bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correct dissociation limit for the exchange‐correlation energy and potential
Authors: Gritsenko Oleg , Baerends Evert Jan 
Published: July 2006

AbstractLocal and semilocal functionals like the local density (LDA) and generalized gradient approximations (GGA) fail to provide correct behavior during the dissociation of electron pair bonds: the asymptotic potential energy curve is wrong, the dissociation in the heteronuclear case leads to partially ionic instead of neutral atoms, and the time‐dependent density functional theory (TD‐DFT) excitation energies behave incorrectly upon bond stretching. We demonstrate that such errors can be avoided by the use of an orbital‐dependent exchange‐correlation (xc) functional. Such a functional needs to incorporate, in contrast to the popular exact exchange functional, the electron correlation effects. The demonstration is given for the electron pair bond of a diatomic molecule AB with just one orbital on A and one on B. This simple two‐orbital model affords an analytical inversion of the density response function, which is used to show that the orbital‐dependent xc functional described previously, possesses the correct dissociation limit for the xc energy and potential. The correct potential (xc hole potential in the symmetric case AB, for example, for the dissociating H2 molecule) properly describes strong nondynamical (left–right) electron correlation, while in the heteroatomic case (A ≠ B) it develops an additional “counter‐ionic” step behavior in its response part, which is needed to ensure proper covalent dissociation of the AB bond (and proper covalency at long bond distances). © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Study of the flaking‐off phenomenon on a jet Engine's shaft bearing using the thin layer activation technique
Authors: Delvigne T. , Chevalier A. , Dubois G. , Escuriol M. , Fehsenfeld P. , Kleinrahm A. , Monnot R. , Pommier S. 
Published: July 2006

AbstractThe Thin Layer Activation technique has been applied in order to study the flake‐off phenomenon on a jet engine's shaft bearing. The external track of the bearing has been activated following the reaction 56Fe(p,n)56Co, over a depth of 80 μm. In spite of a very low activation level, the first signs of flaking‐off were detected 30 min before any significant increase in the vibration level appeared. At that point, the mass of particles leaving the track was measured on line, with a precision of 0.2 mg.
Molecular dynamics simulation of poiseuille flow in ultra thin film
Authors: Hu Y. Z. , Wang H. , Guo Y. 
Published: July 2006

AbstractThe effect of a solid wall on Poiseuille flow of ultra thin film has been simulated by molecular dynamics for a simple Lennard‐Jones fluid. Results showed that the velocity profile and flow are consistent with the prediction of the Stokes equations when the film thickness is considerably greater than the molecular ‘diameter’; that Poiseuille or hydrodynamic flow will be blocked by the solid walls, and the effective viscosity will increase as the film thickness corresponds more closely to only a few molecular diameters; and that when the film thickness is reduced to just the molecular diameter, the fluid molecules between the walls will be solidified or crystallised, and the Poiseuille flow will vanish. This may be one of the mechanisms of transition from hydrodynamic to boundary lubrication.
A single‐pendulum scratch device
Authors: Shu Li , Shizhuo Li , Yanan Liang , Chun Yan , Shenrong Yang 
Published: July 2006

AbstractA single‐pendulum scratch device together with a relevant methodology has been developed for the tribological investigation of modified surfaces of materials. This device allows determination of energy consumed in a single pass scratch along with normal and tangential forces, as well as wear loss. As a stylus, mounted on a pendulum hammer, touches, penetrates, and grooves, and skims over the surface of the specimen in a short duration, a series of phenomena involving elastic and plastic deformation or fracture occurs. This process is considered to be the best simulation of abrasion and erosion. The newly developed device has proven useful in tribological evaluations of a variety of surface modified materials, such as adhesion of superhard coatings, cohesion of thermal spraying overlays and dynamic hardness of diffusion layers.
A measurement and testing method for lubrication regimes in gear transmissions
Authors: Wang Tie , Li Jinbao 
Published: July 2006

AbstractThis paper describes the measurement and test results on oil film thickness conducted with a self‐contained gear testing machine, with pandimensional power flow, using an improved method of discharge voltage measurement. A series of experiments were conducted in an attempt to measure and analyse the lubrication regimes of involute and double circular arc gear with different lubricants under various working conditions. A formula is provided for calculating oil film discharge voltage following the recorded output of a level recorder.Experimental results show that such an improved method for discharge voltage is suitable for measurement of film thickness, and that the results are in keeping with the minimum film thickness formula for a double circular arc gear deduced by the authors. The relations between film voltage and the gear parameters of load, rotation speed, lubricant and oil temperature, are also discussed. It is asserted that such a test system has more reliable performance and is more suitable for measuring and analysing the lubrication regimes of gear transmissions than are ordinary experimental systems.
Wear maps for some uncoated cutting tools
Authors: Lim S. C. , Lee S. H. , Liu Y. B. , Seah K. H. W. 
Published: July 2006

AbstractThe method of using maps and diagrams to present wear rates and wear mechanisms, as well as showing the relationships between them, has been applied to cutting tools. In this summary paper, wear maps obtained earlier for uncoated high‐speed steel (HSS) cutting tools are presented together with maps for uncoated carbide cutting tools. Within the two‐dimensional area of a wear map defined by two easily controlled machining parameters, namely feed rate and cutting speed, the rates of tool wear, and the wear mechanisms observed during actual dry turning operations, are displayed. The presence of safety zones and least‐wear regimes in these maps suggests that it may be possible to optimise actual machining operations so that compromises between rates of material removal, for an acceptable level of productivity, and tool costs can be reached. The concept of using machining‐regions maps for practical tool‐wear minimisation during machining is also discussed.
The controlling factor in the formation of transfer films on ceramic surfaces during sliding contact against metals
Authors: Zhou L. , Fang L. , Gao Y. M. , Zhou J. E. 
Published: July 2006

AbstractA transfer film plays a very important role in the sliding wear process. This paper discusses a factor, ‚adhesive energy’︁, which affects the formation of transfer film on the ceramic's surface during sliding friction of ceramics against metals. On the basis of both a theoretical evaluation of adhesive energies, and experimental results, it can be concluded that the adhesive energy between ceramics and metals is the controlling factor in the formation of transfer film on the ceramic surface. A new semi‐quantitative method to determine the relative thickness of transfer film on ceramic surface with EDAX is discussed.
Life tests on elastomeric lip seals for pneumatic cylinders
Authors: Belforte Guido , Raparelli Terenziano , Mazza Luigi 
Published: July 2006

AbstractA test method and a testing machine for evaluating the wear of lip seals for pneumatic cylinders are presented. The method and the machine have been evaluated with tests on different types of seals for cylinders with a 50 mm bore. Three levels of lubrication condition were examined: dry, with a film of grease, and with an optimum amount of grease. Differences were noted both between these conditions of lubrication, and between types of seal. © Leaf Coppin 1997.
Tribological behaviour of MW PACVD diamond coatings in vibrating contacts
Authors: Skopp A. , Klaffke D. , Buchkremer‐Hermanns H. , Ren H. , Weiß H. 
Published: July 2006

AbstractSix diamond coatings were produced by microwave plasma‐assisted chemical vapour deposition (MW PACVD) on polished SiC substrates. Process gas pressure and process gas composition were varied systematically, resulting in different coating morphologies, roughnesses and grain sizes.Friction and wear were investigated for unlubricated vibrating contact conditions in air at room temperature. Tribological tests on diamond coatings were performed in a ball‐on‐disc configuration, with steel balls (100Cr6) and alumina balls acting as counterbodies. For comparison of the tribological performance of the diamond coatings, standard tests were performed with a stroke of 200 μn, a load of 10 N, and a frequency of 20 Hz. The effect of relative humidity (RH) was investigated by testing in dry (3% RH), in normal (50% RH), and in moist air (100% RH), respectively To investigate running‐in effects and wear propagation, the test duration (104, 105, and 1.2·106 sliding cycles) was varied.For steel/diamond pairings, high wear at the steel ball and high friction were measured, influenced by roughness and grain size of the diamond coating and by relative humidity. For Al2O3 against diamond, a pronounced running‐in of friction and wear was found. High friction and high wear at the beginning of each test are followed by a stationary phase with extremely low friction coefficients (⩽ 0.05) and with wear rates below the limit of resolution. This running‐in depends on grain size and roughness of the coating, on relative humidity, as well as on the operational parameters. Surface analysis using SEM, EDX, LRS and AFM was conducted, to investigate tribologically induced surface changes.
Diagnosis and condition monitoring of medium‐speed marine diesel engines
Authors: Kouremenos D. A. , Hountalas D. T. 
Published: July 2006

AbstractDiagnosis of diesel engines is not new and various methods have been proposed in the past for fault diagnosis. The problems relating to marine diesel engines, especially medium‐ and high‐speed engines, are due mainly to their large size, which does not allow the use of trial and error methods, and their high operating speed. The most difficult problem occurs when the engine is not able to produce its maximum power, while there is no obvious fault or error. In the present work a method is described which attempts to offer a solution to such problems. The method is a thermodynamic one based on a simulation model and the processing of measured engine data. Presented is an application of the method to a medium‐speed marine diesel engine, which suffered from low power output accompanied by high exhaust gas temperatures. The results from application of the method show that the problem is not a direct one, but is caused by many factors that result in improper operation. With this method, the current engine condition can be discovered, and suggestions made for proper tuning or repair. After conducting such an analysis, a vessel was able to achieve its maximum cruising speed, showing that the proposed method is a promising one.
Coking and microcoking: Tools for evaluating and developing lubricant additives
Authors: Cazin J. , Abellaneda G. , Brégent R. , Pascal J. C. 
Published: July 2006

AbstractTwo tests for evaluating an engine lubricant's tendency to form deposits at high temperature have been developed by a working group of the GFC,Groupement Français de Coordination (French Coordination Group).
set up to establish laboratory pre‐selection tests. The first is a new static microcoking test where the oil is deposited on an aluminium alloy plate and submitted to thermal conditions similar to those found in the piston ring zone of an IC engine. The results are analysed to determine the temperature at the oil's thermal stability limit and to evaluate the quantity and nature of the deposits in the form of varnish, according to a grading system based on the CEC M‐02‐A‐78 method of gauging engine cleanliness. The second is an improved panel coking test in which a thin film of oil of a given volume is fed on to a stainless steel panel, at high temperature, and the deposits formed at the end of the test are evaluated, again using the CEC rating method, in terms of quantity and type (carbon or varnish).In addition, a video system has been designed to grade the micro‐coking panels through colour recognition. This not only allows visual grading to be faithfully reproduced but also eliminates the subjective element of colour grading. The results obtained with the ‘Video‐Rater’ constitute a first step towards computer‐assisted grading of engine parts.
A tribotesting method for evaluating cemented carbide tribo‐performance
Authors: Scieszka S. F. , Filipowicz K. 
Published: July 2006

AbstractThe abrasive wear properties of materials in sliding contact with solid mineral particles during the comminution process have been studied. The equipment used can simulate the tribo‐conditions inside coal pulverisers. Using this experimental apparatus, a number of different cemented tungsten carbides have been tested and classified according to their resistance to abrasive wear in rubbing contact with particulate coal. The paper shows that the wear results can be used to estimate the resistance of a material to brittle fragmentation and chipping of the edges during tribo‐contact with solid particles. An equation is presented which enables calculation of the fracture resistance factor, KWR, based on results from carefully controlled repeated abrasion tests.
MEMs hydrodynamic bearings: Applications to and implications for machine failure prevention
Authors: Wood Kristin L. , Neikirk Dean , Busch‐Vishniac Ilene , Weldon William , Chu Chin‐Seng , Kim Youndmin , Gupta Vikas , Maddox William , Masser David 
Published: July 2006

AbstractMicrodynamic systems have been studied for a number of years. Only limited work, however, has been completed on integrating microdynamic components into systems that satisfy mechanical tasks on macroscopic scales. In this paper, we describe microdynamic components needed to produce a surface which is actively deformable on local scales. In particular, we consider the design and demonstration of smart journal and thrust bearings capable of using embedded sensors and actuators to change dynamically the surface geometry. The ability actively to deform bearing surfaces allows for the design of bearings which are less prone to failure, the design of bearings with greater load‐carrying abilities, and a fundamental study of the effect of surface geometries and fluid conditions on bearing performance, such as start‐up and shut‐down conditions. Some results of our new bearing designs are presented, focusing on numerical bearing models, sensor and actuator design and fabrication, and physical experimentation.
Application of an envelope technique in the detection of ball bearing defects in a laboratory experiment
Authors: Toersen Henk 
Published: July 2006

AbstractTo judge the diagnostic capabilities of an envelope technique, based on enveloping the resonance frequency of a transducer, Bearcon Signature™, Carl Schenck AG, Germany
artificially damaged ball bearings (SKF 6207) were run under oil lubrication at different radial loads and speeds in a laboratory experiment. Damage to the outer race, inner race and ball of different magnitudes was introduced by spark erosion and the response of the measurement system was analysed. The results showed that vibration spectrum components of outer race defects showed up in the envelope spectra of undamaged bearings, and that the detectability of defects was primarily limited by the speed of the bearing; on occasion the automatic scaling facility of the analyser was a limiting factor. Inner race and ball defects showed the well‐known effects of load modulation in the defect contact zone, which can become dominant in the envelope spectra at high loads and speeds. This phenomenon could be confirmed by computer simulation. The detection of ball damage was hampered by the fact that overrolling of the defect in purely radially loaded bearings takes place incidentally. This drawback could be mitigated by applying a trigger technique to the envelope signal.
Gear crack propagation investigations
Authors: Lewicki David G. , Ballarini Roberto 
Published: July 2006

AbstractAnalytical and experimental studies were performed to investigate the effect of gear rim thickness on crack propagation life. The FRANC (FRacture Analysis Code) computer program was used to simulate crack propagation. The FRANC program used principles of linear elastic fracture mechanics, finite element modelling, and a unique re‐meshing scheme to determine crack tip stress distributions, estimate stress intensity factors, and model crack propagation. Various fatigue crack growth models were used to estimate crack propagation life, based on the calculated stress intensity factors. Experimental tests were performed in a gear fatigue rig to validate predicted crack propagation results. Test gears were installed with special crack propagation gauges in the tooth fillet region to measure bending fatigue crack growth. Good correlation between predicted and measured crack growth was achieved when the fatigue crack closure concept was introduced into the analysis. As the gear rim thickness decreased, the compressive cyclic stress in the gear tooth fillet region increased. This retarded crack growth and increased the number of crack propagation cycles to failure.
A software‐based measurement system for testing and analysis of automotive brake squeal
Authors: Bergman Filip , Eriksson Mikael , Jacobson Staffan 
Published: July 2006

AbstractA software‐based measurement system using both analogue data acquisition and digital communication via a general‐purpose interface bus (GPIB) board has been developed for analysis and evaluation of disc brake squeal. The system is built around a computer and based on commercial software. Brake pressure and torque, rotational speed, five different temperatures, and sound emission are logged once a second. If the sound is characterised as a squeal it is saved to file together with the other parameters.The measurement system is very flexible, allowing for different types of instruments and sensors to be used by adapting the software. Furthermore, the same software is used for evaluation of the collected data.Mechanically, the equipment consists of a complete front wheel suspension where the original brake disc and caliper are mounted in a steel tube chassis. The brake disc is driven by a DC electric motor, while a hydraulic system provides the brake pressure. Brake pressure and rotational speed can be controlled independently.
NMR and DSC studies of base oils
Authors: Adhvaryu A. , Pandey D. C. , Singh I. D. 
Published: July 2006

AbstractThe effect of the composition of a base oil matrix on additive response is an indication of its behaviour in a dynamic system. In this paper, a novel method involving quantitative 1H and 13C NMR to explain the molecular chemistry of base oil is used. Oxidative degradation of base oils (pure as well as additivated) has been studied using DSC. The results are explained in terms of molecular composition of the different base stocks to get a clear understanding of additive response in a matrix of different hydrocarbon oils.
A method of measuring oil consumption by labelling with radioactive bromine
Authors: Zellbeck H. , Bergmann M. , Röthig J. , Seibold J. , Zeuner A. 
Published: July 2006

AbstractA method of determining the oil consumption rate of combustion engines is presented. It is based on labelling the individual oil fractions of engine oil with radioactive bromine isotope82 Br and on the quantitative absorption of radioactive bromine compounds in the exhaust gas in an aqueous solution of nitric acid and silver nitrate. The advantages of this method are that the oil that is consumed in the exhaust gas can be directly measured, without the fluctuating amounts of oil in the sump influencing the result, and the behaviour of the individual components of the oil in the consumption process can be determined. The test is quick, only twenty minutes being required to detect oil consumption at one operating point; and with a single labelling, the oil consumption at a great number of working engine points can be measured 82 Br has a short half‐life of only 36 h, so that compliance with radiation protection measures is inexpensive and investigations can be carried out using a conventional testing device.As part of the research project, a study was made of the influence of different base oil types, with and without polymer additives, on consumption. Results showed that Noack evaporation loss correlated with oil consumption only with boiling fractions of exactly the same base oil, and not with different, in particular synthetic, base oils; that polymer additives (VI improvers) significantly reduced the rate of oil consumption; and that the polymer additive and the type of base oil both had more influence on oil consumption than viscosity.
Engine friction lubricant sensitivities: A comparison of modern diesel and gasoline engines
Authors: Taylor R. I. 
Published: July 2006

AbstractEngine friction models have been developed that take account of the variations in lubricants with temperature, shear rate, and pressure. These models have been used to study the lubricant sensitivities of modern diesel and gasoline engines. Total engine friction losses for a Perkins Phaser four‐cylinder, 4.0 l, turbocharged, inter‐cooled diesel engine, operating at 1300 rpm, with an SAE 15W‐40 lubricant, were estimated at approximately 2 kW, with the piston assembly contributing 46%, the bearings 49%, and the valve train 5%. Total engine friction losses for a Mercedes Benz M111 2.0 l gasoline engine (used in CEC sludge and fuel economy engine tests) operating at 2500 rpm, and medium load, for an SAE 15W‐40 lubricant, were estimated at 1.5 kW, with the piston assembly contributing 42%, the bearings 39%, and the valve train 19%.
Maximising the fuel efficiency of engine oils: The role of tribology
Authors: Korcek Stefan , Jensen Ronald K. , Johnson Milton D. , Sorab Jagadish 
Published: July 2006

AbstractImprovement of engine fuel efficiency is one of the most important goals of current automotive development. Maximising the contribution of engine oils to fuel efficiency is a very important part of this process. Engine friction modelling, based on fundamental tribological considerations, has shown that further engine friction improvements are possible through engine oil reformulation. This reformulation should minimise friction under hydrodynamic conditions through modification of the rheological properties of oils, and also minimise friction under mixed and boundary lubrication conditions through changes in the chemical composition of the oils. These improvements can be achieved by appropriate selection of a base oil as well as by the use of effective friction‐reducing additive systems. A very important consideration in formulating these highly fuel‐efficient oils is their ability to retain their fuel efficiency during the entire oil service interval. This paper describes the role of tribological research in the development and introduction of advanced fuel‐efficient engine oils.