bluuebunny/crossref_metadata_2025_split huggingface dataset:
Third Paper: A Theoretical Estimate of the Limits of Ductility in the Free Extrusion Process
Authors: Thomason P. F. 
Published: October 2007

The paper presents a theoretical method of estimating the limits of ductile flow in metal forming operations. The method is applied in detail to the problems of ‘arrowhead’ and ‘fir-tree’ cracking in the free forward extrusion of a bar through conical dies. An approximate method is introduced for integrating the equations of equilibrium along the axisymmetric slip lines in the plastic deformation zone. The results give estimates of the mean extrusion pressures and the bulge limits which compare well with experiments and thus suggest that the theoretical internal stresses will be close to the true internal stresses in free extrusion. The theoretical internal stresses are used, together with the theoretical strains to fracture from the instability theory of fracture, to predict the conditions of die and specimen geometry which lead to internal cracking. The theoretical fracture limits are found to be in close agreement with experimental results.
Experiences of the Italian State Railways with Diesel Shunting Locomotives Using Hydrostatic Transmissions
Authors: Camposano P. , Brandani V. 
Published: October 2007

The Italian State Railways (F.S.) have in service 150 two-and three-axle diesel shunting locomotives equipped with hydrostatic transmission, powered at rates from 150 to 450 hp. In these locomotives some operating characteristics give better performance than locomotives equipped with hydrodynamic transmissions, specifically: easy running reversibility; high flexibility factor which allows elimination of the slow-fast running gears and simplicity of installation. Other theoretical advantages of hydrostatic transmission were found to be unimportant in practice, for example: initial loss of power due to the transmission increases remarkably with service and the braking action is limited by the overrunning of the diesel engine. Disadvantages of the hydrostatic transmissions in service are: the ‘rigid’ connection between the engine and the axles and the absence of ‘coasting’; the maintenance costs of the transmission increase more than linearly with power ratio. In conclusion, the experience of the F.S. with hydrostatic transmission units shows that this type of transmission can be competitive in the field of diesel power of less than 150 kW.
The Response of a High-Pressure Pneumatic Servomechanism to Step and Sinewave Inputs
Authors: Botting L. R. , Eynon G. T. , Foster K. 
Published: October 2007

Linearized analysis is used to design the feedback networks of a high-pressure pneumatic servomechanism in order to meet a performance specification. The effect of torque motor dynamics is pointed out and then digital computation of the complete non-linear equations is used to predict the effect of the following important parameters: saturation, inertia load, stiction and coulomb friction, valve laps and leakage. Others considered briefly are: velocity feedback limiting, position error limiting, the use of a cascade lead network to improve the torque motor response and the effect of different inlet to exhaust port width ratios. The equations are non-dimensionalized, a load factor α being first defined which is the equivalent of a parameter found to be useful in hydraulic servo design. A saturation ratio is later defined which includes α, and quantifies the ratio of electrical pneumatic gain. The major part of the results are for step inputs, but the generally poor shape of the response to sinusoidal inputs is examined in some detail. Experiments were conducted to check the validity of the equations, and it is shown that high loop gains can be achieved with adequate stability. It is also shown that the sinewave response can be improved by the correct design of the shaping networks and by a suitable choice of α.
A General Theory of Composite Gear Trains
Authors: Sanger D. J. , White G. 
Published: October 2007

Some basic gear arrangements which use a minimum number of gears are noted; the gear pairs in these composite gear trains are seen to be interdependent. A general and widely applicable method of gear train analysis is developed. Expressions and index numbers are deduced which define optimum designs and the gear sizes for optimum or other design points. The analysis is extended to include gears external to the composite gear sections, so providing a unified theory which covers all known and feasible minimum-gear arrangements based on three shafts. An example of application is included.
First Paper: An Investigation into the Steady-State Characteristics of Plain Slideways
Authors: Bell R. , Burdekin M. 
Published: October 2007

This paper describes steady-state friction tests on a scraped-cup ground combination of cast iron surfaces. The experimental conditions were representative of the operating conditions on a machine tool feed drive employing plain slideways. The range of the relative sliding velocity investigated was 0 → 1 in s-1, and the influence of lubricant viscosity of both polar and non-polar additive lubricants is shown. An investigation into the effect of oil grooves is also reported. Data obtained from squeeze film measurements enabled the characteristics, normal to the sliding plane, to be specified. These characteristics, together with measurements of the separation of the surfaces, enabled the steady-state friction characteristics to be predicted over the range of mixed and hydrodynamic lubrication covered by the tests. This work formed a basis for the investigation into the mechanism of the friction characteristics under dynamic conditions.
The Italian Heavy Mechanical Engineering Industry
Authors: Gamucci Pier Giovanni 
Published: October 2007

This paper is divided into two parts. The first deals with the Italian heavy mechanical engineering industry in general. It contains a brief history of the industry from the nineteenth century to the present day and then considers three important factors at present affecting the industry: technological progress; the growth of labour-training facilities as the number of men employed increases; the increase in size of companies. The second part deals in some detail with the following sectors of the industry: power-generating machines; thermal power-generating equipment for industrial applications; machine tools; pumps and compressors; lifting and handling equipment. In all these sectors significant progress has been made.
Developments in High-Speed Marine Craft
Authors: Silverleaf A. 
Published: October 2007

Ways of travelling fast and comfortably over water have interested inventors and designers for many years. Recently, impressive and significant developments have led to three relatively unconventional types of highspeed marine craft large enough to serve practical commercial or naval purposes, while some conventional large ships now also have high service speeds. The development of hovercraft, hydrofoil ships and high-speed displacement or planing craft is reviewed in the first section of the lecture, and criteria for assessing the performance of these different types in calm water and in typical service conditions are examined and compared. The purposes for which high-speed marine craft are needed are discussed; these can be divided into passenger and cargo services on short sea ferry routes, container and similar cargo services on longer open water and ocean routes, and special tasks for which high speed, sometimes linked to amphibious capability, can significantly increase effectiveness. Finally, the likely role of high-speed craft in future marine transport and other systems is considered.
The Development of an Electronically Controlled Petrol Injection System
Authors: Croft B. H. 
Published: October 2007

The requirements of the modern automotive petrol engine in relation to higher specific power outputs while retaining good driveability and satisfying the impending exhaust emission control regulations, motivated an investigation into the potential of petrol injection. Consideration of the control requirements and accuracy necessary led, at an early stage, to the selection of electronic control on the basis of control capability, long term reliability, relatively low cost and the potential for future development. The fuel system was designed round the electronic control, manifold injection being used instead of direct injection on the basis of simplicity, lower cost and greater installation flexibility. The original system concept has changed only in detail, development effort being applied to the refinement of the system components to achieve a high standard of performance and the facility to apply the system with minimal modification to a wide range of engine types. The system is described in some detail and typical examples of the system performance on vehicles are presented.
Disc Brake Pad Wear Evaluation
Authors: Moore M. W. , Watton B. 
Published: October 2007

An instrument is described that provides an economical means by which normal motoring on public highways can be used to obtain reliable and relevant brake lining wear rate assessments, thus eliminating the need for the conventional artificial, repetitive, test. The development and final form of the instrument is detailed and its employment to monitor the brake usage, to provide a means of obviating abnormalities and to detect changes in the wear rate of material, is explained. Formulae are derived showing how the wear accumulated during any journey may be related to the mean brake temperature and the distance travelled and graphs are used to demonstrate how the range of application of the instrument accommodates driver changes.
Designing Warships for a Cost-Effective Life
Authors: Raper R. G. 
Published: October 2007

In the past the effectiveness of a ship was measured in terms of her weapon performance, speed and cruising range. Today more attention is paid to availability, in terms of the percentage of her total life for which the ship and all her systems are ready for operations. The lecture outlines the design of modern warships from the basic concept, its justification in terms of cost-effectiveness, the system of modelling costs to indicate the effect on the overall cost of adding or subtracting a weapons system, the development of the design and specification to a point at which the contract can be placed, and the reduction of upkeep costs and crew numbers. Machinery and equipment are being standardized for different classes of ships and the intervals between docking and refit periods will eventually be doubled. Health monitoring of machinery is being investigated as a means of reducing maintenance and increasing reliability. The effect of considering life costs as a percentage of the total spent on procurement, upkeep, modernization, etc, is discussed and the additional work now required during the design process to detail the whole of the upkeep task is outlined. Research and development on materials and corrosion problems are affected by the new thinking.
Onload Cleaning of Steam Turbine Blading
Authors: Keogh F. G. 
Published: October 2007

The paper describes how, by programmed reduction of steam pressures and temperatures, the saturation point in the blade system of a steam turbine may be moved towards the inlet end, thus progressively washing off soluble blade deposits. The condition of steam wetness, produced in the blades, results from the heat drop and it is pointed out that having the machine on load is an essential part of the process. The effects of pressure and temperature variations on turbine expansion and vibrations are also considered. The effect of varying pressure on the boiler brings to light the important fact that this is the more sensitive element in the unit and the drum conditions will limit the process rate. The result of washing is to present the turbine and boiler in the optimum condition for maintenance. The saving in cooling time is considerable, barring time on a 60 MW turbine is reduced by 50 h and the boiler may be cooled and emptied of water overnight.
Extrapolation of Creep Strain and Rupture Properties of 1/2 per Cent Cr, 1/2 per Cent Mo, 1/4 per Cent V Pipe Steel
Authors: Cummings W. M. , King R. H. 
Published: October 2007

Both 1 per cent total plastic strain data and rupture data of up to 21 000 h duration are presented for 1/2 per cent Cr, 1/2 per cent Mo, 1/4 per cent V pipe steel. Four parametric methods commonly used for extrapolation purposes are assessed for their accuracy of prediction within the time covered by the present experimental data. The Manson-Haferd parameter, which emerged as the most satisfactory of the four, is used as the basis for the long-time estimates of material properties. Based on the full 1 per cent strain and rupture data, 10 000, 30 000 and 100 000 h predictions are compared with the current British Steelmakers' Creep Committee recommendations. The tendency of both the Larson-Miller and Orr-Sherby-Dorn parameters to provide optimistic estimates at longer times is again demonstrated, and while the Manson Generalized parameter fits the data excellently within the experimental range, it is shown that care is required in selecting values of parametric constants if instability is to be avoided. To meet the increasing need for long-time creep strain data, each individual creep curve is represented by a creep strain/time relationship.
Wind Effects on Structures
Authors: Scruton C. 
Published: October 2007

After several spectacular collapses caused by wind, there has been increased interest in the accurate prediction of the wind loading to which buildings and structures are subjected. The reliability of these design wind loads depends to a very large extent on the accurate prediction of the most severe wind conditions to be experienced for many years into the future, and on the accuracy of the wind force and pressure coefficients applicable to the structure. Many factors influence these coefficients and hitherto many of these factors have not been reproduced in measurements on models in wind tunnels, so much of the existing data is of uncertain reliability. For many structures it is sufficient to regard the wind as causing static loadings and for this purpose to use time-averaged wind forces. However, the advent of modern design and fabrication of structures has rendered them more prone to respond to the dynamic action of wind. Increasing attention is therefore being given to the time-dependency of the wind forces resulting either from the fluctuations of speed caused by the turbulence of natural wind, or from some form of aerodynamic instability arising from the interaction of the structure with the airstream. The calculation of the dynamic response to turbulent winds involves the application of statistical theories to calculate the maximum amplitude of the response (stress or displacement) and the frequency of its occurrence, coupled with the concept of an acceptable degree of risk that the structure will not fulfil its functional requirements during its lifetime.
Third Paper: The Behaviour of Lubricated Steel Balls under Close-Conformity Aero-Engine Mainshaft Ball Race Conditions
Authors: Haines D. J. 
Published: October 2007

The behaviour of individual ball to track contact areas is studied in close conformity oil lubricated conditions. Although primarily concerned with aero-engine operating conditions the results are expressed in dimension-less forms which permit use over a wide field of ball race geometries. An arbitrary boundary is established, based upon electrical conductance through the oil film, between running conditions which produce minimal wear damage and conditions which are probably unacceptable from this point of view. The major purpose of the paper is to focus attention on this criterion and to relate ball to track kinematic situations to it.
Design of Large Diesels for Operational Reliability
Authors: Bertodo R. 
Published: October 2007

This paper considers the conventional approach to the design of large diesel engines, based, as it generally is, on experimental validation by limited engine and/or rig running. It is concluded that to ensure the attainment of a specific degree of reliability the extent of testing required would be economically prohibitive. Consequently, the amount of testing undertaken is largely irrelevant and the failure rates to be expected in service are a matter for intuitive judgement and good fortune. An attempt is made to establish more realistic design criteria for engines manufactured in small batches and designed to remain operational for long periods of time (15-20 years, typically) with infrequent major overhauls (say, every 20 000 h). It is shown that for structural integrity this may be achieved if the criterion [Formula: see text] is met, where [Formula: see text] is the mean strength derived from ideal specimens, [Formula: see text] is the mean load obtained from a consideration of the engine manufacturing and operational tolerances, f is a factor taking into consideration deterministic errors in [Formula: see text] and [Formula: see text], and r is a statistical risk factor characteristic of the component and application. Typical values for f and r are derived for a medium speed diesel and the detailed application to a typical critical engine component described. The economic implications of design on the basis of failure rate, rather than arbitrarily chosen safety factors, are discussed in terms of design economy and better understanding of the factors likely to influence service reliability.
A Laboratory Pneumatic Tyre Testing Rig
Authors: Phillips B. D. A. 
Published: October 2007

The author describes a tyre testing rig which has recently been designed and constructed at the Lanchester Polytechnic, Coventry. The rig measures the six force and moment components acting in the contact patch of a tyre rolling slowly on a flat continuous surface for a wide range of slip angles, camber angles, tyre pressures and wheel loads. Either driving or braking torques can be applied to the wheel axle and both the slip angle and the lateral displacement of the wheel can be varied sinusoidally or instantaneously in order to investigate the frequency responses and step responses of tyres.
The Influence of Surface Roughness on the Capacitive Measurement of Film Thickness in Elastohydrodynamic Contacts
Authors: ten Napel W. E. , Bosma R. 
Published: October 2007

Measurements of oil film thickness according to the capacitive method as carried out on a disc machine with discs having a surface roughness of 10 μin c.l.a. showed marked deviations from the theoretical values predicted by Dowson and Higginson (1)†, especially in the region of small film thickness, i.e. smaller than 0–6 μm (23·6 [μin). In this paper the authors show that surface roughness is the cause of this discrepancy.
Transient Torque of Steam Turbines in Power Systems
Authors: Sheard G. , Evans F. J. 
Published: October 2007

Techniques for the calculation of the transient torque of a steam turbine following step and ramp type displacements of throttle valves are developed. The objective is an improvement in steam turbine representation for digital and other studies of electric power systems under disturbed conditions, including transient stability. The turbine model used as a building block for the transient theory is a length of pipe, representing loop pipe or reheat boiler, followed by a multi-stage turbine. The theory of unsteady flow of compressible fluids is applied to the problem and this, together with throttle, nozzle and steam turbine equations, allows the transient torque to be calculated. A digital computer programme has been developed which could be used as a sub-routine in an overall transient stability programme. The dominant transient feature is a transport lag and not an exponential time delay, as is commonly assumed. Moreover this transport lag, being associated with the local sonic velocity rather than the steam particle velocity, has a value about one-tenth of the usually assumed exponential time lag in mass-flow. Methods are indicated for extending the transient response obtained for the above turbine model to multi-cylinder turbines. The conclusion to be drawn is that, for any fast turbine control or transient condition (on a time-scale of seconds rather than tens of seconds), the conventional assumption of an exponential time constant will be substantially in error. Such fast disturbances will almost certainly have their origins on the power system side. It is from the power system point of view that this paper is written.
Effect of Specimen Size and Preparation on the Fatigue Strength of a Plain Carbon Steel Tested in Rotating Bending and in Torsion
Authors: Kelly D. A. , Morrison J. L. M. 
Published: October 2007

A survey of the literature indicates that, in the presence of a stress gradient, the fatigue strength of large components is generally less than the fatigue limit exhibited by small specimens of similar material. In some cases the ‘size effect’ reported is of alarming proportions. However, a closer examination of the literature and the results of some exploratory tests in rotating bending suggest that the effects observed may not be attributable simply to size but may also be dependent on the final stages of specimen preparation. An extensive test programme carried out on notch-free 0·32 C steel specimens, ranging in minimum diameter from 0·05 to 05 in in torsion and from 0·05 to 1·6 in in bending, provides results showing four main features. As other workers have found, very small specimens have generally high fatigue limits and as-polished specimens have higher fatigue limits than as-heat-treated specimens. For specimens that were normalized, carefully machined and polished, then stress-relieved and finally lightly repolished, the fatigue strength shows a significant increase as the diameter decreases, the maximum increases being about 15 per cent in torsion and 20 per cent in bending. For specimens finally stress-relieved the size effect, over the ranges from 0·25 in diameter upwards, is negligible.
Analogue Investigation of the Inertia-Coupled Free-Piston Engine
Authors: Moore A. 
Published: October 2007

An engine is described in which a free piston is located inside a cylinder assembly which is also allowed freedom of movement in the axial direction. Power is taken from the unit by coupling the pistons of a hydrostatic pump directly to the cylinder assembly. The equations of motion for the device are presented in non-dimensional form, and solved with the aid of an analogue computer. Results are presented for an engine of practical dimensions and the inherent ability of the system to torque multiply is confirmed. Estimates of the overall mechanical efficiency are included.
The Design and Performance of High-Pressure Injectors as Gas Jet Boosters
Authors: Hoggarth M. L. 
Published: October 2007

Injectors have a large potential application as jet boosters in gas distribution networks by using the gas from high-pressure supplies to boost the pressure of gas from low-pressure holders to that required by the distribution system. A theoretical study of the design and performance of injectors for this purpose is described. A one-dimensional theory which takes friction into account is proposed for predicting the performance of injectors with driving pressure ratios up to 14:1. Optimization of the theoretical equations is carried out so that the most suitable dimensions can be chosen for any specified performance. Alternatively, the best operating conditions for a given geometry may be predicted. Experimental results compared well with predictions from the proposed theory particularly in the region close to the optimum working point. Where deviations did occur these are explained by the excessive recirculation of the driving gas at the inlet to the mixing throat, when operated away from the optimum working point at low injection ratios and high pressure lifts. By moving the driving nozzle closer to the inlet of the throat and dispensing with the inlet cone, marked improvements in performance could be obtained at these off-optimum operating conditions.