bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Size Effect in Fatigue of Plain and Notched Steel Specimens Loaded under Reversed Direct Stress
Authors: Phillips C. E. , Heywood R. B. 
Published: October 2007

The fatigue strength under reversed direct stress was ascertained for specimens of various diameters in the range from 0·19 inch to 2·4 inches, the largest diameter being determined by the capacity of the machines available. Two steels were used in this investigation—a 25-ton mild steel and a 65-ton, per cent nickel-chromium steel. The specimens were either plain or notched (transverse hole) and, as far as possible, geometrical similarity was preserved with regard to the transition radii and the diameter of the transverse hole. A few fatigue tests on other types of notch, such as a circumferential V-groove and a shoulder, were also carried out. No intrinsic size effect with either material was observed with the plain specimens. With transverse-hole specimens in mild steel, the fatigue limit was ±8·4 tons per sq. in. for specimens of 0·33 inch diameter, and 6·1 tons per sq. in. for specimens of 1·7 inches diameter, thus showing that an appreciable size effect was present. A similar size effect was found with the alloy steel specimens containing a transverse hole, and fatigue limits of ±17·1 and ±13·9 tons per sq. in. respectively were obtained for these two sizes of specimen. It is suggested that the low values of fatigue-strength reduction factors usually associated with mild steel as a result of laboratory tests do not apply to the larger sections of this material commonly employed in engineering practice.
Gear-tooth Stresses and Rating Formulae
Authors: Merritt H. E. 
Published: October 2007

The state of knowledge about stress conditions in gear teeth is briefly reviewed, and directions in which further research is required are indicated. The assumptions underlying methods of stress-comparison, and the chosen load-points, are considered in relation to profile-modification, leading to revised conceptions of “precision” and “commercial” classes of gear. The present (British standard) basis for the design of “commercial” teeth is stated and a new basis for the design of precision, high-duty gears is offered. Criteria of surface stress are re-examined and current British standard rating formulae for wear are shown to be equivalent to the use of an unmodified criterion Sc = Fc/ Rr in conjunction with a speed factor which is a function of pitch circle velocity and gear ratio. New values for zone factors and strength factors for spur gears have been determined on the revised assumptions, and it is shown how the factors for helical teeth may be derived from those for the virtual spur gears. The assumptions underlying rating formulae for variable load-cycles are also examined, and a revised formula is suggested whereby present inconsistencies are removed.
Use of Heavy Fuels for Medium-sized Marine and Stationary Diesel Engines
Authors: Smith J. R. P. 
Published: October 2007

Problems are discussed associated with the burning of heavy fuels in medium-speed, two-cycle, trunk-piston types of engine. Tests with a stationary engine are described, and performances, rates of cylinder-bore wear, and degrees of fouling are compared, when five classes of fuel are burnt. Pre-treatment of fuels in the centrifuge is considered, and the results from practical experience show how certain fuels with high ash content, probably in an oil-soluble form, promote rapid cylinder-bore wear, even after being subjected to thorough treatment. Comparative rates of deterioration of the lubricating oil are recorded when different classes of fuel are burnt, and figures are given which show how fuels with a high sulphur content promote the formation of sulphuric acid in the crank chamber. Findings with the stationary engine are correlated to marine requirements, and the economy aspect is presented of bunkering a lower grade of fuel in a coastwise vessel of 2,500 tons dead weight. The conclusion is reached that a marine Diesel fuel, preferably a distillate, instead of gas oil could be bunkered with financial advantage, but that in the light of present knowledge the use of a boiler-grade fuel could not be recommended.
Nodal Pattern Analysis
Authors: Grinsted B. 
Published: October 2007

The paper elucidates the manner in which impeller blades, turbine and axial compressor blades, aircraft and marine propeller blades or similar bodies, vibrate in their higher modes. It is demonstrated that complex nodal patterns derive from consistent series of simpler modes and that the frequencies of the latter may be plotted in families of curves. Classical work of Chladni, together with more recent investigations on free square and circular plates, is first reviewed. The similarity of the manner of vibration of the cantilevered plate is then described with a note on the relation of the torsional series of modes to the simple flexural “bar” type modes. The vibration nodal patterns of impeller blades are discussed and diagrams illustrate how “complex” modes were resolved into their constituent “basic” modes, each having an ordered place in the families of modes and frequencies. Similar analysis, with examples, is shown to be applicable to turbine blades, and aircraft and marine propeller blades.
Wind Tunnel Investigations on Rotating Blades of Aerofoil Section
Authors: Khalil K. H. 
Published: October 2007

The results are presented in this paper of investigations on the pressure distributions around aerofoil section blades while rotating in a wind tunnel. The experimental difficulty of obtaining pressures during rotation was overcome by the use of a special gauge attached to the hubs and illuminated by “Strobo-flood” for direct observation. Pressure diagrams and lift coefficients were obtained along the radius of a double-blade set, arranged as a windmill, for various angles of incidence. Static tests were conducted also in all cases to find values for comparison. As the purpose of the work was to contrast rotating and static conditions, two main facts are emphasized: the similarity in the pressure diagram shapes and the significance of the spin factor. It therefore becomes possible to correct ordinary test results obtained when using stationary aerofoil blades in wind tunnels by adding the effect of a vortex of rotation of uniform strength.
Machine Tool Simplification, Especially as Applied to Horizontal Boring Machines
Authors: Sparkes C. A. 
Published: October 2007

The author believes that simplification, while it must not be regarded as the panacea for all the ills of our industry, can if correctly applied be of immense benefit and that, though much has been said and written on the subject, few practical examples of its application in design and manufacture have been made available. The early history of machine tools is reviewed in this paper, and as the horizontal boring machine incorporates the general features of most machine tools it is used as a typical example. Some suggestions are made on the subject of simplification from the aspect of design, and practical examples are given of its application to patterns, castings, machining, lubrication, controls, measuring systems, and electrical equipment. Single-purpose machines, tool equipment, and accessories are also examined. It is proposed that the maximum advantage cannot be gained from a process of simplification unless a high degree of standardization is accepted, and therefore in reviewing the design of a complete range of horizontal boring machines a new principle of unit construction is explored in theory and practice. Examples are given of the application of this unit system to all sizes of horizontal boring machines, including the universal type. The paper concludes with a description of a new slideway grinding machine generally constructed from standard units.
Welding in Marine Engineering
Authors: Pemberton H. N. 
Published: October 2007

This lecture comprises a survey and commentary on the use of welding for the construction and repair of marine machinery for main propelling and ancillary purposes. The history of welding in relation to marine engineering is traced from the hammer welding of boiler seams in 1870 up to the present day, when welds made by modern processes are accepted for highly stressed components. Descriptions of welding processes are omitted since the lecture deals with welding applications rather than welding technique. Numerous examples are given and illustrated, and many of them relate to design details which are typical of good practice and are accepted by ship classification authorities. The lecture is divided under two main heads, namely, “New Construction” and “Repairs”. A further subdivision is made under “New Construction”, so that boilers, pipe-work, machinery components, turbines, gearing, electrical propulsion, refrigerating plant, and dredging craft are dealt with in that order. Also included in this section are some remarks of general interest on the subject of residual stresses and their relief by thermal treatment. Problems concerning the welding of alloy steels for gas turbines are discussed. There is need for research into the weldability of these steels, bearing in mind that not only the welds should be free from micro-cracks to start with, but they should also be equivalent to the parent metal in resistance to metallurgical and physical deterioration whilst operating at high temperatures over long periods. A field of welding which is always of interest to marine engineers is in repair work. Unlike land plant for which complete resources for repairs are usually available, marine machinery may be involved in mishaps and breakdown on the high seas and in remote parts of the world when repair facilities might be primitive, or even non-existent. Many ships now carry electric welding equipment, and sea-going marine engineers include welding in their many manual accomplishments. Several interesting examples of weld repairs are described, which in some cases have enabled ships to complete their voyages carrying valuable cargoes with a minimum of delay. Other examples are given which emphasize the discrimination that is necessary in deciding whether or not a welded repair is desirable. Unfortunate consequences have followed the ill-advised use of welding in some cases.
Some Practical Aspects of Cutting Tool Nomenclature Arising from Recent Research
Authors: Galloway D. F. 
Published: October 2007

In recent years a considerable volume of research has been carried out to improve the techniques employed in the most widely used metal machining processes. An essential preliminary to all these experiments in turning, milling, drilling, tapping, etc., was accurate control of tool shapes. This necessitated the development of adequate tool-measuring equipment and a comprehensive nomenclature. The nomenclature has resulted from an analysis of tool geometry, and an examination of applicable tool grinding methods and inspection equipment. The nomenclature has been extended to take account of factors which were proved by research to be of considerable practical significance in the ultimate tool performance. Nomenclatures for the most commonly used types of tool are presented as a basis for discussion together with typical examples of tool geometry, tool grinding methods, and tool inspection equipment which should be taken into account when developing improved nomenclatures. Reference is also made to some of the British, European, and American standards, which have an important place in these discussions. Some of the problems involved in the workshop application of cutting tool nomenclatures are also considered. Recently, significant advances have been made in tool nomenclature as a result of the increasing co-operation between manufacturers and users of tools, but the nomenclature used for development work in research stations, colleges, universities, and industrial research laboratories, needs to be more comprehensive and precise than that at present used in general engineering practice.
Present Trends in Surge Tank Design
Authors: Jaeger C. 
Published: October 2007

The author summarizes the well-known theory of surges in surge tanks, dealing chiefly with the fundamental equations and introducing some preliminary remarks on the stability of surges. He then describes the different types of surge tanks, ordinary cylindrical tanks, tanks with variable section and expansion or reservoir chambers, tanks with restricted orifices, and differential surge tanks, with special mention of surge tanks in conjunction with underground power stations. The loading conditions to be adopted are discussed and the reason why load changes on the electrical grid are the prime cause of surges is explained. The basic assumptions adopted for surge calculations by Italian, Swiss, French, and British engineers are reviewed, and it is shown that, in spite of many apparent disparitiés on special points, there is widespread agreement on fundamental questions. The interaction of surges, water hammer, and turbine governing is discussed in the light of the most recent tests on large power stations and of the results of modern theories, and the importance of the influence of water hammer on surge tank design is considered together with the special case of surge tanks connected to feeder canals.
Fuel Systems and Controls for Marine Gas Turbines
Authors: Darling R. F. 
Published: October 2007

It is emphasized that reliability is by far the most important requirement in the control system of a marine power plant. The controls of the Pametrada 3,500-h.p. gas turbine, which is taken as a typical marine unit, are then discussed. The sprayers, control blocks, fuel system, transmission, reversing mechanism, and governors are described in turn, and the reasons are given why various features were adopted in preference to the possible alternatives. There is an account of test-bed experience concerning these items. Probable future developments in the field of controls are then considered, but these are found to depend mainly on the way in which the gas turbine itself is developed for marine purposes. The paper therefore concludes with a discussion of the type of gas turbine most likely to be installed in merchant vessels, and the means whereby it will be controlled.
The Calculation of Roll Force and Torque in Hot Rolling Mills
Authors: Sims R. B. 
Published: October 2007

Equations are derived for the normal roll pressure, specific roll load and torque in hot rolling mills, using the condition for plastic deformation in rolling derived by Orowan, together with von Kármán's equation of equilibrium. Although applying strictly to the rolling of ideal plastic-rigid materials, these equations may be applied to the rolling of materials which strain-harden by using a mean value of the yield stress in the pass. The equations have been checked against measurements made when rolling pure lead at room temperatures, and against the results of the experiments on steel at elevated temperatures carried out at Holfors. There is close agreement between the calculated and measured roll loads, but the roll torque is over-estimated slightly by the theory, above reductions of about 30 per cent in thickness.
Practical Training in Industry for the Graduate in Mechanical Engineering: Part II
Authors: Fulton H. W. 
Published: October 2007

Essentially, Part II of this paper recommends planned interweaving of theoretical and workshop practice throughout the period of training. A plea is made for industry's side of training to include some experience in non-engineering, but essential and ancillary branches of the industry, e.g. production and stock control, costing, sales, and general office work. It is emphasized that the larger the organization, the more need there will be specifically to provide this external experience.
Practical Training in Industry for the Graduate in Mechanical Engineering: Part III
Authors: Medlock R. S. , Lant D. P. 
Published: October 2007

The potentialities of a graduate spring from the theoretical and fundamental nature of an academic training. This develops power of analysis, judgement, and initiative, which should be remembered when planning the complementary training course which is mainly practical and technological. The course should not attempt to make the graduate a skilled craftsman but rather to train him in the application of machine tools to production processes. The fully-trained graduate is expected to fill a vacancy in the production, sales, or research and development departments, and although the training can be slightly biased for those apprentices expressing a wish for a particular branch of engineering, early specialization should be avoided. The training programme should be flexible to suit the needs and progress of the graduate, always provided that sufficient time is spent in each department for him to make a useful contribution to output, but without wasting time on needless repetition. In every department, the period of instruction should be as intensive as possible, leaving more time for responsible duties. He is expected to add to his store of experience by analysing the bad things he notices as well as the good. These should not, of course, be reported, but he should be expected to make a weekly report on progress in order to help him crystallize his thoughts. The works training should be supplemented by post-graduate courses in technology and management studies. At the end of the training period, the next phase should rest with a high-ranking committee responsible for executive development.
The Effect of Auxiliary Fuels on the Smoke-limited Power Output of Diesel Engines
Authors: Derry L. D. , Dodds E. M. , Evans E. B. , Royle D. 
Published: October 2007

It is well known that one of the factors Limiting the power output from Diesel engines is the tendency to produce exhaust smoke. In consequence only some 65–70 per cent of the available air can be burnt. By reducing the full-load quantity of Diesel fuel injected and aspirating a volatile fuel, such as gasoline, into the intake air, power outputs of 20 per cent or more above the maximum rated load can be obtained without producing more smoke than when the engine is operated at full load under normal conditions. About 80 per cent of the available air can then be utilized. The effect of octane number of the auxiliary fuel is important, maximum smoke-limited powers being obtained with the higher octane number fuels, while with fuels of low octane number, power increase may be limited by the occurrence of knocking when the air-fuel ratio is too low. By limiting the power on Diesel fuel alone to about 80 per cent of the normal maximum and aspirating gasoline into the intake, it is possible to obtain a power increase of about 12 per cent at all speeds between that of maximum torque and maximum power without increased smoking or the occurrence of knock. Owing to improved economy, the fuel cost per brake horsepower per hour using gasoline aspiration, is not increased. Modifications required to the engine are slight and the fuels required to operate are readily obtainable; even if the auxiliary fuel should run out no damage would be done to the engine.
Some Model Experiments on Special Control Valves
Authors: Firth D. , Young Leslie 
Published: October 2007

A description is given of some model experiments undertaken to resolve problems occurring in the design of special control valves for use in the Hydraulic Machinery Laboratory of the Mechanical Engineering Research Laboratory. Four types are dealt with: (1) a valve to control flows varying from 1 to 30 cu. ft. per sec. in a flow-meter calibrating system; (2) a valve to control flows of up to 30 cu. ft. per sec. in an open pump testing rig with a maximum input of 350 h.p.; (3) a valve to control flows varying from 1 to 20 cu. ft. per sec. in a closed pump research rig with a maximum power input of 350 h.p.; and (4) a hydraulically-balanced in-line valve to control flows varying from 1 to 15 cu. ft. per sec. in a service supply.
Pipe Flanges Research Committee—Third Report
Authors: Johnson A. E. , Bailey R. W. 
Published: October 2007

The Third Report of the Pipe Flanges Research Committee is concerned, with the exception of elastic resistance strain gauge measurement of stresses of two standard flange rings, with the results of a programme of investigation, projected by the Committee in being when the Second Report was made, into the elastic and plastic (creep relaxation) behaviour of flanges, drilled and undrilled, by means of model flanges, and of certain bolt materials. Execution and completion of the programme and attention to its results, was interrupted and delayed by the 1939–45 war. Subsequently examination of the creep relaxation data showed that the phenomenon, and the interpretation of the results, involved difficulties unknown at the time the tests were made, and the need for further investigation became evident. The results, however, have important bearing upon the behaviour of flanged joints and also as a contribution to the subject providing a base for further advances. An Addendum to the Report refers to matters which arise in connexion with utilization of its results for engineering needs. The Committee wishes to record its indebtedness to the Reporter, Dr. A. E. Johnson, now of M.E.R.L., East Kilbride, and formerly of the N.P.L. Engineering Division, who has been chiefly concerned with the investigations at elevated temperatures, and to Mr. H. L. Cox, now of the N.P.L. Engineering Physics Section, and formerly of the N.P.L. Engineering Division, who has been principally interested in the investigation of elastic properties, and who was responsible for the automatic strain control equipment of the relaxation unit.
Comparative High-temperature Properties of British and American Steels
Authors: Bardgett W. E. , Clark C. L. 
Published: October 2007

Some rather substantial differences are found in creep data on similar steels published in various countries. In view of the importance of these differences in relation to design stresses, arrangements were made for an exchange of specimens between The Timken Roller Bearing Co., of Ohio, and The United Steel Companies in order to determine whether the results from the two laboratories, on the same steel, would be in agreement, and to compare the creep resistance of selected steels. Five representative high-temperature steels were chosen comprising three commonly used ferritic steels and two austenitic steels. For each composition, four creep curves were obtained, two by each laboratory. Stress, temperature, and time adopted in the tests in the two laboratories were the same and no attempt was made at standardization of test procedure. A high degree of reproducibility was shown by the test results for the two laboratories on the ferritic steels but those on the austenitic steels showed generally substantial differences. Only two British steels, both of ferritic type, showed similar creep behaviour compared with the corresponding American steels, the remaining three steels showing appreciable differences, which are discussed.