bluuebunny/crossref_metadata_2025 huggingface dataset:
Gyroscopic Loading Tests on a Gas-Turbine Rotor
Authors: Wilson W. Ker , Harris W. J.
Published: October 2007

Amongst the important matters investigated after the accident to a ‘Comet’ aircraft at Elba in 1954 and the recovery of the wreckage from the sea, was the severe damage which had been sustained by the turbine rotor hub-shafts.

Three of the four engines were recovered with the turbine rotor disks intact, though extensive cracking was discovered in the spigot recess radii of the hub-shaft flanges. In the case of the fourth engine, the turbine rotor disk was missing, through fracture of the hub-shaft flange.

A careful step-by-step examination of all the evidence enabled it to be stated quite definitely that the damage sustained by the engine hub-shaft assemblies was a consequence of abnormally severe gyroscopic bending moments imposed during disintegration of the aircraft.

Nevertheless, it was considered desirable to determine by practical tests the actual magnitude of the gyroscopic bending moment which the hub-shaft assembly could sustain and the manner in which fracture would occur.

The paper describes the special gyroscopic test-rig constructed for this purpose and discusses the results obtained. The results of supplementary investigations of the bending fatigue behaviour of hub-shaft assemblies and plain and notched laboratory specimens, with special reference to the high-stress low-endurance portion of the fatigue diagram, usually called the ‘high-level’ fatigue region, are also included.
Behaviour of Compressed Asbestos-Fibre Gaskets in Narrow-Faced, Bolted, Flanged Joints
Authors: Donald M. B. , Salomon J. M.
Published: October 2007

In an attempt to establish the conditions necessary to maintain ‘tightness’ in narrow-faced, bolted, flanged joints, experiments were carried out on standard 300 lb. per sq. in., 900 deg. F. screwed-on and welded-on flanges fitted to 2 1/2-inch bore pipes. ‘Klingerit’, rubber-bonded asbestos, gaskets of various dimensions were tested. Stresses in the bolts were measured by means of electrical resistance strain-gauges. The pressure fluid used was water.

The screwed-on flanges were later turned down to approximately half their original thickness to determine the effect of flange thickness on leakage pressure.

Photo-elastic studies were carried out to determine the distribution of axial stress in the gasket due to bolting up.

The following points were established:

(1a) The gasket factor, m, of compressed asbestos jointing increases practically linearly with gasket thickness. This is the opposite of the trend of the values given in the A.S.M.E. Unifired Pressure Vessel Code of 1952 (A.S.M.E. 1952). (1b) The gasket factor of compressed asbestos jointing increases with decreased gasket width. (2) The gasket yielding pressure, y, of compressed asbestos jointing is, for water as pressure fluid, independent of gasket dimensions. (3) Bolt stress may increase, decrease, or remain constant during increase in internal pressure, in one and the same joint, depending only on the initial bolt stress. (4) The centre of gasket reaction is situated closer to the outer edge of the gasket than to the inner; the exact position depending on the relative stiffness of the flange and gasket material. (5) Increasing thickness or decreasing width or external diameter of the gasket reduces the pressure which the joint is capable of containing. (6) Reducing the thickness of the flange ring increases the gasket stress necessary to contain any particular internal pressure.
Dynamic Loads on the Teeth of Spur Gears
Authors: Harris Stephen L.
Published: October 2007

In a theoretical analysis of a single pair of high-class gears three internal sources of vibration are considered:

(1) Periodic variations in the velocity ratio due either to running the gears above or below the designed load, or to small manufacturing errors. (2) Period variation in the tooth stiffness. (3) Non-linearity in tooth stiffness.

The amplitudes of vibrations caused by (1) depend on damping, while those caused by (2) or (3) will only occur if the damping is below a limit estimated at 0.07 of critical damping. Damping currently reported for tests on steel gears is about 0.1 of critical, but might well be less.

Dynamic tooth forces and amplitudes of vibration were found from photo-elastic stress patterns of model gears with both small and large errors. The more accurate gears showed only vibration caused by (1), variation in the velocity ratio, because the damping was too great for the other modes.

Information on damping is insufficient for satisfactory prediction of dynamic increments. If the damping in any gears fell to 0.07 of critical the increment, instead of having a small value, might equal the applied load, irrespective of any errors, and this might prove disastrous.
Rake Correction in the Measurement of Parallel External and Internal Screw Threads
Authors: Marriner R. S. , Wood J. G.
Published: October 2007

Formulae are derived for calculating the rake correction for a ball seated in the helical groove of an internal screw thread and a ball or cylinder in an external thread. The equivalence of a ball and cylinder in an external thread is discussed. A simple approximation formula and a precise formula are derived for determining when double contact between the cylinder and thread flank occurs.
First Year of Operation of a Cyclone-Fired Boiler
Authors: McCulloch R. P. , Willetts J. R. , Richardson A.
Published: October 2007

This paper is intended to give an account of experiences during the first year's operation of the first cyclone-fired boiler to be commissioned in Britain. The reasons for the choice of a cyclone-fired boiler are given and its relation to the plant previously installed is described. The early operational difficulties and the actions taken to overcome them are discussed.

The results of official tests are given which show that the boiler efficiency is over 88 per cent on the gross calorific value and efficiencies of this order are being regularly attained in commercial operation. The performance of several widely differing coals in the cyclone are described and various factors which affect their suitability for burning in a cyclone are discussed.

The conclusion is reached that after some ‘teething troubles’, the boiler is now giving even a better commercial performance than was envisaged at the time of its inception and that the choice of such a unit has been completely justified.
Theoretical Analysis of the Stresses Induced in a Spherical Pressure Vessel Due to the Constraining Effect of a Cylindrical Skirt
Authors: Hicks Raymond
Published: October 2007

This discussion deals with the stresses induced in a spherical pressure vessel due to the constraining effect of a cylindrical skirt. The skirt is taken as being made of two sections having different thicknesses, one section being located inside the vessel and the other directly underneath on the outside of the vessel.

Expressions are obtained for the bending moments and shear forces induced in the vessel and its skirts when (1) the vessel is stressed by a uniform radial pressure and (2) the skirts are loaded in an axial direction. The general case of an arbitrary load system is also considered and expressions are obtained for the induced moments and shear forces in terms of a set of constants which can be evaluated readily when dealing with any particular problem.

In an appendix the general solution is used to consider briefly the particular cases ( a) Temperature gradient in the bottom skirt. ( b) Self weight of the vessel, ( c) Axial load on the vessel.
Transverse Gauge Variation in Strip and Sheet Rolling
Authors: Saxl K.
Published: October 2007

Large forces acting on the working surfaces of rolls in a mill producing strip or sheet will deform these rolls and, in an endeavour to obtain products of uniform thickness, the roll surfaces are ground to a shape which would compensate for this deflection. Unsupported rolls deform by bending and local compression of the surface, and the latter results in edge thinning. Work rolls of backed-up mills, in addition, deform owing to the effect of the elastic support afforded by the backing roll. The mechanism of deflection is investigated and remedies suggested.

Variation of thickness across the strip and particularly its redistribution is shown to be responsible for a number of troubles such as locked-up stresses in the rolled strip, buckling and waviness of strip, edge cracking, lateral deflection of rolls, etc. The performance of a wide four-high mill can be much increased, particularly when rolling narrow strip, provided the secondary deflection of the work roll is controlled. This enables use of more slender rolls which, in turn, makes it possible to roll harder metals to smaller gauges.
Clean Rooms for the Assembly of Electrical and Mechanical Instruments
Authors: Harris H. G.
Published: October 2007

The demands now made upon the sensitivity and reliability of some classes of electromechanical instruments make it imperative that particulate and other contamination should be excluded from the instrument during assembly. For this purpose it is now usual to install special ‘Clean Areas’ in which such instruments may be assembled under conditions of extreme cleanliness. The paper summarizes modern practice in the planning, design, and operation of clean areas in a manner which it is hoped will provide guidance to those having to build or operate such areas. Mention is made of ways in which the design of components and equipment can assist clean assembly and the hope is expressed that the technology of clean assembly may be put on a more rational basis by means of a scientific study of the ways in which contamination can enter and disturb instruments and mechanisms.
The Fatigue Strength of Pin-Jointed Connections in Aluminium Alloy B.S. L65
Authors: Low A. C.
Published: October 2007

The purpose of this paper is to report investigations into the improvements in fatigue strength of pin-jointed assemblies that could be obtained by the use of interference fits between pin and lug, and the effect on the strength of variations in pin diameter.

Direct-stress tension-tension-fatigue determinations were made on assemblies, consisting of an aluminium-alloy lug joined to a steel fork by means of a hardened-steel pin, using one overall size of lug, and varying first the pin size (using a constant percentage interference) and then the degrees of interference (using a constant pin size). Tests were also made on lugs fitted with interference-fit steel bushes and sliding-fit pins.

For the overall size of lug tested (2 3/4 in. X 3/4 in., pin centre 1 1/2 in. from the end) the optimum pin size was found to be 1 in. diameter, and the optimum interference on a 1-in. pin was found to be 0.007 in. Joints with such a pin had a fatigue strength at 10 million cycles of about 1/4–9 1/2 tons load as compared with 1/4–1 1/2 tons load using a sliding-fit pin. Bushed lugs gave similar results.
The High Temperature Properties of Four Wrought Steels Used in the Chemical Industry
Authors: Connolly B. J. , Boyd G.
Published: October 2007

The paper presents data on the short-time high-temperature tensile properties and creep properties of four steels which are in common use in the chemical industry, these data having been recently obtained from tests done at the Imperial Chemical Industries (I.C.I.) Creep Test Station. The steels tested were:

(1) low-carbon 1 per cent chromium-molybdenum (Cr-Mo) steel; (2) medium-carbon 1 per cent Cr-Mo steel; (3) low-carbon 3 per cent Cr-Mo steel; (4) 18/10/Mo/Ti chromium-nickel (Cr-Ni) austenitic steel.

Information is also given on the effect of long-term heating under stress on the micro-structure of the steels, and in the case of the austenitic steel the effect on the room-temperature mechanical properties is discussed. The application of the data to design, and their relation to existing specifications is also discussed.
Theoretical Assessment of the Performance Characteristics of Inward Radial Flow Turbines
Authors: Wallace F. J.
Published: October 2007

While the simple centrifugal compressor has been widely used over a considerable period of time and in a variety of applications, in particular aircraft gas turbines and aero-engine superchargers, and its behaviour is therefore reasonably well understood, the inward radial flow gas turbine has only recently begun to attract the attention of engineers. As a result, its characteristics are not understood as fully as those of the centrifugal compressor.

Inward radial flow turbines have a number of attractive features, such as robustness, cheapness, and relative immunity from thermal stresses, which render them particularly suitable, where the mass throughput and overall pressure ratio are moderate.

While the assessment of performance and flow conditions at the design point presents no very great difficulties, the evaluation of performance under conditions of reduced speed and pressure ratio, knowledge of which is essential in most applications, does not appear to have been attempted hitherto.

An analytical treatment of part-load conditions is outlined in this paper. In addition, the influence of the various design parameters on the overall characteristics is examined, and tentative suggestions are made for the best combination of these parameters for particular applications.
Large Pipeline Projects
Authors: Hartley A. C.
Published: October 2007

The James Clayton Lectures were instituted to promote the advance of knowledge in any field relating to Mechanical Engineering and I feel very honoured to have been invited by the Council to deliver a James Clayton Lecture on a subject with which I have been associated.
Management and the Engineer
Authors: Smith Ewart
Published: October 2007

I am very conscious of the honour and responsibility involved in presenting the Graham Clark Lecture, particularly as I am the first engineer to do so. These feelings are enhanced because I had the privilege of knowing Graham Clark personally, and because I greatly admired his humanism and breadth of vision. I share his belief that it is not less important to study people, and to organize them effectively for co-operative endeavour, than it is to study the material factors which affect the life of mankind and in which engineering science plays such a vital part. It is on the subject of the interrelation of the technical and human problems of modern life that I wish to talk today.

Like my precursors, I have elected to deal with a very wide theme but, I fear, without their clarity of mind or of expression. Before talking about engineers in particular, I should like to say something about the problems we face, about management in general, and about the form of education and training conducive to a high level of managerial ability. If I oversimplify, state what is obvious, or lose my way in attempting to follow byways of thought, I can only ask for your indulgence. My hope is that I may, in some respects at least, provoke controversy, for any constructive conflict of ideas may help us on the road of progress.
The Forty-Fifth Thomas Hawksley Lecture: The Transmission and Radiation of Acoustic Waves by Structures
Authors: Beranek Leo L.
Published: October 2007

Of major interest to architects, designers of vehicles, and acousticians is the control of structure-borne sound. Walls and panels are set into vibration by airborne waves or by vibrating mechanisms. The panel so excited will radiate sound and it may carry the vibrations to other panels or bodies.

In this lecture, the author will treat the problem of acoustic transmission through walls and panels in the audible frequency range. At low frequencies the panel vibrates as a plate or a stretched membrane. At higher frequencies the panel may behave as a quasiinfinite sheet. Above a particular ‘critical’ frequency, the wavelength of the bending waves in the panel will be longer than the compressional waves in air at the same frequency. The two wavelengths may be brought into coincidence provided the airborne wave impinges on the panel at an angle θ determined by

cos θ = ca/ cb

where c a and cb are the speeds of sound in the air and panel, respectively. At the coincidence angle, an airborne wave striking one side of a panel will set it into a level of vibration such that the magnitude of the airborne wave radiated from the other side may be only a few decibels below that of the incident wave. This effect will be discussed both for airborne waves impinging at individual angles of incidence and for waves at many angles of incidence simultaneously.

Measurements on plates, concrete sheets, and masonry walls will be presented and analysed. Analysis of the different types of response to airborne wave excitation will be made. Rules for the selection of simple and complex structures for buildings and vehicles will be suggested.

Means for reducing the response of structures to airborne wave and mechanical excitation include the use of damping materials in or on the structure, the introduction of discontinuities and the use of sound-absorbing blankets in the structure. Recent data on damping materials and means for utilizing them to produce maximum reduction of flexural waves will be presented. It will be shown that by proper utilization of such materials a structure-borne wave may be attenuated in a given distance by a factor of 10 or more than when utilized in a conventional manner.
Estimation of Upper Bound Loads for Extrusion and Coining Operations
Authors: Johnson W.
Published: October 2007

The pressure required for certain extrusion and coining operations may be approximately estimated from a knowledge of that required to perform the analogous operations under conditions of plane strain, and these pressures may be closely over-estimated by the use of a principle due to Hill or a Limit Theorem of Drucker, Greenberg, and Prager. Numerous examples are presented of a graphical or primarily non-analytical approach for closely over-estimating extrusion or coining loads required. The solutions presented give insight into the mechanics of certain metal-working operations and give good approximate results for problems generally solved by the lengthy numerical procedures associated with the use of slip-line fields.
Economic Design of Light-Alloy Castings
Authors: Broadbent P. A.
Published: October 2007

Light-alloy castings can already be produced to consistently close limits by well-established die-casting methods, so the post-war developments of precision moulds are of more benefit to the other non-ferrous and ferrous foundry industries. Furthermore, the special light- alloy foundry techniques, the heat treatment and other processes, and the free-cutting properties of light alloys should be related to design and costs of production.

Test-bar specifications for a number of aluminium and magnesium alloys are given, and are discussed in relation to strength and weight of castings, and also to certain features of design, and to the cost of a machined casting in cast iron and various light alloys.

High-tensile steel bolts are necessary to shear screw threads in light alloys, and results of tensile tests on inserts and fastenings are given, together with estimates of cost of each method of assembly.

Where inserts and fastenings are used, precautions to avoid galvanic action between dissimilar metals are necessary only on exposed junctions, whilst for corrosion generally, precautions are just as necessary for the common light alloys as for the common iron and steels.
The Compression of Bonded Rubber Blocks
Authors: Gent A. N. , Lindley P. B.
Published: October 2007

Experimental measurements are described of the load-deflection relations for rubber blocks having a wide range of thicknesses and varied shapes of cross-section. An approximate theoretical treatment is presented for classically small compressions of circular discs and infinitely long rectangular bars. The measured stiffnesses for small compressions are shown to be in good agreement with the theoretical predictions for a vulcanízate containing no carbon black, and, when an empirically obtained modification is made for thixotropic effects, for vulcanizates containing various quantities of carbon black. The behaviour under moderately large compressions is also examined.
Experimental Investigation into the Stress Distribution in a Band-Reinforced Pressure Vessel
Authors: Mantle K. G. , Marshall N. , Palmer P. J.
Published: October 2007

A model of a band-reinforced, cylindrical, reactor pressure vessel has been manufactured and tested. The vessel dimensions were 5 ft inside diameter by 9 ft overall length, with hemispherical ends, nominal plate thickness being 1 in. throughout. Hoop reinforcement on the barrel consisted of 3-in. wide circumferential bands, each band being built up of 13 layers of -in. strip, giving a total band thickness of 1 [Formula: see text] in. Full details of design, construction, and method of manufacture are given.

A complete experimental investigation into the stress distribution in the vessel has been carried out, using electrical resistance strain gauges, both at its design pressure of 1000 lb/in2 and also at twice this pressure. The stress distribution on the inner surface of the barrel, on the outer surface of the bands, and local to the tangent line has been measured. These results are compared with theoretical calculations.

Finally, the vessel was pressurized to destruction.

The results show that, as would be expected, the band reinforcement was not fully effective. However, the general stress level was maintained within acceptable limits, the theoretical stresses being exceeded by about 20 per cent. The bursting pressure of 3940 lb/in2 confirms the safety of the design, that is, a design factor of safety of 3·94.

It is considered that the results of the investigation fully demonstrate the safety and merits of the design.
The Response of a Loaded Hydraulic Servomechanism
Authors: Turnbull D. E.
Published: October 2007

When a hydraulic servo controls the position of a load the force required to move the load is produced by a pressure drop across the actuator. This pressure drop decreases that available to drive fluid through the control ports of the valve with the result that the speed of response is reduced.

This paper examines the effects of various types of load on the dynamic behaviour of the system for both step and sinusoidal input signals.

Analytical solutions to most of the response equations are obtained but graphical methods are occasionally used. When an inertial load is present it has been found necessary to consider the step response in the velocity-displacement or ‘phase’ plane.
Vibrations of Pre-Twisted Cantilever Blading
Authors: Carnegie William
Published: October 2007

This paper reports a study of the vibrations of pre-wisted cantilever blading. The blading is pre-twisted linearly about the centroid of its cross-section up to an angle of π/2 rad and is considered to be mounted encastré at the root. Accurate prediction of the frequencies of vibration of such blading is of considerable practical importance.

Two theoretical approaches to the problem are discussed. The first one, involving a direct solution of the equations of motion, is not made use of, although the characteristic equations are derived in an appendix for reference. The second approach is based on the application of Rayleigh's principle. For blades of uniform rectangular cross-section, frequency equations are derived for the fundamental mode of lateral motion and all the modes of torsional motion. Similar types of equation are shown to apply to aerofoil cross- section blading since direct coupling effects between bending and torsion, being extremely small, can be neglected.

Vibration tests were conducted on sets of blades of both uniform rectangular and uniform aerofoil cross-section pre-twisted between 0 and π/2 rad, the objects being to determine the frequencies and corresponding nodal patterns contained within a specified frequency band. The effect of pre-twist on the measured frequencies of the lateral, torsional, and, for the aerofoil cross-section, coupled modes of vibration is shown, with certain exceptions, to be considerable.

For the modes of motion where a theoretical solution is provided, reasonable agreement is shown to exist between the calculated and corresponding measured frequencies. Hence, the use of Rayleigh's method is justified, giving, as it does, relatively simple expressions for the natural frequencies of vibration.

The torsional frequencies of pre-twisted blades are dependent on the torsional stiffness values. Hence, a theoretical study of torsional stiffness variation with pre-twist is presented, the results obtained being confirmed experimentally by a series of simple torsion tests.
An Experimental Investigation of the Pressurized Air-Lubricated Journal Bearing in the High-Speed Range
Authors: Rieger N. F.
Published: October 2007

Experimental apparatus has been developed and used to study the friction characteristics of an externally pressurized air-lubricated journal bearing. The effects of variations in speed, load, diametral clearance, and inlet pressure have been studied over a wide range at high speeds. The experimental friction coefficients have been compared with those given by the well-known Petroff (1)† formula, and a reasonable degree of correlation has been found.

Bearing air consumption has been measured and a linear relationship between air-mass flow and inlet pressure is indicated. Curves relating load-carrying capacity to various ratios of inlet pressures are included, the applied loads being carried by hydrostatic flotation in all cases.

The bearings used were plain, cylindrical bushes of diameter in. and length in. Compressed air was admitted through three sets of radial-inlet holes around the bush circumference, pressures being adjusted to keep the shaft and bush as close to concentric as possible.
The Vibrations of Vertical Milling Machines under Test and Working Conditions
Authors: Tobias S. A.
Published: October 2007

The investigation described in this paper consists of three parts. Part I is concerned with an experimental investigation of the vibration of vertical milling machines under test conditions. It is shown that in the frequency range investigated, 6-10 000 c/s, the machine structure has five modes of vibration which responded with large amplitudes. The dynamic deflections corresponding to these are discussed and attention is drawn to certain structural weaknesses frequently encountered in vertical milling machines. Part II of the paper reports various experiments concerned with face-milling chatter. It is shown that the severity of chatter depends on the relative position of cutter and work-piece and the depth of cut. When the depth of cut exceeds a certain minimum value, the machine chatters in definite speed bands which are separated by chatter-free speeds. As the depth of cut is increased, the chatter-free speed bands contract. From this and the variation of the chatter frequency, it is concluded that the chatter observed is of the regenerative type, similar to that arising in the case of drilling and other machining processes (1), (2)†. A theoretical interpretation of the experimental results is given in Part III. Chatter behaviour of the machine is discussed with the aid of a three-dimensional stability chart. The constants required for the construction of this chart are extracted from the experimental results given in Part II. Correspondence between theory and experiments is satisfactory.
Discharge Coefficient of Small Submerged Orifices
Authors: Spikes R. H. , Pennington G. A.
Published: October 2007

This paper deals with the variation in discharge of small submerged orifices used in aero-control systems. It is shown that the effects of cavitation can be high and can cause changes of discharge coefficient greater than those associated with Reynolds number when the flow is turbulent.

The orifice length was altered and it was found that the most unstable conditions occurred when the length was half the diameter.

Further tests were carried out with inlet chamfer in order to determine the optimum angle and depth of chamfer for cavitation suppression.
Centrifugal Stresses in Turbo-Alternator Rotors
Authors: Fessler H.
Published: October 2007

The frozen stress photo-elastic technique was used to determine the peak stresses occurring in rotating discs which represented rotor sections. A large range of shapes of winding slots was tested and a simple empirical relationship was obtained from which the peak stresses at the necks of the teeth can be readily calculated. It was shown that these results are directly applicable to steel rotors.

Semicircular subslots (inward from the winding slots) and interslots (between the winding slots) reduced the peak stresses. The largest possible cooling slots with semicircular roots are recommended.

The stresses in the tips of the teeth due to the thrust of the winding-slot wedges were studied with static models in which the centrifugal force due to the windings was replaced by a tensile force. From these results recommendations were made for the least highly stressed shapes of tooth tips in rotors containing interslots.
Application of the Eccentric and True Anomalies of the Ellipse to Isometric and Axometric Projection
Authors: Trigg C. F.
Published: October 2007

The terminology of three-dimensional projection is examined and axometric projections compared. A method is introduced which enables a pictorial view to be drawn from orthographic views without using direct projections or special set-squares.
Application of Boundary Layer Theory to Explain Some Nozzle and Venturi Flow Peculiarities
Authors: Hall G. W.
Published: October 2007

The basis of a simple rational method for the analytical determination of discharge coefficients for the rounded-entrance nozzle and Venturi, covering the entire Reynolds number range, is presented. Certain experimental results, when compared with the theoretically derived curves, support the method. Tentative explanations are given, with the aid of the theory, for a number of puzzling and disturbing features arising from the results of some recent flowmeter calibrations. The analysis includes a new method of plotting the discharge coefficient against Reynolds number, which greatly facilitates the interpretation of experimental data.
Strength of Thick Cylinders Subjected to Repeated Internal Pressure
Authors: Morrison J. L. M. , Crossland B. , Parry J. S. C.
Published: October 2007

In April 1956 the authors presented to the Institution of Mechanical Engineers a paper entitled ‘Fatigue under Triaxial Stress: Development of a Testing Machine and Preliminary Results’, and in September 1956 a supplementary paper was presented at the International Conference on Fatigue of Metals. In these papers the authors reported tests carried out on cylinders made from a 2 1/2 per cent nickel-chromium-molybdenum steel, which were subjected to (up to) 10 million repetitions of internal oil pressure of (up to) 20 ton/in2. Since these papers were published a considerable amount of testing has been carried out on cylinders made from a mild steel, a 3 per cent chromium steel, an austenitic stainless steel, a light alloy, a nearly pure titanium, the nickel-chromium-molybdenum steel in a harder state, and both the nickel-chromium-molybdenum steel and the chromium steel in the nitrided condition. In addition, tests of more academic significance have been carried out on the nickel-chromium-molybdenum steel in an attempt to achieve a better understanding of the extraordinary results which have been obtained.

The present paper is concerned mainly with the presentation of results (supported, of course, by ancillary tests on each material) which are of importance in design. Points of academic interest are discussed only when they are relevant to the practical problem. To make the paper reasonably self-contained, a brief summary of the previous work has been given.
Modern Aids in the Design of Railway Bogies
Authors: Manser A. W.
Published: October 2007

The paper illustrates work carried out on motored and non-motored underground train bogies and the experiments carried out in the use of light-alloy bogies and vehicles.
Heat-Transfer Processes in Gas-Turbine Combustion Chambers
Authors: Lefebvre A. H. , Herbert M. V.
Published: October 2007

The authors of this paper have analysed the relevant heat-transfer processes occurring in gas-turbine combustion chambers and have derived a general equation for flame-tube temperatures. This equation is used to determine the effect on flame-tube temperature of changes in the operating conditions of pressure, inlet temperature, and air mass flow. Changes in aircraft flight conditions, involving simultaneous changes in all these operating variables are also considered. Experimental evidence confirming the predictions of the general equation is provided. The paper concludes with a discussion on the influence on flame-tube temperatures of combustion-chamber design.
Creep and Rupture Properties of Carbon Steels
Authors: Smith A. I. , Jenkinson E. A. , Armstrong D. J.
Published: October 2007

In earlier N.P.L. work on the strength of carbon steels at high temperatures, steels showing ‘normal’ and ‘abnormal’ creep properties were assessed from tests extending to 1000 hours. Further results on the same steels indicate that the order of merit of these particular steels is not altered in tests extending to 100 000 hours.

The rupture properties of carbon steels are reviewed in the light of the N.P.L. results and other published data. A wide range of strength properties is shown to exist. The pattern of results, however, appears reasonably consistent. At the lower end of the strength scale are almost pure irons and at the upper end are steels of moderate carbon content and not low in manganese and silicon. Heavy deoxidation with aluminium of conventional carbon steels results in lower creep and rupture properties than are observed in similar steels deoxidized with silicon; the part played by nitrogen in this effect is considered.

The rupture ductility of carbon steels is discussed and in the types covered by the N.P.L. researches, low ductility in long-time service appears unlikely.

Further work required in this field is considered and the need for long-time, low-strain creep properties of mild steels for use in nuclear power plants is emphasized.
Optimization of Heater Enthalpy Rises in Feed-Heating Trains
Authors: Weir C. D.
Published: October 2007

The author discusses the exact relationships obtained for the optimum distribution of heater enthalpy rises in a contact heater train for the simple regenerative subcritical cycle, the single reheat cycle with one and several heaters at and above the reheat point, and also for the double reheat cycle. The problem of supercritical cycles and the method of taking exact account of the influence of the feed pumps are also discussed.
Investigation into the Accuracy of Industrial Measurement of Sizes between 0.02 Inch and 5 Inches
Authors:   Industrial Administration and Engineering Production Group, Harrison P. W.
Published: October 2007

The system of limits and fits introduced by the ISA, covering the size range 0.04 in. up to 5 in., is now being revised by the International Organization for Standardization and will include an enlarged section on measuring instruments because of their much wider adoption since the system was introduced in 1941. The British Standards Institution, who have been taking part in this revision, asked the National Physical Laboratory to investigate the current accuracy of industrial measurements in this size range. Work-pieces were therefore circulated to forty firms whose measurements were compared with those made at the N.P.L. The algebraic mean error of these measurements at different diameters, although having a distinctive pattern, was small in relation to the spread of individual errors about this mean. Errors on external measurements were less than those on internal measurements, and the report discusses this and other characteristics in relation to the techniques of measurement used. Some optimism is apparent in the estimates of accuracy made by the participating firms. The results of this investigation are linked with those of an earlier investigation covering the size range 4 to 80 in.
Blaenau Ffestiniog and other Medium-Head Pumped Storage Schemes in Great Britain
Authors: Headland H.
Published: October 2007

The lecture deals briefly with:

(1) The general features and the mechanical aspects of the 300-MW Blaenau Ffestiniog Pumped Storage Scheme, which will be commissioned in 1961. This station is conventional in layout but nevertheless the vertical arrangement of the four 75-MW machines and other design considerations introduced some interesting and unusual problems. (2) Recent developments in Great Britain where high output reversible pump-turbines for 600-1200 ft head are contemplated. Problems associated with design and performance of this type of machine are mentioned, together with those of a more general character for coastal pumped storage schemes using sea-water, which introduce fresh civil engineering questions. These are interrelated with agricultural and maritime interests and more specialized problems such as the performance of plant and steel structures exposed to wave action, salt-water corrosion, resistance of concrete to high velocities, cavitation, and possibly marine growths.
The Influence of Rate of Strain-Hardening in Machining
Authors:   Industrial Administration and Engineering Production Group, Oxley P. L. B. , Humphreys A. G. , Larizadeh A.
Published: October 2007

In order to determine the influence of the rate of strain-hardening (that is, rate of increase of flow stress with straining) on the machining process, cutting tests were carried out on a material with a high rate of strain-hardening and on a material with a relatively low rate of strain-hardening. All external parameters of the process such as cutting force, chip thickness ratio, angle of tool-chip interface friction etc., were measured and a slip-line analysis of the plastic zone was made using strain-hardening slip-line theory. It was found that although externally the process was virtually the same for each material the plastic zones were distinctly different. The relation between the stress distribution in the plastic zone and an independently obtained stress-strain curve of the machined material was clearly shown. Finally new suggestions were made regarding the nature of the tool-chip interface contact.
Control of Water Level in Marine Boilers during Rapid Changes of Load
Authors:   Steam Plant Group, Morton A. J.
Published: October 2007

Conditions in a boiler and steam range during manoeuvring are analysed in order to identify the factors affecting boiler water level, making reference to the Y.E.A.D.1† naval boiler whose behaviour was closely observed during recent shore trials. It is shown that a boiler steaming alone responds to control actions and load changes quite differently from a boiler steaming in parallel with others. A simple theory is developed and used to establish the characteristics ideally required of a feed regulator, and this leads to the conception of a regulator incorporating an unusual type of steam flow element.

Comparative estimates of the performance of this regulator and others of conventional design, applied to the Y.E.A.D.1 boiler, indicate that the proposed modification would be very beneficial, but that a conventional two-element regulator is likely to give a poorer performance than simpler types dependent upon water level only. It also appears that feed regulation is easiest when the boiler is steaming in the region of half load.

Common design and commissioning procedures are criticized and gaps in knowledge pointed out.
Behaviour of Metallic Thick-Walled Cylindrical Vessels or Tubes Subject to High Internal or External Pressures at Elevated Temperatures
Authors:   Applied Mechanics Group, Johnson A. E. , Henderson J. , Khan B.
Published: October 2007

An analysis of the stresses and strains in a thick-walled cylinder, under internal and external pressure giving rise to purely elastic strain, was made initially by Lamé (1)† and subsequently several authors have dealt with the same problem.

An analysis of stress and strain in similar cylinders at elevated temperatures, in which creep strain was regarded as being of major importance and the elastic strain of relatively trivial significance, was made by Bailey (2). This analysis has been much used by engineering designers.

However, in practice cylindrical pressure vessels or thick-walled tubes may be subject at elevated temperatures to internal and external pressures in such circumstances that, over the whole or a considerable portion of the intended life of the structure, creep strains and elastic strains are both of significant order.

Accordingly, it is obviously of practical importance that an analysis be made of the changes of distribution of stress and strain or strain rate with time, in such cases, and the current paper is directed towards this end.

In the first portion of the paper, theoretical relations between stress, strain rate and time are derived, and in the second portion the application of these relations to a number of metallic alloys at temperatures within their practical working ranges is examined.

A complete example of this application is worked out in detail for one material and temperature, as an aid to designers who may wish to use the methods described.

It is to be emphasized that this work has become possible in view of the very considerable information regarding the complex stress-creep strain-time relations of a variety of engineering materials at elevated temperatures gained in the previous work of the authors.
Discontinuity Effects at the Junction of a Pressurized Cylinder and End Bulkhead
Authors:   Applied Mechanics Group, Houghton D. S. , Chan A. S. L.
Published: October 2007

An analysis is made to assess the forces and moments arising at the junction of a pressurized circular cylindrical shell and end bulkhead which forms part of a hollow sphere. Expressions are developed for the stress distributions for two cases:

(1) When the end bulkhead is joined rigidly and directly to the cylinder. (2) When a jointing ring is introduced at the junction. The necessary and sufficient geometric conditions for the existence of pure membrane stress in the structure are then examined.
A Novel Anti-Seizure Surface Treatment: Diamond Impregnation
Authors:   Lubrication and Wear Group, Wells James
Published: October 2007

Tests of an exploratory nature into a novel process, which improved the load-carrying capacity of sliding surfaces and significantly reduced friction, are described

Particles of a hard material, for example, diamond, were impregnated into the sliding surface, the projecting sharp edges being subsequently removed to leave numerous small pads of diamond above the surface. The experimental programme was limited mainly to bronze sliding on hardened steel and lubricated with aviation paraffin, but a few tests under conditions of high Hertz stress (hard steel sliding on hard steel) and synthetic-oil lubrication showed similar, beneficial effects. Only the hardened steel was impregnated in the bronze on steel tests

Endurance running of the impregnated surface (bronze on steel lubricated with fuel) at loads up to 300 per cent of the failing load of a conventionally lapped surface was satisfactorily performed with coefficients of friction of the order of 0.001. Excellent repeatability of control tests was obtained

Silicon carbide was shown to be a suitable substitute for diamond

One instance of impregnation of the surfaces within a fuel pump with a subsequent reduction in wear rate is also described
Digital Computer Programmes for Steam Cycle Analysis
Authors:   Steam Plant Group, Turton P. J.
Published: October 2007

Much of the published data on steam cycles cannot be applied to modern power stations owing to the advanced steam conditions and complex cycles now used. Plant optimization therefore requires the detailed analysis of a large number of cycles over a wide range of steam conditions

Modern high-speed digital computers offer the engineer relief from the tedium of lengthy calculations and the uncertainty of broad simplifying assumptions. The Ferranti ‘Mercury’ computer is used in the present work and, for economy in computing time, separate boiler and turbine programmes are written and the results combined through a short desk calculation

The turbine programme, which is applicable to both conventional and nuclear stations, is sufficiently general to deal with all anticipated steam conditions and cycle arrangements and it also takes account of minor cycle corrections. Possible variations in boiler design, however, make a similarly general treatment more difficult and several separate programmes are described here, each dealing with a steam cycle and boiler design suitable for use with the low-temperature gas-cooled reactors being built in Britain at present

Application of the programmes to the design optimization of a complete nuclear power station is discussed
Gear-Tooth Contact Phenomena
Authors: Merritt H. E.
Published: October 2007

Current methods of assessing gear-tooth load carrying capacity remain largely empirical; so also is lubrication technique. There is need for more research and more endeavour to apply it. The lecture states the quantities, definitions and notation employed in the analysis of contact conditions; outlines the phenomena of oil-film formation and friction; gives experimental values obtained by disc machines; and develops a modified treatment of temperature calculation. Phenomena encountered in practice are summarized, and the conclusion is reached that scuffing begins not within the oil film but by dislocation of the bounding surfaces. The emphasis throughout is on the problems which still await solution
Maintenance Experience of the Calder Reactors
Authors:   Nuclear Energy Group, Treharne J. R.
Published: October 2007

This paper draws on experience gained during the 14 years of operating experience at the Calder Hall nuclear power station, and describes the problems encountered in maintaining the plant and the reasons for, and effects of, restrictions imposed because of their special features
Interferometry Applied to the Study of Elastic Flexure
Authors:   Applied Mechanics Group, Duncan J. P.
Published: October 2007

This paper describes briefly techniques for the rapid preparation of optically flat metal plates to an accuracy of approximately two interference bands over an 8-in. span. The construction and use of two large Fizeau interferometers for observing defections resulting from flexure is described

The technique was developed 'as an experimental means of circumventing the very great theoretical complexity of analysing various forms of flexed multiply-connected plate occurring in engineering construction. It is illustrated qualitatively from studies of perforated circular plates subjected to lateral loading, of annular and triangular plates subjected to concentrated loads and of perforated bars subjected to pure bending

Quantitative studies based on the method are to be described in subsequent papers
Gridwork Rigidity Determined by Interferometry
Authors:   Applied Mechanics Group, Duncan J. P. , Michejda O.
Published: October 2007

An experimental method based on optical interferometry is applied to find the deflected shape of gridworks subjected to lateral loads

These experimental results are compared with results obtained by moment distribution calculations and by the use of the equivalent elastic constants of Horvay and Malkin

The technique itself, which has been developed by one of the authors as a general experimental method of studying the flexure of thin elastic plates, has been described in the accompanying paper
Pulverized-Fuel Ash Disposal
Authors:   Steam Plant Group, Dawson S. H. , Dunkley W. H.
Published: October 2007

The paper reviews the development of practice in Great Britain of the extraction, handling) and disposal of ash from pulverized fuel boilers—other than slag-tap boilers