bluuebunny/crossref_metadata_2025 huggingface dataset:
Visibility: An application to a probe's definition
Authors: Dépincé P
Published: October 2002

Accessibility of measured points to touch probes is crucial in planning dimensional inspection of mechanical parts by a coordinate measuring machine (CMM). This paper presents a method used to define the kind of touch probe needed to measure the various points of a mechanical part. The proposed method is based on the notion of visibility. The limits of the notion of visibility as it is usually defined for machining purposes are shown. A new definition of visibility is proposed, dedicated to measurement. A method allowing determination of the probe's characteristics (maximum length of the stylus, sufficient number of styli) is described.
Aspects of cooling lubrication reduction in machining advanced materials
Authors: Brinksmeier E , Walter A , Janssen R , Diersen P
Published: October 2002

Coolant lubricants are recognized as undesirable factors in metal cutting, especially in machining advanced and difficult-to-cut materials. For both economic and ecological reasons, as well as because of increasing legislation, efforts are being made to reduce the use of coolants. On account of this, the introduction of dry machining and minimum quantity lubrication (MQL) techniques in machining processes is increasing. The results of the investigations carried out give an overview of the possibilities for influencing the machining of advanced materials, e.g. titanium alloys and extreme low-sulphur steels. The research topics focus on cutting tool performance and wear mechanisms at high cutting speeds while using different lubricants and cooling supply strategies. The investigations and verification experiments contribute to increasing process stability and tool life, improvement of machined surface finish and avoidance of tensile residual stresses.
Tapered-web helical groove machining
Authors: Chyan H C , Ehmann K F
Published: October 2002

Most of the existing, mainly graphics-based, approaches to helical groove machining lack generality since they rely on restrictive machining methods, are designed for special applications and are difficult to use in practice. Therefore, helical groove machining is still predominantly approached from an empirical trial-and-error standpoint by most manufacturers in current industry. In this paper, the formulation of a general analytical approach for tapered-web groove machining is presented, which lends itself to computer aided design (CAD) implementations. In this regard the mathematical foundation and examples of different groove machining tasks will be presented.
Finite element computer investigation of the electrochemical machining process for a parabolically shaped moving tool eroding an arbitrarily shaped workpiece
Authors: Hardisty H , Mileham A R
Published: October 2002

This paper describes a computational investigation into the electrochemical machining (ECM) process for the case of a tool of fixed parabolic shape, moving at a uniform speed while eroding a stationary work surface initially of arbitrary shape. The numerical simulation of this two-dimensional moving boundary problem is based on the finite element method (FEM). The improved algorithms presented here, which model the erosion process at the work surface, remove certain limitations of the previous square mesh method. In ECM, as time increases, the eroded surface approaches more closely to an equilibrium shape. One-dimensional ECM theory is briefly reviewed in order to provide a background to the physical factors which influence this equilibrium state. A general equilibrium criterion is derived which is first used as part of a check on the test data, and later made the basis of an iterative design method.

The present paper is divided into two sections. In the first, the modular computer package, which simulates the continuous erosion process, is described. A parabolically shaped tool was selected to allow the final equilibrium work shape generated after a number of time steps to be checked. These checks demonstrated excellent agreement between computer predictions and theory; they constitute a successful validation of the methodology. In the second part of the paper, the inverse of the above process is considered. Algorithms are described which, starting from the specified work shape, iteratively generate the tool shape required to produce that work shape. This avoids the multiple trial and error runs normally associated with the evolution of a tool shape in practice.
Reliability assessment of a digital electronic board assembly using the physics-of-failure approach: A case study
Authors: Oguibe C N , Williams D J
Published: October 2002

An independent study has been carried out to assess the extent to which the physics-of-failure (PoF) technique can help in reliability enhancement and assessment of electronic assemblies. In particular, a specific case study has been conducted on a real, digital electronic board assembly with known failure modes. Results from the study include the simulation of substrate and component temperatures based on the knowledge of component power dissipation, board assembly materials and cooling methods of the board assembly. The fundamental frequencies and dynamic displacements of the board were computed from the vibration models. The thermal and vibration results were then used to model the damage accumulation at solder joints of the components to accurately predict failure trends and failure sites. These results are compared with field failure data and results from other computer aided engineering (CAE) tools.
Detection of tooth breakage in end milling using machine tool axis control signals
Authors: Johns C , Prickett P W
Published: October 2002

This paper considers the feasibility of utilizing existing machine tool axis drive control signals as a mechanism for the early identification of tool breakages. In particular the paper outlines the utilization of axis tachometer feedback signals as a means of monitoring the cutting process of a computer numerical control vertical milling machine. The work describes how a fault signature, corresponding to a tool breakage, can be identified in the axis tachometer signals at varying feed rates.

The results of the preliminary testing of a monitoring system utilizing existing axis feed drive signals are presented. The paper then outlines steps being taken to develop the application of the method to an increased range of cutting conditions. This work was based upon a study of the interrelationship between the axis control signals when cutting is proceeding in either the X - or the Y -axis direction, and when both the X axis and the Y axis are feeding simultaneously.
Study and selection of grinding conditions Part 1: Grinding conditions and selection strategy
Authors: Li Y , Rowe W B , Mills B
Published: October 2002

This paper is in two parts describing the study and selection of grinding conditions. This first part is concerned with the study of grinding conditions and selection strategy. Grinding is a complex manufacturing process with a large number of interacting variables. Before designing the selection system, it is necessary to define the variables and to find which variables should feature in the selection process. Consideration is therefore given to the relationships and interactions between these variables. The study is limited to the external cylindrical plunge grinding operation. Existing techniques employed to deal with the selection of grinding conditions are investigated, including data retrieval methods, empirical models and artificial intelligence methods. Finally, a blackboard strategy is presented for the selection of grinding conditions. The knowledge agents consist of case-based reasoning, neural network reasoning and rule-based reasoning.
Classification approaches for standard parts to aid design reuse
Authors: Culley S J
Published: October 2002

Standard components or parts make up a large proportion of engineering assemblies and systems. They are increasingly chosen from what is known as the electronic catalogue. These are being developed with the use of a variety of techniques to enable the reuse of both the part and the experience associated with that part. This paper deals with the current state of these techniques and the additional ones being developed, e.g. considering systems and assemblies, classification and knowledge-based methods. It is considered that these new methods will ultimately enable the more generic exploitation of design reuse.
Modelling with gradient information
Authors: Malik Z , Dyck D , Nelder J , Spence R , Lowther D
Published: October 2002

Response surface models (RSMs) can be used to model expensive simulations or real measurements [1]. An RSM is constructed by simulating solutions at systematic points in a design space and fitting a model to them. The RSM is then employed in subsequent calculations (for instance in optimization) effectively replacing the original expensive simulator, which leads to considerable savings in time and money. A novel technique is presented here which uses the gradient of a function as well as the function itself to construct the RSM. Such an approach is possible because, for many types of simulations, gradient information is simple and cheap to obtain.

The design of an electromagnetic speaker assembly is used to illustrate the new approach. The finite element method (FEM), on which the simulation is based, can provide gradient information at little extra cost and hence the benefits of using gradient information are considerable, being especially marked in higher-dimensional spaces.
An investigation of the roles of crack initiation, propagation and ratchetting in producing wear in metallic sliding contacts
Authors: Liu J , Kopalinsky E. M. , Oxley P. L. B.
Published: October 2002

Experiments are described in which the edge of a hard wedge is loaded against the periphery of a rotating disc of softer specimen material. The normal and frictional forces and inward movement of the wedge as the disc wears are continually monitored throughout a test. The results obtained are used together with measurements of the wearing surfaces of metallographic sections to test a newly proposed wear model. In this model it is assumed that ratchetting causes failure of the surface and hence the production of wear particles, while low-cycle fatigue determines the crack propagation rate and hence the wear rate.
Non-destructive examination of adhesively bonded structures using dielectric techniques: Review and some results
Authors: Affrossman S , Banks W. M. , Hayward D , Pethrick R. A.
Published: October 2002

The use of high-frequency dielectric measurements is described for the non-destructive evaluation of adhesively bonded structures. Frequency domain measurements have been used to monitor the ingress of moisture into the joint structure. A good correlation has been observed between the data obtained from gravimetric and dielectric measurements. On prolonged exposure to water, changes occur to the surface oxide in the case of aluminium/aluminium joints to produce a surface hydroxide. The conversion process of oxide to hydroxide has a distinct dielectric signature. A correlation is observed between the changes in the failure mechanism and the variation in the dielectric profile. Time domain data have been used to investigate the integrity of the pristine bonded structure and the changes that occur on ageing. Examples of the application of the technique to both the aluminium and to carbon fibre/carbon fibre bonded structures are presented. The sensitivity of the technique to the occurrence of defects is critically discussed. A method for the study of bonds using a non-contacting method is outlined.
Precision forging
Authors: Dean T. A.
Published: October 2002

The manufacture of forgings to precise dimensional form and with specified mechanical and metallurgical properties has been the aim of industry since the industrial revolution. Developments towards this objective have been continual over the years as companies have sought commercial advantage in markets where competition from other industries such as foundry, powder metallurgy, sheet metal and fabrication is increasingly fierce.

This paper starts with a brief review of historical milestones in the development of forging up to the first half of the twentieth century. The last 50 years have been a period of great activity in the establishment of a science base for forging technology and the development of cold, warm and hot processes with associated equipment to enable industry to provide components of greater complexity, increasing accuracy and nearer to net shape and research in the present author's laboratory has contributed to the advances in many areas. The major thrusts have dealt largely with improved tool designs and coatings for greater accuracy and longevity, techniques to enable metal to flow into die cavities of complex geometries and methods for complete process control, from raw material to product despatch. This paper attempts to highlight significant aspects of the technological developments which have been the result of world-wide activities. To give a coherent picture the steps of knowledge acquisition which have supported technological advancement are described using mainly the results of work from the present author's laboratory.
Forging preform design using a reverse simulation approach with the upper bound finite element procedure
Authors: Chang C. C. , Bramley A. N.
Published: October 2002

Forging preform design, which is a critical step when making forging products, is still performed by experience-based methods or trial-and-error approaches with or without computer simulations. To improve this time consuming task and to establish a systematic forging design method, a reverse simulation approach is proposed. The reverse simulation starts from the finished shape, with boundary areas being released as dies are moved backwards. The simulation is based on the upper bound method with the finite element procedure being used to find a velocity field representing the minimum energy required for plastic deformation. A measure of the material distribution is proposed to evaluate the complexity of the shape, which aims to ensure that the reversed shape becomes a simple geometry. The control of the boundary conditions, i.e. a strategy of releasing contact areas, is also presented. Forward simulations performed by a validated commercial modelling package are used to assess the predicted preform. The results demonstrate that the proposed approach has a considerable potential in the preform design for the forging industry.
Multi-body dynamics: Historical evolution and application
Authors: Rahnejat H
Published: October 2002

The historical developments in the discipline of engineering dynamics are briefly reviewed, with attention paid to the formulation and solution of the dynamic behaviour of multi-body systems. It is shown that the dynamic characteristics of practical multi-body systems are dependent upon the interactions of many physical phenomena that can induce, restrain or constrain motion of parts. The long process of understanding and formulating the physics of multi-body motions, in some cases with pioneering contributions centuries old, together with continual refinements in numerical techniques and enhanced computing power has resulted in the solution of quite complex and practical engineering problems. Linking the historical developments to the fundamental physical phenomena and their interactions, the paper presents solutions to two complex multi-body dynamic problems. The practical implications of the approach in design of these systems are highlighted.
The unsteady stokeslet and oseenlet
Authors: Chan A. T. , Chwang A. T.
Published: October 2002

The unsteady low Reynolds number flow of an incompressible viscous fluid past a singular forcelet is investigated analytically. New fundamental three-dimensional solutions for a concentrated impulsive force are derived for the Stokes and the Oseen equations. These elementary solutions can be used as fundamental Green's functions to obtain solutions for flows over singularities with any time-dependent nature. The fundamental singularities are employed to construct some well-known solutions to demonstrate their validity and usefulness in solving unsteady problems governed by the Stokes and the Oseen equations. A new solution is presented for an unsteady Oseen flow with a constant acceleration.
Fluid power systems—some research issues
Authors: Burrows C. R.
Published: October 2002

Traditional areas of application of fluid power systems are being challenged by alternative forms of energy transmission. In some cases this is because of environmental concerns associated with noise and leakage, in other applications the lack of systematic design methods for synthesizing fluid power systems has led to their replacement by electrical drives. This paper outlines some of the current research studies motivated by these challenges.
Compressor blade leading edges in subsonic compressible flow
Authors: Tain L , Cumpsty N. A.
Published: October 2002

The flow around the leading edge of a compressor blade is interesting and important because there is such a strong interaction between the viscous boundary layer flow and the inviscid flow around it. As the velocity of the inviscid flow just outside the boundary layer is increased from subsonic to supersonic, the type of viscous-inviscid interaction changes; this has important effects on the boundary layer downstream and thus on the performance of the aerofoil or blade.

An investigation has been undertaken of the flow in the immediate vicinity of a simulated compressor blade leading edge for a range of inlet Mach numbers from 0.6 to 0.95. The two-dimensional aerofoil used has a circular leading edge on the front of a flat aerofoil. The incidence, Reynolds number and level of free-stream turbulence have been varied. Measurements include the static pressure around the leading edge and downstream and the boundary layer profile far enough downstream for the leading edge bubble to have reattached. Schlieren pictures were also obtained. The flow around the leading edge becomes supersonic when the inlet Mach number is 0.7 for the zero-incidence case; for an inlet Mach number of 0.95 the peak Mach number was approximately 1.7.

The pattern of flow around the leading edge alters as the Mach number is increased, and at the highest Mach number tested here the laminar separation bubble is removed. Positive incidence, raised free-stream turbulence or increased Reynolds number at intermediate inlet Mach numbers tended to promote flow patterns similar to those seen at the highest inlet Mach number. Both increased free-stream turbulence and increased Reynolds number, for the same Mach number and incidence, produced thinner shear layers including a thinner boundary layer well downstream.

The measurements were supported by calculations using the MSES code (the single aerofoil version of the MISES code); the calculations were helpful in interpreting the measured results and were demonstrated to be accurate enough to be used for design purposes.
A computer algebra-based coordinate reduction technique for multi-body systems
Authors: Chochia G A , Chawdhry P K , Burrows C R
Published: October 2002

This paper presents a heuristic algorithm to solve the linear coordinate reduction problem. If Cartesian coordinates are chosen in the initial formulation the algorithm eliminates two-thirds of dependent coordinates in the planar case and one-half in the spatial case for mechanisms composed of spherical, revolute and universal joints. For an open-loop system composed of spherical joints it eliminates all dependent coordinates. A computer algebra-based implementation in the Maple language is presented. The proposed technique is demonstrated by application to the dynamic analysis of a Peaucellier mechanism.
The structural characteristics of microengineered bridges
Authors: Burdess J S , Harris A J , Wood D , Pitcher R
Published: October 2002

The paper considers the measurement of Young's modulus and internal stress in micro-engineered bridge structures. Values determined from the results of static tests, obtained from the measurement of compliance using a nanoindenter, are compared with values derived from natural frequency measurements obtained from dynamic testing using a laser vibrometer. Both test procedures use mathematical models ‘fitted’ to experimental data to estimate Young's modulus and internal stress. For the case of boron-doped silicon bridges the dynamic test method is shown to produce the superior estimates.
Design of H∞ loop-shaping controllers for fluid power systems
Authors: Njabeleke I A , Pannett R F , Chawdhry P K , Burrows C R
Published: October 2002

Fluid power systems are highly non-linear, making the application of traditional linear feedback control techniques challenging. In this paper, a dual-mode H∞ control scheme has been proposed and demonstrated to be both feasible and practical for controlling such systems. The plant used is a speed control hydrostatic transmission and the particular H∞ approach used is loop shaping as suggested by McFarlane and Glover; this, in addition to simplicity, admits a wider class of uncertainties than comparable schemes. The dual-mode controller is surprisingly effective, delivering robust stability over the entire speed range and offering bumpless transfer, wind-up protection and multi-rate sampling at little extra cost, a factor which is crucial in digital implementation. It is shown that, despite some challenges, a successful H∞ controller need not be of high order.
The spring-and-lever balancing mechanism, George Carwardine and the Anglepoise lamp
Authors: French M J , Widden M B
Published: October 2002

Two short and direct methods of exact analysis of the spring-and-lever balancing mechanism are presented. It is shown that perfect balance can be achieved by the use of a close-coiled spring whose free length is effectively zero and whose stiffness is chosen appropriately. The two-degree-of-freedom balancing mechanism, commonly seen in desk lamps but useful in many other situations, is then analysed. The treatment is extended to allow for the weight of the components of the mechanism itself.

The originator of these devices was George Carwardine, whose patents over the period 1931–35 show the evolution of his ideas on this subject. A short biographical note is included as an appendix.
Dynamical behaviour of a torsional system with parametric and external excitations
Authors: Adiletta G , Guido A R
Published: October 2002

The dynamic behaviour of a torsional system with a one-cylinder, reciprocating compressor driven by an asynchronous motor is studied using a two degrees-of-freedom (2 DOF) lumped-parameter theoretical model. The model takes into account the variability of the mass moment of inertia of the crank mechanism and the presence of pressure forces loading the compressor piston. The influence of the ratio of the variable to the constant part of inertia in the crank mechanism and the effect of the load torque due to pressure forces acting on the piston are examined in relation to system dynamic behaviour. Experimental data, obtained with the adoption of a suitable rig, show that the theoretical indications can be considered reliable, despite the approximation that was given to the mathematical model as far as the treatment of the damping and the absence of clearances were concerned.
Stylus damage prevention index
Authors: Whitehouse D J
Published: October 2002

Stylus methods for measuring surfaces have sometimes been blamed for causing damage to the surface because of the stylus pressure. This paper investigates this possibility and develops a ‘potential damage index’ which takes into account the instrument parameters, static and dynamic, and surface parameters. All types of surface are considered, both periodic and random. The paper shows that the stylus method is often misjudged, that stylus damage is rare and that any damage observed is likely to be due to the operation of a skid in the instrument.
Passive voice coil feedback control of closed-box subwoofer systems
Authors: Chen C-Y , Chiu G T-C , Cheng C-C , Peng H
Published: October 2002

In this paper, the feasibility of using a voice coil back-electromotive voltage (back-e. m.f.) signal as feedback information for closed-loop control was investigated. A dual voice coil closed-box subwoofer system is used to demonstrate the effectiveness of back-e. m.f. feedback control. A second-order filter is developed to extract the velocity information from the coil back-e. m.f. signal. A pro-portional-plus-derivative (PD) controller is well suited for reducing the harmonic distortion and extending the subwoofer bass response. Experimental results verified that the proposed control scheme effectively extended the bass response of the subwoofer system by one octave and at the same time reduced harmonic distortion by more than 6dB. The proposed feedback and control scheme can be easily implemented using inexpensive analogue components, which can further reduce the cost and complexity of the system.
Electron kinetic theory approach for sub-nanosecond laser pulse heating
Authors: Yilbas B S , Shuja S Z
Published: October 2002

Laser short-pulse heating initiates non-equilibrium thermodynamic processes in the surface vicinity of solid substrates that are subjected to the pulse heating. The Fourier heating model, however, overestimates the temperature rise in this region. Consequently, it becomes essential to consider a heating model employing a microscopic level energy exchange mechanism in the surface vicinity. In the present study, electron kinetic theory, Fourier theory (one-equation model) and a two-equation model are introduced for sub-nanosecond laser heating pulses. The effect of laser pulse intensity on the temperature rise is also considered. The equations resulting from the models are solved numerically for gold and chromium substrates. The predictions are validated for a triangular pulse and a silicon substrate. It is found that electron kinetic theory and a two-equation model both predict lower temperatures in the surface vicinity at early heating times. As the pulse heating progresses, the predictions of both models converge to the result of a one-equation model.
The application of wavelets to reacting flows
Authors: Prosser R , Cant R S
Published: October 2002

The prospects presented by wavelets in the numerical analysis of chemically reacting turbulent flows are examined. In many flows of industrial relevance, combustion takes place in a stream of turbulent premixed gases. The mode of combustion is said to lie in the laminar flamelet regime. When a combustion process belonging to this regime occurs, it is anticipated that the flow field will be split into two components: reactants, consisting essentially of the fuel-air mixture, and products, typically consisting of carbon dioxide, water vapour, nitrogen and a number of other trace species. The two regions are separated by the flame, which is typically a very small-scale structure containing all of the chemical and molecular transport effects. The length scale disparity between the thin flame and the flow domain as a whole makes efficient discretization with traditional methods difficult, but is ideally suited to the multiresolution paradigm. In this paper, the current state of the art in the application of wavelets to the discretization of turbulent combustion problems is explored. The limitations of the present approaches as well as their strengths are assessed and outstanding problems from both a theoretical and a practical point of view are discussed. Key research directions for future investigations are highlighted.
Effect of final drawing with light reduction on the levelling of residual stress distribution in cold bar drawing
Authors: Kuboki T , Akiyama M , Neishi Y , Kuroda K
Published: October 2002

A method is proposed for producing a significant reduction in the magnitude of the residual stress generated after cold drawing of a bar. It consists basically of a skin pass at the final stage of drawing and has a good levelling effect on the residual stress distribution as long as the final reduction falls within a specific range. The method was first proposed as a result of elastic-plastic finite element analyses using the ELFEN code developed by Rockfield Software Limited at the University of Wales, Swansea. The validity of the proposed method was verified by measuring the residual stress using the Sachs method.
A direct approach to analysing step changes
Authors: Kubie J
Published: October 2002

There are many processes in engineering in which a physical parameter y normally varies linearly with another physical parameter x, but where, on occasion, a step change in the variation of parameter y may occur. A typical example of this phenomenon is the variation of the pressure drop along an obstructed straight pipe. It is the purpose of this paper to develop a direct method for determining this step change and to consider the implications.
Fault-tolerant control of rotor/magnetic bearing systems using reconfigurable control with built-in fault detection
Authors: Cole M O T , Keogh P S , Burrows C R
Published: October 2002

Magnetic bearings now exist in a variety of industrial applications. However, there are still concerns over the control integrity of rotor/magnetic bearing systems and the ability of control systems to cope with possible faults that can occur during operation. Unless control systems can be developed that have the ability to maintain safe operation when the system is in a degraded or faulty state, then many, otherwise viable, magnetic bearing applications will remain unfulfilled. In this paper, a method is proposed for the design of a fault-tolerant control system that can detect and identify both incipient and sudden faults as and when they occur. A multivariable H∞ controller is reconfigured on occurrence of a fault so that stability and performance is maintained. A neural network is trained to identify faults associated with the system position transducer measurements so that the output from the neural network can be used as the decision tool for reconfiguring control. In this way, satisfactory control of the system can be maintained during failure of a control input. The method requires no knowledge of the system dynamics or system disturbances, and the network can be trained on-line. The validity of this method is demonstrated experimentally for various modes of sensor failure.
Multi-bladerow fan forced response predictions using an integrated three-dimensional time-domain aeroelasticity model
Authors: Sayma A I , Vahdati M , Imregun M
Published: October 2002

A non-linear integrated aeroelasticity system to predict the forced vibration response of aero-engine fans is presented in this paper. The computational fluid dynamics (CFD) solver, which uses Favre-averaged Navier-Stokes equations on unstructured grids of mixed elements, is coupled to a modal model of the structure so that the effects of blade flexibility can be accommodated. The structural motion due to unsteady fluid forces is computed at every time step and the flow mesh is moved to follow the structure so that the resulting flow unsteadiness is determined in a time-accurate fashion. Two fan forced response case studies are reported in detail. The first one deals with a high-pressure ratio fan, the excitation being due to the upstream variable-angle inlet guide vanes (VIGVs). The unsteady flow analysis with blade motion was conducted using a sector of three VIGVs and four rotor blades. The wake predictions were found to be in good agreement with the corresponding laser measurements. The flow was observed to be completely separated for high VIGV angles and the excitation encompassed several harmonics. The predicted rotor blade vibration levels were generally found to be within 30 per cent of the measured values. The forced response to upstream obstructions was studied in the next fan case study. Three whole bladerows, consisting of 11 struts, 33 VIGVs and 26 rotor blades, were modelled in full. The model also included a prescribed inlet distortion pattern so that the combined effects of stator wakes and inlet distortion on the response of the rotor blades could be studied. The unsteady flow calculations were conducted using a time-accurate non-linear viscous flow representation. Blade motion was also included. Such an undertaking required about 4.2 million grid points to include all three bladerows in a complete stage calculation. To reduce the computational effort, a number of smaller computations were conducted by considering the stator and rotor domains separately: the outflow solution of the stator domain was used as an inflow boundary condition to the rotor domain. The results indicated that such isolated bladerow computations were likely to under-predict the response levels because of neglecting rotor-stator interactions. A number of low engine order (LEO) harmonics were identified from an inspection of the unsteady forcing created by the inlet distortions. Good agreement was obtained for cases where experimental data were available.
Mechatronic strategies for torque control of electric powered screwdrivers
Authors: Althoefer K , Seneviratne L D , Shields R
Published: October 2002

The paper presents the results of a study on using mechatronics to enhance the performance and reliability of small electric powered screwdrivers (SEPS). A mechatronic solution to control the final tightening torque replacing the mechanical clutch of a purely electromechanical SEPS is presented. Torque estimation methods based on motor armature current measurements are integrated with an SEPS driven by a direct current motor. Strategies for controlling the final tightening torque of the screw fastening process are developed. The control strategies are tested in accordance with the ISO 5393 standard. It is shown that the mechatronic controller gives comparable performance to a SEPS with a mechanical clutch. The mechatronic solution has the advantage of reduced cost, size and complexity. The paper demonstrates the application of low-cost mechatronics in industrial power tools.
The dynamics of a vibrating-ring multi-axis rate gyroscope
Authors: Eley R , Fox C H J , McWilliam S
Published: October 2002

A novel, multi-axis rate sensor based on the vibration properties of a ring structure is presented. Vibrating ring structures have been used successfully to detect rates applied about the axis perpendicular to the plane of the ring using Coriolis coupling between in-plane displacements. The presented multi-axis sensor is capable of detecting rate applied about three mutually perpendicular axes using Coriolis coupling between in-plane and out-of-plane displacements. The steady state amplitude of the induced displacements are proportional to the applied rate. Coriolis coupling is only present for certain combinations of in-plane and out-of-plane displacement patterns, which allows a number of feasible concepts for two- and three-axis rate sensitivity.
The ideal gas Joule cycle at maximum specific work
Authors: Lewins J D
Published: October 2002

The condition for maximum specific work from a gas-turbine engine operated on a Joule cycle is generalized to ideal gases from the well-known result obtained by using a perfect gas. An obvious corollary is shown to be the principal theorem, when the working substance is an ideal gas with specific heat capacities varying with temperature, that the turbine outlet and compressor outlet temperatures are equal. Two additional corollaries are shown to hold in general. A simple study shows that the optimum condition point is not much affected by real departures from reversible behaviour. The condition for which a regenerative heat exchanger is then desirable is found. The results are generalized to any gas for which the enthalpy is a function of temperature only.
Characterization of acoustic emission signals from fatigue fracture
Authors: Shi Z , Jarzynski J , Bair S , Hurlebaus S , Jacobs L. J.
Published: October 2002

This paper discusses a comprehensive study that is developing a quantitative understanding of the acoustic emission (AE) signals that emanate from fatigue cracks. Two critical components of this study are the development of a transfer function that quantifies and removes geometric effects from a measured AE waveform and an experimental program that monitors and identifies AE signals that occur during the fatigue of cylindrical stainless steel specimens under torsion. Typical waveforms are collected during torsional fatigue and correlated with fracture mechanisms from different stages of testing. Three stages of fatigue are identified by AE waveform characterization and confirmed by microscopic replica observation. The other portion of this study demonstrates the effectiveness of using laser ultrasonic techniques to develop transfer functions to quantify and remove geometric effects from measured acoustic emission waveforms.
Crack detection in thick annular components using ultrasonic guided waves
Authors: Qu J , Berthelot Y. H. , Jacobs L. J.
Published: October 2002

This paper provides an overview of a study on circumferential guided waves in a thick annulus. Both steady state, time-harmonic waves and transient waves are considered. Several solution methods are reviewed and numerical solutions are presented for the propagation of ultrasonic circumferential waves in a thick, curved, two-dimensional annular waveguide. The modal content of the signal and the displacement profiles across the wall thickness are investigated. These studies provide valuable guidance in selecting optimal parameters for use in applications of the guided wave technique to the detection of cracks on the inner surface of annular components. Experimental results show that the technique can be used on parts with complex geometries (e. g. the pitch shaft of a helicopter) to detect cracks that would not be detectable by standard ultrasonic inspection.
Sensitivity analysis for the design and operation of a non-contacting mechanical face seal
Authors: Dayan J , Zou M , Green I
Published: October 2002

Detection and diagnosis of failure in non-contacting mechanical face seals may prevent catastrophes in some critical applications. Seal failure due to face contact may occur because of large relative misalignment between the seal rotor and stator faces. The objective of this work is to study the sensitivity of the relative misaligment to changes in the design and operational parameters of a non-contacting flexibly mounted rotor (FMR) mechanical face seal. These sensitivities can be efficiently exploited to prevent possible contact through proper selection of the seal parameters and working point in both the design and the control stages. Among the design parameters, the seal coning angle is by and large independent of other design requirements and should be properly selected to avoid contact. The operational variables greatly influencing the relative misalignment are the clearance, the bearing fluid pressure and the shaft speed. Where active control is considered, the relative misalignment sensitivity to changes in the control parameters should determine the working point. The sensitivity analysis is demonastrated using the data of an existing seal test rig.
Design for stereolithography
Authors: Pham D T , Ji C
Published: October 2002

This paper analyses the causes of errors in stereolithography with a view to deriving methods to compensate for those errors. Two types of errors are discussed: those due to the process of approximating the part and those arising during the building and finishing of the part. Design rules are proposed to reduce or eliminate both kinds of errors and thus increase the suitability of stereolithography as a technology for rapid tooling.
A particle image velocimetry study on the pulsatile flow characteristics in straight tubes with an asymmetric bulge
Authors: Yu S C M , Zhao J B
Published: October 2002

Flow characteristics in straight tubes with an asymmetric bulge have been investigated using particle image velocimetry (PIV) over a range of Reynolds numbers from 600 to 1200 and at a Womersley number of 22. A mixture of glycerine and water (approximately 40:60 by volume) was used as the working fluid. The study was carried out because of their relevance in some aspects of physiological flows, such as arterial flow through a sidewall aneurysm. Results for both steady and pulsatile flow conditions were obtained. It was found that at a steady flow condition, a weak recirculating vortex formed inside the bulge. The recirculation became stronger at higher Reynolds numbers but weaker at larger bulge sizes. The centre of the vortex was located close to the distal neck. At pulsatile flow conditions, the vortex appeared and disappeared at different phases of the cycle, and the sequence was only punctuated by strong forward flow behaviour (near the peak flow condition). In particular, strong flow interactions between the parent tube and the bulge were observed during the deceleration phase. Stents and springs were used to dampen the flow movement inside the bulge. It was found that the recirculation vortex could be eliminated completely in steady flow conditions using both devices. However, under pulsatile flow conditions, flow velocities inside the bulge could not be suppressed completely by both devices, but could be reduced by more than 80 per cent.
A six-component contact force measurement device based on the Stewart platform
Authors: Dai J S , Kerr D R
Published: October 2002

This paper describes the design of a six-component contact force measuring device, the purpose of which is to verify a system of theories that predict the forces found in robotic grasping. The geometry of the device is based upon that of the Stewart platform manipulator, configured symmetrically. The elastic properties of the device as a whole, and of its legs, are analysed and chosen so that the device possesses appropriate characteristics. The resulting design is described, and its calibration and use are reported. Particular attention is paid to the synthesis of the elastic properties of the system, including an elastic central strut to maintain tension in the legs, which themselves are designed for acceptable sensitivity. The whole device is shown to give good results in contact force measurements.
Analysis of a non-constant gap externally pressurized conical bearing with temperature and pressure dependent viscosity
Authors: Sinha P , Chandra P , Bhartiya S
Published: October 2002

The present paper analyses an externally pressurized non-constant gap conical bearing rotating with a uniform angular velocity. The lubricant is assumed to be incompressible and its viscosity varies with both pressure and temperature. Although the inertia effect due to lubricant flow has been neglected, rotational inertia is taken into account. The governing system of coupled momentum and energy equations, in conical coordinates, is solved numerically using the finite difference method, to determine various bearing characteristics. The effect of the viscosity-pressure exponent, , on various characteristics of the bearing has been studied. It is seen that variation of does not produce any significant change in the load capacity for convergent and constant gap conical bearings. For the divergent gap also, no significant difference is seen when the gap is slightly divergent. However, for highly divergent gaps, the load capacity increases with an increase in . It is also seen that variation in does not produce any significant change in torque of the bearing.
Analysis of the dynamic response of a fluid-supported circular elastic plate impacted by a low-velocity projectile
Authors: Huang W , Li Y , Chen W
Published: October 2002

In this paper, the dynamic response of a thin circular elastic plate supported by a fluid on one side and impacted by a low-velocity projectile on the other side is analysed for the first time. A semi-analytical method is put forward, a non-linear Volterra integral equation governing the impact force is deduced and a linear numerical method is used to solve the equation and calculate the transverse deflection of the plate. The presence of the fluid not only lowers, on account of increased inertia, the natural frequency of the plate vibrating in vacuum but also dampens its transverse vibration owing to the energy carried off in the form of sound waves. As a numerical example, the transverse deflection of a solid circular plate with clamped edges impacted centrally by a low-velocity sphere and the impact force are computed, and the results are discussed.
Thermomechanical fatigue characterization of zirconia (8%Y2O3-ZrO2) and mullite thermal barrier coatings on diesel engine components: Effect of coatings on engine performance
Authors: Ramaswamy P , Seetharamu S , Verma K B R , Raman N , Rao K J
Published: October 2002

8%Y2O3-stabilized zirconia (8YPSZ) and mullite (3Al2O3·2SiO2) powders, which were made plasma sprayable by using an organic binder (polyvinyl alcohol), have been plasma spray coated on to the piston head, valves and cylinder head of a 3.8kW single-cylinder diesel engine, previously coated with Ni-Cr-Al-Y bond coat. The engine with components coated with 250 μm thick 8YPSZ and 1 mm thick mullite thermal barrier coatings has been evaluated for fuel efficiency and for endurance during 500 h long rigorous tests. Improved fuel efficiency was shown by the engine with coated components and the results are discussed. The coatings and the coated components have also been examined for phases, microstructure and chemical composition by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). Mullite coatings were found to exhibit increased resistance to microcracking compared with 8YPSZ during the 500 h endurance test.
Boussinesq solution for solitary waves in uniform channels with sloping side walls
Authors: Teng M H
Published: October 2002

The analytical solution to the Boussinesq equations for solitary waves travelling in uniform water channels with sloping side walls is presented. Quantitative effects of channel cross-sectional geometry and channel side-wall slope at the waterline on the wave profile and wave speed, as well as the criteria for positive solitary waves to exist, are discussed. The new Boussinesq solution is also compared with the existing Korteweg-de Vries solution obtained by Peregrine. It is found that the two solutions are consistent for small amplitude waves while, for relatively large waves, the Boussinesq solution gives different predictions for wave speed and for the criteria for solitary waves to exist.
Third-order wave diffraction by a truncated circular cylinder
Authors: Kinoshita T , Bao W
Published: October 2002

The diffraction problem for a truncated circular cylinder is formulated up to the third order referring to the wave slope. The problem is solved by means of eigenfunction expansion. The Green function suitable for the pressure distribution problem is used to give a special solution which satisfies the inhomogeneous free-surface condition in higher-order problems. The special solution is expressed by an integral over the free surface and the singularity contained in the integrand is discussed. A new method to improve the convergence of the solution is proposed, which has the advantage of simplicity compared with the previous approach. A convergence test also shows satisfactory results. The third-order wave forces are evaluated and compared with the previous results.