bluuebunny/crossref_metadata_2025 huggingface dataset:
Robotic-Assisted Internal Fixation of Femoral Fractures
Authors: Bouazza-Marouf K , Browbank I , Hewit J R
Published: February 2007

Closed surgical techniques for the internal fixation of femoral fractures require orthopaedic surgeons to work in close proximity to X-rays. In addition to the occupational health risk this imposes, inexperienced surgeons often encounter great difficulty in achieving optimal positioning of fracture repair fixtures. A vision-guided robotic system has been proposed as a possible solution to these problems and an initial investigation involving two exemplar orthopaedic procedures has been undertaken Robotic surgery assistance imposes rigorous safety-related design constraints, since the orthopaedic robot must operate in close proximity to the patient and operating staff. The design and implementation of a purpose-built robotic system for orthopaedic surgery assistance is described in this paper.
Cushion form Bearings for Total Knee Joint Replacement Part 1: Design, Friction and Lubrication
Authors: Auger D D , Dowson D , Fisher J
Published: February 2007

Cushion knee prostheses have been designed and constructed that produce approximately equal initial contact areas and theoretical film thicknesses compared with a conventional UHMWPE (ultra-high molecular weight polyethylene) joint. These compliant bearings had a flat tibial component which imposed fewer biomechanical constraints and allowed a greater range of movement. Friction experiments have been carried out on a pendulum simulator apparatus. The results showed that the cushion knee joints operated just within the mixed lubrication regime, but that they benefited from a substantial measure of fluid film lubrication. Microelastohydrodynamic lubrication was effective in preserving low friction and thin but effective lubricating films.
Comparative Analysis of Bone Stresses and Strains in the Intoss dental Implant with and without a Flexible Internal Post
Authors: Clift S E , Fisher J , Edwards B N
Published: February 2007

The clinical success of any dental implant is dependent upon the maintenance of good-quality bone supporting it. Previous studies have shown high values of strain around the neck of an implant under lateral loading. These high values may lead to fatigue damage and resorption in lower strength cancellous bone. In this study, the finite element method has been used to study the bone strain distribution around the following implants: (a) an Intoss dental implant, referred to as the ‘standard’ implant; (b) a comparative Branemark implant and (c) a modified Intoss implant with a central flexible post, referred to as the ‘modified’ implant.

Three different bone distributions have been investigated under axial and lateral loading: (a) implant surrounded by cortical bone; (b) implant tip supported by cortical bone with a thin layer of cancellous bone along the length and top of the implant; (c) implant tip and top supported by cortical bone with a thin layer of cancellous bone along the remaining length.

For the standard implant, similar maximum equivalent strain values were predicted for the bone surrounding a comparable length Branemark-type implant. Modification of the standard implant design to include a flexible central post resulted in a decrease in the maximum von Mises stresses and equivalent strains in the cancellous bone. It is postulated that this will reduce the likelihood of bone fatigue failure and subsequent resorption in this bone. Thus the proposed design change is predicted to be highly beneficial in terms of bone load transfer.
The Influence of Joints and Soft Tissue on the Natural Frequency of the Human Tibia Using the Impulse Response Method
Authors: Tsuchikane A , Nakatsuchi Y , Nomura A
Published: February 2007

The influences of the joints adjacent to the human tibia, the surrounding soft tissue and the fibula on the vibrational parameters of the tibia (that is natural frequency, mode shape and damping ratio) are in need of clarification. Using five cadaveric human legs, the resonant frequency and damping ratio were measured with an accelerometer placed on the medial tibial condyle while the medial malleolus was impacted by an impulse hammer. The legs were subsequently dissected and the measurements were made in six conditions. The mode shape was obtained by use of modal analysis. Hammer impacts were given at 15 points along the three surfaces of the tibia, while an accelerometer was attached to the surface of the medial malleolus. Resonant frequencies ranged from 275 to 405 Hz in the intact specimens and successively increased with removal of the skin, muscles and foot, and then decreased with the removal of the femur and the fibula. Damping ratios successively decreased. The transitional pattern of natural frequencies was similar to that of the resonant frequencies. The mode shape represented the first bending mode and it corresponded to the condition of the tibia in which the proximal and distal ends of the bone were free.
A Biological Basis for Instantaneous Centres of Rotation of the Vertebral Column
Authors: Bogduk N , Amevo B , Pearcy M
Published: February 2007

The instantaneous centre of rotation has proven to be a useful parameter of vertebral motion. The normal location of instantaneous centres has been determined in cadavers and in normal volunteers for the cervical, thoracic and lumbar spines, and abnormal location of centres has been shown to correlate with spinal pain. However, to date, an instantaneous centre has constituted no more than a convenient mathematical summary of vertebral kinematics. It has defied resolution into biologically meaningful parameters. This study offers a novel model of vertebral motion in which the instantaneous centre of rotation can be shown to be a function of the location of the centre of reaction of a vertebra, and the intrinsic rotation and translation it undergoes. These parameters are strictly linked by equations that determine the location of an axis of rotation. These equations allow aberrations in the location of an axis to be interpreted in terms of the anatomical and pathological factors that affect the centre of reaction of the vertebra and the rotation and translation it undergoes.
Modelling of a Flexible Arm Using System Identification and Model Reduction
Authors: Fujimori A , Nikiforuk P N , Koda E
Published: February 2007

This paper presents a new experimental method for modelling of a single (one)-link flexible arm in which the system identification and model reduction are combined. A linear model of the flexible arm is first derived by least-squares estimation. After identifying a model whose order is sufficiently high, the model is reduced by balanced realization. The obtained eighth-order models can represent the characteristics of the flexible arm below 100 Hz. Compared with modelling using modal analysis, the method presented does not need additional experimental equipment, such as an impact hammer or fast Fourier transform analyser, for obtaining data. The validity of the obtained models is confirmed by vibration control experiments using optimal control synthesis.
Constrained Suboptimal Padé Model Reduction
Authors: Lucas T N
Published: February 2007

An extension of a recent Podé suboptimal model reduction method is presented which ensures that the initial time response values of the reduced models coincide with those for the full system for impulse or step inputs. This desirable property is seen to involve little extra computation and can be implemented on existing computer algebra packages. An example is given to illustrate its use.
The Use of Multi-Objective Parallel Genetic Algorithms to Aid Fluid Power System Design
Authors: Donne M S , Tilley D G , Richards W
Published: February 2007

This paper describes the use of parallel genetic algorithms to automate the component sizing stage of the design process. Experiences of applying the method to fluid power systems are discussed and problems encountered are highlighted. Refinements to the standard parallel genetic algorithm for use as a single objective optimizer and its adaptation for use as a method to locate Pareto optimal solutions of multi-objective optimization problems are described. The multi-objective algorithm is used to optimize a mathematical problem and two fluid power circuits.
Generalized Finite Difference Methods for Optimal Estimation of Derivatives in Real-Time Control Problems
Authors: Harrison A J L , Stoten D P
Published: February 2007

The real-time estimation of (particularly first and second) derivatives of motion from position data has many applications in automatic control. Errors in such estimates at high sampling rates arise from noise or quantization of the data and from the presence of high-order derivatives of motion at low rates.

This paper presents a generalized method to allow estimation of derivatives of orbitary order from position data, with minimum overall error, for a given signal-to-noise ratio and sampling-to-signal frequency ratio. Experimental results included in the paper show that the theory is borne out in practice.
A Mechatronic Approach to Compact Fluid Disc Valve Design
Authors: Parker G A , Sun Y B
Published: February 2007

The work presented in this paper deals mainly with a mechatronic approach to compact disc valve design and concentrates on improvements to the disc valve electromagnetic characteristics, the diaphragm design and the dynamic performance. A novel diaphragm-disc force motor has been successfully developed incorporating a pair of permanent ring magnets. It has the advantages of low electric power consumption at the null position, dual-lane electrical structure for fail-safe operation, high control accuracy and should be competitive with existing torque motors due to its low cost and simple construction. The research involved designing and testing a prototype disc pilot valve with a dual-lane operating mode. The test results showed that the valve has satisfactory static and dynamic characteristics for industrial applications.
Decentralized Adaptive Control of a Directly Driven Hydraulic Manipulator: Part 1: Theory
Authors: Edge K A , de Almeida F Gomes
Published: February 2007

A new approach to adaptive control of manipulators is presented in this paper. The proposed controller for each individual axis is of the model reference type, designed through the use of variable structure systems theory. A novel feature of the controller is the introduction of a series-parallel model of the model-following error. The use of this model ensures system stability even if the manipulator design parameters or payload bounds are exceeded. Chattering of the system, associated with variable structure systems, is eliminated by arranging for the control objective to be physically achievable.
Application and Implementation of LQ Design Method for the Velocity Control of Hydrostatic Transmissions
Authors: Lennevi J , Palmberg J-O
Published: February 2007

Hydrostatic transmissions are inherently low damped and stiff systems which are increasingly used for the power transmission in vehicle drivetrains. For the velocity control of hydrostatic transmissions the regulator must contribute to the damping of the system. A non-linear and a linearized model of the system are presented. LQG design is applied and the obtained regulator is implemented in different ways. The implementations are compared and discussed with respect to their merits and drawbacks. Results for evaluation and validation are obtained by means of simulation of a non-linear model and experiments in a test rig.
An Optical Study Of Grease Rheology in an Elastohydrodynamic Point Contact Under Fully Flooded and Starvation Conditions
Authors: Williamson B P
Published: February 2007

An interferometric study of grease rheology in a fully flooded and deliberately starved elastohydrodynamic (EHD) point contact has been carried out under isothermal conditions at 30 °C and various rolling speeeds up to 1 m/s for a viscous liquid lubricant and greases made with lithium, calcium and polyurea thickeners. The measured grease film thickness (GFT) is always greater than that generated by their base oils under fully flooded conditions. The enhanced GFT generated by the lithium and calcium thickened greases can be described by Newtonian flow behaviour using an effective grease viscosity. The results are consistent with the thickener for these greases being fully degraded in passage through the EHD inlet region. The polyurea grease exhibited non-Newtonian fluid flow behaviour (shear thinning) and gave the greatest GFT enhancement (over that exhibited by the base oil). A model to predict the degree of grease starvation in a rolling EHD contact is proposed which is based on determining the inlet meniscus position. Comparison of the results predicted by this model with experiment indicate that the heavily worked grease in the contact inlet exhibits Newtonian behaviour under constant speed conditions. This suggests that the role of the degraded thickener is to increase the effective viscosity of the grease base oil.
A Generalized Computational Fluid Dynamics Approach for Journal Bearing Performance Prediction
Authors: Tucker P G , Keogh P S
Published: February 2007

The use of computational fluid dynamics (CFD) techniques enables performance predictions of bearing designs to be made when the usual operating assumptions of the Reynolds equation Jail to hold. This paper addresses the application of a full three-dimensional thermohydrodynamic CFD approach to journal bearings. The journal/shaft may extend beyond the bearing length and the rotation effect is accounted for in the thermal transport process. A circumferentially uniform shaft surface temperature is not assumed. Cavitation modelling is based on averaged lubricant/vapour properties and does not set pressures directly, allowing sub-ambient pressures to be predicted. Lubricant inlet grooves are incorporated with conservation of mass and the possibility of backflow. The modelling is validated against published experimental work on fully circumferential, single inlet and two-inlet circular bore bearings. The predicted and experimental results are in general agreement, although the predicted cyclic variation of journal surface temperature is less than the experimental value. However, an assumption in the predictions was of a non-orbiting journal. The techniques developed may, in principle, be extended to the orbiting journal case providing a dynamic cavitation model can be formulated.
Characterization of the Ring Pack Lubricant and its Environment
Authors: Burnett P J , Bull B , Wetton R J
Published: February 2007

The performance characteristics of the piston ring-liner assembly and the lubricant within it are critical for the operation of modern internal combustion engines. The ring pack can directly affect engine friction, oil consumption and oil degradation, which in turn can impact upon fuel economy, emissions and engine wear. The operation of this system is complex and no single technique is capable of fully characterizing the processes occurring. This paper outlines the range of both experimental and theoretical methods that are being applied to the study of this system and the lubricant within it. These include the modelling of ring pack gas and oil flows, and direct measurement of piston temperatures, ring belt pressures and piston ring motion. Characterization of lubricant degradation via direct sampling of oil from the top ring groove of an operating engine has also been used. The merits of such a multi-faceted approach are discussed in relation to piston deposit formation.
Debris and Roughness in Machine Element Contacts: Some Current and Future Engineering Implications
Authors: Sayles R S
Published: February 2007

The influence of surface roughness and third-body particulates on tribological contacts will be reviewed in general, but in particular their influence on rolling contacts and contacts where rolling and sliding occur simultaneously will be considered in some detail. Such non-conforming contacts are often referred to as Hertzian, and when lubricated are often considered to be protected by an elastohydrodynamic (EHD) lubricant film. Transferring these concepts to the loaded interfaces of real engineering components such as gears, rolling bearings, constant-velocity joints and cams, etc., can have serious shortcomings and lead engineers to many misconceptions. Roughness often appears to dominate over the theoretical size of lubricant films and can create a contact geometry and local stress distribution far removed from the smooth surface case. Even in ball-bearings where surfaces are some of the smoothest of all mass-produced engineering components, lubricant-borne debris particles are usually many times the theoretical film thickness and the damage they can cause can quickly destroy the production engineer's good work in creating smoothness, as well as having a significant influence on component performance.

The paper reviews such aspects in terms of recent research and explains some of the many practical implications of roughness and debris that are faced at present, and also speculates on the implications for the future, when roughness geometry and surface properties might be engineered to suit a particular lubricant and its potential contaminant population.
The Hydrodynamic Phase of Gearbox Synchromesh Operation
Authors: Paffoni B , Progri R , Blouët J , Gras R
Published: February 2007

The approach used is to divide the synchronization process into three distinct stages according to the friction regime operating, this idea being closely allied to that of A. E. Anderson (1972, SAE paper 750521). The authors proceed to derive a model for the first stage based on a shaft-ring pair with or without taper defects (angular mismatch). Expressions are derived for contact pressure (and hence axial force), output torque and the coefficient of friction, the latter pair being arrived at by considering the shear stresses acting at the cone surface. The results that are gained allow best and worst cases of torque and friction to be considered and the effect of circumferential grooves and axial slots to be theoretically examined, and the potential for this model in simulating such configurations is discussed.

The main conclusion of the paper is that the coefficient of friction clearly decreases during the first stage such that the value during the second stage may be quite small (results of the analyses of the second and third stages are promised for the future), but it is now relatively simple to estimate this with acceptable accuracy.
Simulated Non-Newtonian Lubricant Behaviour under Extreme Conditions
Authors: Chynoweth S , Coy R C , Michopoulos Y
Published: February 2007

Equilibrium and non-equilibrium molecular dynamics techniques are used to simulate a molecular liquid (n-hexadecane) at extreme physical conditions (high temperatures, pressures and shear rates), typical of those encountered in many elastohydrodynamic lubrication applications, and to study the effects of pressure and temperature on the calculated theological properties. Pressure and temperature effects are found to be more pronounced at low shear rates than at high shear rates, where the non-Newtonian behaviour is dominated by the strong external kinematic effects. The observed non-Newtonian behaviour of the pressure and temperature coefficients of viscosity and the variation of certain molecular geometric functions calculated to assist the microscopic understanding are combined to provide a possible explanation for the phenomenon of limiting shear stress under elastohydrodynamic lubrication conditions. Further implications for the behaviour of lubricant-like molecules in practical applications are also discussed.
Steady Load-Carrying Capacity of Recessed Hydrodynamic Bearings
Authors: Goodwin M J , Ogrodnik P J , Roach M P , Lim L K , Fang Y
Published: February 2007

Oil-film hydrodynamic bearings are one of the most common forms of bearing used in rotating machinery. Because of their effect on system unbalance response and stability, care has to be exercised in the design of machines running in hydrodynamic bearings—for example they cannot usually be used in machines operating at high rotational speeds when the steady load on the bearing is low. A novel form of hydrodynamic bearing which incorporates recesses in the bearing surface has been proposed by the authors which improves the dynamic characteristics; however, earlier work has not fully assessed the steady load characteristics of such bearings vis-à-vis conventional bearings for example. The aim of this paper is to present the results of experimental work on several designs of the proposed novel bearings, to assess the bearing's performance and to compare it with that of conventional bearings. The results of the work show that the steady load-carrying capacity is adversely affected by the inclusion of recesses in the bearing surface, but that this is only a marginal effect provided that the number of recesses and their geometry are selected with care.
Study of Static Fluid Forces in a Squeeze Film Damper with a Circumferential Groove
Authors: Zhang J X
Published: February 2007

Approximate expressions are obtained for static fluid pressure and force for a centrally grooved squeeze film damper (SFD) resting at an equilibrium position without vibration. The analysis shows that, to some extent, grooved SFDs may share some characteristics with hydrostatic bearings, due to the existence of the lubricant supply pressure. Thus static fluid force and hence oil stiffness may exist in SFDs, in addition to the conventional inertial and damping coefficients for SFDs. This paper is solely focused on the static fluid forces and oil stiffness generated in an SFD with a finite length groove. Flow continuity is used at the centre of the groove, which takes into account the effects of the inlet oil flowrate and oil supply pressure. This use of flow continuity differs substantially from the traditional use of constant pressure in the central groove, and it provides better results. At the interface between the groove and the thin film land, a step bearing model with ignored fluid inertia is employed. It is verified by both the theory and previous experiments that the static fluid force and stiffness are linearly proportional to both the lubricant supply pressure and the eccentricity ratio of the SFD journal.
Some Aspects of the Outline Design Specification of a 0.5 kW Stirling Engine for Domestic Scale Co-Generation
Authors: Rix D H
Published: February 2007

This paper describes the design considerations that were involved in the production of a prototype Stirling engine, primarily intended for use in a domestic scale combined heat and power (CHP) system. These are discussed in terms of the specification of basic design parameters—configuration, working fluid, etc. First the particular requirements of this application are considered, primarily a power output of 1 kW or less, suitability for high-volume mass production, ultra long life and as high an efficiency as possible. The design that emerges is relatively simple, of low specific power output and with rather conservative operating parameters—temperature, pressure and speed.
A Theoretical Study of the Performance of an Axial Flow Turbine for a Microhydro Installation
Authors: Parker G J
Published: February 2007

The Bernoulli-with-loss equation, with the losses represented by a constant times the velocity head, has been applied to each section of the flow through a small turbine system consisting of inlet guide vanes, axial flow turbine and draft tube. Using experimental data and the sets of equations, the flow angles around the turbine blades and the loss coefficients in the turbine and in the draft tube were determined. These were used to predict the effect of varying the guide vane angle and the turbine blade angle on performance. They were also used to predict the effects on the performance of a geometrically similar prototype system.
Investigations on Preheated Palm Oil Methyl Esters in the Diesel Engine
Authors: Masjuki H , Abdulmuin M Z , Sii H S
Published: February 2007

The major drawback of vegetable oil fuels is their high viscosity. Various conventional approaches to reducing the viscosity of vegetable oils are studied theoretically and experimentally. An attempt to reduce the viscosity of the palm oil methyl esters (POME) by preheating the fuel was performed and a comparison on the basis of its projected chance of leading to ‘diesel-like’ combustion was also carried out with conventional diesel fuel. It was observed that by preheating the POME fuel above the conventional temperature, the engine performance, especially the brake power output and the exhaust emissions characteristics, is improved significantly, approaching diesellike' performance. This is mainly attributed to the fact that as the fuel is preheated the viscosity is reduced close to ordinary diesel (OD) fuel. This will result in improved spray and atomization characteristics. Torque, brake power, specific fuel consumption, exhaust emissions and brake thermal efficiencies were measured and calculated. The potential for improved engine performance and reduction in emissions levels was demonstrated.
Simplified Analyses of Some Vapour Power Cycles
Authors: Horlock J H
Published: February 2007

A range of vapour power cycles is analysed, using the assumption originally made by Schaff that along a turbine expansion line the difference between the (local) enthalpy (h) and the liquid enthalpy at the same pressure ( hL) may remain unchanged (β = h – hL is constant). The thermodynamics of the assumption are critically examined and it is found to be valid only over strictly limited ranges of properties (usually low-pressure levels). However, if such limitations are accepted, the analyses provide understanding of the effects of various key parameters on thermal efficiency, and of measures (such as feed heating, reheat, dual pressure boilers, etc.) that are taken to raise that efficiency.
Study of the Steam Turbine Trip in a 20 MW Geothermal Plant
Authors: Bidini G , Desideri U , Sabbatini F
Published: February 2007

In vapour-dominated geothermal sources a large amount of non-condensable gas is mixed with the steam and requires extraction from the condenser, generally by means of a compressor. A plant has been studied in which this compressor is directly coupled, via gearboxes, to the steam turbine shaft. When a ‘trip’ occurs (and this may often happen when considerable load variations cause a small plant to get out of synchronism), very high torque readings have been measured at the turbine–compressor coupling. This paper presents a computer simulation which has been developed for the system to explore ways of reducing these high torques.
An Investigation of Face Type Magnetic Couplers
Authors: Waring R , Hall J , Pullen K , Etemad M R
Published: February 2007

A theoretical analysis of magnetic couplers is recounted, leading to the design and manufacture of prototype disc type magnetic couplers. Design and development of experimental test rigs are also given. Test results are presented and compared with theoretical calculations. This shows very good agreement. The exception to the rule was the case of axial load measurements, which were not accurately evaluated by the computations. The geometries tested here showed the optimum design to consist of rotors with eight poles, magnet thickness of 10 mm and a filling factor of about 0.7.
Dynamic Model of a Wind-Driven Lift Pump
Authors: Burton J D , Davies D G
Published: February 2007

This paper examines the dynamics of one of the oldest pieces of equipment known to mankind, the simple lift pump. These continue to be used in remote areas of the world for lifting water by hand or using wind power. In the case of the smaller modern wind-powered water pumps the speed of operation is such that dynamic factors need to be taken into account when designing the pump. The paper explores the value of introducing softness and elasticity into either the lift rod or the riser support. Output from models describing the pump dynamics are compared with experimental data.
Regulating Pollution: Alara, Batneec and Beyond
Authors: Robson A
Published: February 2007

Pollution regulation in the United Kingdom has developed over many years, with different agencies developing different approaches to protect air, water and land. Furthermore, regulation of the nuclear industry developed separately from other industries. In the 1990s an era of Integrated Pollution Control began. The aim is to unify the way pollution is regulated by building on concepts like the reduction of radiation exposure to levels of As Low As Reasonably Achievable (ALARA) and the prevention of conventional pollution via the Best Available Techniques Not Entailing Excessive Cost (BATNEEC). Regulatory methodologies suffer from difficulties inherent in dealing with a mixture of health, economic, environmental and social factors. Guidance on how this should be undertaken has developed over time, but is still far from being clear and unambiguous in some key areas. This paper reviews the background to concepts like ALARA and BATNEEC, and discusses the optimization of impacts across more than one medium to achieve the Best Practicable Environmental Option (BPEO). The paper looks beyond current procedures by discussing the problems associated with their application to developing issues.
Aerodynamic Performance of Contra-Rotating Wells Turbine for Wave Energy Conversion
Authors: Raghunathan S , Beattie W C
Published: February 2007

A contra-rotating Wells turbine as an alternative to a biplane Wells turbine for wave energy conversion is investigated. The aerodynamic analysis and control of such a turbine are presented. It is shown that for a given pressure amplitude a contra-rotating Wells turbine is aerodynamically more efficient and can operate over a wider range of flowrates when compared to a biplane Wells turbine.
Design and Performance Prediction of Centrifugal Impellers
Authors: Wang Y , Komori S , Xu Z
Published: February 2007

This study presents a simple method for designing the blade geometry of a centrifugal compressor impeller. In this method, instead of giving the mean swirl distribution on the meridional surface, the blade angle distribution is specified and the blade shape is derived, making it easier to perform the design. The quasi-three-dimensional potential flow field inside the impeller is obtained using the streamline curvature method, which solves the Euler equation along arbitrary quasi-orthogonals. The viscous effect is incorporated indirectly into the inverse design of the impeller via the simplified three-dimensional boundary layer calculation and the performance prediction. A three-dimensional centrifugal impeller was designed using this inviscid-viscous method and eventually manufactured. The newly designed impeller (B) and another impeller (A) designed previously were tested on a standard apparatus for model impellers. With the aid of three-hole probes and thermocouples, the flow parameters downstream of the exit of the impellers were measured along the axial direction of the impellers. A viscous loss model related to the boundary parameters is developed and used for the performance predictions of the impellers together with other loss models. From both the boundary layer analysis and the performance prediction, it is concluded that impeller B is superior to impeller A, which is in close accordance with the measurements.
Numerical Investigation of an Improved Gas and Steam Turbine Seal
Authors: Gordon M H , Kelkar U M , Johnson M C
Published: February 2007

A numerical study has been conducted to assess the viability of a new sealing mechanism for gas and steam turbines. This new static-to-rotating sealing mechanism is mounted on flexible legs which permit radial movement and is designed to take advantage of the hydro-dynamic pressure forces, which result from fluid leaking around the seal, to maintain an ideally small and constant clearance. Relatively simple seal geometries have been numerically tested to find an optimal shape. These results indicate that a substantial sealing improvement (between two and four times less leakage) relative to a labyrinth seal is possible. Although these results show that a brush seal is more effective than the present seal, the present seal is designed to operate in high-speed and high-temperature environments in which the brush seal would degrade.
Synergistic Neural Models of a Robot Sensor for Part Orientation Detection
Authors: Pham D T , Sagiroglu S
Published: February 2007

This paper describes the use of neural networks to compute the orientation of a part from the output signals of an inertial sensor which is a device for determining the location of parts by measuring their inertial parameters. The paper investigates an approach for increasing the accuracy of the computed orientation. This involves employing a group of neural networks and combining their outputs. The paper presents the results obtained for several neural network combinations. These show that the accuracy achieved in a combined system is higher than that of its individual components provided the number of components is not too large.
A Study on Parameter Optimization for Circumferential Gas Tungsten Arc (GTA) Welding of Small Pipes considering Backing Gas Pressure: Part 2: Process Optimization
Authors: Na S-J , Lho T-J
Published: February 2007

Extensive use of circumferential gas tungsten arc (GTA) welding in industrial applications has been handicapped due to the difficulty of choosing the optimal process parameters. In Part 2 of this study, the welding current and backing gas pressure are optimized by calculating the three-dimensional transient temperature distribution and the surface profile of the resultant weld pool in circumferential GTA welding of small-diameter pipes, in order to obtain a uniform weld bead without any hang-down over the entire circumference of pipes.
Adaptive and Compensation Methods in Free-Form Surface Assessment
Authors: Ip W L R , Loftus M
Published: February 2007

The assessment of manufactured surfaces by coordinate metrology techniques has changed in recent years. Speed, accuracy and flexibility have all improved with the introduction of coordinate measuring machines (CMM). However, some technical problems have yet to be solved, in particular those pertaining to free-form surfaces. This paper considers the influence of surface features and probe tip geometry on the assessment of free-form surfaces. Inaccurate measurements due to the problems of probe tip diameter and undulating surface curvature have been investigated, and a simple mathematical compensation technique for different probe diameters and an adaptive measuring point planning strategy have been developed. Experimental data confirm that the measuring errors are significantly reduced when the probe tip diameter compensation approach is used.

The problems of machined surface measurement have also been considered and a method, namely least-squares data fitting, is proposed to give a better qualifying technique for the cusped surfaces. This new technique has been implemented and the results from the case study indicate that the least-squares method can give a more precise representation of the quality of a machined surface than standard statistical measurement systems. Experimentation also indicates that the results of the least-squares data fitting method are consistent with the CMM computed values, which verifies the reliability of the method.
Recent Progress of Computer Aided Simulation of Chip Flow and Tool Damage in Metal Machining
Authors: Maekawa K , Shirakashi T , Obikawa T
Published: February 2007

A computer simulation approach to the predictions of chip flow and tool damage in metal machining is reviewed based on the authors' recent work. Not only finite element simulation theory but also material characteristics to be included in the analysis are stressed, since machining phenomena are intimately associated with elastic-plastic deformation and fracture of work materials at high strain rates and high temperatures. Temperature rise in the tool and workpiece should be incorporated in the machining simulation as well. Various simulation results together with some comparisons with experiments are shown, such as two-dimensional continuous and discontinuous chip formation, wear and fracture of a cutting tool and more practical three-dimensional machining. Finally, a new concept of computational machining or virtual machining simulation is envisaged in the light of further development of the present computer aided simulation.
The Matrix of Confusion—a Classification of Robot Movement
Authors: Morley E C , Wilson J R
Published: February 2007

The human-machine interface for robots has received only limited attention as robots have developed. Most research has focused on the design of teach pendants, hand-held devices for programming and manual motion control. Results from these studies have been generally inconclusive as to the best control design for teach pendants.

In a fresh approach to the area, the human-robot interface has been analysed. This has resulted in the development of a method of classifying robot movements called the ‘matrix of confusion’. The classification shows the robot motions an operator would see when using a given control for a unique combination of operator position, robot position, programming mode and robot configuration.

The use of the matrix has helped to highlight the most important factors in the task of manual motion control of the robot. This has helped in the development of a new motion system for a PUMA robot which is currently being tested in comparative trials.
A Sensing Technique for the Measurement of Tactile Forces in the Gripping of Dough-Like Materials
Authors: Stone R S W , Brett P N
Published: February 2007

This paper describes a tactile sensing technique that is devised for applications concerned with the control of the active gripping of deformable compact shaped non-rigid materials. The sensor uses measurements of thin aluminium plate deformation to determine a close representation of the force distribution applied to the surface of the workpiece and can be used to indicate deformation and slip of soft materials under the action of gripping forces.

Two methods of operation are described along with the results of each of these implementations. The first method utilizes a model of the sensor mechanical structure to interpret the sensory data from the deformed shape created by the applied force of the object on the sensor surface. The second method relies on an algorithm for comparing theoretical and measured bending moments to achieve the force distribution that provides close agreement between these two entities. In this case the theoretical moment is adjusted by manipulation of the parameters used in the expression describing the force distribution.
Towards a Comparative Study of Quarter-Turn Pneumatic Valve Actuators
Authors: French M , Ramìrez A C
Published: February 2007

Comparative design studies are potentially a valuable source of design knowledge, surveying as they do the work of many designers in many companies and incorporating the judgement of the market-place. Quarter-turn pneumatic valve actuators are a good product to study, as they are small and self-contained and used in large numbers, and there are many makers (many more even than were expected).

Experimental tests were made on nineteen designs. Criteria for comparison were found, and applied, measuring efficiency, matching and compactness. Some explanation of the diversity of designs was found in niches in the market, for example for different valve types and applications. Historical trends have generally been to greater refinement. Some function costs are given. The industry has shown serious interest in this work.
Analysis of Grinding Temperatures by Energy Partitioning
Authors: Rowe W B , Black S C E , Mills B , Qi H S
Published: February 2007

The partitioning of heat between two sliding bodies depends strongly on the relative magnitude of the thermal characteristics of each body. Grinding with the superabrasive CBN (cubic boron nitride) gives the favourable condition of a high thermal conductivity wheel, allowing increased heat to be carried away by the grinding wheel. This reduces the temperatures experienced by the workpiece. In this paper different methods of theoretical partitioning in grinding are reviewed. The partition ratio is the proportion of the total grinding energy that enters the workpiece. The partition ratio in surface grinding was measured using a thermocouple technique. Theoretical models for predicting the partition ratio were correlated with measured results to establish the effective thermal properties of CBN and aluminium oxide abrasives. The effective thermal conductivity of CBN was found to be considerably lower than the reported theoretical value. The findings provide the basis for improved prediction of workpiece temperatures in grinding.
Thermal Investigation of a Honing Process Utilizing Polyborosiloxane Impregnated with Abrasive Particles
Authors: Fioravanti A , Fletcher A J
Published: February 2007

A novel honing and polishing process utilizes polyborosiloxane impregnated with a range of abrasives in particulate form, to polish mould cavities of complex geometry. The polymer, which deforms in such a way as to allow complete coverage of the target surface, is used to carry the abrasive. This compound is agitated using an ultrasonic source and is made to flow relative to the target surface.

The process causes heating of the various components in the system. This is the second paper concerned with the prediction of the resultant temperature distributions. The work reported here is an extension of the previous work to take into account the complex geometry of the multi-component system used in the operation. Furthermore, the development of the honing process required the introduction of flow of polishing compound relative to the workpiece. As a result the previous work has been extended to take into account the thermal effects of this flow.

The modelling work has been complemented by measurement of temperatures in a geometry that is representative of the processing requirements. The calculated and measured results have been compared and the model validated accordingly.
Three-Dimensional Flow Measurements in Conical and Straight Wall Centrifugal Compressor Vaneless Diffusers
Authors: Pinarbasi A , Johnson M W
Published: February 2007

In the current work three-dimensional flow measurements in two types of centrifugal compressor vaneless diffuser were obtained using hot wire anemometry. The first diffuser was conical, designed to give a constant flow area, while the second straight wall diffuser had a constant axial width. Measurements of mean velocity, flow angle and velocity fluctuation level were obtained on eight cross-sectional planes in each diffuser.

The jet-wake flow pattern and the impeller blade wakes are clearly visible at the inlet of both diffusers. Mixing out of the blade wake proceeds more rapidly in the straight diffuser. The hub boundary layer also develops more rapidly in this diffuser because of the adverse pressure gradient. Velocity fluctuation level measurements highlight the mixing regions within the diffusers.

Recommendations are also made for the design of vaned diffusers. A larger vaneless space would be required with a straight wall diffuser and significant twisting of the vane would be required for both diffuser geometries if significant incidence losses are to be avoided.
Jet Mixing in a Model Direct Injection Diesel Engine with Swirl
Authors: Petersen U , MacGregor S A
Published: February 2007

Computational and experimental results are reported of an investigation into jet mixing, using the hydraulic analogue technique to simulate the diesel injection process. Steady state and impulsive injections into both quiescent and swirling flow fields are considered. A comparison between predictions and experimental results shows a deficiency in the turbulence model's capability to predict recirculation zones downstream of the point of injection. The relative effect of swirl on jet penetration is examined and it is argued that a non-uniform injection characteristic leads to a more rapid formation of a combustible mixture, thereby reducing the ignition delay period and the pressure gradient during combustion.
Uncertainty in Computational Fluid Dynamics
Authors: Fisher E H , Rhodes N
Published: February 2007

The Annual EPSRC/IMechE Expert Meeting brought together some 44 experts to consider sources of uncertainty in computational fluid dynamics (CFD). Presentations and discussions covered modelling, numerical solution techniques, boundary conditions, evaluation protocols and QA (quality assurance) procedures. The principal conclusions to emerge were: (a) the need for additional collaborative validation studies; (b) the desirability of introducing appropriate QA procedures, possibly based on the CFD Community Club initiative; (c) the need for additional postgraduate training, possibly based on the IGDS principle; (d) the value of continuing work in modelling and error estimation techniques for numerical schemes.
Hybrid Fuzzy Logic Algorithm for Position Control of Pneumatic Actuator With 3/2-Way Solenoid Valves
Authors: Wang H , Mo J P T , Chen N
Published: February 2007

Pneumatic positioning devices are inexpensive and also have the advantages of high speed and cleanliness. However, due to the non-linearity of the working medium, pneumatic actuators are not commonly used in industry for programmable positioning applications. Recent researches in this area are mainly concentrated on using expensive servo valves as the control element. However, the systems generally have the problems of instability and load sensitivity. In this paper, a pneumatic cylinder is controlled by a series of low-cost two-state solenoid valves. The components in the system are taken from commercial stock items that do not have the tight tolerance demanded by traditional control methodologies. The inaccuracies of the components are compensated by a hybrid fuzzy logic algorithm which incorporates additional fuzzy pulse width modulation and small deviation control logics to achieve high accuracy and repeatability at all stroke positions.
Analysis of a Four-Bar Mechanism with a Radially Compliant Clearance Joint
Authors: Seneviratne L D , Earles S W E , Fenner D N
Published: February 2007

Clearance joints in high-speed mechanisms can suffer from contact loss, leading to noise generation and joint deterioration. To predict the onset of contact loss detailed modelling of the joint is required. In this paper a clearance joint is modelled using a combined massless link and spring-damper unit, where the bearing stiffness (spring element) is estimated from a three-dimensional finite element analysis. The combined model is shown to exhibit chaotic behaviour just prior to contact loss and the predictions correlate well with experimental results. The bearing stiffness and damping are shown to have a significant effect on the behaviour of the joint, including the occurrence of chaos and the extent of contact loss regions.
Cross-Flow Heat Transfer in The Freeboard Region of a Fluidized Bed
Authors: Murray D B , O'Connor P , Gilroy P
Published: February 2007

This paper describes an experimental investigation of heat transfer in two tube banks, one in-line and one staggered, located in the freeboard region of a gas fluidized bed. The objectives of this study are twofold. Firstly, examination of the local heat transfer results is used to identify the dominant heat transfer mechanisms. Secondly, the overall heat transfer performance of the two tube configurations is of relevance for the design, selection and siting of heat exchangers for fluidized bed combustors. The experimental results show that the dominant influence on heat transfer is the local concentration of particles, with the impact over the rear of tubes by particles disengaging from the flow having a significant effect on wake heat transfer. The latter mechanism is less important for tubes in the first and second rows of the in-line array, due to the shielding effect of the surrounding tubes. This difference in wake heat transfer contributes to higher mean Nusselt numbers, on average, for the tubes located in the staggered array.