bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies of Blood Flow in Arterial Bifurcations Using Computational Fluid Dynamics
Authors: Xu X Y , Collins M W
Published: February 2007

The local blood flow in arteries, especially at bends and bifurcations, is correlated with the distribution of atherosclerotic lesions. The flow is three-dimensional, unsteady and difficult to measure in vivo. In this paper a numerical treatment of blood flow in general three-dimensional arterial bifurcations is presented. The flow is assumed to be laminar and incompressible, the blood non-Newtonian and the vessel wall rigid. The three-dimensional time-dependent Navier-Stokes equations are employed to describe the flow, and a newly developed computational fluid dynamics (CFD) code AST EC based on finite volume methods is used to solve the equations. A comprehensive range of code validations has been carried out. Good agreement between numerical predictions and in vitro model data is demonstrated, but the correlation with in vivo measurements is less satisfactory. Effects of the non-Newtonian viscosity have also been investigated. It is demonstrated that differences between Newtonian and non-Newtonian flows occur mainly in regions of flow separation. With the non-Newtonian fluid, the duration of flow separation is shorter and the reverse flow is weaker. Nevertheless, it does not have significant effects on the basic features of the flow field. As for the magnitude of wall shear stress, the effect of non-Newtonian viscosity might not be negligible.
Electronic Control of Diffusion Through Langmuir-Blodgett Film Membranes
Authors: Mayer T J , Clark D J , Byrne P O , Petty M C
Published: February 2007

A preliminary investigation is reported into the diffusion of a quinine derivative through composite membranes obtained by the deposition of phospholipid Langmuir-Blodgett films on to porous nylon supports. The results suggest that the thin organic layers probably collapse into the pores in the membrane rather than bridge them. It is found that the diffusion of the drug can be influenced by the application of an electric field.
Soft Tissue Biomechanics
Authors: Smeathers J E , Wright V
Published: February 2007

This overview paper summarizes recent work on the biomechanics of soft tissues relevant to biomedical problems, prosthesis design and interventions, with reports on the papers presented at the Nineteenth Annual Day Conference, held in Leeds on 7 January 1994, by the Bioengineering Group for the Study of Human Joints in association with the Biological Engineering Society.
Contact Mechanics of Soft Layer Artificial Hip Joints: Part 2: Application to Joint Design
Authors: Yao J Q , Parry T V , Unsworth A , Cunningham J L
Published: February 2007

In this paper, the general solutions previously obtained for the contact mechanics of a soft layer artificial hip joint have been applied to the design of such joints. In particular, simple power-law design formulae have been generated for the prediction of the contact radius and the maximum Tresca shear stress within the elastomeric layer, when the aspect ratio varied from 1 to 20 (which covered the entire range of the aspect ratio for soft layer artificial hip joints). The effects of the layer thickness, Young's modulus of the layer and the equivalent radius of the joint upon the contact area and the maximum Tresca shear stress have all been examined for physiological loading conditions which would be experienced by hip joint prostheses in the body.

Furthermore, the shear strain field was calculated so that the level of strain expected for such joints under physiological loading conditions can be estimated. With these data, relevant fatigue tests can be devised to assess the long-term performance of any particular design of soft layer hip joint.

Finally, the effect of the friction between articular surfaces upon the stress field within soft layers has been examined using a newly developed asymptotic analytical theory. It was shown that, for a low coefficient of friction, the maximum Tresca shear stress occurred at layer-substrate bonding interface. With an increase in the coefficient of friction, however, the maximum Tresca shear stress increased its magnitude and moved towards the centre of the contact area along the articular surface.
The Contribution of Different Tissues to Stiffness of the Wrist Joint
Authors: Helliwell P S , Smeathers J E , Wright V
Published: February 2007

Passive articular stiffness is not only a function of articular tissues, but also tissues associated with movement, such as muscles and tendons. Allowance has been made for the relative contribution of these extra-articular tissues in comparing the resting stiffness of normal subjects and patients with rheumatoid arthritis. In addition, the stiffness of the muscle-joint complex with agonist/antagonist muscles co-contracting has been measured. Significant muscle wasting was found in rheumatoid arthritis (forearm muscle cross-sectional area for normals: 30.9 cm2, for rheumatoid arthritis: 22.7 cm2, p = 0.002). Allowing for this, there was a significant difference in resting stiffness between normals and rheumatoid arthritis subjects (adjusted resting stiffness normals: 90.8 × 10-3 Nm/deg, rheumatoid arthritis: 120.3 × 10-3 Nm/deg, p = 0.015). There was no difference between the groups in terms of the relationship between stiffness and grip at different levels of muscle co-contraction, suggesting the muscles are qualitatively normal in rheumatoid arthritis.
Non-Linear Adaptive Control of Robots Including Motor Dynamics
Authors: Ge S S , Postlethwaite I
Published: February 2007

This paper addresses the theoretical aspects of non-linear adaptive control of robots when motor dynamics is included. It is shown that the resulting third-order dynamic models can be transformed into an attractive form, under moderate assumptions, to which the most recent controller design methods are applicable. The third-order model retains important properties (properties 1, 2 and 3 in the paper) which are present in the second-order rigid-body models of robots. Control methods are proposed to tackle two main issues: parameter adaptation for unknown dynamic parameters and robustness in the sense of modelling errors. It is shown that the control methods for rigid-body robots can easily be extended for higher order systems that possess properties 1, 2 and 3.
Pole-Placement Position Control of a Hydraulic Robot Arm
Authors: Özsoy C , Kural A , Kuzucu A
Published: February 2007

This paper discusses a single-input single-output discrete-time model developed to control joint position of a manipulator design for painting purposes. The input of the discrete-time model is the voltage into the control valve, and the output is the joint displacement. The model parameters are identified by using input-output data collected from the actual system. Recursive least-squares, square root, V-D factorization and variable forgetting factor methods were used for the estimation, and a good match between the model and actual system responses was obtained. The best estimation results were found by the U-D factorization algorithm according to the sum of the squared errors. Since identification results indicate a non-minimum phase system, a pole-placement self-tuning controller is designed for the purpose of joint trajectory control. The control signal computed off-line is applied to the electrohydraulic drive system and the perfect performance of the pole-placement controller is shown by the experimental studies.
Robust Non-Linear H∞/Adaptive Control of Robot Manipulator Motion
Authors: Feng W , Postlethwaite I
Published: February 2007

In robotics, despite considerable effort to minimize system modelling errors, uncertainties are always present and sometimes significant. In this paper, modelling errors are first represented by a class of bounded disturbances in the input channels (torques) of the robot. A measure of the robot system's ability to reject these disturbances is formulated in an L2 gain sense and a control design is subsequently proposed to achieve optimal disturbance rejection. If more detailed information is available on the plant-model mismatch, then the control design can be modified to incorporate an adaptive scheme (with explicit parameter updating laws) in order to reduce the conservativeness of the original design and to improve robust performance of the overall system.
The Effect of Different Propellants upon the Barrel Wear Rate of Medium-Calibre Cannon
Authors: Allsop D F , Howes J
Published: February 2007

Firing trials were carried out on the 30 mm calibre RARDEN cannon to measure the wear rates for four different propellants and two different projectiles. The thin-layer activation technique was used for measuring the wear rate of the barrel, thus enabling wear to be measured after firing as few as two rounds. It was found that, for the same conditions, wear rates varied by up to twenty times for different propellants, while for the same propellant wear rates for the two projectiles were similar.
Soap-Thickener Induced Local Pressure Fluctuations in a Grease-Lubricated Elastohydrodynamic Point Contact
Authors: Åström H , Venner C H
Published: February 2007

In several experimental investigations of grease-lubricated elastohydrodynamic (EHD) contacts indications of soap-thickener formations that enter the contact area have been reported, for example by Kageyama et al. (1), Cann and co-workers (2-4) and Åström and co-workers (5, 6). While passing through a contact such soap-thickener lumps significantly disturb the film thickness by locally increasing the surface deformation. These film-thickness fluctuations must be accompanied by pressure fluctuations, knowledge of which is essential to increase insight in the phenomena determining service life and emitted noise of grease-lubricated contacts. In this paper the authors present a combined experimental/numerical approach to generate insight into such pressure fluctuations. From a fringe pattern obtained with optical interferometry (ball-on-disc apparatus) a film-thickness map is created employing image analysis. This map serves as input to a numerical algorithm for the calculation of the pressure from force balance and elastic deformation theory. Consequently, no assumptions about the rheological behaviour of grease can be made.

The method was first tested out on an oil-lubricated contact. This test gave essential insight into the accuracy of the method proposed here and in the magnitude of surface texture induced pressure fluctuations. Subsequently the approach was successfully used to estimate the pressure variations resulting from soap-thickener formations in a grease-lubricated contact (between the same ball and disc).
Measurement of Lubricating Film Thickness in Low Elastic Modulus Lined Bearings, with Particular Reference to Models of Cushion Form Bearings for Total Joint Replacements: Part 1: Steady State Entraining Motion
Authors: Jin Z M , Dowson D , Fisher J , Rimmer D , Wilkinson R , Jobbins B
Published: February 2007

The lubricating film thickness in a model of compliant layered bearings for total joint replacements has been measured by means of optical interferometry under entraining motion. The essential features of the present interferometry technique were off-normal incidence light, a combination of polyurethane elastomer and a crown glass plate as bearing surfaces and the use of silicone fluid or water as lubricants. The film thickness in the lubricated contact was measured for both water and silicone fluid under a range of entraining velocities. Reasonable agreement was found between the experimental measurements of the lubricating film thickness and the theoretical predictions based upon elastohydrodynamic lubrication analysis.
Effects of Speed on Scuffing in Mixed Lubrication
Authors: Kelly D A , Barnes C G
Published: February 2007

Theories of failure of elastohydrodynamic lubrication are briefly reviewed, but none that relate to scuffing per se and no general criterion that accounts for the sensitivity of scuffing to rolling as well as sliding speed are found. A theoretical investigation of micro-EHL by Baglin, for surface finishes with a lay parallel to the sliding direction, predicts boundaries in the operating condition domain to a regime of mixed lubrication in which little elastic deformation of asperities by micro-EHL is expected.

A new thermal model incorporating salient features of scuffing in mixed lubrication conditions is described. It is shown to give the form of a boundary in the sliding/rolling speed domain above which localized temperatures close to melting may be expected and below which lower temperatures suggest running-in without scuffing may be expected.

Results of scuffing tests on circumferentially ground discs, at sliding and rolling speeds in the range 3-10 m/s, are reported and shown for surfaces with a distinguishable mainscale wavelength in their topography, (a) to provide further support for the location of the boundaries to the mixed lubrication regime in the operating domain predicted by Baglin and (b) to match the form of the thermal model in the speed domain. Implications for engineering practice are briefly discussed.
Metallic Sliding Friction under Boundary Lubricated Conditions: A New Method for Measuring the Appropriate Shear Strength of Lubricants
Authors: Black A J , Kopalinsky E M , Oxley P L B
Published: February 2007

An experimental method is described for measuring the shear strength of lubricants for conditions similar to those encountered at the interfaces of contacting asperities in metallic sliding friction. Results are given for a number of lubricants including commercially available motor oils. The significance of the results is discussed.
Managing the Future of the Power Industry
Authors: Devaney J
Published: February 2007

The power industry is one that is currently undergoing great change—a trend likely to continue in the future. As it does so, I believe the role of the manager and the engineer within it will change significantly, providing a challenge to those who are schooled in the old ways and with implications for new engineers emerging from universities and training programmes. I would like to share my thoughts on this with you, starting with discussing a little of the background of how the industry has developed and moving on to how it might look in the future and what that would mean for engineers working within it.
Thermodynamic and Detail Design of a 0.5 kW Stirling Engine for Domestic Scale Cogeneration
Authors: Rix D H
Published: February 2007

This paper describes the principal aspects of the thermodynamic and detail design of a prototype Stirling engine, primarily intended to be mass produced for use in a domestic scale combined heat and power (CHP) system. These include the design of the natural gas fired burner, the heat-transfer system (the regenerator and the cast compression and expansion space heat exchangers) and the crankdrive The latter includes the use of dry running bearings and seals, in answer to the inherent lubrication and gas sealing problems of the Stirling engine.
Cold Generation Systems: A Theoretical Approach
Authors: Tozer R M , James R W
Published: February 2007

The objective of this study was to derive the thermodynamic formulae for ideal combined driving and cooling cycles when the objective of the overall cycle is to produce cooling by using a high-temperature heat source. For this it has been necessary to investigate absorption cooling thermodynamics and to focus on the analysis of one-, two- and three-stage cycles and multi-stage cycles in general. This paper has investigated the absorption thermodynamic principles involved to obtain simple formulae, in a similar way to the Carnot cycle. The first driving cycle considered has a high-temperature source such as a combustion process. From this driving cycle the heat dissipated at the lower temperature is used to drive the next consecutive driving and/or absorption cooling cycles. All the work produced in the driving cycles is used for the cooling cycles with mechanical compressors, whereas the dissipated heat of the last driving cycle is used to drive the absorption cycles. A simple universal law for driving and cooling cycles has been derived, which is applicable to combined heat and power (cogeneration) systems.
Wind Farm Economics
Authors: Milborrow D J
Published: February 2007

The economics of wind energy are changing rapidly, with improvements in machine performance and increases in size both contributing to reduce costs. These trends are examined and future costs assessed. Although the United Kingdom has regions of high wind speed, these are often in difficult terrain and construction costs are often higher than elsewhere in Europe. Nevertheless, wind energy costs are converging with those of the conventional thermal sources. At present bank loan periods for wind projects are shorter than for thermal plant, which means that energy prices are higher. Ways of overcoming this problem are explored. It is important, also, to examine the value of wind energy. It is argued that wind energy has a higher value than energy from centralized plant, since it is fed into the low-voltage distribution network.
Requirements for a Tidal Power Demonstration Scheme
Authors: Young R M
Published: February 2007

If in the future it is decided to progress the British tidal power programme, the next logical step will be to build a demonstration scheme. Criteria for selecting a suitable demonstration scheme site are set out and a number of candidates identified, making use of a survey of small estuaries carried out by Binnie and Partners in 1986. These candidates are compared in the light of the information they are likely to produce and of the probable investment required.
Interaction of Process and Machine in Multi-Stage Forging on a Mechanical Press
Authors: Zhang H G , Dean T A
Published: February 2007

This paper presents a mathematical model which provides a basic description of the force and displacements arising in multi-stage forging on a mechanical press. Given the stiffness of tools and press structure, for a given operational sequence, the variations in shut-height caused by deflections of tools and press during forging, compared with that under no load conditions, can be determined. Also the effect of a change in process conditions at one forging station on forces and dimensions of workpieces produced at other stations can be calculated. The model has been validated by experiments undertaken on a crank press in which upsetting and extrusion have been performed as both single and simultaneous operations.
A Numerical Method for Determining Temperature Distributions in Machining with Coolant: Part 2: Calculation Method and Results
Authors: Li X , Kopalinsky E M , Oxley P L B
Published: February 2007

A computational method is developed for determining temperature distributions in machining with coolant. Models for heat sources and equations for heat-transfer coefficients used in the calculations were presented in Part 1. In Part 2 the finite element method is applied to solve the steady two-dimensional energy equation with a coolant used on the boundaries. Using this method temperature distributions throughout the tool, work and chip in machining with coolant are calculated, given the experimental values of the cutting forces and chip thickness, the thermal properties of the work and tool materials and the heat-transfer coefficients at the boundaries. The calculated tool temperatures are compared to results measured experimentally and satisfactory agreement is shown.
Selection of Cutting Regime for Self-Propelled Rotary Cutting Tools
Authors: Chang X , Chen W , Pang X , Zhong G
Published: February 2007

A self-propelled rotary cutting tool (SPRT) can be used in metal machining at higher cutting speeds with much longer tool life than conventional cutting tools because of the continuous rotation of its round tool insert driven by cutting force. The paper presents a theoretical calculation of cutting speed and feed rate for the SPRT together with practical concerns. Based on the research results and industrial experience the principles for choosing depth of cut in turning and face milling and general considerations concerning the application of the tools are detailed.
Role of Surface Tension Driven Convection in Pulsed Laser Melting and Solidification
Authors: Ravindran K , Srinivasan J , Marathe A G
Published: February 2007

Surface melting by a stationary, pulsed laser has been modelled by the finite element method. The role of the surface tension driven convection is investigated in detail. Numerical results are presented for a triangular laser pulse of durations 10, 50 and 200 ms. Though the magnitude of the velocity is high due to the surface tension forces, the present results indicate that a finite time is required for convection to affect the temperature distribution within the melt pool. The effect of convection is very significant for pulse durations longer than 10 ms.
A Study of the Monitoring and Suppression System for Turning Slender Workpieces
Authors: Yeh L-J , Lai G-J
Published: February 2007

The main purpose of this study is to develop a chatter monitoring and suppression system while turning slender workpieces. In order to clarify the chatter behaviour, the ratio of the length to diameter of the cylindrical bar (L/D ratio) is considered as an independent parameter. Experimental investigations were carried out over a wide range of the L/D ratio and cutting conditions to identify the cutting stability. It can be observed that the standard deviation value of the main cutting force obviously increases in the chatter developing period, and this phenomenon can be used to define the chatter threshold. From the observation on the variation of the standard deviation value of the cutting process and then by means of a reasonable application of the standard deviation value, a precise on-line chatter threshold based on the double-standard concept has been defined in this paper. For an accurate judgement of the chatter occurrence, an effective monitoring criterion was proposed and developed. This monitoring criterion was applied to the feed rate control system to suppress the chatter vibration by increasing the feed rate. Experimental results show, furthermore, that the control system is effective when the L/D ratio is smaller than 12.
Surface Topography Measurement Using Digital Moirè Contouring—Errors and Limitations
Authors: Wykes C , Morshedizadeh R
Published: February 2007

Moiré contouring is a technique that enables the surface topography of an object to be measured in a single view and has a wide range of potential applications in manufacturing. However, to be useful, it is necessary to be able to calibrate the system and establish the traceability of the calibration. In this paper, the factors that determine the accuracy of the technique are identified, methods of calibration proposed and attainable accuracies estimated. These include the optical magnification, phase measurement and sensitivity, all of which contribute to measurement errors in the technique. The methods are illustrated with results from a digital moiré system, and the improvements required to obtain maximum accuracy are outlined.
Towards Intelligent Process Control of Injection Moulding of Polymers
Authors: Coates P D , Speight R G
Published: February 2007

Steps towards process control of the complex, multi-variable injection moulding process are presented. In-process measurements, in particular melt and hydraulic pressures in the primary injection stage, are shown to provide a sensitive means of monitoring changes in the process and changes in the polymer feedstock. Correlations have been observed between real time process measurements, in the form of specific time integrals of melt and hydraulic pressure, and product quality measures, such as product weight or dimensions. The research has been validated in both scientific laboratory and factory studies, and for a range of polymers, injection moulding technologies and complexities of product. Such correlations, and the specific integrals upon which they are based, can therefore form the basis of meaningful statistical process control for injection moulding or a viable closed-loop control strategy.
Two-Dimensional Fast Fourier Transform and Power Spectrum for Surface Roughness in three Dimensions
Authors: Dong W P , Stout K J
Published: February 2007

Two-dimensional power spectrums of engineering surfaces contain plenty of information that is important and valuable for surface characterization. However, the characteristics of the two-dimensional spectrums are largely unknown and the algorithm to implement them is not familiar to many engineers or researchers. This paper describes a detailed procedure to implement the two-dimensional fast Fourier transform and power spectrum for surface roughness in three dimensions. Methods used to extract information from the spectrums are introduced. In order to perform two-dimensional spectral analysis and to have a comprehensive understanding of the characteristics of engineering surfaces, an atlas of the two-dimensional spectrums of representative engineering surfaces are presented. The properties of the spectrums are discussed in conjunction with theoretical analysis and visual characterization of the presented spectrums.
A Study of the Effect of Pre-Straining on Angular Distortion in One-Pass Fillet Welding Incorporating Large Deformation Theory
Authors: Bae K-Y , Na S-J
Published: February 2007

By using the finite element method based on the large deformation theory, the effect of pre-straining on angular distortion of one-pass fillet weldments was analysed for the free-end and constrained-end condition. Pre-straining by an additional concentrated load caused a large thermal deformation during heating, and reduced the reverse distortion during cooling and consequently the residual distortion. Geometric change of the fillet weldment caused by pre-straining during welding induced an initial stress effect on the stiffness to the further deformation, which is due to a developed in-plane stress. This initial stress effect could be considered in the large deformation theory to be based on the updated Lagrangian method, while it could not in the small deformation theory. As the pre-straining load increased in the free-end condition, the initial stress effect also increased. In the constrained-end condition, the initial stress effect played an important role in the deformation of the fillet weldment, even without pre-straining. By comparing the results predicted by the large deformation theory with those by the small deformation theory and experiments, it can be shown that the large deformation theory is able to describe the distortion phenomenon in fillet welding reasonably well.
Process Modelling and Formulation for the Development of an Intelligent Set-up Planning System
Authors: Ong S K , Nee A Y C
Published: February 2007

A set-up is a group of features that are machined together in one particular orientation and position of a workpiece. Hence, the task of set-up planning is to group the features that are required on a part into set-ups and sequence these resultant groups to form an optimally ordered plan to produce the part. This ordered plan has forthright effects on the process and fixture plans that are needed to produce this part. This paper presents the knowledge modelling and formulation process for the development of an intelligent set-up planning system. The knowledge-based information needed for set-up planning from experts in the machining domain and the problem-solving procedures of these experts were obtained from a knowledge acquisition process and modelled in this set-up planning system. The acquired knowledge is modelled using production rules and fuzzy sets, and is coupled with a fuzzy-set-based formulation of the problem-solving procedures of these experts. This formulation and a control framework for set-up planning that closely emulates the expert's thinking processes during planning are integrated to formulate set-up plans.
An Optimal Tool Replacement Strategy for Computer Numerical Controlled Turning Centres
Authors: Arsecularatne J A , Mathew P
Published: February 2007

For a computer numerical controlled (CNC) turning centre with a multi-station tool turret, this paper describes a tool replacement strategy for tools used for both rough and finish turning, boring and facing operations as well as other end operations which include drilling, grooving, threading and parting-off. The method ensures a convenient replacement strategy where tools in the machine turret are replaced after machining integer multiples of an optimum number of components. This optimum number of components is determined so that the total cost due to tools and tool changing time is minimized. An example is given to illustrate how the procedure determines the optimal tool replacement strategy. It shows that the described method can substantially reduce the number of interruptions due to tool replacements in processing a batch.
Stresses and Deformations in Elastic Layers Indented by a Conical Punch
Authors: Jaffar M J
Published: February 2007

The numerical solutions to problems of the contact between an elastic layer in complete adhesion with a rigid foundation (bonded layer) or resting without friction on a rigid foundation (unbonded layer) and a frictionless rigid cone (conical punch) are presented. The present numerical scheme is a modification of that developed by the author for a smooth indenter profile. The modified analysis uses the Fejér method in order to eliminate completely the Gibbs phenomenon at the neighbourhood of the singularity. Calculations are performed to examine the effects of the layer thickness and/or the layer compressibility on the results. It was found that as the layer thickness was decreased then the contact pressure approaches a triangular form for unbonded layer and bonded layer with Poisson's ratio v < 0.5; for an incompressible layered surface (v = 0.5) the pressure gradient tends to zero at the contact ends. Moreover, the contact radius and the surface deformation depend not only on the layer thickness but are also influenced by the layer compressibility. The present method showed excellent agreement with the existing solutions when the layer becomes either a half-space or thin.
A Generalized Approach for the Kinematic Analysis of Planar Mechanisms
Authors: Simpson D J A , Simmons J E L , Moldovean G
Published: February 2007

This paper describes a new approach to the kinematic analysis of planar mechanisms. The basis of the analytical method is a generic four-bar sub-mechanism which is used as the single building block from which other composite mechanisms may be created. A computer program has been written embodying this method and has been demonstrated to operate successfully providing animated displays of displacement, velocity and acceleration diagrams for a wide range of complex mechanisms.
An Investigation of Road Damage Due to Measured Dynamic Tyre Forces
Authors: Potter T E C , Cebon D , Cole D J , Collop A C
Published: February 2007

A portable mat for measuring the dynamic tyre forces of commercial vehicles is described. The mat is 56 m long, 13 mm thick, and has 141 capacitative strip sensors, spaced at 0.4 m intervals. The accuracy of the mat for measuring dynamic tyre forces generated by heavy commercial vehicles is assessed using an instrumented vehicle. The measured dynamic wheel loads generated by 14 articulated vehicle configurations (three tractors with five trailers) are assessed in terms of a variety of road damage criteria. The results are used to investigate the effects of vehicle configuration, vehicle dynamics, speed, road strength, and road damage criteria on the relative theoretical road damage caused by the vehicles. Conclusions are drawn about tests for measuring and assessing the road-damaging potential of heavy lorries.
Possibilities for Reduction of Tyre Wear Through the Design Parameters of the Steering Axle
Authors: Ivanov R , Liubenov S
Published: February 2007

Two conditions for minimal wear of the front wheel tyres are defined. Methods to comply with these conditions through the design parameters of the steering axle are stated. An optimization of the steering axle parameters of a concrete agricultural tractor was performed using the formulated conditions. An experimental corroboration was finally carried out.
Prediction of Compressible Subsonic Flow through an Axisymmetric Exhaust Valve-port Assembly
Authors: Naser J A , Gosman A D
Published: February 2007

Flow details through an axisymmetric exhaust valve-port assembly have been investigated numerically. Computations were performed for steady compressible subsonic air flow at different valve lifts. The numerical procedure used for this purpose solves the governing equations using the SIMPLE algorithm. The governing equations are expressed in a general curvilinear coordinate system and are discretized in a finite volume fashion. The time-averaged governing equations are closed using the k–e. turbulence model. The predictions are assessed by comparing with the available experimental flow field data. Good agreement is observed between the predictions and the experiment.
Comparisons of Drill String Cyclic Loading Due to Vibration and Dog-Legs
Authors: Patel M H , Vaz M A
Published: February 2007

This paper presents an investigation of the cyclic loading on oilfield drill strings due to longitudinal, torsional and lateral vibrations and compares this with the ‘statical’ cyclic loading caused by a deviated string at a dog-leg. Such cyclic loading is a principal contributor to drill string fatigue failures. The methodology of the paper uses numerical dynamic analyses of longitudinal and torsional vibrations together with quasi-static models for lateral vibration and dog-legs to compare the cyclic loading induced separately by each of these effects. A linear damage law (that is Miner's rule) is used to calculate the resultant fatigue damage from the cyclic loading. The results of this investigation show that longitudinal and torsional vibrations may induce significant cyclic loading comparable to that from typical dog-legs whereas the influence of lateral vibration is small. The longitudinal and torsional vibrations are strongly influenced by rotary speed and damping coefficients and can induce significant cyclic loading and rapid accumulation of fatigue damage on drill pipes and collars.
An Expert System for the Integrated Design of Heat Exchangers
Authors: Abou-Ali M G , Beltagui S A
Published: February 2007

The selection of a shell-and-tube heat exchanger type and geometry is one of many engineering applications, where a wide range of specialized knowledge is available as qualitative rules that can be incorporated in an expert system.

This paper presents a technique used for building a knowledge-base system utilizing object-oriented expert system shells. The described steps of system development are: identifying the sources of information, building the knowledge base and finally the production of the runtime program.

The constructed prototype system assists the designer in making decisions about fluid allocation, selection of TEMA (Tubular Exchanger Manufacturers Association) shell type, bundle, heads and various geometrical details. The ultimate aim of developing an expert system of this type is to achieve an integrated design procedure covering all considerations from initial selection to the final thermohydraulic and mechanical design.
Structural Failures of Bulk Carriers
Authors: Jubb J
Published: February 2007

Structural failures of bulk carriers continue at a steady and unacceptable rate, claiming some 150 lives per year. This paper explains why bulk carriers are vulnerable to structural failure either because side shell plating falls out allowing ingress of seawater or the deck cracks open. Inadequate detail design, material without guaranteed fracture toughness and limitations of current inspection programmes are identified as fundamental weaknesses. The paper includes important information from a case study of six oil bulk ore carriers prone to deck cracking. One of the group of six which sank in 1980 was traced 4200 metres down on the floor of the Pacific Ocean in June 1994 and the results of this initial search are reviewed.

There is a genuine need to go back to basics. Designing from first principles to determine local stresses is an important first step rather than the current use of prescriptive rules. All subsequent steps in bulk carrier construction and maintenance should be subject to a penetrating review.
The Analysis of Leakage in a Twin Screw Compressor and its Application to Performance Improvement
Authors: Fleming J S , Tang Y
Published: February 2007

The performance of a helical screw compressor is influenced more by the internal gas leakages than by any other thermo-fluid aspect of its behaviour. Six separate types of leakage path can be identified. Only the cusp blow holes have a constant geometry; every other path has a geometry and resistance to flow which varies (periodically) in a manner unique to it. The pressure difference driving the gas along a leakage path also varies (periodically) and does so in a manner that is not the same for every leakage path. This is quite obviously a complex problem requiring insight in modelling the thermo-fluid behaviour and the solution of a large number of simultaneous equations.

The distribution of leakage through the various leakage paths within the machine is important for the improvement of the compressor performance. A method of determining the aggregate leakage through each path individually over a complete compression cycle is required to enable this study to be conducted. The authors have constructed a mathematical model of the complete compressor thermofluid process which is suitable for this purpose, its macropredictions having been verified against measured data derived from a test compressor. The nature of its micropredictions and their verification, that is for each leakage path, are the subject of the paper proposed here. Analytical techniques are proposed and experimental methods are discussed. The influence of different rotational speeds on the leakage is considered. Also discussed is the manner in which the leakage distribution prediction could be used to optimize a compressor design.
Diesel Locomotive Reliability Improvement by System Monitoring
Authors: Fry K N
Published: February 2007

System monitoring for reliability (SMR) involves monitoring critical parts of a vehicle and informing the owning business of an impending fault. Diesel locomotives offer the largest opportunity for such systems and British Rail Research has developed a system designed to improve Class 47 locomotive reliability.

The vehicle-mounted equipment comprises a computer that continuously monitors the condition of the vehicle through sensors at key points. The computer is connected to a radio telephone and modem and a GPS satellite navigator. The key elements in the success of the system are the automated analysis of data on-board the vehicle and its ability to call for help ahead of the occurrence of service failures. The business interface is through a Windows based information display which runs on a personal computer connected to the public telephone network. This controls the display of messages from monitored vehicles and allows vehicles to be interrogated to check on current condition.

When fully implemented, a reduction in technical casualties of 40 per cent is anticipated. There are additional financial benefits from efficiency improvements and vehicle maintenance cost savings.
Analysis of Modified Railway Passenger Truck Designs to Improve Lateral Stability/Curving Behaviour Compatibility
Authors: Swamy S Narayana , Dukkipati R V , Osman M O M
Published: February 2007

Modified railway passenger truck designs are considered to improve the compatibility between dynamic stability and the ability of the vehicle to steer around curves. A comparative study on the non-linear steady state curving behaviour of some unconventional truck designs is carried out. The study reveals that modified truck designs with primary yaw dampers improve the performance. A particular design of railway truck in which the rear axle is an independently rotating wheelset and in which the primary suspension in the leading axle is different from the trailing axle—known as the unsymmetric wheelset and suspension truck—has the potential to achieve overall superior performance compared to other truck models considered in this paper, for design speeds of around 80 m/s. For the lower design speed of around 60 m/s, a conventional truck provided with primary yaw damper achieves adequate performance and is recommended for its simpler design features.
Development of Hybrid Rail Brake
Authors: Obara T , Kumagai N , Takiguchi T
Published: February 2007

In Japan three types of rail brake were tested in the field. They were the eddy current rail brake, the electromagnetic rail brake, and the hybrid rail brake. The eddy current type, which does not come into contact with rails, needs high current and greatly increases the temperature in rails. The electromagnetic type which attracts rails and achieves braking by frictional force cannot generate a stable braking force. Therefore the authors developed a hybrid rail brake, which has advantages over the other two types. This type does not need as much current, and keeps rail temperature low.
Cooling Methods for Railway Tunnels
Authors: Barrow H , Pope C W
Published: February 2007

In this paper the cooling of a railway tunnel and its environment is investigated, with particular reference to a study of possible methods for reducing both local and overall average tunnel air temperatures. Both passive and supplementary cooling of a tunnel are considered and then various practical systems are proposed for those situations where passive cooling alone may be inadequate. In some cases, calculations for realistic conditions are made using the First Law of Thermodynamics to assess the efficacy of the system from the thermal point of view.

It is concluded that with the advent of increasing energy dissipation, as a consequence of increase in tunnel usage, thermally efficient and cost-effective cooling systems must be developed if temperatures are to be maintained at acceptable levels.
Application of Observers to Monitoring, Failure Detection and Fault Diagnosis in Aircraft Flight Control
Authors: Vepa R , Caliskan F
Published: February 2007

In this paper the application of observers to monitoring, failure detection and fault diagnosis in aircraft flight control systems is discussed in detail. New results concerning the design of parameter-insensitive observers are presented. The feasibility of real-time implementation of a monitoring and failure detection and diagnosis scheme on multiple transputers is investigated and it is shown that the real-time performance specifications can be met and that the method could be used in practice.
Role of Material Properties in the Finite Element Solution for Three-Dimensional Composites—A Sensitivity Study
Authors: Hellweg H-B , Crisfield M A
Published: February 2007

Three-dimensional material test data for orthotropic laminae are difficult to obtain. Consequently, various simplifications are made for the material properties of individual layers in a finite element analysis, ranging from the assumption of transversely isotropic layers to applying two-dimensional material data in a three-dimensional analysis. In order to investigate the impact and validity of such simplifications, the sensitivity of the stresses and deformations in a finite element analysis on the material properties was investigated.
Benefits of Operational Load Monitoring in Civil Transport Aircraft
Authors: Horst P C T
Published: February 2007

One possible approach for the determination of new maintenance inspection schedules in the case of operational load monitoring is presented. Emphasis is laid on fatigue critical structural items. The method is based on the assumption that required safety factors may be reduced, if the actual load history is known from individual monitoring. As an example the method has been applied to an existing widebody aircraft type.
The Probabilistic Approach to Safety—Success Or Failure?
Authors: Cherry R G W
Published: February 2007

Numerical probabilities have been used as an aid to aircraft systems design and safety analysis for some thirty years. This paper considers the background to the philosophy, its current application and the benefits that might be gained from further developments. The approach is also put into the context of other opportunities that might exist for seeking further enhancements to aircraft safety.
Optimization of Tractor Propeller/Wing Configurations
Authors: Veldhuis L L M
Published: February 2007

In this paper, a rapid, approximate calculation method for optimal lift distributions of tractor propeller/wing configurations will be formulated and discussed. Some numerical studies, performed with a computer program containing the coded method, reveal that substantial performance benefits can be obtained by adapting the wing geometry and twist distribution to generate optimum lift distribution. The example calculations show that the lift distribution for minimum induced drag differs significantly from the elliptic loading.

Furthermore, the propeller angle of attack seems to have a dominant influence on the wing performance. Mounting the propeller at a negative (tilt down) angle with reference to the wing suggests a strong reduction of overall wing induced drag. Moreover, the wing efficiency is found to be strongly dependent on the spanwise propeller position. To produce realistic lift distributions the effect of profile drag is incorporated in the model.

Experimental verification of the presented theory using data from simple propeller/wing windtunnel models proves the validity of the method for preliminary design purposes.
Application of H∞ Control and Lqg with Frequency-Dependent Weight Syntheses to a Multivariable Active Flutter Suppression System
Authors: Fujimori A , Nikiforuk P N
Published: February 2007

This paper describes the effectiveness of three robust control synthesis techniques applied to a multivariable active flutter suppression system using numerical simulations. These techniques are the mixed-sensitivity reduction in H∞ (H∞-mix), the normalized left coprime factorization robust stabilization in H∞ (H∞-normalized), and LQG with frequency-dependent weights (FWLQG), which are proposed in this paper. Although the plant is an unstable multi-input and multi-output system with large parameter variation, the FWLQG technique is superior to both H∞ synthesis techniques from the viewpoint of the increment of the flutter velocity, the time response and the solubility of control problems.
Considerations of the All Electric (Accessory) Engine Concept
Authors: Jones R I
Published: February 2007

The concept of the all electric (accessory) engine (AEE) involves the use of an electrical machine integrated on an engine main shaft acting as a starter generator, providing power to both engine and airframe systems.

Through removal of the various constraints caused by the present mechanical accessory drives, this concept apparently provides a number of advantages. However, the concept of an AEE has been around for some years and yet has not been adopted to-date.

A brief review of electrical machine types previously considered as internally mounted starter/generators highlights basic problems of the concept. The reasons for favouring the Switched Reluctance Machine for this application are then explained and some present and planned developments on this basis outlined.

An approximate sizing of starter/generators to replace shaft off-takes alone and bleed in additions in a civil turbofan application is presented, showing more detailed design considerations. Other system component aspects and concerns are also covered before addressing the effects on the ease of adopting the AEE concept of likely future changes to civil engines.

Major differences relative to the civil case are indicated for other engine type applications. Conclusions are then drawn on the likely future of the AEE concept.