bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability of Complete Circular and Non-Circular Toroidal Shells
Authors: Galletly G D , Blachut J 
Published: February 2007

In the first part of the paper a comparison of various theoretical methods for predicting the elastic buckling pressures of externally pressurized complete circular toroidal (that is doughnut shaped) shells is given. Calculations were also carried out using the BOSOR 5 shell buckling program. The accuracy of the latter was checked using two independent programs. The available experimental results on toroidal shells, from the United States and Russia, are summarized and their buckling pressures calculated using BOSOR 5. A simple equation for predicting the buckling pressures of these shells, due to Jordan, is also briefly reviewed. The buckling of externally pressurized complete elliptical toroidal shells is then discussed. Both buckling pressures and buckling modes for selected geometries are given. Depending on the major/minor axis ratio, the buckling pressures of the elliptical toroids can be larger or smaller than those of the corresponding circular toroids. Some part-cylindrical, part-spherical cross-sections were also explored. Buckling due to internal pressure is considered in the third part of the paper. It is predicted to occur for several complete toroids of elliptical cross-section. It is believed that this is a new result. It still has to be verified experimentally.
Transmission Line Modelling of Simulated Drill Strings Undergoing Water-Hammer
Authors: Beck S M , Haider H , Boucher R F 
Published: February 2007

Drill strings and oil production lines are examples of fluid systems for which time-dependent (dynamic) as well as steady state (static) analysis is increasingly needed. These systems are difficult and expensive to instrument and test experimentally. Developments of fluidic non-moving-part controllers to produce water-hammer pulsations stimulated a need to simulate the fluid dynamics of such drill strings to aid the design work. The method of simulation chosen was transmission line modelling (TLM). It is essentially a time-delay method, borrowing its main concepts and the fundamentals of its computational solution scheme from early work by others in the field of electrical power lines. In its elementary form, a fluid network is treated as a set of pipes (or pipe segments) where waves travel with pure time delay. Connecting the pipes are junctions of various types at which the waves are scattered (transmitted, reflected and/or attenuated). The merits and limitations expected with this methodology in comparison with the method of characteristics (MOC) and other wave-analysis methods are discussed. The first adaptations of TLM were for small perturbation analysis. The presentation here takes such work further forward to model large-scale waves in pipe networks of almost arbitrarily complex topology. The basic theory behind the method is presented and the solution schemes are formulated mathematically with comments on the type of data structure and algorithms needed to undertake computationally such solutions. With the aid of modules described elsewhere, providing comprehensive steady state modelling capability, the software provides a powerful tool for implementing static and dynamic TLM simulations of networks. One of the novel aspects of considerable benefit is the ease of implementation of time-varying junctions capable of representing the overall action of control elements such as the fluidic controllers mentioned earlier. A large experimental laboratory facility with a simple circuit containing the essential hydrodynamics of drill strings was used to gather data on water-hammer pulsations. A controlled solenoid valve with a high-resistance bypass acted as an alternating high and low resistance in the main pipe loop. A simplified version of the circuit was simulated with TLM to compare and discuss the results. The TLM time-domain results took a few seconds of computer processing time and revealed the basic features of the circuit dynamics quantifying water-hammer to a fair and useful accuracy. Such results were encouraging and confirmed the power of this computational method as an aid in the design process.
Effects of Trapped Residual Concentration and Surface Temperature on the Combustion Process of a Two-Stroke Cycle Spark Ignition Engine with an Air-Assisted Fuel Injection System
Authors: Chiu C-P , Horng R-F 
Published: February 2007

Poor combustion is one of the drawbacks of two-stroke cycle engines operated at light load condition. Dilution with residuals is the most likely cause for this phenomenon. The main objective of this study was to reduce the residuals within the cylinder in order to improve the combustion performance and hydrocarbon (HC) emission. Experiments were conducted on a 124 cm3 two-stroke cycle engine with a low-pressure air-assisted fuel injection system at idling condition. The main areas of investigation were the effects of trapped residual concentration, air injection pressure and surface temperature on combustion and HC emission. The trapped residuals were reduced using a skip firing strategy with skip numbers of 0, 1, 2, 3, 4 and 5. The air injection pressure was varied in the range of 50–300 kPa and the surface temperature was changed from 120 to 180°C. The in-cylinder gases, cylinder pressure and HC emission were measured simultaneously. Results showed that the skip firing had a significant improvement in the concentration of oxygen as well as the residuals trapped in the cylinder. A suitable combination of skip firing and surface temperature control could be a potential measure to improve the combustion and the HC emission at light load. Meanwhile, it also illustrated that the air injection pressure exerted no significant influence on the results.
Wind Loading on Articulated Trailers During Tipping
Authors: Fessler H , Hyde T H , Sun W 
Published: February 2007

Modern articulated trucks have very large trailers, up to 11 m long. When they empty their load, the body may be inclined at up to 40° this causes a high obstruction to sideways winds, which may cause the vehicle to roll over. The lateral force and the roll-over moment were measured in wind tunnel tests of a 1/60 scale model of a typical truck with the body at different tipping angles, ψ, and the wind in different directions, α. The side force coefficient was found to be approximately 1.5, almost independent of ψ, α up to 15° and Reynolds number up to 340000. The resultant of the wind force was found to act at almost the same height above the ground as the centroid of the lateral area for all values of ψ.
A Comprehensive Simulation Model for Mixing and Combustion Characteristics of Small Direct Injection Diesel Engines
Authors: Mehta P S , Singal S K , Pundir B P 
Published: February 2007

An analytical model has been developed to predict the fuel-air mixing and burning characteristics of small direct injection (DI) diesel engines. Four mass and momentum conservation equations are written along the tangential and normal directions to the spray for both free and wall regions based on the continuum integral approach. The spray structure is multi-zonal and the simulation of atomization, droplet-size distribution, evaporation, turbulent mixing and combustion processes is included. The model predictions show good correlation with the experimental data and respond well to the variations in input parameters. The level of predictions from the model is satisfactory and the model is quite suitable to optimize the injection characteristics bowl geometry and air motion in small DI diesel engines.
An Investigation of Anti-Lock Braking Strategies for Heavy Goods Vehicles
Authors: Hardy M S A , Cebon D 
Published: February 2007

An articulated lorry was instrumented in order to measure its performance in straight-line braking. The trailer was fitted with two interchangeable tandem axle sub-chassis, one with an air suspension and the other with a steel monoleaf four-spring suspension. The brakes were only applied to the trailer axles, which were fitted with anti-lock braking systems (ABS), with the brake torque controlled in response to anticipated locking of the leading axle of the tandem. The vehicle with the air suspension was observed to have significantly better braking performance than the steel suspension, and to generate smaller inter-axle load transfer and smaller vertical dynamic tyre forces. Computer models of the two suspensions were developed, including their brakes and anti-lock systems. The models were found to reproduce most of the important features of the experimental results. It was concluded that the poor braking performance of the steel four-spring suspension was mainly due to interaction between the ABS and inter-axle load transfer effects. The effect of road roughness was investigated and it was found that vehicle stopping distances can increase significantly with increasing road roughness Two alternative anti-lock braking control strategies were simulated. It was found that independent sensing and actuation of the ABS system on each wheel greatly reduced the difference in stopping distances between the air and steel suspensions. A control strategy based on limiting wheel slip was least susceptible to the effects of road roughness
An Investigation into Objective Measures of Gear-shift Quality
Authors: Moir G B 
Published: February 2007

During any synchromesh development programme, reliable methods for evaluating and assessing the gear-shift quality are necessary. In order to overcome the reliance on a trained driver and associated subjective judgement, methods have been investigated to describe the gear-shift characteristics using objective, rather than subjective measures This paper describes the measurement and calculation of objective measures that relate to perceived shift quality. Examples are given on the use of these measures to evaluate the effect of production variability on shift quality, and to allow comparisons of shift quality to be made between competitive vehicles
On-Line Mass Spectrometric Characterization of Hydrocarbons in Engine Exhaust Gases
Authors: Lehrle R S , West H , Wyszyński M L 
Published: February 2007

Mass spectrometry provides a powerful and versatile method for the characterization of the unburnt and also the pyrolysed and partially oxidized gaseous hydrocarbon species present in exhaust gases. Flame ionization detection, the usual analysis method for measuring exhaust hydrocarbons, can give only a total hydrocarbon figure when used on-line. A mass spectrometer can perform the on-line characterization of the individual gaseous hydrocarbon species in the exhaust and can detect any trends in their concentrations. This permits the rapid assessment of experimental approaches for reducing these pollutants. In the present work exhaust gases have been sampled from the exhaust of a Ricardo E6 research engine fuelled with gasoline and they pass to the analysis equipment via heated sample lines. The gases can be analysed as discrete samples by gas chromatography mass spectrometry (GC–MS) in order to identify the components, or can be continuously monitored by mass spectrometry alone (MS) in order to measure any trends in the component concentrations. These mass spectrometric analysis techniques have been compared with other gas analysis and general data acquisition methods, and have permitted the collection of much information about engine exhaust emissions. This information has been related to engine operating parameters with special reference to the fuel–air ratio. The results from this work show that not only does the combustion result in an increase in the relative amounts of NO and CO2, but also suggest that the substituted aromatic hydrocarbons may be products of combustion. Continuous monitoring of specified exhaust components has been performed mass spectrometrically and related to the air–fuel ratio used for the engine. With lean fuels, the hydrocarbons are not totally combusted, but those that are burnt are combusted with reasonable efficiency. On the other hand, rich mixtures are associated with not only inefficient combustion, but also incomplete oxidation (that is CO–CO2 ratio is increased), and an increase in the substituted aromatic hydrocarbons. Stoichiometric mixtures have been found to be associated with most efficient combustion (highest CO2–CO ratio) and minimal hydrocarbon emissions.
From Technology Strategy to Technology Development Programmes in the Power Plant Industry
Authors: Riitahuhta A O , Salminen V K , Iivonen H T 
Published: February 2007

It is widely accepted that the global environment requires the creation of a new manufacturing paradigm. The new paradigm has to take into account the limits of the global environment, provide more customized products with higher value added, have the capability to re-configure the products for different purposes and also produce and reproduce a single product in various facilities. As one principal idea of the new paradigm, environmental consciousness is becoming one of the core competencies of a company. Customers require environmentally friendly products and society requires environmentally conscious manufacturing from the company. This is the reason why companies must take environmental consciousness seriously in their technology strategy as part of the business strategy. Some of the ideas under development today will become future core competencies of the company. Three industrial case studies are presented here. Process plants form a major part of Finnish heavy metal and engineering industry production. Many of the companies in the specialized fields are market leaders in the world. A number of major companies in the Finnish metal and engineering industry have started a technology development program, PRODEA—development of process plant realization—to utilize the latest CIM (computer integrated manufacture) technologies for the enhancement of process plant realization. Two test cases describing the use of expert systems and case-based reasoning technology in supporting the realization are presented in this paper.
High-Speed Third Rail Shoegear
Authors: Hartland D J 
Published: February 2007

The introduction of through-running trains between England and France has required the provision of shoegear to run on the British Rail (BR) system, and this shoegear must retract clear of the rail for operation in France and Belgium (SNCF and SNCB). This paper describes the shoegear development work. An initial design concept was compared with existing experience; mock-ups were tested to confirm essential interfaces with the bogie and track, and prototypes were installed on a test train. The paper will describe the experiences of these trials and the running of the pre-series train on BR and SNCF. GEC-Alsthom, the main contractor for the TMST Eurostar trains, awarded the contract for current collection to a joint venture between Brecknell, Willis of Chard, England, and Faiveley SA of Tours, France. The two companies have a total of 180 years experience in electric traction and the shoegear design was to be a joint exercise. A version of this paper was originally presented at the Railtech conference in May 1994; since that time the Eurostars have entered full passenger service and the shoegear has met the requirements of full regular passenger service.
Certification of the Composite Outer Wing of the ATR72
Authors: Tropis A , Thomas M , Bounie J L , Lafon P 
Published: February 2007

The ATR72 was the first civil aircraft with a composite wing, to be certified JAR/FAR 25 (Joint Aviation Requirements/Federal Aviation Regulations). Using the latest developments composites ACJ 25603, AC20-107A comply with the requirements of JAR/FAR 25; the ATR72 composite outer wing box was certified by the DGAC in September 1989 and by FAA in December 1989. This paper deals with Aerospatiale's innovative approach, focusing on four major certification topics: the determination of allowables from statistical analysis substantiated by tests on cross-ply plain and notched laminates; the fatigue and damage tolerance substantiations performed by analysis to show the non-initiation of fatigue damage and by full-scale test for the no-growth of acceptable manufacturing defects and accidental damages; the development of a probabilistic approach to determine the inspection intervals for accidental impacts in damage-tolerance justifications; the compliance philosophy developed to qualify a second source material (approved by the company in 1992).
Comparative Analysis of Bone Stresses and Strains in the Intoss dental Implant with and without a Flexible Internal Post
Authors: Clift S E , Fisher J , Edwards B N 
Published: February 2007

The clinical success of any dental implant is dependent upon the maintenance of good-quality bone supporting it. Previous studies have shown high values of strain around the neck of an implant under lateral loading. These high values may lead to fatigue damage and resorption in lower strength cancellous bone. In this study, the finite element method has been used to study the bone strain distribution around the following implants: (a) an Intoss dental implant, referred to as the ‘standard’ implant; (b) a comparative Branemark implant and (c) a modified Intoss implant with a central flexible post, referred to as the ‘modified’ implant. Three different bone distributions have been investigated under axial and lateral loading: (a) implant surrounded by cortical bone; (b) implant tip supported by cortical bone with a thin layer of cancellous bone along the length and top of the implant; (c) implant tip and top supported by cortical bone with a thin layer of cancellous bone along the remaining length. For the standard implant, similar maximum equivalent strain values were predicted for the bone surrounding a comparable length Branemark-type implant. Modification of the standard implant design to include a flexible central post resulted in a decrease in the maximum von Mises stresses and equivalent strains in the cancellous bone. It is postulated that this will reduce the likelihood of bone fatigue failure and subsequent resorption in this bone. Thus the proposed design change is predicted to be highly beneficial in terms of bone load transfer.
Generalized Finite Difference Methods for Optimal Estimation of Derivatives in Real-Time Control Problems
Authors: Harrison A J L , Stoten D P 
Published: February 2007

The real-time estimation of (particularly first and second) derivatives of motion from position data has many applications in automatic control. Errors in such estimates at high sampling rates arise from noise or quantization of the data and from the presence of high-order derivatives of motion at low rates. This paper presents a generalized method to allow estimation of derivatives of orbitary order from position data, with minimum overall error, for a given signal-to-noise ratio and sampling-to-signal frequency ratio. Experimental results included in the paper show that the theory is borne out in practice.
Debris and Roughness in Machine Element Contacts: Some Current and Future Engineering Implications
Authors: Sayles R S 
Published: February 2007

The influence of surface roughness and third-body particulates on tribological contacts will be reviewed in general, but in particular their influence on rolling contacts and contacts where rolling and sliding occur simultaneously will be considered in some detail. Such non-conforming contacts are often referred to as Hertzian, and when lubricated are often considered to be protected by an elastohydrodynamic (EHD) lubricant film. Transferring these concepts to the loaded interfaces of real engineering components such as gears, rolling bearings, constant-velocity joints and cams, etc., can have serious shortcomings and lead engineers to many misconceptions. Roughness often appears to dominate over the theoretical size of lubricant films and can create a contact geometry and local stress distribution far removed from the smooth surface case. Even in ball-bearings where surfaces are some of the smoothest of all mass-produced engineering components, lubricant-borne debris particles are usually many times the theoretical film thickness and the damage they can cause can quickly destroy the production engineer's good work in creating smoothness, as well as having a significant influence on component performance. The paper reviews such aspects in terms of recent research and explains some of the many practical implications of roughness and debris that are faced at present, and also speculates on the implications for the future, when roughness geometry and surface properties might be engineered to suit a particular lubricant and its potential contaminant population.
The Hydrodynamic Phase of Gearbox Synchromesh Operation
Authors: Paffoni B , Progri R , Blouët J , Gras R 
Published: February 2007

The approach used is to divide the synchronization process into three distinct stages according to the friction regime operating, this idea being closely allied to that of A. E. Anderson (1972, SAE paper 750521). The authors proceed to derive a model for the first stage based on a shaft-ring pair with or without taper defects (angular mismatch). Expressions are derived for contact pressure (and hence axial force), output torque and the coefficient of friction, the latter pair being arrived at by considering the shear stresses acting at the cone surface. The results that are gained allow best and worst cases of torque and friction to be considered and the effect of circumferential grooves and axial slots to be theoretically examined, and the potential for this model in simulating such configurations is discussed. The main conclusion of the paper is that the coefficient of friction clearly decreases during the first stage such that the value during the second stage may be quite small (results of the analyses of the second and third stages are promised for the future), but it is now relatively simple to estimate this with acceptable accuracy.
Adaptive and Compensation Methods in Free-Form Surface Assessment
Authors: Ip W L R , Loftus M 
Published: February 2007

The assessment of manufactured surfaces by coordinate metrology techniques has changed in recent years. Speed, accuracy and flexibility have all improved with the introduction of coordinate measuring machines (CMM). However, some technical problems have yet to be solved, in particular those pertaining to free-form surfaces. This paper considers the influence of surface features and probe tip geometry on the assessment of free-form surfaces. Inaccurate measurements due to the problems of probe tip diameter and undulating surface curvature have been investigated, and a simple mathematical compensation technique for different probe diameters and an adaptive measuring point planning strategy have been developed. Experimental data confirm that the measuring errors are significantly reduced when the probe tip diameter compensation approach is used. The problems of machined surface measurement have also been considered and a method, namely least-squares data fitting, is proposed to give a better qualifying technique for the cusped surfaces. This new technique has been implemented and the results from the case study indicate that the least-squares method can give a more precise representation of the quality of a machined surface than standard statistical measurement systems. Experimentation also indicates that the results of the least-squares data fitting method are consistent with the CMM computed values, which verifies the reliability of the method.