bluuebunny/crossref_metadata_2025 huggingface dataset:
The Elastic Contact of Rough Surfaces and its Importance in the Reduction of Wear
Authors: Halling J , Nuri K A
Published: February 2007

The paper considers the conditions for the purely elastic contact of rough surfaces and shows that by considering the effect of the truncation of the asperity distribution, such elastic contact is greater at low nominal pressures than has been hitherto recognized. Experimental studies to define the limits of purely elastic contact confirm the theoretical predictions. It is further shown that purely elastic contact may be obtained up to loads of some 10 000 N/mm2 by using ceramic coatings of titanium nitride deposited by the plasma assisted vapour deposition process.
On the Self Diffusion of Water Vapour
Authors: Bakhtar F , Zidi K
Published: February 2007

Calculated values of the coefficient of self diffusion of steam, based on a theoretical model and covering the pressure range 0.07–27 bar, are presented. By considering the equilibrium vapour pressure surrounding a large droplet placed in its own vapour, its temperature, and hence the temperature field, have been estimated. From the heat transfer rate, the rate of mass transfer and consequently the coefficient of self diffusion have been deduced. The calculations are repeated over a large range of conditions and the results correlated.

Application to the nett mass transfer rate is next considered. By drawing comparisons with the case of a droplet in the free molecule regime and other transport processes, an expression covering the whole Knudsen number range is developed.
Streamline Curvature Effects in Distribution Channels
Authors: Hager W H , Hager K
Published: February 2007

Flow in distribution channels (locally decreasing discharge) is investigated for steady flow conditions by accounting for the effects of slope and curvature of the streamlines. A qualitative analysis indicates that the surface profile is either of the undulatory character for subcritical flow state, or smooth for supercritical flow state. When compared to the approach assuming hydrostatic pressure and uniform velocity distributions, the first deviate from each other throughout, while the second reveal only local deviations. A quantitative insight into the flow processes is given by the numerically integrated model equations, and it is found that the present model allows for an accurate prediction of all pertinent flow parameters.
The Vibrations of Radial Ball Bearings
Authors: Rahnejat H , Gohar R
Published: February 2007

This paper presents a theoretical analysis of the vibration response of a rotating rigid shaft supported by two radial deep-groove lubricated ball bearings. The bearings and their oil films are approximated to a set of non-linear elastic springs and dampers rotating relative to the shaft when it is subjected to a rotating unbalance or inner race surface waviness. Under gravity load, the shaft's initial vibration is damped down to a limit cycle operating at a quasi-simple harmonic frequency of small amplitude. Rotating unbalance and surface features introduce further significant frequencies which influence the output response.
Torispherical Shells under Internal Pressure—Failure due to Asymmetric Plastic Buckling or Axisymmetric Yielding
Authors: Galletly G D , Błachut J
Published: February 2007

In the diameter-to-thickness range 250 < D/t < 1000, internally pressurized torispherical shells can fail either by plastic buckling or by axisymmetric yielding. However, the present Code rules cater only for the axisymmetric yielding mode and they also restrict the D/t ratios to being less than 500. The rules are based on limit analysis results and these can be conservative for this problem. With regard to internal pressure buckling, there are as yet no design rules in either the American or the British pressure vessel Codes to prevent its occurrence.

To provide guidance for a more accurate formulation of design rules for both of these failure modes over the range 300 < D/t < 1500, the authors have made a series of calculations to determine the values of Pcr (the internal buckling pressure) and pc (the axisymmetric yielding pressure) for perfect torispherical shells. The availability of these results, obtained with a finite-deflection shell theory, enables curves to be drawn showing when buckling is the controlling failure mode and when axisymmetric yield controls.

A comparison is also made, for D/t < 600, between the controlling failure pressures mentioned above and the Drucker-Shield limit pressures. The ratio between the former and the latter varied between 1.2 and 1.8, depending on the geometry of the shell and the magnitude of the yield point, σyp. Considerable economies in the designs of many torispherical shells could, therefore, be achieved if the relevant sections of the Codes were to be modified to take advantage of the foregoing results.

The controlling failure pressure curves also indicate how Code rules to prevent plastic buckling for D/t > 500 might be formulated. For the benefit of designers, the numerical values of pcr and pc were transformed, using curve-fitting techniques, into simple approximate equations. Although these equations are for perfect torispherical shells, they should be very beneficial when analysing the related problems of fabricated torispheres in practice.
Identification of Surface Roughness
Authors: Mulvaney D J , Newland D E , Gill K F
Published: February 2007

The Fourier spectral estimates of machined surface roughness data are investigated in detail, and, in particular, the shape of these estimates is examined. From these assessments, a parameter is derived which enables a description to be produced of the underlying form of spectral estimates of machined surface roughness data, without the requirement for a stylus instrument operator to select a standard cut-off filter.
A Signal Processing Technique for Detecting Local Defects in a Gear from the Signal Average of the Vibration
Authors: McFadden P D , Smith J D
Published: February 2007

An approximate digital signal processing technique is presented which can assist in the early detection of local defects such as fatigue cracks in gears by enhancing the changes which these defects produce in the signal average of the vibration of the gear. The technique is demonstrated by the identification of an early fatigue crack in a helicopter gear. The importance of phase modulation in the detection of defects is indicated.
An Experimental Investigation of the Performance of Equiangular Annular Diffusers with Swirled Flow
Authors: Elkersh A M , Elgammal A H , Maccallum N R L
Published: February 2007

An experimental study of the influence of geometrical parameters and swirl on the performance of equiangular diffusers is presented. Three diffusers were tested over a range of inlet swirls up to 45°, the swirls being of free vortex distribution.

The data presented indicate similar flow patterns for different cant angles, and show that the centrifugal forces due to swirl stabilize the flow on the outer wall, while increasing the tendency towards separation at the inner wall. Diffuser performance improves as the inlet swirl increases up to 30°, the improvement being influenced by area ratio and cant angle. A further increase of swirl causes a deterioration of performance.
The Effect of Manufacturing Variations on the Performance of Externally Pressurized Gas-Lubricated Journal Bearings
Authors: Stout K J
Published: February 2007

This paper extends the previous work on the hybrid operation of externally pressurized gas bearings to include the effects of manufacturing variations on design performance of the slot entry configuration. Six aspects of manufacture are considered, and include the departure from the design conditions of (a) bearing clearance, (b) feed slot thickness, (c) bearing form, (d) bearing roundness, (e) bearing member alignment, (f) feed slot geometry.

Computer predictions of the above effects have been made by introducing modifications to the programs developed to model gas bearing performance developed for solution using a finite difference technique. The results show how the load capacity of the bearings is affected by the departure of dimensions from their design conditions. The magnitude of the departure from the design performance is demonstrated in the figures presented.

The performance predictions for the slot entry bearing are compared with results obtained from the orifice compensated journal bearing previously reported. Guidance is given on the limits of departure from initial design conditions which should be allowed for both types of bearing. Confirmation of the accuracy of design predictions has been achieved in this investigation by conducting experiments using test bearings which were very carefully measured to establish the real tolerance on manufacture. These bearings were tested on a specially designed experimental rig.
Fretting Fatigue and Contact Conditions: A Rational Explanation of Palliative Behaviour
Authors: Chivers T C , Gordelier S C
Published: February 2007

This paper considers what palliative effects can be achieved for fretting fatigue by modifying the contact conditions. A previous literature survey of palliatives by the authors is briefly reviewed to demonstrate the contrary nature of much of the evidence. Two simple geometries (sphere and cylinder on plane) are then considered, and the tensile stresses generated in the wake of the sliding contact derived. It is contended that fretting fatigue is the result of such tensile stresses contributing to the crack initiation process. The effect on these tensile stresses of modifying the contact conditions of the friction coefficient and clamping force is examined, so that successful palliatives can be identified. The analysis shows that conditions exist where increasing or decreasing either the friction coefficient or clamping force can be of benefit, and there is no panacea. The correct action depends on geometry, slip regime and the controlling factor for relative displacement. The analysis therefore provides an explanation of the apparent contradictions in the literature. Suggestions are made for the best approach to ameliorate a fretting fatigue problem, given this complicated situation.
Prediction of the Load–Speed Ratings of Ball Bearings with Thermoplastic Raceways
Authors: Hilyard N C , Brown A P , Harrison K
Published: February 2007

Load–speed ratings for acetal ball bearings are derived assuming that the ring temperature is the critical factor and that this is governed by heat build-up due to friction and hysteresis and heat loss by convection.
Origins of Hydrocarbon Emissions from a Multi-Fuel, Torch Ignition Assisted Direct Injection Engine
Authors: LoRusso J A , Havstad P H , Kaiser E W , Rothschild W G
Published: February 2007

Unthrottled, direct injection ignition assisted (DI–IA) engines have demonstrated DI diesel efficiencies and multi-fuel capabilities. However, high hydrocarbon (HC) emissions have been a problem with this concept. Torch ignition, provided by a separately fuelled small volume prechamber with spark ignition, was applied as a research tool to define the benefits of large volume ignition for controlling HC emissions. Torch ignition was found to be beneficial for HC control relative to the use of single point spark ignition; however, HC levels were higher than those observed from a DI diesel using low emissions technology. To assist in investigating the cause of the higher HC emissions, tracer experiments were conducted to verify that prechamber combustion characteristics did not contribute significantly to the total exhaust HC emissions. Separate, but similar, fuels were used for the main chamber and prechamber. Through gas chromatographic analysis of the major exhaust HC species, prechamber combustion was found to contribute substantially less than 20 per cent to the overall HC emissions for the engine conditions studied.
Modelling Total Life Cycle Cost
Authors: Bhadury B , Basu S K
Published: February 2007

In this paper, the concept of terotechnology and the formulation of life cycle cost has been taken from the point of view of the user as against that of the manufacturer, and the stages of design, development of prototypes, manufacture and testing of the machine have not been considered. This is felt appropriate since terotechnology has to date found greater application (and will continue to do so, except for military systems and installations wherein it has possibly found the greatest application) in the case of large capital equipment and machines, for example for process plants, integrated iron and steelworks, power plants etc. The hazard curve provides the basis for the estimation of the time-dependent maintenance cost incurred over the life cycle of an equipment. Accordingly a system study of the hazard rate of power units of a thermal power plant was undertaken and has been presented. Using the modified ‘bath-tub’ curve obtained from the case study and the Weibull model, an equation of the total life cycle cost has been developed. Thus the model takes into account deterioration of components and system performance over time. The model brings out the efficacy of preventive maintenance action in the form of condition monitoring and shows that the total life cycle can be increased if appropriate preventive-maintenance actions are taken in the random failure and wear-out failure regions.
The Design of Mitred Bends—A Background to BS 806 : 1975 Amendment No 3
Authors: Battle K , Carmichael G D T , Cresswell E , Morse D , Porter H , Popplewell P L , Riley K
Published: February 2007

To satisfy a requirement within the high pressure pipework industry in the UK, PVE/10 of the British Standards Institution established a Working Party to produce recommendations on the design and application of gusseted or mitred bends. The ultimate conclusions of the Working Party were eventually published within Amendment AMD 3545 to BS 806 ‘Ferrous pipes and piping installations for and in connection with land boilers’. Prior to this amendment BS 806 provided only limited guidance on the design of such bends, based on rules derived from custom and practice.

AMD 3545 provides more extensive guidance than previously, based on experimental data and analysis and provides guidance on pipework design. This paper describes the background to the amendment and provides most of the reasoning behind the conclusions drawn by the Working Party.
William Dent Priestman, Oil Engine Pioneer and Inventor—His Engine Patents 1885–1901
Authors: Cummins C Lyle , Priestman J D
Published: February 2007

William Dent Priestman (1847–1936) patented in 1885 an internal combustion engine to burn fuels heavier than petrol. Introduced in 1886, it was the first commercially successful engine of its type in the United Kingdom. The biographical paper covers Priestman's engine patents and technical accomplishments as well as business ventures. An assessment of his place in the early history of the development of the internal combustion engine, after 100 years, is discussed.
Expression for the Maximum Efficiency of Compression of a Roots Air Compressor
Authors: Driver R W
Published: February 2007

The poor efficiency of Roots compressors and their relatively low compression ratio are shown by the derived expression to be caused by the downstream ducting volume.
Fluid Transmission Lines—Distributed Parameter Models Part 1: A Review of the State of the Art
Authors: Stecki J S , Davis D C
Published: February 2007

This paper presents a hierarchical classification of linear, distributed parameter models which have been used in the study of rigid, uniform fluid transmission lines. The development of the models from the fundamental equations of fluid dynamics is discussed, and the assumptions necessary in obtaining each model are shown. The solutions to the models are presented in general Laplace forms, and the terms that appear in the solutions are discussed with reference to the initial and subsequent assumptions. The existence of seven distinct forms of models was identified and verified by comparison with a vast number of apparently different models quoted in over three hundred research papers covering various engineering, medical, and biological applications. Significant contributions by various researchers over the last eighty years to the development of distributed parameter models of fluid transmission lines are reviewed. The application of the various models based upon comparisons made in the literature is dealt with, and the effect of the initial assumptions on each model's accuracy is discussed. The aim of the paper is to assist in the identification of areas of research where future efforts should be directed and hopefully to prevent needless duplication of research effort.
The Greater London Council's Refuse-Fired Power Station
Authors: Smart J H S
Published: February 2007

This paper describes how electricity may be generated using refuse as a fuel, and outlines the operation of the Greater London Council's plant at Edmonton which was constructed in 1972. Gives details of the engineering aspects of the plant and reviews its performance since 1972 with particular reference to the problems of corrosion and erosion. Discusses the economic aspects of generating electricity by this means and provides data on the sale of electricity by Edmonton power station to the Eastern Electricity Board and the Thames Water Authority.
Certain Effects of Recirculation on Cavitation in Centrifugal Pumps
Authors: Yedidiah S
Published: February 2007

This paper discusses recirculation at the inlet of a centrifugal pump and how it can affect certain, cavitation-related phenomena.
Cost Effectiveness Through Design Simplicity
Authors: Foreman Philip
Published: February 2007

As is customary, the President first reviews his career from research and development work in the Civil Service to Chief Executive of a significant aerospace business. He then goes on to describe the importance of evolutionary product planning to risk management in the competitive commercial environment in which the engineering designer operates. The contribution of design innovation to cost effectiveness is illustrated by some specific examples from his own experience. The address concludes with some reflections on the tasks of managing an engineering enterprise and of providing appropriate training and education for the engineer of the future.
The Financial Evaluation and Economic Application of Advanced Manufacturing Technology
Authors: Primrose P L , Leonard R
Published: February 2007

The traditional approaches to investment appraisal are examined and it is shown that these exhibit severe limitations when applied to advanced manufacturing technology (AMT). In particular, the financial advantages of AMT are usually understated, with the result that companies fail to invest in highly viable projects. The paper then demonstrates how investment appraisal can be correctly performed by use of an integrated suite of programs, and that when the company-wide benefits of AMT are embraced within the DCF evaluation, AMT emerges as being cost effective. The advantages of using the programs are illustrated by examples from each facet of AMT (for example, robotics, CNC, FMS, CAD/CAM and MRP) with conclusions being derived showing how the traditional objective of reductions in direct costs changes when the investment is viewed company-wide. Finally, it is shown how this change in perspective, in turn, induces a re-appraisal of the direction that AMT development should take if its full potential is to be realized.
The Technical Development and Market Exploitation of Novel Manufacturing Techniques for High Speed Plain Bearings
Authors: Albin F T , Campbell J , Garner D R , Barnes C R , Laws A M
Published: February 2007

This paper describes the realization of the economic volume production of high speed plain bearings with precise profiles specified by advanced bearing performance techniques. Details of the operational, design and manufacturing requirements, together with the manufacturing method adopted, are given. The marketing strategy for the new products and the improvements in productivity attained are outlined.
Education and Deployment of Mechanical Engineers in Japan and Europe
Authors: Hutton S P
Published: February 2007

Based on visits to companies and universities a survey is made of the education and deployment of mechanical engineers in Japan. The results are compared with related surveys made by the author in West Germany and the United Kingdom.
CADCAM in the Aircraft Industry
Authors: Hitch H P Y
Published: February 2007

Reviews the development of CADCAM (computer aided design and manufacture) and CAE (computer aided engineering) in the UK aircraft industry, and describes the systems at present used by British Aerospace in their factories. Discusses communications between systems and how the setting up of networks can overcome problems in collaborative projects. Outlines recent developments in robotics and FMS (flexible manufacturing systems) and reefers to the impact of new materials in aircraft design and manufacturing. Comments on the effect of the new technology on the work-force.
The Salvage of an Engineering Business
Authors: Hoffman M R
Published: February 2007

Outlines the problems which may arise in an engineering business and considers various strategies which may be employed for survival and future success. Discusses the effects of change and emphasizes the importance of human resources, marketing plans, product plans, manufacturing plans, systems plans and the ‘pizzaz’ factor in a company resurrection.
An Analysis of the Transient Nugget Formation in Resistance Spot Welds
Authors: Cho Y J , Boo K S , Cho H S , Na S J , Lee C W
Published: February 2007

An analytical model is presented to describe the transient nugget growth in resistance spot welds. Since an exact analysis of this model is difficult, due to complexities arising from the interaction of heat and electric current flow, and from the melting of the weldment, an approximate solution is proposed by employing the integral method and some previous results obtained by the authors (13). With the aid of this analysis a simplified nugget growth equation is derived, which can be effectively used for the design of an adequate on-line feedback control algorithm. To verify the validity of this model equation, the computed results are compared with those experimentally obtained for the case of welding of mild steels. The comparison shows that the transient nugget behaviour is well predictable by the proposed model for the welding conditions in this simulation study.
Simulating for ‘Resource Optimization’ in Robot-Assisted Automatic Assembly
Authors: Rahnejat H
Published: February 2007

In most manufacturing systems emphasis is now given to resource flexibility in operation. The aim is to respond swiftly to changes in product mix and/or market demands.

Discrete event computer simulation is seen as a tool in defining a suitable system configuration at the preliminary design stage. Furthermore, simulation in dynamic form can represent the interactions between the system components and provide a detailed prediction of its performance.

Although many existing computer simulation packages have reached a good level of general purpose modelling, by and large they lack the required versatility to deal with some specific features of manufacturing systems. One such important area is the robot-assisted automatic assembly where minimization of non-productive activities in the product assembly cycle is of vital interest.

This paper introduces a flexible modelling technique which identifies the resource utilization and optimization levels during the individual processes of a product assembly cycle. Within the working constraints of an assembly system, an ‘optimal’ robot sequential cycle is obtained by implementing this modelling technique in GPSL (general purpose simulation language).
The Education of Student Engineers in the Field of Design for Manufacture
Authors: Fletcher N P
Published: February 2007

This paper describes the approach taken by the Department of Engineering Production at Loughborough University of Technology regarding the input of design and manufacture in their undergraduate degree course: design for manufacture.
Engineers Matter—The Lucas Key to International Success
Authors: Gill A K
Published: February 2007

This paper sets out the reasons why engineers are important in Lucas Industries and goes on to illustrate this by describing the development of Lucas Girling's stop control anti-lock braking system. The concept is explained and the management of the project is outlined with details of the manufacturing systems. The contribution of engineers to such projects in manufacturing industry is stressed and the need for more broadly trained professional engineers is emphasized.
The Impact of Advanced Manufacturing Technology on a Mature Industry
Authors: Mackenzie G R
Published: February 2007

TI Group plc is the largest private sector tube-maker in the UK. Group companies manufacture specialist and bearing tube as well as commodity welded and cold-drawn carbon seamless tube. A substantial proportion of tube output is exported from the UK. Continuing competitive pressures and the changing nature of demand from both home and export markets are forcing reappraisal of TI Group's approach to tube manufacture. TI Group sees the maintenance of manufacturing competitiveness as a key element of securing a profitable future, and policy now requires operating subsidiaries to give full weight to manufacturing considerations when formulating their business strategies.

Against this background, TI Group tube manufacturing companies are devising plans and making fundamental changes to apply advanced manufacturing technology to their processes and manufacturing control systems so as to give a more flexible response to market demand whilst achieving further cost reductions.
Computer Integration of Advanced Manufacture
Authors: Crookall J R
Published: February 2007

An inhibiting misconception in the advancement of manufacturing is the widely assumed inevitability of de-humanization of the workplace, and adverse effects of machines taking over. Manufacturing of the future must be: business-led, and targeted to optimize corporate opportunities; planned, equipped and operated accurately to quantifiable, comprehensible criteria; interfaced with and supportive of the the people who run the system.

Therefore analysis and rationalization of the total manufacturing system and strategy should precede computer integration. Techniques such as production flow analysis and computer simulation are important ways of achieving this, but there are others also; these will be considered in the paper. This results in more logical and efficient processing, materials handling and therefore manufacturing flow and orderliness, promoting an effective basis of visibility, information and control, and maximum benefits from computer integration. The growing science of artificial intelligence will complement conventional software engineering skills.

A key issue is the technical skills and training of literate manufacturing systems engineers and managers. In optimized manufacture human judgement increasingly needs the control and information systems back-up that computer integration is capable of providing, particularly against the background of increasing rate of technological change, greater complexity of tasks and interactions with which companies' corporate manufacturing and marketing strategies will have to deal in the future.
Genius in Engineering
Authors: Jones R V
Published: February 2007

This lecture is addressed primarily to students. It assesses the qualities of some distinguished engineers and their approaches to problems they encountered.
The Teaching Company Scheme—The First Ten Years
Authors: Bradley J A
Published: February 2007

The Teaching Company Scheme sets up partnerships between academic institutions and industrial companies large and small. It is financially supported by the Science and Engineering Research Council, the Department of Trade and Industry, the Economic and Social Research Council, Northern Ireland Department of Economic Development and, increasingly, by industry. It has multiple objectives designed to bring benefits in both the long-term and the short-term to industry, to academic institutions and, by providing post-graduate training and experience, to a cadre of high-quality young technical managers. The development of these partnerships started ten years or so ago, principally in the field of engineering manufacture, but in more recent years they have been developed in other fields as well. The overall structure of the Scheme is described briefly in Section 1, the components of a partnership as ‘a Teaching Company programme’, are described in Section 2. Section 3 provides a profile of the Scheme as it existed in 1985, while Section 4 reviews recent data on the impact of the Scheme on companies, academic institutions and on the young technical managers or ‘associates’. Section 5 looks at the opportunities for and limits to future growth and discusses the utility of the Teaching Company mechanism.
Modelling the Ends of Compression Helical Springs for Vibration Calculations
Authors: Pearson D
Published: February 2007

The squared ends of compression helical springs are modelled as fixed ends with adjacent pinned supports. A theory is developed for the calculation of the natural frequencies, its predictions being compared with experiments on springs with about 2 1/2, 4 and 8 1/2 active turns, using two new designs of test rig. The discrepancy between theory and experiment is typically 1 per cent.

The paper contains discussions of the application of the theory to forced vibration calculations, and the modelling of other types of end. Two methods are reviewed for the design of helical springs with the object of avoiding vibration problems.
On Large Deflection of Symmetric Composite Plates under Static Loading
Authors: Gorji M
Published: February 2007

The effect of transverse shear deformation on bending of elastic symmetric laminated composite plates undergoing large deformation (in the Von Karman sense) is considered in the present paper. The non-linear terms of the lateral displacement are considered as an additional set of lateral loads acting on the plate. The solution of a Von Karman type plate is therefore reduced to that of an equivalent plate with small displacements. This method offers an alternative technique for obtaining non-linear solutions to plate problems. The solutions of a number of example problems indicate that the non-linear shear deformation theory results, as expected, in higher values of the lateral displacement than the non-linear solutions from the classical plate theory. The difference in the values of the maximum displacement from both solutions, however, remains essentially constant beyond a certain value of the load. It is also noted that the linear and non-linear solutions deviate at a low value of w/h (w = maximum lateral displacement, h = thickness). Consequently, the extent of w/h within which the small deflection theory is applicable to composite plates is much lower than the value of 0.4 typically used for isotropic plates and depends, in general, upon lamination geometry and the degree of anisotropy.
The Tribology of Surface Coatings, Particularly Ceramics
Authors: Halling J
Published: February 2007

The development of the chemical vapour deposition and plasma-assisted vapour deposition processes has produced major improvements in the performance of tribological coatings. Such processes produce thin, of the order of a few micrometres, highly adhered coatings for engineering components for improved wear and corrosion resistance. The paper shows the effect of substrate and film materials on tribological performance. With such thin films it is shown that surface finish is of major importance and particular emphasis is given to the behaviour of ceramic films. The paper concentrates on the general physical principles governing the tribological behaviour of thin solid films. It is hoped that this presentation will stimulate interest in further extensions of knowledge and encourage a wider application of coatings in industrial service.
Dynamic Analysis of an Axial Piston Pump Swashplate Control
Authors: Zeiger G , Akers A
Published: February 2007

A mathematical model of an axial piston pump is described which consists of a second-order differential equation of the swashplate motion and two first-order equations describing the flow continuity into the pump discharge chamber and into the swashplate control actuator. The equation of the swashplate angle contains torque components due to operating states. A method is presented by which the average torque can be computed for a pump of given geometry and at any given set of operating conditions. From the calculated average torque, the coefficients of the basic equation can be evaluated; agreement to within 10 per cent of experimental values for torque has been achieved.

A state variables analysis of the dynamic behaviour has shown that there are two dominant poles at low frequency and that the damping ratio associated with these poles reduces by approximately one half when the downstream control volume increases by a factor of three, and varies from 0.84 to 0.48 as the pump rotational speed increases from 126 to 209 rad/s.

It has been concluded that the assumption of linear variation with the basic parameters, which is a necessary prerequisite for the use of states variables analysis, is justified.

The work outlined in this paper represents a step in the design process associated with the optimal control of an axial piston pump.
Flow Characteristics of Opposing Rows of Jets in a Confined Space
Authors: Sivasgaram S , Whitelaw J H
Published: February 2007

The influence of flow and geometric boundary conditions on the interaction of opposed rows of jets in a confined duct without cross-flow has been investigated by a flow visualization method. The effects of angular and axial misalignment of jets and of unequal mean jet velocities were found to be much greater than in configurations with cross-flow, and the effects of geometric asymmetries were more important than those of modest differences in mean jet velocities.
Externally-Pressurized Gas-Lubricated Floating-Ring Porous Journal Bearings Part 2: Dynamical State Analysis
Authors: Malik M , Hori Y
Published: February 2007

Theoretical stability characteristics of a new type of floating-ring bearing, proposed in an earlier paper, are presented. The results bring out the essential features of dynamical behaviour of the proposed bearing against the externally-pressurized plain porous journal bearing.

The numerical scheme for the computation of the stability margin adopted in this work is different, yet simple and very efficient.
Estimation of Squeeze-Film Damping and Inertial Coefficients from Experimental Free-Decay Data
Authors: Roberts J B , Holmes R , Mason P J
Published: February 2007

This paper describes the results obtained from an experimental programme concerned with a parametric identification of the damping and inertial coefficients of a cylindrical squeeze-film bearing, through an analysis of transient response data. The results enable the operating range for which a linear model of the squeeze-film is appropriate to be determined. Comparisons are made between the estimated coefficients and theoretical predictions.
Intake Valve and In-Cylinder Flow Development in a Reciprocating Model Engine
Authors: Vafidis C , Whitelaw J H
Published: February 2007

Measurements of three velocity components have been obtained by laser Doppler anemometry at the exit plane of the intake valve and inside the cylinder of a model engine motored at 200 r/min with a compression ratio of 7.7 and both axisymmetric and off-centre valves with flat and bowl-in-piston configurations. The results indicate that during early intake the valve flow is influenced by piston geometry and its proximity to the cylinder head. With the flat piston the TDC flow field is influenced by the intake-generated axial flow pattern but not by the tangential motion, induced by the off-centre valve, which decays around inlet valve closure. The breakdown of the intake-generated vortices is accompanied by redistribution of the normal stresses which, during compression, tend towards homogeneity. Inside the piston bowl, a vortex is induced during early intake and decays later in the induction stroke to a uniform flow field which is transformed during late compression by the squish effect.
A Power Law Fatigue Damage Model for Fibre-Reinforced Plastic Laminates
Authors: Adam T , Dickson R F , Jones C J , Reiter H , Harris B
Published: February 2007

Following an earlier comparative investigation of the tensile fatigue response, in terms of stress versus log life curves, of three epoxy-resin-based laminates of 0/90 lay-up and reinforced with carbon, glass and Kevlar-49 fibres, the authors now present a study of the accumulation of fatigue damage in terms of the residual strengths of the fatigued laminates. A stress-independent parametric relationship between normalized stress and normalized number of cycles is found to describe the behaviour of all three composites, suggesting a single major mode of fatigue damage despite the widely different mechanical characteristics of the different materials. The model is a two-parameter power law model, derived from a consideration of the appropriateness of various curve-fitting methods, and permits the incorporation of all modes of damage accumulation, from gentle ‘wear-out’ to ‘sudden death’ simply by the adjustment of this pair of power law exponents.
A Characterization of Surface Texture Profiles
Authors: Mulvaney D J , Newland D E , Gill K F
Published: February 2007

The spectral analysis of surface texture data is extended so as to include the longer wavelength ‘waviness’ features in addition to the ‘roughness’ aspects. This results in the identification of an underlying form in the spectral estimates of engineering surfaces whose complete description requires only two parameters. Also, by showing that the spectral estimates converge to a final steady value at the longer wavelengths, the need to select and apply a standard cut-off filter is avoided.
Integral Calculations of Transitional Boundary Layers
Authors: Fraser C J , Milne J S
Published: February 2007

A method is presented for the calculation of two-dimensional, incompressible, transitional boundary layers under small pressure gradient and moderate freestream turbulence conditions. Established integral techniques are used in conjunction with an intermittency weighted model of the transitional boundary layer, and empirical correlations are used to predict the onset and length of the transition region. The only input data required to compute the entire unseparated boundary layer are the ambient pressure and temperature, the freestream turbulence level and the freestream velocity distribution in a power law, or a polynomial form. Alternatively, the freestream velocity can be input in tabular form as a function of x.

The computed integral parameters and mean velocity profiles are seen to compare favourably with present and other published experimental data.
Elastohydrodynamic Film Thickness in Concentrated Contacts: Part 1: Experimental Investigation for Lubricant Entrainment Aligned with the Major Axis of the Contact Ellipse
Authors: Chittenden R J , Dowson D , Taylor C M
Published: February 2007

Experimental investigations of the lubricant film thickness generated in elastohydrodynamic elliptical contacts have been undertaken since the early 1960s. The majority of these studies has been concerned with circular or near circular contact situations, although a wide range of geometries in which lubricant entrainment was directed along the minor axis of the contact ellipse has also been considered. The information available on lubricant film thickness in geometrical conditions where lubricant entrainment was aligned with the major axis of the contact ellipse has, however, been severely limited.

The experimental investigation described in this paper is therefore concerned with the measurement of lubricant film thickness in the unusual geometrical conditions recently analysed theoretically by the authors (1, 2). The measurements were made with the aid of a twin disc machine for geometries ranging from a radius ratio of unity down to a value of 0.112. The experimental apparatus is described and details are given of the special test discs which were manufactured to produce such geometries. The capacitance measurement technique adopted is detailed along with the numerical model developed to allow the measured values of inter-disc capacitance to be interpreted in terms of the lubricant film thickness.

The lubricant film thickness developed in four geometrical situations was investigated at four rotational speeds and five loads. This allowed a comparison to be made with the film thickness values predicted by recent elastohydrodynamic theory for changes in both speed and load. The film thickness deduced from the capacitance measurements was considered to be representative of that found at the centre of contact, and good agreement was found between experiment and all aspects of the theoretical predictions.
Elastohydrodynamic Film Thickness in Concentrated Contacts: Part 2: Correlation of Experimental Results with Elastohydrodynamic Theory
Authors: Chittenden R J , Dowson D , Taylor C M
Published: February 2007

The existence of a coherent film of lubricant between highly loaded machine elements has been recognized for many years. Over this period of time measurements of film thickness have gone hand in hand with theoretical analyses in the field now known as elastohydrodynamic lubrication. The experimental techniques of capacitance, electrical resistance and X-ray measurement have been supplemented by the use of optical interferometry while the analytical expressions obtained with the use of elegant simplifications have been superseded by those developed from extensive and comprehensive computational procedures.

These developments in experimental techniques have yielded a substantial number of measurements of both minimum and central film thickness. Likewise, the advent of the digital computer has allowed the derivation of a large number of solutions to the problem of elastohydrodynamic lubrication of concentrated contacts. All these results, covering a wide range of geometrical conditions, are to be found in the literature, yet little attempt appears to have been made to assemble a representative set of experimental data to permit a detailed evaluation of the theoretical formulae for elliptical contacts.

The second part of this paper therefore considers the correlation between a number of experimental studies covering a wide range of operating conditions and geometries, and the predictions of recent elastohydrodynamic theory. Some of the important aspects of each set of experimental results are then considered and examples are provided which illustrate the following points:

1. Good estimates of lubricant film thickness may be obtained from the theoretical expressions recently derived, even when the dimensionless parameters involved are outside the ranges considered in the derivation of the formulae. 2. The discrepancies which exist between theoretical predictions and some of the measured film thicknesses are nevertheless quite large, even when the dimensionless parameters are within their usual limits.

On the whole there is good agreement between experiment and theory, while the general trend of the results indicates that theoretical predictions may underestimate the minimum film thickness by about 10 per cent and the central film thickness by about 25 per cent. This measure of agreement is quite remarkable when the extreme difficulty of interpreting the magnitudes of effective and very thin mean film thicknesses between machined components in various forms of experimental equipment is considered.
An Experimental Investigation of Pressure Distributions in a Journal Bearing Operating in the Transition Regime
Authors: Roberts J B , Mason P J
Published: February 2007

Experimental results are presented, relating to friction factors and circumferential pressure distributions, for a plain cylindrical journal bearing with a central circumferential inlet groove. The length-diameter ratio of each journal bearing land was 0.25 and the clearance ratio was 0.0031. The friction factor results showed the existence of a distinct ‘transition regime’, characterized by a pronounced ‘hump’ in the friction factor-Reynolds number relationship. Pressure measurements recorded when operating in this transition regime revealed the inadequacy of many existing ‘turbulent’ theories for superlaminar lubrication. By using a short-bearing theory a good correlation of the pressure distribution results was obtained, in terms of a non-dimensional viscosity parameter, kz, which is dependent on both the eccentricity ratio and Reynolds number. The magnitude of kz in this regime was considerably higher than the corresponding value for laminar flow, and was similar to the magnitude predicted from a simple theory based on relating kz to the variation of measured friction factor with Reynolds number.
Sources of Excitation in Tube Banks Due to Vortex Shedding
Authors: Hill R S , Shim K C , Lewis R I
Published: February 2007

This paper describes experimental investigations of vortex shedding patterns in staggered and in-line tube banks consisting of four rows with transverse pitch to diameter ratios PT/d of 2.67 and longitudinal pitch to diameter ratios PL/d of 2.31. Single hot wire probes were used to obtain velocity power spectra in order to identify discrete frequencies of velocity fluctuation. Double hot wire probes provided phase correlations which could indicate conclusively the presence of vortex streets. Quite different results were obtained for the staggered and in-line geometries. While vortex street fluctuations were observed in both, an additional higher frequency fluctuation was observed in the staggered tube bank, the causal mechanism for which remains obscure.
Regimes of Traction in Elastohydrodynamic Lubrication
Authors: Evans C R , Johnson K L
Published: February 2007

The rheological behaviour of the lubricant in an elastohydrodynamic contact depends upon the properties of the fluid and the imposed conditions of load, speed and temperature. For a lubricant of known rheological properties, it is shown how a ‘map’ can be constructed in which different areas of the map correspond to different regimes of behaviour. The coordinates chosen for the map are non-dimensional pressure and a parameter which is closely related to the film thickness. Given the load, speed and temperature, the operating conditions can be located as a point in the map.

Maps have been constructed for three fluids: a mineral oil, polyphenyl ether 5P4E and a traction fluid. In general the maps display four regimes: (a) Newtonian, (b) Eyring, (c) viscoelastic and (d) elastic-plastic. Appropriate constitutive equations are proposed for each regime from which the traction forces can be predicted.

The maximum traction coefficients calculated in this way are well supported by experiment.