bluuebunny/crossref_metadata_2025 huggingface dataset:
The Comprehensive Design of Pumps, Water Turbines and Compressors
Authors: Anderson H H
Published: February 2007

Centrifugal pumps and compressors perform the same function of fluid transference; a boiler feed pump also operating as a turbo-compressor, when deprived of water, illustrates the design problems involved in each sphere of duty. Water turbines are reversed pumps. Pump design theory has in the past been unnecessarily complicated; in contrast, a simple system taking into account the combination of impeller and casing gives satisfactory results over the whole range of size, specific speed and characteristics. Flow passage geometry, with exact knowledge of the accelerations in three dimensions, is attained by the concept of the impeller with its flow surfaces generated as a gear wheel, improving efficiency and cavitation performance. Critical speeds and mechanical failure modes illustrate the relationship of pumps to turbo-compressors. Experience of 20000 pumps and 700 water turbines from 5 gallons to 5 million gal/min (of which a statistically significant number were tested on site by the user's staff and instruments on a ‘no tolerance penalty/bonus’ contract) resulted in efficiency bonus payments ranging up to 10 per cent of the contract price. Worldwide, for comparable numbers, higher efficiencies have not yet been published. Imperial units are occasionally used to help mental arithmetic and to illustrate historical data.
Calculation of the Material Interface in a Pressure-Wave Supercharger
Authors: Zhang H S , So R M C
Published: February 2007

The material interface inside a pressure-wave supercharger is determined by solving both the Euler and the Navier-Stokes governing equations, so that the effect of viscosity on the smearing of the interface can be evaluated. Two different numerical techniques are used to resolve the interface. One technique is a straightforward application of finite difference methods to solve the governing equations. Another is a combination of finite difference and coordinate splitting methods. The first technique leads to a material interface that is smeared over many grid celts. This is essentially a consequence of numerical diffusion and/or dispersion that results from truncation error. On the other hand, the combined finite difference and coordinate splitting technique uses a finite difference scheme to solve the governing equations everywhere, except in small regions surrounding the interfaces. In these regions, the governing equations are first transformed into two sets of one-dimensional Lagrangian equations where density does not appear explicitly in the spatial derivatives. As a result, the boundary conditions of the interface are automatically connected. Then the transformed equations are solved using conventional finite difference schemes. This technique gives a very accurate determination of the material interface. The results also show that viscosity does not contribute to the smearing of the interface.
Effusion Cooling: The Influence of the Number of Holes
Authors: Andrews G E , Asere A A , Gupta M L , Mkpadi M C
Published: February 2007

Experimental measurements of the overall cooling effectiveness for full-coverage discrete hole effusion cooling are presented for a wide range of practical geometries and for a density ratio between the coolant and combustion gases of 2.5. The influence of the number of holes per unit surface area was investigated at two fixed total hole areas or design pressure loss. These were a pressure loss of 3 and 0.1 per cent for a relatively low coolant flowrate per unit surface area. Hole configurations suitable for combustor wall cooling were investigated with hole sizes from 1.4 to 0.6 mm at 3 per cent design pressure loss and 1.3 to 3.3 mm at 0.1 per cent design pressure loss. Increasing the number of holes and increasing the hole diameter were shown to increase the cooling effectiveness through improved film cooling. Major reductions in current combustor wall cooling flows were demonstrated for some full-coverage effusion geometries.
Nucleation Phenomena in Flowing High-Pressure Steam Part 2: Theoretical Analysis
Authors: Bakhtar F , Zidi K
Published: February 2007

The paper is the second of a set and gives the theoretical part of an investigation into limiting supersaturation inflowing high-pressure steam. The treatment is one dimensional but includes refinements gradually developed in earlier studies; the complete final version is presented in summary form. Applications are to the authors' own experimental results and others available in the literature and the agreement with the measured pressure distributions is very good. The quality of agreement with the few measured droplet sizes is less good, the theory generally underestimating the observed mean droplet diameters. The summaries presented give variations of limiting supersaturation and resulting droplet sizes with the Wilson point pressure and the rate of expansion.
Management, Engineering and Innovation
Authors: Roberts R E J
Published: February 2007

The President reviews his career which started in aerospace research and continued in industry, eventually becoming Group Managing Director of GKN, then Chairman of Simon Engineering. He outlines the difficulties encountered during the United Kingdom recession in the early 1980s and how these problems were tackled. He gives his views on engineering innovation and the means by which it can be encouraged within a large company. He lists the factors that contribute to successful innovation and illustrates these by describing some specific products. He concludes by quoting some rules for innovation.
An Analysis of Electrochemical arc Machining
Authors: Ni X. , McGeough J A , Greated C A
Published: February 2007

The electrochemical arc machining (ECAM) process has been studied by high-speed photography over a wide range of conditions. The experimental results obtained have provided an unusual insight into the ECAM process, for which a theoretical analysis is proposed. The benefit of ECAM over electrochemical machining (ECM) or electrodischarge machining (EDM) is shown to be increased only if the rate of discharges in ECAM can be improved. Possible methods to enhance the discharges are discussed.
An Equivalent Chip Coefficient Towards an Adaptive Controlled Grinding Process
Authors: Younis M A
Published: February 2007

In this investigation the grinding process of the three grinding modes, external cylindrical, surface and internal cylindrical grinding, has been simulated over a wide range of input parameters. The analyses have led to the definition of a grinding coefficient, which is a collective combination of input parameters: work speed wheel speed vs and depth of cut. Grinding results of cutting forces, surface roughness and grinding ratio were represented in a grinding chart as logarithmic-linear functions of the grinding coefficient. Independent from the grinding mode a direct relationship was found between the output results and the grinding coefficient. Only one line is needed to describe the influence of all the input parameters on the output results (grinding forces, surface roughness and grinding ratio) independently from the grinding mode, thus eliminating the controversial effect of each of the individual input parameters (vs, vw and a) as well as the grinding model (surface, external and internal cylindrical grinding). The results are used to develop a grinding model for the cutting forces, grinding wheel wear and surface roughness. A design of an adaptive controlled grinding process is discussed.
A Front end Control Scheme for a Class of Second-Order Plants
Authors: Nagarajan R , Sajed K A
Published: February 2007

A class of controls, named as front end (FE) control, has been suggested recently. Its application in improving the quality of response of a pneumatically driven pick and place robot module has been experimentally investigated. However, a unified design approach for such FE control systems is yet to be formulated. This paper considers this problem and presents a design approach for an FE controlled second-order plant.
Dynamics of an Object Discharging off a Belt Conveyor
Authors: Yeo S H , Tadmory M J , Foster K , Hodgson D C
Published: February 2007

Belt conveyors are used extensively in the confectionery industry for transporting wrapped products between various phases of packaging such as flow-wrapping, collating and cartoning. A common way of changing the direction and orientation of travel of a single stream of wrapped units involves letting them discharge from the end of the conveyor and fall directly onto a second one set at 90° to the former. For controlled transfer, especially at high speed, the correct position and orientation of the unit on landing are important. The paper therefore sets out to analyse the dynamics of a prismatic, solid object discharging off a belt conveyor. The kinematic and dynamic equations which govern the motion of the object are first derived. Typical results from a computer program developed to predict the trajectories of rectangular objects for a given inclination and speed of the belt, and radius of the end roller are presented. The set-up of an experiment to verify the computer simulation is described and the comparison between analytical and experimental results is also discussed.
Experimental Measurements of Lubricant Film Thickness in Cold Strip Rolling
Authors: Sutcliffe M P F
Published: February 2007

This paper reports on experimental measurements of film thickness and area of contact ratio when cold rolling metal has been measured on an experimental mill. Where the film thickness is significantly greater than the roughness amplitude, measured film thicknesses are up to a factor of two less than the theory for smooth surfaces. That difference is attributed to the uneven lubrication conditions in the experiment. The small effect of this uneven lubrication on the theoretical film thickness is estimated where roughness is important. When this is taken into account, agreement between the film thickness measurements and a theory for lubrication in the mixed regime (see Sutcliffe and Johnson paper pp 249–261), is reasonable. The measured area of contact ratio is found to agree reasonably with the contact area ratio deduced from the measured film thickness and original roughness height distribution.
Automatic Modal Balancing of Flexible Rotors During Operation: Computer Controlled Balancing Head
Authors: Lee Chong-Won , Joh Young-Don , Kim Young-Dae
Published: February 2007

Modal balancing experiments are performed with a flexible rotor-bearing system by using a single wireless, computer controlled precision balancing head. The balancing head is activated by the command signals generated from a personal computer, so that the estimated modal unbalance is cancelled and rotor vibrations are kept relatively small as the rotor system passes through critical speeds. During operation of the rotor-bearing system, the vibrations measured by proximity probes are sampled into the computer and analysed to determine the modal unbalance of the rotor. The active control procedures which counterbalance the modal unbalance using the balancing head are described in this paper along with the theoretical background of the control system for the isotropic rotor-bearing system. Laboratory experiments show that the balancing head and computer control system designed is effective in modal balancing and reliable well over the first and second critical speeds.
The Digital Computation of Pressures in Hydraulic Pipes with Small Volume using an Iterative Technique
Authors: Bowns D E , Wang L M
Published: February 2007

This paper describes a mathematical stiffness problem encountered in the digital simulation of hydraulic pipe systems and an iterative technique that may be employed to avoid it. Mathematical stiffness often arises in systems where the compliance of one or more elements is much smaller than the compliance of the majority of elements in the system. In hydraulic systems, pipes are usually described by first-order differential equations, but if the pipe volume for one or more of the pipes is small, the simulation of this equation by digital computer techniques will necessitate the use of very small computer time steps and simulation times may be very long. However, under these conditions, pressure changes are usually very rapid, and for practical purposes can be considered to instantaneously follow the forcing function, that is, behave as though no compliance existed. A very similar set of circumstances arises in the simulation of orifices at start-up of flow or when flow is reversed. In this paper iterative models are proposed for such cases and their effectiveness is demonstrated in simulating two types of system.
Design Data for the Steadily Loaded Full Central Circumferential Grooved Plain Journal Bearing
Authors: Clayton G A , Taylor C M
Published: February 2007

Dynamically loaded journal bearings, such as those used in the internal combustion engine, frequently have lubricant supplied through a full or partial central circumferential groove. The use of circumferential grooves for oil supply with steadily loaded bearings is less common. It is, however, necessary to use such a feed arrangement if a plain bearing is required to operate for a range of steady state conditions, or slowly varying conditions, with the load vector in any direction. An example of such a situation would be a gearbox bearing. There has been uncertainty in relation to the design of central circumferential grooved journal bearings because of the influence of the feed pressure upon operating characteristics, particularly lubricant flowrate. The results of the analysis which are presented have been obtained with a consideration of film reformation to ensure satisfactory lubricant flow continuity. It is shown that the prediction of lubrication flowrate may be effected by a simple formula for the wide range of influential variables considered. The data which have been generated will be useful as the basis for a thermal analysis procedure.
Scuffing Failure of Steel Discs: Conditions for the Failure of Elastohydrodynamic Lubrication
Authors: Dyson A , Evans H P , Karami G , Paliwal M C , Snidle R W
Published: February 2007

Scuffing tests run on circumferentially finished discs were analysed to determine the conditions for the failure of elastohydrodynamic lubrication according to Dyson's theory. The critical lubricant temperatures and viscosities derived from this analysis were compared with the temperatures and viscosities at atmospheric pressure and at the bulk temperature of the discs, as recorded by thermocouples embedded below the surfaces. Tests and corresponding calculations were made for three different lubricating oils and for two steels. The results of the comparison between measured and calculated critical temperatures and viscosities support the concept of scuffing failure as being related to the physical failure of elastohydrodynamic lubrication, even though the lubricants differed significantly in their scuffing behaviour.
Some Aspects of the Micro-Elastohydrodynamic Lubrication of Rough Cylinders Finished with a Circumferential Lay
Authors: Baglin K P
Published: February 2007

Earlier work has shown that sinusoidal asperities with a circumferential lay give rise to transverse pressure ripples within the nominally smooth elastohydrodynamic pressure distribution. The ripples can become sufficiently large to cause elastic deformation of the generating asperities. This paper assumes that the deformed shape can be described using the Westergaard ‘dry contact’ analysis with the load (that, fraction of the total load contained within the pressure ripple) being unknown a priori. Solution of the Reynolds equation leads to the production of non-dimensional plots which give the extent of asperity deformation and the micro-elastohydrodynamic lubrication film thickness underneath the asperities as functions of the operating variables. It is shown that sensible lubricant films can exist between rough surfaces even as the nominal ratio of undeformed roughness/macro film thickness approaches 10. Different non-dimensional plots exist for different ‘sharpness’ asperities, defined as the ratio of amplitude/wavelength. For low values of the ratio, appropriate to roller bearings for example, Westergaard-type flat formation is appropriate over the total range of operating conditions considered. With sharper asperities, such as occur with W-N gears, the Westergaard flat is appropriate for relatively small deformations but, with increasing deformation, side lobes must form within the predicted ‘flat’. It is argued that this analysis will remain appropriate while the system is capable of producing high pressure in the valleys of the sinusoid but will become inappropriate as asperity deformation approaches the value it would have when bearing the total load.
Internally Pressurized Machined Domed Ends—a Comparison of the Plastic Buckling Predictions of the Deformation and Flow Theories
Authors: Galletly G D , Błachut J , Moreton D N
Published: February 2007

The present series of tests, involving six machined steel torispherical shells subjected to internal pressure, was designed to highlight the difference in the buckling predictions of the deformation and the flow theories of plasticity. For the geometries selected, deformation theory predicted that bifurcation buckling would occur for all the domes tested, whereas flow theory predicted buckling in only two of them.

In the tests, low-amplitude waves (detected by probes) appeared in all six of the domes. In four of the domes, the low-amplitude waves grew with increasing pressure and became buckles which were visible to the naked eye. Assuming that the occurrence of low-amplitude waves can be considered as buckling of a dome, then deformation theory predicted the failure mode correctly in all six cases. Flow theory was correct in only two cases.

The agreement between the initial experimental buckling pressures and those predicted by deformation theory was reasonably good, the ratios varying between 0.71 and 0.94. For three of the domes, the buckling pressures were also found by the Southwell plot technique. These latter agreed best with the deformation theory predictions.

The shell buckling program used for analysis purposes was BOSOR 5 and its predictions were checked using five other independent shell buckling programs. One reason for the incorrect prediction of the failure mode by flow theory may be the neglect of initial geometric imperfections in the analysis. Some preliminary calculations including them seem to confirm the hypothesis.
Determination of the Feedback Coefficients for the Constraint Violation Stabilization Method
Authors: Kim J K , Chung I S , Lee B H
Published: February 2007

A constraint violation stabilization method has been used to solve a mixed set of algebraic and differential equations formulated for the dynamic analysis of a constrained mechanical system. However, the absence of a clear-cut method for determining the feedback coefficients associated with this method makes it unattractive and unreliable for its user. This paper presents a method for determining the optimal feedback coefficients which minimize the propagation of constraint violation. This method is based on the stability analysis for the error propagation dynamics of the modified constrained equation containing the feedback coefficients, which is discretized by the Runge-Kutta method in discrete time domain. Two examples show that the proposed method is effective and easily applicable to general non-linear dynamic systems.
An Optimized Magnet-Coil Force Actuator and Its Application to Precision Elastic Mechanisms
Authors: Smith S T , Chetwynd D G
Published: February 2007

Sprung translation mechanisms driven by electromagnetic force actuators are often used to produce controllable motions. This paper is concerned with one family of such devices incorporating linear spring mechanisms suitable for short-range, high-precision applications. In these, a permanent magnet is attached to the movable translating stage which is, in turn, surrounded by a solenoid coil attached to a fixed datum. Design considerations are discussed, principally an optimum dimensional design for a uniformly wound circular cylindrical coil. Design models are verified by the construction of a simple device in steel and aluminium which demonstrates an open-loop positional accuracy of better than 0.5 per cent over a displacement range of 100 nm to 50 μm.
Linearized Squeeze-Film Dynamics: Model Structure and the Interpretation of Experimentally Derived Parameters
Authors: Burrows C R , Kucuk N C , Sahinkaya M N , Stanway R
Published: February 2007

In this paper the authors address the problem of parameter estimation in linearized models of squeeze-film dampers. After demonstrating how the choice of an unsuitable model structure can lead to the misinterpretation of experimentally derived coefficients, a technique is described for assessing the significance of individual inertia, damping and stiffness effects associated with the squeeze-film. An experimental study involving a squeeze-film vibration isolator is described. It is shown how the technique allows the model structure to be simplified in a systematic way.
Numerical Analysis of Two-Phase Flow in Gas-Stirred Reactors
Authors: Ferng Y M , Chieng C C , Pan C
Published: February 2007

Using the multi-dimensional, turbulent, two-phase flow model, the fluid flow phenomena for gas injecting through a submerged lance in gas-stirred reactors are investigated numerically by a finite difference algorithm. The present numerical model is validated by comparison with the experimental data of the water model and extended to predict the flow fields and mixing phenomena inside the liquid metal model. This study indicates that the flow characteristics and mixing behaviour of the water model are similar to the metal model and the experimental data of the water model can be an important reference for the design of liquid metal reactors. The investigations consist of central (two-dimensional) and off-centred gas injection (three-dimensional) with full—and fractional—depth of lance submergence and with different gas injection rates.
Measuring Vehicle Drag Forces Using an On-Board Microcomputer
Authors: Passmore M A , Jenkins E G
Published: February 2007

The force resisting the straight-line motion of a road vehicle on a flat track consists of mechanical resistance and aerodynamic drag. It is necessary to measure these component forces over the speed range of the vehicle to obtain data for performance calculations and for the accurate calibration of modern chassis dynamometers used in fuel economy and exhaust emission tests.

Continuous measurement of wheel torque, vehicle speed, airspeed and direction enables estimates to be made of the various drag forces that bring the vehicle to rest during a coastdown test. The data are analysed using a sophisticated parameter optimization routine to determine the numerical values of the coefficients in a mathematical model of the total road load. Repeatability of the results are assessed by calculating the uncertainties in the values obtained from a number of track tests. A brief description of the on-vehicle data acquisition and processing system is given, and the advantages of an advanced test and analytical process are demonstrated.
The Implications of Technical Developments on Future European Braking Regulations
Authors: Oppenheimer P
Published: February 2007

Road vehicle braking systems provide a good example of the increasing use of electronics in vehicles (for example, anti-lock braking systems) and the trend towards the adoption of new technologies (for example, brake-by-wire, electric braking, diagnostics, multiplexing, radar/automatic braking).

This paper examines the implications of these developments for future vehicle regulations, including the rule-making process and compliance testing.

The present European ECE and EEC braking standards are summarized and the progress towards ‘harmonization’ with the US Federal Standards is reported.

The advent of electronic anti-lock braking systems has been anticipated within Annexes to the European regulations; however, a more detailed examination of the potential electronic system opportunities for failure warning and diagnostics is currently in progress.

Product liability, failure mode and effects analysis and electromagnetic compatibility are major subjects for consideration in future vehicle regulations; a radical new approach to traffic safety legislation may be opportune.
Investigations on Research Engines with Visible and Infrared Optical Access
Authors: Hands T , Collings N , Ma T
Published: February 2007

This paper details the progress made in an experimental study of knock in spark ignition engines undertaken between the Cambridge University Engineering Department and Ford Research and Engineering Centre.

A general-purpose, optically accessed cylinder head of standard configuration and capable of high-speed operation has been designed and built. This head has been used in preliminary direct emission studies of knock.

The same cylinder head, together with a photographic Ricardo Hydra, has been used in an infrared study of cylinder radiative emissions. By maximizing the combustion chamber surface emissions, observations regarding surface temperature characteristics with and without knock have been made.

By minimizing the emissions from combustion chamber surfaces, the strong emission from the flame from itself has been used to produce once-per-cycle images of flame propagation.
A New Technique for Steady State Flow Force Compensation in Spool Valves
Authors: Weixiang Shi , Songnian Li , Sihua Ge
Published: February 2007

In improving the performance of some hydraulic systems a significant factor is the compensation of the steady state flow force in spool valves. This paper presents a new method, or configuration, to reduce the steady state flow force in spool valves and gives the results of theoretical analyses and experimental research which indicate that the new configuration can remove 56–69 per cent of the steady state flow force in spool valves. The configuration is so simple and economical to manufacture that it only needs a simple annular groove to be machined on the spool.
A Design Guide for the Refractory Linings of Vessel and Transfer Lines
Authors: Richards P K
Published: February 2007

The paper is concerned with the design of refractories where there are significant pressure and temperature loadings on the structure. The factors that affect the performance of linings are discussed, including the properties of the material as manufactured. Design methods are proposed which enable a suitable lining and pressure vessel combination to be determined for those cases where direct experience is not available. Examples are given to illustrate the design methods.
Fibre Spinning: An Optimal Control Problem
Authors: Goh C J , Phan-Thien N
Published: February 2007

This paper presents the analysis of a non-isothermal fibre-spinning process pertinent in some polymer industries. By formulating the problem as an optimal control problem, it is shown that by adjusting the ambient temperature and the draw ratio, any reasonable smooth fibre profile can be obtained. The numerical solutions to the optimal control problem are found to depend on a dimensionless heat-transfer coefficient. An effective optimal solution requires this coefficient to be at least 2.
The Improvement of Plant Maintainability Through Design
Authors: Thompson G
Published: February 2007

The paper considers methods by which professional engineering designers can beneficially influence plant maintainability. It is proposed that maintainability be treated as a design variable and incorporated into analysis procedures. Design analysis methods are described, based on value theory, by which quantitative assessments may be made using subjective value judgements. Design management practice has a significant influence on the eventual maintainability of plant. Maintainability requirements need to be understood and sufficient time provided to solve problems during the design phase. Specifically, the paper discusses design review methodology, design contractual agreements incorporating maintainability clauses and quality assurance. Good plant maintainability cannot be achieved without an imaginative approach and careful attention to detail during product design. General principles are given and illustrated by a process valve design study with respect to maintainability. Other examples are cited.
Modified Atmosphere Packaging: The Flexible Machine System
Authors: Hastings M J
Published: February 2007

This paper examines methods of extending the edible quality of food products by modified atmosphere packaging. Also discussed are developments giving improvements in product handling flexibility, output, reliability and hygiene.
Time Present and Time Past
Authors: Pollard M G
Published: February 2007

The Railway Division Chairman recalls his early interest in aeronautical engineering and then goes on to review his career in British Railways, giving details of some of the projects with which he has been involved. He discusses the role of development and the importance of building and testing prototypes, and outlines some successful long-term developments in the aircraft and railway industries. He then describes some current developments taking place in British Railways which will have important implications for the future. These include a.c. traction systems, noise reduction, strategies to reduce energy consumption, health monitoring and diagnostics of railway systems, non-destructive testing and crashworthiness.
Push—Pull Trains for Iarnrod Eireann — Irish Rail
Authors: Grainger R P
Published: February 2007

This paper describes how Iarnrod Eireann modernized its mainline fleet by the introduction of new passenger rolling stock incorporating push–pull vehicles. This necessitated the development of a control car design using existing manufacturing techniques.
The Mechanisms for Lubricant Failure in Reciprocating and Rotary Vane/Screw Air Compressors
Authors: Matthews P H D , Grisdale J , Walkden R H
Published: February 2007

The prediction of the behaviour of a lubricant for reciprocating and rotary air compressors is of paramount importance in enabling the selection of the correct lubricant for a trouble-free operation. Reasons for premature failures are discussed and suggestions for overcoming these problems are put forward.
The Design and Development of a Brake Disc for High-Speed Trains
Authors: Russell D F , Williams A J
Published: February 2007

This paper describes the demands placed on disc brakes by the modern generation of high-speed passenger trains, in particular the TGV of the French Railways (SNCF), and outlines how a new design of solid steel brake disc was developed in response to these demands. Modern engineering design and development methods such as CAD (computer aided design), FEA (finite element analysis) and large scale computer-controlled test rigs were used to refine initial design proposals to achieve a design which was substantially ‘right first time’. Prototype equipment was delivered to the customer on time for vehicle trials in the passenger-carrying service, and discs of the production design are now being supplied for use on the TGV.
The Effects of Particulate Contamination in Rolling Bearings—a State of the Art Review
Authors: Sayles R S , Hamer J C , Ioannides E
Published: February 2007

The role played by particulate contamination in rolling contacts has formed the subject of much research in recent years. Bearing-steel quality has improved to a level where the long established sub-surface-inclusion based fatigue failures are being replaced by surface or near-surface initiated failures caused by surface defects resulting mainly from rolled-in debris particles. The paper reviews the reasons and mechanisms involved, and shows how particle material, size, concentration and hardness can all have effects on bearing reliability.
Fast Response Tip Clearance Measurements in Axial Flow Compressors—Techniques and Results
Authors: Parrish C J
Published: February 2007

As part of an investigation of the effects of tip clearance performance of development axial flow compressors, a system for detecting rotor blade tip rubs has been developed and a tip clearance measuring system modified to detect clearance changes at a bandwidth of 500 Hz.

Mean clearance changes have been measured as well as changes during surge. Rotor orbit has also been investigated and the system has become an important means of monitoring rotordynamic behaviour. Subharmonic components of rotor orbit have been discovered.
The Fatigue Performance of Notched Composite Material Systems
Authors: Kellas S , Morton J , Curtis P T
Published: February 2007

In this work results are reported from an experimental fatigue programme. The role of the constituent materials upon the fatigue performance of a given composite material system was studied. This involved comparisons of the residual strength, damage development, and in some cases fatigue life. A new method of approach, based upon a unique characteristic fatigue parameter, termed the damage transition stress, St, was also introduced. It has been shown that the employment of the characteristic parameter can simplify the comparison of different material systems considerably.

Four graphite reinforced material systems were evaluated: (a) standard epoxy system, (b) toughened epoxy system, (c) thermoplastic system and, (d) high temperature system. It was found that three of the four material systems examined (a, b, and d) were more sensitive to hygrothermal environments, so far as the development of fatigue damage is concerned. In general, the tensile residual strength, in all material systems, showed a marked improvement, whereas the effect of environment and fatigue damage combination upon the compressive strength was more complex.

Presentation of the fatigue data in the form of linear S-N plots allowed the determination of St, and its dependence upon environment and material systems. A material dynamic toughness was also identified.
Future Fastening Systems for Aerospace Structures
Authors: Roach T A
Published: February 2007

Advanced aerospace programs have created a need for mechanical fastening which requires the development and application of new materials, processes and technologies. Some of these are already in place, but others will evolve as the needs are further defined by the structural designers. Some of these fastening systems are described herein.
Blood Flow: Insights from Ultrasound
Authors: Wells P N T
Published: February 2007

Ultrasonic pulse-echo systems can provide range-finding, time-position and real-time two-dimensional images of soft-tissue structures within the body. The Doppler effect can be used to study motion and blood flow. Continuous wave Doppler instruments provide information about velocity and direction of flow; depth discrimination can be obtained by pulsing the ultrasound. Two-dimensional Doppler flow imaging can be achieved by manual scanning of a probe over the skin surface. The combination of real-time pulse-echo imaging with pulsed Doppler blood flow detection in the duplex scanner makes it possible to localize the anatomical position of the Doppler sample volume. Real-time Doppler colour flow imaging combines traditional ultrasonic scanning with a two-dimensional flow map. Using appropriate ultrasonic instruments, blood flow volume rates, blood flow velocity profiles, pressure gradients, orifice areas, flow disturbances, jets, characteristics of blood vessels and the circulatory system, and tissue perfusion can all be investigated. These investigations have clinical applications in the study of cardiac, cerebral and peripheral blood flow, blood flow in the female pelvis, the fetus, the abdomen, the neonate, and in malignant tumours. Contemporary ultrasonic diagnosis employs exposure levels that are apparently free from biological risk, but other factors need be taken into account in considering the prudent use of ultrasonic methods. Promising research is being carried out into the mechanism of ultrasonic scattering by blood, Doppler speckle, time-domain processing for blood flow imaging, methods for increasing the scanning speed, Doppler flow microscopy and contrast agents. The new technology that will result from this research should lead to further substantial progress in ultrasonic blood flow studies.
Objective Measurement of Knee Laxity and Stiffness with Reference to Knee Injury Diagnosis: Part 1: Design Considerations and Apparatus
Authors: Dahlkvist N J , Seedhom B B
Published: February 2007

Apparatus capable of objectively evaluating the laxity of the knee in vivo has been developed. The equipment consisted of a microcomputer-controlled machine, into which the leg was firmly clamped. The mechanical properties of the knee were measured by slowly applying a load to the tibia, while the femur was held stationary, and monitoring the resulting displacement of the tibia.

Three separate tests could be performed: anterior-posterior drawing, varus-valgus rotation and tibial rotation. The tests were carried out on both legs of each subject, making six tests in all. The forces versus displacement (or torque versus rotation) took the form of a hysteresis loop. From these a total of 24 variables describing the stiffness, laxity and visco-elastic properties of the knee were calculated.
Objective Measurement of Knee Laxity and Stiffness with Reference to Knee Injury Diagnosis: Part 2: Results
Authors: Dahlkvist N J , Seedhom B B
Published: February 2007

Equipment capable of objective knee analysis has been used to obtain data from 85 ‘normal’ healthy knees, 47 patients suffering with knee disorders, and three cadaveric knee joints. Among the ‘normals’ it was found that there was a correlation between body weight and stiffness and laxity. A lower stiffness and higher laxity was recorded at 20y° of knee flexion than at 90°. Using relative-paired diffrence analysis the variables affected by different injuries in patients were identified and are presented. In a separate analysis a multi-variate technique is used to interpret the data. The technique could be used to predict or diagnose knee injury, and as such may be highly useful to clinicians.
A Comparative Study of the Shear Stress Induced in the Leakage Backflow Produced by Four Types of Heart Valve Prostheses
Authors: Haggag Y A M
Published: February 2007

The clinical selection of a prosthetic heart valve requires the consideration of many factors. These include the pressure drop across the prosthesis, the amount of leakage backflow when the valve is closed as well as the associated shear stress within this flow for a particular valve design. Major emphasis has been placed upon the documentation of the pressure drop across prosthetic valves. Consideration of the shear stress induced in the leakage backflow associated with prosthetic valves, however, has received less attention. The purpose of this investigation, therefore, is to determine theoretically the extent of this particular shear stress for four types of currently used mechanical prosthetic cardiac valves. All valves have the same tissue annulus diameter of27 mm.

The leakage backflow is relatively small compared to the main forward flow through the orifice. However, it is important from the haemolysis point of view. The effect of the shear stress on the suspected occurrence of haemolysis is analysed by two theoretical approaches: (a) the laminar flow approach, and (b) the entry flow approach, and then compared with the findings of previous investigators dealing with the critical shear stresses which may damage the red blood cells.

It was found that both approaches give practically equal shear stresses under the same pressure differential for all valves investigated. Some haemolysis is expected to occur but it is generally compensated by bone marrow hyperfunction, since that type of shear stress is sustained for only a short duration of time.
A Simple Instrument for the Measurement of Maximum Occlusal Force in Human Dentition
Authors: Blamphin C N J , Brafield T R , Jobbins B , Fisher J , Watson C J , Redfern E J
Published: February 2007

A simple instrument for the measurement of maximum occlusal force has been developed and the results of an initial clinical trial have been reported. The maximum occlusal force in subjects with dentures was significantly lower than in a group of young male subjects with natural dentition. In the young males the bite force between the molars and premolars was significantly greater than between the incisors. The maximum bite force was not dependent on position for subjects with dentures.
Axisymmetric Mechanical Analysis of Ceramic Heads for Total Hip Replacement
Authors: Andrisano A O , Dragoni E , Strozzi A
Published: February 2007

An axisymmetric, mechanical analysis of conical press-fit ceramic heads is performed. The head strength and its fracture modes are assessed experimentally. The stress field is examined by finite element, strain gauge and photoelastic methods. An alternative head design, characterized by a cylindrical engagement with the stem, is analysed with the same techniques and its merits are explored.
A Simple Procedure for Determining Spatial and Transient Variations of Cooling Rate within a Specimen during Cryopreservation: Part 1: Analysis
Authors: Diller K R
Published: February 2007

The cryopreservation of biological materials may involve cooling continuously in the liquid state (as in vitrification) or nucleation of ice, followed by thermal equilibration at a selected sub-zero temperature and subsequent cooling in the solid phase. Both of these processes may be approximated by a single-phase heat transport analysis, the most critical parameter of which, for biological survival, is the cooling rate. The Fourier series solution for the cooling rate in a specimen is presented for single-phase heat transfer in cartesian, cylindrical and spherical coordinates: extensive tables of the series constants and of the roots of the transcendental equations have been computed that include the cases of most relevance to cryopreservation. In particular, data are provided to calculate the cooling rate at process states close to the initial conditions, that is at small Fourier numbers. Graphical results of the analysis are given in Part 2.
A Simple Procedure for Determining Spatial and Transient Variations of Cooling Rate within a Specimen during Cryopreservation: Part 2: Graphical Solutions
Authors: Diller K R
Published: February 2007

The ability to analyse the cooling rate history and its spatial distribution is useful in predicting the response of a biological specimen to a specific cryopreservation protocol. Although analytical and numerical methods exist for performing rigorous analyses of these thermal processes, their practical use requires considerable time and/or mathematical sophistication. In Part I of this paper a theoretical basis was presented for the development of a graphical analysis procedure for determining cooling rate that is quick and straightforward to apply.

In this paper derived graphs are presented, from which the instantaneous cooling rate may be determined for specimens of a wide range of physical shapes. These dimensionless graphs have been derived for determination of cooling rate as a function of time, position, the system's physical properties and the thermal boundary conditions. Numerical examples are presented for analysing the cooling of biological specimens for specific preservation protocols, illustrating solution both by computation using the tabulated constants from tables in the first paper and by reading directly from the graphed solutions.
Effect of Tube Ovalling on Pressure Wave Propagation Speed
Authors: Anderson Eur Ing A , Johnson G R
Published: February 2007

For physiological and other flows it is often assumed that the pressure pulse wave speed is given by the classic Moens-Korteweg expression and this may be used, for example, to assist in the determination of in vivo blood vessel wall incremental Young's modulus. A number of physical factors affecting the value of this wave speed have been reviewed in the literature, but the effect of slight ovalling of the tube cross-section is rarely mentioned.

The analysis for a tube of elliptic cross-section shows that even a very small degree of ovalling can cause quite substantial reductions in Young mode wave propagation velocities compared with the classic Moens-Korteweg expression. Bending-induced changes in cross-section shape with internal pressure increase the apparent elasticity of the tube wall.

Experimental confirmation is provided by waterhammer wave speed measurements in a copper tube that has been ovalled by coiling. Even though the Young mode is not dominant in this case, as it would be for a physiological case, the measured wave speed is quite clearly less than the Moens-Korteweg theory and it can be shown that the small degree of measured tube ovality explains this.
Applying Tribological Principles to Improve the Performance of the Hoffmann External Fixator'S Universal Joint
Authors: Drijber F L I P , Finlay Eur Ing J B
Published: February 2007

As part of a continuing investigation of sources of slippage in the universal joints of external fixation devices, a study was conducted to determine if selected interfaces of the Hoffmann external fixator (rod/clip torsional, cheek/bowl and clip/cheek) could be improved by moving the point of contact between the wing-nut clamp and cheek closer to the centre of the wing-nut clamp. It was felt that the movement of the point of contact would reduce the magnitude of the frictional torque resisting the tightening of the wing-nut clamp. The point of contact was changed by the addition of a Belleville washer between the interface of the wing-nut clamp and the cheek. Increased slippage torques of approximately 100 per cent were noted in all interfaces at low values of tightening torque (6 and 8 N m) of the wing-nut clamp and improvements of not less than 50 per cent were obtained at higher tightening torques (10 and 12 N m) on the wing-nut clamp.
An Undergraduate Introductory Course on Computational Fluid Dynamics
Authors: Potts I , Anderson A
Published: February 2007

Introducing computational fluid dynamics (CFD) into undergraduate teaching of fluid mechanics is easily justified by the recent explosion in general access to high-quality commercial software. However, the ready availability of powerful CFD software also has its dangers from a pedagogical viewpoint if students are simply encouraged to tackle real problems without understanding the validity and limitations of these tools. The objectives of the Newcastle approach are to emphasize the underlying physical and mathematical concepts which will underpin CFD as commercial software continues to develop in the future. This emphasis has had a significant (and possibly controversial) impact on the choices adopted for applications, solution methods and teaching techniques, including the use of software. Inevitably the sheer breadth and multi-disciplinary nature of the subject means that great selectivity has had to be applied to topics addressed in a general-purpose undergraduate course.
Thermofluid Mechanics: A Computer Integrated Teaching Approach
Authors: Fraser C J
Published: February 2007

With the reduced class contact hours associated with many Bachelor of Engineering undergraduate courses and the continually broadening applications of computer technology, a new philosophical approach is required in the teaching of thermofluid mechanics. In this paper, thermofluid mechanics is considered as an element of engineering design and the means of a computer-based integration within a composite course structure is addressed.
Developments in Marine Propellers
Authors: Patience G
Published: February 2007

This paper outlines and discusses the development of marine propellers, with particular reference to large fixed-pitch propellers for merchant ships, in response to the challenges of economic and environmental factors that have emerged within the last two decades.