bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress and Strain Distribution in the Bone Surrounding a New Design of Dental Implant: A Comparison with a Threaded Branemark Type Implant
Authors: Clift S E , Fisher J , Watson C J
Published: February 2007

The stress and strain distributions in the bone surrounding a new dental implant, designed specifically for use with a bioactive porous coating and thus having a fully bonded interface to the bone, have been analysed. The new implant geometry was slightly tapered, with deep concentric grooves to allow bone ingrowth and load transfer, and had a parallel cylindrical section at the neck. The results have been compared with stress and strain predictions in the bone surrounding a ‘Branemark type’ threaded implant with a fully bonded interface. Under axial loading both implant types produced similar stress and strain distributions with a higher level of stress in the cortical bone surrounding the neck of the implant. Under lateral loading a high stress concentration was found in the neck region of both implants, but this was lower around the neck of the new design compared with the threaded implant. When the new implant was surrounded by cancellous bone, the reduction in the stress concentration was up to 50 per cent. This reduction should help to reduce fatigue failure and bone resorption in this area under lateral loading.
An Analytical Examination of Muscle Force Estimations Using Optimization Techniques
Authors: Challis J H , Kerwin D G
Published: February 2007

Muscle forces are often estimated during human movement using optimization procedures. The optimization procedures involve the minimization of an objective function relating to the muscle forces. In this study 15 different objective functions were evaluated by examining the analytical solutions to the objective functions and by comparing their force predictions with the forces estimated using a validated muscle model. The muscle forces estimated by the objective functions were shown to give poor correspondence with the muscle model predicted muscle forces. The objective function estimates were criticized for not taking sufficient account of the physiological properties of the muscles. As a consequence of the analysis of the objective functions an alternative, simpler function was presented with which to estimate muscle forces in vivo. This function required that to satisfy a given joint moment, the force exerted by each of the muscles divided by the maximum force possible by the muscle was constant for all muscles. For this function the maximum muscle force was determined using a muscle model assuming maximal activation.
Rotation of the Tibia in the Normal and Ligament-Deficient Knee. A study Using Biplanar Photography
Authors: Matsumoto H , Seedhom B B
Published: February 2007

The difference between physiological tibial rotation and rotatory instability of the knee, particularly the ‘pivot shift’ phenomenon, was investigated by analysing knee movements under both rotatory and valgus torques using 29 fresh cadaveric knees. The knee movements were measured in three dimensions using biplanar photography, when all ligaments were intact, and then after the ligaments were sequentially sectioned. The axis of the physiological tibial rotation was shown to be located about the centre of the tibial plateaux, while that of the pivot shift is located about the medial collateral ligament (MCL). When the anterior cruciate ligament (ACL) was sectioned, little or no significant change in physiological tibial rotation was observed under rotary torques, while a significant rotatory instability, including the ‘pivot shift’ phenomenon, was observed under a valgus torque. It was thus concluded that the rotatory instability is not simply an increase in the magnitude of the physiological rotation of the tibia, but is an abnormal tibial rotation which occurs with a different mechanism.
An Instrumented Glove for Monitoring MCP Joint Motion
Authors: Rand D T , Nicol A C
Published: February 2007

A lycra glove has been instrumented with novel low-profile electrogoniometers to measure index and middle finger metacarpophalangeal (MCP) flexion/extension motion. It is lightweight and comfortable to wear, enabling portable, unobtrusive measurement of joint usage about the home or work environment. Preliminary results have shown it to be of comparable accuracy to existing clinical measurements. Many applications are envisaged in the fields of ergonomics, orthopaedics and rehabilitation.
Estimation of Weld Pool Sizes in GMA Welding Process Using Neural Networks
Authors: Lim T G , Cho H S
Published: February 2007

In gas metal arc (GMA) welding processes, the geometrical shape and size of the weld pool are utilized to assess the integrity of the weld quality. Monitoring of these geometrical parameters for on-line process control as well as for on-line quality evaluation, however, is an extremely difficult problem. The paper describes the design of a neural network estimator to estimate weld pool sizes for on-line use in quality monitoring and control. The neural network estimator is designed to estimate the weld pool sizes from surface temperatures measured at various points on the top surface of the weldment. The main task of the neural network is to realize the mapping characteristics from the point temperatures to the weld pool sizes through training. The chosen design parameters of the neural network estimator, such as the number of hidden layers and the number of nodes in a layer, are based on an estimation error analysis. A series of bead-on-plate welding experiments were performed to assess the performance of the neural network estimator. The experimental results show that the proposed neural network estimator can estimate the weld pool sizes with satisfactory accuracy.
Closed-Loop Control of Weld Penetration Using Front-Face Vision Sensing
Authors: Zhang Y M , Kovacevic R , Wu L
Published: February 2007

Feedback control of weld penetration based on a front-face sensor is a challenging problem in the field of welding. A novel vision-based approach is proposed in this paper for full penetration control of the gas tungsten arc welding (GT AW). Owing to the relationship between the front-face weld geometry and back-face weld width (representation of the full penetration state), which has been reported earlier by the present authors, it is possible to use the front-face geometry as feedback of full penetration. Based on the dynamic modelling and the analysis of accepted adaptive control algorithms, an adaptive predictive decoupling controller is developed. Simulations and experiments under a variety of welding conditions have been conducted to verify the effectiveness of the proposed approach and controller.
Modelling and Simulation of Thermal and Closed-Loop Control Behaviour of Uranium-Bed Assemblies
Authors: Konstantellos A , Karditsas P J
Published: February 2007

A theoretical model describes the thermal and closed-loop control behaviour of uranium-bed assemblies used for the storage of hydrogen or its isotopes. Storage is in the form of UH3 at ambient temperature, and heating uranium-beds to 700-900 K can deliver the desorbed gas at pressures useful for transport to other process equipment. Modern compact uranium-bed assemblies include multiple-containment stainless-steel vessels to provide vacuum insulation and safety boundaries and to accommodate the heating and cooling systems. The thermal model describes the heat balance and the time evolution of the hydride powder temperature and includes radiation, dissociation and convection heat-transfer processes. The process controller simulation includes PID-type control/decision and adaptive algorithms. The model allows for simulations of the behaviour of the closed-loop system to demonstrate its effectiveness and to achieve controlled release of hydrogen, deuterium and tritium gas. A numerical example is presented which is based on a typical bed assembly. The simulation methodology used can easily incorporate more complex geometries, additional process components such as control valves, pumps and reservoirs as well as advanced control strategies as a means of predicting gas flow/pressure characteristics and bed safety.

This study was initiated after the first applications of uranium and other metal hydride beds in the active gas handling plant (AGH) of the Joint European Torus Project (JET), where (a) an in-depth knowledge of the bed control system and operation under tritium gas and a prediction of system parameters and tritium gas behaviour were needed, and (b) minimization of unnecessary testing and stressing of the uranium beds was required. The model can, in general, be applied to any hydride gas storage system and also has the capability to simulate the hydriding process.
The Electro-Rheological Clutch: Design, Performance Characteristics and Operation
Authors: Bullough W A , Johnson A R , Hosseini-Sianaki A , Makin J , Firoozian R
Published: February 2007

Fluid power transmission based on the electro-rheological clutch is taken beyond the concept-proving stage. A typical electro-rheological fluid is characterized over a range of engineering conditions and is found to usefully approximate to a continuum of Bingham plastic form. The clutch is optimized from this standpoint, and the limits of its performance are estimated. The state of the art is discussed alongside an outline of the infrastructure required to achieve maximum potential.
Robust Control of Robotic Manipulators with Model-Based Precompensation and SMC Postcompensation
Authors: Hong G S , Zhu H A , Teo C L , Poo A N
Published: February 2007

Robust and reliable control of robotic manipulators is studied. A model-based precompensation configuration is first used to decouple and linearize the highly complicated electromechanical dynamics of robotic manipulators. Then a linear state-feedback control law is used for closed-loop control. Finally, simplified SMC is adopted to postcompensate for the resulting error dynamics of the closed-loop control system. It is shown that the intentionally introduced control redundancy will not only ensure global high performance for the resulting system, but will also provide the system with built-in high reliability.
The Trajectory Tracking of an Electrohydraulic Servo-Mechanism via a Sliding Mode Controller
Authors: Hwang C L , Lan C H , Jieng W J
Published: February 2007

Since hydraulic power systems possess such features as high output power per unit weight, high acceleration capability and high torque stiffness, they are the most common form of precise power manipulation. In addition, the bandwidth of electrohydraulic servo-mechanisms is higher than that of pump control systems and thus they are more commonly used at present. However, some non-linear phenomena (for example stiction of cylinder, deadband due to internal leakage, fluid compressibility) make the precise microtrajectory tracking of an electrohydraulic servo-mechanism difficult. Because of the essential advantages of sliding mode control (fast response without, or with a little, overshoot, lower sensitivity to parameter variations and simple realization) a discrete-time servo-controller via the sliding mode technique is implemented to track a non-periodic trajectory.
Stochastic Optimal Control of Active Vehicle Suspensions Using Learning Automata
Authors: Gordon T J , Marsh C , Wu Q H
Published: February 2007

This paper is concerned with the application of reinforcement learning to the stochastic optimal control of an idealized active vehicle suspension system. The use of learning automata in optimal control is a new application of this machine learning technique, and the principal aim of this work is to define and demonstrate the method in a relatively simple context, as well as to compare performance against results obtained from standard linear optimal control theory. The most distinctive feature of the approach is that no formal modelling is involved in the control system design; once implemented, learning takes place on-line, and the automaton improves its control performance with respect to a predefined cost function. An important new feature of the method is the use of subset actions, which enables the automaton to reduce the size of its action set at any particular instant, without imposing any global restrictions on the controller that is eventually learnt. The results, though based on simulation studies, suggest that there is great potential for implementing learning control in active vehicle suspensions, as well as for many other systems.
The present and Future of Fluid Power
Authors: Backé W
Published: February 2007

This paper traces the development of fluid power from the formulation of the fundamental law of hydrostatics to the hydraulic applications of today. In the last few decades technology has advanced and many more uses have been found for fluid power. It is probable that these will increase in the future as competitiveness with other forms of power strengthens.
Advanced Underwater Power Systems
Authors: Hawley J G , Ashcroft S J , Patrick M A
Published: February 2007

The defence, commercial and scientific communities are all aware of the strategic importance that the oceans hold. Future underwater operations are under evaluation using autonomous ocean-ranging submersibles of the unmanned variety. Such vessels are commonly termed autonomous underwater vehicles (AUVs), and the search for suitable power systems that are able to provide high reliability coupled with long underwater durations has intensified over the last decade. This paper presents a review of those power systems that are under consideration, design and development, mainly for the AUV application. No attempt is made by the authors to directly compare individual systems, as this can only be effectively undertaken once a well-defined vehicle and associated mission profile has been defined.
Analytical Study of Hydro-Pneumatic Processes for Gorlov's Power System
Authors: Ryazanov A I
Published: February 2007

This paper describes the aerohydrodvnamics of processes in chambers of Gorlov's hydro-pneumatic power system. The mathematical model is developed to determine the main parameters of the processes: water and air velocities, air pressure in the chamber, the periods of time required to fill and empty the chambers and the output of energy during the cycle. The results obtained are in agreement with experimental data and model tests.
The Care and Maintenance of High-Temperature, High-Pressure Pipework Systems
Authors: Hoskins C
Published: February 2007

This paper describes the routine inspections carried out on the high-temperature, high-pressure steam pipework associated with large electricity generating units owned by PowerGen. The early implementation of the Pressure Systems and Transportable Gas Container Regulations, 1989, has allowed power stations more flexibility to set intervals between outages for inspection compared to the fixed intervals required under the Factories Act, 1961. Part of these inspections includes a detailed examination of high-temperature, high- pressure steam pipework welds and support systems. The method of inspection and analysis carried out to contain the risk of failure at welds due to high system stresses is described in the paper. Details are also included of how pipework flexibility analyses have been used to redesign some systems that have exhibited significant problems.
Environmental Economics and Electricity Generation
Authors: Robson A , Turner W J
Published: February 2007

Environmental economics, methodologies and issues are discussed and examples quoted for electricity generation systems. Results of the application of environmental ‘adders’ simulating a carbon tax in a British engineering-economic forecasting model are presented and the implications for energy strategy and nuclear energy discussed in relation to environmental factors.
Theoretical Predictions of the Full-and Part-Load Performance of an Air-Blown Fluidized Bed Gasification Combined Cycle
Authors: Davison J E , Soothill C D
Published: February 2007

It is important that any future power generation process should have a high thermal efficiency, be able to operate over a wide range of conditions and have low environmental emissions. This paper presents the results of work carried out by the British Coal Research Establishment (CRE) and European Gas Turbines (EGT) to evaluate the overall performance of an air-blown fluidized bed coal gasification combined cycle (topping cycle). This evaluation formed part of a major appraisal of the topping cycle chaired by EGT and which was carried out for the Department of Trade and Industry (DTI).

Performance predictions for commercial plants based on topping cycle technology were produced using a computer flowsheet modelling package developed at the CRE. The predicted full-load thermal efficiency of a base case plant using commercially available gas and steam turbines was 46.9 per cent. An evaluation of different options for providing the input air to the gasifier and the effects of likely future emission limits were also evaluated.

The part-loaded performance of the base case plant was predicted and it was shown to be capable of operating efficiently at power outputs down to 35 per cent or less. This flexibility means that the process should be suitable not only for base-load operation but also for locations where part-load operation may be required.
Thermal and Friction Factor Data for Three Packed Block Construction Wavy Fin Surfaces
Authors: BEng R J Gough , Al-Shemmeri T T
Published: February 2007

This paper describes an experimental work undertaken to determine performance data for packed block wavy fins. A purpose-built heat exchanger testing wind tunnel was used to investigate three wavy surfaces. The data were then presented in the form of Colburn (j) factors and friction (f) factors versus Reynolds number. Results showed a favourable comparison with published works pertaining to similar surface geometries; in addition, geometries were also tested which varied considerably from those in the literature to date.
Reverse Engineering of Quadric Surfaces Employing Three-Dimensional Laser Scanning
Authors: Bradley C , Vickers G W , Milroy M
Published: February 2007

A software package for the reverse engineering of surface forms commonly found in manufactured objects is presented. An object's surface is digitized using a three-dimensional, laser-based scanner that produces accurate and copious data files. Complex surface forms are reconstructed by interactively segmenting the multiple-surface patches, invoking the appropriate surface modelling routine and transferring the resulting surfaces to a CAD package via a standard IGES entity. Examples of the accuracy of the laser scanner data, and software algorithms for modelling planes, cylinders, cones and spheres, are presented by performing comparisons with results generated by a coordinate measuring machine. The paper concentrates on the novel software process to model the principal quadric forms; however, the program's capabilities do extend to free-form surfaces.
The Material Removal Mechanism in Magnetic Fluid Grinding of Ceramic Ball Bearings
Authors: Childs T H C , Mahmood S , Yoon H J
Published: February 2007

Recently a new process known as magnetic fluid grinding has been developed in Japan which can remove material in the finishing of ceramic balls some fifty times more rapidly than can the lapping processes that are conventionally used. Balls are driven round a cell by a rotating shaft in an arrangement similar to a thrust race but submerged in a magnetic fluid placed above permanent magnets. The magnets and fluid create buoyancy forces that levitate grinding grits in the fluid and also provide the loads for the process, but it is not clear why the process is more effective than lapping. This paper reports on experimental studies of the grinding rates of silicon nitride balls in magnetic fluids loaded with diamond grits and of the motion of the balls through the fluids. The high removal rates occur when skidding occurs between the balls and drive shaft. A kinematic theory is developed to calculate sliding speeds and is used to deduce an abrasive wear coefficient for the process of 0.07 ± 0.02, indicative of two-body abrasion. The high removal rates are a consequence of the large sliding speeds that can be developed, of several metres per second.
A Study of Vision-Based Measurement of Weld Joint Shape Incorporating the Neural Network
Authors: Bae K-Y , Na S-J
Published: February 2007

Visual sensing of the surface geometry is often necessary to inspect and evaluate the quality of welded joints as well as to sense the transient distortion of a structure during welding for the feedback of its current geometry. This investigation presents a simple and non-contact digitization method of the vision-based system for measuring the three-dimensional surface geometry of the object distorted by welding. Its basic principles are based on the equation derived from the geometric optics, for which the illumination of the laser beam was controlled in the form of the projected plane. This method utilized a 10 mW He-Ne laser for the structured light and a charge coupled device (CCD) camera as the vision sensor. When the laser stripe is projected on to the weldment, a minute deviation from the perfect plane existing on the specimen surface causes a distortion of the stripe. The shape and amount of the weldment distortion can be then calculated by analysing the distorted laser stripe.

In this study, a neural network was proposed and implemented for recognizing the laser stripe features from the image plane. A calibration scheme of corresponding an image to the world position was also adopted for determining the sectional features of the welding distortion. The feasibility of determining the welding distortion by the proposed vision-based system was demonstrated through the experiments with various types of specimen.
The Application of Envelope Theory to the Surface Geometry of Spool Winding Cams
Authors: Backhouse C J , Jones J Rees
Published: February 2007

An approach to the analysis of the surface form of spatial cams, based on envelope theory, is illustrated. The method, previously developed by the authors, is applied here to spool winding cams. These groove-type barrel cams employ followers having flank radii significantly larger than the groove width, implying particular problems in defining the form of the cam surface. The capability presented here to precisely define the surface form is the necessary precursor for optimum design and manufacture.
Identification of Abrasive Waterjet Nozzle Wear Based on Parametric Spectrum Estimation of Acoustic Signal
Authors: Kovacevic R , Wang L , Zhang Y M
Published: February 2007

The abrasive waterjet nozzle is one of the most critical parts that influences the technical and economical performance of an abrasive waterjet system. In order to control the uniformity of cutting results in milling and cutting, it is necessary to devise a sensing system that can sense on-line the nozzle wear. This paper presents an on-line technique for monitoring the nozzle wear which is based on monitoring the acoustic signals generated by the abrasive waterjet. The autoregressive moving average (ARMA) spectra are used to estimate the nozzle wear. It has been shown that the ARMA spectra can reveal more features of the nozzle wear than the conventional fast Fourier transform (FFT) method. It was found that the amplitude of the spectra and the frequency of the spectra peaks of ARMA models have a high sensitivity to a small variation of the nozzle exit geometry. A method based on on-line acoustic signals is proposed for identification of the nozzle inside diameter.
The Detection of Short Time-Scale Tool Degradation Events during Face Milling Operations Using Cutting Force and Acoustic Emission
Authors: Wilcox S J , Reuben R L
Published: February 2007

Experimental data are presented on the effects of short time-scale events on measured cutting force and acoustic emission during face milling. The events of interest are those that occur within a few revolutions of the cutting tool and are associated with non-continuous degradation such as insert edge chipping.

A processing scheme is suggested whereby the events are recognized and distinguished from each other using a neural network simulation applied to the peaks of the r.m.s. acoustic emission records. It is found that acoustic emission is a more suitable description of such events than is cutting force.

Finally, a record of the network simulation acting as a breakage detector in real time on a computer numerical control (CNC) milling machine is presented.
Helical Gear Vibration Excitation with Misalignment
Authors: Smith J D
Published: February 2007

Occasionally it is necessary to predict the effects of misalignment of gear helices on the regular once-per-tooth forces which are generated by the meshing. This can be done simply on a personal computer and gives results that show surprisingly high dynamic forces at high speeds. The computation is straightforward and the program is given.
Numerical Integration of Fluid Power Circuit Models Using Two-Stage Semi-Implicit Runge-Kutta Methods
Authors: Piché R , Ellman A
Published: February 2007

Fluid power circuits that contain fluid volumes of different orders of magnitude are difficult to simulate because the system of ordinary differential equations is numerically stiff. Even algorithms specially designed for stiff systems require excessively small time steps to avoid numerical oscillation in simulations of some circuits. In this paper the accuracy and numerical stability of several two-stage semi-implicit Runge-Kutta methods that have been proposed in circuit simulation literature are analysed and compared. It is shown that, for integration of very stiff circuits, the best method in this class is an L-stable method. A simple numerical example is used to verify the theoretical results. The example includes a novel way of modelling orifice flow that is especially suitable for numerical simulations.
The Vibration of Ring-Stiffened Cones Under External Water Pressure
Authors: Ross C T F , Richards W D
Published: February 2007

This paper describes a theoretical and an experimental investigation into the vibration of three ring-stiffened thin-walled conical shells, under external water pressure. The theoretical investigation was via the finite element method for both the shell structure and the surrounding water. Various fluid meshes were chosen, and a relatively simple one showed good agreement between experiment and theory.
Solution of the Classic Thermal Regenerator Problem
Authors: Organ A J
Published: February 2007

An exact, general and algebraically simple solution is obtained to the classic model of the thermal regenerator—general in the sense of covering flushing ratios, A, of any magnitude, including the small values of interest in the context of Stirling cycle machines, and of depicting start-up and cyclic steady state operation.

Specimen solutions turn the conventional picture of regenerator performance on its head: for a flushing ratio equal to or less than unity, for example, zero heat-transfer coefficient (NTU = 0) leads to a temperature recovery ratio of 100 per cent! At a thermal capacity ratio, NTCR, above a certain, minimal, value, the wall temperature distribution sits invariant between the extremes of gas temperature swing, and increased NTCR has no effect on temperature recovery ratio.

The findings are sufficient to explain reports of unexpectedly good performance of Stirling machines with regenerators of cotton wool or glass fibre.
Heat Transfer from a Diesel Engine and Estimation of Lubricating Oil Temperature
Authors: Lakshminarayanan P A , Dani A D
Published: February 2007

This paper describes the application of an analytical model based on established heat-transfer correlations to the prediction of lubricating oil temperatures in a diesel engine. Predictions are compared with experimental results from a number of stationary engines run at various speeds and loads and quite good agreement is shown. The model takes account of heat transferred from the combustion gases to the oil directly and indirectly, and of friction heat generated at bearings, piston rings and cylinder liner. The oil is partly cooled in the oil cooler. In small engines a substantial portion of this heat is convected from the engine surfaces, while in large engines not a negligible portion is convected. Equilibrium between the heat to oil and heat from oil to coolant and the ambient air determines the steady state oil temperature.
A Comparison of Approximate Forms of Air Spring Shells
Authors: Agnew B
Published: February 2007

The true form of an air spring shell is approximated to two forms consisting of circular arcs The first moments of the curves and the domain bounded by the curves are obtained and compared. An estimate of the difference in form between the true form and the approximate forms is presented.
Combustion in High-Speed Direct Injection Diesel Engines—A Comprehensive Study
Authors: Winterbone D E , Yates D A , Clough E , Rao K K , Gomes P , Sun J-H
Published: February 2007

This paper reports the latest results of a comprehensive project investigating the performance of a Ricardo Hydra direct injection diesel engine. Early work covered a number of aspects of research into the gross behaviour of this engine: this paper concentrates on techniques for obtaining quantitative data from photographs of the combustion process. High-speed photographs, at framing rates up to 20 000 frames/s, were taken using a piston with a quartz bowl, at engine speeds up to 3000 r/min. The pre-combustion period was illuminated using a synchronized copper vapour laser. After the initiation of combustion, the process is self-illuminating and information on the combustion process was obtained by analysing the radiation emitted by the carbon particles. The two-colour method was used to evaluate the temperature of the combustion gases over the full field of view. The images have also been analysed by a cross-correlation technique to obtain velocity information.

Tests have been performed on the engine over a wide range of operating conditions, but this paper concentrates on the effect of swirl ratio on combustion. It will be shown that too much swirl increases the ignition delay period and results in an increase in the NOx emissions but a decrease in the soot. It will also be shown that the velocity pattern after combustion is in good agreement with that evaluated by Arcoumanis et al. at the end of compression, which implies that swirl persists through the combustion period despite significant decay.
Effects of Variable Solids Loading on Gas-Solid Heat Transfer in a Staggered Tube Array
Authors: Murray D B , Humphreys I
Published: February 2007

For staggered tube arrays subject to gas-solid cross flows with low solids concentrations, the overall heat-transfer performance can be reduced by the presence of the solids in the flow. This paper investigates the effect of varying solids concentration on cross flow heat transfer with a view to identifying the dominant heat-transfer mechanisms for higher solids concentrations. Measurements are obtained for tubes located within a staggered tube array subject to mass loading ratios of up to 2.2 kg/kg of particles of 58 and 46 μm mean diameter at flow Reynolds numbers of 3000 and 10 000. From the results it is found that, although heat transfer in the wake of a tube is commonly reduced by the particles, a significant increase in the overall Nusselt number can be expected. The reduction in heat transfer in the wake region is attributed to a combination of delayed boundary layer separation and turbulence suppression by the solids, whereas the very significant enhancement of heat transfer measured over the front of the tubes is considered to result mainly from the increased thermal capacity of the mixture.
Modelling of Heat Generation and Resultant Temperature Distribution Due to the Passage of an Ultrasonic Wave Through a Mixture of Polyborosiloxane and Silicon Carbide
Authors: Fletcher A J , Fioravanti A
Published: February 2007

A mixture of polyborosiloxane and silicon carbide abrasive has been agitated using an ultrasonic system. The passage of the ultrasonic wave through this mixture resulted in an increase in temperature due to conversion of energy from the ultrasonic wave into heat. This investigation was initially concerned with the calculation of the heat-generation term, from a knowledge of the attenuation of the acoustic wave. The second stage of the analysis involved the solution of the relevant transient heat-transfer equations for conduction and convection with internal heat generation. The solution to these equations was obtained using a numerical technique.

Temperatures at various positions within the system were measured using suitable equipment. These experimental data were compared against the results of the calculation and it was found that significant discrepancies existed between the two sets of results when the analysis considered heat generation as a sole function of wave attenuation.

In an attempt to improve the correlation between calculated and measured temperatures the analysis was developed to include a heat-generation term acting at the interface between the sonotrode and the transmission medium. Such heat generation would be produced by frictional heating at the interface, and this would be associated with poor coupling between the acoustic source and the medium. It was found that the correlation between calculated and measured temperatures improved greatly on adoption of the frictional heating analysis, which leads to the suggestion that heating within the medium is a function of both ultrasonic attenuation and frictional heating. For the conditions specified the latter appears to have a dominant role.
An Experimental Study on the Dynamic Response of a Beam Structure Containing a Pseudo Joint
Authors: Ren Y , Beards C F
Published: February 2007

The effects of frictional damping on the dynamic response of a beam structure have been investigated. The frictional damping was contributed from the slip mechanisms in a ‘pseudo’ joint, that is a joint that did not take any static load. Using pseudo joints for vibration control has significant advantages over using joints that are designed both to take static load and to introduce frictional damping; because there is almost no restriction on the configuration of the pseudo joint, the undesirable side effects related to the frictional damping such as fretting corrosion of contact surfaces and loss of static stiffness are zero if the frictional damping from a pseudo joint is utilized.

An ‘optimum’ clamping force was found which minimized the magnitude of the frequency response function (FRF) of the structure under excitation. A reduction of about 20 dB in the amplitudes of the FRFs was achieved by adjusting the clamping force at the joint. Frictional damping was found to be significant over the measured frequency range of 20-2000 Hz, and it was particularly effective over the range of 20-1000 Hz. The magnitudes of the FRFs of the structure were determined by the ratio of clamping force to excitation force. They were insensitive to the change of clamping force near its optimum value; also the optimum clamping force was not sensitive to small modifications to the structure. Therefore, utilizing frictional damping in pseudo joints is an effective technique for vibration control.
A New Wobble Drive with Particular Application in a Stirling Engine
Authors: Clucas D M , Raine J K
Published: February 2007

Swash plate or wobble mechanisms used in engine drives commonly require gearing, slides and/or spherical bearings to connect the piston rods to the transfer mechanism and react to the torque produced. This paper briefly reviews the literature on this class of engine mechanism and presents the theory and form design of a new wobble yoke mechanism which achieves single degree of freedom rotational motion for all bearings, enabling the use of sealed rolling element bearings and eliminating the need for sliding surfaces or gears.

The mechanism has been first applied in a liquefied petroleum gas-fuelled integrated Stirling engine electric generator system for battery charging. The hermetically sealed system gives 200 watt d.c. electrical output and is configured for charging 12 volt batteries. A square four-cylinder double-acting configuration is used, with pistons equispaced and parallel to the output shaft. The mechanism is easily parametrically scaled to different engine sizes. It also has potential application in compressors, pumps, other Stirling cycle machines or Otto cycle engines. Development of mechanical design features and thermodynamic and electrical development of the Stirling engine generator are to be described in a subsequent paper, to be published in the next Part C issue.
Development of a Hermetically Sealed Stirling Engine Battery Charger
Authors: Clucas D M , Raine J K
Published: February 2007

Recent Stirling engine research at the University of Canterbury has focused on the development of a compact 12 volt 200 watt electrical battery charger suitable for use in yachts, mobile homes or remote dwellings, and intended for scaling up to larger power applications. The hermetically sealed engine with integral alternator uses a four-cylinder double-acting configuration with air pressurized to 1 MPa as the working fluid. The engine and battery charger control system includes self-regulation, and automatic start and shut-down. The previous paper has described the wobble yoke mechanism which is central to the engine design as it requires only pre-lubricated single degree of freedom bearings. This paper explains the design philosophy behind the new engine and describes the computer modelling and subsequent development of engine components on an alpha configuration experimental prototype. Features examined include the alternator, the cylinder-mounted seals and the heat exchangers. Embodiment design features of the final double-acting prototype are discussed. Performance data for the experimental prototype are presented.
The Mechanics of Parallel Mechanisms and Walking Machines
Authors: Zhang S J , Sanger D J , Howard D
Published: February 2007

A parallel mechanism is one whose links and joints form two or more serially connected chains which join the fixed base and the end effector The mechanism of a multi-legged walking machine can be considered as a parallel mechanism whose base is not fixed and whose configuration changes during different phases of its gait.

This paper presents methods for analysing the mechanics of parallel mechanisms and walking machines using vector and screw algebra Firstly, displacement analysis is covered; this includes general methods for deriving the position vector of any joint in any leg and for calculating the active joint displacements in any leg. Secondly, velocity analysis is covered which tackles the problem of calculating active joint velocities given the velocity, position and the orientation of the body and the positions of the feet. Thirdly, the static analysis of these classes of mechanisms using the principle of virtual work and screw algebra is given. Expressions are derived for the actuator forces and torques required to balance a given end effector (or body) wrench and, in the case of a walking machine, the ground reactions at the feet. Numerical examples are given to demonstrate the application of these methods.
A Precise Time Step Integration Method
Authors: Zhong W X , Williams F W
Published: February 2007

A high-precision numerical time step integration method is proposed for a linear time-invariant structural dynamic system. Its numerical results are almost identical to the precise solution and are almost independent of the time step size for a wide range of step sizes. Numerical examples illustrate this high precision.
The Sources of Unburnt Hydrocarbon Emissions from Spark Ignition Engines during Cold Starts and Warm-Up
Authors: Boam D J , Finlay I C , Biddulph T W , Ma T A , Lee R , Richardson S H , Bloomfleld J , Green J A , Wallace S , Woods W A , Brown P
Published: February 2007

The results of a three-year collaborative research study into the sources of unburnt hydrocarbon (uHC) emissions are reported. The study sought to extend existing knowledge of the sources in an engine to the crucial period following a cold start and before the exhaust catalyst becomes fully effective. The study, carried out on a range of engines but centred on the Rover M 16 four-valve engine, identified a number of sources, all of which are equally important in the warm-up period. The paper concludes with some recommendations for the control of uHC emissions
Using CFRP for the Design of a Connecting Rod for Automobile Applications
Authors: Gunyaev G M , Borovskaya S M , Panin V I
Published: February 2007

Composite materials may be used for selective improvements to automobile engines. For example, using a composite connecting rod offers some advantages such as weight saving, inertial forces reductions, increasing automobile speeds and reducing noise emission from engines.

Two technological approaches were chosen for connecting rod production. The first type of connecting rod consists of a compression-stressed shank made of laminated plastic and the tension loop made of carbon fibre reinforced plastic (CFRP). The second type of connecting rod is made of multi-directional laminated CFRP. Due to these approaches split and unsplit versions were made. Moreover, the titanium-CFRP concept of the split connecting rod was assessed.

Several studies have shown the possibility of manufacturing composite connecting rods satisfying load requirements for engine components.
The Application of Multi-Body Computer Codes to Road Vehicle Dynamics Modelling Problems
Authors: Sharp R S
Published: February 2007

Issues involved in the automation of the mathematical modelling of multi-body systems with special reference to road vehicle dynamics problems are discussed and reviewed. Some background and historical informations are provided. Those aspects of road vehicle dynamics problems that are of greatest concern from the point of multi-body modelling and rapid simulation are then considered. Various foundations for the equations of motion of multi-body systems and the treatment of constraints are described and some of the implications of methods chosen are exposed. Significant aspects of the modes of operation of the main relevant numerical and symbolic multi-body modelling codes are addressed. Conclusions are reached on the present state of multi-body modelling as relating to road vehicle dynamics and some thoughts on strategies for effectiveness in the future are offered. A substantial reference list, through which the topic can be pursued in greater detail, is included.
Applications of a Computer Aided Method to Parametric Study of Tracked Vehicles with Rigid Links
Authors: Wong J Y , Gao Y
Published: February 2007

This paper demonstrates the applications of a computer aided method (CAM) to the parametric study of tracked vehicles with rigid links, commonly in use in agriculture, construction and logging. The results of the study show that the track pitch, number of road-wheels, initial track tension and location of the centre of gravity have a noticeable effect on tractive performance over soft terrain. It is also found that by careful selection of a combination of design parameters, vehicle performance can be significantly improved. It is shown that the computer aided method can play a significant role in design optimization of tracked vehicles with rigid links and in the evaluation of vehicle candidates for a given mission and environment.
Improving the Process of Engine Design through the Integrated Application of CAE Methods
Authors: Smith A V , Johns R J R , McNamara P M
Published: February 2007

The increasingly competitive nature of the automotive industry is forcing engine design organizations to target improvements in function and quality at the same time as substantial reductions, in product development cycle times. This paper describes how Ricardo is meeting this challenge through the integrated development and application of computer aided engineering (CAE) methods. The weaknesses of traditional approaches to the management of CAE innovation are discussed and the need for a more strategic approach is identified. Examples are given of CAE research, development and applications carried out by Ricardo. Conclusions are presented outlining the key elements of an effective CAE strategy.
Light-Duty Diesels—an Update on the Emissions Challenge
Authors: Horrocks R W
Published: February 2007

The next major stage of emissions legislation for European Community countries is planned for 1996. This paper examines these proposed standards and the effect they will have on light-duty automotive diesel vehicles. The present status of the Clean Air Act amendments in the United States is also considered. The latest developments in light-duty automotive diesel technology are reviewed, particularly with respect to achieving the lower emission standards and the effect on fuel economy.
Saddle and Lug Supported Tanks and Vessels
Authors: Křupka V
Published: February 2007

High stresses originate in the region of the support of circular cylindrical storage tanks and vessels. These influence the brittle fracture and crack growth by cyclic loading. The plastic deformation caused by the squeeze of the saddle into the vessel limits, in particular, the carrying capacity. Besides local stresses the effect of buckling is not negligible. The difference between the loose and welded support is discussed. Unstiffened and ring-stiffened circular cylindrical tanks are taken into consideration. Derived formulae enable the designer to take into account the effect of cyclic load, fatigue and buckling.
Plastic Loads for Piping Branch Junctions Subjected to Combined Pressure and In-Plane Moment Loads
Authors: Kirkwood M G , Moffat D G
Published: February 2007

Experimental results are presented from plastic collapse tests on a series of 150 mm nominal diameter piping branch junctions. The loads considered are internal pressure and both branch and run pipe in-plane bending. Plastic loads are defined and presented for individual loads followed by combined pressure and moment results in the form of plastic load interaction diagrams. The results are discussed in the light of the ASME III nuclear pressure vessel design code rules.
Realizing Engineering Potential in Ocean Wealth Generation
Authors: Kuo C
Published: February 2007

The paper begins by highlighting the importance and contributions of the various types of ocean wealth to human well-being. These range from oil, food and minerals to a medium for the transportation of bulk goods and a source of renewable energy. The commercial goal to be satisfied in order to achieve success is then stated and a methodology, based on a tree diagram approach, for identifying ocean market opportunities is described. Four examples relating to support for ocean activities are used to illustrate its application. These deal with underwater navigation systems, intermodal marine transport maritime and offshore safety, and dredging. The criteria for fully realizing the engineering potential are considered. They range from the importance of meeting the commercial goal and the impact of safety on ocean activities to the role of human factors and fresh educational methods. The need for an integrated approach to ocean wealth generation and the contribution of research and development efforts are discussed. The main conclusion is that many other forms of wealth with a potential market as large as that of offshore oil and gas are waiting to be ‘discovered’.