bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Renaissance of Mechanical Properties
Authors: Vivian A. C. 
Published: October 2007

The present technology of the mechanical properties of materials is suffering on account of its development from casual beginnings now known to have been ill-conceived and unsystematic. An improved understanding of the behaviour of metals under load is with growing difficulty reconciled with the original foundation and framework, and really calls for a replanning of the site and a redesigning of the edifice. Starting afresh on the fundamental basis of the true stress-strain curve itself, the technology appears to lend itself to reconstruction affording major simplification and better illumination. The reorientation of outlook followed by planned action for systematization would appear to be justified and to promise progress in unexpected directions.
Problems Connected with Reclamation of Worn Parts by the Metal-spraying Process
Authors: Ballard W. E. 
Published: October 2007

In times of peace the salvaging of worn parts is not usually a major problem confronting the mechanical engineer. Every consideration is given to new materials and to novel designs, but except for those engaged on works maintenance, the returning of old parts to service has not in the past received enough attention from professional engineers. In war time, however, the repair of damaged material becomes a national duty. Although metal spraying by the wire process has become more widely known during the past two decades, the number of engineers who would feel competent to judge its suitability for any repair is comparatively small. The object of the present paper is to describe certain matters of interest to engineers in connexion with this form of salvage. It is not proposed to give details of metal spraying tools or pistols, as descriptions of these may be consulted in the technical press (Rollason, Turner, and Budgen 1939).† For the same reason an account of the many parts normally repaired by this method (Ballard 1942; Ballard, Fairbairn, and Pilkington 1942) is omitted. Metal spraying is being used commercially to a very large and increasing extent for reclamation work. To assist engineers faced with the problem of repairing a worn part, the author has arranged the paper in the form of answers to the following questions: ( a) Is metal spraying a suitable method of reclamation? ( b) If so, how must the work be prepared for spraying? ( c) What method of spraying and which metal should be used? ( d) What finish is necessary?
The Repair of Worn or Over-machined Parts by Electrodeposition
Authors: Hothersall A. W. 
Published: October 2007

Worn or over-machined parts may be restored to size by electrodeposition of nickel or chromium followed by machining or grinding to remove excess of deposit. The mechanical properties and the adhesion of these deposits are described with special reference to nickel. It is shown that strongly adherent nickel coatings can contribute appreciably to the tensile strength of the steel upon which they are deposited. Electrodeposited coatings may reduce the fatigue strength of steel and their use on parts subject to high alternating stresses should be made with caution. General notes on the process are given for the guidance of users.
The Application of Statistical Methods to the Control of Industrial Costs
Authors: Neal Norman R. 
Published: October 2007

Quality control studies the variation from standard of tangible articles, whereas “cost control” studies the variation from standard of the workers' efficiency, and consequent variation in production cost. In essence, the system consists in setting standard times, and thus standard costs, for all jobs and for the elements making up the complete jobs. Percentage divergencies from those standards are recorded at regular intervals on charts, a separate chart being used for each class of work, both as regards time and cost. Control lines, calculated from previous results over a period, upon the same mathematical principles as for quality control, are inserted on the charts. When a reading falls outside the control line, action must be taken to ascertain the cause. However, unlike quality control in which articles covered by abnormal readings can be scrapped, abnormal time or cost must still figure in the final examination of production cost. A sufficiently fine subdivision of the elements of a job will prevent an occasional abnormal reading on one portion from giving abnormal reading for the complete job. The individual readings are combined to form a grand total chart; careful watching of the detail charts enables the grand total chart to be maintained in control and it is from the latter chart that the “cost index” (percentage divergence from standard of the cost of the complete product) is obtained, which enables the latest actual cost at a particular moment to be determined directly. A continuous check is thus kept on the production cost of all the principal details; any abnormal fluctuations of cost become quickly apparent, and can be readily traced back to their cause. Concurrently, a simple method is provided for obtaining the total actual cost of the complete product at any time.
Sampling Schemes for Qualitative Inspection
Authors: Swan A. W. 
Published: October 2007

The paper opens with a description of the applications of “qualitative” inspection. Briefly, it is used where “quantitative” inspection, or inspection by direct measurement on a continuous scale, is impossible, as in the case of a destructive test or a visual inspection for blemishes, or as an economical alternative through limit gauges to “quantitative” inspection. The industrial and theoretical factors affecting the choice of a sampling scheme for qualitative inspection are discussed, particularly producer's risk (the risk that good material may be rejected), and consumer's risk (the risk that bad material may be passed). It is pointed out that a sampling scheme can be devised to give an agreed maximum producer's and consumer's risk. It is shown that the maximum allowable percentage of defectives cannot be set in an arbitrary manner, but only after consideration of the process average percentage of defectives. If the ratio of the maximum allowable to the process average is too low (e.g. if the requirement is too severe), the minimum sample size for reasonable producer's and consumer's risk is impossibly high. A simple chart is provided, from which, with the industrial factors limiting the size of lots and the size of samples, the desired percentage of inspection, and the process average percentage of defectives as the “known” quantities, it is possible to read off the best single or double sampling scheme to give agreed maximum producer's and consumer's risks. The chart gives the best size of sample and the corresponding “pass up to” number of defectives per sample. The paper concludes with instructions on when and how to change to more severe sampling conditions, when results from successive samples show a deterioration in quality from the process average; and discusses the need to keep the new conditions in force until there is satisfactory evidence that the quality has improved again to the process average.
The Fencing of Dangerous Parts of Machinery
Authors: Hepburn Henry A. 
Published: October 2007

The Factories Act, 1937, introduced higher standards of general “fencing” or safeguarding requirements for machinery, and gave legal recognition to types of guards other than those of the fixed type. During the past forty years, more attention has been devoted by machinery designers to the incorporation of guards to dangerous parts, but it is considered that more could be done in the future. Safety engineering is advancing in experience and practice, and is receiving an impetus by the appointment of safety officers and safety committees by many important firms. In order to assist all concerned to an appreciation of those parts of machinery that the experience of the Factory Department for over 100 years has proved to be dangerous, certain axioms, applicable to various parts, or combinations of parts, of dangerous machinery are formulated, together with some principles of fencing. The object is to place in the hands of those who design machinery, or who have the responsibility of accident prevention in a factory, some guiding principles for application to their problems. The principles of fencing are exemplified by illustrations of a few representative types of guards in present use, but such references are necessarily brief and are of but a few applications of the general principles. The requirements of the Act are in general terms, and compliance can be given in many ways, for which the paper is intended to give general guidance.
The Application of Fabricated Construction to Machine Design
Authors: Koenigsberger F. 
Published: October 2007

Modern welding equipment and practice have given the machine designer the opportunity of applying fabricated welded construction in an efficient manner. This does not mean that steel fabrications should replace castings everywhere, but that steel should be kept in mind as a material which is available if technical or economic considerations favour its use as an alternative to that of cast iron. The designer of a fabricated steel machine structure has to consider the properties of the material and the problems of the manufacturing process, which are different from those which apply for the generally used cast iron construction. Layout arrangement, and shape of the fabricated construction have to be designed in accordance with the foregoing conditions. In machine structures, stiffness against distortion and freedom from vibrations are usually of major importance as compared with strength. A comparison of strength, stiffness, and freedom from resonance for simple fabricated steel and cast iron structures is given in the form of graphs. The problem of the design of ribs for static and shock load conditions is discussed; and some designs criteria are determined. Some observations on the procedure of stress relieving after fabrication are also included. The author, in addition to setting out the principles governing the design of fabricated structures, gives information on the execution of production drawings, including definite instructions for the most efficient procedure in the fabricating shop. Typical examples of fabricated machine structures are also included.
Coupled Engine Torsional and Propeller Flexural Vibrations
Authors: Morris J. 
Published: October 2007

In the initial treatment of resonant torsional vibration in engine crankshaft propeller systems, the basic assumption was made that for practical purposes a propeller could be regarded as a rigid pulley in the plane of rotation. At an early stage, however, it became evident that theoretical results ensuing from the rigid pulley hypothesis could not explain certain engine-propeller failures, and thus it came to be realized that the flexibility of the propeller blades must have an important influence in coupled crankshaft-propeller vibrations. In this paper an analytical method is given for the determination of coupled engine torsional and propeller flexural vibrations, in which account is taken of blade section, blade twist, hub moment of inertia, pitch setting angle, and speed of rotation. The propeller blade is divided chordwise into six portions which are regarded as having their masses concentrated at their centres of gravity, while account is taken, so far as is possible, of the actual elastic properties of the blade. In the case of an aircraft propeller, the problem is simplified in that the mass axis is practically straight and coincident with the flexural axis, so that flexural and torsional vibrations of the blade itself are not coupled. The theory has been applied to a three-blade propeller used on two different engines, in both of which agreement between the calculated critical speeds and those observed experimentally on the cable hangar was found to be satisfactory. Moreover, the calculated fixed root frequencies for the fundamental and six overtones accorded very closely with the corresponding values evidenced on a -model of the blade by bowing and calibrated oscillator tests.
The Variable-Speed Hydraulic Governor
Authors: Bujak J. Z. 
Published: October 2007

Due to the “square” law of the variation of centrifugal force with speed, a centrifugal governor is not well suited to variable-speed engines with a wide range of speeds. It lacks power at low speeds, which results in poor idling, and it has an excess of power at high speeds. Also the presence of heavy weights and springs may give rise to undesirable resonance phenomena. This paper deals with the development and gives the theory of a variable-speed hydraulic governor consisting of a positive displacement pump and of a pressure-operated plunger. Such an arrangement should be distinguished from a hydraulic relay as used in servo-governors. The story of its development is told, starting from the simplest possible scheme. The various troubles experienced are reported, together with the way in which they were overcome, leading to the design of a production type hydraulic governor meant primarily for road transport compression-ignition engines. A mathematical theory of the hydraulic governor is derived and the conditions for stable governing established, as well as the criteria for a definite convergency of the disturbances set up by a sudden change of engine load. The magnitude of the temporary increase of engine speed following a sudden throwing-off of its load is calculated. The results of the mathematical analysis are discussed and illustrated by some numerical examples. These compare quite well with the results of experiments carried out on the engine. Some of the conclusions arrived at, and the formulae derived, are applicable to variable-speed governors of any type. A hydraulic governor which was developed as a result of the research described underwent several hundreds of hours of bench testing, as well as many thousands of miles of road testing.
Dynamic Loading and Some Indications of its Effect on Internal Combustion Engines
Authors: Chapman E. C. W. 
Published: October 2007

The paper shows that when forces are applied to a mass which is connected to another mass by a stressed member, the “stressing forces” (i.e. the forces which must be considered when stressing the connecting member) are not the applied forces, but are fluctuating forces comprising the applied forces modified by vibratory forces at the natural frequency of the system. The relative intensity of these vibratory forces depends upon the rate of application of the applied forces, and the period for which they are sustained, compared with the natural periodic times of the system to which the forces are applied. Formulae are given for assessing the “stressing” forces under different conditions of application of the applied forces, and a graphical method of obtaining “stressing” force curves corresponding to applied force curves is described. The application of the theory to some of the forces occurring in internal combustion engines is illustrated by a series of curves.
On the Theory of Automatic Control: Regulator Equations
Authors: Kaufmann Paul G. 
Published: October 2007

Different types of automatic regulators can formally be represented by differential equations between the deviation from normal of the controlled variable and the displacement of the power device of the regulator. The equations are derived for the “floating-and-proportional”, the “proportional-position”, the “floating”, and the “first and higher derivative” control, and the characteristics for drooping and non-drooping control are described. The paper shows that identical results may be obtained by self-contained regulators and by control equipment consisting of separate units which may comprise a regulator proper, a servo-motor, and sometimes also one or more impulse transformers. Such composite control equipment has the advantage of greater flexibility, as the same elements may be used in various arrangements producing entirely different control actions. The regulator equations by themselves give no information on the ultimate behaviour of a regulator, if applied to a particular plant, as this depends just as much on the characteristics of the plant itself. Information regarding stability of control, maximum deviation, and period of oscillation can be obtained only by combining the regulator equation with the equation describing the plant to which the regulator is applied.
A Thermodynamic Theory of Circulation in Water-Tube Boilers
Authors: Silver R. S. 
Published: October 2007

A thermodynamic evaluation is made of the work available for, and the resistance to circulation by, natural convection in a water-tube boiler. This leads to a theory of circulation which is independent of the usual type of hydraulic theory expressed in terms of density difference. The theoretical circulation equation is first used for the direct estimation of examples of particular circuits. Estimates made by means of this are in good agreement with estimates made on existing hydraulic theories. It is then shown that the present theory lends itself to a more general formulation, and the treatment is developed to elucidate the general physics of natural convection in water-tube boilers. The fundamental variables are certain characteristic non-dimensional groups. The system is shown to possess critical limits of stability and of circulating quantity. Expressions for these are derived, and the general type of performance is given in charts. The relation of operating pressure and rate of heating to these critical limits is discussed. In the course of the development a definition of an ideal standard boiler is proposed which is suggested to be a useful conception. By means of the present theory an adequate account of qualitative characteristics of boiler operation can be given. Its possible quantitative accuracy is then discussed. Some comparison with experimental results is given. Appendix I shows that the theory is generally applicable to the convection of non-evaporating fluids in tubes as well as to the boiler circuit. Appendix II indicates the relevance of the theory to the question of forced circulation. In Appendix III the problem is treated by dimensional methods and the characteristic non-dimensional groups are confirmed. Another characteristic group is shown to apply when capillarity is included. This permits some discussion of the effects of discontinuity and of the requirements of scale models.
Modern Methods of Water Treatment
Authors: Walter A. J. R. 
Published: October 2007

Water is one of the most important raw materials used in industry. Its uses are multifarious, including the processing of other materials, steam and power generation, cooling condensers and water-jacketed machinery, and for drinking purposes. It is often spoken of as “pure”, but in fact seldom is. Indeed, all natural water supplies contain impurities which often have a profound and far-reaching effect on the products being made and on the manufacturing costs. This fact has become more and more realized as industry has progressed. The introduction of new processes for materials and more efficient power generation has in turn made essential the removal of even extremely small amounts of impurities from water that a few years ago would have been tolerated. For example, the increase in boiler pressures alone over the last twenty-five years has called for complete revision of the quality standard of boiler feed water. Fortunately those responsible for research into, and practising the art of, water purification have kept a step ahead of these new requirements and most waters can now be treated in one way or another so as to render them suitable for practically any purpose. Revolutionary discoveries have been made and applied in the field of water treatment. This paper describes the major advances, among them new crystallization and precipitation processes developed for lime-soda softening and particularly the entirely new chemical field discovered in hydrogen ion exchange materials and acid adsorption materials. The combined use of these two new discoveries has resulted in the development of equipment for the production of the equivalent of distilled water without heat or evaporation.
Low-Pressure Ash-Sluicing Systems, with Particular Reference to Power Station Practice
Authors: Carr T. H. 
Published: October 2007

The purpose of the paper is to outline some of the salient features of the low-pressure recirculating water systems of ash handling, and to discuss some of the difficulties encountered with the pumps and the associated equipment employed. The author introduces his subject with a general consideration of the factors affecting the design of the ash plant, including its location in regard to the rest of the power station, the best type of plant to employ, and the general working conditions of the power station itself. This is followed by a description of the low-pressure systems for the water-sluicing of ashes and the methods of handling and disposing of the material. Space is also devoted to those features which require particular attention in order to secure the best results in operation. The physical characteristics of boiler ash are considered in some detail and typical ash and grit analyses and properties are given. One of the most important problems arising in this field is the corrosion which takes place in ash handling plant. The author gives details of the loss of metal in such circumstances, and gives the results of carefully controlled tests. The chief desiderata in the design of troughs and pumps are also outlined, and the paper concludes with some useful information on the costs of operation and maintenance of ash-handling plants.
Expanded Tube Joints in Boiler Drums with Special Reference to the Battersea High-Pressure Boilers
Authors: Shannon W. B. , Pratt C. W. , Webb T. B. , Carlson W. B. 
Published: October 2007

Particulars are given of the major pressure parts of two high-pressure boilers installed at Battersea Power Station, each comprising four alloy steel drums and their interconnecting mild steel tubing. Their design and working conditions are described, and a historical review is presented of their erection and of problems which arose whilst rendering the expanded tube joints leakproof. The gradual resolution of these problems is then traced through several stages. It was realized that the leakage was fundamentally due to the elastic strain which occurs in the tube holes of highly stressed drums, which, at Battersea, amounts to about twice that pertaining to mild steel drums. The holding power of the joint is thus relaxed to an abnormal extent, sufficient to permit leakage. The elastic deflexions, or total “spring” of the joint, resulting from the expanding operation, must therefore be correspondingly increased to accommodate the increased drum strain. Various suggested methods of achieving this are reviewed. Insertion ferrules were selected as the most promising, and experimental development tests to investigate its possibilities are described. A full-scale rehearsal of the method carried out on one of the steam receivers is recorded, and this is followed by a description of the final ferruling and testing of both boilers. A number of general observations and conclusions are given, and the subject of leakage and its causes is discussed in some detail. It is concluded that full advantage can be taken of the benefits which result from the use of high-tensile steel boiler drums, with mild steel tubes expanded into the drums. It is, however, essential that in the design stages the expected operating conditions of the expanded joints should be investigated on the lines suggested in this paper. The adoption of high-tensile steel ferrules as a feature of original design is justified by the results obtained at Battersea.