bluuebunny/crossref_metadata_2025 huggingface dataset:
Implementing a model-based generic user interface for computer integrated manufacturing systems
Authors: Monfared R P , Hodgson A , Bowen B A , West A A
Published: October 2002

Computer integrated manufacturing (CIM) systems are complex in terms of performing a variety of activities, maintaining a range of information and involving various classes of users with differing levels of knowledge and skills, and different levels and time spans of decision making. Much investment and effort has been made to formalize and automate the performance of the CIM elements in a manufacturing system. However, each CIM subsystem will typically have its own terminology, procedures and presentation formats. This places a heavy and unnecessary burden on users, resulting in frustration and reduced effectiveness.

Research has been carried out by the Manufacturing Systems Integration Research Institute at Lough-borough University towards the generation of a user-oriented interface for CIM systems. This research has resulted in a conceptual approach, which incorporates a generic user—task model, which enables the generation of flexible and reusable software components to form a semigeneric user interface for CIM users. The CIM user interface provides presentation tools to monitor and control the performance of the CIM elements.

Advanced modelling and integration technologies have been deployed to enable the system to cover a wide area of manufacturing domains. These technologies include modern manufacturing modelling architectures such as CIMOSA and GERAM, and advanced communication techniques such as those used by Web-based software applications in manufacturing environments.

The implementation issues of the generic user interface concept, together with its application within an industrial case study are discussed in this paper.
The effects of exposure time on tackiness and rheology of solder paste
Authors: Hui I K , Ralph B
Published: October 2002

The quality of printing and reflow in surface mount technology depends very much on the selection of a solder paste with suitable tackiness and rheology. A series of studies has been conducted to find out the effects of exposure time of the solder paste on its tackiness and rheology. A qualitative method was designed for tackiness analysis. The results of the analysis show that tackiness decreases as exposure time increases and their relationship can be expressed by a power law. It is recommended that the values of the characteristic constants in the power law should be provided as part of the solder paste specification to facilitate calculation of the decay in tackiness over time by the user. The Malcom system was used to investigate rheology changes of the solder paste. Based on the solder paste used for the investigation, it was found that the viscosity increases with exposure time and becomes stable at about 2 h. On a log—log scale plot the viscosity and shear rate have a linear dependence on time of exposure for all solder pastes, and their thixotropy indices remain almost unchanged. However, the non-recovery rate, used for measuring the recovery ability of the solder paste, decreases rapidly in the first 40 min of exposure and then remains almost unchanged.
Calculation of drawbead restraining forces with the Bauschinger effect
Authors: You Y
Published: October 2002

In this paper, a numerical model for the calculation of the drawbead restraining force is described. The model is formulated using an elastoplastic finite deformation, finite element method. Because of the bending, unbending and reverse bending deformation which occurs as the sheet metal passes through the drawbead, a kinematic hardening constitutive law associated with a description of the cyclic property and the Bauschinger effect is considered. In comparison with experiments, the results based on the kinematic hardening material model proved to be better than those based on the usual isotropic hardening material model.
Thermal modelling of cutting front edge dynamic behaviour in high-power reactive CO2 laser cutting
Authors: Chen S-L
Published: October 2002

The sheer number of non-linear interacting factors responsible for the performance of laser cutting makes it impractical, in general, to investigate all the factors by experimental method only. To understand further the essential phenomena of the oxidation reaction in reactive CO2 laser cutting, a mathematical model was created in this research to investigate the effects of cutting parameters on the cutting front edge dynamic behaviour. Understanding the effects of various parameters is important for improving the performance and quality of laser cutting. The reactive CO2 laser cutting of a thin metallic plate utilizing a continuous-wave laser beam having a Gaussian intensity distribution was considered in this study. Both the beam absorptivity and the heat generated at the cutting front edge during the reactive cutting process were considered in this research. The numerical results of this work can be used to predict or estimate the variations in the location, speed and acceleration of the cutting front edge, given various gas compositions, gas pressures, cutting speeds and beam absorptivities. An on-line monitoring system for laser cutting was built, and a series of experiments was performed to record the fluctuating frequency of the cutting front edge. The results confirm that our theoretical results were in accordance with the related experimental results.
Description of the contact between a deterministic anisotropic tool surface and a workpiece subjected to plastic deformation
Authors: Rotarescu M-I
Published: October 2002

The finite element method offers an opportunity to obtain important information by simulating metal-forming processes. The description of the tool—workpiece interaction still remains a critical issue. The aim of this paper is to describe the contact between a deterministic anisotropic tool surface (grooved) and a workpiece. This is done by means of an existing contact processor and a friction law that has been conceived to describe sliding friction. This compromise solution of describing a contact state near to sticking by means of a law created for sliding friction is investigated. The results obtained using a macrogeometric model of the grooved surface are compared to those achieved by an idealized smooth surface and different friction coefficients. Next, an anisotropic model is introduced and calibrated using the inverse method based on the ring upsetting test for a hot-worked steel.
Monte Carlo simulation and analysis of free-form surface registration
Authors: Brujic D , Ristic M
Published: October 2002

Accurate dimensional inspection and error analysis of free-form surfaces requires accurate registration of the component in hand. Registration of surfaces defined as non-uniform rational B-splines (NURBS) has been realized through an implementation of the iterative closest point method (ICP). The paper presents performance analysis of the ICP registration method using Monte Carlo simulation. A large number of simulations were performed on an example of a precision engineering component, an aero-engine turbine blade, which was judged to possess a useful combination of geometric characteristics such that the results of the analysis had generic significance. Data sets were obtained through CAD (computer aided design)-based inspection. Confidence intervals for estimated transformation parameters, maximum error between a measured point and the nominal surface (which is extremely important for inspection) mean error and several other performance criteria are presented. The influence of shape, number of measured points, measurement noise and some less obvious, but not less important, factors affecting confidence intervals are identified through statistical analysis.
An application of the energy barrier to prismatic 2 1/2-dimensional parts of uniform cross-section with non-orthogonal contiguous faces
Authors: Lee S G , Lye S W , Ngoi B K A , Lim L E N
Published: October 2002

The energy barrier method, first proposed by Boothroyd and associates, can be used to determine the probabilities of the natural resting aspects of objects to be conveyed on and oriented by vibratory devices. However, for parts of uniform cross-section other than square or rectangular ones, the application of the method can be intractable. In such cases, Boothroyd and associates recommended circumscribing the part by a cylinder and using the energy barrier for the cylinder to approximate the probabilities of the natural resting aspects of the part. This approximation is understandably inexact although computationally expedient. This paper outlines the CAD (computer aided design) computation of the probabilities from the energy barriers for two objects: one, a triangular prism with equilateral sides (representing objects with adjacent faces that are not mutually perpendicular) and the second, an L-shaped prism with a virtual resting aspect. The significance of the centroid plane of the part in the determination of the probabilities is discussed. The CAD computations were carried out using the Graphical Interface Programming (GRIP) Language of McDonnell Douglas' UniGraphics II™ CAD system running on a DEC 9000 workstation.
Energy analysis and quality evaluation of pulsed neodymium-doped yttrium aluminium garnet laser cladding ceramic-metal composite coating on aluminium alloys
Authors: Chen S-L , Hsu R-L
Published: October 2002

This research addressed an ‘energy threshold’ evaluation method for pulsed Nd-doped yttrium aluminium garnet (Nd-YAG) laser cladding. A high-power pulsed Nd-YAG laser was selected as the main equipment to investigate the performance of laser cladding ceramic-metal composite coating on Al alloys. Additionally, the basic characteristics of pulsed Nd-YAG laser for cladding processing were analysed. Three important system parameters of the pulsed Nd-YAG laser were isolated as the key factors that significantly affect cladding quality: Cladding speed, pulse width and laser power (pumping current). The experimental results were carefully analysed and evaluated. Firstly, the evaluation procedures included cladding track observation. The integrity of the tracks was used to judge whether the cladding was successful or inadequate. Secondly, the cross-section of the cladding layer was measured and examined. Three indexes of cladding quality (the thickness, the penetration depth and the shrinkage cavity area in the cladding layer) were analysed. From these evaluations, it was found that the pulse energy is the critical factor for pulsed Nd-YAG laser cladding. The research results also suggest that the minimum pulse energy Ep∗ may be adopted as the ‘energy threshold’ for continuously and successfully cladding the ceramic-metal composite on Al alloys.
Investigation into the automation of incremental forming processes
Authors: Osman F H , Ferreira J
Published: October 2002

Incremental deformation is a low-cost manufacturing process which requires low-energy machines. Open die forging is a type of process in which a large variety of simple tools, plain and profiled, are employed to produce complex shapes by incremental deformation. In its traditional form, the process is carried out manually, thus requiring experience and intelligent manipulation of the workpiece material. The development of a new operating environment for open die forging will increase its competitiveness in the global market where the small-batch manufacturing mode has become an essential feature of the new production trends. This paper presents a new on-line computer controlled set-up in which the workpiece material is manipulated via a step-by-step computerized schedule. Accurate interaction between the workpiece orientation and the action provided by the tools is achieved by the use of step motors and a feedback loop. Also, an analytical approach to predict the mode of deformation after an incremental step effected by a semicircular tool has been presented and the results compared with those obtained experimentally.
Environmentally clean metal cutting processes—machining on the way to dry cutting
Authors: Popke H , Emmer Th , Steffenhagen J
Published: October 2002

The growing importance of environmental aspects cannot be denied by manufacturing businesses. An important factor to be considered is the use of cutting fluids in machining processes. This paper presents concepts that need to be considered in companies that extensively use cutting fluids, and not only for environmental reasons. Based on these concepts, the improvement and practical realization of minimum quantity cutting fluid application and dry cutting are shown. In this paper experimental results and effects on tool life and part quality are presented and discussed for drilling, counterboring and reaming processes.
An analytic hierarchy process approach to the choice of manufacturing plant layout
Authors: Abdul-Hamid Y T , Kochhar A K , Khan M K
Published: October 2002

The type of plant layout has very significant impact on the structure and operation of a manufacturing system. The current common and intuitive methods of selecting a suitable type of layout by using simple graphs of production volume versus number of parts manufactured in the plant, or production volume versus flexibility, can result in inaccurate decisions for such an important issue. This paper presents an alternative approach to the choice of plant layouts, which applies the Analytic Hierarchy Process (AHP). The methodology considers three main objectives for the selection of layouts: increasing flexibility, increasing production volume and reducing manufacturing costs. Each objective has a number of subobjectives. Three main types of layout are considered: functional (process) layout, group technology (cellular) layout and transfer (flow) lines. The AHP methodology has been applied as a knowledge-based system, which is integrated with another three knowledge-based systems for the technical and social conditions required for the successful implementation of each of the above types of layout. An example of the application of the AHP methodology is presented, which represents an important step towards proper validation of the methodology.
The detrimental effect of non-metallic inclusions during metal forming processes
Authors: Riedel U T , Morgan J E , McMahon C A , Guild F J , Bleck W
Published: October 2002

The presence of non-metallic inclusions can result in material failure during the metal forming process or lead to a serious deterioration in the quality of the final product. Understanding the effects of inclusions during metal forming is therefore an important step towards predicting the behaviour of inclusions and subsequently minimizing their consequences.

To aid this understanding the authors have carried out a finite element (FE) analysis into the effect that metal inclusions have during metal forming, and specifically the effect of non-metallic inclusions in rod drawing [1, 2]. The FE analysis was verified using experiments that simulated the rod drawing process. It is part of the results of these experiments which is briefly described in this paper. An aluminium oxide (Al2O3) sphere was embedded into an axially split rod which was then drawn through a carbide die. The subsequent deformation of the rod around the Al2O3 inclusion was studied. In addition, fracture of the rod, initiated at the inclusion, was observed.
Selective laser sintering: Applications and technological capabilities
Authors: Pham D T , Dimov S , Lacan F
Published: October 2002

Rapid prototyping (RP) models are no longer used only for design verification. Currently, parts built utilizing layer manufacturing technology can be employed as functional prototypes and as patterns or tools for different manufacturing processes such as vacuum casting, investment casting, injection moulding, die casting and sand casting. The selective laser sintering (SLS) process is becoming widely used in industry, its main advantage over other RP processes being that it can produce parts in a wide range of materials. This paper describes applications of some of the materials available with the SLS process and, by means of case studies, explains the technological capabilities of this process.
The generation and practical use of plans for manual assembly using immersive virtual reality
Authors: Ritchie J M , Dewar R G , Simmons J E L
Published: October 2002

The preparation of assembly plans for manufactured goods is a major bottleneck in the time it takes to bring many new products to market. Computer aided assembly planning (CAAP) systems have been the subject of considerable research in recent years without achieving significant up-take in manufacturing industry. This paper proposes an alternative approach based on the adoption of immersive virtual reality, which is used here to produce practical downstream manufacturing information. The product is assembled from computer aided design (CAD) models of its components by experienced assembly operators working in a virtual environment. The operators' actions are monitored and assembly sequence plans are automatically generated by the system. In the research described in this paper, the plans produced for an advanced electromechanical product were then used by a second group of participants to demonstrate the functionality of the system in an industrial environment. The development of virtual reality-based assembly planning carries with it the opportunity not only to shorten the product innovation cycle but also to capitalize on the experience of assembly operators and bring this to bear much earlier in the design process.
Simulation study of an agile high-speed machining system for automotive cylinder heads
Authors: Omar M , Hussain K , Wright S
Published: October 2002

There is a continuous need within most manufacturing environments for more flexible production equipment, particularly where customer satisfaction and responsiveness promote quality improvement. In this paper, an automated agile manufacturing system that uses high-speed computer numerically controlled (CNC) machines to make automotive cylinder heads is proposed and evaluated by means of discrete event simulation using the ARENA simulator. Two alternative agile system configurations are constructed and simulated to achieve the production target. The simulation shows some significant benefits in using the agile system and demonstrates that high-speed CNC equipment is a viable option for cylinder head manufacture at a production volume of 550 000 units per annum. It is shown that the agile system can provide more flexibility and half the throughput time of the transfer line.
Quality information feedback within a contemporary metalworking smaller manufacturing enterprise
Authors: Bagshaw R W , Newman S T
Published: October 2002

This paper reports ongoing research into a workshop-oriented PC-based machining and inspection and analysis facility within a contemporary metalworking smaller manufacturing enterprise (SME). It identifies a novel manufacturing and inspection framework, which is supported by the use of information models. A major feature of the framework is the ability to produce rapid manufacturing control through feedback data from both the inspection and production data analysis activities in order to influence the responsiveness to manufacturing disturbances experienced through the machining of discrete prismatic components. The major contribution of this paper explores a production data analysis (PDA) concept, which forms the basis of a prototype facility that closes the manufacturing feedback loop void that exists in the metalworking SME. The paper outlines the three major constituents of the prototype PDA facility, namely machine and inspection planning, comparative tolerance analysis and manufacturing data analysis and the information resources contained within a quality information feedback model (QIFM).
A concurrent design system for machined parts
Authors: Pham D T , Ji C
Published: October 2002

Detailed manufacturing information about the part being designed can help the designer to specify appropriate manufacturing methods and satisfy cost constraints. A prototype concurrent design system has been developed in which information concerning features in the design is provided to the designer. The information supplied includes manufacturability assessment, machining schemes, cutting tool types and cutting parameters, the tolerances and surface finish to be achieved and pure machining times. The system extracts geometrical and technological information regarding a part from its computer aided design (CAD) model and generates the required manufacturing information.
A single representation to support assembly and process planning in feature-based design machined parts
Authors: Case K , Harun W A Wan
Published: October 2002

The need for a product model that can support the modelling requirements of a broad range of applications leads to the application of a feature-based model within a computer aided design environment. An important requirement in feature-based design for manufacture is that a single feature representation should be capable of concurrently supporting a number of different applications. Assembly and process planning are seen as two crucial manufacturing applications and a formal structure for their representation in a feature-based design system is presented. This research addresses two basic questions relating to the lack of a unified definition for features and the establishment of a feature-based representation for assembly. Thus the concept of designing with features is extended by incorporating assembly and process planning information with the geometrical and topological details of component parts. A prototype system has been implemented using an object-oriented programming technique which provides a convenient method for adding functionality to the geometric reasoning process of features and the complex relationships between the parts that make up the assembly. The feature-based model is embedded in the ACIS object-oriented solid modeller kernel.
The borderline of elastohydrodynamic and boundary lubrication
Authors: Spikes H
Published: October 2002

There is a growing trend for lubricated systems to operate for much of their operating life with very thin lubricating films. This paper reviews our current understanding of such films, at the borderline between elastohydrodynamic and boundary lubrication. The nature and properties of these films are very complex, since the proximity of the solid surfaces influences the structure and rheology of thin liquid layers, while boundary films can, themselves, possess rheological characteristics that vary with thickness.

Novel experimental tools, such as atomic force microscopy and ultra-thin-film interferometry have greatly accelerated our understanding of this area in the last few years and it has recently become possible to map lubricant film thickness within rough surface contacts. These tools are beginning to provide the level of understanding of thin-film rough surface behaviour required to develop accurate numerical and simulation models. The next 5 years should see a very rapid progression of our understanding of this important regime.
Determination of the optimum performance of gas turbines
Authors: Horlock J. H. , Woods W. A.
Published: October 2002

Earlier analytical and graphical treatments of gas turbine performance, assuming the working fluid to be a perfect gas, are developed to allow for ‘non-perfect’ gas effects and pressure losses. The pressure ratios for maximum power and maximum thermal efficiency are determined analytically; the graphical presentations of performance based on the earlier approach are also modified. It is shown that the optimum conditions previously determined from the ‘air standard’ analyses may be changed quite substantially by the inclusion of the ‘real’ effects.
Observations on the vibration of axially tensioned elastomeric pipes conveying fluid
Authors: Zhang Y L , Gorman D G , Reese J M , Horacek J
Published: October 2002

A study of the effect of axial tension on the vibration of a single-span elastomeric pipe clamped at both ends conveying fluid has been carried out both experimentally and theoretically. A new mathematical model using a penalty function technique and the method of kinematic correction and fictitious loads has been developed. The influence of flowing fluid and axial tension on natural frequencies and mode shapes of the system has been described using this model and compared with experimental observations. Linear and non-linear dynamic response of the harmonically excited pipe has also been investigated for varying flow velocities and initial axial tensions.
Theoretical modelling of cavitation in piston ring lubrication
Authors: Priest M , Dowson D , Taylor C M
Published: October 2002

Mathematical models of piston ring dynamics and lubrication are sensitive to the boundary conditions adopted to describe the cavitation occurring in the diverging outlet region of the lubricant film between the piston ring and cylinder wall. In this paper, such sensitivity is investigated by applying different models of gaseous cavitation, flow separation and fluid film reformation to the analysis of a single compression ring from a diesel engine. Significant differences are predicted in hydrodynamic pressure profiles, lubricant film boundaries, lubricant film thickness, oil flow and friction.

Such indications of substantial differences in piston ring operating characteristics associated with the distinct cavitation boundary conditions considered highlights the need for further research in this field. However, the lack of detailed experimental data to validate the predictive models suggests that future progress must be based upon combined theoretical and experimental approaches to the problem. It is postulated that boundary conditions based upon Reynolds cavitation and fluid film reformation may be applicable at high loads, and fluid film separation of a form proposed by Coyne and Elrod at low loads.
A new equation representing the performance of kinematic Stirling engines
Authors: Prieto J I , González M A , González C , Fano J
Published: October 2002

Previous work carried out for the last eight years resulted in the proposal of a complete system of dimensionless groups in order to represent the performance of different kinematic Stirling engine configurations. When looking for experimental support for the proposed model, some differences between the performances of several prototypes were observed. In this paper an equation is introduced to be applied to all known kinematic engines and to their whole range of performance. The coefficients appearing in this equation can be computed from temperature and geometrical dimensionless ratios and from experimental measurements at the maximum indicated power operating point. The meaning of those coefficients is interpreted and their usefulness to provide an engine performance overview is shown. The quasi-static simulation and the characteristic Mach number at the maximum indicated power operating point appear to be interesting criteria in order to evaluate the performance of prototypes.
Finite element prediction of the ultimate collapse strength of casings
Authors: Huang X , Mihsein M
Published: October 2002

Accurately predicting the ultimate collapse strength is very important for casing design. For an infinitely long thick-walled casing under external pressure, a finite element method (FEM) model has been proposed to obtain a better understanding of the ultimate collapse strength of a casing. A very careful comparison with a series of experimental data has been conducted to verify the accuracy and reliability of the proposed FEM model. In addition, the predicted post-collapse behaviour compares well with the experimental test data. The validation proves that, if the material behaviour and imperfection variables are known, the ultimate collapse strength can be predicted to a satisfactory degree of accuracy. The major factors that affect the ultimate collapse strength of a casing have been fully investigated using the proposed FEM model.
Robust neuro control for rotating disc vibrations
Authors: Lin C-L , Liu V-T , Hao P-S
Published: October 2002

A novel robust-neuro control scheme for rotating disc vibrations is explored. In the approach proposed, a robust controller is first adopted to suppress the regulation error resulting from the unmodelled residuals while avoiding the spillover effect. In addition to the robust controller, a multilayer feedforward neural network is introduced to improve regulation performance. To maintain loop stability during neural network learning, a confinement algorithm for adaptive adjustment of the network weights is investigated. Simulation studies for a flexible rotating disc show that the control scheme proposed provides fast vibration suppression while maintaining robust stability.
Resolution of redundant manipulators via distance optimization
Authors: Ding M Z , Ong C J , Poo A N
Published: October 2002

Redundant manipulators are useful in practice as they have freedom in addition to that needed for a specific end-effector position. This additional freedom has to be properly resolved, and such redundancy resolution problems have been actively studied over the past decade. The most common scheme for redundancy resolution is achieved at the joint velocity level and does not take into account the presence of obstacles. This work presents a new scheme for redundancy resolution based on maximizing the shortest distance to obstacles. The aim is to resolve the redundancy by reconfiguring the robot to be at the safest pose or furthest from obstacles. The proposed scheme resolves the redundancy at the joint position level and, hence, has the advantage of ensuring collision-free motion. Several numerical examples in two- and three-dimensional spaces demonstrate the effectiveness of the proposed scheme.
Identification of fluid flow regimes in narrow cracks
Authors: Bagshaw N M , Beck S B M , Yates J R
Published: October 2002

The problem of fluid seepage through the cracked walls of pressure vessels has been examined. A simplified two-dimensional computational fluid dynamics (CFD) model of water passing through a narrow crack has been constructed and the results compared with published data. The CFD modelling process was validated by experimental work on two geometrically identical idealized crack bodies. The flowrate of air through the crack as a function of opening displacement was measured using the smaller apparatus, and the corresponding flow patterns were observed using smoke particles in the larger air flow apparatus. Four distinct flow regimes have been identified when the opening displacement of the crack is less than 3 times the surface roughness of the crack faces.
A numerical solution for a soft line elastohydrodynamic lubrication contact problem with sinusoidal roughness using the Chebyshev polynomials
Authors: Jaffar M J
Published: October 2002

A sinusoidal roughness model for the elastohydrodynamic problem of a low elastic modulus semi-infinite solid is investigated numerically. Both pressure and surface deformation are expanded in terms of the Chebyshev polynomials of the first kind Tn (x), and hence the governing equations are reduced to a finite set of non-linear equations using the orthogonality property of Tn (x). The influences of the elasticity parameter and the rough surface parameters, such as roughness amplitude, wavelength and phase angle, are examined. The obtained results show good agreement with existing results for a smooth model, and similar characteristics to those reported for a rough elastic layer.
Two-phase flow in orifice plates and valves
Authors: McNeil D A
Published: October 2002

The pressure drop that occurs when a two-phase flow passes through a pipeline component is usually found by calculating the single-phase value and multiplying it by a two-phase multiplier. Little or no consideration is given to what occurs within that component. For example, if the valve seat area is sufficiently small, the fluid velocity will approach, or even reach, the critical velocity. In these circumstances, compressibility effects should be accounted for—they rarely are. This study was initiated to develop a technique that would allow pressure drops to be predicted for pipe fittings, whether the flow is compressible or not, and to allow the critical mass flux to be estimated, thus allowing the method to be applied to the design of venting systems. The model developed can be used for all pipe fittings of the contraction-expansion type, like orifice plates and valves, up to and including the choking point, provided the single-phase loss coefficient is known.
Coupled solution of the elastohydrodynamic line contact problem using a differential deflection method
Authors: Hughes T G , Elcoate C D , Evans H P
Published: October 2002

This paper describes how a differential deflection technique for determining the deflection due to pressure acting on a semi-infinite body can be incorporated into solution schemes for the elastohydrodynamic lubrication (EHL) line contact problem. The method allows a fully coupled approach to be used without the full matrix penalty usually associated with that technique. This is achieved by the differential deflection method which specifies the deflection in a distributed implicit way rather than a specific explicit way. The differential deflection method is shown to give unchanged results with a radical reduction in the computing time required. It thus makes the inherent benefits of full coupling of the elastic and hydrodynamic equations available to EHL solution schemes without the computational penalty that has hitherto been associated with that approach.
Pressure wave attenuation in an air pipe flow
Authors: Wang H , Priestman G H , Beck S B M , Boucher R F
Published: October 2002

Pressure wave transmission attenuation in an air pipe flow is investigated both theoretically and experimentally. This investigation is to ensure the viability of remote flow measurement in an air pipe flow using a new fluidic pressure-pulse-transmitting flowmeter. The novel flowmeter produces self-induced oscillations, whose frequency is proportional to the flowrate. These pressure waves are transmitted via the flowing fluid and can be detected far downstream of the device. Experimental work has been conducted to ascertain how much the pressure waves are attenuated in air flow in a pipeline. This was done by using pipes of 0.05m diameter and both 4.7 and 28.5m long installed downstream of the flowmeter. A method of network simulation known as transmission line modelling (TLM), which has been programmed as the Sheffield University Network Analysis Software (SUNAS) code, is described and utilized to predict the wave decay through the air pipe flow. The theoretical and experimental results were found to give good agreement, demonstrating both the value of the modelling software and the viability of the remote flow measurement concept.
Spring constants of filament-wound composite circular rings
Authors: Tse P C , Reid S R , Ng S P
Published: October 2002

Closed-form solutions from complementary strain energy are derived for the spring stiffnesses of mid-surface symmetric, filament-wound, composite circular rings under unidirectional loading. A three-dimensional finite element analysis (FEA) including the effects of transverse shear has also been applied to study the problem. Four > 45° and four > 75° E-glass/epoxy composite rings of odd numbers of covers were tested. Comparisons of the results obtained from the two methods with experimental data are made and the results are found to be in good agreement. The FEA prediction of stiffness is always higher than the theoretical result. The relationships between the spring stiffnesses and the winding angles and geometry of the filament-wound composite ring are considered and discussed.
Modelling the flow distribution through automotive catalytic converters
Authors: Benjamin S F , Haimad N , Roberts C A , Wollin J
Published: October 2002

Conventional computational fluid dynamics (CFD) methods for simulating the flow through automotive exhaust catalysts assume a monolith resistance based on one-dimensional laminar flow. This underpredicts the flow maldistribution in the monolith. Incorporation of an additional pressure loss accounting for entrance effects improves predictions for the maximum flow velocity within the substrate.
Analytical treatment of tube drawing with a mandrel
Authors: Alexandrova N
Published: October 2002

An upper-bound analysis is used to estimate the required power in tube drawing and ironing of rigid, perfectly plastic material through a conical die. The frictional stresses exerted by the die and the mandrel on the material have constant values. The proposed kinematically admissible velocity field accounts for the singular behaviour of the real velocity field in the vicinity of the maximum friction surface. An optimal die angle is determined. The analysis agrees favourably with experiments and other theoretical solutions.
Gear condition monitoring by a new application of the Kolmogorov—Smirnov test
Authors: Andrade F A , Esat I I , Badi M N M
Published: October 2002

This paper introduces a new technique for the vibration condition monitoring of a set of spur gears. This technique, the Kolmogorov—Smirnov (KS) test, is based on a statistical comparison of two vibration signatures, which tests the ‘null hypotheses that the cumulative density function (CDF) of a target distribution is statistically similar to the CDF of a reference distribution’. In practice, the KS test is a time-domain signal processing technique that compares two signals and returns the likelihood that the two signals are statistically similar (i.e. have the same probability distribution function). Consequently, by comparing a given vibration signature with a number of template signatures for known gear conditions, it is possible to state which is the most likely condition of the gear under analysis. It must be emphasized that this is not a moment technique as it uses the whole CDF instead of sections of the CDF.

In this work, the KS test is applied to the specific problem of direct spur gear condition monitoring. It is shown that this test not only successfully identifies the condition of the gear under analysis (brand new, normal, faulty and worn out), but also gives an indication of the advancement of the crack. Furthermore, this technique identifies cracks that are not identified by popular methods based on the statistical moment and/or time-frequency (TF) analysis and the vibration signature. This shows that, despite its simplicity, the KS test is an extremely powerful method that effectively classifies different vibration signatures, allowing for its safe use as another condition monitoring technique.
Distributed-element Preisach model for hysteresis of shape memory alloys
Authors: Song C , Brandon J A , Featherston C A
Published: October 2002

The paper describes the development of distributed-element models for non-linear hysteresis in materials and structures. The physical model is based on an approach that views the system as comprising a series of ideal elastoplastic elements. Parameter identification, numerical simulation and inversion of the model through the application of the Preisach model for hysteresis are discussed. Experimentally obtained data using Nitinol are compared with the model prediction, thus establishing the effectiveness of distributed-element Preisach elements for predicting complex hysteresis effects including high-order hysteresis transition curves.
A shrink-fitted peg of finite depth subjected to a tensile load
Authors: Mugadu A , Hills D A
Published: October 2002

The load required to initiate slip of a shrink-fitted peg is found. For higher loads, the depth of slip penetration is determined, and, finally, the load producing complete extraction of the peg is calculated. Each solution is found as a function of the coefficient of interfacial friction and the normalized clamping stress.
Finite element modelling and load share analysis for involute worm gears with localized tooth contact
Authors: Yang F , Su D , Gentle C. R.
Published: October 2002

A new approach has been developed by the authors to estimate the load share of worm gear drives, and to calculate the instantaneous tooth meshing stiffness and loaded transmission errors. In the approach, the finite element (FE) modelling is based on the modified tooth geometry, which ensures that the worm gear teeth are in localized contact. The geometric modelling method for involute worm gears allows the tooth elastic deformation and tooth root stresses of worm gear drives under different load conditions to be investigated. On the basis of finite element analysis, the instantaneous meshing stiffness and loaded transmission errors are obtained and the load share is predicted. In comparison with existing methods, this approach applies loaded tooth contact analysis and provides more accurate load capacity rating of worm gear drives.
Contact and elastohydrodynamic analysis of worm gears Part 2: Results
Authors: Sharif K. J. , Kong S , Evans H. P. , Snidle R. W.
Published: October 2002

The paper presents the results of modelling the contact and elastohydrodynamic lubrication (EHL) effects between the teeth of worm gears. A number of different practical worm gear designs have been studied covering a wide range of sizes and potential applications, from small instrument drives to high power units. All the designs are of the popular ZI type, in which the worm is an involute helicoid, with deliberate mismatch of tooth conformity in order to avoid damaging edge contact. The results cover loaded tooth contact analysis (‘loaded TCA’) under dry conditions, predicted film-generating behaviour with lubrication, surface and oil film temperatures, and calculated values of friction and transmission efficiency. It is demonstrated that regions of poor film formation may be predicted in a qualitative way on the basis of loaded TCA together with consideration of the kinematics of entrainment at the contacts.
Vibration analysis of a circular disc backed by a cylindrical cavity
Authors: Gorman D G , Reese J M , Horácek J , Dedouch K
Published: October 2002

This paper describes the free vibration analysis of a thin disc vibrating and interacting with an acoustic medium contained in a cylindrical duct. The effects of structural-acoustic coupling are studied by means of an analytical-numerical method that is based upon classical theory and the Galerkin method. The coupling effects are discussed, and results obtained from the analysis are compared with corresponding values obtained both experimentally and from a finite element analysis. There is good agreement between the three sets of results.
Development of a pilot of an Arecibo-type large spherical radio telescope for the square kilometre array
Authors: Su Y X , Duan B Y , Nan R D , Peng B
Published: October 2002

An optomechatronics design project for the pilot of an Arecibo-type large spherical radio telescope for the square kilometre array (SKA) is proposed, concentrating on the feed-supporting system with large-span cables. The feed-supporting system consists of two parallel manipulators: the parallel cable manipulator, which provides a large workspace for the trajectory tracking and realizes the coarse tracking control, and the fine-tuning Stewart platform, which connects the parallel cable manipulator to the cabin structure and implements the high-accuracy requirement of tracking. In order to improve the real-time controllability, an approximate kinematics model of the parallel cable manipulator is developed using straight links to approximate the cables based on static equilibrium at low tracking velocity. A control strategy for the feed-supporting system is proposed using the independent control method, and the corresponding tracking accuracy of the coarse control and fine tuning is presented. The simulation results have supported the rationale of this approximate model of the parallel cable manipulator and the feasibility of this mechatronics design project for the SKA.
Spring damper model of an impact between a tennis ball and racket
Authors: Goodwill S R , Haake S J
Published: October 2002

A model has been derived that determines the ball, stringbed and racket frame motion for an impact between a tennis ball and racket. This paper describes the model and methods used to verify it experimentally. The model incorporated parameters such as racket mass, moment of inertia and ball stiffness. The work was conducted to produce a tool that could be used to identify the importance of each of the parameters on the impact.

The ball was modelled as simple spring and damper in parallel while the stringbed was modelled as a spring in series with the ball. The values of these spring and damper parameters were determined experimentally. It was assumed that the racket frame was a rigid body to simplify the analysis. Two different methods of supporting the racket were modelled, and the balls were always projected perpendicular to the string plane. Firstly, the racket was head-clamped and all the balls impacted at the geometric string centre of the racket. Good agreement was found between the experiment and model data for both ball rebound velocity and maximum stringbed deflection during impact. The second method of support involved freely suspending the racket at the tip on a small pin. Three different impact positions along the longitudinal axis of the racket were tested. Good agreement between the experiment and model data was found for the ball rebound velocity for impacts at the geometric string centre of the racket. The model over-predicted the experimental racket rebound velocity (generally by less than 5 per cent) for all impact positions. A qualitative analysis assigned this small difference to the assumption that the frame was a rigid body and therefore vibration losses were not accounted for.
A non-linear transfer matrix technique for statically indeterminate rotor bearing systems
Authors: Liew A , Feng N S , Hahn E J
Published: October 2002

Transfer matrix (TM) methods have long been used to obtain the vibration behaviour of linearized rotor bearing systems. Recently the technique has been enhanced to find the unbalance response of statically determinate systems with hydrodynamic bearing type non-linearities. This paper further extends the non-linear approach to statically indeterminate systems, enabling application to practical rotating machinery. The technique is illustrated on simple unbalanced rotor bearing systems with two and four bearings. It is shown that, in statically indeterminate systems, unbalance may affect not only the orbit size and shape but also the load distribution between the bearings.
Dimensional analysis revisited
Authors: Butterfield R
Published: October 2002

Dimensionless groups, the output of a successful dimensional analysis, are usually developed via Buckingham's pi theorem. Because this theorem provides a necessary but not sufficient condition for a solution, such a dimensional analysis may, on occasion, appear to fail. The paper presents the necessary and sufficient conditions in a simple form and builds on them to demonstrate how new physical knowledge can augment a ‘primitive’ set of dimensions to arrive at an optimal number of dimensionless groups. The formulation is used to elucidate the historical Rayleigh-Ria-bouchinsky controversy and a related thermomechanical problem is analysed to demonstrate the complete ‘new knowledge’ algorithm. Mathematica code is appended which incorporates these ideas and generates the complete set of admissible dimensionless groups for any specific problem.