Analysis of antiscoring and antifriction properties of greases

The paper describes an improved electric circuit of the method for estimating the scoring resistance of greases based on contact resistance measurement. Antiscoring and antifriction properties of greases under conditions of sliding and rolling friction are studied. The critical loads for the greases under testing are determined and the grease having the best antiscoring and antifriction properties is selected.     

Biodegradable lubricants — Analysis of metalworking oils and hydraulic fluids by mass spectroscopy

Biodegradable metalworking oils and hydraulic fluids were screened for their base oil composition using a special mass spectrometric technique — direct exposure probe chemical ionisation mass spectrometry (CI(NH₃)-MS). All but one of the hydraulic fluid samples were rapeseed oil or trimethylolpropane trioleate based, the other sample being a neopentylglycol ester trimethylolpropane ester mixture. Ethylhexyl ester of rapeseed oil fatty acids (or similar) was present in some of the metalworking fluids in addition to rapeseed oil, whilst other samples were pure rapeseed oil. In several cases a trimethylolpropane/neopentylglycol ester base was found. Preliminary results for additive isolation/identification show the usefulness of preparative gel permeation chromatography.     

Formation of antiscoring properties of materials during dynamic adaptation of surface layers to operational conditions

The relationship between the antiscoring properties of tribotechnical materials, estimated according to load-carrying capacity increase during running-in, and their inclination to dynamic adaptation under loading via self-organizing processes in their surface layers is studied.     

Development of a statistical method to formulate high‐VI hydraulic oils

Mobile hydraulic equipment is often subjected to a wide range of operating temperatures, and so must be lubricated with oils with a high viscosity index (VI) in order to maximise efficiency. Formulating high‐VI hydraulic oils is a complex task that requires testing numerous intermediate blends in order to achieve the desired viscosity at both low and high temperatures. With the introduction of the ASTM D 6080 hydraulic oil classification, which defines a separate grade at low and high temperature for high‐VI oils, and further includes VI and viscosity measurements after the sonic shear test, formulating high‐VI hydraulic oils has become even more complex. In order to determine the most effective VI improver to meet a given set of viscosity requirements, a large statistically designed experiment has been carried out. Empirical equations have been obtained that can be used to model the blending efficiency of VI improvers at different temperatures and to estimate their shear stability. This paper shows how the results obtained for 42 hydraulic oils have been used to develop a computer program aimed at facilitating the formulation of high‐VI hydraulic oils.     

Elastohydrodynamic properties of water-based fire-resistant hydraulic fluids

The elastohydrodynamic (ehd) lubricating properties of commercial fire-resistant hydraulic fluids in rolling point contacts are described. Earlier work is reviewed and new work presented on water-in-oil and oil-in-water emulsions. It is shown that in general, elastohydrodynamic film thicknesses of water-in-oil emulsions are close to those of their base oils. For very fine particle size emulsions, however, thicker films are observed. Commercial oil-in-water emulsions in fully flooded conditions have not been found to give measurable elastohydrodynamic films. However, when the emulsions are destabilized, a localized pool of oil collects in the contact zone which enables ehd films to form, though these films do not survive very high rolling speeds. Polyglycol solutions give low ehd film thicknesses, approximately one third those of mineral oils of corresponding viscosity. This can be attributed to the low pressure—viscosity coefficient of these solutions.     

Boric acid and borax as antiscoring additives to glycerin-based lubricant

Boric acid and borax, which are used as antiscoring additives to an environmentally friendly glycerin-based lubricant, have been studied. It is shown that the adsorption of borax obeys the Langmuir isotherm. The equilibrium constants of the adsorption of the additives and the energy of the adsorption are estimated. It has been found that borax is a more effective antiscoring additive than boric acid. For borax used as the additive, the dependence of the coefficient of friction on the load applied to a friction unit is studied and interpreted.     

Lubricating properties of rapeseed‐based oils

Three commercially available hydraulic/transmission lubricants based on rapeseed oil have been investigated for their lubricating properties. The coefficient of friction, scuffing‐load capacity, and pitting resistance were evaluated, and the results compared with a corresponding commercial mineral‐based oil. The results showed in general a substantially lower coefficient of friction and better pitting resistance for rapeseed‐based oils than for the mineral oil. Scuffing load capacity was, with one exception, the same for all oils. As a result of lower shear stresses during contact, and a higher viscosity index, the temperatures in the gearbox were lower for the rapeseed oils tested than for the mineral oil. Insufficient antiwear behaviour at high loads was found to be a major drawback of these vegetable oils.     

Lubricating properties of rapeseed oils compared to mineral oils under a high load oscillating movement

The use of rapeseed‐based lubricating oils has become more widespread in recent years. When these oils have been tested for their tribological properties, some imperfections have been found, especially in conditions of highfrequency and low‐amplitude oscillating movements. In the present work, we compare the tribological properties of commercially available rapeseed‐ and mineral‐based oils, rapeseed and mineral base oils, and these base oils mixed with two additives for improving lubricity. The results are compared for a wide range of contact pressures.     

Improvement of antioxidation and antiwear properties of polyalphaolefin oils

Polyalphaolefin-based lubricating oils were tested on a four-ball tester, and in a stability test, with antiwear and antioxidant additives of different types, along with other (petroleum and alkylbenzene) base oils and additives. Antioxidant additives for PAOs essentially influence their thermo-oxidation stability. It was found that binary inhibitors increased thermo-oxidation stability effectively. In the antiwear tests, the addition of additives to PAOs sharply decreased wear scar diameters. A significant difference was observed in the action of small concentrations of antiwear additives as between PAO, alkylbenzene and mineral oils. Explanations of this behaviour are put forward.     

Influence of aldehydes in make-up oils on antioxidation properties

The addition of more antioxidant to aged oils is not always effective in preventing autoxidation. To investigate this phenomenon, a solution of antioxidant and model oxide in hexadecane was examined by means of the induction period method. Aldehydes were found to be the most active species for reducing the antioxidation properties of zinc dialkyldithiophosphate (ZDTP), 2,6-di(tert. butyl)-4-methylphenol (DBPC), and N-phenyl-1-naphtylamine (PNA). Carboxylic acids, ethers, alcohols, and ketones to some extent reduced the induction period with these antioxidants. Esters showed almost no influence on reducing their antioxidant properties. Reaction of ZDTP with aldehyde was studied by means of ³¹P-NMR analysis. It was found that (a) aldehydes accelerate conversion of ZDTP, and thereby reduce its antioxidant performance. (b) Conversion of ZDTP in the presence of aldehydes under oxygen at 130° in hexadecane and no reaction was observed under nitrogen at the same temperature. Active intermediates derived by the autoxidation of aldehyde were suspected. (c) Reaction of peroxycarboxylic acid with ZDTP took place smoothly at 0°C under nitrogen to give bis(dialkylthiorophosphoro)disulphide and the corresponding carboxylic acid. Reaction of hydroperoxide with ZDTP took place at room temperature to give oxo-hexa(dialkylphosphorothiorothionato)-tetrazinc. Two mechanisms for decomposition of ZDTP promoted by aldehydes, namely hydroperoxide and peroxycarboxylic acid mechanisms, are proposed. Reaction of peroxycarboxylic acid with DBPC or PNA barely took place at room temperature: for these antioxidants, the peroxycarboxylic acid mechanism would be excluded. Radical species derived by the autoxidation of aldehydes were considered as active intermediates. It is considered that classification of the types of oxides that exist in used oils in the key to optimising the effect of re-added antioxidants.     

闸门双吊点液压启闭机液压同步系统分析

双吊点液压启闭机在大中型闸门的启闭上应用广泛,针对其液压同步系统进行分析。分析了双吊点液压启闭机双缸同步误差形成的原因;介绍了双缸同步闭环控制方案;结合闸门双吊点液压启闭机液压同步控制的工程实际,分析了目前典型同步回路的工作原理及特点;最后归纳了双吊点液压启闭机同步回路的发展趋势。     

液压油对液压系统副作用分析

依据液压油变劣的特征,分析了外界环境对液压油性能影响的原因,阐述了液压油对液压系统的副作用,并提出改善措施。     

Influence of viscosity modifiers on the rheological properties of synthetic oils

The study of the effect that the molecular weight and concentration of the polymer gelling additive PMMA (polymethylmethacrylate) introduced into the synthetic base oil PAO6 has on viscosity. The empirical dependence of the viscosity of the thickened oil on the content of additives has been established and the coefficients of the thickening efficiency of additive have been determined. An experimental study of the viscosity of synthetic oils on the shear rate has been carried out at different contents of viscosity modifier PMMA with different molecular weights in a base of PAO6. The ranges of velocities have been determined at which the oil exhibits properties of non-Newtonian fluid. It has been shown that, with an increase in the molecular weight of PMMA of additive at the same concentration in its base, the non-Newtonian behavior of oil begins to emerge at lower shear rates. It has been found that the use of an acoustic arsenal of the operational control of the viscosity of lubricating oils based both on the piezoelectric and the magnetoelastic interaction is promising for the operational control of the viscosity of lubricating oils.     

Experimental analysis of tribological properties of lubricating oils with nanoparticle additives

This study examined the tribological properties of two lubricating oils, an API-SF engine oil and a Base oil, with CuO, TiO₂, and Nano-Diamond nanoparticles used as additives. The friction and wear experiments were performed using a reciprocating sliding tribotester. The experimental results show that nanoparticles, especially CuO, added to standard oils exhibit good friction-reduction and anti-wear properties. The addition of CuO nanoparticles in the API-SF engine oil and the Base oil decreased the friction coefficient by 18.4 and 5.8%, respectively, and reduced the worn scar depth by 16.7 and 78.8%, respectively, as compared to the standard oils without CuO nanoparticles. In addition, investigations were performed using TEM, OM, SEM, and EDX to interpret the possible mechanisms of anti-friction and anti-wear with nanoparticles.     

液压泵效率与排量特性试验研究

为实现工程机械液压系统的高效节能,对液压泵的效率和控制特性进行试验研究.基于液压试验台,测试了液压泵在不同压力、转速和排量下的效率,并进行了建模分析.之后对液压泵排量的动态与静态电比例控制特性进行了对比试验.研究结果表明液压泵的高效区分布于等值线图的右上角,即中高转速和排量范围内.液压泵排量控制特性基本不受转速影响,受负载压力影响较大,新旧液压泵的排量控制特性基本相同.研究为工程机械动力匹配奠定了基础.     

液压油的污染分析及其控制方法

随着国民经济的迅猛发展和科学技术的进步，起重设备对液压系统工作的灵敏性、稳定性和寿命提出了越来越高的要求，而油液污染不仅会影响系统的正常工作和使用寿命，甚至会引起设备事故。据不完全统计，由于油液污染引起的液压系统故障占总故障的70％-80％，可见要保证液压系统工作灵敏、稳定、可靠和延长液压元件使用寿命，就必须加强对液压油污染的控制，以保持液压系统良好的运行状态。     

Studying tribotechnical properties of nanostructured lubricating oils with various dispersive media

Equipment design and research procedure are described for studying magnetic and tribotechnical properties of nanodispersed magnetic media. The tribotechnical properties and functionality of nanostructured magnetic oils prepared by introduction of a magnetic filler into dispersive media that belong chemically to four classes of the most promising fluids have been studied. The effect of additives and fillers on improving the lubricating properties of magnetic oils has been analyzed.     

Analysis and quality control of aviation turbine oils

A method is described in which capillary gas chromatographic data from aviation turbine oils are processed by methods of pattern recognition based on the chemometrics systempackage ‘Ein*Sight’. It allows an automatic, objective and quantitative comparison of the base oil components of production batches. This application can be used to advantage in a control scheme based on analytical data.     

300MN模锻水压机提升管道液压冲击仿真分析

针对300MN模锻水压机加压.提升过程中提升管道液压冲击较大的问题,建立水压机水路系统的AMESim仿真模型,设定加压-提升过程主分配器轴角度由170°～5°的变化时间t为1、0.5、0.3、0.1s,仿真分析提升管道中液压冲击值为27.8、89.6、100.5、146.8bar,并得出加压一提升过程主分配器轴角度由170°～5°的变化时间、提升管道压力、以及工作缸压力之间的关系.分析结果表明:加压-提升过程主分配器轴角度由170°～5°的变化时间缩短将使工作缸卸压不充分,引起提升管道较大的液压冲击.     

液压缸运动失调的问题分析

1　前言在液压机床生产中 ,液压缸工作的可靠性和稳定性是影响零件加工质量的重要原因。特别是对于精密零件的加工 ,其加工精度和表面粗糙度是由液压系统控制下的液压缸的切削加工来达到的。为了提高液压缸的可靠性 ,不仅要使液压系统设计合理 ,还要在使用中经常调整和维护 ,要注意液压元件的优劣等。在液压系统中由于回路复杂 ,自动循环紊乱的现象经常发生 ,影响零件的加工质量 ,甚至使零件报废。产生自动循环紊乱的原因很多 ,如设计不合理、液压阀失灵、系统泄漏等。下面对在实际生产中出现的液压缸失调现象加以分析并提出解决方法。2　几…