bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dependence of Joint Strength on the Degree of Expanding in the Tube Expanding Process
Authors:   Applied Mechanics Group, Culver L. E. , Ford H. 
Published: October 2007

The experiments, which were sponsored by the British Shipbuilding Research Association, were designed to study how the strength of an expanded joint depends on the degree of expanding with normal propulsive type expanders. Fourteen tests were made, varying the back extrusion from 0.029 in. to 0.093 in. on a 2 in. O.D. × 11/2 in. bore tube in 1 1/4 in. long seat There is an optimum degree of expanding for maximum joint strength measured either by the push-out load or mean seat pressure. The position of the maximum in the curve of push-out load is dependent upon surface finish. Within the inevitable variation present in industrial machining finishes the presence of a peak will be masked. Moreover, the peak occurs at a degree of expanding well beyond the values recommended by previous workers for the same size of joint. Bearing in mind the added difficulties of controlling the process in the field, these recommended figures are open to question Mean seat pressures as high as 5 ton/in2 are easily reached at the optimum degree of expanding In view of the large variations in joint strength that can occur even with carefully controlled expandings, reproducibility tests were carried out. It is shown that, where exceptional care is taken to control all the conditions of the test, good consistency in the characteristics of identically expanded joints is possible
Oil Whirl of Flexible Rotors
Authors:   Lubrication and Wear Group, Parszewski Z. , Cameron A. 
Published: October 2007

The equations for a flexible rotor in journal bearings are set up and solved, extending the method previously used by Hummel and Cameron. It is shown that if w is the natural elastic frequency of the rotor, A the resonant oil frequency for an infinitely stiff but otherwise identical rotor, then the combined frequency s is given by l/ s2 = 1/Λ2 + 1/ w2. This resonant frequency will usually occur when it equals 1/2 the shaft rotational frequency The frequency calculated by the method given here is applied to a number of cases of large turbines and alternators and found to give quite satisfactory results
Stresses in Branched Pipes under Internal Pressure
Authors:   Applied Mechanics Group, Fessler H. , Lewin B. H. 
Published: October 2007

The frozen stress photo-elastic technique was employed to determine the elastic stresses in T-shaped branched pipes. All branches had the same ratio of inner diameter to outer diameter as the main pipes and this ratio varied from 1/6 to 1/1 1/2. The ratio of branch diameter to main pipe diameter varied from 1/4 to 1. The peak stresses measured in 21 models of plain intersections showed no significant changes due to variation of branch diameter. External reinforcements in the form of collars, ‘Blair triforms’ and horseshoes were shown to be effective. Internal chamfers and counter-bores also reduced the peak stresses in thick pipes.
Acceleration and the Critical Heat Flux in Pool Boiling Heat Transfer
Authors:   Thermodynamics and Fluid Mechanics Group, Ivey H. J. 
Published: October 2007

Many theories predicting the critical (or burnout) heat flux in saturation pool boiling have been proposed during the past decade. Although most are able to correlate existing experimental data, it is evident that the theoretical models upon which they are based are widely different in concept. Moreover, owing to lack of experimental evidence it is not clear which, if any, are based upon the more correct models. Certain of the theories implicitly contain the acceleration due to gravity raised to a different power; by performing a relatively simple experiment it may be possible to accept or reject certain of the theories. An experiment of this type is described in the present paper. On the basis of the results of this experiment it is possible to reject several of the above theories. The extent to which the acceleration of the boiling system is important as a parameter in determining the critical heat flux was ascertained experimentally. A simple centrifugal apparatus is described which was used for determining the critical heat flux in pool boiling to water at atmospheric pressure and accelerations in the range 1 < ( a/g) < 160. A two-variable non-linear correlation involving a logarithmic transformation was made upon the experimental results after allowing for the possible effect of pressure and potential sub-cooling by extrapolation to zero subcooling. The resulting equation is of the form:
Operating Characteristics of Compound Engine Schemes for Traction Purposes Based on Opposed Piston Two-Stroke Engines and Differential Gearing
Authors:   Internal Combustion Engines Group, Wallace F. J. 
Published: October 2007

In an earlier paper (1)†, the performance characteristics of combinations of two-stroke compression ignition engines with compressors and turbines were analysed under the headings (1) Turbosupercharged engines with mechanically driven scavenge blowers, (2) Gas generators, (3) Compound engines with fixed ratio geared connection between engine., compressor, turbine and output shaft. The object of the present paper is to extend the method of analysis outlined in the previous paper to cover various compound engine arrangements with differential rather than fixed ratio gear connection between the members of the aggregate. It is shown that such units meet to a very high degree the specific requirements of the traction application, namely (1) High unit power achieved by the use of high boost pressures, (2) Torque-speed characteristics approaching the ideal hyperbolic law, and permitting drastic simplification of the external transmission system, (3) Good part-load efficiency—superior to both the turbocharged and the gas generator engine—made possible by free power flow between the members of the aggregate, (4) High degree of engine-assisted braking, and (5) Good response to sudden changes in load demand. Two arrangements, both meeting these requirements to a high degree, are considered. These units constitute a significant advance over existing traction prime movers.
Achievement of Clean Conditions in Gas-Cooled Nuclear Reactors
Authors: Anderson E. 
Published: October 2007

Precautions taken to ensure ‘clean’ conditions in the first civil nuclear power stations resulted in excessive costs and delays. These precautions are aimed at the elimination of materials which could poison the core, create a maintenance hazard, affect the fuel elements or increase the fire risk in the core. The present paper reviews the subject in the light of the considerable experience of constructing and running reactors now available, and an attempt is made to assess the importance of the various precautions.
The Project Method of Teaching Creative Mechanical Engineering
Authors: Hayes S. V. , Tobias S. A. 
Published: October 2007

An account is given of a scheme for teaching design-development engineering to undergraduates which has now been in operation since 1960 in the Department of Mechanical Engineering, the University of Birmingham. The essential feature of this scheme is that selected groups of final year students are engaged on the design of research and/or teaching equipment currently required in the Department. These designs are detailed by second-year students and are subsequently manufactured by them during their vacation employment in industry. The manufactured designs are taken back by them to the University to be developed in the first term of their final year. Following this, the equipment is either fed into the teaching or research activities or re-designed to start on a new cycle. Thus, the students concerned get direct experience of the complete design-production-assembly-development sequence. A description of the detailed working of the scheme, its organization and the experience gained in running it, is given. A number of completed designs are discussed. A detailed statement of the overall drawing-design teaching system is presented in Appendix I.
Job Evaluation
Authors: Norris A. Mc. C. 
Published: October 2007

Job evaluation is a technique which seeks to provide a logical basis for the setting of comparative pay rates. The methods used originated in America over 35 years ago and most job evaluation plans are adaptations of the three original ones described in this paper. A new technique has been evolved in Britain recently which is very akin to job evaluation but far more sophisticated in its approach. As far as is known, this technique has only been tried in a limited way at one firm so that only a brief mention is made of it, despite its obvious interest. Like a lot of other modern management techniques, job evaluation can do more harm than good unless human nature is taken into account. A man still wants to be regarded as a unique individual and so resents any attempt to fit him into a cold scientific pattern. Success in job evaluation, therefore, depends largely on the personalities of those responsible and on the creation of mutual trust between management and men.
The Pendulum Mill—A New Method of Rolling Metals
Authors: Saxl K. 
Published: October 2007

The Pendulum process is a new incremental rolling method for producing thin metal strip from thick plate. This is done in a single step, bypassing a sequence of conventional and often unproductive operations, such as process coiling, storing, annealing or cleaning. Rolling is carried out generally without preheating. The forces in the reduction zone are largely controllable and comparatively hard alloys can be rolled without overloading the equipment. The ingoing material is forced by feed rolls into a gap formed by converging paths of the work rolls which are moved backwards and forwards. The work rolls are freely rotatable, each being supported by two rows of backing rollers. The rolls are rotated solely by frictional contact with the strip and must remain loaded during the whole cycle. Deformation takes place during both strokes of the cycle. The limitations of the method are discussed and some results reported.
Nitrogen Oxides and Other Toxic Gases in Diesel Engine Exhausts
Authors: Middleditch H. 
Published: October 2007

The mode of production of carbon monoxide and of oxides of nitrogen and those aspects of combustion which control the formation of these gases in a diesel engine are examined. It is deduced that carbon monoxide production is principally a function of engine maintenance; on the other hand, there is an inherent characteristic for the production of oxides of nitrogen which can be ascribed to each engine design with the engine in standard trim. The characteristic oxides of nitrogen production for various engine designs will be compared and those aspects of design and operation which control this characteristic will be considered.
High-Reliability Servos: First Paper: Development of Redundancy Techniques for the Achievement of Highly Reliable Autocontrol for Nuclear Reactors
Authors: Lawrence L. A. J. 
Published: October 2007

Plant autocontrol systems are subject to failure; those occurring in autocontrolled nuclear reactors may necessitate a trip, with attendant economic penalties. Such failures may be avoided by designing autocontrollers which comprise a number of identical subsystems. The practical significance is discussed of some of the requirements for achieving high autocontrol reliability, and it is shown how these requirements have been translated into detailed design of hardware for a research reactor in which autocontrol of neutron flux and period is required. The underlying theme is that autocontrol of the plant can continue in spite of subsystem failure, but that careful vigilance must be exercised over the duration of the failure. Various devices are discussed which help to increase the efficiency of a redundant autocontrol system. Daily proof tests and passive monitoring devices can ensure that no relaxation of vigilance is allowed.
Second Paper: Failure-Survival Automatic Flight Control Systems for Aircraft with Particular Reference to a High Reliability Electrohydraulic Actuator
Authors: Ruggles R. 
Published: October 2007

The author discusses some of the problems of failure-survival automatic flight control systems and suggests some basic ground rules as design criteria. The advantages and disadvantages of some of the main types of system are discussed: duplex, triplex, triple component, duplicate-monitored and quadruplex systems being covered. In particular, a quadruplex actuator is described which has been designed and developed mainly for automatic flight control system applications where a very high degrees of failure-survival capability is required. A detailed failure analysis of the various systems is carried out and the importance of the electrical and hydraulic supply system configurations and failure rates is brought out.
Curing Instability in a Rotating Face Seal Control System: A Case History of the Application of Control Techniques in Mechanical Engineering
Authors: Tyler R. D. , Cooper B. J. 
Published: October 2007

The paper is a case history of the solution of a control problem in mechanical engineering. The system concerned, namely a pneumatic control system which regulated the leakage to the atmosphere of carbon dioxide through a rotating face seal, had exhibited the familiar symptoms of drift and hunting and had defied ad hoc methods to cure it. The difficulties stemmed from the fact that the gain of the element being controlled could assume indefinitely large values, whilst in addition, the loop contained one highly non-linear element. The solution of the problem did not require highly sophisticated techniques. In contrast, a combination of frequency-response testing and the application of quite elementary servo theory enabled the causes of the malfunctioning of the system to be pin-pointed and indicated the modifications required. Details are presented of the four phases of the investigation which comprised the initial frequency-response testing of the malfunctioning system, the theoretical analysis, laboratory tests on a simulator model of the system and final proving tests on the modified system at site.
Friction and Wear of Unlubricated Steel Surfaces at Speeds up to 655 FT/S
Authors: Earles S. W. E. , Kadhim M. J. 
Published: October 2007

The friction force between 1/8, 3/32 and 1/16 in diameter, and the wear of 3/32 in diameter, specimens of En 1A steel sliding on a disc of S62 steel are measured at speeds between 93 and 655 ft/s, the normal load on the specimen varying between 0.2 and 4.5 lbf. The coefficient of friction is shown to be dependent on sliding speed, normal load and specimen diameter, and to be a function of N1/2 U, where N is the normal load and U is the sliding speed. It is suggested that the coefficient of friction is dependent on the specimen contact surface condition which is dependent on the specimen surface temperature. There is evidence to suggest a gradual change in the mechanism of sliding with increasing magnitude of N1/2 U from, (i) metallic abrasion and tearing of an oxide layer, (ii) to skidding on and shallow ploughing of an oxide layer, (iii) to gliding over and shearing of a soft surface layer. It appears that the coefficient of friction is independent of, whereas specimen wear is dependent on, the disc surface condition. At low loads the material transferred from the specimen tends to form a continuous oxide layer on the disc., while at high loads there is the formation and tearing of a thick oxide layer, presenting a more abrasive surface to the specimen with a relative increase in wear. Generally specimen wear per sliding distance increases with N and decreases with U.
Military Requirement and Employment of Engineering Equipment
Authors: Egan T. H. , Mackay E. M. 
Published: October 2007

This paper is divided into two parts and covers two aspects important to the military engineer. The first part argues the case for military development of construction equipment. Its basis is the recent change of emphasis in military doctrine from the concept of general war in Europe towards that of limited war in more remote parts of the world. This makes air portability the most important but not the only parameter, and from this follows the paramount need for equipment of light weight, easy to break down to loads suitable for transport by helicopter, and as easily reassembled under field conditions. Military development is necessary because of these special requirements and in some cases because no commercial equivalents exist. The paper outlines the advantages and disadvantages of the ‘military special’ equipment, and Ministry of Defence (Army) policy regarding development of Engineering Construction equipment. It also suggests ways in which the commercial designer and manufacturer might help to make this policy effective without detriment to their product, and without attempting to design specifically for the military market, which is not an economic proposition anyway. The second part of the paper is the actual experience of its author in airborne engineer operations in Borneo. It discusses the equipment used, methods of getting it into and away from relatively inaccessible sites, and offers advice on training, packaging of ‘on-equipment’ spares, and aids to breaking down and reassembling plant for airlifted operations.
The Behaviour of the Impact Damper
Authors: Sadek M. M. 
Published: October 2007

In this investigation a theory is developed relating to the behaviour of the impact damper. The analysis is based on the assumptions that (1) two un-equispaced impacts per cycle occur in the steady state, and (2) the impact force-time curve is of rectangular shape and of infinitesimal duration. Fourier series are used to represent the impact cycle and the differential equation of motion is derived. This is solved using the dynamic equations of impact to determine the boundary conditions. Three equations are developed to determine the variation of impulse, phase angle and vibrational amplitude with the change of the damper parameters. Resonance curves are obtained and the theory is examined experimentally. The regions of validity of the above assumptions are studied both theoretically and experimentally. Non-linearity in the behaviour of this damper is very clear, especially in the range of its optimum behaviour. Two design curves are developed which can be used to determine the damper parameters necessary for a certain amplitude reduction.
Experimental Stress Analysis of Rails
Authors: Babb A. S. 
Published: October 2007

The paper describes the experimental stress analysis of a range of rail sections and a fishplated joint carried out by means of a loading frame which accommodated a short length of track, hydraulic jacks with load cells, and electrical resistance strain gauges. The most detailed test was that of the B.S. 110A rail which after being tested ‘as rolled’ was successively re-tested at states representing six stages of head wear, simulated by planing the rail head. The stress ranges determined under various loading conditions were compared with those for a bullhead rail planed to represent its known safe limit of wear and gave a guide to the permissible head wear of the B.S. 110A rail from stress criteria. The B.R. 116 lb/yd thick web rail was tested for comparison with the B.S. 110A, and rails representing three weights of the new B.S. A series were compared with three of the older B.S. R series rails of the same weights. From the test results various general conclusions have been drawn. The relationships between rail weight, head wear and fillet stresses, and the effect of different fastenings are discussed. A fishplated joint for 60 lb/yd rail was tested. The fillet, bolthole and bending stresses on the rail end, and the bending and bolthole stresses on the fishplates were determined. Although this is a light rail by modern main-line standards, the stress distributions and the conclusions drawn are believed to be typical of joints in heavier rail also.
Hydraulic Design of Syphons
Authors: Kelly A. G. 
Published: October 2007

This paper puts forward anew theory on the operation of syphons. It proposes, and gives proof from test results, that the rising leg of a syphon can be greater than heretofore thought (i.e. it can be greater than atmospheric pressure expressed in feet of the fluid being used minus the friction loss). It also shows that the length of the down leg of a syphon has no limit. Test results are given using heated water in syphons; having residence time near the apex; using water supplied off pumps. Pressures and vacua throughout syphons are also tested. It is shown that hydraulic gradient has no significance because the fluid stores energy in parts of some syphons; this matter is discussed in some detail. Other items discussed are friction factors to be used for syphons using water; noise in syphons; priming flows and parallel operation of syphons. It is shown that model tests for syphons have pitfalls. Lines for further investigation are indicated.
Thermometric Methods of Measuring the Rate of Mass Flow
Authors: El Agib A. A. R. 
Published: October 2007

By measurement of the unit-mass and the unit-time rates of exchange of energy between a flowing fluid and a heating or actuating source, the rates of mass flow can be directly determined, provided that certain thermodynamic properties of the fluid are known. Various methods of application of this principle are described and an account of proving tests is given. In these tests special techniques of precision thermometry were used. The results obtained were very promising and warrant further laboratory and field investigations.
Performance of P.T.F.E. Based Piston Rings in an Unlubricated Reciprocating Compressor
Authors: Hart R. R. 
Published: October 2007

Published data on the wear of non-metals is usually based on tests using a sliding disc on a rotating drum, with atmospheric air surrounding the equipment. Although this type of test gives a fair indication of the relative merits of the materials, it is impossible to accurately estimate the wear of piston rings under working conditions. Tests have therefore been carried out on various filled polytetrafluorethylene (P.T.F.E.) materials in an un-lubricated reciprocating compressor. The materials were tested as piston rings with helium as the working gas. The gas was used in two conditions: (1) ‘Wet’ where the moisture content was approximately 200 parts per million (p.p.m.) by volume. (2) ‘Dry’ where the moisture content was approximately 7 p.p.m. The fillers used were carbon, glass fibre and molybdenum disulphide and it was found that the carbon filled materials had the lowest wear rate in the wet gas. Using the dry gas the glass fibre filled materials gave the lowest wear rates. All the materials showed a tendency to local decomposition of the P.T.F.E. to carbon and fluorine and this is thought to be due to local hot spots formed by the relative movement of the ring in its groove.
Peat-Fired Boilers for Electricity Generation
Authors: Lang J. F. , Meyler J. J. 
Published: October 2007

The Electricity Supply Board of Ireland has been using peat-fired boilers for electricity generation for over 15 years. Peat is produced in two forms—sod and milled. Sod peat is burned on chain-grate stokers in boilers of up to 20 MW capacity; milled peat is fired as pulverized fuel in boilers of up to 40 MW capacity. Total peat-fired plant is 407 MW. Production methods for sod and milled peat are outlined. The paper describes the combustion technique adopted for these two fuel forms and the special maintenance and operational difficulties experienced over the years. The influence of peat characteristics on boiler design and the salient differences compared with coal and oil-fired boilers are explained. Details are given of performance and cost figures compared with coal and oil-fired plants.