bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement and diagnostics of machine tool errors during circular contouring motions
Authors: Kwon H D , Burdekin M
Published: October 2002

This paper deals with the measurement and diagnosis of the machine tool errors by application of the ball link bar system. It includes the development of a new link bar, the in-plane and out-of-plane measurement techniques and the machine error analysis system. The new type of ball link incorporates an idealized three-point kinematic contact principle between the balls and sockets of the link bar, and provides the following features: (a) the minimum length of the link corresponds to the minimum length of a standard LVDT transducer, (b) the link is of light weight, (c) the accuracy and the repeatability of the link corresponds to that of the LVDT (linear variable differential transformer) transducer and (d) the link is mounted between two reference balls by using the spring force of the LVDT transducer and thereby eliminating the need for magnets as in the case of the conventional double-ball bar.

With the in-plane and out-of-plane measurements under different test conditions, the machine errors, such as set-up errors, closing errors, backlash errors, dynamic backlash errors, positional errors, pitch motion errors, transient errors around the start point of the test path, vibration due to too high a gain setting, stick-slip errors, squareness errors and servo mis-match errors, can be analysed by the application of the machine error analysis software.

Practical measurements on the TAKISAWA CNC (computerized numerical control) machining centre were carried out and the machine tool errors were effectively evaluated.
The workpiece temperature, fluid cooling effectiveness and burning threshold of grinding energy in creep feed grinding
Authors: Wang S-B , Fuh K-H
Published: October 2002

In this study, a heat transfer model based on numerical analysis of creep feed grinding is proposed. This model is verified to predict the workpiece surface temperature and to find the fraction of heat entering the workpiece. The fluid cooling effectiveness and the effects of specific grinding conditions on the critical grinding energy when the workpiece burns are also discussed. Meanwhile, scaling analysis is performed to explain the influence that conduction behaviour in the moving direction exerts on creep feed grinding. Compared with the published data, the thermal analysis adopted in this paper is shown to be valid.
Machining of free-form surfaces and geometrical specifications
Authors: Lartigue C , Duc E , Tournier C
Published: October 2002

The machining process of free-form surfaces with computer aided design:manufacture (CAD:CAM) systems has to be in accordance with the geometrical specifications. Usually, the cutter path strategy is defined in order to respect these specifications (essentially, form deviation and roughness) as much as possible. Unfortunately, there is no obvious link between geometrical specifications and the CAM parameters that characterize the cutter path strategy. The aim of this paper is to propose links between CAM parameters and geometrical specifications so that the machined surface has the desired quality. These links cannot be made without taking the influence of the form convexity into account. In addition, the parameter values can be optimized with respect to the machining time.
Turbulent solid-liquid flow through the nozzle of premixed abrasive water jet cutting systems
Authors: Ye J , Kovacevic R
Published: October 2002

A computational fluid dynamics analysis has been conducted for the steady state, turbulent, solid-liquid flow through nozzles used in premixed abrasive water jet cutting systems. The development of a theoretical approach to the evaluation of turbulent flow and particle dynamic properties in the nozzles is attractive because of the difficulties associated with direct measurements in nozzles of high flow speed and small dimension. Axisymmetric simulations have been performed with the commercial code FIDAP, using the standard k-∊ turbulence model. One-way coupling was considered in the simulations, which means that the effect of the presence of the dispersed solid phase on the dynamics of the liquid phase was neglected. The velocities and trajectories of solid particles were predicted. The effects of nozzle geometry on particle dynamic properties were studied. The predictions have been compared with available experimental and theoretical results published by other investigators. This modelling technique will assist in the nozzle design of premixed abrasive water jet systems and the prediction of jet cutting performance.
New roles for twenty-first century manufacturing
Authors: Humphreys P K , McAleer W E , McIvor R T
Published: October 2002

The introduction of cellular manufacturing has in general been beneficial to organizations by enhancing productivity and quality, reducing lead times and enriching the jobs for personnel within the cell. However, such changes create conflict owing to the transition from the traditional functional structure to a more flexible cellular environment. This article describes the development of the cell structure within an aerospace company in order to identify the potential problems that can arise between the various participants who operate in a cellular environment. Maister's professional service firm model is then used to structure the roles and responsibilities of the support functions that service the cells, using manufacturing engineering as an exemplar. It is proposed that this framework not only illustrates how planning and organizing issues can be addressed using the concepts developed by Maister but also provides an illustration of how one model propounded by management educators can provide a foundation for enhancing organizational performance.
Selective laser sintering of an amorphous polymer—simulations and experiments
Authors: Childs T H C , Berzins M , Ryder G R , Tontowi A
Published: October 2002

Thermal and powder densification modelling of the selective laser sintering of amorphous polycarbonate is reported. Three strategies have been investigated: analytical, adaptive mesh finite difference and fixed mesh finite element. A comparison between the three and experimental results is used to evaluate their ability reliably to predict the behaviour of the physical process. The finite difference and finite element approaches are the only ones that automatically deal with the non-linearities of the physical process that arise from the variation in the thermal properties of the polymer with density during sintering, but the analytical model has some value, provided appropriate mean values are used for thermal properties. Analysis shows that the densification and linear accuracies due to sintering are most sensitive to changes in the activation energy and heat capacity of the polymer, with a second level of sensitivities that includes powder bed density and powder layer thickness. Simulations of the manufacture of hollow cylinders and T-pieces show feature distortions due to excessive depth of sintering at downward facing surfaces in the powder bed. In addition to supporting the modelling, the experiments draw attention to the importance of sintering machine hardware and software controls.
An object-oriented frame-based prototyping approach for the development of automated manufacturing systems
Authors: Mak K L , Lau H Y K , Wong S T W
Published: October 2002

Prototyping assumes a predominant role in the development of automated manufacturing systems (AMSs) and, in particular, in the verification of system specifications prior to their subsequent realization. In recent years, object-oriented methods have been applied increasingly in the prototyping of AMSs to shorten the development cycle. This paper proposes an object-oriented frame-based approach to the rapid prototyping of AMSs. The proposed approach is characterized by the extended use of the frame-based representation method in the modelling of object behaviour. This approach also draws reference from an object-oriented conceptual model of manufacturing systems and a semantic model of object behaviour. These two models and an object-oriented frame-based prototyping tool are developed to support the approach. When compared with the conventional object-oriented methods, the proposed approach can reduce the semantic gap in system modelling and therefore lead to a better integration of the specification and prototyping of AMSs. The application of the proposed approach is illustrated by the prototyping of a flexible manufacturing system.
Feature-based interaction: An identification and classification methodology
Authors: da Hounsell M Silva , Case K
Published: October 2002

Features are an established means of adding non-geometric information and extra geometric semantics to conventional computer aided design (CAD) systems. For some time it has been realized that, although feature-based modelling is necessary for the next generation of integrated design and manufacturing systems, the inherent feature interactions pose a difficulty in representing and manipulating geometric designs. This paper presents a structured geometric spatial feature interaction identification method based on a broad multilevel classification. Feature interaction definitions and classifications have been surveyed and it is evident that, although many feature interaction classifications have been proposed, there is a lack of a general framework. The classification presented here encompasses existing feature interference cases found in the literature and defines a singular framework that leads to a general classification structure. The framework is presented and applied at three different levels and each interaction case is defined by feature parameters rather than just geometric entities. The restrictions often found in other research concerning contact/non-contact and concave/convex situations are avoided. The resulting classification is easy to understand and implement because it uses simple rules based on commonly available Boolean operators. Finally, an example component is presented and the advantages, uses and applications of the classification scheme are discussed.
Energy life cycle design: A method
Authors: Mueller K G , Court A W , Besant C B
Published: October 2002

This paper presents a strategy for investigating life cycle performance of a product by means of analysing the cumulative energy expenditure (CEE). The strategy involves the use of energy life cycle data on materials, processes, machine elements, subassemblies and assemblies. These are used in a modular approach to put together a concept with the minimum requirement for detailed data. The individual modules need to be categorized according to variables that can be estimated with sufficient confidence early on during the design.
A maximally weighted planar graph method for facilities design
Authors: John E G , Hammond J
Published: October 2002

This paper examines the application of graph theory (GTH) in facilities design and questions whether existing methodologies can be improved. The paper proposes a new approach which introduces the concept of a maximally weighted planar graph (MWPG), in contrast to the more usual maximally planar weighted graph (MPWG).
Distributed autonomous real-time planning and control of small to medium enterprises
Authors: Rahimifard S , Newman S T , Bell R
Published: October 2002

The research reported in this paper is built on the use of the concepts of ‘holonic manufacturing’ and is seeking new methods to reinforce the autonomous and cooperative attributes of planning and control activities within human centred manufacturing facilities. It is claimed that in small enterprises, where the success depends on the skill of individual employees and their ability to collaborate, the manufacturing performance can be improved by the use of the appropriate information technology (IT) tools and the appropriate planning and control structure, designed and developed on the basis of these holonic concepts. Such novel tools and planning structures must provide the most appropriate information in a way that enhances collaborative activity within the business and strengthens the role of the individual. This paper identifies a number of major requirements that must be considered for the design and implementation of an effective production planning and control (PPC) structure, tailored for the needs of small enterprises. Based on these requirements and the use of holonic manufacturing concepts, a novel distributed autonomous real-time planning and control structure is presented. The final sections of the paper describe the implementation of such a planning and control structure within a typical configuration for the production facility of a small metalworking enterprise.
Range image measurement and shaded image measurement: Two non-contact coordinate measurement approaches designed for special application tasks
Authors: Ip R W-L , Hou K C-C
Published: October 2002

Reproduction of sculptured surfaces is a common and difficult process in the manufacturing industry, such as mould and die cavity making for plastic toys. In this paper, two surface measurement techniques, namely range image measurement (RIM) and shaded image measurement (SIM), were investigated. The principle of the two approaches is based on the techniques of non-contact surface coordinate measurement. In RIM the range data of a surface are measured by laser scanning, while in SIM the coordinates of the surface are obtained by a shape from shading model and the photometric stereo technique. The acquired information from these two different surface feature measuring techniques can be used to reconstruct the surface profile by surface models such as the Bezier and B-spline models. The features of the modelled surface can subsequently be used to produce the surface on a numerically controlled (NC) machine. The validity of the approaches was examined by two machining tests, one being a medical trial and the other an industrial case. The results of the tests showed that the principle of the two approaches is workable, but some technical problems of the SIM technique need to be overcome.
Manufacturing information interactions in data model driven design
Authors: Young R I M , Canciglieri O , Costa C A
Published: October 2002

This paper presents a novel view of a software environment that has the potential to provide manufacturing information support to product design in line with the aims of concurrent engineering. The arguments developed should have significant consequences for future computer aided engineering (CAE) systems development and support the continuing globalization in business development. The approach taken has at the centre of its philosophy the need to provide designers with high-quality information on which to base their decisions. The concept of an information supported product design environment is not new, but a range of issues related to information interactions has yet to be resolved. This paper explores the use of information models to support functional and manufacturing interactions in design as well as the issues that are raised in attempting to support multiple views in design for manufacture. The design of injection moulded products is used as the focus against which the ideas in the paper are explored.
Heat generation at photopolymerization by multiple-spot exposure with blue light
Authors: Loose K , Niino T , Nakagawa T
Published: October 2002

In this paper, heat generation in an acrylate monomer during photopolymerization in multiple-LED photographic curing (MPC) is studied. During the exposure process, an array of multiple beams of light are projected simultaneously on to the resin surface while the projector moves across the resin vat. In this way, exposure occurs through raster scanning. It was found that the heat generated by the polymerization process causes the resin temperature to increase in steps to a maximum of 25 °C when scanning at a velocity of 0.5 mm/s. Heat from the light source itself is not induced. At 3 mm/s, excess temperature decreases to only approximately 4.5 °C. For one layer, three-dimensional temperature profiles show that excess temperature is distributed equally, perpendicular to the scan direction.

The polymerization process occurs slowly. Using spectrophotometry, the course of absorbance of the photoinitiators can be observed. At 470 nm, the absorbance increases from 0.4 to 1.2 in the liquid state. The absorbance of the photoinitiators decreases to 0.1. After 30 min of exposure, the polymerization process is complete. This necessitates post-curing after the actual build process.
Intelligent control of VCR audio tuning process using a genetic estimator
Authors: Cho D-j , Gweon D-g
Published: October 2002

This article proposes an intelligent control scheme for automating the VCR audio tuning process using genetic algorithms (GAs). Being a non-linear multimodal system, the process is difficult to automate by simple conventional controllers. In the proposed control scheme, a new kind of GA structure, called a genetic estimator, is used for estimating the unknown internal state of the process and a simple integral controller is adopted to drive the process according to the estimated state. To adapt GA to the estimation problem, the general procedure of the conventional GAs is modified in two aspects: the reproduction strategy uses two different criteria (survival cost and parent cost) for natural selection and parent selection, and a new genetic operator is developed on the basis of the model of the process to generate offspring solutions more effectively. The performance of the proposed control scheme was investigated via experiments, and the results obtained show that the control scheme performs the task very well.
Extraction of compound volumetric features from a three-dimensional wire frame model
Authors: Jain P K
Published: October 2002

This paper reports feature extraction strategy adopted in a computer aided process planning (CAPP) system developed for prismatic parts. Automatic extraction of compound volumetric features from three-dimensional wire frame models created in AutoCAD is discussed. Size, location and shape elements of a feature are used to recognize simple volumetric features like slots, steps, holes and pockets of different profile geometries by considering a hole as a basic feature. Compound volumetric features are defined as a combination of more than one simple volumetric feature such as slot-in-slot, slot-in-step, etc. Connectivity through common surface(s)/edges between member features is used to recognize compound features. The feature extractor output can be used for the generation of manufacturing instructions, namely set-up planning, process selection, sequence generation, machining parameters selection, etc. The unique feature of this system is that it works on a wire frame model of the part and needs no help from the user in extracting features. The working of the system and algorithms used for feature extraction are explained with examples.
Smooth circular arc interpolation for planar free curves with tolerance control
Authors: Lee J-J , Hascoët J-Y
Published: October 2002

Several circular arc curve-fitting methods have been proposed to overcome the drawbacks caused by a series of short linear movements in planar curve contouring machining. Almost all the previous circular arc curve-fitting methods assume that overcut and undercut allowances are the same. This assumption is not practical in industry since the allowances can vary according to the characteristic of the part to be machined. The objective of this paper is to develop an enhanced circular arc interpolation algorithm for planar free curves including tolerance control, which is easy and robust in practical implementation. An important property of the circular arc curve is that its offset curve is also another circular arc curve and can be calculated analytically. Using this property, the tolerance factors can be taken into account effectively in the present algorithm.
Design reuse: An overview
Authors: Sivaloganathan S , Shahin T M M
Published: October 2002

This paper reviews the current research that has been carried out under the ‘design reuse’ umbrella. It classifies and discusses the work carried out in design reuse under seven categories, namely:

focused innovation, cognitive studies on design reuse, computational perspective of design reuse, use of standard components, design reuse tools and methods, design reuse systems and issues in design reuse.

In the light of this discussion it proposes future areas of work to enable design reuse to become an accepted tool for systematic design.
Three-dimensional temperature distribution in laser surface hardening processes
Authors: Woo H G , Cho H S
Published: October 2002

This paper introduces a new analytical solution to predict transient temperature distributions in a finite thickness plate during laser surface hardening. This analytical solution was obtained by solving a transient three-dimensional heat conduction equation with convection boundary conditions at the surfaces of the workpiece. To calculate the temperature field numerically in laser surface hardening processes, laser beam absorptivity, one of the most important parameters, should first be determined. It was extremely difficult to find an accurate value for laser beam absorptivity owing to the use of coating material on the workpiece surfaces, essentially to improve the efficiency of laser beam power. Therefore, in this paper, absorptivities were measured experimentally under various hardening conditions, including variations in coating thickness, laser beam power and beam travel velocity. Thereafter, to prove the validity of the model, a series of laser surface hardening experiments was performed on medium-carbon steel under various hardening conditions. The hardened layer of the etched cross-sectional view was examined and compared with the isothermal lines predicted by the proposed analytical model, in which the values of the experimentally measured absorptivity were employed. The results showed that the solution predicted well the transient temperature distribution of finite plates with satisfactory accuracy. Also, owing to the simplicity of the solution method, the analytical model developed may be easily implemented for simulation work for analysis and prediction of laser surface hardening processes under various hardening conditions.
A manufacturing model of carbide-tipped spherical milling cutters
Authors: Chen C-K , Lai H-Y , Tang Y
Published: October 2002

The paper presents a manufacturing model for use in grinding the front-end surfaces of a carbide-tipped spherical milling cutter. The concepts of radial equidistant lines and oblique equidistant surfaces are presented. Based upon these concepts, a model of the cutting edge of a spherical milling cutter is derived by solution for the intersection of the spherical front-end surface of the cutter and the equation of a sphere. A special mechanism model is also presented for grinding the rear cutting-edge surface of the cutter. To ensure that the mechanism model is valid, the cutting-edge curve of the cutter is also on the rear cutting-edge surface. The associated geometric and manufacturing parameters are further optimized to ensure that the best quality of the carbide-tipped spherical milling cutter can be achieved. The mechanism is also used to study the manufacturability of spherical milling cutters for slightly varying specifications. A numerical example is presented to illustrate the effectiveness of the proposed modelling procedure for producing carbide-tipped spherical milling cutters. Numerical results indicate that the proposed manufacturing model and grinding procedure are capable of producing a family of carbide-tipped spherical milling cutters with an accuracy up to the user-provided specific tolerance. Some major contributions of the proposed approach are summarized in the conclusions.
Manufacturing cost estimation during design of fabricated parts
Authors: Schreve K , Schuster H R , Basson A H
Published: October 2002

Manufacturing cost estimation models can overcome some of the limitations of relying only on design experience. This paper outlines the role of cost models in design for manufacture (DFM) and the requirements for a design for manufacturing cost estimation models. Cost models for a process typical of batch production of fabricated steel welded assemblies, i.e. tack welding, are presented as examples in this paper, and references are given for cost models of other fabrication processes. The cost models were developed from data collected through time studies and analysed using robust regression statistical methods. The model estimates were compared to production estimates from two companies.
The application of computational fluid dynamics to the development of a pharmaceutical processor
Authors: MacGregor S A , Newnes L B , Li M , Staniforth J N , Tobyn M J , Kay G R , Horrill M D , Lamming R C , Hajee D W , Wong D , Chippendale K E , Page T
Published: October 2002

The use of computational fluid dynamics (CFD) in the design of a pharmaceutical processor is described. A simple computational model of the process vessel was developed using a single-phase flow. The results of this preliminary study showed good agreement with experimental tests. The model was further developed to consider the effect of solid particles on the processes occurring within a single vessel pharmaceutical processor. Having obtained converged solutions, the model was used to optimize the design of the processor. The model was used to develop new designs of the vessel. The design optimization was done on the basis of comparisons with conventional pharmaceutical processing equipment. Optimization of the process parameters is important, as they are known to affect the functionality of the final product. The study reported here discusses one step in the design process, showing how changes to the inlet configuration can be modelled to show the potential for improved performance.
Exploiting (supplier) information acquisition mechanisms in NPD: An empirical study
Authors: Culley S J , Boston O P , McMahon C A
Published: October 2002

This paper proposes a number of information acquisition mechanisms by which engineering designers may acquire information from suppliers. It then provides an overview of a selection of case design projects that were studied from the perspective of customer as designer-supplier information interactions. Subsequently, based on an analysis of models of these data, it shows that engineering designers may not be exploiting the ‘information and knowledge’ available from suppliers to its full potential. Finally, it highlights a number of ‘interaction guidelines’ specific areas in which engineering designers are lacking in support.
Analytical solution for transient temperature distribution in gas tungsten arc welding with consideration of filler wire
Authors: Kang S H , Cho H S
Published: October 2002

This paper is focused on deriving an analytical solution to predict the transient temperature distribution of the plate during the process of gas tungsten arc (GTA) welding in which a filler wire is fed. An analytical solution is derived from the transient three-dimensional heat conduction equation by applying a convection boundary condition to the top and bottom surface of an infinite plate of finite thickness. The heat input that is applied on the plate is exactly the same as the amount of heat lost from the electric arc while fusing the filler wire. The electric arc is assumed to be a moving heat source with a Gaussian distribution. The point heat sink is located in the spot where the filler wire is fed to the weld pool. However, the feed position of the filler wire is ever-evolving with time because the size of the weld pool changes in accordance with the welding conditions. Nevertheless, the algorithm is capable of determining the feed position. Also, the influence of the filler wire on the temperature distribution of the plate is established by removing the filler wire from the analytical solution and comparing these two different situations. In order to verify the validity of this solution, a GTA welding experiment is conducted for various welding conditions. After this stage, the resulting isotherms of the cross-sections of the plate and the analytical results are compared. The analytical solution, which is in good agreement with experimental results, is the very first to take the filler wire feed into consideration. It can be used as a model to control the GTA welding process with account taken of the filler wire, and it can also be used as an optimization tool for welding process parameters.
Failure analysis of mature robots in automated production
Authors: Starr A G , Wynne R J , Kennedy I
Published: October 2002

Robot failures are costly and difficult to diagnose. Breakdown data for robot-automated production lines, collected from automotive applications, showed that nearly half of robot failures are caused by positional error. A further quarter were attributed to drive failures. Positional error may be caused by a number of mechanical failure modes or by poor tuning of the control system. Testing of repeatability or absolute position in the work place is hard because the robot moves quickly, allowing little time for measurement. Measurement may be required in up to six axes. The end-effectors of a robot, e.g. welding guns, grinding wheels and sealant applicators, are powerful and unguarded, and are not compatible with conventional contact, or close proximity non-contact, transducers.

This paper presents significant new industrial evidence of the need for advanced diagnostic techniques in industrial robotics. Historical records for about 200 robots in automotive applications were analysed, identifying the major failure modes. Existing maintenance and condition monitoring methods were audited, and the problems of selecting condition monitoring methods for robots were analysed, identifying characteristics that differ from application in calibration. Measurement methods are briefly reviewed in the paper. It is concluded that non-invasive, non-contact methods are a prerequisite for operational effectiveness.
A systems engineering approach to product modularity
Authors: Marshall R , Leaney P G
Published: October 2002

Product modularity has been successfully adopted in a number of specific industries, such as computer technology and software development, where it provides a number of advantages over monolithic product architectures. This paper presents initial findings from research at a range of companies within the United Kingdom where modularity is being applied or considered to address increasing product complexity and the growing need for the symbiosis of mechanical, electrical, electronic, optical and software technologies in a wider range of manufactured products to meet discerning market requirements. The research identifies a need to address the current application of modularity within industry at three levels: A systems engineering based framework, a methodology for product modularization and the underlying process of modular product development. Concluding remarks highlight the issues drawn from the research and opportunities for addressing these issues.
Grinding ceramics containing preformed cracks
Authors: Maksoud T M A , Mokbel A A , Morgan J E
Published: October 2002

Diamond grinding of ceramics creates an interaction of complex elastic/plastic deformations within the ceramic workpiece. These deformations cause cracking on the surface and in the bulk of the ceramic, where cracks of different types, locations and characteristics can be produced. During grinding, cracks may propagate, open or close. This paper describes the production of cracks during the grinding of silicon nitride. Radial, median and lateral cracks are identified and the type of crack produced is linked to grinding parameters such as grit size, bond type, depth of cut, feed rate, etc.
Efficient control chart pattern recognition through synergistic and distributed artificial neural networks
Authors: Wani M A , Pham D T
Published: October 2002

Accurate and fast control chart pattern recognition is essential for efficient system monitoring to maintain the production of high-quality goods. This paper addresses three major issues of control chart pattern recognition: (a) transparency, (b) accuracy and (c) fast detection of abnormal patterns. A new approach is described which uses novel shape features extracted from a control chart pattern (CCP) instead of the unprocessed CCP data or its statistical properties. These features represent the shape of the CCP explicitly. A set of algorithms is described for extraction of the shape features from a CCP. The paper discusses the use of artificial neural networks for recognition of the shape features. Synergistic, distributed and distributed synergistic neural networks are proposed for learning efficiently non-linear characteristics and overlapping ranges of values of the data set describing CCPs. The paper presents the results of analysing several hundred control chart patterns and gives a comparison with those reported in previous work.
Optical probing of acoustic emission from a rotating tool holder with a Sagnac interferometer
Authors: Jakobsen M L , Harvey D , Carolan T A , Barton J S , Jones J D C , Reuben R L
Published: October 2002

The development of the Sagnac interferometer to monitor the machining process in high-value-added machining processes is described. The instrumental requirements are non-contact measurement of acoustic emission, in the form of 0.1–1.0 MHz out-of-plane vibration, with amplitudes in the subnanometre range. The instrument was designed to detect acoustic emission by probing the surface of the rotating tool holder on the machine tool shaft. Experiments leading to the instrument design, face milling and slot milling machine tests and a comparison with earlier instrument designs are described.
An experimental investigation of human mismatches in machining
Authors: Case K , Sinclair M A , Rani M R Abdul
Published: October 2002

Mismatches refer to incompatibilities, inappropriateness, unsuitabilities or inconsistencies in machine operators' actions which, if not addressed, would lead to errors. A fuller understanding of the rate at which mismatches occur and their causes would allow human aspects to be given proper consideration alongside hardware and technological issues in the design of new working environments, machines and tasks. This research highlights these human aspects of machining by examining mismatches in relation to various human characteristics.

The human task-mismatch matching method was developed and applied in manual turning operations using experimental and questionnaire techniques on groups of 16 skilled and 12 unskilled operators. The skilled subjects were drawn from local industry and university technical staff. Unskilled subjects were engineering students, all of whom had some familiarity with machining through periods of industrial placement. Statistically significant relationships were established between mismatches and many of the human characteristics studied (skill, age, work experience, self-confidence and trust) when considering all the subjects as a single group, but for skilled operators alone, the only significant relationship was between self-confidence and trust.

As a general conclusion, it can be confirmed that studying operators in their own workplace provides invaluable information for the design and operation of future workplaces, but that the relationships between performance and human characteristics remain difficult to establish formally.
The contribution of micro/nano-tribology to the interpretation of dry friction
Authors: Johnson K. L.
Published: October 2002

Fundamental studies of the mechanics and physics of dry sliding friction between solid surfaces have been impeded in the past by surface roughness and the difficulty of determining the real area of contact. The last decade has seen an explosive development of techniques to study friction at single-asperity contacts in which the real and apparent contact areas coincide. The contribution of these developments to interpreting dry friction is discussed in this paper. Experiments with smooth compliant rubber led to an appreciation of the role of adhesive forces and to including its effects in contact mechanics. Atomically smooth surfaces are obtained in the surface force apparatus (SFA) through the property of mica to cleave on atomic planes, and in the atomic force/friction microscope (AFM) by the use of nanometre size contacts on single crystals. Based on friction measurements in the SFA and AFM, a hypothesis is advanced that sliding of atomically smooth contacts takes place by the nucleation and propagation of dislocation-like defects through the interface. An analysis by Hurtado and Kim [29] using dislocation mechanics suggests a ‘scale effect’ in which friction is governed by resistance to nucleation in very small contacts and by resistance to propagation in larger contacts.
Gears: Elastohydrodynamic lubrication and durability
Authors: Snidle R. W. , Evans H. P. , Alanou M. P.
Published: October 2002

The paper presents a brief review of developments in understanding of gear tooth contact lubrication in relation to problems of surface durability and distress. Gear tooth contacts tend to operate under conditions where the lubricating oil film is thin compared with surface roughness. This feature is shown to have a significant effect on scuffing capacity and friction and is also thought to be a factor in micropitting. Recent developments in thin-film micro-elastohydrodynamic lubrication theory are described and these should lead to a better understanding of the behaviour and modes of surface distress in gears. The paper also describes the application of elastohydrodynamic analysis to other transmission components such as high-conformity gears and thrust cones.
Influence of circumferential waviness on engine bearing performance
Authors: Mehenny D. S. , Taylor C. M.
Published: October 2002

The influence of circumferential waviness of the journal on the lubrication of the inter-main bearing of an automotive engine is investigated using a theoretical analysis. The analysis is for two-dimensional thin film flow, with oil-film history. The bearing and shaft surfaces were assumed to be rigid and the lubricant isoviscous. The results show a significant influence of shaft lobing on predicted maximum film pressure and minimum film thickness, particularly as the number and size of lobes increase. It is concluded that, for satisfactory operation of engine bearings, circumferential form errors of the shaft need to be controlled.
Structural damping enhancement using a novel approach—a forward look
Authors: Tomlinson G. R.
Published: October 2002

This paper considers two aspects for enhancing structural damping using passive, but novel, methods. Attempting to take a forward look to the twenty-first century, the concept of using biological and evolutionary methods to ‘grow’ damping material on the surface of a vibrating component is described. A simple cantilever beam is used as the component and a ‘free-layer’ viscoelastic damping treatment is ‘grown’ on the structure in such a way as to provide optimum damping over a frequency bandwidth that encompasses flexural and torsional modes of vibration. To enhance the ‘controllability’ of the damping, the viscoelastic material is considered as a cellular material displaying a negative Poisson's ratio and it is shown that for the ‘free-layer’ treatment it is possible to produce a range of modal loss factors by changing the cell geometry. Only numerical studies are used and no experimental validation has been carried out, the idea being to stimulate ideas for future structural damping concepts.
Combustion and the thermodynamic performance of spark ignition engines
Authors: Bradley D , Lawes M , Sheppard C. G. W.
Published: October 2002

Some overall considerations for the optimization of the energy chain for the spark ignition engine are briefly discussed and figures given for the relative inhaled energies with different fuels. There follows a description of the nature of turbulent flame propagation in engines, showing the computed characteristics of the burning rate for stoichiometric and lean mixtures at different engine speeds. These reveal the factors influencing partial quenching and misfire. Flame instabilities are shown theoretically to become more important with increasing pressure. The associated flame wrinkling and cellularity increase the burning rate of both laminar and turbulent gaseous flames. Fundamental aspects of the present trend towards the direct injection of gasoline are discussed and the unique instabilities in aerosol combustion are shown to increase the burning velocity above that of the corresponding gaseous mixture. The degree to which evaporative cooling of droplets can enhance the volumetric efficiency is discussed. The onset of autoignition in an engine is calculated with recent shock tube data, which are also used to show that evaporative cooling can increase the knock resistance by about four octane numbers.
The future of aircraft propulsion
Authors: Ruffles P. C.
Published: October 2002

The next century offers many challenges to the aero-engine industry in both the civil and the military markets. The primary driver in both markets will be to reduce the cost of acquiring, operating and supporting the product throughout its life. Reducing the environmental impact will be an additional challenge for the civil sector.

Aero-engines operate at the limits of technology, take longer to develop than airframes, are often in direct competition for one such airframe and typically have an aftermarket value of up to double their initial cost. It is therefore important to place great emphasis on forecasting customer needs and future market requirements.

Developments in the design of turbomachinery, combustion and control systems will offer performance, cost and environmental advantages in both the near and the long term. These developments will be aided by the progression of materials technology.

The technologies applied to the product will be complemented by the technologies applied in the design, manufacture and support of products in order to reduce cost at every stage of the product life cycle. In this way the industry will continue to provide value to the customer well into the twenty-first century.
The influence of mean contact pressure on the friction coefficient of a traction fluid at high pressure
Authors: Workel M F , Dowson D , Ehret P , Taylor C M
Published: October 2002

A new ball impact apparatus has been developed for measuring the friction coefficients of solidified lubricants under very high pressures. Results obtained for Santotrac 50 showed a decrease in friction coefficient with increasing mean contact pressure and showed good consistency with values reported elsewhere from several different forms of apparatus.
Analysis of the flow through a circular-to-semicircular cooling baffle bend
Authors: Van der Walt J P , Morsi Y S
Published: October 2002

The cooling of moulds through the usage of baffles is commonplace in the plastic injection moulding industry. The flow of cooling water through the baffle entrance experiences a sharp 90° bend as well as a circular-to-semicircular geometry change. As it is apparent from the literature that no pressure loss relationships are available, an experimental test rig was constructed to enable these losses to be measured. Furthermore, a numerical model was constructed through the use of computational fluid dynamics to assist in the development of these correlations. This paper discusses this flow problem and develops a new empirical correlation using dimensional analysis for the sharp circular-to-semicircular elbow entrance of the cooling baffle of a plastic injection mould. It was found that the empirical relationship predicts the pressure losses with good accuracy.
Predicting heat extraction due to boiling in the cooling channels during the pressure die casting process
Authors: Clark L D , Rosindale I , Davey K , Hinduja S , Dooling P J
Published: October 2002

The effect of boiling on the rate of heat extraction by cooling channels employed in pressure die casting dies is investigated. The cooling effect of the channels is simulated using a model that accounts for subcooled nucleate boiling and transitional film boiling as well as forced convection. The boiling model provides a continuous relationship between the rate of heat transfer and temperature, and can be applied to surfaces where forced convection, subcooled nucleate boiling and transitional film boiling are taking place in close proximity. The effects of physical parameters such as flow velocity, degree of subcooling, system pressure and bulk temperature are taken into account. Experimental results are obtained using a rig that simulates the pressure die casting process. The results are compared with the model predictions and are found to show good agreement. Instrumented field tests, on an industrial die casting machine, are also reported. These tests show the beneficial effects of boiling heat transfer in the pressure die casting process, including a 75 per cent increase in the production rate for the test component.
Detection and monitoring of cracks in rotors through Q factors
Authors: Sekhar A S
Published: October 2002

Dynamic analysis of a cracked Jeffcott rotor has been carried out, considering the effects of fluid film bearings. Q factors and dissipation coefficients have been evaluated in addition to the harmonic responses of the rotor. The coast down phenomenon was analysed for the effects of crack depth. Sensitivity studies were carried out, considering dissipation, response and the Q factor. Measurement of Q factors of second harmonics, Qx1 and Qy2, has been suggested for crack detection, while measurement of Q factors of first harmonics is recommended for crack monitoring as these proved to be more sensitive to cracks compared with other methods.
Space-time visualization of vibration of a ribbed cylinder
Authors: Woodhouse J , Power J
Published: October 2002

Data from an axial array of sensors along a ribbed cylindrical structure may be analysed to allow the evolving vibrational response to impulsive driving to be plotted as a function of space and time. The process is carried out separately in a series of frequency bands, by first carrying out a time-frequency analysis at each position. Aspects of the behaviour not previously discussed are highlighted by this analysis. These aspects are discussed in the light of a previously published theoretical model [1]. Since reflections from the cylinder's ends also play a role here, it has been necessary to develop further theoretical modelling to interpret the measurements. The new experimental approach, which is described here as the method of ‘space-time cross-sections', has scope for application to other problems involving structure-borne vibration. This illustrates the power of time-frequency analysis and its extensions for engineering vibration analysis.
Prediction of natural frequencies for thin circular cylindrical shells
Authors: Naeem M N , Sharma C B
Published: October 2002

In this paper an analytical procedure is given to study the free-vibration characteristics of thin circular cylindrical shells. Ritz polynomial functions are assumed to model the axial modal dependence and the Rayleigh-Ritz variational approach is employed to formulate the general eigenvalue problem. Influence of some commonly used boundary conditions, viz. simply supported-simply supported, clamped-clamped and clamped-free, and also the effects of variations of shell parameters on the vibration frequencies are examined. Natural frequencies for a number of particular cases are evaluated and compared with some available experimental and other analytical results in the literature on this topic. These results are given in the form of tables and figures. A very good agreement between the results of the present analysis and the corresponding experimental and analytical results available in the literature is obtained to confirm the validity and accuracy as well as the efficiency of the method.