bluuebunny/crossref_metadata_2025_split huggingface dataset:
The lubrication of metal-on-metal total hip joints: A slide down the Stribeck curve
Authors: Smith S. L. , Dowson D , Goldsmith A. A. J. 
Published: October 2002

Metal-on-metal joints can exhibit profoundly different modes of lubrication when tested in a hip simulator. A range of metal-on-metal joints of similar diameters differing only in diametral clearance can demonstrate differences in lubrication conditions during simulator testing, as can joints differing principally in diameter. Simulated walking cycles can similarly cause differences in lubricating conditions through the application of different motion and loading cycles. In this study, and work conducted previously by the authors, metal-on-metal joints were tested in 25 per cent bovine serum in a hip simulator. A simple resistivity technique was used to detect surface contact, or separation, in a lubrication study, while a wear study used a gravimetric protocol extending over at least 2000000 cycles duration. Simulated physiological and simplified walking cycles were used during the studies to investigate the effect of motion and load on lubrication and wear. Joints of 16, 22.225, 28 and 36 mm nominal diameter were tested to investigate the effect of diameter, while the effect of diametral clearance was studied using joints of 36 mm diameter with a range of diametral clearances from 97 to 170μm. The trend of an idealized Stribeck curve, plotted as coefficient of friction versus the dimensionless Sommerfeld parameter (viscosity × sliding velocity × radius of the femoral head/load), indicates the lubrication regime prevalent in a joint. Boundary, mixed and fluid-film lubrication, shown by the three classic regions on an idealized Stribeck curve, were all demonstrated using metal-on-metal joints in a hip simulator. The different modes of lubrication prevalent in the joints resulted in wear rates spanning two orders of magnitude between joints differing principally in diameter. Similarly, a reduction in diametral clearance caused a general increase in the proportion of surface separation per simulated walking cycle. Likewise, a simplified walking cycle generated more surface separation per walking cycle for the same joint subjected to a simulated physiological cycle. However, the two walking cycles generated no significant difference in simulator wear rates.
Numerical prediction of the performance of gas-lubricated spiral groove thrust bearings
Authors: Yue Y , Stolarski T. A. 
Published: October 2002

The objective of this paper is to develop an accurate numerical procedure for the analysis of nominally flat contacts with spiral grooves lubricated by gases. The numerical procedure, which is based on the control-volume method, enables the solutions of the non-linear Reynolds equation to be obtained without limitation in geometry and operating conditions. Satisfactory flow balance was achieved on the control volumes as well as on the whole boundary and the method was proved to be very accurate. Convergence of the method was quick for any compressibility number. Three types of contact with spiral grooves were analysed. They were hydrodynamic bearings without interior chambers, hydrodynamic bearings with interior chambers and hybrid bearings. The effects of spiral angle, groove geometry (length, depth and width) and compressibility on performances were investigated for all possible designs.
GENSIM—a compact regression-based model for Coulomb torque in ball bearings
Authors: Todd M. J. 
Published: October 2002

A computable model is described for estimating Coulomb (frictional) torque of a ball bearing under free rolling conditions. The model assumes complete microslip over the contact and makes use of precalculated polynomial regressions to approximate the roll and spin moments and the lateral traction force at each contact. Iterative solution of the force and moment balance equations (with only two unknowns) then allows the Coulomb torque to be found. Use of regressions in this way makes the model compact and efficient at dealing with a wide range of rotational speeds and contact geometries. The range of validity of the model is discussed. From the so-far limited number of field trials, good agreement exists with other codes and experimental data.
Elastohydrodynamic film thickness for shear-thinning lubricants
Authors: Greenwood J. A. , Kauzlarich J. J. 
Published: October 2002

Mineral oils and synthetic lubricants that are thickened by polymers of large molecular weight are being promoted for automobiles as well as aircraft gas turbines. These multiweight lubricants are found to have a complicated Newtonian and non-Newtonian viscosity depending upon shear rate in the bearing. In general, polymer-thickened mineral oil lubricants show a first Newtonian behaviour at a low shear rate, shear-thinning non-Newtonian behaviour at a higher shear rate and a second Newtonian behaviour at a very high shear rate, with a second Newtonian viscosity approximately equal to the base oil viscosity. Because of high shear thinning in the inlet region of rolling element bearings, predicting the film thickness using the low shear rate first Newtonian viscosity can be in error, in particular examples, by a factor of ½ for mineral oil plus 4% methacrylate thickener and 1/7 for mineral oil plus 20% polybutene thickener. The case of naturally shear-thinning silicone fluids is analysed and it is shown that the elastohydrodynamic (EHD) film thickness is nearly the same for silicones with widely varying first Newtonian viscosity. A general EHD analysis for shear-thinning lubricants in pure rolling is presented and shown to agree with known special cases. A closed-form EHD equation for power law shear-thinning lubricants is derived, which gives very accurate results for a bearing where the inlet state of the rolling element falls in the region where the non-Newtonian viscosity is expected. A comparison with some published experimental results by Bair and Khonsari is presented.
Viscosity times density equations for five classes of lubricants
Authors: Kauzlarich J. J. 
Published: October 2002

Viscometers based on wave mechanics measure absolute viscosity times density, λ = ηρ, and lubricant temperature. By using the ISO-VG (ASTM D2422) classification as a continuous (non-banded) system and fitting data for classes of lubricants at Patm, equations relating (a) absolute viscosity times density to (b) temperature and (c) ISO-VG number have been developed with good practical accuracy. Five classes of lubricants have been correlated with ISO-VG numbers. They are paraffinics, naphthenics, PFPE (perfluoroalkylpolyether), diesters and polyol esters.
Prediction of traction in elastohydrodynamic lubrication
Authors: Olver A. V. , Spikes H. A. 
Published: October 2002

The prediction of traction (friction) in lubricated rolling-sliding contacts remains a challenging problem despite the development of the realistic Maxwell-Eyring-limiting shear stress model by Johnson and co-workers in the 1980s. This is largely because there is a strong coupling between the elastohydrodynamic traction and the film temperature. An added complication is that the heat conducted into the rubbing surfaces, as well as influencing traction directly, also determines the temperature in the inlet to the contact and hence the thickness of the elastohydrodynamic film. In the present paper, the traction model of Johnson et al. is combined with a heat transfer analysis of the contacting bodies as well as the film thickness regression equation. In addition, the variations in the lubricant's rheological properties with temperature and pressure based upon the measurements of Muraki et al. have been included. The traction equation is expressed in dimensionless form and is solved using a simple iterative scheme, which in many cases allows estimation of the traction without the use of a computer. Closed-form equations for the friction are given for each of the traction regimes.
Observations on and the modelling of erosive wear of a long-radius pneumatic conveyor bend
Authors: Burnett A. J. , Pittman A. N. , Bradley M. S. A. 
Published: October 2002

This paper describes the results of an experimental investigation of the erosive wear, and puncture, of a long-radius bend in a pneumatic conveyor when used to convey abrasive particles. Measurements were taken of (a) the local air pressure in the pipe bore (used to obtain values of the local superficial air velocity), (b) the mass of abrasive particles flowing through the pipe with time, (c) the reduction in the thickness of the bend wall and (d) the particle concentration distribution using a simple optical obscuration technique. From analysis of the results it was deduced that an accumulation of the particles against the outside bend wall, and the shape of the pipe bore itself, caused the particles to rebound back towards the pipe bore centre-line after primary impact. This behaviour caused an intensification of particle impacts in the region where secondary impacts predominate, and this is where puncture was found to occur. A simple empirical model is proposed for the prediction of the bend wear life. This is based upon an analogy between the particle dynamics in the bend and the optical aberration of a cylindrical mirror of similar dimensions to the pipe bore.
Oil flow in plain steadily loaded journal bearings: Realistic predictions using rapid techniques
Authors: Martin F. A. 
Published: October 2002

The aim of the paper is to produce a rapid calculation method for predicting lubricant flow in plain cylindrical journal bearings. Lubricant flow data, already available from rigorous solutions considering the effect of film reformation, are used together with experimental evidence to develop unique graphical aids and flow prediction equations. These equations, although developed from specific flow data, are of a general form and therefore will be applicable to a wide range of different bearing operating conditions. Graphical aids, from which the flow equations are derived, give normalized actual flow as a function of normalized hydrodynamic flow for different groove geometries. The main input parameters, namely a hydrodynamic flow term Qh and a feed pressure flow term Qp, are easy to derive and have been in common use in bearing design techniques over many decades. The new design aids, in chart and equation form, give realistic flow predictions for bearings with an oil hole, a groove opposite the load line, an axial groove at the maximum film thickness position and the commonly used case of a bearing with two axial grooves. The flow prediction equations are supported by experimental data.
Amplitude reduction of small-amplitude waviness in transient elastohydrodynamically lubricated line contacts
Authors: Venner C. H. , Morales-Espejel G. E. 
Published: October 2002

By means of numerical simulations the amplitude reduction of waviness in a transient elastohydrodynamically lubricated line contact is investigated as a function of slip, under conditions representative of a highly loaded (piezoviscous) situation. Firstly, the case of waviness on one of the surfaces is investigated. It is shown that the behaviour of the deformed amplitude as a function of the sliding velocity can be traced back to the variations in the mass flow induced by the waviness (which are forced by the squeeze term oscillations). The results are compared with recent theoretical work, showing excellent agreement. In particular, the peculiar effect of (significant) amplification of the amplitude (instead of reduction) for short wavelengths under conditions of sliding predicted in this work is confirmed by the presented results. However, for similar conditions it is almost absent if lubricant compressibility is taken into account. Secondly, waviness was assumed on both surfaces. The magnitude of the film oscillations in the centre of the contact has been monitored as a function of the sliding velocity and amplitude ratio. Again the behaviour can be traced back to the squeeze term and mass flow variations. Furthermore, it is shown that, for the conditions considered here, accurate predictions can be obtained on the basis of the results obtained for single-sided waviness. A simple formula is presented.
The modelling and simulation of vehicle handling Part 3: Tyre modelling
Authors: Blundell M V 
Published: October 2002

This is the third in a series of four papers (Parts 1 to 4) looking at the application of computer-based analysis methods to model vehicles and simulate vehicle handling. The material contained in these papers is based on a study carried out in order to investigate the influence of suspension and tyre modelling on the outputs predicted by vehicle handling simulations. The papers deal with analysis methods, vehicle modelling (both in the previous Issue), tyre modelling and handling simulation. In this paper an overview of the use of tyre models in vehicle dynamics is provided. This is followed by a more detailed description of three tyre modelling approaches that can be used for handling simulations. A description is also provided of a computer-based modelling system where FORTRAN routines represent the various models and a computer model of a tyre test rig is used to interrogate the models and data before integrating these into a full vehicle handling simulation. The use of this system to compare the accuracy of the tyre models under consideration is also presented. The examples used to illustrate the concepts explained throughout this series of papers have been generated using the ADAMS (Automatic Dynamic Analysis of Mechanical Systems) program.
The modelling and simulation of vehicle handling Part 1: Analysis methods
Authors: Blundell M V 
Published: October 2002

This is the first in a series of four papers looking at the application of computer-based analysis methods to model vehicles and simulate vehicle handling. The material contained in these papers is based on a study carried out in order to investigate the influence of suspension and tyre modelling on the outputs predicted by vehicle handling simulations. The papers deal with analysis methods, vehicle modelling, tyre modelling and handling simulation. In this paper a review is provided that outlines some of the main contributions leading to the development of models and tools in vehicle dynamics, followed by an overview of the computer-based simulation methodology known as multi-body systems analysis. The way in which multi-body systems analysis can be used to generate models, formulate and solve the equations of motion and post-process the results will be discussed. The examples used to illustrate the concepts explained throughout this series of papers have been generated using the ADAMS (Automatic Dynamic Analysis of Mechanical Systems)program.
Spray propagation and mixture formation in an air guided direct injection gasoline engine
Authors: Adomeit P , Lang O , Pischinger S 
Published: October 2002

Numerical analysis is used to gain information on the spray propagation and mixture formation in tumble guided gasoline direct injection (DI) engines. In order to achieve reliable predictions an atomization model for high-pressure swirl injectors is described and verified by comparison to experimental data. The approach is capable of adequately predicting the most important effects, such as nozzle orifice diameter, cone angle or injection pressure on spray development. Furthermore, it is found that the pre-jet generated at the beginning of the injection strongly affects the overall spray development. The temporal development of the pre-jet is described empirically. The in-cylinder computational fluid dynamics (CFD) analysis reveals that the tumble charge motion strongly affects spray propagation and mixture formation in the stratified operation mode, as it transports the fuel vapour cloud towards the spark plug. The CFD simulation improves understanding of the interaction between the flow field, spray propagation and evaporation and enables guidance of the optimization of the flow control and of the injection parameters for tumble guided gasoline DI engines.
Dynamic simulation of a high-performance sequentially turbocharged marine diesel engine
Authors: Benvenuto G , Campora U 
Published: October 2002

The sequential turbocharging technique is used to improve the performance of highly rated diese engines in particular at part loads. However, the transient behaviour of the sequential turbocharging connection/disconnection phases may be difficult to calibrate and requires an accurate study and development. This may be accomplished, in addition to the necessary experimentation, by means of dynamic simulation techniques. In this paper a model for the dynamic simulation of a sequentially turbocharged diesel engine is presented. A two-zone, non-adiabatic, actual cycle approach is used for the chemical and thermodynamic phenomena simulation in the cylinder. Fluid mass and energy accumulation in the engine volumes are evaluated by means of a filling and emptying method. The simulation of the turbocharger dynamics combines the use of the compressor and turbine maps with a model of the sequential turbocharging connection/disconnection valves and of their governor system. The procedure is applied to the simulation of the Wärtsilä 18V 26X engine, a highly rated, recently developed, sequentially turbocharged marine diesel engine, whose experimental results are used for the steady state and transient validation of the simulation code with particular reference to the sequential turbocharging connection/disconnection phases. The presented results show the time histories of some important variables during typical engine load variations.
Estimates of Worldwide Gas Hydrate Resources
Authors: Lerche I. 
Published: October 2002

Gas hydrates have been touted as the next generation of energy resources exploitable for commercial gain and anthropogenic use. It would then seem relevant to estimate the potential resources available in order that one has an appreciation of availability. Several such estimates have been made over the years for both onshore and offshore gas hydrates. This paper examines the relative percentages and the ranges of uncertainty for both the onshore and offshore estimates. In addition, the estimated resources are plotted versus the year in which the estimate was made to see if any convergence of results is being achieved with time as more data become available. The main conclusions are that there seems not to be any systematic pattern of convergence of resource estimates with time, nor does there seem to be any narrowing of the uncertainty of the estimates for either onshore or offshore resource estimates as more data have become available over the last twenty years. It would seem that a concerted effort is needed to improve estimates if there is to be any hope of assessing the commercial worth of hydrate resources and of deciding whether hydrates really do represent a significant exploitable energy resource on a worldwide basis.
Sidetrack and Recompletion Risks in Oil Fields. I. Recompletion Decisions Based on Estimated Net Present Value
Authors: Lerche I. , Noeth S. 
Published: October 2002

This paper develops a procedure for assessing quantitatively the economic risk associated with deciding whether to undertake a recompletion job for an undeveloped oil-bearing horizon in a producing oil field. Decisions to proceed, or not, with the recompletion depend upon the estimated probability of a successful recompletion and on the estimated probability one will kill the producing horizon in the process. Also of concern are the estimates of total residual production for the producing horizon, the estimates of potentially recoverable reserves in the untapped horizon, together with associated recompletion costs, production costs per barrel, and selling price of product. Because one does not know ahead of performing the recompletion what the chances are of success and kill, then expected values and their uncertainties (as measured by the volatility of the expected value), together with cumulative probabilities of the recompletion worth exceeding the worth without recompletion, and also the expected worth required in order to satisfy a corporate declared mandate of a minimum acceptable chance of improved worth, are all used to provide risk measures to the corporate decision-makers. Several numerical examples are provided to illustrate how one can rapidly evaluate such risky situations in terms of present-day worth values. Considerations of uncertain ranges of parameters involved in the risk assessment, and of models for future inflation rates, selling price time-dependence, and production variations (so that one can provide an assessment of when a recompletion job should be undertaken) are considered in later papers in this series.
Fulfilling the Hand-Arm Vibration Requirements of the EU Machinery Directive
Authors: Brereton Paul , Hewitt Sue 
Published: October 2002

The Machinery Directive was written to facilitate the establishment of the single European market by harmonising Member States' health and safety requirements for machinery so eliminating barriers to trade. The Machinery Directive specifies a hierarchy for selection of methods to eliminate risk of accident or ill-health throughout the foreseeable lifetime of the machine. Designers of new machinery are obliged to: eliminate or reduce risks as far as possible (inherently safe machinery design and construction); take the necessary protection measures in relation to risks that cannot be eliminated; and inform users of the residual risks due to any shortcomings of the protection measures adopted, indicate whether any particular training is required and specify any need to provide personal protection equipment. The Health & Safety Executive (HSE) of the United Kingdom is investigating the hand-arm vibration risks of powered hand-tools and the value of vibration information supplied with the tools. Manufacturers appear to be successfully reducing the vibration emissions of many types of tool. There are many classes of tool that have a wide range in the vibration emissions – frequently up to 4:1 between the highest and lowest emissions in a class. The data provided by manufacturers is likely to provide broad guidance as to which tools are likely to produce the most and least vibration in normal use but often fails to provide an indication of risk.
Biosurfactant-Enhanced Remediation of Oil-Contaminated Environments
Authors: Shulga A. , Karpenko E. , Vildanova-Martsishin R. , Turovsky A. , Soltys M. 
Published: October 2002

The development of new efficient cleaning technologies for the bioremediation of the environment and its cleaning from oil products has become a subject of great interest. Surfactants influence the bioremediation of oil and other organic contaminants through increasing their availability. Since surfactant products of a microbial nature are highly efficient in this respect, they have important advantages over synthetic materials. Being biodegradable, they are ecologically safe. A new washing bioremedy based on surfactant products synthesized microbially from the bacterial strain Pseudomonas sp. PS-17 has been obtained. It contains an unique biocomplex of a glycolipid biosurfactant and an alginate biopolymer and possesses a high surface and emulsifying activity. The washing and antisorptional capacity of this bioremedy has been tested on objects of various natures, viz. bird feathers, animal skins and furs. We have obtained positive results in the remediation of sea sands, birds and animals suffering from ecological catastrophy. It was shown that the bioremedy has mild properties and does not change the structure of the feathers, skins and furs studied. The bioremedy remains active over the temperature range 15–90°C.