bluuebunny/crossref_metadata_2025 huggingface dataset:
Improvement of the Accuracy of a PUMA 560 Industrial Manipulator by Calibration
Authors: Greig A R , Lovell S P
Published: February 2007

Compared to their repeatability, the accuracy of industrial manipulators is disappointingly poor. To permit off-line programming of manipulators and interaction with their local surrounds a high positional accuracy is required; this is particularly true for operation under supervisory control. The accuracy of a manipulator can be improved by calibration of its link lengths and joint angle measurements.

This paper presents the results of the calibration of a PUMA 560 industrial manipulator and discusses simplifications to the procedure and theory which improve the practicality of the method without seriously compromising the results. Circle point analysis is used with data points being recorded by a pair of theodolites; the relevant theory is presented in the Appendix. A joint error correction function is produced for each joint. A fourfold improvement in accuracy is demonstrated without unduly increasing the complexity of the kinematics or requiring a sophisticated end effector.
A Study on Parameter Optimization for Circumferential Gas Tungsten Arc (GTA) Welding of Small Pipes considering Backing Gas Pressure: Part 1: Analysis of Weld Pool Surface Profile
Authors: Na S-J , Lho T-J
Published: February 2007

It is well known that the weld bead becomes wider and the weld pool hangs down as the circumferential welding of small-diameter pipes progresses, if constant welding conditions are maintained over the entire joint length and/or no appropriate backing gas is supplied into the pipe. In order to obtain a weld bead which is uniform in width and does not hang down over the whole circumference of the pipe, the welding parameters such as welding current, welding velocity and backing gas pressure should be optimized as the welding progresses. In order to optimize the welding parameters, a mathematical model for determining the temperature distribution in the pipe workpiece and the surface profile of the resultant weld pool is indispensable.

An efficient finite difference model was adopted for calculating the three-dimensional transient temperature distribution in circumferential gas tungsten arc (GTA) welding of pipes. Its solution was obtained by employing the alternating direction implicit (ADI) finite difference method, in which a periodic boundary condition and a periodic cubic spline function were used. For calculating the weld pool surface profiles in full penetration circumferential welding of pipes, a governing equation was derived in the cylindrical coordinate and solved using a simple finite difference model with the ADI scheme.

In Part 2 of this paper, an efficient parameter optimization method is used to evaluate the optimal welding current for a required bead width when the welding velocity is given.
Process Re-Engineering Provides the Impetus for Accelerating Change
Authors: Garvey V J
Published: February 2007

Strix Limited is the world's leading supplier of waterboiling controls for the domestic appliance industry. This paper will describe how a successful project has helped develop a culture where the focus has now progressed from change to one of accelerating change. A brief look at the company's background will be used to explain the need for a change culture. The lead project will be described in some detail, and some conclusions drawn. A brief overview of further projects will illustrate the robustness of the method.
Analysis and Computer Simulation of the Electrochemical Machining Process: A Stepped Moving Tool Eroding a Plane Surface
Authors: Hardisty H , Mileham A R , Shirvani H
Published: February 2007

This paper presents a theoretical and computational investigation of the electrochemical machining (ECM) process, for the important practical case of a stepped tool eroding an initially flat work surface. A fully automatic computer package based on the finite element method (FEM) has been developed which simulates the two-dimensional ECM process. To provide theoretical benchmarks for the computer simulation, differential erosion of a step has been analysed in terms of the one-dimensional processes on either side of it. To facilitate this analysis, the basic erosion equation has been approximated by a simple exponential relation, which becomes increasingly exact as time increases. This has enabled explicit equations for the time required to machine a step to be developed. This simple theoretical model both provides insight into the ECM process and facilitates design estimates of the time required to erode a step to a given tolerance.

Five characteristic cases of erosion with a stepped tool have been summarized in parametric form. For one of these cases, results from the two-dimensional computer simulation have been compared with theory; there is good agreement. It is intended that the computer results from the four remaining cases will be presented in a later companion paper which will provide additional information on the computer package and the two-dimensional results from it.
Computer Simulation of the Deformation of Dough-Like Materials in a Parallel Plate Gripper
Authors: Evans B S , Brett P N
Published: February 2007

Flexible automation for the handling of rigid materials has been available for many years, but similar systems are not as yet available for the handling of non-rigid materials such as doughs. The properties of this type of material require careful control of gripping and manipulation forces to prevent the product from deforming out of tolerance during handling. This paper describes a computationally efficient model that has been developed for use in the planning and control of gripping and manipulation strategies for dough-like materials. In addition to describing the model and the way in which it would be used in an automated handling environment, experimental results demonstrating the accuracy of the model in predicting the behaviour of three doughs are presented.
The Effects of Geometric Variables in Roll Forming a Channel Section
Authors: Zhu S D , Panton S M , Duncan J L
Published: February 2007

A model of the roll forming process developed previously by the authors was used to examine the effect of geometric variables such as flange length, thickness, bend angle, bend angle increment and roll diameter on the longitudinal strain developed in the roll forming of channel sections. The peak longitudinal strain was found to increase with flange length and then drop when the flange length reaches a critical value. The peak longitudinal strain was found to increase with thickness. In general, increasing the bend angle increment was found to increase the peak longitudinal strain despite the fact that the deformation length also increases. Increasing the roll diameter was found to decrease the peak longitudinal strain. The results from the study explain several roll forming phenomena observed in previous experimental studies.
Reverse Engineering Physical Models Employing Wrap-Around B-Spline Surfaces and Quadrics
Authors: Weir D J , Milroy M J , Bradley C , Vickers G W
Published: February 2007

Reverse engineering involves digitizing a three-dimensional model or part, by means of a tactile or non-contact optical sensor, converting the data to a CAD (computer aided design) database description and manufacturing by CNC (computer numerical controlled) machines. This paper demonstrates an effective approach to the reverse engineering of physical models by employing a three-dimensional laser scanning system in conjunction with surface-fitting software developed by the authors. Accurate surface data are collected by the laser scanner and then input to the surface-fitting software. Surface entities such as B-spline and quadric functions are employed to build the CAD model. The CAD model is compatible with popular design and manufacturing software packages. A telephone receiver is used to illustrate the efficiency of the process.
Dynamics and Trackability of Stylus Systems
Authors: Whitehouse D J , Wang W L
Published: February 2007

Surface measuring instruments have been used for fifty years and their applications have been widespread. However, new demands are being made such as increased speed of measurement and also the capability of measuring more complex surfaces. This paper examines ways in which the design of the pick-up element can be optimized. It also deals in detail with the optimum parameters needed to measure a wide variety of random as well as periodic surfaces.
A New Approach to Modelling Machined Surface Profiles
Authors: Hasegawa M , Liu J C , Okuda K , Nunobiki M
Published: February 2007

A new approach to modelling machined surface profiles is presented in this paper. The fractal characteristics of the ARMA model are first investigated. It is found that the ARMA model behaves in a fractal manner. Then, based on this result, the relationships between the parameters of the ARMA model and its fractal dimensions are studied by use of the multiple regression analysis. In this way, the parameters of the ARMA model of a machined surface profile can be decided by calculating its fractal dimension. The way the fractal dimensions of the machined surface profiles are affected by the machining conditions is also studied. Therefore using these results, the ARMA model of the machined surface profile can be derived directly from the machining conditions. The AIC (Akaike information criterion) is used as the selection criterion for the model obtained using this approach. Finally, modelling of cut surface profiles is carried out.
Achieving Competitive Edge
Authors: Graham-Bryce A L
Published: February 2007

The need for manufacturing companies, particularly those in the defence sector, to become more competitive in global markets is well known. As a case study of what can be achieved, this paper describes a programme in which new approaches—including team working, world class manufacturing, production cells and JIT—were used to transform a traditional, protected manufacturing supply organization into a viable business to meet the challenge of low-cost international competition. The programme was called the ACE project.
Quality Support for the Army's Equipment
Authors: Corp P J G
Published: February 2007

The Royal Electrical and Mechanical Engineers (REME) was formed in 1942, with strong support from the major engineering institutions, as the Army's professional repair and recovery corps. Its role has progressively broadened into that of an integrated support organization involved in the whole equipment life cycle: besides repair, its key processes now span engineering policy, fleet management, redesign and modification, spares procurement and future design influence. The past three years have seen radical restructuring and innovation throughout the organization, both in response to wider government and departmental changes and in order to provide a better service to the Army at less cost. Underpinning these changes is a strong ‘total quality’ ethos throughout the organization. REME has entered its second half-century committed to continuous improvement, both in peace and on operations.
Design and Manufacture by Foreign Electronics Multi-Nationals in Singapore and Taiwan: Product Responsibilities in a Global Environment
Authors: Tilley K J , Williams D J , Conway P P
Published: February 2007

The electronics clusters in Singapore and Taiwan have grown largely as a result of foreign direct investment. It is shown that foreign electronics companies in Singapore and Taiwan manufacture with processes close to the state-of-the-art and have considerable process and product design responsibilities. It is established that the products designed are not the core technology for the companies concerned. When compared to the development of the Scottish sites of foreign electronics companies, the sites in Singapore and Taiwan compare favourably in terms of time to obtain design responsibilities and the size of R & D (research and development) teams. National initiatives in Singapore and Taiwan that support the move to R & D at foreign sites are described.
A Survey of Design Philosophies, Models, Methods and Systems
Authors: Evbuomwan N F O , Sivaloganathan S , Jebb A
Published: February 2007

The study of the design process, design theory and methodology has been a preoccupation of engineers, designers and researchers over the last four to five decades. As the end of this millenium is approached and with the renewed interest around the world in engineering design, it is fitting to examine the state of the art and current status of issues relating to design philosophies, theory and methodology. Over the last 40 years, many approaches to design have been put forward by various researchers, designers and engineers, both in academia and industry, on how design ought to and might be carried out. These proposals on design have tended towards what has come to be regarded as design philosophies, design models and design methods. The thesis of this paper is to discuss various aspects of generic research in design, within the above classifications in the light of the work that has been done in the last four decades. Discussions will focus on various definitions of design, design theory and methodology, the nature and variety of design problems, design classifications, philosophies, models, methods and systems.
Grinding Vibration Detection Using a Neural Network
Authors: Chen X , Rowe W B , Li Y , Mills B
Published: February 2007

The amplitude of grinding vibration increases gradually throughout the grinding wheel wear process. In the meantime the predominant vibration frequency shifts in a region close to a natural frequency of the system. The complex time-varying pattern of vibrations makes it a problem to objectively identify when the grinding vibration becomes unacceptable and when the wheel should be redressed. A neural network approach method was proposed in this paper to identify the wheel life. The signal data were pre-treated by eight-band-pass filters, which covered the whole frequency range of the grinding chatter. These pre-treated data were used as the inputs to the neural network. By training the neural network, an objective criterion can be determined for the wheel redress life.
Shot Peen Forming Sheet Metal: Finite Element Prediction of Deformed Shape
Authors: Grasty L V , Andrew C
Published: February 2007

Shot peen forming is a production process used to create curved metal parts from sheet. It is commercially important despite the fact that its mechanisms are not fully understood; peen forming programmes are currently generated using experience and trial and error. The purpose of this work is to increase the predictability and range of application of the process by advancing its understanding.

Finite element analysis proved to be a satisfactory procedure for studying shot peen forming. The stress distribution in a sheet arising from multiple indentations, as occur in shot peen forming, was modelled. A technique of squeezing the upper layers of a finite element model was shown to be a good simulation of the stress distributions resulting from shot peen forming, and provided a much more tractable analysis with respect to computing time and resources.
Criterion for the Locality of a Manipulator Arm with Respect to an Operating Point
Authors: Abdel-Malek K
Published: February 2007

Criteria for determining an optimum locality of a manipulator arm are developed. In many cases, in a manufacturing environment, the tools, fixtures and targets that a manipulator has to deal with cannot be relocated. Thus, the choice of the manipulator locality is important. The method presented in this paper uses the notion of a service sphere to determine required orientability at an operating point. The boundary surfaces to the wrist-accessible output set is determined and positioned such that the service sphere is inside the wrist-accessible output set.

To determine boundary surfaces of the wrist-accessible output set, manipulator singularities (internal boundary, and higher order) are computed and substituted into the constraint equation to parameterize singular surfaces. Part of these surfaces may lie internal to the boundary while other parts are a subset of the boundary. Singular surfaces are then intersected to determine second-order singularities. Second-order singularities partition surfaces into subsurfaces. Those subsurfaces on the boundary are determined by perturbing a point on the surface and concluding whether the perturbed point satisfies the constraint equations. The boundary to the wrist-accessible output set is then located with respect to the service sphere. The locality of the manipulator is determined for maximum orientability.
The Attitudes of Small Companies to the ISO 9000 Series
Authors: McTeer M M , Dale B G
Published: February 2007

This paper reports the main findings of a study of eight companies with fifty or less employees which investigated their attitudes, problems and successes in relation to registration to the ISO 9000 series of quality management system standards. All the companies studied had attended a Workshop Programme training course to provide them with the requisite advice and assistance to gain registration. However, only one of the eight companies went on to gain ISO 9000 series registration. In every case the perception that the market-place was demanding or likely to demand ISO 9000 series registration was the prime motivator. The two main drawbacks of introducing an ISO 9000 series quality management system standard were time and the volume of paperwork.
Tool Management and Job Allocation in Flexible Machining Cells Part 2: Tool-Oriented Strategies
Authors: Coleman P , Ozbayrak M , Bell R
Published: February 2007

This paper illustrates the potential for the improved economic provision of tooling in flexible machining cells, through the use of a multi-stage algorithm for the allocation of jobs to machines and the efficient exchange of the associated tool kits. The tool-oriented manufacturing algorithm uses a combination of clustering techniques to identify groups of jobs which have some similarity of operational and hence tooling requirements. These clustered groups are allocated to a particular machining cell configuration with respect to the additional constraints of balancing the overall work load per machine and managing tool kit exchange under limited tool magazine capacity. The performance of tool-oriented strategies has been investigated using a computational study and indicates a consistent advantage compared to alternative work-oriented strategies. This is measured in terms of the quantity and frequency of tool exchange activities required over a given manufacturing period and the degree of necessary disturbance to the sequence of job throughput.
Rotational Moulding of Liquid Polymers
Authors: Harkin-Jones E , Crawford R J
Published: February 2007

The vast majority of rotationally moulded articles are produced from powdered polymers. However, the moulding process developed originally from the use of liquid polymers and nowadays there is a renewed interest in such systems because of some unique advantages that they offer.

This paper compares the behaviour of three different liquid polymer systems—nylon 6 by ring-opening caprolactam, polyvinyl chloride plastisol and polyurethane. The flow behaviour of each material is examined with particular reference to wall thickness distributions and bubble formation in the product. On the basis of this, criteria for the production of fault-free mouldings have been established. The interrelationships between mould shape and resin viscosity are also examined and an ideal viscosity—time—temperature profile is proposed for liquid polymer systems. Finally, a general comparison of the materials is made with regard to material handling, safety, cycle times, etc.
The Multi-Factor Design Evaluation of Antenna Structures by Parameter Profile Analysis
Authors: Liu J S , Thompson G
Published: February 2007

The design of antenna structures involves complex mechanical and electrical analyses. An evaluation method is proposed by which the results of such analyses can be combined to assess the overall merit of an antenna design. The method considers the antenna at different elevations to represent the range of its working conditions in service. A feature of the method is the use of the proximity of the calculated performance of the antenna with respect to certain parameters compared to the performance that can be reasonably expected for each parameter. An antenna structure is analysed and the results are used in the evaluation method to demonstrate how the method is applied.
Prediction of Cutting Forces and Built-Up Edge Formation Conditions in Machining With Oblique Nose Radius Tools
Authors: Arsecularatne J A , Fowle R F , Mathew P , Oxley P L B
Published: February 2007

A semi-empirical machining theory is described for predicting cutting forces and temperatures for oblique nose radius tools from cutting conditions and a knowledge of work material flow stress and thermal properties. Predictions are made for a range of cutting speeds and tool geometries. It is shown how the cutting conditions giving a built-up edge can be determined from the predicted cutting temperatures. A comparison between predicted and experimental results shows good agreement.
Robotic Assembly Operation Strategy Investigation Without Force Sensors Through the Research on Contact Point Location and Range of Peg Movement
Authors: Qiao H , Dalay B S , Knight J A G
Published: February 2007

The assembly operation plays an important role in manufacturing industry. The robotic peg-hole insertion operation, the most widely used assembly model, has been heavily studied due to its widespread application. The purpose of the research in this area is to design techniques that enable the robot to perform assembly operations with high speed, high accuracy and low cost. The key problems of strategy investigation research include: (a) designing a series of sub-goals through which the peg-hole system can achieve the insertion operation from any point in the initial area, (b) calculating the allowable range for the initial area, (c) determining the values and duration of the control inputs and (d) analysing the robustness of the strategy.

There are many strategies given to perform the assembly operation with the assistance of specially designed force sensors or flexible wrists. In this paper: 1. The map from the position of the peg in the coordinate frame attached to the hole and the location of the contact point in the frame attached to the peg was analysed. This provided the basis for the identification of the position relationship between the peg and the hole using a force sensor signal. 2. The range of peg movement was analysed and found to be useful in the selection of the sub-goals for the insertion operation. 3. A deficient and yet precise hardware strategy, characterized by not requiring force sensors or flexible wrists, was analysed. 4. The validity of the deficient hardware strategy was demonstrated through experiments with the UMI-RTX robot. The results were further confirmed through simulation. The allowed initial area, the control input design and the robustness of the strategy were analysed in detail.

A constant cycle time of 2.5 s was achieved during the ten trials in which the diameters of the pegs were selected from a choice of 29.99, 31.98 or 31.99 mm with a clearance between the hole remaining at 0.02 mm and a common peg legnth of 41 mm.
Motion Planning with Reversal Manoeuvres for a Non-Holonomic Constrained Robot
Authors: Jiang K , Seneviratne L D , Earles S W E
Published: February 2007

This paper presents a new motion planning approach, including reversal manoeuvres, for car-like robots subject to non-holonomic constraints. The paper presents a complete path planning algorithm and describes the procedure for constructing a collision-free path for a mobile robot constrained by its rectangular shape and kinematics. Emphasis is made on the techniques of reversal transfers, which are used to compensate the limited manoeuvrability of a car-like robot. The approach works entirely in the workspace, as opposed to building a higher dimensional configuration space (C-space). It starts by constructing a visibility graph and finding the shortest path for a point robot and then detects areas where collision may occur by minimum distance calculations between obstacles and between the selected path and obstacles. Robot configurations are placed along the shortest path and lemmas are developed for ascertaining transfers from one robot configuration to another. The transfer techniques include direct, indirect and reversal manoeuvres, and ensure that the path is feasible for the robot to travel with a given steering limit. The process runs in time O(nk + n log n) for k obstacles and n vertices. The algorithm is tested in computer simulations and results are given, demonstrating the versatility of the algorithm.
Problems of Creating Computer Integrated Manufacture for Pilot Mechanical Engineering
Authors: Adamov E O , Gnedenko V G , Dukarskii S M
Published: February 2007

The specific features of experimental mechanical engineering require production and technical systems (PTSs) to be highly flexible. At the same time, the necessity of engineering and production support for scientific research work and the development of new equipment with limited labour resources in the shortest period of time make it necessary to increase the level of PTS automation. The problem of flexible automation of PTSs can be solved by creating a computer integrated manufacture (CIM). The present article describes the experience of the creation of CIM for the production of high-technology experimental equipment at the Russian Research Centre (RRC) ‘Kurchatov Institute’. The system functions and the level of automation of various activities in the system are described. Methods of overcoming many troubles encountered during the creation of CIMs are shown.
Two-Stage Approach for Nesting in Two-Dimensional Cutting Problems Using Neural Network and Simulated Annealing
Authors: Han G-C , Na S-J
Published: February 2007

Nesting of two-dimensional patterns on a given raw sheet has applications in a number of industries. It is a common problem often faced by designers in the shipbuilding, garment making, blanking die design, glass and wood industries. This paper presents a new two-stage layout approach for nesting two-dimensional patterns by using the self-organization assisted layout and simulated annealing. The proposed nesting approach consists of two stages: initial layout stage and layout improvement stage. This heuristic algorithm generates a ‘good’ initial layout by using the self-organization assisted layout (SOAL) algorithm and then improves the layout by using the simulated annealing (SA) algorithm. Some examples are treated for showing the effectiveness of this approach in nesting the two-dimensional irregular patterns with and without holes.
Removal of Pinholes and Bubbles from Rotationally Moulded Products
Authors: Spence A G , Crawford R J
Published: February 2007

The rotational moulding processing method for plastics is steadily expanding its product range and market areas. However, a drawback of the process has always been the surface pinholes and internal bubbles which occur in the products due to the inherent nature of the process. In an attempt to alleviate this problem, a programme of research has been carried out to investigate the factors that affect the formation of the bubbles and more importantly influence their removal.

This paper describes how bubbles in rotationally moulded products can be removed by pressurizing the inner atmosphere of the mould. It has been shown that bubbles were successfully removed from MDPE (medium density polyethylene) by introducing a low pressure (0.5 bar) inside the mould after the polymer had melted. The removal of bubbles using pressure was shown to increase the impact properties (25 per cent) and the tensile properties (5 per cent) of the moulding while also reducing the cycle time. Pressure was successfully used to remove bubbles from other rotational moulding materials, such as polypropylene, Nylon 12, polycarbonate, ethylene vinyl acetate and ethylene butyl acetate.
Quality Costing: The Findings from an Industrial-Based Research Study in Coating Manufacture
Authors: Pursglove A B , Dale B G
Published: February 2007

A study has been made over a period of four years of the use of quality costing by three individual manufacturers of coatings for industrial and decorative use. The experience indicates that differences in manufacturing processes, products, markets and systems all combine to prevent one company's quality costing system from being used effectively by another. It was found that the establishment of a reliable and well-developed management information system is of considerable importance to the establishment of a quality costing system. It is also pointed out that the early reporting of some costs such as internal and external failure in advance of the development of a complete quality costing system was found to be beneficial in getting the concept of quality costing accepted and making good use of the data.
Development of Product and Process Comparison Criteria for an Intelligent Knowledge-Based System for Forging Die Design
Authors: Bakhshi-Jooybari M , Pillinger I , Dean T A , Hartley P
Published: February 2007

An important feature of any intelligent knowledge-based system (IKBS) for the design of forging dies is the ability to compare new components with those previously encountered by the system. In order to accomplish this, it is necessary to identify the parameters that significantly influence the success or otherwise of the forging and the weighting effect of these parameters. An experimental method has been developed to obtain the weighting effects of different process and geometrical parameters in completely closed-die forging. The results have been implemented in the IKBS and are shown to be capable of assessing the suitability of proposed forging die sequences.
A Gravity Compensation Technique for an N-Legged Robot
Authors: Channon P H , Hopkins S H , Pham D T
Published: February 2007

Steady state errors resulting from gravitational loading are significant in legged robots, particularly when controller gains are set to low values to achieve the desirable property of compliant legs. This paper presents a gravity compensation scheme which not only eliminates steady state errors but which also generates foot reaction distributions that are optimal in terms of minimizing the likelihood of foot constraints being broken. This is achieved by minimizing a cost function, designed to reflect the condition of foot constraints, in conjunction with the equations of static equilibrium for the robot. A method of performing the minimization based on a combination of an analytical and a Newton—Raphson technique is presented. Results are given for hexapod and biped simulation models and for an experimental biped.
The Solution of Crack Problems by Using Distributed Strain Nuclei
Authors: Korsunsky A M , Hills D A
Published: February 2007

Crack problems may be solved by first establishing the stress field in the crack's absence and distributing strain nuclei along the line of the crack in order to render its faces traction-free. The relationship between the different possible forms of nucleus and the kinds of singular integral equation to which they lead are explored. The merits of each are then highlighted.
The Characterization of Mixed-Mode Energy Release Rates in Orthotropic Materials
Authors: Walker C A , Jamasri
Published: February 2007

The aim of this work was to predict, from the material constants, mixed-mode energy release rates in orthotropic materials, in particular the general cases in which the crack is aligned at a random angle to the principal material direction, normal to the plane of orthotropy. Two-dimensional finite element models with various fibre orientations were generated. The finite element models were validated by comparing two sets of contour plots of deformation, one resulting from the finite element analysis and the other from moiré interferograms of the experimental work. On comparison there was shown to be a strict similarity between experimentally determined and computational deformation fields.

Variations of the energy release rates were investigated for both rapid and stable crack growth. This was accomplished by generating two-dimensional stable crack growth finite element models. In general, energy release rates were found to be strongly affected by the fibre orientation. An increase of the angle of the crack growth direction caused a decrease of the mode I energy release rate and, by contrast, an increase of the mode II energy release rate, but the mode II energy release rate was always a small fraction of the mode I value.

Crack extension caused a gradual increase of the mode I energy release rate both for coplanar and non-coplanar crack growth. However, there was no significant effect found on the mode II energy release rate.
Theoretical Analysis of Damping Properties of two-Degree-of-Freedom Linear Vibrational Systems
Authors: Popov G
Published: February 2007

Analytical solutions for complete two-degree-of-freedom (2 DOF) vibrational systems comprising primary and secondary resilient and damping elements and subjected to a harmonic base excitation are obtained for the first time and presented in terms of transmissibility of primary and secondary mass and resonance and invariant frequencies of primary mass, which is considered to be the object of isolation. Analytical expressions for optimum values of main system parameters including primary and secondary dampings, mass ratio and secondary and primary springs stiffness ratios are also newly presented. Damping properties of systems are analysed for the case of a constant optimum damping, which minimizes the primary mass transmissibility at the lowest resonance frequency, and for the case of frequency-variable optimum damping, providing the minimization over the entire range of forced frequency. The expressions for optimum primary and secondary dampings are given in the form of quadratic algebraic equations for the case of complete 2 DOF systems. The influence of the mass and spring stiffness ratios on the system response is investigated as well. The obtained results, being of a general nature and obtained for large ranges of main parameters, can be applied to different classes of vibration isolation problems, such as isolation of a large item of machinery, a light piece of instrumentation or a ground vehicle.
A Technique for Experimental Acoustic Modal Analysis
Authors: Whear F R , Morrey D
Published: February 2007

A technique developed to carry out experimental acoustic modal analysis using commercially available structural modal analysis software is described. This uses a finite difference calculation to determine the spatial variation in pressure. In order that the resulting function exhibits the same nodes and antinodes as the actual pressure distribution at resonance, a second-order finite difference calculation is performed to obtain the second spatial derivative. This is implemented in practice using a three side-by-side microphone probe with an analogue differential amplifier.

The technique is verified by measuring the natural frequencies and mode shapes of a bare rectangular office. These results are compared with analytical calculations and output from a finite element model. The results show very good agreement for all modes in the frequency range of interest.
A Variational Approach To The Optimization of Gait For a Bipedal Robot
Authors: Channon P H , Hopkins S H , Pham D T
Published: February 2007

This paper presents a method for optimizing the walking motions of a planar five-link biped. The technique starts with non-linear kinematic and dynamic models for both the single-support and impact stages of motion. A variational technique is then used to derive joint trajectories that minimize a simple cost function. The resulting two-point boundary value problem is solved using a finite difference technique, with trajectories obtained from a simple linearized model as initial conditions. Families of optimal trajectories for different step periods and step lengths are presented.
Gear Transmission Error Measurement Using Phase Demodulation
Authors: Sweeney P J , Randall R B
Published: February 2007

Gear manufacturers in all fields of industry are under increasing pressure to deliver products of high accuracy and which generate ever lower levels of vibration and noise. Over the past decades, transmission error (TE) measurement has become more popular as a means of measurement for research and quality control. However, dedicated measurement systems have often proved incapable of measuring TE under operating conditions.

This paper presents an overview of TE measurement techniques and their applications. In addition, an introduction to a versatile and portable method of measurement based on FFT analysis and demodulation is given. This method is easily implemented using current generation FFT analysers or signal analysis software, and is suitable for research, diagnostics, condition monitoring and quality control applications alike.
Calculation of Pressure Wave Propagation Through a Tube Junction
Authors: William-Louis M J P , Tournier C
Published: February 2007

This paper describes a new method for the calculation of pressure wave propagation through a junction. The unsteady model, valid for subsonic flow, takes into account the fluid compressibility and pressure losses according to the type of junction. A new method called the ‘branch superposition method’ is used for the numerical calculation, and consists of uncoupling the system of governing equations. During the propagation of pressure waves through a three-tube junction, two branches are inlet or outlet. Therefore, to uncouple the system, one of the two branches with incoming flow is modelled as a source or one of the two branches with outgoing flow as a sink. This method, combined with the method of characteristics, gives the possibility of predicting the propagation of pressure waves through a junction, where the fluid may be initially at rest or not. The model is validated by a comparison with experimental results.
Polishing and Honing Processes: An Investigation of the Thermal Properties of Mixtures of Polyborosiloxane and Silicon Carbide Abrasive
Authors: Fletcher A J , Fioravanti A
Published: February 2007

The passage of an ultrasonic wave through a mixture of polyborosiloxane and silicon carbide abrasive, when used in a honing process, causes heating due to the attenuation of the said wave. This is critical to the honing process since the temperature in the components being treated must be limited to about 70° C. A numerical model of the heat generation and transfer processes in the polishing medium is being formulated, which requires knowledge of the thermophysical properties of the mixture.

This investigation concentrates on the experimental determination of thermal conductivity, specific heat capacity and surface heat transfer coefficient for various mixtures of polyborosiloxane and silicon carbide abrasive. Theoretical, semi-empirical and empirical models are derived for the variation of these thermal properties as functions of both material composition and temperature.
On the Vibration of a Nearly Cyclic System
Authors: Wu G F , Liu X J
Published: February 2007

In this paper, the vibration modes of the structural model of a nearly cyclic multiply mono-coupled multi-degree-of-freedom (multi-DOF) component assembly are examined. The attention is focused on the mode similarity phenomenon among the vibration deformation shapes of all the components for the disordered assemblies with relatively weak coupling. By means of this particular characteristic of the normal modes of such a system, an effective solution method based on the analysis of a single component system is developed, which can be used to find any specified structural frequency within any given frequency band and its corresponding mode of the system directly. This solution scheme, in a new perspective, provides a direct physical insight into the relation between the imperfection effects and the various structural and imperfection parameters. Numerical examples are given at the end.
A New Approach to The Design of Fan Volute Profiles
Authors: Qi D T , Pomfret M J , Lam K
Published: February 2007

In traditional volute design methods, the flow at the volute inlet is assumed to be uniform according to one-dimensional theory. However, many experimental results have shown that under the design operating conditions, the actual distributions of the flow parameters at the volute inlet are different from those predicted by the ideal assumption. This is because of the influence of the non-axisymmetrical volute geometry, especially due to the presence of the volute tongue. Based on this fact, a new method was considered whereby different volute profiles can be generated by varying the distributions of flow parameters at the volute inlet. The ultimate objective is to achieve the optimal volute profile design so that the performance of a centrifugal machine can be improved. In this paper, a two-dimensional inverse method has been used to redesign the original volute profiles of two centrifugal fans. The results show that the method presented provides effective improvement to the one-dimensional volute design method. The controlled distribution form of volute inlet flow angle α4 in the redesign is qualitatively discussed and can be used for reference in the volute design and further research.
Measurements of Thermal Performance of the Regenerator of a Cryocooler with a high Number of Transfer Units Value
Authors: Chen P-H , Chang Z-C
Published: February 2007

Hundreds of stacked wire screens are used in the regenerator matrix of a common cryocooler. The number of transfer units of such a matrix (denoted as NTUm) may well exceed 60. However, most of the earlier studies reported are limited to studies of regenerators with NTUm values less than 60, as the single-blow method was employed to measure the NTUm value of the regenerator matrix. Furthermore, in these earlier studies, the effect of heat transfer from the working fluid to the external tube and the Joule-Thomson effect were neglected.

In the present study, three regenerators having high NTUm values have been constructed and a transient single-blow technique has been employed to measure the friction factor and the heat transfer performance of these regenerators. In addition, an improved model has been adopted to correct the shortcomings of the earlier studies.

Empirical correlations have been provided for the relation between the friction factor and Reynolds number and between the Nusselt number and Reynolds number. The correlation with smaller NTUm values agreed well with those reported in earlier studies.
An Efficient Robust Adaptive Control Law For Robot Manipulators
Authors: Yu H , Lloyd S
Published: February 2007

A computationally efficient robust adaptive control algorithm is proposed in this paper. The regressors are implemented using the desired trajectories to replace the actual trajectories in order to reduce the computational burden. To reduce the disturbance introduced by this replacement, an adaptive variable structure control law is proposed. The proposed adaptive control law results in a system that is robust to bounded input disturbances. A small modification of the control law makes the system robust to more general input disturbances. The stability analysis is in the Lyapunov sense. Simulation results demonstrate the validity of the proposed scheme.
Modelling Study of the Scavenging Process in a Turbocharged Diesel Engine with Modified Valve Operation
Authors: Benajes J , Reyes E , Luján J M
Published: February 2007

The instantaneous gas exchange process in a turbocharged direct injection diesel engine with an intake valve pre-lift and an exhaust valve post-lift has been studied in detail by means of a wave action model. Such a modified valve timing operation allows the internal exhaust gas recirculation and the residual burnt gas ratio in the combustion chamber to be increased and modulated. A simple scavenging model has been included in the global calculation code, in order to obtain information on the instantaneous composition of the gas flow across valves. The analysis sheds light on the intricate flow phenomena produced by the additional valve lift periods, and evaluates the potential of this technique in the control of the residual burnt gas in the cylinder.
Identification of the Unbalance Distribution and Dynamic Characteristics of Bearings in Flexible Rotors
Authors: Lee A-C , Shih Y-P
Published: February 2007

This paper presents a new method for estimating dynamic characteristics of bearings and unbalance distribution in flexible rotors based on the transfer matrix method for analysing the steady state responses of rotor-bearing systems, in which rotary inertia, gyroscopic and transverse-shear effects are also considered. Identification can be realized from the measured response data influenced by bearing characteristics and rotor unbalance using the least-squares method. Justification of the method is presented by numerical simulations.
The Dynamics of a Vibrating Cylinder Gyro with Imperfection
Authors: Fox C H J
Published: February 2007

This paper presents an analysis of the mechanics of a vibrating cylinder rate gyroscope including the effects of structural imperfection which is inevitably present in a real device. Imperfection has important consequences for the vibration properties of the cylinder which affect gyro performance. Interaction between imperfection and externally imposed motion of the cylinder gives rise to a number of potential error mechanisms which are identified and analysed. Analytical expressions are developed by means of which the error mechanisms are quantified in a practically useful way.
Buoyancy-Induced Flow Through a Narrow Chamber Containing an Internal Heat Source: Comparison of Experimental Measurements and Numerical Simulations
Authors: Baskaya S , Gilchrist A , Fraser S M
Published: February 2007

Natural convection ventilation of a rectangular chamber containing a heated rectangular body has been investigated both experimentally and computationally. The heated square blockage within the partial enclosure was adjacent to the adiabatic lower surface of the chamber and the three exposed surfaces of the block were such as to give a constant heat flux. The air inlet and outlet were located at the bottom and top of the chamber vertical walls respectively, and were of equal area. Velocity measurements were performed using laser Doppler anemometry (LDA) with a one-component He–Ne laser connected to a burst spectrum analyser (BSA). Detailed velocity profiles were measured at the inlet, outlet and at several locations inside the chamber. Temperatures of the heated air at the outlet were measured with a chromel–alumel (type K) bare wire thermocouple probe. Three-dimensional laminar and turbulent (k–e model) numerical simulations were obtained by solving the governing equations using the computational fluid dynamics (CFD) code PHOENICS. Comparisons of experimental and computational results showed very good agreement in most of the flow field.