The effect of lubricants and additives on the tribological performance of solids. Part 1. Passive friction control

The paper presents an analysis of the state of the art in research into the effect of the composition of lubricants and additives of various origin on the friction of solids. It is shown that the combined application of additives with various structure, including those containing nanomaterials, is most effective from the viewpoint of lubricity. The objective is to attain an ordered state of lubricating films with a low shear strength in the friction zone.     

An investigation of the transfer film characteristics and the tribological behaviors of polyphenylene sulfide composites in sliding against tool steel

The effect of CuS, CuO, CaF₂, and ZnF₂ fillers in particulate sizes of 200–350 mesh on the friction and wear behavior of polyphenylene sulfide (PPS) was investigated. The filler proportion studied was 35 vol.%. The specimens which were prepared by compression molding were tested for friction and wear in a pin-on-disc configuration using hardened tool steel disc as the counterface. The morphologies of the worn surfaces and the transfer films were studied by scanning electron microscopy and the transfer films were analyzed by energy dispersive spectroscopy. The improvement in wear resistance with CuS was considerable and with CuO marginal, while the wear resistance decreased with CaF₂ and ZnF₂. The coefficient of friction increased significantly with CuO and decreased with CaF₂ and was not significantly affected by the other fillers. The changes in the friction and wear behaviors were analyzed in terms of the morphology and the composition of transfer films.     

The tribological study of S-(1H-Benzotriazol-1-yl) methyl N,N-dialkyldithiocarbamates as additives in synthetic lubricants

The load-carrying capacity, wear, and friction properties of four S-(1 H-Benzotriazol-1-yl)methyl N,N-dialkyldithiocarbamates added to a synthetic lubricant (diester) were evaluated using a four-ball test machine and an Optimal SRV tester. The results indicate that these compounds added to the diester possess good load-carrying capacities and antiwear properties. The rubbed surfaces were investigated using X-ray photoelectron spectroscopy (XPS) analysis and the antiwear mechanism is discussed.     

Effect of lubricants and additives on the tribological performance of solids. Part 2. Active friction control

The paper presents an analysis of the state of the art in the study of the effect of magnetic and electric fields on lubrication and active control over the friction of solids. The lubricity of magnetic and electrorheological fluids is shown to depend greatly on the properties and component composition of fillers and to be related to the provision of the required rheological characteristics (varying over a wide range), which affect the lubricating film thickness. It is noted that the application of structural-sensitive LC systems and materials in joints is a promising method for the active and effective control over their friction.     

Comparative study of the tribological properties of ionic liquids as additives of the attapulgite and bentone greases

Three kinds of ionic liquids (1‐butyl‐3‐methylimidazolium hexafluorophosphate (L‐P104), 1‐hexyl‐3‐methyl imidazolium hexafluorophosphate (L‐P106) and 1‐octyl‐3‐methylimidazolium tetrafluoroborate (LB108)) were added to the attapulgite base grease and the bentone base grease to investigate and compare the tribological behaviours of the ionic liquids with the two base greases at room temperature and 150°C. Tribological tests were performed using a ball‐on‐plate reciprocating tribometer. The attapulgite base grease showed better wear resistance properties than that of bentone base grease by adding ionic liquids as additives. At same time, the attapulgite base grease showed excellent friction‐reducing and wear resistance properties at high temperature (150°C). Also, we discussed the tribological mechanism of the attapulgite base grease at both room temperature and 150°C from the aspect of the structure of the grease thicker. Copyright © 2012 John Wiley & Sons, Ltd.     

A study of the tribological behaviour of heterocyclic derivatives as additives in rape seed oil and mineral oil

The tribological properties of two novel heterocyclic derivatives as additives in rape seed oil and in mineral oil were investigated using a four‐ball machine. The morphologies and chemical features of the worn steel surfaces were observed and examined by means of X‐ray photoelectron spectroscopy and scanning electron microscopy. Both heterocyclic compounds improved the load‐carrying and extreme‐pressure capacities and the friction‐reducing and antiwear properties of rape seed oil more than they improved those of the mineral oil. Surface analyses of the rubbed surfaces revealed the formation of a protective film containing FeSO₄, organosulphur compound, FeS₂, polymerised ester, and organonitrogen compound when the surfaces were lubricated by rape seed oil containing the additives. The protective film formed during sliding processes contributed to the increase in the wear resistance.     

山东某稀土矿区成人头发中15种稀土元素含量及分布特征初探

本研究以头发中的稀土含量和分布特征作为暴露的生物标志物,选用ICP-MS分析法,对矿区和对照区两村长期居住的农民头发进行15种稀土元素的含量研究。结果表明:矿区发样中各稀土元素的中位数(ng/g)为:La(124.9)、Ce(269.2)、Pr(21.4)、Nd(77.2)、Sm(9.3)、Eu(2.5)和Gd(8.4)均高于对照村(p<0.01),其余重稀土元素虽亦有稍高的趋势,但差异无统计学显著性。全部发样的稀土分布模式均为轻稀土富集重稀土亏损型(LaN/SmN>1和GdN/YbN>1),矿区发样轻稀土富集程度平均高出对照村3倍(p 0.01)。     

An investigation of the effects of some motor oil additives on the friction and wear behaviour of oil-soluble organomolybdenum compounds

The compatibility of oil-soluble organomolybdenum compounds with some motor oil additives (detergent, dispersant, rust inhibitor and ZDDP) has been investigated on a four-ball machine and a SRV tester. Preliminary results indicated that a combination of two agents might have either synergistic or antagonistic effects on the friction and wear performance of the organomolybdenum compounds, although many combinations were shown to be synergistic. The interactions between two agents were primarily determined by the additive types, additive concentrations and test temperatures. It was also found that the presence of calcium sulphonate detergent was particularly beneficial to molybdenum dithiophos-phate and molybdenum dithiocarbamate in terms of friction reduction and wear reduction at temperatures in a certain range. The induction period of the organomolybdenum compounds was also reduced. Surface analysis results suggested that the synergistic effects were closely related to the formation of thick films, which were rich in molybdenum and sulphur, on rubbing surfaces.     

Friction and wear behaviors of a (Ca, Mg)-sialon/SAE 52100 steel pair under the lubrication of various polyols as water-based lubricating additives

The friction and wear behaviors of (Ca, Mg)-sialon/SAE 52100 steel pair under the lubrication of water or various polyol aqueous solutions were investigated with an SRV friction and wear tester in a ball-on-disc configuration. This was conducted to simulate the effect of polyols as aqueous additive in machining sialon ceramic. The morphologies of and elemental distributions in the worn surfaces of the lubricated sialon ceramics and counterpart steel were observed and determined with scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). All solutions of the tested polyols decreased the friction coefficient of (Ca, Mg)-sialon/SAE 52100 steel effectively and increased the wear volume loss of (Ca, Mg)-sialon to some extent as compared with dry sliding. The friction coefficients under the lubrication of distilled water and various polyols aqueous solutions of polyols showed almost no difference, and propanetriol was found to be the most effective for machining (Ca, Mg)-sialon with the concentration of polyols in water fixed as 5 wt%. The friction coefficients under the lubrication of propanetriol aqueous solutions in varied concentrations are closely related with the concentration, which came to the lowest value of 0.04 at a concentration of 75%. The friction-reducing performance of the polyols as additives in water was roughly correlated with their wetting behaviors on the sialon ceramic surface. In other words, the higher the wetting ability is, the lower the friction coefficients will be. Moreover, the wear volume losses of (Ca, Mg)-sialon also varied with the variation in the concentration of propanetriol in water. Accounting for the friction-reduction and wear behavior, 20% concentration of propanetriol in water could be recommended for machining (Ca, Mg)-sialon. Electron microscopic analysis indicates that polyols as additives in water enhanced the corrosive wear of sialon ceramic, which could be beneficial for increasing the machining efficiency. There existed interactions among water, polyols and sialon surfaces, which were dependent on the compositions of the lubricant solution. This accounts for the variations in the friction and wear behaviors with the concentration of polyols in water.     

An experimental study on the flow and heat transfer characteristics of an impinging jet

The flow and heat transfer characteristics of an impinging jet is investigated in two major stages. The first stage is about the investigation of the three dimensional mean flow and the turbulent flow quantities in free jet, stagnation and wall jet region. After a complete documentation of the flow field, the convective heat transfer coefficient distributions on the impingement plate are presented, during the second stage of the study. Heat transfer experiments using the new hue-capturing technique result in high resolution wall heating rate distributions. The technique is fully automated using a true color image processing system. The present heat transfer results are discussed in detail in terms of the flow characteristics. The measurements from the new method are compared with conventional heat flux sensors located on the same model. These heat transfer distributions are also compared with other studies available from the literature. The new non-intrusive heat transfer method is highly effective in obtaining high resolution heat transfer maps with good accuracy.     

Study of tribological performance of ECR-CVD diamond-like carbon coatings on steel substrates: Part 1. The effect of processing parameters and operating conditions

Diamond-like carbon (DLC) coatings were prepared on AISI 440C steel substrates at room temperature by electron cyclotron resonance chemical vapor deposition (ECR-CVD) process in C₂H₂/Ar plasma. Using the designed Ti/TiN/TiCN/TiC interfacial transition layers, relatively thick DLC coatings (1-2 μm) were successfully prepared on the steel substrates. The friction and wear performance of the DLC coatings was evaluated by ball-on-disk tribometry using a steel counterbody at various normal loads (1-10 N) and sliding speeds (2-15 cm/s). By optimizing the deposition parameters such as negative bias voltage, DLC coatings with hardness up to 30 GPa and friction coefficients lower than 0.15 against the 100Cr6 steel ball could be obtained. The friction coefficient was maintained for 100,000 cycles (∼2.2 km) of dry sliding in ambient environments. In addition, the specific wear rates of the coatings were found to be extremely low (∼10⁻⁸ mm³/Nm); at the same time, the ball wear rates were one order of magnitude lower. The influences of the processing parameters and the sliding conditions were determined, and the frictional behavior of the coatings was discussed. It has been found that higher normal loads or sliding speeds reduced the wear rates of the coatings. Therefore, it is feasible to prepare hard and highly adherent DLC coatings with low friction coefficient and low wear rate on engineering steel substrates by the ECR-CVD process. The excellent tribological performance of DLC coatings enables their industrial applications as wear-resistant solid lubricants on sliding parts.     

ICP-MS法在国标小麦GBW08503和人发GBW09101中稀土元素定值研究中的应用

本工作采用混酸(HNO_3+HClO_4)溶样方法,选择了仪器工作参数和待测同位素,研究了氧化物干扰与校正方法,采用Re作内标元素,对基体效应进行了补偿,用标准加入回收法验证了方法的准确性。从而建立了为两种标准物质定值分析的ICP-MS法,按照JJG 1006-94技术规范在严格质控条件下,提供了15种超痕量稀土元素的测定结果并检验了其均匀性和稳定性。     

An experimental investigation into the comparison of the performance characteristics of TiN and ZrN coatings on split point drills using the static and stochastic models of the force system as a signature

This paper presents a comparison of the performance characteristics of TiN (Titanium nitride) and ZrN (Zirconium nitride) coatings on split point drills. The objective of this work was to choose the better coating for machining tough materials like INCONEL. This leads to an increased productivity of drilling holes in certain components of environmental control systems and fuel control systems (in aerospace industry) made of tough materials like INCONEL. The comparison of the performance characteristics was based on the measurement of the mean values and dynamic fluctuations of the cutting force and the number of holes drilled under the same optimum machining conditions. The measurements were carried out using two specially designed piezoelectric dynamometers. The dynamometer was calibrated from static and dynamic outputs and techniques were employed for increasing the measuring accuracy and reducing the cross interference by obtaining the elements of the tranfer function. Power spectrum plots of the drift force, axial force and torque were obtained so that these plots may be used as a signature. Results show that the ZrN coating is better than the TiN coating because (a) the mean values of the axialforce, drift force and torque are smaller, thus improving the roundness, (b) the dynamic flutuations of the forces and torque about the mean are smaller thus improving the surface quality of the holes produced, (c) the number of holes before the failure of the drill is about three times more for a ZrN coated split point drill as compared to a TiN coated drill.     

The measurement of blood flow waveforms from X-ray angiography. Part 1: Principles of the method and preliminary validation.

The principles and implementation of a method for measurement of blood flow waveforms from X-ray angiography are described. Contrast medium mass values are obtained at multitudinous positions along individual vessels and from numerous images in a time sequence. These values are represented as a matrix of grey levels in a parametric image. This image is normalized to represent contrast medium concentration, and the movement over time of isoconcentration portions of the contrast bolus is recovered to determine blood flow. Preliminary validation has been undertaken using parametric images generated in two ways: synthesis from a computer model of vascular pulsatile flow and analysis of cine-angiograms of physical models (plastic and perspex tubes) carrying known pulsatile flows. Two distinct methods for interrogation of parametric images by digital image processing were employed; both provided accurate flow measurements.     

Compliant layer bearings in artificial joints. Part 1: the effects of different manufacturing techniques on the interface strength between an elastomeric layer and a rigid substrate

The premise that elastomeric materials could be used as one or more of the articulating components in both hip and knee prostheses was postulated first by Unsworth and co-workers. It was thought that such materials might have the capacity to mimic natural joint behaviour more closely than the more rigid bearing surfaces commonly in use. A more natural joint function in artificial joints should promote better tribology, with full fluid-film lubrication being the goal. Early tests showed that this objective could potentially be achieved with a judicious choice of materials and carefully controlled manufacturing techniques. This paper (Part 1 of a two-part series) describes and explains the techniques used to verify the material selection as well as to determine the most appropriate manufacturing procedure to obtain a strong and robust interface between the support and bearing material of the prosthesis. Two polycarbonate urethane (PU) materials with different hardness values (Corethane 80A and Corethane 75D) gave sufficient interfacial strength when moulded under optimum conditions. Corethane 80A was used as the soft bearing material while Corethane 75D provided the rigid backing component. Peel tests revealed strong interface bonds, varying with processing conditions between 350 and 862 N. Fourier transform infrared spectroscopy and micro-thermal analysis showed that a fusion bond over 30 microm thick formed at the interface. The results of the range of tests and analyses, which have been used in this study, have provided sufficient evidence to validate the process used to manufacture these components.