polymers and fillers used to make self-lubricating composites. It delves into the mechanisms of composite lubrication and wear, the theory behind transfer film lubricating mechanisms, and some factors which affect polymer composite wear and transfer. In addition, some of the current space tribology application areas for self-lubricating polymer composites and polymer transfer are mentioned.     

Analysis of lubrication failure using molecular simulation

Monte Carlo simulations of chain molecules are used to study lubricant film behavior in confined regions. Lubrication failure is studied under two possible scenarios. The first is desorption of the lubricant molecules from the gap between asperities driven by equilibrium thermodynamics with increasing temperature. The second is the physical removal (squeezing out) of lubricant molecules from between asperities in close proximity due to high loads on solid asperities. Using simulations in the grand canonical and grand isostress ensembles, combinations of load and increased temperature are evaluated for their potential to thermodynamically drive the system to a lubrication failure event.     

Tribological behavior of PEEK-based materials under mixed and boundary lubrication conditions

In modern industries, more and more mechanical components are exposed to mixed and even boundary lubrication conditions, inducing fast wear and even scuffing of the motion systems. In order to enhance the lifetime and reliability of the motion systems, replacing metal–metal friction pairs by metal–polymer ones can be one of the most effective approaches. The present work focuses on tribological behavior of pure polyetheretherketone (PEEK) and a formulated PEEK composite lubricated with diesel and engine oil. It was demonstrated that in mixed and boundary lubrication regimes the structure of PEEK materials affect significantly the tribological performance. Formation of a tribofilm on the surface of metallic counterbody plays an important role on the tribological behavior of the PEEK-based materials.     

A reciprocating wear test for evaluating boundary lubrication

A reciprocating wear tester was used to investigated the nature of antiwear boundary lubrication films formed by several ZDDP additives in mineral oil. Under the test conditions examined in this work, antiwear films are relatively thick (approximately 0.1 μm), and so can be readily detected by optical microscopy. Film formation occurs after only a few centimetres of sliding on smooth hard surfaces, whereupon wear essentialy ceases. On rough surfaces, film formation does not take place until the surfaces have run-in, whereupon wear again ceases. Antiwear films did not form on steel pins softer than Rc 25, which wore by an oxidative mechanism. The extent of run-in or rough surfaces before film formation can be used as a measure of the effectiveness of an antiwear additive. Antiwear films are resistant to wear, so once formed they can provide sustained wear protection in base oil. However, antiwear films can be removed by wear in the presence of hydroperoxides, or by running against a new rough countersurface.     

锂基复合脂润滑下HIP—Si3N4／Mo50钢系统磨损试验研究

采用Timken摩擦试验机,在不同合成润滑脂润滑下,对热等静压氮化硅工陶瓷与Mo50钢系统进行了定量试验研究,并采用SEM扫描电镜对磨痕表面形貌进行了定性分析。     

Tribological behaviour of steel‐alumina sliding pairs under boundary lubrication conditions

The tribological behaviour of oil‐lubricated steel‐alumina sliding pairs was investigated using a ball‐on‐disc tribometer at room temperature. Commercial bearing balls of 10 mm diameter were mated to 99.7% Al₂O₃ discs, and additive‐free mineral oil was fed into the contact area. The sliding speed and the applied normal load were varied, and the initial surface roughness of the Al₂O₃ disc was altered using different polishing and grinding procedures. The results showed that the surface roughness of the ceramic discs dominated the tribological behaviour under the given experimental conditions. The sliding speed as well as the normal load showed less effect on the friction behaviour, but the amount of wear depended strongly on the normal load. From the results it was concluded that improvement of the surface roughness and optimised surface machining of the ceramic material can be essential for improving the tribological performance for boundary‐lubricated steel‐ceramic sliding pairs.     

稀油润滑系统的精确温控

分析大型设备稀油润滑系统的温度控制原理,重点介绍冷却器配置计算方法和调节阀的配置要点。     

供暖热网水力控制阀的选用

针对供暖热网的水力失调,介绍几种常用的调节控制阀门。并讨论这几种调节阀在不同运行模式下的调节原理和应用范围。     

Additive interaction and lubrication performance in a polar additive binary system

Additive interactions were studied between polar compounds, one of which decomposes at the frictional surface, on the lubrication performance of a binary system for polar straight chain hydrocarbons and aromatic compounds.As a comparison, an additive single component system was also studied. The lubricant performance of the blended oils was evaluated using a Falex lubricant testing machine and the adsorption characteristics of the additives on an iron surface were analysed.In the single component system, good correlation was obtained between the adsorption isotherm and the anti-seizure characteristics of the additives for both 1-octadecanol and 2-naphthol. In the binary system of 2-naphthol and 1-octadecanol, the lubrication characteristics of 2-naphthol appeared, producing heavy decomposition products of 2-naphthol because 2-naphthol was irreversibly (or chemically) adsorbed while 1-octadecanol was reversibly (or physically) adsorbed.Conversely, in the binary system of β-naphthol and stearic acid, the lubrication performance was poorer than that of the individual additive, since neither the decomposition products of the aromatics nor the adsorption film of stearic acid was sufficient against seizure. This was owing to the comparable adsorbability of the two compounds.