bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Shear in Transverse Impact on Beams
Authors: Christopherson D. G.
Published: October 2007

In this paper the problem of transverse impact on a uniform beam is considered theoretically. Two examples which can be taken as representing a wide range of impacts which occur in practice are referred to particularly: (1) the beam struck transversely by a uniform square-ended rod travelling perpendicularly to it; (2) the same problem for the striker having a spherical end.

In these examples it is shown that the ability of the beam to deflect in shear as well as in bending plays a dominant part in what takes place, and that, as far as the force between striker and beam is concerned, the length of the beam is usually without importance, as there is not time during the impact for an elastic wave to travel to the ends of the beam and return.

It is shown that in regard to example (2) the theory presented is in good agreement with Arnold's experimental results obtained some years previously, and curves are given from which the maximum force between beam and striker can be obtained in terms of three parameters, representing respectively the velocity, the mass, and the radius of the striker, each dependent on the ratio of shear stiffness to bending stiffness for the beam.
Principles of Continuous Gauge Control in Sheet and Strip Rolling
Authors: Hessenberg W. C. F. , Sims R. B.
Published: October 2007

The problem of longitudinal gauge variations in hot- and cold-rolled sheet and strip metal is considered. It is suggested that they are caused mainly by elastic distortions of the mill in response to variations in the separating force between the rolls. A unique relation is shown to exist between the roll force and the thickness of the strip leaving the rolls, and this forms the basis of two new methods of continuous automatic control of gauge. These methods are independent of direct measurement of the thickness of the sheet or strip during rolling. They employ an electrical roll-force measuring element the output of which, after suitable modification, continuously adjusts either the position of the rolls or the tension applied to the strip, so that a substantially constant thickness is maintained in the rolled material. Some preliminary experiments on a 10 inches by 10 inches two-high mill have demonstrated that these methods of control are correct in principle.
Control of Boilers Fired by Solid Fuels in Suspension
Authors: Young Llewellyn
Published: October 2007

In this paper are discussed those characteristics of boiler design and performance which have favoured the parallel development of automatic control of boiler auxiliaries.

Consideration is given to those temporary conditions which arise during periods of load change, and which, if not accurately estimated and followed by the necessary corrective action, may lead to over-regulation of firing rate or feed-water supply. Instruments are provided to determine and inform the operator of the necessary action to be taken, and manual remote-control eliminates the laborious duties of routine readjustments necessary to maintain efficiency. In this field automatic control has many advantages and is quicker and more accurate in response than the human operator.

The theory of elementary forms of automatic control devices is dealt with simply, and the mechanical means, employing pneumatically operated devices, by which these theoretical requirements are met are described. Examples are given of the use of standard apparatus in building up a composite control system, and the more complicated installations of boilers fired by spreader stokers, pulverized fuel and cyclone furnaces are dealt with.
Characteristics of a Spinning-disk Liquid Sprayer
Authors: Boshoff W. H.
Published: October 2007

In this paper is described an attempt to increase the output of a spinning-disk sprayer without sacrificing the homogeneous drop-size characteristics found by previous investigators. A disk sprayer inches in diameter was designed, and the characteristics were determined by feeding various quantities of water centrally on to the disk, and noting the resulting drop sizes and their distribution over a range of disk speeds from 600 to 2,000 r.p.m.

The critical flow rate for the production of uniform-size drops is in the range 6–22 cu. cm. per sec., and the size of drops produced is inversely proportional to the speed of the disk. The product of drop diameter and peripheral velocity of the disk is approximately constant and varies with the smoothness of the surface of the disk rather than with the rate of liquid flow.

Above the critical flow rate the homogeneity of the drops disappears and a wider range of sizes is observed. The distribution and sizes of the drops are independent of the rate of liquid feed over a range of from 22 to 110 cu. cm. per sec, the size of the majority of drops being dependent on the peripheral speed of the disk. Above that range the liquid comes off the disk in a sheet, in which little or no break-up of the liquid takes place.

It is concluded that spinning disks of large diameter will produce drops of uniform size even at relatively low rotational speeds.
Part II. Research on the Performance of a Type of Internally Air-cooled Turbine Blade
Authors: Ainley D. G.
Published: October 2007

A comprehensive series of tests have been made on an experimental single-stage turbine to determine the cooling characteristics and the overall stage performance of a set of air-cooled turbine blades. These blades, which are described fully in Part I of this paper had, internally, a multiplicity of passages of small diameter along which cool air was passed through the whole length of the blade. Analysis of the, test data indicated that, when a quantity of cooling air amounting to 2 per cent, by weight, of the total gas-flow through the turbine is fed to the row of rotor blades, an increase in gas temperature of about 270 deg. C. (518 deg. F.) should be permissible above the maximum allowable value for a row of uncooled blades made from the same material.

The degree of cooling achieved throughout each blade was far from uniform and large thermal stresses must result. It appears, however, that the consequences of this are not highly detrimental to the performance of the present type of blading, it being demonstrated that the main effect of the induced thermal stress is apparently to transfer the major tensile stresses to the cooler (and hence stronger) regions of the blade.

The results obtained from the present investigations do not represent a limit to the potentialities of internal air-cooling, but form merely a first exploratory step. At the same time the practical feasibility of air cooling is made apparent, and advances up to the present are undoubtedly encouraging.
The Synthesis of Two Marine Water-tube Boilers
Authors: Baker L.
Published: October 2007

In this paper a brief résumé is given of the important lessons learnt from the operation of oil-fired water-tube boilers at sea since 1925. These are linked with the shipowners' requirements—particularly those pertaining to the post-war merchant service—and the development of two designs of boiler from these requirements is shown. In this way it is possible to accept fundamentally different designs of boiler for application in the same ship.
Main Propulsion Gas-turbine Set for the Oil Tanker Auris
Authors: Forsling B. E. G.
Published: October 2007

In order to obtain operating experience with a main propulsion gas turbine under service conditions at sea, the Diesel electric oil tanker Auris has been equipped with a gas-turbine set which replaces one of the four Diesel engines originally installed.

A description is given of the set which operates on the simple open cycle with a heat exchanger and independent (low pressure) power turbine. The set thus has one compressor and two turbines in series, the high-pressure turbine driving the compressor and the low-pressure turbine driving the alternator which supplies power to the propeller motor.

In the design the emphasis was laid on high component efficiencies which necessitated the use of multi-stage uncooled turbines. A moderately high initial gas-temperature was adopted in order to ensure adequate length of life.

The experience during test operation, which covered a running time of 680 hours, is fully recorded, and complete performance figures for all conditions are given.

The set was operated with some success on heavy (residual) fuel oil. The total running time on heavy fuel oil was 363 hours, which included a continuous run of 270 hours, mainly at full load.
On the Graphical Solution of Transient Vibration Problems
Authors: Bishop R. E. D.
Published: October 2007

Phase-plane methods have been used with great success in the theory of non-linear mechanics. They have also been applied to a different class of problems; viz. to dynamical systems with transient loading. The paper concerns this second use of the plane and some recent extensions of it.

A survey is made of the literature covering the twenty years since these constructions were introduced. This relates to: (1) the transient disturbance of single-degree-of-freedom systems (which may include damping, non-linearity, hysteresis, etc.) and of multi-degree-of-freedom systems; (2) the deflexions of beam columns in the theory of elastic stability; and (3) Jacobsen's general method of graphical integration.

Some new additions to the theory are given. These are: (1) a method of graphical differentiation; (2) a simplified approach to multi-degree-of-freedom systems leading to the treatment of transient loading of beams by moving and moving-and-varying loads (damping may be contemplated in these beam problems and the method that is devised easily carries over to certain plate problems); and (3) a demonstration that the graphical method can be used for deflexions—as well as bending moments —in the theory of beam columns.

It is suggested that these constructions are of real importance, not only for practical engineering problems, but also for teaching purposes.
The Vibration of Rectangular Plates
Authors: Warburton G. B.
Published: October 2007

In this paper are considered the free transverse vibrations of rectangular plates with all possible boundary conditions obtained by combining free, freely-supported, and fixed edges. The Rayleigh method, assuming waveforms similar to those of beams, is used to derive a simple approximate frequency expression for all modes of vibration. The terms in this expression depend on the nodal pattern and the boundary conditions; they are tabulated for fifteen boundary conditions—all four edges free, freely-supported, or fixed and the twelve cases in which some of the edges have one condition and the rest another. The expression can also be used to obtain frequencies for a plate which has a combination of all three boundary conditions. The effect on frequency of an edge being supported and partially restrained is discussed.

For some boundary conditions it is possible to compare derived frequencies with those obtained by various methods of accurate analysis and by experiment; except for a few cases, the results from the approximate expression and accurate analysis agree closely.

For rectangular plates and for most boundary conditions and modes of square plates, the nodal pattern consists of lines approximately parallel to the sides of the plate. The exceptions are discussed and the gradual transition from these non-parallel patterns characteristic of a square plate to those of a rectangular plate is traced.

The frequencies of extensional vibrations of rectangular plates are derived for two boundary conditions.
The New British Standard for Engineering Drawing Practice
Authors: Abbott W.
Published: October 2007

The new British Standard No. 308 is a comprehensive work which should go far to bring unity to drawing procedure. The standard has been long in preparation and at various stages in its compilation has been presented to British industry for comments. It has been discussed internationally, and particularly in American and Canadian committees, which have been giving considerable study to the same subject; the object has been that of reaching a common international understanding of the fundamental principles involved. In preparing the standard, reference has been made to the ‘Dimensional Analysis of Engineering Designs’, an important contribution to the subject published by H.M. Stationery Office in 1948.

Recommendations of the standard fall into two main groups: those which relate to general practice, and those which deal with dimensioning and tolerancing.
Air Flow in a Naturally Aspirated Two-stroke Engine
Authors: Wallace F. J. , Nassif M. H.
Published: October 2007

The problem of scavenging of naturally aspirated, two-stroke cycle engines by utilization of wave effects in the exhaust and induction system is treated theoretically and investigated experimentally by systematic variation of the exhaust and induction system, as well as engine speed.

In the theoretical treatment accuracy is achieved with a minimum of numerical computation by the adoption of the theory of waves of finite amplitude and the use of charts, wherever possible. These two features constitute the most significant departure from List's very thorough analysis (List 1949/50)‡, which is based throughout on the small-wave theory and in which little attention appears to have been paid to the simplification of numerical work.

The theoretical section is divided into two parts dealing with (1) the analysis of cyclical pressure fluctuations in the engine cylinder and pipe system, and (2) the treatment of the gas-exchange process in the cylinder on the basis of ‘perfect mixing’ and the derivation of the conditions for dynamic similarity.

A novel experimental technique is used, air from an external compressor being admitted to the cylinder of the motored engine through a rotary valve. In this manner release pressures comparable with those obtaining in the firing engine are attained, while the effects of high temperatures, which are of secondary importance in relation to wave phenomena, are eliminated.

The experimental work is divided into two parts: (1) tests corroborating the wave theory; and (2) systematic air-consumption trials with variable induction-pipe lengths and exhaust systems, incorporating ( a) plain pipes, ( b) an exhaust ejector similar to that described in the Kadenacy patent specifications, ( c) an expansion chamber, and ( d) a diffuser.

The general conclusions are: (1) good agreement between observations and analytical results is obtained, (2) high air-consumption is possible with natural aspiration provided that effective use is made of wave action by correctly designed exhaust and inlet systems; and (3) satisfactory scavenging is only achieved if not only the external pipe system but also the engine speed and geometry conform to certain requirements conveniently expressed in the form of dimensionless groups.
Nodular Cast Iron—its Present Position and Future Prospects as an Engineering Material, with Special Reference to its Suitability for Crankshafts
Authors: Bailey S. B.
Published: October 2007

The historical development of iron having graphite present in the nodular form as cast, is traced from the patent application by Morrogh and the British Cast Iron Research Association (1946)† to its selection as a crankshaft material by the Ford Motor Co. in 1952. The economics of the production of nodular iron by various methods is discussed and it is concluded that material produced by the magnesium-nickel process now in use cannot compete in price with established materials such as carbon steel and malleable iron. Methods for direct addition of magnesium to molten iron are described, and it is concluded that application of these methods to low-sulphur irons from basic cupolas may completely alter the situation.

The engineering properties of nodular cast iron are compared with those of other ferrous metals. It is concluded that nodular irons in the as-cast condition may be used instead of high grade flake-graphite irons for components not subject to shock loading, and instead of malleable irons in applications where 2–4 per cent elongation at fracture is adequate. The annealed nodular cast irons may be used, where their extra ductility and impact resistance are considered essential, to replace malleable irons and cast or forged carbon-steels. Their chief advantage over malleable irons lies in the shorter heat-treatment they require, which becomes economically more important as the size of a casting increases and as its selling price per lb. falls. As a replacement for carbon steel, nodular cast iron will be attractive for components which are difficult to cast or which require high surface-hardness with medium strength and impact resistance. However, the extent to which nodular cast iron replaces any of these materials will be determined largely by the price at which it can be produced; this will have to be decreased very considerably before it becomes competitive. Ultimate output of nodular cast iron in Britain in peace time is likely to be limited by the high cost of the low-phosphorus ore which is necessary for its production; in war time, its output might be severely restricted by the difficulty in importing this ore.

The particular application of nodular cast iron to crankshafts is discussed in detail. It can replace alloy flake-graphite irons with a gain in ductility and impact resistance, and is already replacing graphitic cast steel, chiefly because of its better founding properties, and because its lower pouring-temperature facilitates the use of mass-produced shell moulds. It seems doubtful whether its fatigue properties will permit of its replacing the forged low-alloy steel which is used for most British automobile crankshafts, unless some reduction in engine specific-power output is accepted.
Exhaust Arrangements and Their Influence on the Power Output of Internal-combustion Engines
Authors: Williams T. J.
Published: October 2007

This paper was read before a meeting of the South Wales Branch Graduates' Section, Institution of Mechanical Engineers, on 24th February 1953, and was awarded a Viscount Weir Prize.
Wave-Action in Gases: The Attenuation and Reflection of Compression Waves Propagated in Pipes
Authors: Mucklow G. F. , Wilson A. J.
Published: October 2007

The investigation supplements a previous examination (Bannister and Mucklow 1948)‡ of the wave-action following sudden discharge of compressed gas into pipes. The paper consists of two parts, Part I dealing with the relation between the frictional attenuation of compression waves propagated in pipes and the effects of friction under conditions of steady flow. The object of the work covered in Part II was to compare experimentally the pressure amplitude of compression waves before and after closed-end and open-end reflection, with a view to verifying considerations based on theoretical argument.

The apparatus consisted of a series of cylinders of 1.5, 2.0, and 4.285 inches bore, from which compressed air was discharged suddenly into pipes of varying length and of the same bore as the cylinder in use. Indicator diagrams were recorded at suitable intervals along the pipes.

Theoretical considerations show that, with the same particle velocity, a simple relation exists between the rate of decay of small-amplitude waves and the steady-flow pressure-drop along a pipe. Experiment suggests that this relation applies approximately to finite-amplitude waves and, on this basis, a simple expression is devised to relate wave-head decay with initial amplitude, pipe diameter, and distance propagated, within the range considered. By use of this expression, the mean velocity of propagation may also be determined.

The processes of open- and closed-end reflection of compression waves are examined and considerations outlined in an appendix to the previous paper are amplified. The resulting conclusions are supported by experimental evidence. The effects of discharge through a constriction are considered in the Appendix.
Dynamic Stresses in Electric Overhead Travelling Cranes Due to the Hoisting and Lowering of Loads
Authors: Lightfoot E. , Clarkson B. L.
Published: October 2007

The paper describes a series of tests which were carried out on three lattice-type electric overhead travelling (E.O.T.) cranes to determine the impulsive effects due to the sudden hoisting and lowering of loads. Dynamic strains were measured from electric-resistance strain-gauge recordings taken during the tests. The stresses computed from these strains are compared with values from a complete theoretical analysis and with values obtained from three approximate formulae. Finally, a method is proposed for the evaluation of the dynamic factor in design.
Effect of Small Modifications on Engine-propeller Vibration Characteristics
Authors: Head J. W.
Published: October 2007

In 1945, Morris† gave an analytical method for the determination of coupled engine torsional and propeller flexural vibrations, in which account was taken of blade section, blade twist, hub moment of inertia, pitch-setting angle, and speed of rotation. A particular case involved mathematically the determination of the latent roots and their associated modes for a symmetrical square matrix of the twelfth order, and in 1942 the necessary calculation took about three months. Here it is shown that, given the latent roots and their associated modes for one such case, the corresponding latent roots and modes for a similar case (in which the ‘deflexion coefficients’ are changed by arbitrary but small amounts) can be deduced explicitly, so that the additional calculation for each case after the first requires only a day or two. Extension to the case where the changes are not small is tentatively considered.

The results here given are derived by the ‘Escalator’ method; they could be applied to a wide range of problems concerning oscillations and vibrations.
The Roll-setting Method of Automatic Control of Gauge in Hot and Cold Rolling Mills
Authors: Sims R. B. , Slack K. H.
Published: October 2007

When strip is rolled at a constant speed, errors in the finished thickness occur owing to changes in width, hardness, and thickness of the incoming material, in tensions applied to it, and to variations in friction in the roll gap. The gauge of strip may also vary when the mill speed is changed.

A closed-loop regulator had been constructed to demonstrate, on a pilot-plant scale, a method of automatically controlling the gauge of sheet and strip rolled in hot and cold mills. A measure of the departure from gauge is obtained from simultaneous measurements of roll-load and the roll-setting, and correction is made by varying the position of the rolls. The controller is described together with experiments which demonstrate that the method is capable of consistent rolling to close tolerances in gauge.
Cylindrical Pressure Vessels: Stress Systems in Plain Cylindrical Shells and in Plain and Pierced Drumheads
Authors: Carlson W. B. , McKean J. D.
Published: October 2007

This paper is limited in its scope to three specific aspects of pressure vessel stressing:—

(1) The presentation of experimental evidence that stresses arising from out-of-circularity in shells may be calculated by the method of Haigh Welding Research Committee (1936)‡, and deductions from this fact.

(2) The presentation of the results of plain drumhead stress range calculations carried out by the ‘beam-on-elastic-foundation’ method of Wells (1950); experimental corroboration and deductions therefrom.

(3) Some notes on manhole drumhead stressing and reinforcement.

The first of these aspects has reached a fairly acceptable degree of finality. The second has been carried a stage forward but it calls for discussion and the pooling of further data. The work on manhole drumhead stressing and reinforcement is continuing, and the present paper must be regarded as an interim statement in that respect.
The Analysis of Vibrating Systems Which Embody Beams in Flexure
Authors: Bishop R. E. D.
Published: October 2007

When an oscillatory system embodies uniform beams in flexure, as for instance in frames, the receptance method probably offers the most convenient means of analysing free and forced motion. The theory is given in detail and tables of receptance functions are presented. The use of these is explained by means of examples, and numerical work is made convenient by a table of functions.
Friction of Steel Slabs on a Roller Table under Varying Physical Conditions
Authors: Dean S. K. , Kilburn M. A.
Published: October 2007

A knowledge of the coefficient of friction between steel slabs and the surfaces of rollers is important for the design and operation of roller tables in steelworks, and values were determined from acceleration tests on a model roller table. When cold the effective coefficient of friction was greater with a light slab than with a heavy slab, and was greater with low roller speeds than with high roller speeds. The effective coefficient of friction was independent of slab temperature in the range 700–1,100 deg. C. (1,290–2,010 deg. F.), and with hot slabs it was affected less by slab weight and roller speed. When the slip between the rollers and the slab became small, the effective coefficient of friction decreased with cold slabs and increased with hot slabs. The mean value with cold slabs was 0.20 and with hot slabs it was 0.29. Grit-blasting the slab surface increased the value by about 5 per cent and with heavily oxidized slabs the value was about 10 per cent greater. Adding powdered mill scale and water to the rollers increased the value with hot slabs by about 20 per cent but not with cold slabs. Some observations in a steelworks support the results.
Water-Ring Self-Priming Pumps
Authors: Crewdson E.
Published: October 2007

The method of operation of water-ring self-priming pumps is briefly described, with performance data of three designs of such pump. The mechanism by which these pumps produce their effect is discussed, and the conclusions reached indicate that it is impossible to anticipate their performance from their physical dimensions as can be done with a centrifugal pump. If, however, the head-discharge curve of any pump is established, and the horsepower required to overcome mechanical and disk friction is known or can be closely estimated, the horsepower taken by the pump at any point of its range can be calculated with a high degree of accuracy. Amongst the information included are graphs of air-pumping capacity and details of experiments to determine the best designs of rotor vane. Small changes in the shape of the vanes produce remarkable differences in performance.
Oil Flow and Film Extent in Complete Journal Bearings
Authors: Cole J. A. , Hughes C. J.
Published: October 2007

In 360-deg. journal-bearing theory, the load-carrying film is assumed to be partial as a result of cavitation in the diverging outlet film, but the friction-producing film is taken as complete. The effect of oil inlet conditions on film extent and the state of affairs prevailing in the cavitated film have been matters for speculation. A method has been developed for photographing the oil film in glass bearings of standard clearance ratio (0·001 and 0·002) and the results of a qualitative and quantitative examination of film extent are described. The measured oil outflow rates are analysed by separation into the hydrodynamic and supply-pressure-induced components, and explanations for an apparent deficit in the former are discussed.
The Hydrodynamic Pocket Thrust-Bearing
Authors: Kettleborough C. F.
Published: October 2007

Wilcock (1955)† describes a thrust bearing in which the power loss is very much less than that of the existing conventional thrust bearings. This bearing consists of a stepped oil film with side lands to restrict side leakage, and a pocket of large depth over which the friction is negligible. The analysis described, although allowing for side leakage, is not very exact.

Kettleborough (1955) has described an electrolytic tank investigation into stepped thrust-bearings. The method has been modified for the bearing under discussion and operating characteristics have been calculated.

The results are compared with those for the tilting-pad bearing and stepped bearing and verify that the latter is superior to the others so far as hydrodynamic performance is concerned.
Testing of Boilers and Turbo-Alternators in Power Stations of the Central Electricity Authority
Authors: Horsman H. S.
Published: October 2007

The paper refers to the seven years' period following the nationlaization of electricity supply. The various reasons for plant testing are stated but such work is never an end in itself.

The average heat rates for 33 sets each of 30 MW. and 30 sets each of 60 MW. are stated, together with their standard deviations. Heat rates as low as 7,800 B.Th.U. per kW.-hr. may be achieved in the foreseeable future.

In the seven-year period 77 per cent of new sets were tested, which yields a fair cross-section of the performance of the installed plant. It is the intention to introduce a system of routine testing for the more important machines. In dealing with the subject of boiler tests, available methods are reviewed and consideration is given to recent simplifications of the deferred efficiency test as agreed with the Watertube Boilermakers' Association (W.T.B.A.).

A table of average boiler losses for stoker and for pulverized-fuel firing is presented and from this reliable estimates of boiler performance can be deduced so as to allow for several variables which could affect the answer.

Water flow enters into the testing of both boilers and turbines. The paper refers to standardization of flow metering in the Central Electricity Authority (C.E.A.) and states that five hydraulic calibrating laboratories are being constructed. The Authority is constantly investigating improved means of flow measurement and hopes thereby to contribute to an improvement in technique.

With regard to electrical metering, and in view of the proposal to introduce routine turbine testing, meters should be of the highest quality. N.P.L. certificates have been obtained for a super grade of instrument and results are set out in tabular form. The paper ends by a foreshadow of some possible improvements in electrical integrators.
The Influence of Free-Stream Turbulence on Heat Transfer by Convection from an Isolated Region of a Plane Surface in Parallel Air Flow
Authors: Edwards A. , Furber B. N.
Published: October 2007

The object of the experiments was to investigate the influence of free-stream turbulence, which it was considered had been overlooked as one of the variables in the field of heat transfer by forced convection from a plane surface.

In order to cover a suitable range of Reynolds number, and to avoid the complication of laminar, transition, and turbulent boundary layers existing simultaneously over the transferring region, an isolated arrangement was used. The influence of a square nose on the plate, with no turbulence grid fitted in the tunnel, was also investigated.

The results are given in Fig. 5 in the form of Nusselt number against Reynolds number.

The mean heat-transfer coefficient has been corrected for conduction (edge) and radiation losses.
Tension and Torsion Properties of Some Metals under Repeated Dynamic Loading (Impact)
Authors: Taylor D. B. C. , Tadros A. Z.
Published: October 2007

Two new machines for the testing of metals to fracture under repeated dynamic loading in both tension and torsion are described. These machines are of the ‘falling weight’ type, the yield stress (or yield torque) being measured electronically and the total extension (or total twist) during a particular loading cycle being limited to any desired value.

A preliminary series of tests in both dynamic tension and dynamic torsion, using solid cylindrical bar specimens of 3/8 inch diameter, was carried out on a medium-carbon steel, a mild steel, a silico-manganese spring steel, and two aluminium alloys. For tension, the average time from zero stress to the dynamic yield stress was in the range 0·18-1·00 milliseconds and, for torsion, 0·65-2·67 milliseconds from zero torque to the dynamic yield torque.

In straining specimens to fracture under such repeated dynamic loading, the yield point was found to vary in a manner similar to that for static loading, though all dynamic yield points showed a progressive increase in value with reduction in loading time.

For equal loading times, a greater percentage increase in yield point value was noted for the medium-carbon steel and the mild steel under dynamic torsion as compared with dynamic tension, thus indicating a migration of the criterion of failure away from the Mises-Hencky theory towards the theory of maximum principal stress.
The American System of Education and Training of Mechanical Engineers
Authors: Arms H. S.
Published: October 2007

A very brief review is made of the American system of education and training of mechanical engineers and some of its salient features at the present time are contrasted with the British system. Points of particular interest are the emphasis being placed on the scientific foundations of the subject with a corresponding lack of emphasis on present practice by the colleges, an attempt to produce a more cultured graduate, and a rapid growth of postgraduate education. Points of particular contrast are the small number of engineers who ever undergo apprentice training, and the system of recognition by State boards rather than by the Engineering Institutions.

A short illustration is given of the cost of a university education to the student.
Examination of the Theories for Calculating the Stresses in Pipe Bends Subjected to in-Plane Bending
Authors: Turner C. E. , Ford Hugh
Published: October 2007

Much theoretical and experimental work has been published on the flexure of pipe bends. Examination of the results to date show considerable differences between certain measured results and the predicted behaviour.

The theoretical works relate mainly to long radius bends and all make many simplifying assumptions.

This paper presents a more detailed theoretical study, for bending in the plane of the pipe bend. Examination of both typical and extreme cases and a comparison with the experimental evidence shows which of the various theoretical simplifications can be accepted for a given pipe bend.

It is concluded that although complete stress distributions calculated by previous theories may be seriously in error over particular ranges of the variables, the peak stresses and flexibilities are, by a combination of circumstances, unlikely to be more than 5-10 per cent in error if certain factors introduced in the more recent of these theories are used.

Manufacturing and other variations between nominally similar pipe bends, however, seem to preclude the possibility of predicting the behaviour of a particular bend to closer than ±20 per cent.
Efficiency of Supersonic Nozzles for Rockets and Some Unusual Designs
Authors: Fraser R. P. , Rowe P. N. , Coulter M. O.
Published: October 2007

The paper describes experimental work that has been carried out over a number of years to find an efficient rocket-nozzle shape that could be manufactured simply. Experiments have been conducted with nozzles generally of 1/2-inch diameter throat discharging air to atmosphere from reservoir pressures in the region of 900 lb. per sq. in. and the thrust reaction and discharge rate have been measured. The air flow within the nozzle and the issuing jet have been examined photographically. The apparatus used and the experimental techniques are fully described.

The investigation has determined the best design for simple nozzles of conical divergence and found these to have a thrust efficiency of some 96 per cent. Suitable entry radius and divergence angle are recommended and the effect of machining errors, of obstructions in and near the nozzle and of operating at incorrect pressure ratios have all been considered experimentally.

In the course of this study, a number of unusual designs has been considered. These include annular nozzles, a variable thrust-nozzle, and a nozzle designed to be mounted at the front of a rocket. These unconventional nozzles all have some special feature which makes them particularly suitable for certain requirements.

The paper gives data on all the nozzle-design details investigated and an attempt has been made to relate the observed thrust-losses in conical nozzles to a simple theory. Throughout the research and in presenting the results, the requirements and interests of the rocket-motor designer have been kept in view.
Modern Trends in Waterworks Pumping Machinery
Authors: Hudson T. Irvine
Published: October 2007

The paper stresses the importance of water in the life of the community, the various factors governing the location and size of pumping stations, the magnitude and diversity of demand and the topography of the area of supply, all of which have a bearing on the type of machinery and the system of control to be employed. Trends from the past are traced from the slow-speed and mainly steam-driven plant of the nineteenth century, to modern high-speed installations, including progress in the design of pumps of improved efficiency and high-tension motors for surface duties and for submersible application. Reference is also made to new problems which have arisen, such as surge control, the limitations of the A.C. electric motor as a driving agent, and the increasing use of automatic and remote controls. The paper concludes with a few thoughts on the future.
Design of Bolted, Flanged Joints of Pressure Vessels
Authors: Lake G. F. , Boyd G.
Published: October 2007

The paper contains an analysis of the stress distribution in bolted flanged joints of pressure vessels, and presents a design procedure for such joints based on the analysis. Existing bases of design are unsatisfactory in that they are derived from treatments which assume elastic conditions to apply, and so lead to fictitiously high stresses. These stresses imply that parts of the joint assembly yield plastically. The analysis in the paper takes account of such plastic behaviour.

The design procedure includes methods for determining the critical dimensions of a joint, including the number and size of bolts. It is shown that there is an approximate limit of 25,000 on the product of design pressure (lb. per sq. in.) and inside diameter of flange (inches) within which it is possible to design flanged joints with flat gaskets.

A formula is derived whereby a preliminary estimate of the flange thickness may be readily obtained. Other formulae are given which enable closer approximations to be made of the thickness required depending upon the extent of the influence of plastic strain. Examples are given to illustrate the design procedure.
Static Bending of Pre-Twisted Cantilever Blading
Authors: Carnegie William
Published: October 2007

In the present paper the static bending of pre-twisted cantilever blading is examined. The blading is pre-twisted linearly about the centroid of its cross-section to a maximum angle of π/2 radians and is considered to be mounted encastré at the root. The behaviour of such blading, particularly when bending under a distributed load, is of considerable practical importance.

By the application of variational calculus, static equilibrium equations are derived from expressions for the total potential energy of blades subject to either concentrated or uniformly distributed bending loads. Solution of the equilibrium equations yields expressions for the static deflexions. Over a range of pre-twist angles between 0 and π/2 radians deflexions are calculated for blades of (1) narrow rectangular cross-section when subjected to either method of loading, (2) narrow aerofoil cross-section when subjected to a uniformly distributed load.

Sets of steel cantilever blades of narrow rectangular cross-section are loaded laterally at their free ends and the deflexions determined by measurement. The experimental values of deflexion compare reasonably with the relevant calculated ones. Small discrepancies between the two sets of results are not yet fully explained and further investigation of the problem is under consideration.

For blades where the pre-twist angles do not exceed π/2 radians, the agreement obtained between the two sets of deflexions for the concentrated load system is such that the validity of the theory, when it is applied to other loading systems, can safely be assumed without further recourse to experiment.
Part II: Running-In Characteristics
Authors: Davis A. J.
Published: October 2007

A series of bearings manufactured from two different materials and having various clearance and length diameter ratios has been tested on journals having various types of surface finish, using the machine and experimental technique described in Part I. The investigation was concerned mainly with the changes in performance which occur during running-in, and with the ultimate performance which is obtained, under conditions of thin film lubrication. Some tests have been made on the effect of a solid boundary lubricant (molybdenum disulphide).
Estimation of Dryness Fraction and Mass Discharge of Geothermal Bores
Authors: Belin R. E. , Bainbridge A. E.
Published: October 2007

A method is described in which flow nozzles were used for investigating steam-water mixtures discharging horizontally from geothermal bores. British Standard and 25-deg. approach nozzles were modified, so that the density in a small column, with the throat diameter as axis, could be estimated by measuring the absorption of beta rays, in their passage diametrically through the mixture. A single density determination is shown to be sufficient to estimate the dryness fraction. If the upstream pressure is also noted then the mass output can be calculated using an empirical equation similar in form to the single-phase mass-discharge equation derived from Bernoulli's principle. For the dryness fraction one calibration curve suffices for 25-deg. approach nozzles of various diameters. By nozzle rotation the angular distribution of the water was measured and hence its cross-sectional area.
Dead-Weight Stresses in Piping Systems and Their Inclusion in Thermal Stress Analyses
Authors: Poynor J. F.
Published: October 2007

A method is given of accurately analysing the dead-weight stresses in piping systems. Both the uniformly distributed weight of the pipe and its insulation, and point loads such as valves are considered. The effects of constant-support spring hangers or counterweights are also included in the analysis.

The paper is based on the Meyer-Hovgaard and grapho-analytical systems of pipe stress analysis which in their present form deal solely with thermal expansions. These methods have been extended to deal with the dead-weight of both straight and curved pipe, and the effects of the flexibility and stress intensification factors for bent pipe may be included.

For large-bore, low-temperature pipes, the dead-weight analysis may be carried out on its own. For high-temperature pipes the dead-weight analysis may be included as an integral part of the thermal analysis for the pipe, using the same flexibility coefficients as for a normal thermal analysis.

Tables of dead-weight constants have been derived, which for a dead-weight analysis replace the normal thermal expansion constants. An example is given of a three-dimensional 24-in. pipe at 950°F subjected to thermal expansions and its own dead-weight. Suitable support for the pipe is considered in the analysis.
Plastic Design of Rotating Discs
Authors: Heyman Jacques
Published: October 2007

The labour involved in calculating stresses in turbine or compressor discs is usually considerable. The equations cannot in general be solved explicitly, and tables and charts must be used. The basic difficulty arises from the fact that a second-order non-linear differential equation governs the problem. If, however, attention is confined to the condition at which the disc is on the point of collapse, that is, at which the whole of the disc has just become plastic, the problem is simplified considerably. Instead of using an elastic ‘safety factor’ on stress, an overspeed factor is used; further, one of the stress components is known at collapse, and only a first-order differential equation has to be investigated.

This plastic design method will lead to profiles similar to those given by elastic design, but the calculations are much more rapid. At the end of the paper is given a fully worked design example; before reading the bulk of the paper, the designer may wish to compare this plastic design with the results given by one of the more usual methods.
Reheat Practice in British Power Stations
Authors: Brown F. H. S. , Dore J. W. H.
Published: October 2007

The Central Electricity Generating Board's current plans for new generating capacity using fossil fuels are based on the use of large boiler-turbine units in which reheating of the steam after initial expansion is employed. The background to the development of these units is reviewed and the ways in which the use of reheat affects the design of the main items of plant, the significance of unit rating and its influence on design, and the special requirements imposed by the need for the plant to be suitable for two-shift operation are considered. Reference is also made to certain aspects of the design of generators and of some items of auxiliary equipment which, although not related to the use of reheat, are very much a part of current practice. Some of the problems encountered in the evolution of the latest designs are discussed, and the solutions to them currently adopted described.
The Thrust of a Supersonic Conical Nozzle with Non-Isentropic Flow
Authors: Rowe P. N.
Published: October 2007

This analysis derives an expression for the thrust of a non-ideal supersonic conical nozzle in terms of coefficients that can be measured experimentally. The coefficients chosen are discharge coefficients pressure coefficient, and the geometric divergence coefficient.

Expressions are developed for the gas velocity, the area ratio and the thrust in terms of the pressure ratio, the specific heat ratio, and the above coefficients.

Optimum operating conditions are deduced and it is shown that the jet exit pressure should be greater than atmospheric for maximum thrust. The proposed equation is in good agreement with observed results.
Light Mechanical Engineering in South Wales
Authors: Bulleid H. A. V.
Published: October 2007

Light mechanical engineering in South Wales began to develop about 1938, and this paper describes the following typical modern products offering notable design, production, and operational features.

Diaphragm valves with control gear and modern impervious materials; turbine type flowmeters and fuel/water separators; the manufacture of washing machines; watches and clocks; circuit assemblies for digital computers; and some details of test rigs and plant used in chemical and textile process industries.
Design and Development of Engines for High-Speed Flight
Authors: Moult E. S.
Published: October 2007

Engineering, according to our Senior Institution, is ‘the art of directing the great forces of power in nature for the use and convenience of man’. Mechanical engineering as applied to aeronautics is, I consider, mechanical engineering at its best. And this is not for any altruistic reason but because of the very real prizes to be obtained from improved performance and reduced weight.

It is only 50 years since the first aircraft flew and now more people cross the Atlantic or the Continent of America by air than by all the alternative means available. The rate of advance has been terrific and the ever-changing picture has posed new problems and issued new challenges at every turn. Whilst it may be argued that the rate of development has stemmed principally from the military significance of aviation, the lessons learnt have been applied to civil transport. In addition, new materials, new techniques, new principles of design have greatly benefited other branches of engineering and stimulated other industries.