bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of Coulomb and Viscous Friction in Robot Drives: An Experimental Comparison of Methods
Authors: Elhami M R , Brookfield D J
Published: February 2007

This paper presents an experimental comparison of five methods of identifying friction in robot drives. The methods considered are direct plotting of velocity versus armature voltage, plotting velocity versus armature current, third harmonic estimation, batch least squares and sequential least squares. These methods were implemented on a d.c. servo motor robot drive system to identify Coulomb and viscous friction parameters. It is shown that an asymmetric Coulomb and viscous model properly identifies the frictional torque due to the combined sliding and rolling friction in the motor. Furthermore, although each of the identification methods is shown to be capable of giving reasonable estimates of the frictional coefficients, the plotting of velocity versus armature current is shown to be most suitable for off-line frictional identification and the sequential least-squares method most suitable for on-line identification, particularly when coefficients may change with time.
A Non-Linear Aeroelasticity Analysis of a Fan Blade Using Unstructured Dynamic Meshes
Authors: Vahdati M , Imregun M
Published: February 2007

The main objective of this paper is to present a methodology for the three-dimensional aeroelasticity analysis of turbomachinery blades using an unstructured compressible Navier-Stokes solver for the fluid and a modal model for the structure. The basic fluid solver is constructed in the form of a central difference scheme with explicitly added artificial dissipation which is based upon the fourth- and second-order differences of the solution. The temporal discretization uses an implicit time integration scheme based on a Jacobi relaxation procedure. The structural modes of vibration are determined via a finite element model and the mode shapes are interpolated on to the fluid mesh in a manner that is consistent with general unstructured tetrahedral grids. A spring analogy algorithm that can move the mesh according to the instantaneous shape of a deforming blade has been developed for the accurate tracking of the solid boundaries without creating excessive grid distortions. The performance of the resulting system was examined by considering the aeroelastic behaviour of NASA Rotor 67 fan blade and predictions were compared to experimental results wherever possible. Using a three-dimensional cyclic symmetry model, the tip leading edge time histories were predicted under peak-efficiency and near-stall conditions, and the corresponding aeroelastic natural frequencies and aerodynamic damping values were determined. The blade was found to be stable in all cases considered.
Dynamic Simulation of Road Vehicle Performance Under Transient Accelerating Conditions
Authors: Hong C-W
Published: February 2007

A personal computer-based simulation package has been developed to design the powertrain system of passenger cars aiming to operate at optimal performance. This package is capable of dynamic simulation of road vehicle performance under transient accelerating conditions. Two methods are included: one is the traditional transient-reconstruction method using steady-state engine performance maps; the other is a dynamic simulation technique newly developed by the author. The latter is described in this paper. It is based on cyclic analysis of the engine thermofluid-combustion phenomena with additional considerations of flow inertia, thermal inertia and mechanical inertia effects. This transient engine model plus a dynamic powertrain model and a transient road-load simulation make it possible to predict the automobile performance under road-driving conditions.

Two examples of transient performance prediction, including a sudden full-throttle acceleration at a fixed gear and a changing-gear starting acceleration from standstill, are demonstrated in this paper. These examples show that the relation between the engine speed and the road speed under accelerating conditions is very different to the steady-state relationships normally assumed.
Noise and Vibration Analysis of an S-Cam Drum Brake
Authors: Day A J , Kim S Y
Published: February 2007

Modal analyses of an S-cam drum brake assembly, using finite element analysis, are presented. A friction interface contact pressure-dependent model for the coupling between the lined brake shoe assembly and the brake drum is described. Using this model, natural modes and frequencies are predicted which compare well with measured data for the brake assembly. A parametric study of brake design and performance variables is presented which predicts the noise propensity of the brake design based on the binary flutter model. Good agreement with measured brake noise and trends, experience and other published work on S-cam brake noise is shown.
The Magnitude of The Losses in the Steel Pushing V-Belt Continuously Variable Transmission
Authors: Micklem J D , Longmore D K , Burrows C R
Published: February 2007

This paper investigates the reasons why in current passenger vehicles the steel pushing V-belt continuously variable transmission (CVT) has failed to achieve an improvement in fuel economy even though the CVT is correctly controlled and allows the engine to operate near to its region of maximum efficiency. It is shown that the overall efficiency of the transmission is low, especially at the lower vehicle speeds.

The main losses are due to the belt torque loss, the hydraulic pump loss and the loss due to slip in the belt-pulley system. It is shown that a considerable improvement in vehicle economy is obtainable by controlling the transmission so that the sum of these losses is minimized as well as seeking to optimize the engine efficiency. This improved overall efficiency is achieved by operating the CVT with much lower pulley clamping pressures than have previously been considered desirable.
Vehicle Dynamics—Theory into Practice
Authors: Crolla D A
Published: February 2007

The paper reviews the contributions of vehicle dynamics theory to practical vehicle design. In particular, it focuses on actively controlled components, for example active suspension, four wheel steering, and their impact on vehicle performance and safety.
Aldehydes and Ketones in Engine Exhaust Emissions—a Review
Authors: Wagner T , Wyszyński M L
Published: February 2007

Aldehydes and ketones in engine exhaust gases are receiving increased attention and are beginning to be subject to special legislation due to their carcinogenic and ozone formation potential. This paper gives an overview of their properties as well as of the basic chemistry and conditions of their formation in internal combustion engines. Extensive research on the effects of engine operation and fuelling parameters is reviewed with specific references to gasoline, diesel, natural gas and methanol fuelled engines. This is accompanied by the review of the studies of the performance of exhaust catalytic converters with respect to aldehydes. Aldehyde detection and measurement methods are summarized and analysed from the point of view of their applicability to exhaust gas analysis.
Spatial Repeatability of Measured Dynamic Tyre Forces
Authors: Cole D J , Collop A C , Potter T E C , Cebon D
Published: February 2007

The dynamic tyre forces generated by heavy goods vehicles are measured with a portable load measuring mat and used to investigate ‘spatial repeatability’. The mat is 56 m long, 13 mm thick and has 141 capacitative strip sensors, spaced at 0.4 m intervals. Two sets of experiments are described. In the phase 1 experiments the measured dynamic tyre forces generated by fourteen articulated vehicle combinations (three tractors and five trailers) are used to confirm previous theoretical predictions of spatial repeatability. In the phase 2 experiments the dynamic tyre forces generated by over 1500 heavy goods vehicles travelling on a British trunk road are used to estimate the degree of repeatability exhibited by a typical highway fleet.

Spatial repeatability is assessed using the ‘spatial repeatability index’ (SRI), and a method is developed to correct the SRI for sensor noise. Approximately half the vehicles tested were found to contribute to a spatially repeatable pattern of road loading.
Effect of Top Land Width and Engine Operating Conditions on Exhaust Hydrocarbon Emissions from a Spark Ignition Engine
Authors: Huang Z H , Pan K Y , Zhou L B , Jiang D M
Published: February 2007

In this paper, the formation mechanisms of unburnt hydrocarbons in the cylinder of a spark ignition engine are investigated and the effects of various top land crevice widths, engine speeds, air–fuel ratios and spark advance angles on engine exhaust hydrocarbons are investigated. The effects of engine top land crevice width on power output and fuel economy are also analysed. It is shown that the optimum engine top land crevice width is 0.32 mm (1.3 times the two surface quench distances), thus the flame can get into the bottom of the crevice and burns out all of the accumulated unburnt hydrocarbons in it, consequently the engine exhaust hydrocarbons can be greatly reduced by 35–50 per cent with less penalty on engine power output and fuel economy (0.5–1.5 per cent loss in power output and 1 ∼ 3 per cent increase in fuel economy).
An Exhaust Emissions Based Air–Fuel Ratio Calculation for Internal Combustion Engines
Authors: Chan S H
Published: February 2007

This paper describes a method for accurate determination of air–fuel ratio based upon exhaust gas emissions analysis as an alternative to the conventional direct air and fuel flowrates measurement. A thorough analysis of all the possible parameters that may affect the accuracy of air–fuel ratio is conducted which includes the instrument error, ambient conditions, the assumed water–gas shift reaction constant, the humidity of the atmospheric air and the inclusion of oxides of nitrogen in the air–fuel ratio model. Results show that four essential exhaust gas emission concentrations, namely carbon dioxide, carbon monoxide, oxygen and hydrocarbons, are adequate for obtaining an accurate air–fuel ratio provided that the fuel type and the range of parameters that may affect the accuracy of air–fuel ratio are properly defined.
Flow in Automotive Alternators
Authors: Brungart T A , Meyer G A , Lauchle G C
Published: February 2007

A study of the flow field in and around an automotive alternator is described. The approach taken is to test the alternator in water at equivalent in-air Reynolds numbers in order to reduce the rotational velocity by a factor of approximately 15 and provide an environment ideal for flow visualization. The casing and stator were constructed from clear plastic in order to provide visual access inside the alternator. Dye injection flow visualization is used to assess qualitatively the global flow field. Laser Doppler velocimetry is used to perform a detailed, quantitative study of the alternator external flow field. Results from the flow field study are presented and modifications necessary for improved cooling and aerodynamic performance are identified and demonstrated.
Diesel Injector Dynamic Modelling and Estimation of Injection Parameters from Impact Response Part 2: Prediction of Injection Parameters from Monitored Vibration
Authors: Gu F , Ball A D , Rao K K
Published: February 2007

Part 2 of this paper presents the experimental and analytical procedures used in the estimation of injection parameters from monitored vibration. The mechanical and flow-induced sources of vibration in a fuel injector are detailed and the features of the resulting vibration response of the injector body are discussed. Experimental engine test and data acquisition procedures are described, and the use of an out-of-the-engine test facility to confirm injection dependent vibration response is outlined.

Wigner–Ville distribution (WVD) analysis of non-stationary vibration signals monitored on the injector body is used to locate regions of vibration in the time–frequency plane which are responsive to injection parameters. From the data in these regions, estimates of injection timing and fuel pressure are obtained.

Accurate estimation of injection parameters from externally monitored vibration is shown to pave the way for the detection and diagnosis of injection system faults. Moreover, it is demonstrated that the technique provides an alternative method for the set-up, checking and adjustment of fuel injection timing.
A Model for Automotive Windshield Washer Spray Delivered by a Fluidic Nozzle
Authors: Ghannam M , Schumack M
Published: February 2007

Locating the spray nozzle to provide optimum coverage of the windshield under a wide range of driving conditions is largely a trial-and-error experimental process for the designer. In this paper a computational model is presented that will initially locate the nozzle and thus reduce wind-tunnel and/or road test time. The computer program is easy to use and the calculation time is short on a 486 PC. Comparisons between model and experiment are presented which show that the model generally predicts the experimental strike point to within 13 per cent. Parametric studies show the effects of spray velocity, car speed, fluid density, droplet size and nozzle location.
Four Wheel Steering System for Vehicle Handling Improvement: A Robust Model Reference Control Using the Sliding Mode
Authors: Ro P I , Kim H
Published: February 2007

In this paper a MIMO model reference control scheme incorporating the sliding mode control theory for a vehicle four wheel steering system is proposed and evaluated for a class of continuous-time non-linear dynamics with uncertainties. By the Lyapunov direct method, the algorithm is proven to be globally stable, with tracking errors converging to the neighbourhood of zero. The sliding mode four wheel steering (SM4WS) not only improves the directional stability and responsiveness but also provides good disturbance rejection for unexpected side wind. The SM4WS results in a faster vehicle response than conventional two wheel steering (2WS) without suspension and tyre modification. The linear three degree-of-freedom vehicle handling model is used to investigate vehicle handling performances. In simulation of the J-turn, the yaw rate overshoot reduction of a typical mid-size car improved by 30 per cent compared to a 2WS case. Although the lateral deviation of SM4WS is almost the same as that of 2WS the yaw rate reduction was approximately 20 per cent of that of a 2WS system. The simulation of the J-turn manoeuvre shows that the proposed scheme gives faster yaw rate response and smaller slide-slip angle than the 2WS case. When the rear tyre pressure is lower than normal, the car has less understeer and is worse in directional responsiveness, while SM4WS is insensitive to such parameter variations because of the robustness characteristics of the sliding mode control.
Flow Area of Multiple Poppet Valves
Authors: Woods W A , Brown P G
Published: February 2007

The importance of valve flow area is highlighted and the advantages of the four valve cylinder head mentioned. A simple method of making a preliminary assessment of multi-valve schemes, based upon relative effective flow areas, is outlined. The method is demonstrated with reference to eight and less valves for odd and even numbers. The 37 per cent increase in valve area for the four valve case is demonstrated and the promising possibilities for the three, five and seven valve heads are presented.
Burst Pressures of Pipes Containing Dents and Gouges
Authors: Lancaster E R , Palmer S C
Published: February 2007

Mechanical damage to pipelines may take the form of dents and gouges, which may also incorporate cracks. The combination of a gouge within a dent has long been recognized as the most severe form of damage, and can result in failure at very low internal pressures. Yet despite much expensive full-scale testing, predictions of subsequent burst pressures of such damaged pipes are unreliable, and assessment procedures are very conservative.

This paper describes a series of burst tests on model aluminium pipes containing dents and smooth gouges, specifically excluding cracks. The results show that gouges located near the axial extremity of a dent cause low-pressure failure, and indicate the presence of two regions of high strain at the axial extremities of the initial dent. For gouges in other areas of the dent, the Battelle flow stress dependent model for ductile failure of plain gouges in undented pipes is shown to give reasonable predictions of burst pressures, which are independent of the dent depth. In all of the pipes tested, failure was ductile, and this is attributable to the absence of cracks. Pipes withstood pressures in excess of the corresponding normal operating pressures, except where gouges were located near the axial extremity of the dent. The results throw much light on the published results from tests on full-size steel pipes, and support earlier hypotheses that removal of cracks from a damaged pipe by light grinding may significantly increase the pipe burst pressure.
Strain Concentrations in Pressurized Dented Pipes
Authors: Lancaster E R , Palmer S C
Published: February 2007

Knowledge of the strain distribution in a dent is crucial in assessing the severity of damage to pipes. Accordingly this paper presents the results of a series of tests to measure strains and displacements in previously dented aluminium pipes subject to increasing internal pressure. Indentation of unpressurized and pressurized pipes was caused by a rigid sphere and resulted in short smooth dents of depths up to 16 per cent of pipe diameter. Strain changes on the external pipe surface were monitored by strain gauges and a photoelastic coating. The results identify two stationary crescent-shaped regions of high external strain at the axial extremities of the initial dent, where strain concentration factors of 10 were recorded in the early (elastic) stages of pressurization, increasing to a maximum of 28 in one particular dent.

The results have immediate application to the assessment of a gouge within a dent, which has long been recognized as the most severe form of mechanical damage to pipelines and can result in failures at very low internal pressures. A parallel series of burst tests by the authors revealed that gouges located near the axial extremities of the initial dent may cause premature failure. The strain concentration results presented here help to explain this behaviour, and indicate the size, shape and location of the regions of high external strain.
Automatic Detection of Defects on Birch Wood Boards
Authors: Pham D T , Alcock R J
Published: February 2007

In a factory which produces veneer boards from birch wood, grading of the boards into different quality categories is usually part of the production process. To improve the efficiency of grading, attempts are being made to automate it using automated visual inspection (AVI). Integral to the process of inspection is segmentation. Segmentation is the part of the AVI process concerned with separating clear wood and defective areas in the image. This paper describes a system that is used to segment the images of birch wood boards. The system consists of four modules which are called global adaptive thresholding, multi-level thresholding, row-by-row adaptive thresholding and vertical profiling. The paper gives details of the four modules and presents the results obtained in segmenting images of a large sample of birch wood boards.
Experimental and Theoretical Observations of the Dynamics of Paper in a Printing Press Folder
Authors: Harrison A J , McMahon C A
Published: February 2007

The jaw folder is widely used in the printing and paper converting industry, having the purpose of placing a fold in a sheet or sheets of paper in a direction perpendicular to their direction of motion. The dynamics of the sheet are complex, involving the rapid reversal of motion of half of the sheet, and are not presently well understood. Through analysis of high-speed cine films of a typical jaw folder, the authors have quantified the positions and accelerations of the sheet during the folding process. These have been verified by software simulation. The surrounding air is shown to be of great significance to the effective sheet mass and the damping of its motion. Accelerations in the plane of the sheet are also demonstrated to be important contributors to its stiffness. Methods are suggested by which the design of the folder might be improved.
Analysis of the Mechanics for Drawing Polyvinyl Chloride Tubes over an Expanding Mandrel
Authors: Kakadjian S , Craggs G , Ward I M
Published: February 2007

An analysis is presented of the mandrel drawing process in which a tubular polyvinyl chloride (PVC) billet is drawn over an expanding mandrel so as to achieve a tubular product having a high degree of molecular orientation in the hoop and axial directions and enhanced mechanical properties. The stress and deformation behaviour of material moving over the mandrel are determined from equilibrium considerations and modelling of the material using the Ogden representation.

Experimental results from drawing tests carried out on a large-scale test facility are presented and the effects of mandrel semi-angle, mandrel exit diameter and processing temperature on drawing behaviour are evaluated. Good agreement is shown between the experimental results and theoretical predictions of final product thickness, die exit stress and drawing load.
Plastic Limit Pressures for Neighbouring Radial Nozzles in a Spherical Pressure Vessel
Authors: Naderan-Tahan K , Robinson M
Published: February 2007

Limit pressures have been calculated for the case of two identical flush neighbouring radial nozzles in a spherical pressure vessel. The nozzle and vessel radius and thickness have been kept fixed, but the separation angle 2α has been varied. Four cases have been analysed, including that where the nozzles touch, and the results compared to the value for a single nozzle. For these nozzles very little decrease occurred for any of the α. The effect of displacement on pressure carrying capacity was also investigated and shown to be beneficial, so that limit pressure results may be used with confidence.
Data Management and Document Control
Authors: Abbas S Ahmed
Published: February 2007

The Information Management Committee of the Process Industries Division of the Institution of Mechanical Engineers organized two seminars on the subject of ‘Data management and document control’ during 1995. The first was held in London on 28 March, attracting about 70 delegates. Its popularity prompted the Committee to organize a modified repeat in the Teeside area, with its high concentration of process industries, on 28 September, and this was attended by over 50 delegates from a variety of sectors including oil and gas, chemicals, pharmaceuticals, power generation, water and food.
Hydrodynamic Modelling of Sedimentation Tanks
Authors: Quarini G , Innes H , Smith M , Wise D
Published: February 2007

Sedimentation is one of the principal processes used in the water industry to treat domestic and industrial effluents. In this paper the hydrodynamic characteristics of a standard circular sedimentation tank have been studied using a one-twentieth scale physical model and computational fluid dynamics (CFD). The experimental data have been compared with the numerical CFD predictions; good agreement has been obtained, especially in areas of high flow velocity. The physical and numerical models have been used to study the effects of tank configuration on its hydraulic performance.
Pressures in a Square Planform Silo during Discharge
Authors: Brown C J , Jarrett N D , Moore D B
Published: February 2007

This paper presents data obtained from a series of tests on a steel square planform funnel flow silo with concentric discharge. For the silo in a discharging condition, results are presented from wall pressure cells. Key results for the loading cycle are given for comparison. An analysis shows the accuracy and reliability of the data obtained. The wall pressure measurements show the increase in wall pressure as a result of discharge conditions. Explanation of the phenomena and an indication of their design relevance is given.
Analysis of a Cylindrical Shell Supported by Two Longitudinal Beams
Authors: Ong L S , Tooth A S
Published: February 2007

A shell analysis model has been developed to determine the stress and strain developed in cylindrical vessels supported by two longitudinal beams which extend the full length of the cylinder. A contact stress approach has been formulated to find the interface reaction pressures between the cylinder and the beam supports and a cylindrical shell theory has been used to obtain the stress and displacement in the shell. A comparison has been made between the present theory and a set of published experimental and finite element results. Good agreement has been found between them. The maximum strain in the beam-supported cylindrical vessel has been found to occur at the mid-span of the vessel in the vicinity of the beam support. A parametric study shows that the most efficient way of supporting the vessel is to locate the beam support at the equator of the shell. With this support arrangement the peak strain in the shell is the lowest compared with other cases. Lastly, a simple ring theory has been proposed and derived which provides quick and accurate results for the peak strain and strain distribution.
A New Model for Design Processes
Authors: Acar B S
Published: February 2007

A number of models have been suggested in the past to understand the design procedures. Improvements in one model over another one usually fills a gap in modelling; however, like the design procedure itself, modelling has a dynamic nature and it constantly needs to be updated according to the needs and requirements of time. This paper will concentrate on modelling today's design procedures and interrelations. A new model to provide a global view to understand the design procedures will be proposed and explained. It is believed that this may help to open the avenues for the production of new tools for designers and design teaching in the future.
Developments in Warship Design and Engineering
Authors: Betts C V
Published: February 2007

Warships, together with their weapons and major sub-systems, take ten to fifteen years to design and build and then spend twenty-five years or more in service. The Royal Navy fleet of today was designed during the Cold War for conditions rather different from those now pertaining. Designs now on the drawing board (or, more correctly, on the computer screen) and the research and development required to underpin them are aimed at requirements where the enemy threat is uncertain, warfare technology proceeds apace and the need for maximum value for money in reduced defence budgets is paramount.

Developments in weapon systems and command, control and communication systems are impressive and far reaching. However, developments in surface warship and submarine naval architecture and marine engineering are potentially as important to the long-term effectiveness and affordability of the Fleet. This paper looks at the technologies being considered for future designs with emphasis on hull and marine engineering developments. These include novel hull forms such as the trimaran and possibly the next major step in surface warship propulsion—the all-electric ship with electric transmission and low fuel consumption gas turbines as prime movers for electricity generation. The paper also discusses the importance of ‘human factors’ in the design process, the increasing use of commercial standards to control costs of both hardware and software, and improvements in naval ship and submarine design tools for use in the crucial concept design phase.
On the Prediction of Stresses in Pipes Caused by Ice Plug Formation
Authors: Syngellakis S , Keary A , Bowen R J
Published: February 2007

Stress development in pipes due to local fluid freezing is investigated through a simple analytical model based on thin axisymmetric shell theory. Particular attention is given to modelling the interaction between the pipe wall and the ice formed within the freezing jacket. The developed analysis accounts for the interface shear traction and relies on rational assumptions regarding its distribution in order to interpret and reproduce observed pipe behaviour. It is validated by comparing its predictions to available exact and numerical solutions as well as experimental data. Finally, it proves a valuable tool in understanding the ice plug-pipe wall interaction mechanism which controls stress generation and distribution.
A study of Turbulent Flow in Pipe Contractions
Authors: Bullen P R , Cheeseman D J , Hussain L A
Published: February 2007

An experimental study of turbulent water flow through abrupt contractions was carried out in order to determine the detailed flow field. Wall static pressure measurements enabled the calculation of pressure loss coefficients for a range of contraction area ratios from 0.13 to 0.67 over a Reynolds number range of 40000–200000. The effect of variations in contraction sharpness was also established. Measurements of mean velocities and turbulence intensities were made using a two-component laser Doppler anemometer for one area ratio of 0.332 to establish the detailed flow features.
Wheelset Guidance—Conicity, Wheel Wear and Safety
Authors: Pearce T G
Published: February 2007

This is a discussion of the profile features which govern the guidance of a wheelset, both on straight track and on curves. Starting from the choice of a new profile, the paper explores the effects of wear on both the conicity and the safety against derailment by flange climbing. Safety against derailment is then discussed further in relation to the discrete irregularities in rail profile that occur at switches and crossings.
Reliability considerations for Switched Mode Power Supplies for use in Railway Applications
Authors: Allen S J
Published: February 2007

The use of switched mode power supplies in trackside and railway applications is considered, with particular emphasis on the selection process for determining long-term high reliability.
Structure Gauging—Maximizing the Use of Restricted Clearance
Authors: Eickhoff B M , Scott G A
Published: February 2007

Structure gauging is the process for ensuring that a particular railway vehicle or train can pass safely along a particular route under all operating conditions without coming unacceptably close to lineside structures or vehicles on adjacent tracks. This paper reviews some of the background to the development of the gauging methods in use at present, identifies areas where attention is likely to be concentrated in the near future and considers possible longer term developments. The paper concentrates on the methods developed and used within the UK but does also consider other methods such as those in use by other UIC railways.
The Dynamic Response of Railway Ballast to the Action of Trains Moving at Different Speeds
Authors: Luo Y , Yin H , Hua C
Published: February 2007

To study the dynamic response of railway ballast excited by forces from the moving train at different speeds, a finite element model of track is developed. The rail is represented by a Timoshenko beam on discrete pad-sleeper-ballast supports. The ballast is considered as a three-dimensional finite element model. Wheel/rail irregularities and moving loads are taken into account. The displacement, acceleration and dynamic stress at different parts of the ballast are calculated. Vibration propagation is also presented. The responses of ballast, for constant loads and travelling at constant speeds over track with and without irregularity, are studied. It is shown that, at high speeds, stone may be projected out of the ballast bed.
Passive and Semi-Active Airspring Suspensions for Rail Passenger Vehicles—Theory and Practice
Authors: Tang J S
Published: February 2007

The performance of passive and semi-active secondary airspring suspension systems on rail passenger vehicles has been studied theoretically and experimentally. Classical and modern optimal control theory was utilized in the studies. The concept of the semi-active damper was realized in a laboratory test by a butterfly valve, for which a practical position control logic was developed. The quarter vehicle test rig results have shown that by making the orifice damper variable, a 29 per cent ride improvement has been achieved. For the full vehicle computer simulation, a ride improvement of 20 per cent has been achieved. In addition, for both cases, the dynamic suspension working space has been reduced by 10 per cent.
The Interlaminar Fracture Behaviour of Carbon Fibre Reinforced Plastics at Low Temperatures
Authors: Cantwell W J
Published: February 2007

The low-temperature fracture properties of a carbon fibre reinforced epoxy composite have been investigated by conducting a series of mode I, mode II, interlaminar shear strength (ILSS) and drop-weight impact tests at temperatures between — 194 and 23 °C. Initial tests on the pure epoxy indicated that the mode I fracture toughness of the pure resin increased steadily with reducing temperature. Similar trends were observed in the ILSS and mode II data where increases of up to 100 per cent were observed over the range of temperatures examined. No appreciable temperature dependence was observed, however, in either the mode 1 fracture data or the overall impact damage area.
Active Cooling of a Hypersonic Plane Using Hydrogen, Methane, Oxygen and Fluorine
Authors: Al-Garni A Z , Şahin A Z , Yilbas B S
Published: February 2007

This paper studies active cooling of an aerospace plane using liquid hydrogen, liquid methane, liquid oxygen and liquid fluorine. An ascending optimized trajectory to minimize the heat load in the hypersonic part is used to perform the study, which includes cooling of the stagnation point, the leading edges of wings and engine and other parts of the aerospace plane that are close to the leading edges. The laminar case of the stagnation point and both laminar and turbulent cases for the leading edge heating have been considered. The amount of liquid coolant mass needed for cooling is calculated. A design of minimum inlet–outlet areas for the amount of liquid needed for cooling is made with consideration of the coolant's physical constraints in the liquid and gaseous states. The study shows that the ratio of masses of coolant to the initial total mass (initial total mass of the vehicle including fuel and coolant masses) is in the limit of the reachable range. The comparison shows that the hydrogen is a clear winner as a candidate for coolant and saves mass as compared to the other three coolants. The study shows that there are no fundamental barriers for the cooling system of the vehicle in terms of its coolant mass and area size for coolant passage.
Civil Airframe Structural Integrity—Some Probabilistic Aspects of Risk Assessment
Authors: Jones M R
Published: February 2007

Fatigue is the mechanism of progressive damage which may ultimately limit the economic life of an airframe. However, there is an intrinsic variability in the life of nominally identical structures subjected to alternating loads. Currently, the uncertainty in the estimated fatigue lives is accounted for in design by applying ‘scatter factors’ to the results of full-scale fatigue tests or to deterministically calculated lives. An alternative approach is to perform a reliability analysis to ensure that the weaker members of an aircraft fleet will meet the design aims with a pre-defined level of reliability. This paper aims to develop and apply analytical models required to:

determine the safe-life or inspection threshold for a given fleet size with a prescribed reliability and review and revise the inspection programme based on the results of in-service inspections.
The Vibration of an Aero-Engine Rotor Incorporating Two Squeeze-Film Dampers
Authors: Holmes R , Sykes J E H
Published: February 2007

Virtually all previous research on the squeeze-film damping of rotor assemblies has considered the use of only one damper. However, many aero-engine rotor assemblies have at least two dampers and the interplay between them is an important factor in the overall vibration performance of the rotor. The purpose of this paper is to report results on a test facility which simulates the rotor of an aero-engine of the size used to power an executive jet. It draws general conclusions on the application of two squeeze-film dampers (SFDs) to such a rotor, while in the process qualitatively validating a suggested theoretical model of the SFD. The test facility is a three bearing rigid rotor assembly incorporating two sprung bearing supports, each in series with a weakly sealed squeeze-film damper. A range of practical configurations with different SFD static misalignments is studied. Non-linear jump phenomena and subharmonic resonances are demonstrated both experimentally and theoretically for a range of rotor unbalance. The paper is concerned with predicting and measuring rotor-centre responses and vibration orbits and drawing conclusions that are relevant to the designer. It forms a complement to a previous paper (1) in which spectrum analyses of vibration signatures were made.
Maintaining Mature Military Air Transport Aircraft
Authors: Skinner G
Published: February 2007

Military air transport aircraft and those airliners converted to air-to-air refuelling roles present special technical challenges to sustain airworthiness as they mature in-service. In this paper a senior Royal Air Force engineer describes the procedures employed to safeguard structural integrity and other ageing transport aircraft problems in general; and in particular, uses the VC10 as a case study to illustrate the development of techniques such as regular proof pressure testing and acoustic emission monitoring of the fuselage as part of a range of activities in the maintenance of this mature type of aircraft. The effects of ageing on the lifecycle of these aircraft types is also considered.
The Prediction of Aircraft Wing Mass
Authors: Howe D
Published: February 2007

The need for mass prediction methods and the problems associated with them are discussed. Two methods for wing mass prediction are then presented, one based on an analysis of empirical data and the other having a theoretical basis. The two methods have been tested against a substantial number of actual wing masses covering all types of aircraft. Overall the results are acceptable although there are some, specific, discrepancies. While the empirical method is easier to use and actually shows less scatter, the theoretically based method does enable particular features of the wing design to be allowed for and gives somewhat better correlation with actual wing masses.
Impact of Second Generation Single Crystal Superalloys on Foundry Technology
Authors: Ford D A
Published: February 2007

Superalloys developed after the Second World War to meet the demands of the jet engine reached the limit of known alloying in the late 1960s. The continuing requirement for materials with higher temperature capabilities was met by developments in solidification and processing technologies leading to directional solidification and single crystals.

By the mid 1980s it was apparent that further improvements in material temperature capability could be achieved by alloying with such exotic elements as rhenium and yttrium. The success of these alloys is due to the retarding of diffusion rates and greatly increased oxidation resistance at high temperatures.

Superalloys containing these elements are generally known as second generation materials and are by virtue of their unique advantages very difficult to process. In particular the slow diffusion rates give significant difficulties with heat treatment and the retention of yttrium presents a foundry challenge of the highest order.

This paper will review the advantages of second generation material and address the process problems associated with their successful introduction into service.
Overview of Data Buses Commonly Used in the Aircraft Industry
Authors: Reynolds A P
Published: February 2007

This paper begins by reviewing the essential features of data bus concepts and continues by describing the key features of the most commonly used data buses on aircraft today. The following data buses are covered: ARINC 429; ARINC 629; MIL-STD-1553B; MIL-STD-1773; and STANAG 3910. The paper is intended to refresh and update those engineers not dealing with data buses, or the associated technology on a day-to-day basis.
Stresses in a Splineless Drive for Aero-Engines
Authors: Fessler H , Moore C J
Published: February 2007

This paper describes an alternative to splines for connecting turbine discs to shafts. The trilobe shape consists of six smoothly blending 60° circular arcs of two alternating radii; it is between a circle (both radii equal) and a triangle (smaller radius zero, larger radius infinite). Frozen-stress, photoelastic models of a realistic disc and a tubular shaft have been designed, made and loaded centrifugally, under static torsion and under combined torsion and rotation.

The results show that the greatest centrifugal stresses in the disc occur in the bore at the tips of the trilobe and the greatest contact stresses occur near the transition from the larger to the smaller radius. The centrifugal stress concentrations due to the trilobe were small. Bore deformation and backlash due to differential centrifugal expansion were measured and found to be acceptable for a similar ceramic or nickel alloy disc.
The Qualification of Safety Critical Structures by Finite Element Analytical Methods
Authors: Morris A J
Published: February 2007

The paper introduces the concept of certifying or qualifying structures in a safety critical situation using the finite element method. Error control and error treatment methods for this purpose are discussed together with the associated role of testing. The underlying methodology follows the principles laid down in the SAFESA (SAFE Structural Analysis) method which is described in outline.
Dynamical Behaviour of Cryogenic Helium in a Partially Filled Dewar in Microgravity
Authors: Hung R J , Pan H L
Published: February 2007

The temporal evolution of a spherically shaped bubble sitting to one side of a dewar at rest initially, and subsequently spun up to a constant angular velocity, is investigated. The time-dependent deformation of the bubble, which starts to elongate from a spherical shape, to wrap around the inner dewar wall, and finally to complete encirclement of the dewar wall, is numerically studied and simulated. Some similarity parameters are considered to study the bubble wrapping around the dewar wall. Examples are given to illustrate this problem which is important in the understanding of how surface tension, rotation speed, fluid density, contact angle, etc. affect the bubble deformation for the case of cryogenic helium II in a microgravity environment.
Model Reference Control of a Gas Turbine Engine
Authors: Perez R A
Published: February 2007

A simple control law is developed that guarantees that the outputs of a linear time invariant plant with feedthrough elements will converge asymptotically to a pre-specified set of desired trajectories. This control law is illustrated on a gas turbine engine to demonstrate its applicability to higher dimensional problems and to highlight the fast asymptotic convergence towards the desired trajectories. The algorithm presented here is fairly straightforward to implement, and should be a useful tool for model reference control. The desired model is implemented off-line, thus allowing for a potential real-time application. The only assumption made in this work is that the modes of the ‘actual’ plant are controllable. No assumptions are made or required on the ‘desired’ plant. The dynamic characteristics of both the ‘actual’ and the ‘desired’ plant can actually be quite different. The control law generates an input that forces the ‘actual’ outputs to follow the ‘desired’ trajectories.
Studies on Twin Non-Parallel Unventilated Axisymmetric Jets
Authors: Elangovan S , Solaiappan A , Rathakrishnan E
Published: February 2007

Twin non-parallel jet configurations occur in many practical devices like burners, combustion chambers, and also in the area of fluidics etc. Despite the importance of such configurations, studies on the interaction of twin non-parallel jets are very limited. The present work is an attempt to investigate the mixing of two axisymmetric jets obliquely oriented towards each other. Experimental studies were made on the interaction of twin intersecting axisymmetric jets issuing from two unventilated convergent nozzles. The nozzles of exit diameter (D) 10 mm were set on a common end wall with their axes intersecting each other at half angles (α3) of 0°, 5°, 10° and 15°. The centre-to-centre spacing (S) of the nozzles, non-dimensionalized, as S/D, was 3.1. The jet exit Mach number (Me) studied was 0.2. The results indicate that the near field characteristics are strongly influenced by α3. However, the potential core of the individual jets and the far field characteristics of the twin jet flow field, that is beyond downstream distances of 40 nozzle diameters, are not significantly influenced by α3. The cross-section of the jet just downstream of the combining point is approximately elliptic. The axis switching phenomenon normally associated with non-circular jets is observed in the jet flow field. The spread of the combined jet is more in the transverse direction than in the spanwise direction. Entrainment of the ambient fluid is found to be more in the case of twin parallel jets (α3 = 0°). The entrainment decreases with increasing α3. The self-preserving nature of the combined jet is almost independent of the initial geometric conditions. The combined jet is axisymmetric with regard to the normalized velocity and length scales.
The Design of a Small Satellite for Earth Observation
Authors: Gardner S J , Swinerd G G , Ward A K
Published: February 2007

The concept of the Teaching Company Scheme Satellite (TuCSAT), has been developed to meet the requirements of the Earth observation user community for inexpensive and flexible opportunities to launch remote sensing instruments into low earth orbit (LEO). This paper describes the satellite design process, together with the philosophy behind the selection of a baseline mission. The satellite is shown to demonstrate the ability to meet a wide range of requirements within a strict low mass and low cost philosophy, while making use of currently available technology in order to achieve the design aims.
Design Safety Analysis of Helicopter Rotor and Transmission Systems
Authors: Astridge D G
Published: February 2007

Design safety analysis (DSA) is an element of the certification process having the objective of determining whether the design can satisfy the required safety objectives. Analysis methods traditionally applied to aeroplane control systems include numerical procedures that are based upon the standard rules of probability theory. In this paper it is shown from a detailed examination of accident data that helicopter rotor and transmission systems do not confirm to this theory in respect of catastrophic failures. Practical solutions are offered for this problem, and for that posed by the lack of meaningful component failure data. Details are also given of procedures tailored to produce effective analysis of such systems, and for the structuring of failure modes, effects, and criticality analysis (FMECA) to improve their space efficiency by several orders of magnitude.