bluuebunny/crossref_metadata_2025 huggingface dataset:
A Better Than Average Stress Model—Photoelastic Analysis for Airbus Design
Authors: O'Brien E W
Published: February 2007

A high level of structural efficiency is required in order to help achieve competitive performance from modern commercial aircraft. Quality data is essential to confidently optimize complex structures with respect to stress, weight and cost. One response to the challenge has necessitated the development of improved analysis techniques involving photoelasticity as a design tool—‘a better than average stress model’ (unfortunately the phrase is not original).

Linear-elastic epoxy stress models can quickly determine precise stress levels and distributions of the required quality using reflective photoelasticity and may be supplemented by strain gauges.
Skeletal Accelerations Measured during Different Exercises
Authors: Woodward M I , Cunningham J L
Published: February 2007

Exercise is often suggested as a means of reducing the effects of osteoporosis in post-menopausal women. In response to an increase in physical activity, bone mass can be increased and several studies have investigated the effectiveness of different exercises in increasing bone mass. In this study we have attempted to quantify the effect of different exercises by measuring the accelerations produced during various exercises. Accelerations have been measured at the ankle of normal subjects during a series of impulsive (walking, running and walking up and down stairs) and non-impulsive (cycling) exercises. Accelerations were measured using an accelerometer attached to a stiff cuff which straps around the ankle. Signals from the accelerometer are amplified and recorded using a specially developed portable data-logging system. The principal parameters measured were the maximum change of acceleration (peak to peak) and the rate of change of acceleration. From the results it was observed that running and walking up and down stairs produced the highest peak-to-peak change (running = 8.08 g; walking downstairs = 8.11 g) and rate of change of acceleration (running = 2.14 g/s; walking downstairs = 2.07 g/s). By contrast, a non-impulsive exercise such as cycling produced relatively low values of peak-to-peak change (2.24 g) and rate of change (0.23 g/s) of acceleration.
Three-Dimensional Analysis of Knee Joint Movement with Biplanar Photography, with Special Reference to the Analysis of ‘dynamic’ Knee Instabilities
Authors: Matsumoto H , Seedhom B B
Published: February 2007

An apparatus was developed by means of which it was possible to move a cadaveric knee joint under a constant external force and to measure its movement in three dimensions using biplanar photography, to investigate mechanisms of ‘dynamic’ knee instabilities, such as the ‘pivot shift’ phenomenon. Two wire frameworks, one attached to the femur, the other to the tibia, defined a system of three mutually orthogonal axes. While the knee joint was moved under a given force, a series of biplanar photographs of the two frameworks were taken. This procedure was repeated after sectioning different ligaments simulating different injuries. The joint was finally fully disarticulated, but leaving the reference wire frameworks still attached to their respective bone. Another series of biplanar photographs of the femur and tibia were taken. From these two series of measurements, movements of the tibia with respect to the femur were calculated. With this two-step method, knee movements could be measured without damaging the knee structures before or during the actual measurement (which could change the knee movement itself). On validating the system, it was concluded that knee movement could be measured with sufficient accuracy for the analysis of knee instability.
Self-Service Banking and Mechatronics: The First Twenty Years
Authors: Dinsdale J , Hutcheon A J
Published: February 2007

The past two decades have seen a remarkable increase in the automation of banking operations and financial transactions. A comparative examination of modern automated teller machines (ATMs) and electronic banking systems alongside the mechanical machines in use less than half a century ago illustrates how this rapid introduction of advanced technology has been made possible through the interaction of mechanical engineering (especially mechanisms), electronic actuators and sensors, and computer software, an activity which has become known as ‘mechatronics’.
Control Chart Pattern Recognition Using Combinations of Multi-Layer Perceptrons and Learning-Vector-Quantization Neural Networks
Authors: Pham D T , Oztemel E
Published: February 2007

Pattern recognition systems made up of independent multi-layer perceptrons and learning-vector-quantization neural network modules have been developed for classifying control chart patterns. These composite pattern recognition systems have better classification capabilities than their individual modules. The paper describes the structures of these pattern recognition systems and the results obtained on using them.
Influence of an Accumulator on the Performance of a Hydrostatic Drive with Control of the Secondary Unit
Authors: Jen Y M , Lee C B
Published: February 2007

In a secondary control unit system, an accumulator changes the relationship of the pumps and motor from flow coupling to pressure coupling. This change creates several benefits, including energy conservation, increased stability and the ability to change the rotational direction of the hydraulic motor. The accumulator therefore plays an important role because it dominates the overall performance of the secondary control unit system. This paper studies the influence of accumulator volume and precharge gas pressure on the performance of a hydrostatic transmission system in a secondary unit control system. A small test rig of the secondary unit system was set up and a series of experimental studies were run. A mathematical model was derived for simulation purposes. The results reveal that making the volume of the accumulator and the precharge gas pressure as high as possible under permitted circumstances can decrease the fluctuation of working pressure, improve the dynamic performance of speed control and increase the recovery of energy.
On Minimum Boundary Image Maps
Authors: Ekanayake M M , Premaratne K
Published: February 2007

A Nyquist-like technique using boundary image maps for the assessment of stability of two-dimensional (2-D) digital control system models was first reported by De Carlo et al. in 1977. However, this method, although attractive in principle, is time-consuming and complicated. In a recent paper by Whalley and Zeng in 1992, a more efficient technique using minimum boundary image maps was reported. The technique, if correct, turns out to be even simpler than the tabular algorithms, which are probably the most convenient of all stability algorithms to program. However, with the use of two counter-examples it is shown that this method is not consistent with either De Carlo's theory or the modified Jury table (MJT) method. It is also shown that the new method does not guarantee stability even under conditions which are stronger than those proposed by Whalley and Zeng.
Self-Tuning Control of a Heating, Ventilating and Air-Conditioning System
Authors: Özsoy C
Published: February 2007

This paper describes the minimum-variance parameter-adaptive (self-tuning) control algorithms for SISO and MIMO systems. The algorithms are designed on the basis of linear input-output system models by the combination of recursive-parameter estimation and control algorithms: a single-variable minimum-variance self-tuning controller and a multi-variable minimum-variance self-tuning controller. These controllers are applied to a three-input three-output single environmental space, which consists of an air heater, air humidifier and ventilator, and whose output variables are temperature, relative humidity and air velocity. The results of simulation indicate that it is possible to use the self-tuning controllers to stabilize the controlled system after a short adaption phase and to achieve at least a satisfactory control performance for time-varying set-points of the output variables.
A Modelling Technique for Estimating Hot Tap Water Consumption in District Heating Systems
Authors: Jónsson G R , Holtsberg A , Jónsson V K
Published: February 2007

This paper is concerned with estimating the hot tap water consumption in district heating systems when direct measurements of the hot tap water are not available. Instead, only measurements of the total mass flow, that is the mass flow for both heating and hot water are assumed available. Thus, a method is needed that may be applied in order to separate the mass flow into these two parts, or even more if the mass flow is assumed to be consisting of more than two factors. Here, the mass flow is divided into one part dependent upon climate variables and one part that is independent of the climate. By assuming that the hot tap water consumption is to a high degree independent of the weather, the latter part is an estimate of the hot tap water. The data are from the Reykjavik Municipal District Heating System in Iceland. The results show that the hot tap water consumption has a noon and an evening peak and is at its minimum around 4 a.m. The average consumption is about 10 per cent of the yearly average mass flow. Furthermore, the consumption is highest during the winter time and lowest during the summer time. It was found sufficient to use one tap water profile on working days and one for weekends. It is shown that the solar effect on the mass flow is quite moderate. During working days it is about 1.2 per cent of the yearly average mass flow and 1.6 per cent during weekends (based on 10 hours of sunshine per day).
Branch Line Pipewhip Following Rupture at the Junction with the Main Pipe
Authors: Baum M R
Published: February 2007

There are many cases on power plant where large-diameter pipes containing high-pressure gas or steam have branch connections of a much smaller diameter. Frequently branch lines contain a closed valve. Here pipe rupture adjacent to the main pipe means that the section of pipe on the valve side of the break is subject to a transient thrust as the limited quantity of fluid between the closed valve and the open end is expelled. This section of pipe may also experience a force exerted by the impingement of the jet emerging from the main pipe. This paper considers the resulting pipewhip motion. The relative significance of the thrust resulting from the expulsion of the limited volume of fluid within the pipe and the subsequent jet impingement force are explored. In addition, the extent of the hazard zone and the peak kinetic energy of the pipe are determined.
Design and Performance of Vaneless Volutes for Radial Inflow Turbines: Part 2: Experimental Investigation of the Mean Line Performance—Assessment of Empirical Design Parameters
Authors: Whitfield A , MacGregor S A , Noor A B Mohd
Published: February 2007

The non-dimensional design procedure described in Part 1 assumed a one-dimensional compressible flow and as such relied on the empirical specification of the dissipation of angular momentum, the dissipation of energy and the deviation of the swirling flow from that of a free vortex. This was based largely on data available in the published literature. In order to develop and substantiate the empirical procedures further an experimental study was carried out in parallel with the development of the design procedure.

The experimental investigation described here had the specific objective of assessing and developing appropriate empirical models and coefficients for application to the design procedure. The study concentrated on the application of a five-hole probe located in the centre of the volute passage and at a series of azimuth angles around the discharge. The probe provided stagnation and static pressure measurements, from which the gas velocity was derived, together with the flow angle. When taking measurements at the volute discharge a stationary dummy rotor was used to carry the five-hole probe.
Performance Evaluation of Centrifugal Chillers in an Air-Conditioning Plant with The Building Automation System (BAS)
Authors: Ng K C , Bong T Y , Chua H T
Published: February 2007

A thermodynamic model with a novel method of describing the performances of centrifugal chillers for air-conditioning is presented. It is based on the first and second laws of thermodynamics which captures the overall entropy change due to non-isentropic compression and expansion of the thermodynamic cycle. The model gives the fundamental relation between the coefficient of performance (COP) and the cooling rates (Qe) for (a) the modulating and (b) the throttling actions of the inlet guide-vanes of the compressor. The usefulness and the accuracy of the model are demonstrated here by analysing the in situ performance of two commercial, installed centrifugal chillers of an air-conditioning plant as well as comparing the available performance data of another chiller in the literature.
Role of Dissipation Characteristics in Predicting Flow from Dissimilar Centrifugal Pumps
Authors: Bunt E A , Parsons B , Holtzhausen F
Published: February 2007

Examination of flows in a particular case of dissimilar pumps coupled in series or in parallel (without check valves) showed that the ‘classical’ graphical solution of combined characteristics in the [+H, +Q] quadrant did not accord with the output field in certain regions. To predict the full flow fields, it was necessary to take into account dissipative flow characteristics in two other quadrants: for low-output parallel flow (when there is still flow available from the pump of higher head when the ‘weaker’ pump's flow has been reduced to zero), that in the [+H, –Q] quadrant; and for high series flow (after the output head of the pump of lower maximum flow has been reduced to zero), that in the [–H, +Q] quadrant. This problem does not arise when the pumps have identical characteristics.
Product Variability Risks and Robust Design
Authors: Swift K G , Allen A J
Published: February 2007

The design of a product largely predetermines its cost and quality, and there are therefore limits to the benefits that can be obtained by the application of best practice in manufacturing and quality control. The paper introduces a general model of design for quality and describes a systematic quality evaluation methodology to aid the development of quality competitive products. The application and performance of the methodology are described and its integration with techniques in design for manufacture and assembly is discussed.
Product Design in British Manufacturing—New Processes from Old Practices
Authors: Black I
Published: February 2007

Despite the publicity given nowadays to Britain's troubled economic condition, the roots of the demise of British manufacturing can be traced back to the mid-nineteenth century, a time when Britain reached its peak of industrialization and market dominance. However, complacency, mistrust and a general lack of nerve by Victorian society led the workshop of the world down a path that would lead to ongoing industrial decay and stagnation, reflected in Britain's current poor position in the global market-place. During this decline in industrial status modern design processes emerged within a general approach to manufacturing that was incapable of meeting the market demands that were to grow as the twentieth century progressed. This paper, by taking a backward look at product design from the industrial revolution, will show that salutary lessons can be learned from examining past performance. British manufacturing must profit from that experience if it wants to take its place among the leading industrialized nations of the future.
On the Retrospective Balancing of Installed Planar Mechanisms
Authors: Davies T H , Niu G H
Published: February 2007

The paper closely follows the work described in the preceding paper by Chiou and Davies (1) and shares with it the nomenclature and illustrative example. The results of that paper are used here to investigate the feasibility of providing retrospective balancing of existing machines on site. In reference (1) it is shown that unbalance of frequency that is a multiple k of driveshaft rotational frequency can be represented by contra-rotating force vectors Fk+, Fk- rotating about centres Sk+, Sk-, one of which can be chosen arbitrarily.

As explained in reference (1) there are advantages in adding balance mass to existing shafts that rotate at driveshaft speed, notably of course the driveshaft itself, or shafts that rotate at an exact multiple k of that speed. The extrusion press machine described in reference (1) has a driveshaft balance mass. Space is available on the driveshaft to add additional mass as a retrofit measure, but the force exerted by the supplemented balance mass remains less than the first-order unbalance of magnitude F1+ that rotates in the same sense as the driveshaft. The residual unbalance still requires two contra-rotating forces to represent it, but one of these is less than it would otherwise have been without driveshaft balance mass.

It will usually be found that there are boundaries to the regions where additional shafts can be located. This is particularly so within the frame of a machine where it is, to say the least, inconvenient to install shafts that span the width of the machine as a retrofit measure. Attention is therefore directed to balancing one or more frequency terms of the unbalance by additional masses installed external to the frame of the machine. Several means by which this can be done are described: they include the use of two or more additional shafts carrying balance masses and the use of dummy mechanisms. Means of driving the shafts and mechanisms are also briefly discussed.
Precise Robotic Chamferless Peg-Hole Insertion Operation Without Force Feedback and Remote Centre Compliance (RCC)
Authors: Qiao H , Dalay B S , Parkin R M
Published: February 2007

Robots can be widely used in the industrial assembly operation if the task can be performed with high precision, high speed and with low cost. Peg-hole insertion is a fundamental operation whose problems have been the focus of much work.

In the passive accommodation solution, remote centre compliance (RCC) is used to perform chamfered peg-hole insertion). The principle exploited involves using RCC as a mechanical map which transfers the translational and angular errors, between the peg and the hole, into corrective motion. The potential advantages of minimized cycle times are offset by the limited precision. This contrasts with techniques exploiting active accommodation which use a force sensor to arrive at the deviation, between the peg and hole axes, to achieve chamferless insertion.

A strategy is developed here that uses neither of these additional accessories but instead exploits features of both techniques with defined initial conditions. The immediate advantages of reduced hardware complexity are supplemented by evidence of trials. These were based on a 31.99 mm diameter peg and a hole with a diameter clearance of 0.02 mm. The results showed that the algorithm operated reliably with small clearances and with minimum cycle times. This confirms its potentially wide application in industry where its simplicity can be fully exploited.
Experimental Investigation into the Dynamic Plastic Response and Perforation of a Clamped Circular Plate Struck Transversely by a Mass
Authors: Wen H-M , Jones N
Published: February 2007

An experimental investigation is reported on the dynamic response of a clamped circular plate struck transversely by a mass at any point along a radial line. A study is made of the variation of the failure mode with a change of striker diameter-plate thickness ratio, together with an assessment of transverse shear effects and the energy-absorbing capacity for impact velocities up to 12.2 m/s. The experimental results show that the steel and aluminium alloy targets fail by plugging with a plug having approximately the same diameter as the striker, which has a blunt end. The experimental results also show that the energy-absorbing capacity of a plate is reduced significantly when struck by a mass close to the supports compared to a strike at the centre and that the transverse shear force plays a more dominant role when a mass strikes close to the supports. A new criterion for the design of metal targets against projectile impact is proposed.
On the Minimum Volume of Material in Temperature-Compensating Devices
Authors: French M J
Published: February 2007

In temperature-compensating devices of the bimetallic type in which the absolute magnitude of the work done is significant, an absolute lower bound to the volume of material required is established, enabling a rapid assessment of size, weight or cost to be made.
Numerical Simulation of Fume Cupboard Performance
Authors: Khezzar L , Whitelaw J H
Published: February 2007

Calculated distributions of velocity and concentration of a passive scalar for a modern fume cupboard arrangement are shown to be in close agreement with measurements, to quantify the nature of the flow more fully and to demonstrate the consequences of changes in the geometrical and flow boundary conditions. In particular, it is shown that the arrangement of the sash has important consequences for the location of the main longitudinal vortex behind it and that the effect of removing the rear baffle results in the creation of two conical vortices that are scavenged through the top outlet. The calculation method is based on the numerical solution of time-averaged equations; the uncertainties associated with numerical and turbulence assumptions are discussed.
Prediction of Electro-Rheological Valve Performance in Steady Flow
Authors: Peel D J , Bullough W A
Published: February 2007

Previous work has indicated that electro-rheological (ER) fluid in steady valve flow can be approximately characterized by the dimensionless parameters friction coefficient, Reynolds number and Hedström number and the Bingham plastic constitutive equation, and has pointed towards a relationship between tests on valves of various dimensions at different excitations and speeds of flow and comparatively small volume, quick, static clutch mode tests.

In this paper, the position is extended and developed more precisely. The generalized valve flow characteristic is taken, together with simple static clutch determinations of fluid yield properties, zero volt viscosity and valve dimensions to predict valve pressure/flow performance for comparison with valve test data. The static clutch test rig and test procedure are described, and the relationship between static clutch and valve flow determinations of yield stress is then further examined.
Measurement of Thermodynamic Quantities of Mineral Oil By Laser Interferometry
Authors: Washio S , Takahashi S , Kanamitsu M , Yoshida A
Published: February 2007

In previous attempts to find bulk modulus of liquids, the difficulty has always been in how to accurately measure minute volumetric changes in the fluids when pressure changes. The present paper describes the application of laser interferometry to this measurement in a mineral oil in order to develop a more reliable substitute for the conventional methods. Firstly, the basic relationship between density and refractive index of the oil was established by the use of the interference fringe method. Thereafter, the heterodyne interferometer was used to measure thermodynamic changes of state in the oil, giving adiabatic and isothermal compressibilities, specific heats at constant pressure and at constant volume, and specific heat ratio. The velocity of sound in the oil derived from adiabatic compressibility thus obtained agrees well with that determined experimentally through wave transmission tests. The same interferometer has also been shown to be applicable to the measurement of pulsating pressures in oil.
Identification of Coulomb Friction in Robot Drives and Other Mechanical Systems Through Observation of Third Harmonic Generation
Authors: Brookfield D J
Published: February 2007

One of the main difficulties in introducing improved robot control strategies is a lack of knowledge of the frictional behaviour of robot drive systems. The aim of the present paper is to describe a technique for the identification of Coulomb friction based on the response of the robot drive to a sinusoidal driving torque The presence of a third harmonic component in the resulting velocity is a consequence of the Coulomb non-linearity and it is shown theoretically, through computer simulation and in experimental tests, that the coefficient of Coulomb friction can be estimated from the amplitude of the third harmonic component. The identification method is shown to be applicable to any mechanical system that can be subjected to a sinusoidal forcing torque or force.
Application of Discriminated Dimensional Analysis to the Kinematic Stirling Engine
Authors: Prieto J I , Fano J , Diaz R , González M A
Published: February 2007

By means of spatially discriminated dimensional analysis, a complete system of dimensionless groups is proposed to describe the thermodynamic performance of the kinematic Stirling engine From experimental results, homogeneous dimensionless indicated power equations are deduced, as well as equations corresponding to the maximum indicated power operating point. Spatial discrimination evidences conceptual differences between quantities, reduces the number of dimensionless parameters and improves the design method based on dynamic similarity.
Parametric Resonances at Subcritical Speeds in Discs with Rotating Frictional Loads
Authors: Chan S N , Mottershead J E , Cartmell M P
Published: February 2007

This paper is concerned with the parametric resonances in a stationary classical annular disc when excited by a rotating mass-spring-damper system together with a frictional follower load. An analysis by the method of multiple scales is performed to reveal the existence of instabilities associated with subcritical parametric resonances, and other instabilities of the backward waves in modes with nodal diameters. The latter are shown to be driven by friction and not to be dependent upon the rotational speed. A state-space analysis, with truncated modes, is used to investigate the effect of varying the friction, stiffness, mass and damping prameters in a series of simulated problems. The results obtained from the state-space eigenvalue method tend to support the conclusions of the multiple scales analysis.
The Effect of Chassis Torsional Stiffness and Suspension Roll Stiffness Distribution on Truck Handling
Authors: Hinzburg L L , Nosencoff M A
Published: February 2007

In the design of a new vehicle, optimization of stability and handling is in conflict with optimization of ride and vibration, and with durability of suspension and structural components The purpose of this study, in which vehicle handling was the focus of attention, was not to provide specific vehicle recommendations but rather to reveal the main trends used to assist the design process. The maximum speed of a 20 m long 3.5 m offset lane-change manoeuvre to avoid an obstacle was investigated, this being defined as the velocity of the vehicle when it could not follow the marked traffic lane or lifted a wheel.
A Method for Assessing the Rollover Stability of Articulated Tipping Trailer Units under Tipping Conditions
Authors: Hyde T H , Fessler H , Pickering S G
Published: February 2007

Because the chassis, suspension and tyres of a tipping trailer unit are flexible, when standing on sloping ground, the body tilts more than the sideways slope of the ground on which it is standing. This changes the positions and directions of the resultant forces due to self-weight, payload and sideways wind relative to the hinge bar which allows the body to be tipped. These changes alter the magnitudes of the forces exerted on the chassis at the hinges and by the lifting ram; this changes the forces exerted through the air suspension on to the rear wheels. When the force exerted by a rear wheel becomes zero, rollover is imminent.

All of the above changes have highly non-linear effects. Further non-linearities are due to the operation of the airbag suspension. This paper defines these effects and describes iterative methods to predict the position of the body relative to the ground for any trailer unit under specified conditions and to predict the ram length at which rollover would occur.
Meeting the Challenge of Low Emissions and Fuel Economy with the Ricardo Four-Valve High-Speed Direct Injection Engine
Authors: Needham J R , Whelan S
Published: February 2007

In order to investigate and demonstrate the potential of the high-speed direct injection (HSDI) diesel engine, Ricardo have undertaken a programme of research and analysis into the performance and emissions of a four-valve/cylinder combustion system. Analytical studies were based on a computational fluid dynamics investigation to model in-bowl events of fuel spray/air interactions and to improve understanding of the mixing processes.

The major variables studied during the test programme included swirl ratio, combustion bowl geometry, nozzle configuration, contemporary and advanced electronic rotary fuel injection pumps and the effects of exhaust gas recirculation (EGR). A systematic optimization programme provided a fixed swirl configuration capable of achieving in excess of 15 bar b.m.e.p. (brake mean effective pressure) while providing less than 1.0 Bosch smoke unit. R49 EURO II NOx levels were met with competitive smoke, particulate emissions and fuel economy, demonstrating excellent potential for full EURO II compliance with further development. Vehicle emissions and fuel consumption simulations have shown that the combustion system has the potential to meet both the heavy and light duty emissions legislation planned for the 1990s.
Strain Distributions in Hemispherical GRP Vessels with Radial Branch Connections Subject to Internal Pressure and Radial Load
Authors: Leach J , Soden P D W , Kitching R
Published: February 2007

Experiments were conducted on two glass fibre reinforced plastic (GRP) hemispherical vessels, each of internal diameter 1 m. Each had a radial cylindrical nozzle, of 200 mm inside diameter, of similar construction to the vessel which consisted of layers of ‘E’ glass fibre chopped strand mat with a polyester resin matrix. One vessel was reinforced local to the nozzle, while the other had no such reinforcement. Strain gauges on internal and external surfaces were used to measure strain distributions due to internal pressure loading and separately due to local loads applied along the axis of the nozzle. For those tests strains were restricted to values below 0.2 per cent. The measured strain distributions were compared with strains calculated by the thin shell computer code BOSOR4. Finally, tests to destruction were carried out on both vessels under internal pressure with strains being measured up to the level of reliability of the gauges. The agreement between measured strains and those predicted by the thin shell theory was good, except at the nozzle/sphere junction.
New Bogie for German ICE (InterCity Express) Based on BT41
Authors: Freitag C , Karch S
Published: February 2007

Since 1979, the SIG Swiss Industrial Company (SIG) has been developing a modular construction system for bogies. Recently its range has been expanded by the addition of two new bogie modules that will run on high-speed lines. One is for the bogie that British Rail InterCity 225 trains have been equipped with since 1989, which is designed to run on conventional railway track at speeds of up to 225 km/h. As a further development of this model there is now a second module for a high-speed bogie which runs at 300 km/h on new purpose-built track. This paper provides an account of the development, construction and testing of these two types of bogie.
A Finite Element Model of Railway Track and its Application to the Wheel Flat Problem
Authors: Dong R G , Sankar S , Dukkipati R V
Published: February 2007

To study the dynamic interactions between the railway vehicle and track, a finite element model of infinitely long track is developed. The track is represented by a Timoshenko beam on discrete pad-tie-ballast supports. The non-linear factors such as loss of wheel-rail contact, rail lift-off from the tie and tie lift-off from the ballast are taken into account. A multi-point wheel-rail contact model is also proposed. The dynamic forces on the track and the strains on the rail are directly calculated from the model. The vehicle could travel on the track forever with an arbitrary time-dependent speed. The steady-state response of a vehicle-track system for a perfect wheel carrying a constant load and travelling at a constant speed over a track with no irregularities is studied using the finite element model and is presented. The impact loads due to wheel flats are also studied with this model. The results show a good correlation with the experimental data available in the literature. Influences of system parameters on the impact loads due to a wheel flat are also investigated. T***he results show that the axle load and vehicle speed are the important factors affecting the wheel-rail impact loads. The impact forces transferred from the rail to the tie are strongly affected by the pad stiffness and tie mass.
Static Strength and Fatigue Performance of Aluminium-Adhesive T-Peel Joints
Authors: Gilchrist M D , Smith R A
Published: February 2007

Numerical predictions of the tensile stresses within adhesively-bonded aluminium T-peel joints have established where critical fatigue defects are likely to initiate and propagate to fracture. These predictions of maximum stress correlate directly with static strength measurements of such joints. The results presented within this article elucidate the region of cohesive crack initiation, its subsequent direction of propagation and the relative duration of the different stages of fatigue crack growth. Separate stages of embedded, surface and through-width fatigue growth of cohesive defects with a T-peel joint are identified and compared. In this manner the fatigue life of typical bonded aluminium-epoxy T-peel joints has been established from the first stages of crack initiation to final joint fracture. It has been shown that joint static and fatigue strengths are maximized by having a maximum amount of adhesive within the fillet region of the joint.
An Experimental and Numerical Analysis of Riveted Single Lap Joints
Authors: Fung C-P , Smart J
Published: February 2007

Countersunk and snap riveted single lap joints have been examined both experimentally and numerically. A total of 11 specimens were fatigued to failure with failures occurring in either the plate or the rive***r. The failures have been metallurgically examined to determine the cause of failure.

The joints have also been analysed using the finite element method. Initially a single lap joint has been modelled as a ‘stepped plate’ and the results for the stress concentration factor found to be in reasonable agreement with published data. However, the stress concentration for this joint occurred at a point away from the point of failure of a riveted joint.

A fuller three-dimensional finite element model has been constructed and the stress patterns around the rivet determined. These stress patterns are discussed in relation to the results from the metallurgical examination.
Lynx Main Rotor/Tail Rotor Interactions: Mechanisms and Modelling
Authors: Ellin Lt Cdr A D S
Published: February 2007

A flight trial has been conducted by the Defence Research Agency (DRA) Bedford using a Lynx AH Mk5 helicopter fitted with an instrumented tail rotor to collect data on tail rotor aerodynamic performance. The analysis carried out to date has concentrated on the effects of main rotor wake interactions on the tail rotor. This paper describes the trial and the analysis in broad outline and discusses in detail mechanisms to explain three out of the six main rotor/tail rotor interactions found. The modelling of these effects to improve the fidelity of ground-based flight simulation is also covered.
Assessment of Titanium Alloy on Polyethylene Bearing Surfaces in Retrieved Uncemented Total Hip Replacements
Authors: Drabu K J , Michaud R J , McCullagh P J J , Brummitt K , Smith R A
Published: February 2007

Changes to the bearing surfaces of eighteen uncemented total hip replacements retrieved at revision surgery were assessed by three-dimensional binocular microscopy, Rank Taylor Hobson talysurf measurements, scanning electron microscopy, and X-ray dispersive analysis. Abrasions on the non-articular surface of the polyethylene cups were present. Bone particles were found in tracks in the bearing surfaces of both the titanium femoral heads and the polyethylene cups and were responsible for wear of these surfaces. Although the wear of the femoral heads appeared substantial to naked eye examination, the surface finish of these surfaces remained within the British ISO standards for titanium alloy when assessed by the methods used above. This study concluded that direct contact between polyethylene and bone should be avoided in total hip arthroplasty and that ‘third body’ wear from bone particles occurred in these uncemented prostheses. Both components of this type of implant should be replaced at revision surgery and titanium should be avoided as a bearing surface in hip arthroplasty. Present methods of assessing the surface finish of titanium should be re-evaluated and more reliable ones considered.
Axisymmetric Finite Element Analysis of Hip Replacement with an Elastomeric Layer: The Effects of Layer Thickness
Authors: Strozzi A , Unsworth A
Published: February 2007

Finite element analysis of compliant layered artificial hip joints has been used to study the mechanical response of four different layer thicknesses from 0.5 to 3 mm. The results have been compared with a classical asymptotic model in terms of maximum contact pressure and contact width, and of maximum shear stress at the layer-backing interface and its location. The surface deformations and load capacities have also been compared. The best thickness was found to be 2 mm; though a marginal reduction in stresses would be found in the 3 mm layer, the penetrations would be greater and these might have implications for the fatigue life of the material.

A formula for the thickness of the fluid film has been derived on the basis of the inverse hydrodynamic theory and the results show good correlation with existing theories.
A Simple Device for Measurement of Load-Bearing Forces during Walking
Authors: Harrison A J , Atkins R M , Scott H J F
Published: February 2007

A low-cost, portable, unobtrusive and non-invasive system has been developed, capable of measuring human gait forces over a 16 how-period, and characterized and proven in limited trials. The device comprises a foam insole containing a coiled air-filled elastic tube whose internal pressure (which increases under load) is measured by a pressure gauge. This signal is recorded by a small data logger worn around the patient's waist, and subsequently downloaded to a personal computer for analysis. Typical results are presented. The system will initially be used with patients recovering from tibial and femoral shaft fractures to monitor their day-long load-bearing patterns. The results of this study will be used to investigate a causal relationship between load bearing and the extent and rate of osteoporosis, which will be measured separately. In the future, additional studies of gait, load bearing and general mobility of patients suffering from conditions such as arthritis and amputation will be undertaken.
An Adaptive Control System Incorporating H∞ Concepts for High-Speed Machinery with Independent Drives
Authors: Beaven R W , Wilkes L D , Wright M T , Garvey S D , Friswell M I
Published: February 2007

Current state of the art in the design of high-speed machinery for the production or processing of discrete products often involves the use of independent drives synchronized through controllers, rather than via stiff mechanical connections. High-speed machinery for discontinuous processes tends to be characterized by the following attributes: (a) synchronization is highly critical between the axes in certain groups; (b) strong coupling between axes (groups) can be introduced by the work material; (c) the speeds of operation are such that computation is at a premium and just be restricted; (d) individual axes have periodically varying parameters (with additional non-periodic noise); (e) individual axes can become strongly non-linear at high torque (or force) rates; (f) slow and steady trends in the plant parameters are common; and (g) the development of reliable, high-fidelity dynamic models of all machine components for perfect design simulation is impracticable. This paper addresses the issue of how controllers may be specified and designed to provide control solutions for high-speed machinery, which provide the designer with a high degree of confidence that simulated performance may be realized in practice. The form of the solution proposed is an adaptive decentralized control scheme with a recursive identifier to track machine parameter variations. H∞ design methods are used both to specify the form of the control system and to ensure ongoing robust control of the machinery with minimum sacrifice of performance. Three examples are given(two simulation and one experimental) to demonstrate the benefits of using H∞ methods, rather than traditional methods, for this type of machinery, and one of these illustrates the effectiveness of adaption for maximizing performance while maintaining stability.
Occupancy and Refurbishment Effects on Digital Modelling for Buildings
Authors: Virk G S , Cheung J Y M , Loveday D L
Published: February 2007

The paper considers the application of stochastic modelling to building energy management systems. The results presented relate to research conducted on a full-scale experimental test room with its own dedicated HVAC plant. It is shown that the digital models deduced from correlating the system input/output and climatic data can be used not only to accurately predict the thermal behaviour in the room, but also to allow for the effects of occupancy. In particular, the effects of altering futniture and fittings within the occupied spaces are discussed.
QLQG/LTR Control for Hard Non-Linear Multivariable Systems
Authors: Kim J S
Published: February 2007

A new non-linear multivariable control method called the QLQG/LTR method is presented, which is the integration of statistical linearization, loop-shaping and loop transfer recovery techniques. The QLQG/LTR method is a powerful one for designing controllers of non-linear systems with hard non-linearities such as Coulomb friction, backlash and saturation. In order to show the effectiveness of the QLQG/LTR method, the LQG/LTR and QLQG/LTR methods are applied to a robot manipulator with Coulomb friction. The computer simulation results show that the performance and stability robustness of the QLQG/LTR control system is insensitive to the magnitude and direction of the command input.
Non-Linear Control for Uncertain Systems
Authors: Spurgeon S K
Published: February 2007

This paper presents a review of a number of state-of-the-art non-linear control design techniques which may be readily applied to solve practical problems in a robust fashion. It is first shown that non-linear controllers may be designed using straightforward linear models with minimal recourse to abstract mathematical concepts. More involved philosophies for robust control system design of inherently non-linear plants are then briefly described. A straightforward yet rigorous design framework is then presented to implement the philosophy. Tutorial examples are presented throughout the paper in order to illustrate major points of interest.
An On-Line Approach to Fault Diagnosis of Fluid Power Cylinder Drive Systems
Authors: Watton J , Lucca-Negro O , Stewart J C
Published: February 2007

An approach is presented whereby a number of faults, typical of many hydraulic circuits, may be determined using rule-based concepts. The approach uses on-line data and principally integrates both qualitative and quantitative reasoning in a novel way that enables speciJic faults to be detected. It has the advantage of being able to indicate a class of multiple faults and can also provide some indication of sensor integrity. A practical example is presented using an open-loop meter-inlmeter-out flow control system, and a variety of single and multiple faults have been studied with respect to leakages, check valves andflow control valve behaviour.
Self-Tuning Active Vibration Control in Flexible Beam Structures
Authors: Tokhi M O , Hossain M A
Published: February 2007

This paper presents the design and performance evaluation of an adaptive active control mechanism for vibration suppression inflexible beam structures. A cantilever beam system in transverse vibration is considered. First-order central finite difference methods are used to study the behaviour of the beam and develop a suitable test and verification platform. An active vibration control algorithm is developed within an adaptive control framework for broadband cancellation of vibration along the beam using a single-input multi-output (SIMO) control structure. The algorithm is implemented on a digital processor incorporating a digital signal processing (DSP) and transputer system. Simulation results verifying the performance of the algorithm in the suppression of vibration along the beam, using single-input single-output and SIMO control structures, are presented and discussed.
The Behaviour of Transverse Roughness in EHL Contacts
Authors: Greenwood J A , Morales-Espejel G E
Published: February 2007

By assuming the contact geometry in elastohydrodynamic lubrication (EHL) to be that of an infinitely long contact with given nominal film thickness and mean pressure and considering the elastic displacements of the separate components of the initial roughness, it is possible to extend the Greenwood and Johnson analysis for sinusoidal pressure to any two-dimensional roughness. For typical EHL pressures the viscosity effects are negligible, so the Reynolds equation can be linearized and solved analytically; the solution provides a criterion to relate the amplitudes of the undeformed and deformed roughness to the wavelength, and shows that roughness with a short wavelength is likely to persist after deformation. The linearization of the Reynolds equation is extended to the transient case and it is found that the complete solution is made of two separate parts: the particular integral (steady state solution) and the complementary function (which depends on the entry of the partly deformed roughness into the Hertzian zone).
The Effect of Extreme Pressure (EP) Lubricants on the Life of Rolling Element Bearings
Authors: Wan G T Y , Lankamp H , de Vries A , Ioannides E
Published: February 2007

Bearing tests showed that lubricants containing sulphur and phosphorus extreme pressure (EP) additives reduce the life of rolling bearings compared with similar lubricants without EP additives. High-resolution electron microscopy revealed a remarkable difference of contact surface topography and microstructural changes between bearings tested with or without EP additives.