bluuebunny/crossref_metadata_2025_split huggingface dataset:
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 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.
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.
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.
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.
An Analysis of the Plastic Bending of Wide Plate, and the Effect of Stretching on Transverse Residual Stresses
Authors: Alexander J. M. 
Published: October 2007

Part I of this analysis is devoted to solving the problem of bending a wide beam of ideally plastic material, under substantially plane strain conditions. A geometric method of solution, in which the stress and strain paths during the deformation are determined in the stress plane, is compared with the well-known analytical solution. Curves are given which will allow the rapid estimation of bending moments and ‘spring-back’ for plates of an aluminium alloy conforming to B.S. 1476:HE 15W†. The system of residual stresses induced is determined and compared with that for a narrow beam. In Part II the geometric method mentioned above is used to estimate the effectiveness of stretching in reducing residual stresses which are transverse to the direction of stretching. This is a problem of some technological interest in that residual stresses arising from operations such as heat treatment and quenching are usually complex, lying in all directions within the plane of the plate. It is shown that stretching in a direction transverse to the major residual stresses is almost as effective in their reduction as stretching in a parallel direction.
Vibration of Cascade Blades Treated by Actuator Disc Methods
Authors: Whitehead D. S. 
Published: October 2007

This paper gives a theoretical method of calculating the aerodynamic forces on vibrating compressor and turbine blades subject to two fundamental limitations. These are, firstly, that the time for the fluid to flow through the cascade must be small compared with the period of the vibration, and secondly, that adjacent blades must vibrate nearly in phase. This enables any kind of two-dimensional steady-flow cascade data to be used. The methods given also allow the vibration forced by fluctuations in the incident flow to be calculated. The main conclusions are as follows: (1) Bending vibration of unstalled blades with small mean deflection is always damped. (2) A criterion for bending flutter of unstalled blades with large mean deflection is derived. This is qualitatively supported by experiments carried out by Shioiri and Shibata (1)†. (3) A condition of instability of the flow through stalled cascades of fixed blades is derived, and agrees with previous investigations by Fabri and Siestrunck (2) and Rannie and Marble (3). This also agrees with the results of an experimental investigation by Wood (4). (4) A criterion for the bending flutter of stalled blades is derived, and it is shown that this limit is reached before the instability limit referred to in (3) above. (5) It is found that, except for a particular case of zero stagger cascades, flutter of unstalled blades in torsion will always occur. For this case, however, the first fundamental assumption referred to above is unlikely to be true and more detailed investigation of this case is required.