bluuebunny/crossref_metadata_2025 huggingface dataset:
Roll pass evaluation for three-dimensional section rolling using a simplified finite element method
Authors: Wen S W , Hartley P , Pillinger I , Sturgess C E N
Published: October 2002

A simplified finite element (FE) method for modelling the complex three-dimensional deformation inherent in section rolling is presented. This simplified FE technique has been developed by considering a single slice of material of finite thickness passing through the roll gap, to avoid performing a full three- dimensional finite element analysis. Only one layer of a finite element mesh (consisting of brick elements) is generated on the slice of the process material taken from the three-dimensional workpiece. The slice of material is considered to be compressed using a pair of grooved dies, which have the same profiles as the rolls. In order to make this simplified pseudo-two-dimensional model more realistic, the speed of compression of the grooved dies is modified according to the vertical component of the peripheral roll velocity within the contact zone. Equations have been developed to approximate the roll separation force. This method is applied to perform a pre- and post-rolling FE analysis for the rolling process of a special section produced at British Steel's Skinningrove Works. The roll pass design and the stability of the rolling process are evaluated according to the results obtained from the FE predictions. Comparisons between FE results and experiment are made where possible.
Developing methodologies for robust mechanical engineering design
Authors: Dunsmore W , Pitts G , Lewis S M , Sexton C J , Please C P , Carden P J
Published: October 2002

This paper considers robust product design applied to mechanical systems via computer-based models at the detail design stage. This involves the efficient use of computer-based experiments to understand how product performance, both its mean and variability, depends on the design parameters. The integration of the general concepts and practical tools is described in terms of the design process, with the aim of making the techniques accessible to designers in an industrial context. The approach is motivated from a design for quality standpoint and is directed principally at improving functional reliability, while addressing issues of performance and cost. The approach is illustrated using a case study on the robust design of a cam mechanism.
The ‘green area’ concept
Authors: Norridge B , Burns N D , Backhouse C J
Published: October 2002

The paper discusses the application of a new cell management system implemented in a UK company. The system was originally based upon the Nissan ‘green area’ (GA) concept but it was extended at the company into a complete business management structure covering the entire business. This new structure involved a GA system in the operational activities of the business, for example shop-floor and commercial activities, a ‘business excellence’ GA system primarily aimed at business improvement and development projects and a business strategic GA system. The GA system was used throughout the business and integrated the activities of cells in the commercial, engineering and shop-floor domains. It was more than the quality circle concept in that it also provided a mechanism for performance assessment, business control, improvement, training and communication.
Solid freeforming of ceramics using a drop-on-demand jet printer
Authors: Xiang Q F , Evans J R G , Edirisinghe M J , Blazdell P F
Published: October 2002

The formulation of a stabilized ceramic ink and the adaptation of a piezoelectric-activated drop- on-demand jet printer with a 65 mm nozzle for the direct solid freeforming of ceramics by multilayer jet printing is reported. The procedure has exciting implications for the miniaturization of ceramic circuits and for the fabrication of solid oxide fuel cells, ordered ceramic composites and small monolithic ceramic components of complex shape.
The role of inhomogeneous deformation in high-temperature ring compression testing
Authors: Nanneh M , Dunne F P E
Published: October 2002

Elastic-viscoplastic constitutive equations that enable the modelling of rate effects, temperature effects and dynamic recrystallization are employed to model the ring compression test at high temperatures. The effects of strain rate and temperature on the calibration curves, used widely to characterize frictional behaviour in forging, are investigated.

Both strain rate and temperature are found to influence the calibration curves obtained, and it is found that the influence derives from the dependency of dynamic recrystallization processes on strain rate and temperature. The coupling between the deformation and the recrystallization process is found to lead to the establishment of significantly different strain fields with different strain rates, and it is this that leads to the dependency of the calibration curves on strain rate and temperature.

A methodology has been presented for the determination of friction calibration curves for hot forging of high-performance materials, which accounts for strain rate effects, temperature effects and recrystallization processes. The method is likely to be useful to industries involved in the high-temperature processing of high-performance components.
Modelling void nucleation and growth in axisymmetric extrusion
Authors: Lim L G , Dunne F P E
Published: October 2002

Elastic-viscoplastic constitutive equations, with kinematic and isotropic hardening, are employed to model the deformation behaviour of an aluminium alloy in extrusion. Constitutive equations are also employed for void nucleation and growth, which are fully coupled with the deformation behaviour. The material model is employed to investigate the roles of void nucleation and growth in extrusion defect formation.

It has been shown that central bursting is a void growth controlled process. The existence of nucleated voids only leads to central burst formation with the existence of appropriate stress states which lead to void growth. The results obtained show excellent agreement with well-established limit diagrams, obtained analytically and experimentally.

The results also show that for a given combination of area reduction and semi-cone die angle, the introduction of friction tends to inhibit the formation of central bursting, but increases the likelihood of surface tearing/cracking. The tendency to inhibit central burst formation with increasing friction results from the reduction in the levels of tensile hydrostatic stress, which therefore reduce the rate of void growth.

A comparison of the results obtained using kinematic and isotropic hardening in the extrusion process showed that significantly different residual stress fields are obtained for the two cases. This is of importance, for example, in the case of multipass extrusion or where the residual stress field is to be used subsequently in design analysis.
Numerical simulation of current density in gas tungsten arc welding including the influence of the cathode
Authors: Fan H G , Na S-J , Shi Y W
Published: October 2002

A two-dimensional axisymmetric numerical model including the influence of cathode is developed to describe the heat transfer and fluid flow in gas tungsten arc (GTA) welding arcs. The current continuity equation has been solved with the combined arc plasma-cathode system, independent of the assumption of current density distribution on the cathode surface which was essential in the previous studies of the arc plasma. It is indicated that the predicted arc column temperatures agree well with existing experimental data. The effects of current, electrode tip geometry and arc length on the anode current density distributions are analysed using the developed model, and the current density distributions calculated at the anode are compared with the experimental data measured by the probe method.
Self-assessment: Methods, management and process
Authors: Teo W F , Dale B G
Published: October 2002

Self-assessment is a method for reviewing the activities and performance of an organization. This paper reports the findings of a study in four organizations of their management of this process. Each company followed the key self-assessment stages of planning, developing awareness, implementation and review but carried out the process in a different manner. The level of total quality management (TQM) maturity, available resources and organizational culture were the main factors for the differences.

The key to successful self-assessment is effective management and the use of a team to manage the process. The most important activities were identified as: selection of a suitable model, appropriate approach(es) for the assessment, provision of appropriate training, monitoring the progress of improvement actions, establishment of a ‘closed-loop’ structure for the improvement cycle and integration of improvement with the strategic business plan. It is also pointed out that self-assessment is not without difficulties, including scarcity of time, overemphasis on scoring and scores, failing to follow-up improvement actions and lack of communication.
An investigation of the effects of autobrazer parameter variations on the quality of return bend joints
Authors: Agba E I , Jones E W , Penaherrera A S , Thrift B
Published: October 2002

A temperature monitor that can record brazing temperatures inside an autobrazer for process control and qualification was developed. The monitor was made of a heat exchanger coil instrumented with multiple thermocouples at statistically selected return bend joints that had a high or low probability of leaking. The brazing temperatures recorded at the selected return bends were compared with control temperature profiles for high-quality brazed joints. The results clearly accentuated the disparities in the heating rates, the cooling rates and the peak bonding temperatures between the non-leaking joints and the leaking joints. The autobrazer process parameters were then correlated with a number of leaks and leak locations to determine how to configure the autobrazer and control the process variables to ensure similar brazing conditions at all joints. By so doing, the repeatability of the brazing process and the production of high-quality joints was guaranteed.
A ‘stepper’ approach to tolerance charting
Authors: Ngoi B K A , Goh L C
Published: October 2002

This paper presents a simplified approach of model construction directly from the process plan. With the model constructed, the relevant process links between any two surfaces can be easily determined. Unlike other methods, it does not require transcribing the link information into constraint equations. The formation of the constraint equations is made easier by direct read-out from the model. The constraint equations can then be solved by using LINDO (a linear programming optimization software) to generate the working dimensions and tolerances. An example is included for illustration of the method presented.
Path trajectory verification for robot manipulators in a manufacturing environment
Authors: Abdel-Malek K , Yeh H J
Published: October 2002

In a manufacturing environment where a robotic arm is programmed to follow a specified trajectory such as in welding, painting and soldering, it is often the case that the arm reaches a singular configu- ration, where the programme is stopped, the arm is switched to a new configuration and the motion is continued. This difficulty has been a long-standing problem. This paper presents a mathematical formulation for verifying whether a trajectory can be completed, uninterrupted, avoiding halting of a planned path. In some cases, this formulation also allows the selection of an initial configuration to ensure a smooth path trajectory. The paper presents an analytical formulation for determining barriers to motion inside the workspace of manipulator arms. Crossability analysis of the end-effector on a barrier is addressed. A criterion for selecting an initial configuration that would result in an uninterrupted motion is introduced. The mathematical theory is validated through numerical examples of planar and spatial manipulator arms.
An approach to concurrent engineering
Authors: Pham D T , Dimov S S
Published: October 2002

This paper presents a new approach to concurrent engineering, focusing on simultaneous product design and process planning. The key elements in this approach are (a) a framework for structuring manufacturing information and maximizing the information-carrying capacity of the design models, (b) a procedure for intelligently mapping form features on to pertinent manufacturing considerations and (c) a procedure for utilizing the available manufacturing information about components already machined within the given manufacturing environment. The proposed approach provides a natural way for conveying manufacturing information to the designer. Its distinguishing feature is the application of a wide range of artificial intelligence techniques for knowledge acquisition and deductive reasoning.
Influence of exit angle and tool nose geometry on burr formation in face milling operations
Authors: Olvera O , Barrow G
Published: October 2002

One of the more important burrs produced in a face milling operation is the burr formed on the exit edge in the cutting direction. This burr is present over the full length of the exit edge, and under certain cutting conditions is relatively large in size, strongly attached to the workpiece, and presents a strong configuration, features that make it difficult to remove and consequently increases the cost of the component. This paper is concerned with the influence of the exit angle and tool nose geometry on the formation of this burr for both finishing and roughing conditions (small and large depths of cut respectively), with a medium carbon steel. The results show that four different types of burr can be produced on the exit edge, namely the tear, curly, rubbing and wavy burrs. The exit angle and the tool nose geometry have a significant influence on the formation and characteristics of the burr formed on the exit edge. Under finishing conditions, exit angles greater than 90° and large tool nose radii facilitate the formation of large primary burrs. Under roughing conditions, on the contrary, the exit angle affects the type of burr produced on the exit edge, whereas the tool nose geometry only influences the burr size. The formation of primary and secondary burrs is mainly determined by the chip flow angle ρ; primary (wavy) burrs usually form for ρ > ρt (where the transition chip flow angle ρt ≈ 42°, in this case) and secondary (tear) burrs for r < rt.
An information systems architecture for small metal-working companies
Authors: Toh K T K , Newman S T , Bell R
Published: October 2002

This paper offers a novel approach for the specification of the information networks needed by small metal-working companies and is based on the precept that the network should support rather than dictate the mode of operation of the business. The work is underpinned by the use of holonic systems concepts and constitutes a contribution to research in the field of human-centred manufacturing. The first part of the paper is concerned with holonic issues; the small to medium enterprise (SME) is viewed as an holarchy and the reader is introduced to the concept of the holonically enhanced SME. The second part of the paper is concerned with the generation of an holonic information system, the emphasis being placed on the realization of the system specification for information requirements. The enabling technology to realize this spec- ification is discussed, a three-part enterprise model is introduced and the supporting CASE tool is discussed.
A computational modelling framework to predict macroscopic phenomena in solder joint formation
Authors: Wheeler D , Bailey C , Cross M
Published: October 2002

A computational model of solder joint formation and the subsequent cooling behaviour is described. Given the rapid changes in the technology of printed circuit boards, there is a requirement for comprehensive models of solder joint formation which permit detailed analysis of design and optimization options. Solder joint formation is complex, involving a range of interacting phenomena. This paper describes a model implementation (as part of a more comprehensive framework) to describe the shape formation (conditioned by surface tension), heat transfer, phase change and the development of elastoviscoplastic stress. The computational modelling framework is based upon mixed finite element and finite volume procedures, and has unstructured meshes enabling arbitrarily complex geometries to be analysed. Initial results for both through-hole and surface-mount geometries are presented.
Rapid prototyping of metal parts by three-dimensional welding
Authors: Spencer J D , Dickens P M , Wykes C M
Published: October 2002

Three-dimensional welding has the ability to produce strong, fully dense metal parts in layers. Adaptation of a weld cladding technique has enabled the production of parts wider than normally possible from single beads. However, high heat inputs during welding could affect part quality. Simple temperature control techniques help improve surface finish. A number of parts were made incorporating temperature control. Results show that, although improvements have been made, corresponding time penalties can have a significant influence on build time. Descriptions of the welding system and temperature control technique are included as well as the surface measurement and residual stress assessment techniques used. Results of temperature versus time, surface finish versus temperature and temperature versus residual stress are presented and discussed.
Procedures for effective implementation of simultaneous engineering in small to medium enterprises
Authors: Hindson G A , Kochhar A K , Cook P
Published: October 2002

Simultaneous engineering (SE) has been developed by large multinational companies working in consumer oriented industries. This has meant that the implementation methods, tools and techniques have been geared towards these industries. 600 Lathes is a medium-sized company engaged in the manufacture of a variety of machine tools. The application of an SE approach in such environments requires the adaptation of its generic principles.

The initial use of SE on a new machine tool, the Tornado lathe, indicated the need for procedures to institutionalize this new method of working. A critical analysis of SE identified four generic principles that were used as a framework for product introduction. Procedures were developed drawing on organizational communication theory and involving the users. The aim was to create procedures with company-wide acceptance that were user friendly and worked. These procedures were used for the introduction of a second range of lathes, named Alpha. Their effectiveness was studied as a crucial part of the Alpha project review. This evaluation showed that procedures based on practical experience are readily adopted. Each procedure was necessary and integral to SE. Any company wanting to implement SE must tackle similar issues. The generic principles of SE are proposed as the method for developing effective procedures.
Techniques for firm tooling using rapid prototyping
Authors: Pham D T , Dimov S , Lacan F
Published: October 2002

This paper gives an overview of rapid tooling technologies that are, or shortly will be, available for production runs of up to several hundred parts in the same material as the final production part.
Computer-based selection of manufacturing processes: Methods, software and case studies
Authors: Esawi A M K , Ashby M F
Published: October 2002

A systematic procedure for selecting single steps of a process to manufacture a component is outlined. It is based on comparing the attributes required by the design (the required material, size, shape, precision and cost) with those that lie within the capacity of a large number of processes, seeking the subset which is capable of making the component. The subset is then ranked by economic criteria.
Application of the Taguchi method for consistent polymer melt production in injection moulding
Authors: Khoshooee N , Coates P D
Published: October 2002

The consistency of polymer melt production in the injection-moulding process has been studied using a Taguchi design-of-experiment method for acrylonitrile butadiene styrene (ABS) and high-density polyethylene. Systematic experimentation with injection-moulding machine settings helped to establish both qualitative and quantitative process understanding in attempting to control the melt quality, assessed here by the shot weight variability. Optimum machine settings were determined which gave the lowest variations in the shot weight. In the case of ABS, uncontrollable influences (noise factors; here the injection stroke and moisture content) were incorporated in the study in such a way that the optimum levels recommended by the analysis make the process (i.e. shot weight) insensitive to variations caused by the noise factors. The set melt temperature and screw-back pressure were observed to be the most influential control factors affecting the shot weight variability for both polymers.
The role of technical education, training and the engineering profession in the wealth-creating process
Authors: Denton A A
Published: October 2002

Engineering is in competition with other professions in seeking to attract the best young people, making it necessary to market engineering proactively as an attractive career prospect. The education to be provided to prospective engineers should equip them to perform competently in areas other than the strict engineering sciences, but, equally, it is argued that there is a requirement for the adoption of a more rigorous approach to the teaching of mathematics. In training, attention is drawn to the added value to be gained by employers who introduce formal mentored courses for graduates, and emphasis is given on the need in education and training to recognize the different roles that professional engineers have to play. The role of the engineering Institutions is discussed, with particular emphasis on their work in the area of accreditation and continuing professional development. The public relations role of the Institutions is also examined.
Design of special tools by CAD/CAM systems
Authors: Rico J C , Mateos S , Cuesta E , Suárez C M
Published: October 2002

This paper presents a program for the automatic design of special tools developed under a CAD/CAM (computer aided design/manufacture) system. In particular, the special tools made with standard components have been considered. Since the design of these types of tools was essentially related to the selection of their components, this paper deals with this aspect, insisting upon the selection of those components directly related to the removal of material: the toolholders or cartridges and the inserts. To select these components it is necessary to take into account not only geometrical or technological rules but also economical ones, owing to the high amount of possible components they can select. Consideration of economical aspects required the formulation of the cost equation associated with the use of these types of tools, characterized because their cutting edges coincide with different cutting velocities. Likewise, consideration of economical aspects allows the selection of the optimum cutting conditions and the cutting components to take place at the same time. Some of the geometrical and technological parameters related to the selection of cutting components are automatically identified by the system through an automatic identification of the workpiece profile.
Structured models to assist in justifying investment in knowledge-based systems
Authors: Oldham K , Kochhar A K , Hather R M , Halton J
Published: October 2002

This paper investigates the issues that should be considered before investing in knowledge-based systems. The desirability of having a knowledge-based system strategy is recognized and the issues associated with such a strategy are identified. Having defined the phases in the life-cycle of a knowledge-based system, models are proposed showing the activities and roles involved in the stages of opportunity identification and business case establishment. These models ensure that all relevant issues are addressed in a structured way. Particular attention is paid to the issues associated with people.
Pattern formation and linear stability analysis in centreless grinding
Authors: Epureanu B I , Dowell E H , Montoya F M
Published: October 2002

Quite often a centreless ground surface has an undesired wavy shape instead of a circular shape owing to a geometric instability. In this paper the equations describing the kinematics of the grinding process obtained by Rowe et al.(1) are used to build a linearized model that describes the formation and evolution of the pattern on the manufactured surface. The profile of the workpiece is discretized and linearly interpolated. Stable or unstable patterns or eigenvectors are obtained for the configurations of the centreless grinding system. Circular profiles are shown to appear for configurations that have no unstable patterns while wavy profiles appear for configurations that have at least one unstable pattern. Some of the most important non-linear effects are considered as limits on the exponential growth of the unstable patterns predicted by the linear analysis. Specifically, the non-linear analysis is based on the limited allowed curvature of the profile of the workpiece. Although it is an approximation of the real phenomena, the non-linear analysis is able to predict patterns that appear on the ground surface that are very close to the experimental observations even if unstable patterns are present.
Precision forging design and analysis in electronics part manufacturing
Authors: Park K , Yang D Y , Kang Y S
Published: October 2002

In order to increase the productivity of electrical parts, manufacturing processes using progressive dies have been widely used in the industry. With a progressive die, however, closed die forging is impossible because the part has to be connected with a strip layout so that there might arise various problems in the die design. For the proper design of a process, a prediction of the process is required to obtain relevant design parameters. In this work, three-dimensional rigid-plastic finite element analysis is carried out to simulate a precision forging process. The forging process of the stem, a part of a photo pickup hologram device, is simulated with two types of processes’ open die forging and semiclosed die forging. From the results of analyses, the forging processes can be predicted successfully, which enables the die and the process to be designed appropriately.
Integration of quality, environmental and health and safety management systems: An examination of the key issues
Authors: Wilkinson G , Dale B G
Published: October 2002

This paper reports the main findings of a study of five manufacturing companies in relation to their attitudes to the integration of quality, environmental and occupational health and safety management systems. It was found that less interest is shown in occupational health and safety management systems, ISO 14001 is preferred to EMAS and those organizations that have embraced the principles and mechanisms of total quality management are more likely to pursue integration than those that have not. Integration of management systems is also seen more readily by those organizations that have operations involving high hazards. It is also pointed out that system integration can be achieved in a number of ways and at different levels which are explored in the paper.
Feature-based robot machining for rapid prototyping
Authors: Song Y , Chen Y H
Published: October 2002

This paper presents the development of a robot machining centre for rapid prototyping (RP) applications. Given a three-dimensional model of an object, surface features of the model were extracted and analysed. Cutter paths for both rough and finish cutting were then generated on the basis of the extracted surface features. In order to detect collision between the robot arm and its environment, an accurate model was built using a computer aided design (CAD) system and the Denavit-Hartenberg (D-H) notation was used to represent the robot arm transformation matrix. When collision was detected for a given contact point, both cutter location and robot arm positions were modified. A simple ship model was machined to demonstrate the effectiveness of the robot machining centre. Finally machining errors were quantified with the use of a coordinate measuring machine (CMM).
Automated visual inspection for surface profile tolerancing
Authors: Lau K H , Ng K C
Published: October 2002

Achieving inspection automation is desirable in a production line in order to reduce labour cost and ensure consistent product quality. This paper presents an automated inspection system for a three-dimensional complex surface according to the specification of surface profile tolerancing. A range scanner is used to measure the surface profile of an object and an algorithm is designed to decide upon the acceptability of the part. The pyramidal generalized Hough transform is used to obtain a rough estimate of the object's pose in the three-dimensional world. This pose estimate is then refined over a linearized optimization process to achieve an optimal solution from which shape acceptability can be determined on the basis of a statistical interpretation. Experiments showed that the current inspection system is capable of registering objects having arbitrary deformations and that the system is capable of inspecting objects of complex shape.
A design reuse system
Authors: Shahin T M M , Andrews P T J , Sivaloganathan S
Published: October 2002

Successful past design is the largest accumulation of expertise in the entire manufacturing sector and effective exploitation needs to structure this store of information. This paper shows that the design model under which this information is going to be used greatly influences the structuring process. Within design function deployment past designs should be structured as (a) a product concept, (b) a solution concept, (c) an embodiment design and (d) a detailed design, for efficient reuse. Illustrative examples are provided to explain their reuse. The methods for representing the structured information are also described.
Chip control in tube turning using a high-pressure water jet
Authors: Crafoord R , Kaminski J , Lagerberg S , Ljungkrona O , Wretland A
Published: October 2002

A stable chip control using inserts with integrated chip formers is difficult, especially if the feed rate or cutting depth is not within the range recommended for the insert. This paper shows the possibility of controlling the chip upcurl radius in turning by using flat inserts without any chip formers. An experimental study was made of the skew cutting of an end of a pipe using a plain water jet with a pressure of up to 80 MPa and a flow of up to 8 l/min. The jet was directed perpendicularly to the cutting edge into the tool/chip interface. Investigations show that the chip upcurl radius can be successfully controlled. A correlation between water jet power, jet momentum and upcurl radius is presented and discussed. An empirical model of the above-mentioned correlation is also suggested.
Study and selection of grinding conditions Part 2: A hybrid intelligent system for selection of grinding conditions
Authors: Li Y , Rowe W B , Chen X , Mills B
Published: October 2002

A blackboard approach is presented for the selection of grinding conditions. The knowledge agents consist of case-based reasoning, neural network reasoning and rule-based reasoning. Case-based reasoning is employed as the main problem-solving agent to select combinations of the grinding wheel and values of control parameters. Rule-based reasoning is employed where relevant data have not yet accumulated in the case base. A neural network is employed to select a grinding wheel if required. The operator has ultimate control over the wheel or the values of control parameters selected. The blackboard approach combines the strengths of the different knowledge agents to generate hybrid solutions and overcomes the limitations of any single approach. The system works as expected and demonstrates the potential of using artificial intelligence for selection of grinding conditions, as well as the capability to develop a powerful database by learning from experience.
Direct experimental evidence of lubrication in a metal-on-metal total hip replacement tested in a joint simulator
Authors: Dowson D , McNie C. M. , Goldsmith A. A. J.
Published: October 2002

The purpose of the study reported in this paper was to investigate experimentally the conditions of lubrication and contact between a metallic femoral head and a metallic acetabular cup in a hip joint simulator. An electrical resistivity technique previously developed for engine tribology studies was used to detect the extent of surface separation throughout a cycle of dynamic loading simulating walking conditions. A metal-on-metal total joint replacement was tested in a single station of a ten-station hip joint simulator in the presence of five different lubricants. Two proteinaceous serum-based fluids of concentrations 25 and 100 per cent were used as well as three lubricants devoid of protein but of quite different viscosities.

It was observed that surface separation developed with both the protein-based fluids during the swing phase of the articulation and that an equilibrium cyclic pattern of contact and separation was established after running the simulator for some minutes. Furthermore, there was at times some evidence of separation during the severe conditions encountered during the stance phase. Silicone fluid failed to promote surface separation, while water and the more viscous carboxymethylcellulose solution yielded only modest periods of separation during the swing phase.

It was deduced from experimental and analytical features of the study that the mode of lubrication was mixed, with some periods of very effective surface separation and others of metal-to-metal contact. While the presence of protein was necessary for effective lubrication, the cyclic pattern of separation appeared to be determined by elastohydrodynamic action. The bond strength of the protein to the metals appeared to be weak. The partial film of lubricant between the boundary lubricating layers provided significant enhancement to the combined protective action in this mixed lubrication system.

The simple, cheap and effective electrical resistivity technique has revealed important new information on the tribological conditions in metal-on-metal hip joints which determine friction and wear. It can readily be adopted on most forms of total joint simulators. The technique and the findings reported here further advance the development of criteria for lubricants to be used in laboratory studies of the performance of total replacement joints.
Some contemporary problems in road vehicle dynamics
Authors: Sharp R. S.
Published: October 2002

It is argued that there is great commercial value in transferring as much of vehicle-handling qualities assessment as possible from the prototype testing domain to the predictive engineering domain. Man—machine system thinking is necessary to provide a firm basis for progress. Also, the newer opportunities in vehicle chassis engineering to introduce information enhancement and control intervention systems pose human factors problems. It is possible for such systems to do more harm than good. Some descriptions of conventional mixtures of prediction and testing are given and the driving activity is analysed. A conceptual framework involving the specification of vehicle characteristics, which contribute to the subjective judgements made by drivers, is set up. Examples in the categories are explained. The major chassis enhancement systems in production or in late development and their contributions in the various categories are discussed. Quality judgements are shown to be made by a very complex process, containing conflict and requiring very wide-ranging test conditions for the full picture to be revealed. It is considered that a conceptual classification, such as that put forward, is necessary to allow the design of research programmes which will yield fundamental, generic and practically useful results.
A validation study on mathematical models of speed and frequency dependence in seakeeping
Authors: Du S. X. , Hudson D. A. , Price W. G. , Temarel P
Published: October 2002

An extensive theoretical validation exercise is presented into the speed and frequency dependent solutions associated with surface piercing vessels travelling in waves. The basis of the study lies in the formulation of the Green's function satisfying the traditionally posed linearized boundary value problem of an oscillating ship with forward speed and the development/implementation of appropriate numerical schemes of study for solution.

Two widely different mathematical models in formulation and numerical algorithm, denoted as methods A and B, are discussed and employed to predict hydrodynamic coefficients, wave loads and responses of a Series 60 form and an NPL monohull. Only a selection of results are shown, but great care was taken in the overall investigation to verify and validate intermediate steps within the separate calculation procedures as well as to compare final predicted values.

The extensive qualitative and quantitative agreement of comparable results from methods A and B provides a measure of confidence that the presented findings are solutions to the posed seakeeping problem. The influence of speed and frequency dependence within the context of this study are discussed as well as a preliminary study into their influence in the occurrence of irregular frequencies in the numerical schemes.
Two centuries of the thermal regenerator
Authors: Organ A. J.
Published: October 2002

The paper looks back over almost 200 years taken to convert Stirling's original description of the thermal regenerator into a quantitative picture of transient thermal response. The ‘regenerator problem’ is found to be essentially the conjugate heat exchange problem by another name, and thus the subject of a massive literature, none of which, however, has, until recently, successfully addressed the problem of repeated flow reversals at low flush ratios. The gap in the repertoire is ironic, given that these are precisely the operating conditions of Stirling's original invention. An elementary transformation overcomes the difficulty of solving for any number of flow reversals at any flush ratio. Temperature-time histories are presented for the ‘classic’ problem with fixed entry temperatures. For sufficiently high thermal capacity ratio a straightforward and explicit solution emerges for fluid temperature history at cyclic steady state. The approach is shown to be sufficiently versatile to permit extension to the complex cyclic operating conditions of Stirling coolers and prime movers. Along the way it is noted that heat transfer correlations ( NSt N2/3Pr versus NRe) for wire gauzes frequently thought inapplicable to the regenerator by virtue of a supposed ‘steady flow’ connotation in fact owe their very existence to an early part-solution of transient thermal response. To this extent the correlations are the proper data to use.
Computer simulation of three-dimensional transport during moistened defatted soy flour processing in the metering section of a single-screw extruder
Authors: Ghoshdastidar P S , Ghai G , Chhabra R P
Published: October 2002

A quasi-three-dimensional steady state finite-volume-based computer model for a power-law fluid is used to describe the three-dimensional transport during the processing of defatted soy flour with 25, 28 and 33 per cent moisture contents by weight in the metering section of a single-screw extruder. The numerical results have been compared with the earlier experimental results of Fong. The results are found to be reliable only for the highest moisture content dough (33 per cent by weight). The conclusion is that the quasi-three-dimensional model showing a viscous drag flow mechanism using a power-law equation for viscosity may be effectively used for predicting the behaviour of moist doughs during the extrusion process while the same model may not be very reliable for drier doughs which show plug flow behaviour during processing.
An experimental investigation of torque signature signals for self-tapping screws
Authors: Seneviratne L D , Ngemoh F A , Earles S W E
Published: October 2002

The results of an experimental study on the self-tapping screw insertion process are presented. A test rig designed and constructed for measuring the torque signature signals during screw insertions is described. Experimental results for torque signature signals during general self-tapping screw fastenings are given graphically, confirming the five-stage variation with screw insertion depth predicted by an earlier theoretical study. The experimental data provide a basis for the further development of empirical and theoretical models of the self-tapping screw fastening process, in order to formulate and put into practice automated monitoring and control strategies.
The application of a correlation dimension in large rotating machinery fault diagnosis
Authors: Wang W , Chen J , Wu Z
Published: October 2002

This paper reports on the application of the correlation dimension in large rotating machinery fault diagnosis. The Grassberger-Procaccia algorithm and its modified version are introduced. Some important influencing factors relating directly to the computational precision of the correlation dimension are discussed. Industrial vibration signals measured from large rotating machinery with different faults are researched using the above-mentioned methods. The results show that the correlation dimension can provide some intrinsic information on an underlying dynamic system and can be used to classify different faults intelligently.
Experimental study for a heat transport device using magnetic fluid: Improvement by a regenerative thermomagnetic heat cycle
Authors: Yamaguchi H , Kobori I , Kobayashi N
Published: October 2002

Heat transporting characteristics are investigated experimentally for a heat transport device using a temperature-sensitive magnetic fluid. In the present study, in particular the regenerative thermomagnetic heat cycle is considered by allowing heat conduction in the inner pipe wall of the device. According to the heat transport configuration studied, the lower end of the device is heated while the upper end is cooled isothermally when the device is placed vertically. Experimental results show that a relatively high amount of heat can be transported in comparison with the case of an adiabatic inner pipe wall, indicating that the thermomagnetic heat cycle in the device is improved. The correlation obtained from one-dimensional analysis provides a reasonable means of assessing estimating experimental data when the thermomagnetic heat cycle based on the working principle is satisfied.
Safety of fall arrest systems: A numerical and experimental study
Authors: Drabble F , Brookfield D J
Published: October 2002

Workers in elevated positions must be protected from falling or from the hazardous consequences of falls. Protection from falling can include fences, guard rails, etc., or a restraint system preventing the workers from reaching any point from which they can fall. However, protection from falling can be impractical and in such situations a fall arrest system (FAS) must be provided such that the fall does not cause injury to the worker or to others. This paper surveys prior work on the analysis of FASs including the energy balance method historically used. This method is limited to simple FASs where only one worker may fall. A novel numerical analysis technique for predicting the forces occurring in each component of an FAS during a fall is then described. Results from the numerical analysis are compared with results from experimental tests and with those from the energy balance method. It is shown that the numerical analysis technique predicts forces to within better than approximately 7 per cent, the method being conservative, whereas the errors shown by the energy balance method exceed 26 per cent. The new analysis method is also shown to be applicable to multiple falls.
An electrodynamic shaker with an integral force gauge for high-frequency measurements on lightweight structures
Authors: Grice R M , Pinnington R J
Published: October 2002

The design, construction and calibration of a purpose-built electrodynamic shaker for making frequency response function measurements on lightweight structures at high frequencies (i.e. many kHz) are described. The shaker uses a conventional wire-wound coil onto which is assembled a force gauge. The force gauge is constructed using little more than just a miniature piece of piezoelectric material. The dimensions of the components used to manufacture the shaker are determined by comparing their estimated dynamic behaviour with the estimated mobility of a lightweight perspex test structure. Although such an electrodynamic shaker is not entirely novel, it demonstrates how careful use of basic materials can produce a device that overcomes some limitations of commercial devices at very little cost.
The vibration of a corrugated carbon fibre pressure vessel under external hydrostatic pressure
Authors: Ross C T F , Little A P F
Published: October 2002

The paper presents a theoretical and an experimental investigation into the vibration of a corrugated carbon fibre cylinder in air and under external water pressure. The theoretical investigation was via the finite element method, where both the shell and the surrounding water were modelled with axisymmetric finite elements. In the case of the shell, the element allowed for orthotropicity and in the case of the water, the element was a solid element with an isoparametric cross-section. Good agreement was found between experiment and theory for both the vibration in air and the vibration under external water pressure. The results showed that as the external water pressure was increased, the resonant frequencies decreased. This appeared to agree with previous findings that a form of dynamic buckling could occur when the vibration eigenmode was the same form as the buckling eigenmode, in response to a periodic excitation force.
Application of wavelet analysis to the impact harshness of a vehicle
Authors: Lee S K , White P R
Published: October 2002

The impact harshness of cars is an important factor in ride comfort. Traditionally, impact harshness is evaluated via subjective measurements based on the experience of test drivers. Objective evaluations are more efficient and reproducible than subjective measurements. Thus, this paper develops an objective measure based on a few signal parameters, specifically the initial peak values and damping ratios of the major vibration modes. A method based on the continuous wavelet transform is presented for the measurement of damping ratios. The performance of the method for estimating damping ratios is illustrated by the use of synthetic data, while performance of the objective measure is assessed on the basis of a series of trials on real vehicles.