bluuebunny/crossref_metadata_2025 huggingface dataset:
Generic functions for fuel consumption and engine-out emissions of HC, CO and NOx of spark-ignition engines
Authors: Shayler P. J. , Chick J , Darnton N. J. , Eade D
Published: October 2002

The prediction of fuel consumption and engine-out emissions of spark-ignition engines from characteristic relationships has been investigated. For spark-ignition engines operating on homogeneous mixtures, indicated specific fuel consumption based on gross indicated power is related to compression ratio and spark timing relative to optimum values. The influence of burn rate is largely accounted for by differences in spark timings required to phase combustion correctly. For engine-out emissions of HC, CO and NO x, generic functions have been derived that relate the emissions index in each case to air-fuel ratio, spark timing relative to the optimum and burned gas fraction present during compression. The effects of exhaust gas recirculation and residual gas dilution are accounted for. Brake specific performance maps can be generated. This requires knowledge or predictions of calibrations, cylinder volumetric efficiency, rubbing friction, auxiliary loads and exhaust back pressure. A closed set of equations and illustrative results are given.
Fibre-reinforced composites in the car side structure
Authors: Patberg L , Philipps M , Dittmann R
Published: October 2002

In this paper the general requirements for a passenger car side door made of fibrereinforced plastic (FRP) are presented as well as a description of different concepts for self-supporting monocoque FRP doors. For one conceptual design, static and dynamic analyses have been made to investigate the potential of composites in this application. The results of the structural analyses, which have been investigated by commercial finite element analysis (FEA) codes, are presented. The research data resulting from completed testing of components are compared with the simulation results. On the basis of this research the prospect for the application of FRP in the field of side impact protection is discussed.
Vehicle speed calculation from pedestrian throw distance
Authors: Evans A. K. , Smith R
Published: October 2002

When a pedestrian is thrown through the air by the impact of a motor vehicle, the distance travelled by the pedestrian from the point of impact can be used to provide an estimate of the speed at which the vehicle was travelling. Three sets of data collected from real accidents are reviewed with the aims of assessing the value of this method and fixing the model used to estimate the speed. The data have been published by Stürtz and Suren [1], by Hill [2] and by Dettinger [3]. Each provides the vehicle speed estimated from skid marks and the pedestrian throw distance for a number of real traffic accidents. The parameters in a simple, physically motivated model are fitted to each dataset separately using a least squares method. It is found that the earlier dataset has a much less consistent relationship between throw distance and vehicle speed than the later sets. The two more recent sets of data are used to construct a model that provides an estimate of the vehicle speed based on the throw distance, the bounds within which, with 95 per cent certainty, the vehicle speed lies, and an absolute lower bound. The data are also used to assess a method considered by Wood for the estimation of vehicle speed from the distance between the final resting place of vehicle and pedestrian. It is concluded that this last method is not likely to be useful because of its sensitivity to errors in measurement.
Method procedures for sampling aldehyde and ketone using 2,4-dinitrophenylhydrazine—a review
Authors: Yacoub Y
Published: October 2002

Methods for sampling aldehyde and ketone using 2,4-dinitrophenylhydrazine (DNPH) are reviewed with emphasis on the type of trapping media, the absorbing solution composition and stability and the sample flowrate. Pre- and post-sampling procedures are discussed as well as collected sample stability, detection range, contamination and interference. Different methods for generating standard atmospheres are discussed as well as collection efficiency and standards recovery. Aldehyde emissions measured using DNPH in engine exhaust are briefly reviewed with an overview of the effects of fuel type, engine concept and operation and exhaust gas aftertreatment. Finally, practices and recommendations are proposed to ensure the integrity of the sampling process and appropriateness to different applications.
Computer aided engineering in diesel exhaust aftertreatment systems design
Authors: Stamatelos A. M. , Koltsakis G. C. , Kandylas I. P. , Pontikakis G. N.
Published: October 2002

Computer aided engineering (CAE) methodologies are increasingly being applied to assist the design of spark-ignition (SI) engine exhaust aftertreatment systems in view of the stage III and IV emissions standards. Following this trend, the design of diesel exhaust aftertreatment systems is receiving more attention owing to the capabilities of recently developed mathematical models. The design of diesel exhaust systems must cope with three major aftertreatment categories: diesel oxidation catalysts, diesel particulate filters and de-NOx catalytic converters. An integrated CAE methodology that could assist the design of all these classes of systems is described in this paper. It employs the following computational tools: a computer code for modelling transient exhaust system heat transfer, a computer code for modelling the transient operation of a diesel oxidation or a de-NOx catalytic converter, a database containing chemical kinetics data for a variety of oxidation and de-NOx catalyst formulations and a computer code for modelling the loading and regeneration behaviour of a wall-flow filter, assisted by catalytic fuel additives. Application of the CAE methodology, which helps the exhaust aftertreatment system design engineer to meet the future emissions standards, is highlighted by referring to a number of representative case studies.
Barrel swirl breakdown in spark-ignition engines: Insights from particle image velocimetry measurements
Authors: Reeves M , Haste M. J. , Garner C. P. , Halliwell N. A.
Published: October 2002

Particle image velocimetry (PIV) has been used here to study the formation and breakdown of barrel swirl (‘tumble’) in a production geometry, four-stroke, four-valve, motored, spark-ignition, optically accessed internal combustion (IC) engine. The barrel swirl ratio (BSR) of the cylinder head could be enhanced by means of a port face inducer gasket so that the flow processes taking place at low and high swirl ratios could be investigated conveniently. Double-exposed images from planes both parallel and perpendicular to the cylinder axis were recorded at selected crank angles through the induction and compression strokes at a motored engine speed of 1000 r/min, with a wide open throttle, for both high and low BSR cases. The recorded images were interrogated by digital autocorrelation to give two-dimensional maps of instantaneous velocity.

In both high and low BSR cases, a barrel or tumbling vortex motion is generated during induction, which is shown to persist throughout the majority of the compression stroke. The details of barrel swirl formation during induction and its subsequent modification during compression, however, differ strongly between the two cases. These differences can be explained qualitatively in terms of two main events; the first being competition during induction between vortices of unequal strength and the second being competition between the large-scale swirl motion and the local flow field generated by piston motion during compression. In the low barrel swirl case, significant dissipation occurs owing to these interactions and consequently the large-scale motion exhibits lower mean velocities and undergoes significant distortion. In the case of high BSR, the competition effects are minimized and a single ordered vertical vortex exhibiting high velocity magnitudes is observed to avoid piston induced distortion. It then moves into the apex of the pent roof combustion chamber where it survives as a single ordered vortex until at least 40° crank angle (CA) before top dead centre (TDC). Limitations and developments of the PIV technique are discussed.
Analysis of stratified EGR and air on combustion and NO formation in a spark-ignition engine
Authors: Zhao H , Peng Z , Calnan P , Ladommatos N , Ma T
Published: October 2002

Using a phenomenological model (Brunel Engine Emissions, Performance and Autoignition Simulation, BEEPAS) developed at Brunel University, the influence of stratified exhaust gas recycled (EGR) and stratified air (lean burn) on spark-ignition (SI) engine performance and NO emission were analysed. The mixture in the cylinder was divided spherically into three parts: a central core with a stoichiometric air—fuel charge, a dilution region without any combustible charge and a mixing region lying between the core and the dilution region. Three mixture stratification parameters were investigated: the amount of mixing in the cylinder, the extent of dilution in the mixing region and the gradient of stratification in the mixing region. In addition, the difference in the effects on combustion and NO formation of stratified EGR and air was analysed.

The results indicate that stratified air operation is better for improving engine efficiency than stratified EGR operation. It was found that the longer combustion duration, as well as the increased heat capacity of EGR, contributes to the superiority of stratified EGR over stratified air in the suppression of in-cylinder NO formation. For the same initial charge temperature, stratified EGR has a much lower dilution limit than stratified air owing to retardation of flame propagation. As long as the degree of dilution in the mixing region is within the dilution limit of the combustible charge, the gradient of dilution has little effect on combustion and NO formation.
Pneumatic conveying of abrasive bulk solids at Anglesey Aluminium Metals Limited: Four case studies
Authors: Burne C , Bradley M S A
Published: October 2002

This paper explains and compares four different technologies used for piped pneumatic transportation of bulk materials within the aluminium smelter at Holyhead, North Wales, and gives guidance for the selection of future systems. The differences in system design and operation are surveyed, the relative advantages and disadvantages identified in practical operation are discussed, and the energy consumptions of the different systems are compared. In addition, comparisons are made to the alternatives, i.e. mechanical conveying systems. Finally, conclusions are drawn as to what lessons may be learned in regard to choosing, operating and maintaining a system for the conveying of abrasive materials.
Systems integration in maintenance engineering
Authors: Starr A , Ball A
Published: October 2002

Integration in maintenance engineering systems provides a potential solution to some complex and conflicting problems. Decision making is often achieved with uncertainty and unknowns, while measuring against conflicting performance criteria. Maintenance decisions are made in the context of business priorities.

Integration must consider the bidirectional flow of data and information into the decision-making and planning process at all levels. This reaches from business systems right down to sensor level. Integration automates the organization and operation of systems, data collection and actuation, information storage and decision making. Critically, integrated systems display the evidence of thorough top-down system design, which incorporates the elements above and closes the loop from the minutiae of data collection to strategic decision making.

This paper introduces the systems associated with maintenance and draws comparisons with adjacent disciplines such as control. A globalized model is proposed, and methods for selecting and adapting technologies for the model are discussed. Examples of industrial implementation are shown at several levels within the model.
Condition-based maintenance: A systematic method for counting the cost and assessing the benefits
Authors: Rajan B S , Roylance B J
Published: October 2002

A mathematical model has been developed in order to predict the cost of repairs for batch process plant machinery in the pharmaceutical industry and thereby to determine the associated cost benefits of practising a condition-based maintenance programme. The implications of consequential costs arising from the operation of fans are compared with pumps which have stand-by facilities. The situation with gearboxes where oil condition monitoring decreases the failure rate is also examined.
Incorporation of modern on-line spectral condition monitoring for operational availability improvement of reactor coolant pumps
Authors: Kang C W , Golay M W
Published: October 2002

At the design stage, the work reported here recommends provision of the possibility of employing modern on-line spectral condition-monitoring equipment in order to improve the operational availability of nuclear power plant equipment, the reactor coolant pump (RCP).

Following an analysis of the leading causes in the RCP forced outages, incorporation of the use of advanced on-line spectral condition-monitoring sensors and their corresponding data-processing equipment in new power plant designs is sought. They are employed in order to detect the incipient symptoms generated during the progression of potential system faults of major concern. Firstly, the applicability of recent developments in new sensors and data-processing techniques is examined. This examination concerns system status parameter monitoring in the analysis of vibration, motor current, partial discharge and wear debris. Finally, use of modern sensors and data-processing equipment, which are valuable for the intended condition-monitoring systems, is recommended. Furthermore, valuable information on the future trend of currently developing sensors at the research stage is briefly presented.

This state-of-the-art review lays a foundation for developing modern comprehensive sensor networks to support efficient condition monitoring in other power plant rotating machines.
Nozzles in the knuckle region of a torispherical head: Stress levels and load interaction effects
Authors: Hsieh M F , Moffat D G , Mistry J
Published: October 2002

The results of a limited parametric study on the stress levels in knuckle encroaching nozzles in a Klöpperböden torispherical head due to pressure and nozzle loads are presented. The results give support to the CEN TC 54 procedure which requires thickening of the knuckle region for such nozzles for pressure loading. Stress levels due to nozzle loads are shown to be of the same order of magnitude as those in the equivalent axisymmetric nozzle. Studies of interaction diagrams have confirmed the CEN TC 54 proposal for combined loading in axisymmetric nozzles but have shown that a linear interaction rule should be recommended for non-axisymmetric nozzles in heads.
Effects of the properties of bulk solids on the relative performance of polyethylene and stainless steel wall lining materials in mass flow hoppers and other applications
Authors: Bradley M S A , Bingley M , Farnish R J , Pittman A N , Lee G
Published: October 2002

Reducing the friction between the walls of storage vessels and the bulk solids that they contain is widely known to be beneficial in obtaining more satisfactory flow patterns in such vessels, and to reduce flow problems. In particular, the advantages of low friction in promoting a mass flow discharge pattern are well understood; means of obtaining data to design a hopper for mass flow are also well established.

In recent years a number of polyethylene materials have come on to the market, intended for use in lining silos and claimed by their manufacturers to offer low wall friction in comparison with other materials. In this paper, one particular commercial grade of ultra-high molecular weight polyethylene (UHMWPE) material has been tested alongside a commonly used type and finish of ferritic stainless steel. The wall friction has been measured for both materials, with a variety of bulk solid materials and conditions, and the hopper half-angles needed for mass flow computed for each combination.

The results show that the UHMWPE material does not always offer a lower friction than the stainless steel; in some cases it offers much lower friction and hence much greater scope for obtaining mass flow discharge. However, in other cases it gives significantly higher friction and is a bad choice for promoting flow.

The principal conclusion is that, under certain circumstances, UHMWPE offers substantial advantages over other wall materials. However, this advantage is by no means universal and, if it is to be considered for employment in a hopper design, then a wall friction test should be undertaken. This test should use a sample of the bulk solid to be handled against both the UHMWPE material and other possible materials.
A computational fluid dynamics study on the effect of sterilization temperatures on bacteria deactivation and vitamin destruction
Authors: Ghani A G Abdul , Farid M M , Chen X D , Richards P
Published: October 2002

The optimization of thermal processes such as sterilization relies on the accuracy of relevant kinetic data for bacterial inactivation and quality evolution. It is also dependent on the geometry and heating mechanism involved in the process. In these processes or systems, profiles of temperature distribution, bacteria concentration and concentrations of vitamins C (ascorbic acid), B1 (thiamin) and B2 (riboflavin) in a can filled with cherry juice during thermal sterilization have been obtained through numerical simulations. Different heating medium temperatures of 121, 130 and 140°C were tested. In order to generate these profiles, the continuity, momentum and energy equations are solved numerically, together with those of bacteria and vitamins concentrations, using the computational fluid dynamics code PHOENICS, combined with reaction kinetics models. Natural convection that occurs during thermal sterilization of viscous liquid (concentrated cherry juice, 74 °Brix) in a cylindrical can heated from all sides has been studied in this work. The simulations show clearly the dependences of the concentration of live bacteria and different vitamins on both the temperature distribution and the flow pattern as sterilization proceeds. The results also show that the best sterilization temperature may not always be 121 °C, depending on the quality requirements imposed on individual food material of concern.
Cutting force, tool wear and surface finish in drilling metal matrix composites
Authors: Davim J P , Monteiro Baptista A
Published: October 2002

In this paper the evolution of the cutting force, tool wear and surface finish, measured when drilling the metal matrix composite A356/20/SiCp-T6, is presented. The experimental work was developed through the continuous measurement of the torque with an appropriate piezoelectric dynamometer and the results were used to derive the cutting power (ranging from 0.1 to 0.4 kW) and the specific cutting pressure, K s (1700-3500 N/mm2). The tool wear type was identified and its evolution with cutting time was measured for different sets of cutting conditions, using polycrystalline diamond drills. The holes' surface finish was evaluated and very good results, exceeding standard values for drilling, were obtained ( R a between 0.25 and 1.2 μm).
Stresses from radial loads and external moments in spherical pressure vessels
Authors: Rilo N F , da Silva Gomes J F , Cirne J M O S , da Costa Pereira Leal R A
Published: October 2002

In this paper analytical solutions for displacements and stresses in spherical shells over rectangular areas are developed. The analysis is based on spherical shallow shell equations, and solutions are obtained through the use of double Fourier series expressions to represent the displacement and loading terms. Three types of loading were considered: radial load, overturning moment and tangential shear. In order to test the results, an experiment and finite element investigation has been carried out to determine the state of stress in a spherical shell model and results are compared in graphs. The proposed solution is also applied to compute the local stresses around a support leg in a spherical shell, and results are compared with those obtained by the Bijlaard method used in American code ASME VIII, Part 2, and British code PD 5500: 2000.
Self-discharging flat-bottom centrifugal basket design
Authors: Gogate S A
Published: October 2002

The final stage of sugar production is the separation and drying of grown sugar crystals from the viscous slurry called massecuite. Massecuite is poured into a spinning basket and washed. The centrifugal force purges the wash from the meshed basket wall. Sugar crystals left behind in the basket are spin dried. Dried sugar crystals are either scraped or self discharged from the basket. A basket with an external scraper, a flat-bottom basket, has a typical process cycle of 180 s inclusive of 40 s scraping time. A self-discharging (taper-end) basket has a typical process cycle of 150s inclusive of 8 s discharge time. However, the material-handling capacity of the self-discharging basket is poorer, and the processed sugar quality is inferior as it has traces of molasses and therefore has a yellow tinge. Acceleration of the centrifugal basket requires a very large amount of energy because of its innately high moment of inertia. A ‘self-discharging flat-bottom centrifugal basket’ design is proposed. This basket would have material-handling capacity similar to that of a flat-bottom basket and it would deliver sugar of similar quality. It has no external scraper and sugar discharge time would be 8–10 s. It has a lower moment of inertia and would save more than 15 per cent energy on the inertial basket load.
Mathematical modelling for synthesis of spatial gears
Authors: Abadjiev V I
Published: October 2002

Spatial skew axes gears are used to transform rotation between shafts with non-parallel and nonintersecting axes. Principles of mathematical modelling of a tooth contact synthesis for this general gearing case are discussed in this paper. The research presented shows that the synthesis of a skew axes gear can be realized by application of two mathematical models: a pitch contact point approach and a mesh region model. These two approaches are applied to synthesis of spatial gear sets of the Spiroid and Helicon types.
Optimization of a heat exchanger network superstructure using nonlinear programming
Authors: Morton W
Published: October 2002

A heat exchanger network design for a particular set of hot and cold stream duties requires multiple stream splits for minimum energy use. A modern NLP solver, FilterSQP, is applied to minimize a total cost function that takes account of capital and energy costs. The best solution contains fewer exchangers than the initial network. There are multiple local optima at various cost levels. They contain different subsets of exchangers of the initial design, which constitutes a partial superstructure for the problem.

Several optimization alternatives are examined:

for the model formulation, leading to problems with different optimum costs, for the way the objective is written, which affects the formal degree of nonlinearity in the equations or objective, and for the way the solver operates.

For each combination of options, tests were run using widely different initial values for the Trust Region size, a parameter in the solver.

FilterSQP solved the network with impressive reliability and efficiency from several starting guesses, some of which were highly arbitrary. From even the most unpromising initial guesses, the solver converged to a local optimum in nearly all cases.
Vortex magnetic separation
Authors: Watson J L S , Li Z
Published: October 2002

Vortex magnetic separation (VMS) is a new technique (1-3) which can not only greatly increase selectivity of high gradient magnetic separation but can also provide a much higher material throughput because high slurry velocity is used. This technique will have a wide range of applications in fields as diverse as mineral processing, biochemical engineering, sewage and wastewater treatment and industrial effluent treatment.

At present in high gradient magnetic separation (HGMS) low Reynolds numbers (with respect to the wire diameter) are usually used and the magnetic product is captured on the upstream side of the wire matrix which results in a serious mechanical entrainment problem that is very detrimental to the purity of the magnetic fraction and to the reduction of the quantity of non-magnetic fraction (4). Vortex magnetic separation runs at moderate Reynolds number ( Re = 6–40) which leads to the formation of vortex flow in the neighbourhood of the matrix. Magnetic particles in the slurry are first concentrated in the boundary layer flow around the matrix and then brought into the magnetically attractive area on the matrix downstream side. The magnetic deposit on the downstream side of the matrix does not suffer the direct collisions with non-magnetic particles in the slurry, so the quality of the magnetic product is drastically improved. As will be described below, a new invention has been made with regard to the VMS matrix which allows capture to take place on both the upstream and downstream sides of the matrix without mechanical entrainment. This paper reviews experimental and theoretical work on the mechanisms involved in vortex magnetic separation.
The behaviour of liquid films and drops in relation to liquid/gas separators
Authors: Gardner N J , Owen I
Published: October 2002

This paper is concerned with separators designed for removing dispersed liquid from gas streams. The main example cited in the paper is a steam/water separator which has to be efficient and preferably compact to work in a high-pressure environment. It is shown how, in general, the separation efficiencies of such devices can be poor at high gas velocities. Reasons for this can be found in the way that liquid films and drops behave. The paper describes this behaviour and shows that understanding it can lead to better separator designs.
The fundamental principles and design considerations for the implementation of centrifugal reverse osmosis
Authors: Wild P M , Vickers G W , Djilali N
Published: October 2002

The paper describes the fundamental principles of a new desalination technology, centrifugal reverse osmosis (CRO), which offers significant benefits relative to the leading existing desalination technology, conventional reverse osmosis. Relations are developed that quantify the primary benefit of the process, reduced energy consumption, and it is shown that the energy efficiency of the process increases with system capacity. Other benefits are discussed, including lower membrane costs and enhanced reliability. The key technical obstacles to the practical implementation of centrifugal reverse osmosis are identified as well as novel and patented design features which overcome these obstacles. A prototype which incorporates these features has been designed, built and tested aboard the Canadian Forces vessel, the St Anthony.
An inverse method for prediction of the required temperature distribution in the creep forming process
Authors: Moreau P , Lochegnies D , Oudin J
Published: October 2002

To achieve the creep forming of glass sheet from designer specifications, the manufacturer has to know the required temperature distribution in the glass sheet accurately: a small variation of the temperature produces great change in the viscosity, and therefore, in the final shape of the sheet. In order to find this distribution, the authors propose an inverse identification procedure based on an optimization method and finite element analyses. The inverse problem is solved using a modified Levenberg—Marquardt method to match the measured displacements to the finite element solutions which depend on the unknown forming parameters. The manufacture of recent rear automotive screens illustrates this efficient numerical procedure.
Metal-to-metal full face taper-hub flanges: Finite element model evaluation and preliminary plastic analysis results
Authors: Spence J , Macfarlane D M , Tooth A S
Published: October 2002

The stress analysis of the flange problem is found to be sensitive to the way in which the component is modelled, particularly so when a finite element program is used to analyse the flange and bolt contact faces. The validity of a number of these finite element models are examined, by comparing the predicted maximum axial bending stress at the intersection of the taper-hub and the cylindrical vessel, with those measured on a large taper hub flange. It is found that a well-thought-through simple model can produce accurate results. In this type of flange it is considered that the magnitude of this stress is critical since, if the bending stress at this intersection reaches yield and subsequently a plastic hinge develops, then undue rotation of the flange could cause leakage. Using an appropriate finite element model, the development of plasticity is studied, from which it is shown that the use of a cylindrical shell yield surface provides a more realistic approach than the simple beam criterion which is unconservative despite its wide use in the existing pressure vessel standards.
Vibrational power flow in beam-plate structures with isolation components
Authors: Yi C , Dietz P , Hu X
Published: October 2002

This paper presents the expressions for the vibrational power flow (VPF) in beam-plate structures (BPSs) with isolation components for three different cases: case 1 is when the isolation component 1 (IC1) is added at the free end of the beam; case 2 is when the isolation component 2 (IC2) is embedded between the beam and the plate; case 3 is when IC1 is at the end of the beam, and IC2 is between the beam and the plate (IC1,2). The BPS is composed of a constant-cross-section beam and a thin flat rectangular plate with four edges simply supported. According to these expressions the corresponding numerical calculations are implemented. The influence of the parameters of the isolation components on the VPF is also considered. The calculated VPF in the structures are compared with the corresponding measured VPF. There is good agreement between them. The analytical method presented in the paper provides a tool for analysing vibrational energy transmission between the support roller and the armoured plate of a tracked vehicle. Some valuable conclusions have been applied to the vibration and noise control of tracked vehicles.
Effect of changes in the taper-hub shape on the strength of high-pressure flanges
Authors: Fessler H , Perry D A
Published: October 2002

Taper hub is the name of a ring of triangular cross-section which is integral with the flange and pipe to strengthen their junction. Eleven models, made of pearlitic-ferritic spheroidal graphite or flake case iron were tested by tightening and pressurizing to failure at room temperature.

Models with four different taper-hub lengths and three different fillet radii were tested. Flange fillet, pipe fillet and pipe strains due to increasing (measured) bolt tensions were recorded and converted to non-dimensional stress indices. An approximately linear response was found owing to tightening and pressurization up to the nominal rated pressure of the basic British standard flange. Bolt tightening caused no stresses in the pipe remote from the taper hub. Pressure caused only small changes at the flange fillet. The lengths of the taper hub could be reduced to five pipe wall thicknesses without increasing stresses above those in the standard shape. Doubling the fillet radius increased the nominal hoop stress in the pipe at burst from 67 to 78 per cent of the ultimate tensile strength of the spheroidal graphite cast irons. A reduction in the hub length does not change the failure pressure.
Elastic buckling of imperfect circular toroidal shells under external pressure
Authors: Galletly G D
Published: October 2002

When perfect, externally pressurized complete circular toroidal shells buckle, the minimum buckling pressure pcr usually occurs in the axisymmetric n = 0 mode, with pcr for n = 2 being only slightly larger. In the present paper, the effects of axisymmetric initial geometric imperfections on reducing pcr for the perfect shell are investigated. Various types of imperfection are studied, i.e. localized flat spots, smooth dimples, sinusoids and buckling mode shapes. The principal geometry investigated was R/b = 10, b/t = 100, although other geometries were also considered. The maximum decrease in buckling resistance, Δ pcr, was found to be about 16 per cent at δ 0/t = 1 and it occurred with smooth dimples at the north (φ = 180°) and south (φ=0°) poles. This value of Δ pcr is not large. Circular toroidal shells thus do not appear to be very sensitive to axisymmetric initial geometric imperfections.

The reductions in the buckling pressure of the above shell, arising because of initial imperfections having the shape of the n = 0 and the n = 2 buckling modes, were 12 and 9 per cent respectively for wo/t = 1. These decreases in the buckling resistance are smaller than that for the ‘two smooth dimple’ case mentioned above.
A review of mechanical reliability
Authors: Martin P
Published: October 2002

This paper reviews the background to mechanical reliability from a design engineering viewpoint. It considers the way in which mechanical reliability is primarily dictated by design decisions and illustrates the reliability engineering models which can provide guidance during mechanical engineering design with some examples. Many modern technological systems involve the integration of multidisciplinary systems. These can be found in such diverse major industries as transportation, power generation, food production, chemical processing and advanced manufacturing. Clearly, the reliability of the mechanical system elements is a crucial consideration in all such highly integrated complex systems. Fortunately, after many years of research and application, the engineering approaches concerned with the reduction in uncertainty are sufficiently well understood to result in the existence of many examples of highly reliable mechanical system elements, although the particular problem of mechanical reliability prediction still exists. In particular, the engineering understanding resulting from an examination of potential failure modes, the messages resulting from a consideration of the load—strength interference theory, the load-chain model, environmental considerations and the complex equipment model are examined to identify the advantages of these approaches as a basis for mechanical design. Some of the many difficulties which still remain in dealing with mechanical reliability are also identified.
Numerical simulation of laminar natural convection in horizontal annuli with radial fins
Authors: Rahnama M , Mehrabian M A , Mansouri S H , Sinaie A , Jafargholi K
Published: October 2002

Natural convection heat transfer in the annular region between two concentric cylinders with radial fins is studied numerically. The basic conservation equations are discretized using the finite volume approach together with the SIMPLER algorithm. Computations are performed for laminar flow with Rayleigh numbers up to 106. The velocity and temperature fields are presented for various Rayleigh numbers and fin heights by streamline and isothermal plots. The local and mean Nusselt number predictions show that the fin height has an optimum value for which the heat transfer rate is increased. Long fins have a blocking effect on flow recirculation.
A computational and experimental study of flows in a distribution chamber: Validation of a numerical model
Authors: Wong V H , Thompson C P , Avery P
Published: October 2002

A computational fluid dynamics (CFD) model of the two-phase flow within a flow distribution chamber is presented in this paper. Several sets of results have been validated against experimental data obtained from a scale model of the chamber.

The interaction between air and water within the chamber, the shape and location of the free surface are modelled by the volume-of-fluid (VOF) model. The k-∊ and renormalization group (RNG) k-∊ models are the two turbulence models used in the simulations.

It is found that both the two-dimensional and the three-dimensional models using the RNG k-∊ model give a good qualitative description of the flow features within the chamber. The three-dimensional results also show very good quantitative agreement with the experimental results.
Condition monitoring of low-speed rotating machinery using stress waves Part 2
Authors: Mba D , Bannister R H , Findlay G E
Published: October 2002

The mechanical integrity of rotating biological contractors (RBCs) and their bearings are vital to maintaining uninterrupted operation. Part 1 of this work presented a study of the high-frequency stress wave (SW) technique as a means of monitoring low-speed RBCs (1 r/min). While the present authors were involved with the development of a monitoring system for RBCs, they also used the opportunity to assess the viability of the application of SWs to monitoring low-speed bearings having bore diameters ranging from 80 to 125 mm. It is concluded that the mechanism of SW generation was the relative movement between mating components experiencing a loss of mechanical integrity, e.g. the loss of tightening torque between the clamped components of RBCs.
Genetic algorithms in optimal safety system design
Authors: Pattison R L , Andrews J D
Published: October 2002

This paper describes a design optimization scheme for systems that require a high likelihood of functioning on demand. For safety systems whose failure could result in loss of life it is imperative that the best use of the available resources is made and that a system which is optimal and not just adequate is produced.
Buckling of imperfect elastic elliptic toroidal shells subjected to uniform external pressure
Authors: Galletly G D
Published: October 2002

The effects of axisymmetric initial geometric imperfections on the buckling pressures of externally pressurized steel elastic toroidal shells of elliptical cross-section are studied in this paper. The shapes of the axisymmetric localized imperfections are increased-radius circular ‘flat spots’ and smooth dimples. In most cases, the locations of the imperfections are at the north (Φ = 180°) and south (Φ = 0°) poles of the cross-section. The main shells investigated are prolate ellipses having k(≡ a/ b) = 1.5, R/ b = 4 and 10 and b/ t = 50, 100 and 500. Some studies of shells with k = 2.0 and 2.5 and k = 0.833 (an oblate ellipse) are also included.
Design of an efficient crashworthy lifeguard for current and future electric multiple unit bogies
Authors: Chirwa E. C. , Searancke E. J. , Hoy A. J. , Wong S. M. P.
Published: October 2002

Lifeguards are energy-absorbing devices fitted to the leading edges of train bogies under driving cab ends. Their primary function is to deflect obstacles away from the wheel/rail interface and in the process absorb excessive impact energy through plastic deformation. This paper presents an experimental investigation into the crashworthiness, the deformation mechanisms and failure phenomena of steel lifeguards for the Class 465 electric multiple unit (EMU) train bogies. Their performance, based on tight specification, is evaluated under both quasi-static and impact loading. Under quasi-stactic loading, the lifeguards have been shown to be capable of withstanding, without permanent deformation to the bogie and its attachment to the axlebox, a load of up to 35 kN applied horizontally in the global longitudinal axis of the train towards the adjacent wheel. The deformation history is found to be that of a plastic hinge developing at the neck or narrowest section which proceeds by rotating the tip about the deformed section. Typical loads necessary for triggering the plastic failure are between 40 and 58 kN; this rises to a maximum of 60-67 kN as the tip rotates around the single hinge mechanism. Under impact loading, the lifeguard shows a failure mechanism that is to some extent similar to that observed under quasi-static testing. The difference, however, is in the collapse mechanism hierarchy which begins with a local plastic indentation at the point of load application and is followed by rotation of the neck about the global principal axes resulting in a three-dimensional failure of the tip. Typical dynamic loads are between 3.5 and 3.8 times the quasi-static loads. Based on the mechanism of deformation observed from the experimental results of the developed lifeguard, preliminary theoretical predictions have been carried out using finite element analysis. The computer outputs show good correlation with experimental results.
Finite element analyses of rolling contact fatigue crack initiation in railheads
Authors: Ringsber J. W. , Josefson B. L.
Published: October 2002

A finite element (FE) tool was developed for the analysis of rolling contact fatigue crack initiation in railheads. An elastic-plastic non-linear kinematic hardening material model is included in the tool, which can model decaying ratcheting rate. The FE tool was applied to rails used in commuter train traffic at a Swedish test site. Two rolling contact conditions were compared, with respect to fatigue crack initiation, by modelling the contact loads differently. The two conditions were newly manufactured rails (Hertzian distribution) and rails that have been in service for 16 months (non-Hertzian distribution). A strategy proposed for fatigue analysis comprises a critical plane approach used together with a multiaxial fatigue model; a damage accumulation rule is also proposed that takes into account low-cycle fatigue and ratcheting damage mechanisms. Together with a two-dimensional FE analysis of a twin disc test, the fatigue evaluation strategy was validated by a set of twin disc data with good agreement. A fatigue analysis of the results from the FE tool show good agreement with observations and measurements made at the Swedish test site with respect to position for fatigue crack initiation, angle of the crack plane and the calculated number of wheel passages to initiation of head checks. Agreement was particularly good for the Hertzian distribution.
Disc machine testing to assess the life of surface-damaged railway track
Authors: Gao N , Dwyer-Joyce R. S. , Grieve D. G.
Published: October 2002

Wheel-rail contacts operate in an arduous and contaminated environment. Railway track running surfaces can become damaged either prior to or during operation. This work is aimed at understanding how that surface damage can affect the life of railway track. Pre-damaged surfaces and track damaged by the entrainment of solid contaminants are considered under both oil and water lubrication. A series of small-scale laboratory experiments has been carried out on a twin-disc rolling-sliding test machine. The test discs are artificially indented and run under typical wheel-rail contact conditions. The experimental results revealed that artificial dents only reduce the fatigue life of the contact under oil, but not water lubrication. With oil lubrication the fatigue failure initiates close to the location of the surface defect. However, with water as the lubricant the whole of the surface undergoes cracking with the defect having no preferential effect. Studies have also been carried out to investigate the damage caused by the entrainment of solid particles into the wheel-rail contact. This kind of damage can accelerate surface fatigue and also lead to excessive wear. An attempt has been made to quantify the wear process and develop a simple empirical model.
An investigation into the aerodynamic characteristics of catenary contact wires in a cross-wind
Authors: Stickland M. T. , Scanlon T. J.
Published: October 2002

An experimental analysis of the aerodynamic characteristics of catenary contact wires is presented. The aerodynamic data obtained were used to calculate the Glauert-Den Harthog criterion for one-dimensional galloping. Utilizing this criterion, the susceptibility to galloping instability of a number of contact wire cross-sections was assessed. The analysis showed that a galloping oscillation can only be induced in a cross-wind when the wire is worn and the flow approaches the wire at an angle of between 7 and 14° to the horizontal. This analysis suggested an explanation for the large-scale oscillations experienced by catenary wires on elevated railway tracks in exposed positions, where the close proximity of the embankment to the wire generates large angles of attack in the flow field around the contact wire.
Infuence of cracked sleepers on the global track response: Coupling of a linear track model and nonlinear finite element analyses
Authors: Gustavson R , Gylltoft K
Published: October 2002

In the procedure of designing a prestressed concrete sleeper to be used in a railway track, irregularities of the wheels and rails may induce substantial dynamic loads that have to be accounted for. A global track model together with a nite element model of the sleeper were used to analyse the inuence of cracks in sleepers on the response of the entire track during a train passage. A train passage was simulated with the track model, and the time history of the vertical displacement at the rail seat position of a sleeper was obtained. This time history was applied to the sleeper in the nonlinear nite element model of both the sleeper and the underlying ballast, and detailed studies of the dynamic behaviour of the sleeper were made. The studies made with sleeper and track models showed that cracks in the sleepers had a minor effect on the direct response of the entire track. However, it is important to realize that cracks in the sleepers greatly reduce their lifetime; hence such cracks are very undesirable. The studies also showed that the interaction between the sleeper and the underlying ballast can be of importance for the dynamic behaviour of the sleeper. During a train passage, the time histories of the vertical displacement for the sleeper and the ballast can involve oscillation out of phase. This results in large impact forces as the sleeper hits the ballast surface.
The development of rail vehicle crashworthiness
Authors: Sutton A
Published: October 2002

The conscious design of passenger vehicles to provide protection to passengers in the event of collision accidents is a development of the second half of the twentieth century. This paper traces the major steps taken along this path in Europe and the United Kingdom and relates the development of the associated structural standards to the emerging vehicle designs. At the present time valuable data are beginning to emerge from the European-funded ‘Safetrain’ project. This work and the safety requirements for European high-speed interoperability are being brought into the common perspective of a European crashworthiness standard for all types of rail vehicle. The structure of this standard is outlined. Some of the current areas of debate associated with achieving the objectives and validating vehicle performance are discussed
Rail passenger equipment accidents and the evaluation of crashworthiness strategies
Authors: Tyrell D. C.
Published: October 2002

The US Department of Transportation's Federal Railroad Administration's (FRA) Office of Research and Development has been conducting research into rail equipment crashworthiness. The approach taken in conducting this research has been to review relevant accidents, to identify options for design modifications to improve occupant survivability and to apply analytic tools and testing techniques for evaluating the effectiveness of these strategies. Accidents have been grouped into three categories: train-to-train collisions, collisions with objects, such as grade crossing collisions, and derailments and other single-train events. In order to determine the potential effectiveness of improved crashworthiness equipment, computer models have been used to simulate the behaviour of conventional and modified equipment in scenarios based on accidents.