bluuebunny/crossref_metadata_2025 huggingface dataset:
The Construction of 700 MW Units with Advanced Steam Conditions
Authors: Iwanaga K , Ohji A , Haneda H
Published: February 2007

High priority has been given to increase efficiency of power generation plants; therefore, the steam conditions of fossil fuelled plants have gradually been improved. Recent developments of material and design techniques, the accumulated experience of the operation and so on have enabled advancements to be made in steam conditions. Two units of 700 MW with advanced steam conditions were constructed at Kawagoe Power Station by Chubu Electric Power Company, Inc. in Japan. These two double reheat units are designed at elevated steam conditions of 310 bar, 5661566/566° C, to improve thermal efficiency by 5 per cent in relative values, as compared with conventional supercritical steam conditions (240 bar, 538/566° C). Considerable research and development has been carried out by the manufacturers of the boiler and the turbine to achieve highly reliable operation. This paper presents the design features, the result of the research and development and the result of the operation of these units.
On the Role of the Harmonic Mean Isentropic Exponent in the Analysis of the Closed-Cycle Gas Turbine
Authors: Woods W A
Published: February 2007

This technical note presents a development of the perfect gas analysis of the simple, closed-cycle, gas turbine reported by Hawthorne and Davis. Some comments on perfect and semi-perfect gases are included for clarification.

The new analysis takes account of the variation of specific heats of the working fluid by treating the flow through the compressor and the flow through the turbine as different perfect gases. An analytical expression is derived for the pressure ratio corresponding to maximum power. This expression is shown to be the same as that derived previously, except that the isentropic exponent has to be replaced by the harmonic mean of those used for the compressor and the turbine.

The note shows that the new method leads to significantly higher pressure ratios for the maximum power.
European Alliances
Authors: Matthews C S
Published: February 2007

The author discusses the evolution of markets which were once ‘national’ developing into ‘regional markets’ throughout Europe. He considers the importance of market leadership and outlines General Electric's decision to concentrate the company's efforts on fewer products. He stresses the need for alliances between companies in the United Kingdom and the rest of Europe if they are to survive in European markets.
Application of Transputers for Simulation of Manufacturing Systems—a Preliminary Study
Authors: Hon K K B , Ismail H S
Published: February 2007

The object of this paper is to present some preliminary results on the application of parallel processing to the simulation of manufacturing systems. The paper is focused on the basic concepts and techniques that were used in the development of a parallel simulation model written in OCCAM for a PC-based transputer system. Other technical features and characteristics of parallel processing for discrete-event-based simulations are discussed with an illustrating example.
An Expert System as a Link Between Computer Aided Design and Combined Stamping-Laser Manufacture
Authors: Raggenbass A , Reissner J
Published: February 2007

Sheet parts that have been drawn on any computer aided design (CAD) system can be manufactured on various stamping and laser-cutting machines with a prescribed set of tools. The expert system described in this paper generates from the CAD data of a part of a complete numerically controlled (NC) manufacturing plan, which contains only punching operations, only laser operations or a punching-laser combination. The main points in the fully automatic NC program generation are the recognition of the sheet part geometry, the determination of the manufacturing variant, the selection of the optimum punching tools, taking account of violation criteria, the introduction of the technology, the arrangement of many parts on a plate and the optimization of tool movement paths.
Analysis of Bi-Arm Robots for Applications in Manufacturing Industry
Authors: Buckingham R O , Brett P N , Khodabandehloo K
Published: February 2007

Within manufacturing industry many assembly and materials handling tasks are labour intensive and do not lend themselves to the application of dedicated machinery carrying out specific repetitive parts of the process. Automation of these processes will require adaptive machinery able to respond to variations in product size, orientation, mechanical properties and the position in which the task is carried out. The potential of intelligent bi-arm robot systems in these areas is discussed in relation to a number of specific bi-arm robot tasks.

The paper also discusses the design of bi-arm systems with reference to a suite of simulation programs for the analysis of workspace quality of branched, serial and closed chain robot configurations. The structure of the program enables the analysis of any robot configuration and provides the means of assessing the strategies required for robot control such as clash detection and trajectory planning.
Effects of Turning Forging Steels Which Lead to Discontinuous Cutting Conditions
Authors: Tönshoff H K , Kaestner W
Published: February 2007

An important component of the total production costs of forged parts are the costs for finish turning. During the last few years near-net - shape technology has been advanced, so that the realizable accuracy by chipless forming has been enhanced and cutting operations are necessary at connection surfaces. This can lead to discontinuous cutting processes caused by the varying depth of cut or interrupted cut. Results obtained from turning tests with continuous cutting cannot be used as a base for the machining of those forged parts. For a reduction of production costs of near-net-shape forged parts further investigations on machinability are necessary by adapted testing methods.
Surface Treatment of High-Strength Steel Plates Due to Ball-Drop Forming
Authors: Mamalis A G , Vaxevanidis N M , Karafillis A P , Xiong J Z
Published: February 2007

Experimental results pertaining to the ball-drop forming of carbon-alloyed and high-strength steel plates are reported. The authors' research is mainly focused on the correlation of the residual stresses induced and the hardness changes developed with the operational parameters that govern the ball-drop forming process. Ball-drop forming is a multiple impact process and the theories pertaining to single and/or multiple indentations are critically reviewed and compared with experimental results. It is shown that the depth of plastic zone can be determined from measurements of the indentation crater diameter dc. Residual stress fields and strained zones are related to the process parameters, that is, drop height, shot size, accumulated mass dropped and material thickness for various grades of steel strips.
On the Assessment of Equipment Reliability: Trading Data Collection Costs for Precision
Authors: Leech D J , Watkins A J
Published: February 2007

The collection of data for quantitative reliability analyses is often a costly process, particularly when field data have to be forwarded to a central point for analysis. In this short note, the authors consider one aspect of these reliability assessments, and show how data collection costs may be considerably reduced by allowing for a relatively low loss of precision in the subsequent analysis. The authors support their remarks with an example in which the two-parameter Weibull distribution is used to describe the times in service of items of equipment; however, this example illustrates principles which are more generally true, and the reader will be able to transfer the conclusions of the discussion to a wide variety of cases.
Joint Roles in Manufacturing and the Process of Change
Authors: Harrisson P W , Burns N D
Published: February 2007

In 1988 Neil Burns was appointed to a position jointly sponsored by Davy Morris Limited and Loughborough University of Technology. The appointment was unusual and pioneering in many respects, in that it required Burns to act as an Executive Director at the Company while carrying out a full academic role as Professor of Manufacturing Systems at the University. Peter Harrisson, who is Chief Executive of Davy Corporation's Mechanical Handling Division, has also been a member of the University Council since 1989. The joint role has been operating for two years and the benefits and problems have now been evaluated. The appointment has been beneficial in accelerating the process of change at Davy Morris, helping it in its progress towards its goal of achieving ‘world class’ performance in its various activities. It has also been a focus for attracting high-calibre personnel into both the Company and University. Burns, as a Davy Morris Director, has been directly involved with the short-term issues affecting the business and has been able to share these with the students. At the same time he has had access to the innovative thinking that exists within the University and has helped the Company with its development plans. The joint role has benefited from the close proximity of the two organizations, providing flexibility in timing and movement in the appointment. After two years both the Company and the University have realized greater than anticipated benefits and it is evident that the scheme is applicable for industry and institutions of higher education, not only in engineering but across a wide range of disciplines.
Analysis of Dimensional Accuracy of Precision Forged Axisymmetric Components
Authors: Sadeghi M H , Dean T A
Published: February 2007

A theoretical analysis for predicting final forging dimensions for precision forged cylinders at various forging temperatures and loads is presented. This has been derived by studying the effects of various parameters such as forging load, forging temperature, die preheat temperature and spark gap on final forged dimensions. Experimental results compare well with theoretical predictions. It has been found for circular forgings that the finish forged diameter increases with an increase in forging load, but if loading is such that it induces an axial stress greater than twice the flow stress of the workpiece material, the dimension of finished product remains constant. Dimensional variation of forgings due to elastic die deflection decreases when forging temperature increases and at high temperatures is insignificant compared to other factors. For a given die preheat temperature, the higher the forging temperature the greater the increase in forging dimension due to thermal expansion of the die. Thermal shrinkage of the forging is the overwhelming factor influencing forged dimensions at medium and high temperatures. Although friction, work hardening and heat loss were neglected, the close agreement between experimental and theoretical results shows that the theory can be usefully employed in practical situations.
Influence of Residual Stresses on Dimensional Instability of Cold-Formed Workpieces During Machining
Authors: Kocańda A Z , Wanheim T
Published: February 2007

The presence of residual stresses in a cold-formed workpiece is unavoidable due to an inhomogeneous flow of metal during the plastic deformation process. The paper deals with the problem of changes in geometry of such a workpiece after machining or heating. An extruded cup and such a cup subjected to ironing were taken into consideration. First circumferential residual stresses were determined experimentally for those cups. Next longitudinal and circumferential grooves were machined on the outer surfaces of the cups. The state of equilibrium of residual stresses was disturbed during machining and the workpieces reacted by deforming. Changes in diameter were measured by using a Zeiss three-coordinate machine and deviations in the radial direction were determined depending on the length and the number of grooves. It was concluded from the experiments that the diameter tolerances taking those changes into account should be higher than 0.4 per cent of the diameter of the extruded cup and 0.2 per cent of the diameter of the ironed cup. Stress relief annealing carried out after machining grooves increased the deviations of diameter.
Measurements of the Rheological Properties of a Kerosene Metal-Rolling Lubricant
Authors: Sutcliffe M P F
Published: February 2007

Measurements with a line-contact disc machine are used to deduce the rheological properties of a kerosene oil used in aluminium cold-rolling at the temperatures and pressures found in the bite. The deduced variation of viscosity with pressure at the higher pressures blends reasonably with previous measurements at lower pressures. The relationship between shear stress and strain rate may be described using the Eyring viscous model of fluid properties.
Interactive Robotics to Aid Physically Disabled People in Manufacturing Tasks
Authors: Gosine R G , Mahoney R M , Gatiss J , Jackson R D , Dargie G , Gibson J , Scott D , Jones T
Published: February 2007

Automation is commonly considered for application in manufacturing industry as a means of increasing productivity on repetitive assembly tasks. Attempts to automate production processes fully have been hindered by the relatively slow development of suitable technology that is cost-effective in comparison with human labour. It is known that automation is successful for high volume, rigidly structured tasks that require little decision-making. It is not so successful in the less structured tasks where human decision-making plays an important role. It is in manufacturing scenarios that rely on human decision-making that people with impaired motor function may use appropriate handling devices to carry out limited manual tasks within a more complex job activity. Demographic changes are resulting in an ageing population, a shrinking labour force and, as a result, a need for industry to consider alternative sources of labour. Most previous attempts to use robots in vocational rehabilitation have been made on an individual basis where a person possessing a desired skill becomes disabled and is able to continue in the job with robot assistance. Since many people with severe physical disability from birth have a restricted primary and secondary education, it is unlikely that there will be widespread prospects in jobs such as computer programming or accounting. This is not to say that computer-oriented jobs are not ideal for some disabled people, particularly those who have attained a high level of job qualification prior to becoming disabled. The research described in this paper, however, aims to identify generic job activities that require human decision-making ability and that have a minimum of prerequisite educational qualifications. This scenario is typical of many of the jobs within the manufacturing sector that allow the worker to acquire the necessary job skills through on-the-job training.
A General Three-Dimensional Finite Element Approach for Porous and Dense Metal-Forming Processes
Authors: Marques M J M Barata , Martins P A F
Published: February 2007

The rigid plastic finite element flow formulation based on the Doraivelu et al., constitutive equations is described. Applications to the three-dimensional compression of rectangular blocks made from dense and porous materials are presented. Modification on the ‘arc tangent’ friction model initially proposed by Chen and Kobayashi in order to take into account these constitutive equations is also discussed.

A three-dimensional finite element programme based on a generalization of the Doraivelu et al., model to include the plastic deformation of dense materials was developed. Numerical tests performed on the simulation of fully dense materials using this programme show a good agreement with the results obtained with other programmes based on the Levy-Mises constitutive equations. Theoretical predictions for the simulation of the compression of rectangular blocks made from a porous material are also presented.
Towards Improving the Properties of Plaster Moulds and Castings
Authors: Brevick J R , Davis J W , Dincher C
Published: February 2007

The plaster moulding process is commonly used for casting prototypes of aluminium components designed for subsequent production by die casting. Plaster moulded prototype castings possess dimensional tolerances and surface quality comparable to die castings, but without the high tooling costs and lead times.

Unfortunately, the mechanical properties of plaster castings are significantly inferior to their die cast counterparts. This is due primarily to the low thermal conductivity of plaster which extends casting solidification time significantly compared to die or even sand casting processes. Long solidification times result in large grained castings demonstrating low strength and hardness.

This work is an experimental investigation into the effects of various levels of silica sand and carbon fibre additions on the properties of foaming plaster moulds and associated aluminium castings. Data and statistical analyses are presented and conclusions drawn regarding the wet and dry strength of plaster moulds as a function of sand and carbon fibre content. Likewise, conclusions regarding the associated casting characteristics such as surface finish, solidification time, hardness and tensile strength are presented. The effectiveness of silica sand and carbon fibre additions with respect to improving the properties of plaster moulded prototype castings is also discussed.
A Comparison of Two-Dimensional and Three-Dimensional Hydroelasticity Theories Including the Effect of Slamming
Authors: Aksu S , Price W G , Temarel P
Published: February 2007

The behaviour of slender and non-slender flexible bodies travelling in irregular seaways is examined. This is achieved by using a two-dimensional (2D) and a three-dimensional (3D) theory. These theories are based on different assumptions and mathematical models, though both are capable of assessing the influence of transient loadings caused by slamming.

The two-dimensional theory is restricted to steady state and transient vertical responses (motion, distortion, bending moment, shear force) in irregular head waves, whereas the three-dimensional theory allows calculations of both vertical responses and transverse responses (motion, distortion, bending moment, shear force, twist) in head and oblique waves. Time-domain simulations of the responses (steady state and transient) are generated from which statistical data are determined.

For a slender uniform barge structure travelling in head seas, the response simulations and statistical data evaluated by the two theories show favourable agreement. However, for a non-slender uniform barge differences between predictions arise with the two-dimensional strip theory eventually failing, while the three-dimensional approach remains effective and its versatility is further demonstrated by predicting the slamming behaviour of a flexible barge structure travelling at arbitrary heading in an irregular seaway.
The Hysteretic Damping Model in Vibration Theory
Authors: Crandall S H
Published: February 2007

The characterization of damping elements by differential or integral equations relating physical variables by transfer functions in the frequency domain and by impulse response functions in the time domain is carried out for the ideal viscous damper, the ideal hysteretic damper and the band-limited hysteretic damper. It is shown that the latter two models are flawed because they do not satisfy the causality requirement.
On the Scattering of Waves in a Non-Uniform Euler-Bernoulli Beam
Authors: Gladwell G M L
Published: February 2007

A scattering theory for waves in non-uniform Euler-Bernoulli beams is developed and shown to be analogous to the corresponding theory for longitudinal waves in rods. Both continuous and abrupt scattering are considered, and the relevant differential equations and matrices are derived. It is shown in particular that if the beam is such that the product of its area of cross-section and its second moment of area is constant, then it is, in a certain sense, equivalent to a rod. In that case known procedures for reconstructing a rod from two spectra can be applied, with the necessary changes, to the beam.
A Link between Structural Resonance and Room Acoustics
Authors: Grootenhuis P
Published: February 2007

The amplification at resonance of a vibrating structure is dependent upon the damping which can be specified by the Q-factor. A link has been established between structural resonance and room acoustics by the derivation of an equivalent Q-factor for a standing wave in a room. The link has been obtained by equating the decay rate for free structural vibration with the rate of decay for a standing wave based on the reverberation time of the room. The analysis has been simplified by limiting the frequency range to below 500 Hz and by taking only a low to medium value for the sound absorption coefficient for the room. An example of the application of the concept of an equivalent Q-factor has been given by estimating the time required to build up a standing wave in a room compared with the duration for a train to pass.
Isolation of Buildings from Ground Vibration: A Review of Recent Progress
Authors: Newland D E , Hunt H E M
Published: February 2007

Many buildings near railways are mounted on rubber springs to isolate them from ground vibration. This paper reviews the theory of resiliently mounted buildings and discusses recent calculations of the effects of (a) different damping models and (b) piled foundations. The paper also describes site measurements in London and laboratory tests in Cambridge which are being made to support new analytical work.
Non-Linear Sensitivity Analysis of Mechanical Structures Using Modal Data
Authors: To W M , Ewins D J
Published: February 2007

This paper presents a new procedure for determining the revised modal properties (eigenvalues and mass-normalized eigenvectors) in a structural modification analysis. The procedure is based on expressing the eigenvectors of the modified structure as a linear combination of the eigenvectors of the original structure and employs the stationary property of the Rayleigh quotient to determine the modified structure's eigenvalues. It has the same theoretical basis as first- and second-order sensitivity analysis, but here the non-linear effects contributed by all high-order terms [generally assumed to be small relative to the effect contributed by first- and second-order terms (1–6)] are preserved in full. Hence, the usual shortcoming of sensitivity analysis—that it is limited to small modifications—is overcome.

A special feature of this procedure is that the exact modal properties of the modified structure are determined without solving the generalized eigenvalue problem for the modified structure. Thus, this procedure can greatly reduce the computation cost and increase the efficiency of structural modification analysis (or reanalysis) during a structural optimization process. Numerical examples demonstrate the superconvergence characteristic of the technique. The limitations caused by modal and coordinate incompleteness, and the sensitivity of this technique with respect to simulated measurement errors, are investigated by using a finite element model of a steel frame structure and a ten-degrees-of-freedom mass-spring model.
Robust Observer-Based Control of a Vibrating Beam
Authors: Chen B-S , Lin C-L , Hsiao F-B
Published: February 2007

A new multiple-input multiple-output time domain stability criterion for large flexible structures is illustrated by application to observer-based control of a Bernoulli-Euler beam. Upper norm bounds of the state transition matrix of the residual dynamics and total spillover matrix (impulse response matrix of the residual model) are investigated. The approach can be easily extended to a practical consideration of the unavoidable saturation of the actuators and gives an insight into the stabilization analysis of saturating control of flexible structures.
Elastohydrodynamic Lubrication of Big-End Bearings Part 1: Theory
Authors: Aitken M B , McCallion H
Published: February 2007

Lubrication of a dynamically loaded big-end bearing is re-examined under elastohydrodynamic assumptions. All current models are found to be in some way deficient; reference frame anomalies and erroneous connecting-rod kinetics proliferate.

Part 1 of this work presents a consistent schema correcting deficiencies identified in previous big-end studies. Newton-Raphson and continuation techniques are developed for the solution of a Galerkin system formulation. This formulation additionally features a simple ‘vapour’ cavitation model.

Part 2 presents verifications of the developed theory: comparisons with previous theoretical works along with an overdue comparison with previously published experimental results.
A Hybrid Method for the Vibration Analysis of Rotor-Bearing Systems
Authors: Firoozian R , Zhu H
Published: February 2007

The transfer matrix method together with a digital computer form the foundation of the dynamic analysis of rotor-bearing systems. The properties of each segment of the rotating shaft are expressed in simple matrix form and the overall dynamic behaviour is then obtained by successive multiplication of the element matrices. The main drawback associated with this method is the numerical instability in calculating natural frequencies for complex systems.

The finite element method, on the other hand, uses the element stiffness and mass matrices to form the global equation of motion for the complete system. This avoids the numerical problems of the transfer matrix method at the expense of the computer memory requirements.

The new method described in this paper combines the transfer matrix and finite element techniques to form a powerful algorithm for vibration analysis of rotor-bearing systems. It is shown that the accuracy improves significantly when the transfer matrix for each shaft segment is obtained from finite element techniques.

The accuracy and efficiency of the hybrid method are compared with the transfer matrix method for a simply supported uniform rotating shaft where an analytical solution for the critical speeds and mode shapes is available. The method is then applied to a flexibly supported uniform shaft and a non-uniform shaft with a large disc to show the capability of the method for finding the critical speeds of complex rotor-bearing systems.
Optimum Sampling Interval for Ra Roughness Measurement
Authors: Yim D Y , Kim S W
Published: February 2007

This paper describes the statistical treatment of determining the sampling interval for the digital Ra roughness measurement. It is proved that the optimum sampling interval can be determined from the Rq/Ra ratio of the surface to be measured and the evaluation length. A nomograph is suggested for practical uses on the workshop floor.
Elastohydrodynamic Lubrication of Elliptical Contacts with Spin and Rolling
Authors: Dowson D , Taylor C M , Xu H
Published: February 2007

Studies of elastohydrodynamic lubrication of point contacts have been undertaken since the early 1970s. Nearly all the investigations reported have been concerned with surface motions of rolling and/or sliding and little work has been reported on the common engineering problem of elastohydrodynamic lubrication with spin and rolling. This kinematic condition is found in angular contact bearings and variable-speed traction drive systems.

The theoretical investigation described in this paper is therefore concerned with the elastohydrodynamic lubrication of non-conformal point contacts with both rolling/sliding (potentially) and spin. The study provides an indication of the importance of the superimposed spinning motion upon the rolling and sliding motions in the lubricated conjunctions. The results presented cover not only typical ratios of spin/rolling velocities but much higher values not encountered in the machine elements mentioned.
Buckling Design of Imperfect Welded Hemispherical Shells Subjected to External Pressure
Authors: Galletly G D , Blachut J
Published: February 2007

Welded hemispherical or spherical shells in practice have initial geometric imperfections in them that are random in nature. These imperfections determine the buckling resistance of a shell to external pressure but their magnitudes will not be known until after the shell has been built. If suitable simplified, but realistic, imperfection shapes can be found, then a reasonably accurate theoretical prediction of a spherical shell's buckling/collapse pressure should be possible at the design stage.

The main aim of the present paper is to show that the test results obtained at the David Taylor Model Basin (DTMB) on 28 welded hemispherical shells (having diameters of 0.75 and 1.68 m) can be predicted quite well using such simplified shape imperfections. This was done in two ways. In the first, equations for determining the theoretical collapse pressures of externally pressurized imperfect spherical shells were utilized. The only imperfection parameter used in these equations is δ0, the amplitude of the inward radial deviation of the pole of the shell. Two values for δ0 were studied but the best overall agreement between test and theory was found using δ0 = 0.05 ✓ (Rt). This produced ratios of experimental to numerical collapse pressures in the range 0.98–1.30 (in most cases the test result was the higher).

The second approach also used simplified imperfection shapes, but in conjunction with the shell buckling program BOSOR 5. The arc length of the imperfection was taken as simp = k ✓ (Rt) (with k = 3.0 or 3.5) and its amplitude as δ0 = 0.05√(Rt). Using this procedure on the 28 DTMB shells gave satisfactory agreement between the experimental and the computer predictions (in the range 0.92–1.20). These results are very encouraging. The foregoing method is, however, only a first step in the computerized buckling design of welded spherical shells and it needs to be checked against spherical shells having other values of R/t. In addition, more experimental information on the initial geometric imperfections in welded spherical shells (and how they vary with R/t) is desirable.

A comparison is also given in the paper of the collapse pressures of spherical shells, as obtained from codes, with those predicted by computer analyses when the maximum shape deviations allowed by the codes are employed in the computer programs. The computed collapse pressures are frequently higher than the values given by the buckling strength curves in the codes. On the other hand, some amplitudes of imperfections studied in the paper give acceptable results. It would be helpful to designers if agreement could be reached on an imperfection shape (amplitude and arc length) that was generally acceptable.

Residual stresses are not considered in this paper. They might be expected to decrease a spherical shell's buckling resistance to external pressure. However, experimentally, this does not always happen.
Computer Simulation of the King's Cross Fire: Effect of Radiative Heat Transfer on Fire Spread
Authors: Malalasekera W M G , Lockwood F
Published: February 2007

A mathematical model has been applied to simulate model experiments of the 1987 King's Cross underground fire by the Department of Health and Safety Executive. The predicted growth of the fire is compared with the experimental data and in particular the predicted and measured times to ‘flashover’ are compared. The comparisons show exceptional agreement which, in part, may be fortuitous due to the need to facilitate the prediction of the early stages of the growth with the aid of an experimentally estimated fire strength. The good agreement nonetheless is also due to the full description of the radiation transfer which is a feature of the mathematical model. It is concluded that the flashover phenomenon that occurred at King's Cross was thermal radiation driven and that future research should be devoted to modelling the details of fire spread across a combustible surface.
Analysis of Failure Modes of a Thermoplastic One-Way Clutch
Authors: Burgess S C , Stolarski T A , Karp S
Published: February 2007

This paper presents an analysis of the failure modes during power transmission of a new type of one-way clutch called an expansible-band clutch. The new clutch is made from thermoplastic materials and an experimental test rig has been used to test two material combinations to failure. The experimental results are compared with predictions obtained from empirical formulae. The differences in the two sets of results are used to make conclusions about the failure processes.
Traction Measurements in Mixed Elastohydrodynamic Lubrication with a Controlled Circumferential Roughness
Authors: Sutcliffe M P F
Published: February 2007

The transition between smooth elastohydrodynamics (EHL) and micro-EHL is investigated. Traction measurements in a disc machine with a controlled circumferential roughness are used to infer film thicknesses under the asperity tops. These are then compared with hydrodynamic theory. At the two extremes where there is little pressure rippling between the asperity tops and the adjoining valleys or where there is little pressure in the valleys the theoretical and experimentally inferred films are in reasonable agreement. In the transition region the experimentally deduced films are not reliable. Traction behaviour is estimated in the transition region by making some simple assumptions. The film thickness under the asperities is taken as that given by theory for no pressure in the valleys, and the valley pressure in the transition region is estimated by assuming a simple variation with speed. Theoretical traction curves are calculated by apportioning the load between the valleys and the asperity tops and agree well with measured curves, suggesting that this is a good picture of the contact. The traction behaviour was found to depend on sliding speed in a way typical of hydrodynamic lubrication even for estimated oil films as small as 8 nm.
Signature Analysis for Reciprocating Machinery with Adaptive Signal Processing
Authors: Zhuge Q , Lu Y
Published: February 2007

The spectrum analysis by means of FFT (fast Fourier transform) analysis has been widely used in mechanical signature analysis. An alternative method is proposed in the paper for condition monitoring and diagnostics of reciprocating machines. A modified LMS (least mean square) algorithm is proposed in order to model the impulse-like signals with non-stationarity. Convergence of the algorithm is investigated. The approach presented is suitable to real-time monitoring during the process of working operation and fault diagnostics of reciprocating machines.
Towards Optimum Carbon-Fibre-Reinforced Plastic End Closures
Authors: Błachut J , Galletly G D , Levy-Neto F
Published: February 2007

Two series of external pressure tests on six-layer CFRP (carbon-fibre-reinforced plastic) torispherical domes are discussed in the paper. One series had a diameter-average thickness ratio of 80 and the other 120. The ratio Rs/D was the same for all the models and equalled 0.55 (Rs = spherical radius of a dome). The ratio r/D (r = toroidal or knuckle radius) varied from 0.2 to 0.5, the latter being a hemisphere. All the models were made by the hand lay-up/vacuum bag technique using male moulds.

The failure modes considered were bifurcation buckling and first-ply failure (FPF). The BOSOR 4 program was used to evaluate the theoretical stresses in the shells and various failure criteria (Owen, Tsai-Wu etc.) were employed to determine the FPF pressures. In the tests, all the models failed by material failure rather than shell buckling and the ratios of the experimental collapse pressures to the FPF predictions were in the range 0.85–1.30.

The tests also confirm a recent theoretical prediction that there is an optimum value of the r/D ratio insofar as dome strength is concerned. These CFRP torispherical domes are lighter and stronger than the comparable CFRP hemispheres.

The BOSOR 4 predictions of FPF pressures and failure locations were confirmed by the NISA finite element code. The calculations also showed that it is necessary to use finite deflection shell theory when analysing these composite domes.
Piston-Liner Thermal Resistance Model for Diesel Engine Simulation: Part 2: Application to various Insulation Schemes
Authors: Rasihhan Y , Wallace F J
Published: February 2007

The piston-liner thermal resistance model, developed in Part 1, is applied to various piston and/or liner insulation schemes. The effects of insulation on piston-liner conduction and gas to wall heat fluxes and liner temperature distribution are examined. The small effect of insulation of the middle and lower parts of the liner is clearly shown.
Boundary Singularities in Steady Potential Compressible Flow Through Plane Two-Dimensional Channels
Authors: Streeter C A C
Published: February 2007

Boundary singularity solutions are reviewed, which relate to the steady, transonic potential flow of a perfect gas, through plane, two-dimensional convergent channels. Two singularities occur in the physical plane, one at upstream infinity and the other at the concave corner in channels that have a parallel entry section followed by a convergent section that ends at the throat plane. Solutions of these singularities are obtained from the general solution of Chaplygin's stream function equation in the hodograph system of coordinates. Uniform, uni-directional subsonic entry flow, in a finite-length channel, gives rise to a boundary singularity in the hodograph plane. The stream function is multi-valued at this singularity, where it varies between one and zero, while the flow direction is zero. This condition is removed by introducing circular polar coordinates (r, α) with origin at the singular point. For a sufficiently small value of r, a second-order partial differential equation of the stream function is obtained in the new coordinates. A particular solution of this equation is given, when r is small, rs say, in which the stream function gradient in the radial direction is taken as zero for all values of α at rs. The full series solution of the new equation is given in a paper which is to follow. Finally, consideration is given to the problem of matching the subsonic and supersonic flow regions at the sonic surface. A new system of equations is given, which determine the stream function gradient at sonic points from values of the stream function in the expansion region. Computed results are given that relate to the steady, choked flow of a perfect gas through a 15° convergent channel. The overall solution is shown to converge.
Computer-Based Algorithm for Instantaneous Centres of Planar Mechanisms
Authors: Lee K-W , Yoon Y-S
Published: February 2007

A computer-based algorithm to enumerate the locations of instantaneous centres of planar mechanisms is developed. There exists a matrix method of obtaining instantaneous centres of planar mechanisms implementing Kennedy's theorem into a matrix form, but it has such limitations that many classes of planar mechanisms cannot be handled properly. The algorithm proposed here is basically an extension of the matrix method to handle any kind of planar mechanism. Several classes of planar mechanism are studied by these two methods to demonstrate the differences between them.
Internal Flow Modelling of Vortex Throttles
Authors: Yang Z Y , Priestman G H , Boysan H F
Published: February 2007

A finite difference computer code has been used to predict highly swirling confined incompressible turbulent flow in vortex throttles. As turbulence can become highly anistropic in such flow cases, both the widely used two-equation k-ɛ model and a Reynolds stress model have been used. The results have been compared with basic experimental data and the predicted flow structure within the throttles is related to the main design parameters. It has been found that the pressure drop across the vortex throttles occurs mainly through the axial port by dissipation of the high tangential velocity. Energy loss in the vortex chamber tends to reduce the vortex strength, lowering the tangential velocity and consequently reducing the pressure drop.
An Analytical Evaluation Method for Lubrication Oil Consumption
Authors: Miyachika M
Published: February 2007

A study of engine oil consumption (OC) was conducted both theoretically and experimentally. It was found that oil blowing into the combustion chamber through the top ring gap (termed ‘reversed oil’) and oil returning to the crankcase through the oil ring gap (termed ‘blowby oil’) are important factors affecting OC. It was also observed that depending on the ring gap clearance, enlarged because of ring wear (for example the radial ring wear of 50 μ corresponds to a gap enlargement of roughly 0.31 mm) or non-optimal ring gap clearance and inter-ring volume, the 2nd land pressure can exceed cylinder pressure—leading to increasing reversed oil and consequently higher OC. The deterioration of OC with increasing operation has been traced to lowered oil-scraping capability with ring wear. This is true. However, the above-mentioned phenomenon can be considered as another reason for such OC. This paper describes the relationship between reversed oil/blowby oil ratio and OC, and presents a procedure for optimizing ring gap clearance and interring volume for acceptable OC. This study, however, neglected oil supplied to the ring pack via the valve set.
Simulation of Side Impact on Cars
Authors: Langdon M G
Published: February 2007

Simulation models of side impact are used to improve understanding of the dynamic events which can only partially be observed and measured in full-scale impact tests, and to explore the effects of modifying structural design without the expense of building and impacting large numbers of experimental vehicles. It has also been suggested that they could be used for legislative testing.

Simulation models for frontal impact into a rigid block were first developed about fifteen years ago. Subsequently side impact models were developed along similar lines, to represent impact by a rigid impactor, in accord with the then current methods of full-scale testing. The car structure was represented by a small number of discrete masses, connected by (non-linear) springs and dampers. The dummy occupant was initially represented by a single rigid mass. When a deformable barrier front was first used to replace the rigid barrier, this was merely represented by an additional spring in the model, and an attempt was made to introduce a more representative model of the dummy thorax. Comparison with full-scale test results has shown that this was an oversimplification and that relative motion between different parts of the car structure, and between different parts of the dummy, is an important factor in determining the likely level of injury. Currently work is proceeding on developing more realistic lumped parameter models which can reproduce these effects and which can take some account of the effect of dynamic impact (compared with quasi-static loading) on the spring elements.

In many ways the ideal solution would be to use a dynamic finite element model, but these are complicated to set up and very expensive in computer running time. An exciting possibility for the future is the development of hybrid models, in which critical elements can be modelled by finite elements, but in which the bulk of the model still consists of lumped parameter elements.
Drum Brake Interface Pressure Distributions
Authors: Day A J
Published: February 2007

A review of recent research work predicting contact and pressure distributions at the friction interface of drum brakes is presented. Previously published results are summarized and used, together with new results, to illustrate the effects of friction coefficient, lining compressibility and brake shoe stiffness, actuation force, lining/drum conformity, and wear, on brake performance. The results are discussed in the context of geometry and bulk deformation effects, and of macroscopic interface pressure distribution effects, and confirm the importance of interface pressure distribution in the performance and continued operation of drum brakes to required design levels.
Disc Brake Interface Pressure Distributions
Authors: Tirovic M , Day A J
Published: February 2007

The nature of the contact and pressure at the interface between the friction material pad and the disc rotor of a ‘spot’-type disc brake affects the performance of a brake in terms of torque, temperature distributions and wear. Interface contact and pressure distributions have been predicted for a particular design of floating caliper passenger car disc brake, using three-dimensional finite element analysis under static and dynamic brake actuation conditions.

The influence of friction material compressibility, pad backplate thickness, coefficient of friction, caliper flexure, disc stiffness and actuating piston contact with the piston bore on the interface pressure distribution is examined. The effect upon brake performance is discussed in terms of ‘centre of pressure’ and corresponding braking torque, and in terms of observed effects such as temperature and wear distribution. The results confirm that in order to ensure consistent disc brake performance the interface pressure distribution should be carefully controlled by designing in mechanical rigidity, compliant friction materials and minimum compliance during brake operation.
Developing the Truck Engine for Ultra Low Emissions
Authors: Needham J R , Faulkner S A , Doyle D M
Published: February 2007

Environmental concerns dictate that the heavy duty automotive diesel engine will have to comply with increasingly more stringent exhaust emission standards. Nowhere are these standards more stringent than the 1991–94 USA requirements. Meeting these standards in production and during the engine's useful life, while maintaining or improving engine performance and fuel economy, is an extremely demanding technical challenge. This paper describes the technology that will be utilized on heavy duty diesel engines to meet the US 1994 standard and examines how the fleet operator may be affected.
Frequency Analysis of Tumble and Swirl in Motored Engines
Authors: Arcoumanis C , Enotiadis A C , Whitelaw J H
Published: February 2007

Frequency analysis of the turbulent velocity fluctuations was performed in an engine motored at 1000 r/min and equipped with a directed port generating tumbling flow and a helical port generating swirl. The results show that the turbulent energy generated by the breakdown of the tumbling vortex in the directed port case, although confined to frequencies below 289 Hz, is overall higher compared to that of the helical port which suggests that flame propagation in the initial stages of combustion will be faster in the tumbling flow case.
Standardization of Intelligent Vehicles and Highways
Authors: Kayton M
Published: February 2007

This paper suggests that intelligent vehicle-highway systems (IVHS) will evolve differently in North America, Europe and Japan. Over-highway systems should be standardized on a continent-wide basis while city systems will adapt to local needs. The paper proposes an open-system architecture for the electronics within the vehicles themselves. Those societies who best conserve their citizens' time will compete best in world markets.
On the Synthesis of Constraint Systems for Stable Workholding
Authors: Pham D T , Tacgin E
Published: February 2007

During a robotic materials handling operation, the position and orientation of the workpiece must remain fixed with respect to the coordinate frame of the gripper when the robot arm moves from one point to another. This is achieved if all degrees of freedom of the workpiece relative to the gripper are eliminated by placing appropriate constraints on its movements. Deciding how to constrain an object forms an important part of the design of gripping devices. In this paper, the rules for analysing the state of constraint of an object are reviewed. This is followed by a discussion of a procedure for synthesizing stable constraint configurations for a wide variety of object shapes. Finally, examples are provided to illustrate the application of the proposed procedure in the case of two simple objects.