bluuebunny/crossref_metadata_2025_split huggingface dataset:
Friction properties of perfluorinated polyethers for hot‐dipped tin low‐level separable electrical contacts
Authors: Noël S. , Lécaudé N. , Alamarguy D. , Boyer L. 
Published: July 2006

AbstractTin coatings are used as a final protection for cuprous substrates involved in low‐level electrical contacts. High friction forces and fretting phenomena remain a cause of electrical failure of connector terminals, and so should be minimised. A lubricant layer can improve the life and reliability of connector terminals but such a layer must ensure low and stable resistance values even under severe temperature conditions. Work has been undertaken to investigate the lubricant layer most suitable for the protection of tinned electrical contacts. Perfluorinated polyethers (PFPEs) were chosen for their inertness. The aim was to correlate various physico‐chemical properties of branched or linear PFPEs, with their frictional and electrical properties. The long‐term electrical properties of a contact are shown to be linked to the initial wear mode in the contact.
Theoretical characteristics of hydrodynamic journal bearings lubricated with soybean‐based oil
Authors: Mongkolwongrojn M. , Arunmetta P. 
Published: July 2006

AbstractVegetable‐based oils are not only biodegradable but also environmentally advantageous, and the range of lubrication applications offered by them continues to grow. Recently, vegetable‐based oils have been combined with synthetic esters to produce modified vegetable‐based oils.This paper presents an investigation of the theoretical characteristics of hydrodynamic journal bearings lubricated with non‐Newtonian soybean‐based oil. The soybean‐based oil was mixed with synthetic esters and silicone oil. The relationship between the shear stress and shear strain rate of the oil was obtained experimentally. The time‐dependent modified Reynolds equation including non‐Newtonian effects was formulated for short circular journal bearings. The perturbation technique was applied to the Reynolds equation to obtain zero‐ and first‐order pressure equations. The finite difference method was used to calculate the pressure distribution numerically. The static and dynamic characteristics, such as pressure distribution, Sommerfeld number, attitude angle, and spring and damping coefficients, were obtained numerically. It was found that the nonlinear factors of the non‐Newtonian soybean‐based oil strongly affected the performance characteristics of the journal bearings.
Time of exposure to lubricating liquid for predicting wear of UHMWPE in joint prostheses
Authors: Nakanishi Y. , Miyagawa H. , Higaki H. , Miura H. , Iwamoto Y. 
Published: July 2006

AbstractIt is generally agreed that contact pressure and sliding speed are the predominant factors for the prediction of wear of ultrahigh‐molecular‐weight polyethylene (UHMWPE) in joint prostheses. A new parameter for predicting the wear of UHMWPE has been introduced with a wear test in vitro. The parameter is the time of exposure to a lubricating liquid on a bearing surface. A pin‐on‐disc machine was designed such that the exposure time of a CoCrMo alloy disc to a lubricating liquid could be varied. The specific wear of UHMWPE was increased by a decrease in the exposure time, even if the contact pressure and the sliding speed were held constant. The parameter is able to account for the contact pressure set in the experiment (2.0–20.0 mPa), and clarifies the conditions under which the specific wear of UHMWPE is found to be high.
The effects of acid passivation, tricresyl phosphate presoak, and UV/ozone treatment on the tribology of perfluoropolyether‐lubricated 440C stainless steel couples
Authors: Shogrin Bradley A. , Jones William R. , Herrera‐Fierro Pilar , Jansen Mark J. 
Published: July 2006

AbstractResearch on the boundary lubrication performance of two perfluoropolyether (PFPE) thin films in the presence of passirated 440C stainless steel is presented. The study used a standard ball‐on‐disc (BoD) tribometer operating in dry nitrogen and a vacuum spiral orbit tribometer (SOT). Stainless steel surfaces were passivated using one of four techniques: a high‐temperature and low‐temperature chromic acid bath, a tricresyl phosphate (TCP) soak, or UV/ozone treatment for 15 min. After passivation, each BoD disc had a 400 Å film of Krytox® 16256 (PFPE) applied to it. The lives of these films were quantified by measuring the number of sliding cycles before an increase in friction occurred. The lubricated life of the 440C couple was not altered as a result of the various passivation techniques. The resulting surface chemistry of each passivation technique was examined using X‐ray photoelectron spectroscopy. The SOT was used to examine the effects of the TCP treatment on the lubricated life of another PFPE, Brayco® 815Z, under rolling conditions. None of the passivation techniques were found to increase dramatically the oxide film thickness or lubricated life.
The influence of lubricating fluid type on the properties of biodegradable greases
Authors: Florea Ortansa , Luca Marcel , Constantinescu Anca , Florescu Danilian 
Published: July 2006

AbstractThe lubricating ability of a grease depends on both the base oil and the thickener. As a result of their intrinsic properties and/or because of their com‐patibility with thickeners and specific additives, base fluids have different influences upon the properties of grease formulations. It is well known that mineral oils are the most widely used lubricant bases due to their inherent lubricity and lower cost, but recent environmental concern has led to consideration of the use of vegetable oils and readily biodegradable synthetic fluids as raw materials in lubricating grease formulations. As well as the base materials, the additives for biodegradable greases should also be biodegradable. This requirement limits the kind of products that may be used in environmentally friendly greases.This paper presents comparative data concerning the tribological and physico‐chemical properties of biodegradable greases formulated with certain vegetable oils, such as rape seed oil, castor oil, and soybean oil or their mixtures, and synthetic esters. The improvement of the load‐carrying properties of biodegradable greases and the antioxidative effect of some suitable additives have also been studied, and the results are presented here.
Effect of solid lubricant and fibrous reinforcement on the abrasive wear of polyamides
Authors: Rajesh J. John , Bijwe Jayashree , Tewari U. S. 
Published: July 2006

AbstractShort glass fibre‐reinforced polyamide 6 and polyamide 11 (PA 6 and PA 11) with and without a solid lubricant of polytetrafluoroethylene and metal powders (e.g., bronze) and copper as fillers were formulated and characterised for their compositional and mechanical properties. A tribological evaluation of these composites' abrasive wear was carried out by abrading a polymer pin against 80 grade (175 um) silicon carbide (SiC) paper under single‐pass conditions at various loads. It was observed that the fibre reinforcement reduced the abrasive wear resistance of virgin polymers. A combination of fibre and particulate fillers was further detrimental in this respect. Efforts were made to correlate the wear performance with the ductility factor, fracture toughness, and fracture energy in the case of PA 6 and its composites.
New citric esters with aromatic content and a complex structure considered for use as tribological fluids
Authors: Mirci L. , Boran S. , Luca P. , Boiangiu V. 
Published: July 2006

AbstractThis paper presents the results of research carried out to produce synthetic ester oils with a mixed structure, based on citric acid, with beneficial tribological properties and potential biodegradability. Two series of unsymmetrical triesters have been synthesised by varying the molar relationship between aliphatic alcohols from C1, to C13 along with an alcohol of a complex alkyl‐aryl structure, namely 2‐[(p‐nonyl)phenoxy]ethanol. The variation of the principal properties as a function of the length of the aliphatic chain introduced by the aliphatic alcohol and the aromatic content introduced by the alkyl‐aryl alcohol has been assessed. The wide range of viscosities of these triesters demonstrates their versatility, and the natural citric acid origin holds potential for their having good ecological characteristics.
The influence of application and additives on ecotoxicity and biodegradability of environmentally acceptable ester‐based lubricants
Authors: Hahn S. , Dott W. , Eisentraeger A. 
Published: July 2006

AbstractThe main advantages of lubricants based on synthetic esters are their good biodegradability and low toxicity. Most of them are classified as non‐water polluting. Also, the lubricants should be stable for a long time, while operating under varying conditions. In the work presented here ‐ part of a research projectSFB 442, University of Aachen, see acknowledgement.
to improve the ecological and technical properties of these types of lubricant by chemical modification of the base fluids, variation of the type and concentration of additives, and application of new coating technologies for tools with which the lubricants are used ‐ the effects of different operating conditions on toxicity, biodegradability, and chemical characteristics are assessed using biological and chemical methods. Water‐extractable toxicity is determined using a modified extraction technique and several bioassays, which allow one to distinguish between the toxic potential of the base fluids and that of the base fluids with additives. Biodegradability is determined using an optimised test system, changes in the chemical composition of the lubricants are quantified, and it is shown how the addition of additives, and the changes in the lubricants during use, affect the ecological characteristics.
Tribological properties of phosphate esters as additives in rape seed oil
Authors: Jiusheng Li , Wenqi Rao , Tianhui Ren , Xingguo Fu , Weimin Liu 
Published: July 2006

AbstractWith the growing concern about environmental pollution, vegetable oils have begun to be applied as base oils for environmentally friendly lubricants. Additives containing phosphorus can be used for their excellent antiwear properties and low toxicity. In view of this, a study of a series of phosphate esters as additives in rape seed oil (RSO) was carried out using a four‐ball tester. The results indicate that phosphate esters possess very good load‐carrying capacity and good antiwear and friction‐reducing properties compared with RSO by itself. Surface analysis of the worn balls was carried out using X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The tribological mechanism of the additives is discussed on the basis of the experimental results.
Lubricating properties of vegetable oils and paraffinic oils with unsaturated fatty acids under high‐contact‐pressure conditions in four‐ball tests
Authors: Murakami Teruo , Sakamoto Hiroshi 
Published: July 2006

AbstractThe tribological properties of three kinds of vegetable oils of different composition under high‐contact‐pressure conditions were evaluated in four‐ball tests to elucidate the lubrication mechanism of vegetable oils. The types of fatty acids composing the triglycerides and the concentration of dissolved oxygen appeared mainly to control the lubricating performance. Therefore, glycerol and a paraffinic oil containing fatty acids were tested as a comparison. Further, the influences of fatty acid types, antioxidant additives, and dissolved oxygen in the oils on the lubricating performance were examined. It was shown that linolenic acid with three double bonds was the most effective at higher temperature, where the formation of a friction polymer was observed, although the addition of antioxidant additives suppressed the formation of the friction polymer but reduced the load‐carrying capacity.
Tribocarbonisation of a synthetic engine oil in lubricated piston ring/cylinder bore sliding contact and its relation to friction and wear
Authors: Li S. H. , Zhang R. J. , Jin Y. S. , Wang Y. C. , Tung S. C. 
Published: July 2006

AbstractTribocarbonisation of a fully formulated synthetic engine oil, an API SJ/SAE 5W‐30 containing an organic molybdenum friction modifier, was investigated in an Optimal SRV® tribotester, with a Mo‐coated piston ring and a cast iron cylinder bore tribopair in lubricated sliding contact and under stepwise heating conditions. The friction characteristics were determined by the friction coefficient curve which showed that two local minimum values occurred as the temperature increased stepwise. The local minimum friction coefficient at the lower temperature of 290°C was the result of the formation of MoS2 and MoO3, tribochemically generated by MoDTC and ZDTP. For the other local minimum friction coefficient at the higher temperature of 400°C, FT‐IR and Raman spectroscopic examinations of the worn tracks on the cylinder bore samples indicated that tribopyrolysis of the oil components and simultaneous polycondensation into carbonaceous species had occurred. Detailed Raman analyses showed that the carbonaceous species included a disordered phase and an ordered phase characterised, respectively, by the D‐line (1370 cm−1) and G‐line (1580 cm−1). The peak positions and sizes of the graphite crystallites involved varied according to temperature, and were related to the specific points on the friction coefficient versus temperature curve. Tribochemistry could enhance pyrolysis of the oil and facilitate the production of the carbonaceous species and growth of the graphite crystallites.
Tribological performance of an ionic liquid as a lubricant for steel/aluminium contacts
Authors: Chen  , Yunxia  , Ye  , Chengfeng  , Wang  , Haizhong  , Liu  , Weimin  
Published: July 2006

AbstractThe wear and friction behaviour of an ionic liquid 1‐ethyl‐3‐hexylimidazolium tetrafluoroborate (L206) was investigated as a lubricant for steel/aluminium contacts using an Optimol SRV® oscillating friction and wear tester. The elemental composition and chemical nature of the antiwear films generated on the aluminium surface were analysed using a scanning electron microscope with a Kevex energy dispersive X‐ray analyser attachment (SEM/EDS) and X‐ray photoelectron spectroscopy (XPS). A low friction coefficient (˜0.05) was recorded when lubricating with L206; a small amount of water (5 wt. %) in L206 effectively reduced the wear volume and greatly increased the microhardness of the aluminium alloy, but had little effect on the friction coefficient. The SEM/EDS results showed that severe corrosive wear occurred on the aluminium alloy when lubricating with neat L206, which could be avoided by the addition of water in L206. The XPS results indicated that the species AlF3, Al2O3, AlO(OH), and Al(OH)3 formed during friction; there was no indication of boron on the worn surfaces.
Investigations into the epoxidation and alcoholysis of oleochemicals for use as lubricants
Authors: Hölderich W. F. , Rios L. A. , Weckes P. P. , Schuster H. 
Published: July 2006

AbstractMost lubricants and functional fluids worldwide are based on mineral oil. These fluids contain up to 10% of a wide variety of additives for the improvement of their tribological properties. Several of these are still ecologically hazardous.From an environmental point of view, the use of renewable feedstock is of great interest. In Europe rape seed oil is available in substantial amounts and its esters (triglycerides, esters with saturated or partly unsaturated acids) to some extent display better tribological properties than conventional lubricants. The aim of the work which is presented here has been to improve the stability of these types of ester and their derivatives with regard to oxidation and hydrolysis. This can be done by the addition of different carboxylic acids and alcohols, of various complexities, to the double bonds. This paper deals with the indirect addition of different alcohols, such as methanol, isobutanol, and neopentanol, to the double bond of methyl oleate, and the addition of methanol to the double bonds of glycerin trioleate using the corresponding epoxides as intermediates. The reactions were carried out with environmentally friendly heterogeneous catalysts. Several tests, such as for viscosity, oxidation stability, and biodegradability, were carried out to demonstrate the potential of these newly developed fluids for use as lubricants.
The tribological properties of several silahydrocarbons for use in space mechanisms
Authors: Jones W. R. , Jansen M. J. , Gschwender L. J. , Snyder C. E. , Sharma S. K. , Predmore R. E. , Dube M. J. 
Published: July 2006

AbstractSilahydrocarbons are members of a relatively new class of liquid lubricants with great potential for use in space mechanisms. They are unimolecular species consisting of silicon, carbon, and hydrogen. They possess unique wear, viscosity, and volatility properties while retaining the ability to solubilise conventional additives. The tribological properties of several members of this class, including tri‐, tetra‐, and penta‐compounds, are presented. These properties include viscosity‐temperature, viscosity—pressure, vapour pressure, lubricant life, traction, and reciprocating and four‐ball wear rates. Lubricant lifetimes were determined using a vacuum ball bearing simulator, the spiral orbit tribometer. Wear was measured using a Cameron Plint reciprocating tribometer and wear rates with a vacuum four‐ball tribometer. Conventional viscometry was used for viscosity—temperature measurements and a Knudsen cell for vapour pressure. Thermogravimetric analysis was also used for volatility measurements. Pressure—viscosity coefficients (α—values) were estimated from elastohydrodynamic lubrication film thickness measurements. These properties are compared to those of existing state‐of‐the‐art space lubricants.
High‐pressure rheology of eight synthetic lubricants based on phase diagrams
Authors: Rahman Md. Ziaur , Ohno Nobuyoshi 
Published: July 2006

AbstractNew sets of equations have been constructed from the density‐pressure‐temperature and viscosity‐pressure‐temperature relationships to determine the rheology of synthetic lubricants at high pressure. A phase diagram was first plotted for the oils up to a pressure of 1.2 GPa and temperatures from 303 to 353 K using high‐pressure density experimental results and others. For the oils at temperatures of 313, 333, and 353 K, the high‐pressure viscosity experiment was done up to a viscosity of 104 Pa s and up to a pressure of 0.4 GPa. A relationship, based on free volume theory, between pressure and temperature with varying density and viscosity was proposed. It was found that the new equations from these relationships could predict the high‐pressure rheology more closely than those of previous researchers. Moreover, it was shown that the Ehrenfest equation or the gradient of the phase diagram is closely related to the expansion coefficient of free volume.
Biobased dry‐film metalworking lubricants
Authors: Biresaw G. 
Published: July 2006

AbstractMetalworking lubricants must allow the manufacture of acceptable products at competitive cost without causing harm to operators or the environment. One way of attaining such a goal is through the use of biobased raw materials in lubricant formaulations. Biobased materials are generally non‐toxic, easily biodegradable, and abundantly available from renewable agricultural sources. However, successful application of biobased marterials in lubrication requires a thorough understanding of the tribochemical properties of these agricultural products. Recent studies have shown that biobased lubricants comprising starch and vegetable oils have promising lubrication properties. This paper discusses investigations into the effect of film thickness on the friction properties of dry‐film lubricants formulated from starch‐soybean oil composites.
Modification of the chemical structure of an environmentally‐friendly castor oil lubricant
Authors: Di‐Hua Tao , Bin Ye 
Published: July 2006

AbstractWidely used mineral‐oil based lubricants are often released into the environment and cause pollution. Therefore importance is attached to developing environmentally‐friendly lubricants. Vegetable oils have been used as lubricants since ancient times. These materials, similar to synthetic esters, have better biodegradability than mineral oils. They are also renewable. Vegetable oils have some shortcomings, such as a higher pour point and a lower viscosity index than synthetic esters. They have a limited viscosity range and lower oxidative stability due to the presence of unsaturated bonds. Therefore vegetable oils as such cannot satisfy all the requirements of modern machine lubrication. In this paper, the chemical structure of natural castor oil is modified by an isomerisation reaction and by extending the carbon chain, so as to lower the pour point and improve the viscosity index.The results show that structurally modified castor oil has very good lubrication characteristics. Its viscosity at 40°C is 150 mm2/s, its pour point is −40°C, and its viscosity index is improved. The antiwear and friction characteristics are better than those of mineral oil of the same viscosity and comparable to pentaerythritol esters and diisocapryl sebacate.
A study of the tribological behaviour and action mechanism of thiophosphates in rape seed oil
Authors: Weimin Liu , Qingye Gong , Wanren He 
Published: July 2006

AbstractTri‐n‐butyl phosphate and two thiophosphates, tri‐n‐butyl thiophosphate and tri‐n‐octyl thiophosphate, were synthesised. The tribological properties of the compounds as additives in rape seed oil for a steel‐steel friction pair were investigated with two four‐ball machines. The worn surfaces of the steel balls lubricated with the additive‐containing rape seed oil were analysed by means of X‐ray photoelectron spectrometry and scanning electron microscopy. Typical elemental distributions in the worn steel surfaces were analysed with an electron probe micro‐analyser. It was found that rape seed oil containing thiophosphates as additives at appropriate concentrations demonstrated better tribological properties than tri‐n‐butyl phosphate. Tribochemical reactions were found to be involved for the steel‐steel friction pair lubricated with the rape seed oil containing the synthetic phosphates, with the formation of a boundary lubricating film composed of a glyceride of the rape seed oil and the tribochemical reaction products of the additives. This is assumed to contribute to the improvement of the tribological properties of the rape seed oil base stock. The action mechanism of the additives is also discussed.
Some comments on micro‐abrasion interactions of pure metals in bio‐oils
Authors: Mathew M. T. , Stack M. M. 
Published: July 2006

AbstractAn attempt has been made to study the effect of bio‐oils on the two‐ and three‐body abrasion process of pure metals and steel. The equipment used was a micro‐abrasion tester (TE‐66, Phoenix Tribology (Plint)). The materials considered were mild steel, copper, and aluminium, being the most usable and basic materials for industrial applications such as bearings and gear assemblies. The results were used to identify transitions between wear regimes as a function of sliding speed and load. The effect on the abrasion process in the presence of various lubricant oils was also assessed. The mechanisms of abrasion with and without particles were characterised.