bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermo‐oxidative stability of new‐generation base oils
Authors: Pandey D. C. , Sahoo S. K. , Singh I. D. 
Published: July 2006

AbstractThermo‐oxidation of base oils is the primary cause of lubricant degradation and engine failure during use. Degradation is mainly due to high‐temperature oxidation and thermal decomposition near the piston ring zone, forming oxygenated compounds that polymerise to form high‐molecular‐weight insoluble deposits. New‐generation base oils are found to be more stable towards oxidation and deposit formation due to the absence of aromatics and polynaphthenes. However, compatibility with antioxidants and other additives is now of greater concern because of the poor solvency of these oils. With the increase in the purity of the oil, sometimes the oxidation performance is poor in comparison to group I oils, mainly due to the removal of sulphur compounds, which act as natural antioxidants.Thermal techniques, such as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), are emerging as fast and accurate methods for determining the thermo‐oxidative stability of base oils and their additive blends, making it possible to measure the oxidation induction time, incipient oxidation temperature, and deposit‐forming tendency. The objective of this work is to evaluate the thermo‐oxidative stability of new‐generation group II/III base oils without antioxidant additives, using DSC and TGA. The kinetics of base oil oxidative degradation are studied using different heating rates. The data obtained from thermal techniques are correlated with the micro‐oxidation data obtained from the Penn State Micro‐Oxidation (PSMO) test. The response of a typical antioxidant additive, zinc dialkyldithiophosphate, towards oxidative degradation of base oils has also been studied.
Assessment of the useful life of current long‐drain and future low‐phosphorus engine oils
Authors: Korcek S. , Jensen R. K. , Johnson M. D. 
Published: July 2006

AbstractThe assessment of engine oil useful life is an important step in the development of future low‐phosphorus, catalyst‐compatible, and long‐drain engine oils. This paper describes the development and application of a new laboratory screening test, the Ford oil ageing test (FOAT), for the assessment of engine oil useful life. FOAT simulates the Sequence IIIE engine dynamometer test and evaluates oils on the basis of viscosity increase. It correlates well with both single‐ and double‐length Sequence IIIE test results. FOAT allows for inexpensive screening of candidate oils prior to engine tests and is currently being used in the evaluation of future low‐phosphorus engine oils. This comparative study has demonstrated that low‐phosphorus, catalyst‐compatible engine oils can be formulated to provide a similar useful life to current commercial long‐drain oils.
A contribution to determining the friction coefficient in hydroforming of tubes
Authors: Plancak M. , Vollertsen F. 
Published: July 2006

AbstractHydroforming is a relatively new technology, which enables complex shaped hollow parts to be produced efficiently. Compared to alternative methods, this technology is characterised by significant potential advantages, such as complex shape production, lightweight design, high accuracy, and process integration.The tribological aspects of hydroforming are very significant, as friction influences all the main process parameters practically in a direct or indirect way. However, there is a paucity of information relating to hydroforming tribology. In most reports on this subject only qualitative data regarding the friction coefficient are given. However, for finite‐element method simulation and optimal process and tool design, quantitative data are indispensable.This paper describes an attempt to determine the coefficient of friction in both the elastic and plastic states of a workpiece during tube hydroforming processes. Push‐through tests were carried out in order to determine the coefficient of friction in the elastic state, and tube upsetting tests were conducted for the plastic state. Various commercial lubricants were used in the experiments.
Nano‐scratch study of molecular deposition films on silicon wafers using nano‐indentation
Authors: Deguo Wang , Siwei Zhang , Manglai Gao 
Published: July 2006

AbstractExperiments on molecular deposition (MD) films with and without alkyl terminal groups deposited on silicon wafers were conducted using nano‐indentation. It was found that MD films and alkyl‐terminated MD films exhibit a higher critical load and a lower coefficient of friction than the silicon substrate. The critical load increases with the number of layers, and the coefficients of friction of MD films with alkyl terminal groups are lower than those of the corresponding MD films with the same number of layers but without alkyl terminal groups.
Some considerations concerning lubrication in high‐performance internal combustion engines
Authors: Righes Giuseppe , Garro Attilio , Calderale Pasquale Mario 
Published: July 2006

AbstractThe increasing rotational speeds and the weight reduction of high‐performance internal combustion engines are accompanied by problems of lubrication, heat transfer, and vibration that are mostly negligible in medium‐ and low‐performance engines. To deal with such phenomena under demanding operating conditions necessitates a specific design. The dynamics of the power system between crankshaft and related sub‐components, e. g., bending and torsional vibrations of the connecting rod, ovalisation of the head and eye of the connecting rod, and vibrations of thin cylinder liners, are critical for the lubrication system in general, and for oil film pressure fields in particular. In some cases, no information on these features has existed until now, so no quantification of the variables involved has been possible. Over the last few years a systematic investigation has been performed to take into account the critical points and their fundamental importance in the design of such engines.The present paper considers some of the phenomena related to lubrication in high‐performance engines. The need is highlighted for further investigations using computational and experimental methodologies.
Adhesion of cleaned nanoscopic metal contacts
Authors: Santner E. , Spaltmann D. 
Published: July 2006

AbstractNanoscopic metal contact in the context used in this paper means atomic force microscope (AFM) tips in contact with cleaned, flat, smooth surfaces in ultrahigh vacuum. Such idealised contact conditions are of more and more relevance for technical friction systems despite the fact that for the latter the loads and the velocities are usually higher, the materials used are impure (e. g. alloys) and contaminants or lubricants are present between the sliding surfaces. Sliding contacts in micro‐system technology, which is unequivocally a key technology of the future, will presumably be compared with such idealised conditions. Another important reason for the investigation of nanoscopic contacts is the strong interest in the understanding of the elementary processes and mechanisms causing friction. The investigation of friction systems with a reduced number of influencing parameters offers a chance to gain insight into elementary processes and to compare the results with theoretical models based on physical principles, such as molecular dynamics simulation.
Investigation of antiwear coatings deposited by the pvd process
Authors: Tuszynski W. , Szczerek M. , Michalczewski R. 
Published: July 2006

AbstractThe tribological properties of various PVD‐deposited coatings (vacuum arc method) have been tested, both single‐layer coatings (TiN, CrN, Ti(C,N), and Cr(C,N)) and multilayer coatings (Cr(C,N)/CrN/Cr and CR(C,N)/(CrN+Cr2N)/CrN/Cr). An unlubricated ball‐on‐disc tribosystem was used in which an Al2O3 ball is pressed against a coated steel disc rotating in the horizontal plane. A novelty of the method is the removal of wear debris from the contact zone using a draught of dry argon. This improves the repeatability of the test results and the stability of the tribological characteristics.It is shown that CrN coatings exhibit the best antiwear properties and Ti(C,N) the worst. Multilayer coatings have better antiwear properties than single‐layer ones. The friction coefficients for CrN and Cr(C,N) coatings are much smaller than for the commonly used TiN.A correlation has also been found between the physical properties of the coatings tested (adhesion of the coating to the substrate assessed in scratch tests, and coating hardness) and their antiwear properties. An improvement in coating‐substrate adhesion results in wear reduction, while greater hardness (causing a coating embrittlement increase and a change in the wear mechanism) brings about greater wear. There is no correlation between the physical properties and the friction coefficients of the coatings tested.
Influence of test parameters on friction and wear results obtained in oscillating sliding tests with 100cr6 steel against sic‐based materials
Authors: Klaffke D. 
Published: July 2006

AbstractIn order to characterise materials for tribological applications, model tests with simple contact geometry are in widespread use. Friction and wear behaviour can be determined with high accuracy from this type of test. Tests with oscillating sliding motion have the advantage that only small‐sized specimens are required. However, the fact that the results of model tests are affected considerably by the choice of test parameters is often overlooked. In order to check the influence of test parameters on friction and wear results, tests were performed in which the relevant parameters (stroke, frequency, load, relative humidity of the surrounding air) were varied. Comparative studies with different SiC‐based materials (SiC, SiSiC, and SiC‐TiC) against steel (100Cr6) under unlubricated conditions at room temperature show that in all cases the relative humidity is an important parameter, influencing the friction and wear results substantially. Additionally, several parameters can modify friction and wear behaviour more or less significantly. The effects of test parameters on friction and wear are discussed here on the basis of the wear mechanism. Some of the consequences of this for planning test series and for the practical use of test results are noted.
Mechanism of ploughing wear of martensite nodular cast iron
Authors: Jingpei Xie , Eigin Wang , Wenyan Wang , Yanpei Shong , Luoli Li 
Published: July 2006

AbstractThe mechanism of ploughing wear of martensite nodular cast iron has been investigated by means of elastic contact theory, stress interferometry, and scanning electron microscopy. Stress distributions in the contact area are plotted through numerical quadrature. The results show that the formation of cracks is between 0.2a and 0.5a (a is the radius of the contact curve). The driving force to produce crack extension along the Y axis is τyzmax and the extension direction is 45° to the horizontal. The driving force to produce crack extension along the X axis is either τx or τxzmax and the direction of crack extension is 37° to the horizontal.
Water‐Lubricated and Dry‐Running Properties of Ceramic Journal Bearings
Authors: Andersson Peter 
Published: July 2006

AbstractJournal bearings and other well‐defined sliding surfaces are important for numerous moving mechanical assemblies. Quite often sliding surfaces are produced on particular components during fabrication, for which reason the manufacturer needs to know the properties of the materials in order to optimise production processes and the running‐in characteristics of the sliding surfaces. This paper describes application‐orientated tests to support the selection of ceramic materials for water‐lubricated and unlubricated journal bearings and similar sliding surfaces. The ceramics studied were different grades of alumina, sialon, silicon carbide, and zirconia. The most promising results were obtained with a dense, sintered silicon carbide.
Comparison of Empirical Methods and Measurements for the Determination of Wear of Worm Gears
Authors: Kral P. , Pausch S. 
Published: July 2006

AbstractEmpirical methods use the results of test bench measurements with varying gear running conditions (such as output torque, type of lubricating oil, and material of worm and worm wheel) to allow one to derive mathematical relations for more easily calculating the wear that occurs. In this paper the empirical methods of Neupert and Steingröver are applied to two worm gears and the results described. Also, test bench measurements on two different test gears (of different worm flank shapes and slightly differing material and geometrical dimensions) were carried out. For these measurements, two types of lubricating oils, mineral and synthetic, were used. The advantages and disadvantages of the empirical methods compared to the test bench measurements and computer simulations to determine the wear of worm gears (empirical calculations, measurements, and mathematical modelling and simulations) are presented and discussed in detail. These results should help to select the best method for each case of wear evaluation.
A Theoretical Approach to Evaluating the Performance Characteristics of Double‐Decker High‐Precision Bearings
Authors: Prashad Har 
Published: July 2006

AbstractThis paper presents a theoretical approach to evaluating the deflection and indentation of the track surface of the inner race, the stiffness, and the life of double‐decker high‐precision bearings (DDHPBs). The deflection, indentation, and stiffness of DDH‐PBs have been compared with those of conventional bearings of the same bore under identical operating conditions. The analysis, in general, indicates that the deflection of the DDHPB is less and the stiffness is greater than in conventional bearings. Computation of the data under various loads indicates that the indentation on the ball tracks of the DDHPB is comparable to or less than that of conventional bearings of the same bore. The better performance characteristics of the DDHPB make it useful in various industrial applications.
Investigation of the Thermal Behaviour of Non‐metallic Curved‐Face‐Width Spur Gears
Authors: Andrei L. , Epureanu A. , Andrei G. , Walton D. 
Published: July 2006

AbstractThis paper describes a curved‐face‐width spur gear, specially designed for manufacture from non‐metallic materials. The benefits of this gear are the higher contact ratio, bending and Hertzian contact resistance, and greater tooth stiffness compared to standard spur gears. A modified geometry is proposed for the gear tooth, the height of which varies along the gear face width. Due to the reduction in tooth height, in sections away from the gear centre, lower sliding friction is expected, with consequences for the gear's thermal behaviour. The complex gear geometry makes the design of a die difficult; therefore the gears were cut on a milling machine, using a special kinematic generation process and related equipment. The tooth flank profile, an involute or near involute in sections away from the gear half‐width plane, as well as the flank surface quality determined by the single‐cutter tool used for gear manufacture, influence the meshing condition, and can be detrimental to the thermal behaviour of the gear. Experimental tests were carried out to examine the influence of load and speed on the temperature of the curved‐face‐width spur gears with modified geometry. The measured temperature of the non‐standard gear is further compared with the predicted temperature of plastic standard spur gears of the same specification.
The influence of oxygen on the friction and wear behaviour of a copper—steel couple under electric current
Authors: Bouchoucha A. , Chekroud S. , Paulmier D. 
Published: July 2006

AbstractThe tribological behaviour of a copper—steel couple similar to those in electrified railways has been studied as a function of mechanical, electrical, and environmental parameters. The experimental results obtained in an oxygen atmosphere show that this factor has a major influence on the wear behaviour. While there was a reduction in the average coefficient of friction compared to in argon, under oxygen there was twice the wear found under air, and six times that found under argon. In the absence of an electric current, the nature of the wear was essentially mild adhesive. However, with an electric current at the interface, fluctuations, particularly at high intensities, were recorded in both the coefficient of friction and the electrical contact resistance, and there was severe wear. Discussion of the results is based on examination of the wear surfaces and analysis of the phenomena observed during sliding contact.
Study of grey relational grade identification for ferrography based on characteristic analysis of wear debris
Authors: Hu Xianguo , Zhan Song , Zheng Shousen 
Published: July 2006

AbstractAttention has been focused on how to achieve intelligent automation in ferrographic diagnosis in order to overcome the subjectivity of the diagnosis process. The present paper reports on a technique of characteristic measurement developed on the basis of the VC++ 6.0 programming platform, with characteristic parameters such as area, roundness, and aspect ratio being extracted from images of wear debris based on digital image analysis. However, the extraction of characteristic parameters from a ferrographic image is not the ultimate purpose of ferrographic diagnosis. The wear particles should be classified into several pre‐decision categories and their statistical distribution should also be calculated. The grey relational grade theory is introduced in this paper as a way to recognise wear debris and a new software system has been developed to deal with the problems occurring in the automation of ferrographic diagnosis. It is shown that the identification rules can be used to treat some real wear debris images with generally satisfactory results.
Study of the formation of gouging pits in Mn7Cr2 steel under impact abrasive wear conditions
Authors: Xie J. P. , Wang A. Q. , Yuan H. L. , Wang W. Y. , Li L. L. 
Published: July 2006

AbstractA study of the formation of gouging pits in Mn7Cr2 steel under impact abrasive wear conditions was conducted using theories of elastic impact and contact, analysis of photo‐elasticity, and scanning electron microscopy (SEM). The results show that the maximum shear stress occurs at z = 0. 48a, and this initiates a crack; the crack propagates at an angle of 45° from the horizontal; and the gouging pit is conical. The SEM observations are in agreement with the theoretical calculations.
Two energy efficient algorithms for tracking objects in a sensor network
Authors: Rapaka Arvind , Madria Sanjay 
Published: July 2006

AbstractWe propose two energy efficient algorithms for locating a target object moving in an area covered by a wireless ad hoc network. The first algorithm developed conserve energy by efficiently identifying sensor nodes, asHome Nodes, and use only local messages between neighboring nodes to follow the trail of the object. Since we avoid the long‐range transmission and maximize the localization, the algorithms reduce the communication cost. The dynamic nature of the second algorithm exploits the predefined parameters such as the object velocity. Our algorithm represents query shipping against the conventional data shipping as a means to reduce the amount of data being shipped across the network. Hence, it locates the objects over the network with minimal energy conservation using short‐range message transmissions. The performance analysis (both experimental and theoretical) shows the effectiveness of the two algorithms in comparison to another tracking algorithm. Copyright © 2006 John Wiley & Sons, Ltd.
Estimating nest locations of bumblebee Bombus ardens from flower quality and distribution
Authors: Suzuki Yukari , Kawaguchi Lina G. , Toquenaga Yukihiko 
Published: July 2006

AbstractThe central‐place forager in a social‐insect colony, e.g., the bumblebee, has been expected to maximize its net rate of energy gain to increase the success of its colony. In addition to foraging behavior, the nest location is an important factor for the success of the colony. The bumblebee's nest location would be affected by the spatial distribution of flowers and their food quality. In this study, we constructed a model to estimate bumblebee nest sites, using the net energy intake rate at available food sites for workers foraging from the nest site. We hypothesized that the probability of colony establishment at a site in coordinates (x, y) was high as the sum of the net energy intake rate I(x, y) increased. To obtain I(x, y), nectar standing crop, sugar concentration, and foraging time were measured for ten plant species in the study site covering 6.25 km2. As available flowers changed seasonally, I(x, y) was calculated for three periods: the end of April, the beginning of May, and the middle of May. To verify our hypothesis, we compared the estimations in our model with the actual nest sites of Bombus ardens found in the beginning of May and June by means of tracking bumblebees. From the results, we considered that the net energy intake rate at mid‐May might represent the probability of colony establishment, because it could affect colony persistence and reproductive success.
Unadapted behaviour of native, dominant ant species during the colonization of an aggressive, invasive ant
Authors: Le Breton Julien , Orivel Jérôme , Chazeau Jean , Dejean Alain 
Published: July 2006

AbstractAmong the factors driving the invasive success of non‐indigenous species, the “escape opportunity” or “enemy release” hypothesis argues that an invader's success may result partly from less resistance from the new competitors found in its introduced range. In this study, we examined competitive interactions between the little fire ant Wasmannia auropunctata (Roger) and ant species of the genus Pheidole in places where both are native (French Guiana) and in places where only species of Pheidole are native (New Caledonia). The experimental introduction of W. auropunctata at food resources monopolized by the Pheidole species induced the recruitment of major workers only for the Guianian Pheidole species, which were very effective at killing Wasmannia competitors. In contrast, an overall decrease in the number of Pheidole workers and no recruitment of major workers were observed for the New Caledonian species, although the latter were the only ones able to kill the Wasmannia workers. These results emphasize the inappropriate response of native dominant New Caledonian species to W. auropunctata and, thus, the importance of enemy recognition and specification in the organization of ant communities. This factor could explain how invasive animal species, particularly ants, may be able to successfully invade species‐rich communities.