bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigations into the Precessing Vortex Core Phenomenon in Cyclone Dust Separators
Authors: Yazdabadi P , Griffiths A J , Syred N
Published: February 2007

Experimental investigations have been carried out to examine the effect of downstream pipework configurations on the precessing vortex core (PVC) generated within the exhaust region of a cyclone dust separator. Characterization of the PVC using a non-dimensionalized frequency parameter (NDFP) was used to determine the relationship between Reynolds number and geometrical swirl number of the cyclone.

The results show that the NDFP tends towards an asymptotic value for Reynolds numbers of about 50 000 and high swirl numbers (> 3.043). This value is reached earlier with lower swirl numbers. It was concluded that any exhaust pipework configuration produced a significant drop in the PVC frequency, and certain configurations either delayed or promoted the development of the PVC.
Clearances between the Rotors of Helical Screw Compressors: Their Determination, Optimization and Thermodynamic Consequences
Authors: Tang Y , Fleming J S
Published: February 2007

Although helical screw compressors contain only two moving parts, their shapes are very complicated and must mesh to very fine clearances. The process of determining lobe geometry requires that parts of the male generate parts of the female and vice versa. Once the nominally perfect (zero clearance) profile geometry has been generated, a method for determining clearances is needed which gives an attainable result from the manufacturing and operational viewpoints and gives a thermodynamic efficiency which is at least equal to that of competing machines of the same class. The thermodynamic performance depends principally on the internal leakage rates in the compressor, in particular, the leakage across the contact (sealing) line.

This paper presents two ways of setting clearances. They result in different patterns of clearance distribution along the sealing line and have different effects of the thermodynamic performance of the compressor due to the different leakage mass flowrates that they permit. A design technique for obtaining an optimum clearance distribution is discussed.

Finally, a thermodynamic model of compressor behaviour is used to predict the performance as influenced by the different clearance distributions, and the predictions are compared with measured values taken from a test compressor. The predictions are shown to be good.
Energy Conservation via Optimal Control of Cone Crushers
Authors: Parkin R M , Bearman R A
Published: February 2007

The quarrying industry has a major impact on the environment. The impact arises from direct sources (that is the quarrying operation with attendant noise and dust) and indirect sources (that is electricity usage). To quantify these usages, the quarrying industry in the United Kingdom consumes some 4.8 TW h/year, representing 3 per cent of installed generating capacity. A significant proportion of this usage is attributable to machines known as cone crushers. Cone crushers are large items of plant (up to 3 m diameter) producing, mainly, aggregates for the road-making industry. The British output is currently 230M tonnes per annum, due to rise to 400M tonnes by 2011. The energy costs are currently £240M per annum.

Further environmental issues are raised by the use of manganese steels. A crusher uses, components that can wear away at a rate of 1 mm per hour. If the parts are not renewed at regular intervals machine performance can be dramatically affected and, in the worst case, mechanical damage may occur. The parts are replaced early to avoid damage with a concomitant poor energy utilization.

The paper describes a programme of work intended to address some of these problems. Pegson Limited, a leading manufacturer of crushing plant, in association with Transfer Technology plc and De Montfort University, are co-operating in a project funded by SERC/DTI under the design of high-speed machinery LINK programme, Treatment is theoretical, demonstrating the justification of the funding. A follow-up paper will detail actual savings and contrast them with the theoretical model.

The next generation of crushers will be instrumented with a range of sensors to monitor machine performance. Of especial interest is a novel sensor which monitors the wear of the crushing components The sensors are connected to a knowledge-based system (KBS) to monitor and control performance. The sensors are not reported in any detail due to the pursuance of Intellectual Property Rights. The ideal performance parameters are obtained from another KBS based on rock mechanics and models of wear mechanisms.

The advanced crushers incorporate a simple man/machine interface and make much use of distributed control based on NEC 78K series microcontrollers. Preliminary studies indicate that energy savings of £15M in the United Kingdom (over £400M worldwide) per year are realizable. Further savings of £5M in the United Kingdom (nearly £150M worldwide) per year arise from the optimal use of the manganese crushing components.
A Comparative Study on Lateral Stability and Steady State Curving Behaviour of Unconventional Rail Truck Models
Authors: Swamy S Narayana , Dukkipati R V , Osman M
Published: February 2007

Conventional railway vehicle systems exhibit hunting phenomenon which increases component wear and imposes operating speed limits. There is also a conflict between dynamic stability and the ability of the vehicle to steer around curves. Alternatively, independently rotating wheels (IRW) in a wheelset eliminate hunting but the wheelset guidance capability is lost. A compromise solution is made possible by a modified design that exploits a lack of fore-and-aft symmetry in the suspension design. A comparative study on steady state curving performance and dynamic stability of some unconventional truck designs is carried out. The effects of suspension and conicity are considered to evaluate the trade-off between dynamic stability and curving performance.
Passenger Detrainment and Tunnel Evacuation—Theory, Modelling and Experience
Authors: Keenan M T , Pittman K G , Stephens P J , Ketchell N
Published: February 2007

A consideration of the theory, mathematical modelling and actual experience of the evacuation of people, with particular reference to detrainment underground and evacuation along tunnels.
Fatigue Life Evaluation of a Railway Vehicle Bogie Using an Integrated Dynamic Simulation
Authors: Luo R K , Gabbitas B L , Brickle B V
Published: February 2007

An integrated design methodology has been developed for the fatigue life evaluation of railway vehicle bogies. In principle, there are five parts in the procedure: specification and measurement of track irregularities; modelling a railway vehicle and description of rail-wheel profiles; obtaining the railway vehicle suspension load histories; dynamic analysis and stress evaluation of the bogie frame; fatigue life evaluation of the bogie. The whole procedure has been applied to a typical London Underground railway vehicle. The theoretical results have been validated against field test data and fatigue calculations have indicated good agreement with operational data from the actual vehicles. It has been shown that a design methodology for railway vehicle bogies based on the track profiles on which they will run and on their own structural characteristics is possible and can be used at an appropriate stage in the design process.
Advanced Materials for Aerospace Structures
Authors: Dorey G , Peel C J , Curtis P T
Published: February 2007

The role of materials in aerospace structures is discussed in terms of engineering performance, at affordable costs, for a variety of applications. Vehicle performance can be extended by improved materials performance and examples are given of new materials (alloys, polymer matrix composites, metal matrix composites and hybrid laminates), from the concept of new microstructures through development of new manufacturing processes to pilot scale production.
Experimental Investigation into the Vibration Response of an Aero-Engine Rotor-Damper Assembly
Authors: Levesley M C , Holmes R
Published: February 2007

This paper presents experimental results on the non-linear vibration response of a rotating assembly comprising a rotor, flexible bearing housing and oil film damper. For the latter, due consideration is given to the effects of oil-supply pressure, film-rupture pressure and end sealing. The results are compared with predictions based on the Harmonic Balance principle described in a complementary paper (1).
The Study of Transonic Flows by Quantitative Holographic Interferometry
Authors: Parker S C J , Holden C M E , Bryanston-Cross P J
Published: February 2007

Optical flow diagnostics are non-intrusive and therefore suitable for investigating perturbation sensitive transonic flows. Unfortunately, most of these techniques depend on particle seeding and are confined to point measurements. In contrast, holographic interferometry is whole field, does not require seeding, and is an appropriate tool for the study of temporal and spatial properties of unsteady flows. At present, however, holographic interferometry is mainly used qualitatively due to the practical restrictions of data recording, acquisition and processing.

This paper addresses some of the limitations that have prevented routine use of holographic interferometry in production wind tunnel testing. Vibration is a frequent problem when capturing interferometric data; however, this paper shows that the associated rigid body movements are easily removed during Fourier transform fringe analysis. A second major limitation arises when attempting to interpret and analyse interferograms from three-dimensional flows. To overcome this problem, a prototype optical system is described which can record multiple interferometric views around the working section. The information extracted from these images may then be used to tomographically reconstruct the three-dimensional density field.

Holographic measurements for two-dimensional and three-dimensional axisymmetric flows are presented and compared quantitatively to computational fluid dynamics (CFD) predictions. The experimental and computational results are in general agreement and demonstrate the feasibility of automating the extraction of three-dimensional density data from holographic interferograms.
The Life And (Maintenance) Times of an A300 Tailplane Trim Actuator—A Systems Perspective
Authors: Badger M
Published: February 2007

In order to achieve the required level of system safety, it is often necessary to specify scheduled single system check periods for duplicated or triplicated systems, where failure of one system is neither indicated nor evident to the pilot or ground crew.

This paper presents the techniques used in the analysis of the A300 tailplane trim actuator service data, for the purpose of identifying a check period and overhaul life, consistent with continued safe economic operation.
Experimental Testing of Prototype Face Gears for Helicopter Transmissions
Authors: Handschuh R F , Lewicki D G , Bossler R B
Published: February 2007

An experimental programme to test the feasibility of using face gears in a high-speed and high-power environment was conducted. Four face gear sets were tested, two sets at a time, in a closed-loop test stand at pinion rotational speeds to 19 100 r/min and to 271 kW (364 b.h.p.). The test gear sets were one-half scale of the helicopter design gear set. Testing the gears at one-eighth power, the test gear set had slightly increased bending and compressive stresses when compared to the full-scale design. The tests were performed in the NASA Lewis spiral bevel gear test facility. All four sets of gears successfully ran at 100 per cent of design torque and speed for 30 million pinion cycles, and two sets successfully ran at 200 per cent of torque for an additional 30 million pinion cycles. The results, although limited, demonstrated the feasibility of using face gears for high-speed, high-load applications.
An Initial Parametric Study on Fluid Flow Through Bileaflet Mechanical Heart Valves Using Computational Fluid Dynamics
Authors: King M J , David T , Fisher J
Published: February 2007

The effect of leaflet opening angle on flow through a bileaflet mechanical heart valve has been investigated using computational fluid dynamics (CFD). Steady state, laminar flow for a Newtonian fluid at a Reynolds number of 1500 was used in the two-dimensional model of the valve, ventricle, sinus and aorta. This computational model was verified using one-dimensional laser Doppler velocimetry (LDV). Although marked differences in the flow fields and energy dissipation of the jets downstream of the valve were found between the CFD predictions and the three-dimensional experimental model, both methods showed similar trends in the changes of the flow fields as the leaflet opening angle was altered. As the opening angle increased the area of recirculating fluid downstream of the leaflets, the pressure drop across the valve and the volumetric flow rate through the outer orifice decreased. For opening angles greater than 80° the jet through the outer orifice recombined with the central jet downstream of the leaflet; for an opening angle of 78° the jet through the outer orifice impinged on the aortic wall before recombining with the central jet. This study suggests that the opening angle has a marked effect on the flow downstream of the bileaflet mechanical heart valve and that valves with opening angles greater than 80° are preferable.
Finite Element Analysis and Mechanical Testing of External Fixator Designs
Authors: Prendergast P J , Toland S J , Corrigan J P
Published: February 2007

Experimental and theoretical stress analysis methods are used to evaluate the mechanical behaviour of external fixation devices as load-bearing structures. For the experimental part, a modular assembly was fabricated from which unilateral and bilateral fixators of different design configurations were assembled and tested under various loading conditions. A reflective photoelasticity technique was used to study the effect of frame configuration on the stress patterns generated around the pin-bone interface. Finite element models of each design were also generated using three-dimensional beam and shell elements. Spring elements were used to model the pin/sidebar clamp. It is shown that close correspondence between the experimental and theoretical methods of investigation is obtained when the flexibility of the pin/side-bar clamp is taken into account. It is also shown that a unilateral design, modified by attaching a second side-bar to the first and connecting them by means of a semicircular component, can achieve some of the structural advantages of bilateral fixators without the clinical disadvantage of transfixing pins.
The Response of Mammalian Muscle to Distraction—A Study in the Rabbit
Authors: Kyberd P J , Williams P E , Simpson A H W R , Goldspink G , Kenwright J
Published: February 2007

‘Distraction’ is the technique of lengthening of bones to correct deformities in limbs of individuals; it is established practice in orthopaedic surgery. Large increases in length of the bone can be achieved, but the associated soft tissues do not appear to be able to respond as rapidly. The aim of this study was to assess the response of muscles in the leg of New Zealand rabbits to distraction. At the end of a period of lengthening, the function of the limb and that of the muscles (tibialis anterior and soleus) was tested and compared with the histology to measure the level of accommodation that can be achieved by the muscle. The results show that muscle responds more slowly to the lengthening regime than the supporting bone. Thus it is the muscles' ability to respond to the distraction that is an important factor when deciding the rate of distraction.
Assessment of the Change in Volume of Acetabular Cups Using a Coordinate Measuring Machine
Authors: Derbyshire B , Hardaker C S , Fisher J , Dowson D , Brummitt K
Published: February 2007

It is necessary to accurately measure the change in volume of ultra-high molecular weight polyethylene (UHMWPE) acetabular cups during hip simulator tests in order to determine wear rates. This study investigates the accuracy of dimensional measurement of an acetabular cup socket using two different coordinate measuring machines. The repeatability of the measurement was found to be primarily dependent upon the accuracy of relocation of the datum before each set of measurements.
Pulsatile Performance of Two Valved Conduits Used as Cardiac Valve Replacements
Authors: Gentle C R , Leefe S E
Published: February 2007

Pulsatile in vitro flow tests are reported on a Björk-Shiley conduit disc valve and a prototype ball valve conduit, both used as replacements for the aortic valve and ascending aorta. Comparison is made with a model of the aortic stenosis which the conduits would be used to replace. It is found that although the ball valve is considerably better than the disc valve, in terms of pressure drop and power loss for a given cardiac output, both prostheses offer large improvements on the stenotic situation.
Contact Mechanics of Soft Layer Artificial Hip Joints: Part 1: General Solutions
Authors: Yao J Q
Published: February 2007

Unlike natural synovial joints, which are lubricated with a full fluid film lubrication mechanism, conventional artificial hip joints are lubricated with a mixed lubrication mechanism. Recently, however, a new generation of artificial hip joints employing compliant layers to mimic the compliance of articular cartilage in natural synovial joints have been developed to provide fluid film lubrication in these joints. While satisfactory lubrication can be achieved by employing soft layers, compliant thin layers are susceptible to the debonding between the soft layer and its stiffer substrate and long-term mechanical fatigue failure. Stress analyses for different designs of such joints are therefore important. In the present paper, the circular contact between a rigid sphere and an elastomeric layer bonded on to a rigid substrate has been analysed with a novel semi-analytical approach. The detailed contact parameters (the contact radius, the maximum surface deformation, the contact pressure and the contact stress inside the layer) have been examined for a wide range of aspect ratios (0 ≤ a/ht ≤ 100).
The Reaction of Skin and Soft Tissue to Shear Forces Applied Externally to the Skin Surface
Authors: Zhang M , Turner-Smith A R , Roberts V C
Published: February 2007

The reaction of skin and soft tissue to shear force applied externally to the skin surface has been investigated by the experimental measurement of skin blood flow and model analysis of internal stresses. Skin blood flow has been measured using laser Doppler flowmetry while variable shear forces and normal force were applied to the skin surface. The experimental results show that the skin blood flow is reduced by increasing either normal force or shear force; the magnitude of the reduction being nearly proportional to the resultant of the normal and shear forces. The internal stresses were analysed by simplified models incorporating elasticity theory. The analyses indicate that shear force changes the stress distribution mainly in the superficial layer of the soft tissue and increases the stress in the area ahead of the direction of application; the maximum internal compression stress was found to be determined by the resultant of normal and shear forces. The study suggests that the resultant force is the most critical parameter in assessing the effect of load applied to the skin; and shear force has the same effect on skin and underlying tissue as normal force.
Dynamic Characterization of Human Tendons
Authors: Schechtman H , Bader D L
Published: February 2007

Human tendons were tested in uniaxial tension with the use of specially designed grips and the local measurement of tendon cross-sectional area. The resulting stress-strain relationship was non-linear in form, with the modulus of elasticity initially increasing to a constant value which decreased as the tendon failed. The ultimate tensile strength (UTS) for the extensor digitorum longus and extensor hallucis longus tendons were 99.9 ± 12.2 MPa and 87.1 ± 125 MPa, respectively. Dynamic characterization of those tendon specimens was achieved by the method of forced oscillations using dedicated software on a hydraulic testing machine. Specimens were subjected to cyclic tension-tension loads at frequencies in the physiological range of 1–4 Hz. The sta*** load was set at values corresponding to prescribed levels between 10 and 80 per cent of the calculated UTS. Results suggest that both the dynamic modulus and the storage modulus were non-linearly proportional to the mean static stress level reaching a peak value at 60 per cent UTS, whereas the loss modulus was independent of the mean static stress. All three dynamic parameters were generally independent of frequency. The trends in the dynamic parameters were explained in terms of the loading/unloading response of tendons, as well as the structural organization of their collagen fibres.
Computer Simulation of Human Interaction with Underwater Breathing Equipment
Authors: Tomlinson S P , Lo J K W , Tilley D G
Published: February 2007

A mathematical model of the human respiratory system is being developed in order to simulate manned diving operations using various types of breathing equipment. A simulation study is presented of a human diving to a depth of 50 m, using a semi-closed re-breathing system with two different oxygen flow settings. A gas supply with 32.5 per cent oxygen concentration results in a safe dive whereas a 60 per cent setting indicates a dangerous diving condition. Typical respiratory model input data are illustrated for the lung, together with dimensional details for the re-breathing counterlung. The simulation results show variations in alveolar and pleural pressures, gas concentrations and partial pressures in the equipment and in the human respiratory system.
Design and Implementation of a Neural Network Controlled Electro-Hydraulic Drive
Authors: Newton D A
Published: February 2007

Hydraulic systems are commonly used in industry when large forces of torques are required. Increasing demands for positional, force and speed control from users have led to the use of closed-loop control techniques. While classical controllers are used successfully for many hydraulic applications, they cannot cope with the non-linearities inherent in hydraulic systems or the changes to system parameters over time. This paper considers these problems and proposes a solution in the form of a neural network-based controller in the forward path of the system directly controlling the hydraulic plant. A network-learning mechanism is also proposed to train the network to minimize the system error and examples are given of the implementation with comparisons against a PID controller. The examples illustrate the rapid convergence of the training algorithm and the robustness properties of a simple two-neuron, two-input network controlling a non-linear time-varying plant.
The Implementation of the Minimal Control Synthesis Algorithm on a Web Control Problem
Authors: Stoten D P , Dye M G , Webb M
Published: February 2007

The minimal control synthesis (MCS) algorithm is an adaptive control strategy that requires no prior knowledge of plant dynamic parameters, and yet is guaranteed to provide global asymptotic stability of the closed-loop system. The purpose of this paper is to present MCS as applied to web tension und transport control a class of plant that has highly non-linear dynamics and time-varying parameters. The plant is difficult to control by conventional methods over its full operating range. A typical example and model of such a plant is presented along with the implementation of MCS. Experimental comparisons of MCS with conventional control benchmarks are provided. It will be seen that MCS significantly outperforms the conventional controller.
A Switched-Reluctance Motor Drive with Zero Torque Ripple and a Constant Inverter Bus Current
Authors: Dunlop G
Published: February 2007

Switched-reluctance motors appear to be ideal industrial prime movers capable of precision speed and position control. The efficiency can be higher than for a similar-sized induction motor and the electronics less complicated for precise speed control. While the switched-reluctance drive is common in some applications, it has not been widely accepted because of the large amount of torque ripple produced. The torque ripple from the widely used induction motor is quite low and it causes less vibration in the mechanical drive train following the motor. A four-phase switched-reluctance motor can he operated in such a way as to produce a constant zero-ripple torque output. The currents in at least two of the four phases are set so that the total torque produced is constant. By precisely setting the currents in three of the four phases, a constant torque output can be obtained at a constant d.c. supply current, and the switched-reluctance motor then has similar characteristics to a d.c. series motor. A mathematical description of these non-linear currents is derived along with the individual and mutual torque contributions to the total constant torque. The equations are also shown in graphical form.
Finite-Time Settling Control of a Flexible Arm
Authors: Choura S
Published: February 2007

This paper considers the position control of a flexible beam attached to a rotating rigid hub. The control torque is applied at the hub through a motor. A state-space model describing the motion of the flexible beam is developed and is employed in the design of the control law. The finite-time settling control strategy that combines feedback and feedforward is applied to the beam problem. The feedback part is separately designed to resolve the issues of asymptotic stability and robustness to uncertainties. The feedforward part simultaneously suppresses the rigid-body mode and a finite set of flexible modes at the end of manoeuvre and, therefore, it is the part responsible for the finite-time settling of the beam to its final configuration. It is shown that if the finite-time settling control is compared with previously developed control strategies under the same input bound constraint, it leads to a better suppression of vibrations at the end of manoeuvre, provided that a sufficient number of flexible modes are incorporated in the computation of the feedforward control law. A robustness test is carried out to show the viability of the control strategy supported by computer simulations.
Prediction of Forming Pressure Curve for Hydroforming Processes Using Artificial Neural Network
Authors: Hyun B S , Cho H S
Published: February 2007

In a hydroforming process, forming pressure versus punch stroke is critical to product quality, and thus the operating pressure curve is strictly controlled according to a preplanned control method. The conventional method of determining such a curve is trial and error, which demands tremendous effort and high cost. In this paper, a neural network approach is proposed to replace the conventional method. It automatically generates the appropriate operating curve whenever any changes in part material properties and forming geometries occur. The network maps non-linear relationships between part geometric variables and forming pressure throughout the punch stroke. The performance of the trained network was tested for various drawing ratios and punch shapes which had not been used for training. The results show that the proposed neural network approach yields products of uniform thickness, thus exhibiting the ability to design an operating pressure curve necessary for guaranteeing good product quality.
Diagnosis of Faults in the Fuel Injection System of a Forging Machine Using Fuzzy Sets Theory
Authors: Pham D T , Wu M H
Published: February 2007

This paper describes a diagnostic system for the fuel injection module in a high-speed forging machine. The system is based on the use of fuzzy sets techniques, with a fuzzy set representing each fault in the module. Empirical membership functions for the different fuzzy sets are employed to locate faults according to conditions observed on the forging machine. Two types of faults can be handled: faults due to one of more valves in the fuel injection module remaining in their unenergized state and faults caused by a valve being stuck in the energized state. Details of the diagnostic methods for both fault types are presented following a brief review of the operating principle of the forging machine.
Suboptimal Model Reduction by Multi-Point Padé Approximation
Authors: Lucas T N
Published: February 2007

A novel Padé approximation method is used to obtain a reduced-order transfer function, with a predetermined denominator, such that the integral square error between the time responses of the full and reduced models is minimized. The method is seen to be easy to apply compared with existing suboptimal order reduction methods. A numerical example is given to illustrate its application.
Real-Time Control Using Explicit Dynamic Solutions of a Two-Motion-Modes Mobile Robot
Authors: Cha Y Y , Gweon D G
Published: February 2007

In this study a two-motion-modes mobile robot is developed. The motion of the mobile robot is controlled by three d.c. servo-motors, two of which drive two wheels independently and one of which steers the wheels simultaneously. The two motion modes of the mobile robot, different velocity motion (DVM) and equal velocity motion (EVM), are analysed. Kinematic and dynamic analyses of the two motion modes are performed. For the implementation of real-time control considering mobile robot dynamics, the forward and inverse dynamic solutions are derived explicitly. Through a simulation, the path-tracking and control performance of the mobile robot considering dynamics is compared with the considering kinetics only, and the possibility of real-time dynamic control is proved.
The Behaviour of Lubricants in Contacts: Current Understanding and Future Possibilities
Authors: Spikes H A
Published: February 2007

The main role of a lubricant is to form a protective, low shear strength film between rubbing surfaces and thereby reduce friction and surface damage. The science, or art, of both the lubricant and the mechanical designer is to develop combinations of lubricant and mechanical system best able to form such films. This task is not straightforward since modern technology is continually demanding lower friction and better protection over an ever-widening range of operating conditions. Furthermore, environmental concerns are also producing both design constraints and the need for rapid change.

The aim of this paper is to show how progress is being made by experimental research which looks inside rubbing contacts to see how lubricants behave therein. The paper focuses on concentrated contacts, as found in gears, cams and rolling element bearings, and describes a number of techniques for probing such contacts to observe just how a range of lubricant types, from greases to emulsions, behave in such contacts to reduce friction and form films.
Elastohydrodynamic Lubrication of Soft-Layered Solids at Elliptical Contacts: Part 1: Elasticity Analysis
Authors: Yao J Q , Dowson D
Published: February 2007

In this two-part paper we consider the elastohydrodynamic lubrication (EHL) of soft-layered solids representing elliptical contacts. The problem has not previously attracted much attention, partly due to the lack of an effective numerical procedure to solve the coupled non-linear system of equations, but it is essential to the proper design of bearings with soft elastomeric liners and the full understanding of synovial joint lubrication.

In Part 1, the elasticity analysis for the surface deformation of a low elastic modulus layer on a hard-backing half-space under various forms of normal loadings is considered, by means of both the rigorous Hankel transform method and various simplifications. For layers of compressible materials (v ≤ 0.4), a generalized foundation model described by a second-order differential equation is proposed to represent the relationship between the surface deformation and the applied pressure. The empirical equation developed in this study is valid for a very wide range of the aspect ratio of the contact and provides an alternative way of modelling the elastic deformation without recourse to the often tedious integration in the numerical analysis of the EHL problem. The simplest form (constrained column model) of the equation, where the surface deformation is directly proportional to the local applied pressure, was found to be reasonably accurate for compressible thin layers (the aspect ratio 2b/ht ≥ 5 and Poisson's ratio v ≤ 0.4).
The Calculation of Residual Stresses in Worn Surfaces
Authors: Torrance A A
Published: February 2007

An elastoplastic model for calculating the residual stresses caused by the indentation of a semi-infinite solid by aflat punch is developed to allow calculation of the residual stresses left in a soft surface after it has been rubbed by a hard wedge. Despite the simplifications used, the model predicts to within 20 per cent the magnitude of the residual stresses produced by the gentle grinding of metals. It also predicts the essential features of the stress field and direction of crack propagation in some recent experiments on the sliding of steel wedges on aluminium.
The Effects of Geometric Irregularities of Journals on the Performance of Porous Bearings
Authors: Chennabasavan T S , Raman R
Published: February 2007

In the theoretical analysis of porous bearings the journal has so far been assumed to be ideal, that is perfectly cylindrical. In the present analysis the geometric irregularities of the journal, such as circumferential undulations and barrel/bellmouth shapes, are taken into account. The permeability variation along the length of the bearing as found in commercial bearings has also been taken into account. The present analysis reveals that, at the critical Sommerfeld number, the friction is very low compared to the very high value for an ideal journal. The present analysis also reveals that the friction and the attitude angle are lower for any Sommerfeld number and that the load-carrying capacity is lower for any eccentricity ratio than that for an ideal journal.
Determination of the Instantaneous Radius of Curvature of a Cam at the Contact Point with a Flat Follower Moving Orthogonally
Authors: Stone R , Leonard H J
Published: February 2007

A means of calculating the exact radius of curvature is derived for a cam in contact with a flat follower. A comparison is then made with a widely used approximate analysis.
Investigation of the Failure of Heavily Loaded Journal Bearings
Authors: Ashman D
Published: February 2007

This paper gives details of a combined theoretical and experimental investigation of a plain journal bearing under heavily loaded conditions together with a metrological study of the bearing geometry. It was found that under high loading conditions a simplified analytical expression relating the Sommerfeld number to the non-dimensional minimum film thickness, using a hydrodynamic solution of the isoviscous form of the Reynolds equation, could be developed. An alternative theoretical solution based on elastohydrodynamic lubrication was also considered. In addition, experimental work determined a variety of operating conditions that produced metal-to-metal contact. These operating conditions were then compared with the theoretical minimum film thickness calculations and bearing manufacturing data. This process was used to determine combined failure criteria based on operating conditions and machining capability.
Damping the Vibrations of a Rigid Shaft Supported by Ball Bearings by Means of External Elastomeric O-ring Dampers
Authors: Aktürk N , Gohar R
Published: February 2007

In this paper the radial and axial vibration behaviour of a rigid shaft supported by a pair of back-to-back angular contact ball bearings, mounted on elastomeric O-ring dampers, is studied. The use of elastomeric dampers for reducing the untoward effects of vibrations, due to unbalance of the shaft centre, is investigated. A computer program was developed to simulate such situations with the results presented in the form of frequency response curves and shaft centre orbits.

All results showed that elastomeric O-ring dampers can successfully be used for shaft-ball bearing systems as long as the dynamic characteristics of both the system and the elastomeric O-rings are known very well.
Measuring Lubricant Film Thickness with Image Analysis
Authors: Gustafsson L , Höglund E , Marklund O
Published: February 2007

Determining lubricant film thickness between contacting bodies under elastohydrodynamic (EHD) conditions is often simulated by using a ball/cylinder and transparent disc apparatus together with an interferometry technique. The simulated contact will have a point or elliptic shape and the light used can be white or monochromatic. The interference pattern is normally photographed with a regular camera or a video camera and the pictures are then evaluated by the naked eye of the observer. In most cases, only central or minimum thicknesses are evaluated.

In this paper an image processing method for the analysis of film thickness is presented. This method makes it possible to extract considerably more information about film thickness fluctuations than is achievable by the naked eye. The method primarily matches hue (but also saturation and intensity values) from digitized colour interferometric images of the unknown film shapes with calibration values obtained with known geometric shapes.

The method is shown to work well in the range from 95 up to 700 nm with white light and makes the results unbiased by the observer. Furthermore, absolute film thickness can be evaluated without prior knowledge about the fringe order in the interferogram.
Fluid Film Lubrication in Automobile Valve Trains
Authors: Taylor C M
Published: February 2007

It is nearly twenty years since the so-called energy crisis of the 1970s. This stimulated an increased awareness of the scarcity of natural resources and the necessity for their efficient and effective use. During the intervening period there has also been a mounting pressure from the ‘green’ lobby to recognize the fragility of the environment. The automobile is a significant factor world-wide with regard to both these aspects because of fuel consumption and exhaust considerations. These developments have led to intensive studies of the lubricated machine elements which are vital to the functioning of the internal combustion engine—the piston assembly, the bearings and the valve train. This paper will focus upon the valve train and in particular the fluid film lubrication of its most significant part, the cam and follower. The important role of lubricant additives, the formation of reaction films, boundary lubrication, contaminants and wear and failure mechanisms will not be addressed. In part the paper will review the background to the current position and understanding. However, attention will also be paid to a new study of a modern automobile engine valve train—that in the Ford Zeta engine. The research work described has revealed novel tribological understanding which will aid the design of future valve trains through technology transfer.
Bearings with Ceramic Balls—The Effect of Reduced Lubricant Supply on the Minimum Load
Authors: Gentle C R
Published: February 2007

Experiments have been carried out on a high-speed, precision, angular contact, thrust-loaded ball bearing, fitted with silicon nitride ceramic balls to determine the effect of reduced lubricant flowrate on the minimum load required to prevent gross skidding. The results showed similar behaviour to conventional steel bearings, with a significant reduction in minimum load as the lubricant supply is reduced, but the minimum load values were less in most cases for the ceramic balls.
A Simple Method of Elastic Contact Simulation
Authors: Snidle R W , Evans H P
Published: February 2007

The note describes an iterative algorithm for calculating contact pressure and areas of contact in nonconforming, two-dimensional, non-Hertzian contacts. In principle the method can be easily extended to three-dimensional problems.
The Optimum Pressure Ratio for a Combined Cycle Gas Turbine Plant
Authors: Horlock J H
Published: February 2007

A graphical method of calculating the performance of gas turbine cycles, developed by Hawthorne and Davis (1), is adapted to determine the pressure ratio of a combined cycle gas turbine (CCGT) plant which will give maximum overall efficiency. The results of this approximate analysis show that the optimum pressure ratio is less than that for maximum efficiency in the higher level (gas turbine) cycle but greater than that for maximum specific work in that cycle.

Introduction of reheat into the higher cycle increases the pressure ratio required for maximum overall efficiency.
Thermoeconomic Analysis of Gas Turbine Cogeneration Plant—a Case Study
Authors: Utgikar P S , Dubey S P , Rao P J Prasada
Published: February 2007

In a process plant where there is a simultaneous demand for power and process heat, cogeneration is an effective method of utilizing the fuel energy. In the present paper an energy and exergy analysis of a 20 MW gas turbine (GT) cogeneration topping cycle plant with supplementary fuel firing to meet the process heat requirements at full and half load operating conditions has been presented. The energy and exergy values at different locations of the plant are depicted in the form of Sankey and Grassmann diagrams. The plant performance has been evaluated on the basis of fuel utilization efficiency, power-heat ratio and second law efficiency. Technoeconomic aspects of the plant have also been estimated on the basis of the fuel-saving ratio and the pay-back period. The fuel-saving ratio for the full and half load conditions is found to be 0.35 and 0.25 respectively. Analysis shows that exergy losses in the combustion chamber of the GT and the heat recovery steam generator (HRSG) furnace are significant. Further, the pay-back period estimated at the full load operating condition is about 5 years.
Practical Difficulties in Raising Finance For Wind Farms
Authors: Johns J H
Published: February 2007

The 15 year term of NFFO3 will significantly alter the financial structures of wind farm projects. Senior debt terms will extend to 10–12 years and returns are unlikely to reach the levels required by venture capitalists. Returns to equity investors can be enhanced by debt and equity gearing techniques, for example the introduction of preference shares. Two investment schemes and an additional capital gains relief which were introduced in the November 1993 budget could benefit potential investors in wind farms
Biomass: An Environmentally Acceptable Fuel for the Future
Authors: Hall D O , House J
Published: February 2007

Biomass fuels currently supply around 15 per cent of the World's energy. Much of this is in the form of traditional fuelwood, plant residues and dung, which are often inefficiently used and can be environmentally detrimental. There is great potential for the modernization of biomass fuels to produce convenient energy carriers, such as electricity, gases and transportation fuels, while continuing to provide for traditional uses of biomass; this is already happening in many countries. When produced in an efficient and sustainable manner, biomass energy has numerous environmental and social benefits compared with fossil fuels. These include waste control, nutrient recycling, job creation, use of surplus agricultural land in industrialized countries, provision of modern energy carriers to rural communities of developing countries, improved land management, and a reduction of CO2 levels. Using biomass to substitute for fossil fuels is afar more effective use of available land than simply growing trees as a carbon store. Biomass fuels can form part of a matrix of renewable fuel sources that increases the energy available for economic development in developing countries. In OECD Europe it is calculated that a potential of 9.0–13.5 EJ could be produced in 2050 on available land, which represents 17–30 per cent of projected total energy requirements.
The Waste Handling System of the Waste Disposal Department of the City of Zurich (Abfuhrwesen Zurich)
Authors: Lemann M
Published: February 2007

This paper outlines the system used by the authorities in Zurich to treat and recycle waste in an environmentally acceptable way. The waste incineration system produces power and incorporates a district heating system as well as a wet gas-cleaning process.
Clean Coal Technologies
Authors: Moore M J
Published: February 2007

A seminar on ‘Clean coal technologies’ was held at the Institution of Mechanical Engineers in London on 13 June 1995.
Knowledge Elicitation and the Development of a Knowledge-Based System for Production Scheduling
Authors: Price G , Dunne F P E , Teoh K S , Walters D G
Published: February 2007

A prototype knowledge-based system for automated production scheduling has been developed for a press shop, which manufactures laminations for stator and rotor packs and cores for electric motor production. The system is PC (personal computer) based, user friendly, and may be interfaced to the existing computer-based MRP (material requirements planning) system, making the transfer of production data quick and easy. The knowledge-based system has been tested and validated over a range of production circumstances and the predicted production schedules show close agreement with those manually produced, over longer time-scales, by the human scheduler.

The knowledge elicitation procedures developed are described and, in particular, the use of a large flow diagram to describe the decision-making process during scheduling is discussed. The visual representation of the structure of the decision-making process is of particular benefit in aiding clarity of communication between the knowledge engineer and the domain expert. The techniques for knowledge acquisition within the production scheduling environment have been formalized and their use is advocated for use in the development of scheduling systems.

For the prototype system to be of practical benefit within the press shop, further development of the system is necessary to enable all the presses and lamination combinations to be scheduled. This is currently being carried out within the company.
The Nesting of Two-Dimensional Shapes Using Genetic Algorithms
Authors: Ismail H S , Hon K K B
Published: February 2007

The general two-dimensional cutting stock problem is concerned with the optimum layout and arrangement of two-dimensional shapes within the spatial constraints imposed by the cutting stock. The main objective is to maximize the utilization of the cutting stock material. This paper presents some of the results obtained from applying a combination of genetic algorithms and heuristic approaches to the nesting of dissimilar shapes. Genetic algorithms are stochastically based optimization approaches which mimic nature's evolutionary process in finding global optimal solutions in a large search space. The paper discusses the method by which the problem is defined and represented for analysis and introduces a number of new problem-specific genetic algorithm operators that aid in the rapid conversion to an optimum solution.