bluuebunny/crossref_metadata_2025 huggingface dataset:
Compressible Gas-Flow in Commercial Pipes
Authors: Mills Brian , Cole B. N.
Published: October 2007

The main object has been to facilitate economic design of pipework for compressible flow; it being recollected that the cost of pipework in a given installation may not infrequently exceed the cost of compressor plant. It is found that the conclusion reached by Keenan and Neumann, namely, that compressible, subsonic flow in ‘smooth’ pipes is independent of Mach number and depends upon Reynolds number exactly as for incompressible flow, may be extended to commercial pipes of appreciable wall-surface roughness. While non-adiabatic flow is also examined, attention is mainly given to adiabatic flow; and various devices, tabular, graphical, and nomographical, are proposed to assist rapid estimation of such quantities as flow rate, pressure drop, maximum power transmitting capacity, etc.

Encouraging correlation is found to exist between directly measured wall-surface roughness, as represented by the British Standard centre-line average index, and roughness as expressed hydrodynamically by the equation of Colebrook and White. This points to the practicability of predicting the flow characteristics of large pipes, for which flow tests may be difficult until in situ, by surface measurement alone.
Photo-Elastic Investigation of Stresses in the Heads of Thick Pressure-Vessels
Authors: Fessler H. , Rose R. T.
Published: October 2007

The frozen stress photo-elastic technique is used to study the stresses in four different shapes of full drumheads and in five drumheads with circular or elliptical manholes. Circumferential and meridional stresses on inside and outside surfaces are presented, and some of these are compared with stresses calculated from different thin shell theories. These theories were modified to be more realistic for thick shells by considering the pressure to act on the inside instead of the middle surface of the shell. The wall thickness of every drum was one-tenth of the mean diameter of the drum.

The effect of large elastic strains was studied by means of two identical models tested at different pressures. Calculations showed that the stresses were slightly decreased when Poisson's ratio was changed from 1/2 to 1/4. The effect of a reduction of the wall thickness of hemispherical heads was calculated and was found to be in good agreement with experimental results. The stress distribution in the walls of the shells was also determined for some critical sections.
Diesel Engine Lubricants: Their Selection and Utilization with Particular Reference to Oil Alkalinity
Authors: Dyson A. , Richards L. J. , Williams K. R.
Published: October 2007

The main functions of heavy-duty lubricating-oil additives are to control engine fouling, bearing corrosion, and wear of liners and piston rings. Alkalinity is desirable for the control of wear and is one of the major requirements for the avoidance of piston fouling when conventional organo-metallic additives are used. In a well-balanced oil, sufficient dispersive power and oxidation stability may be incorporated to ensure adequate piston cleanliness and freedom from bearing corrosion provided that the alkalinity level is satisfactory.

The alkalinity level falls during service, and for satisfactory performance with certain types of additive in common use it must be kept above a minimum value. For these additives equations are given which enable the variation of the alkalinity level with time in given circumstances to be predicted approximately. The most satisfactory arrangement is to use an oil containing sufficient alkalinity so that the concentration never falls below the critical value. The oil-change period is then determined by other considerations, for example, contamination with abrasives. If an oil of lower alkalinity-concentration is used, then the equations developed permit an approximate estimate of the oil-change period, determined solely from the aspect of additive effectiveness. The application of these results to engines with separate cylinder lubrication is discussed.

Thus oils, and, where appropriate, oil-change periods, may be selected on a rational basis instead of by trial and error.
Thermodynamic Study of the Number and Positioning of the Feed Pumps in the Feed Train of a Regenerative Steam Cycle
Authors: Haywood R. W.
Published: October 2007

In this paper an approximate method of analysis is developed to compare the performance of single-pump and split-pump schemes in the non-reheat regenerative steam cycle. The analytical result is shown to agree closely with figures obtained by detailed calculations based on the same standards of comparison of the two schemes as those used in the approximate analysis, although on an alternative basis of comparison the calculated difference between the performances of the two schemes is smaller. The study reveals, however, that on either basis of comparison the efficiency of the cycle is slightly greater for the split-pump arrangement. Detailed calculations for a typical reheat cycle show the same tendency. It is concluded that, on the score of both thermal efficiency and capital cost, the split-pump arrangement is to be preferred.
Journal Bearing Performance for Combinations of Steady, Fundamental and Harmonic Components of Load
Authors: Shawki G. S. A.
Published: October 2007

The performance of a complete journal bearing is obtained for a vertical cyclic load of the form

It has already been established that the ratio of the rate of load application to that of journal rotation (ω1/ω) is a prime factor in the bearing behaviour, and for the case where Pn = 0, values of this ratio slightly less than 0·5 were found to give rise to critical changes in the bearing performance depending on the ratio P1/ P0.

Present test results show that the superposition of the harmonic load component Pn would, in general, bring some changes to the performance characteristics at the ω1/ω value corresponding to this harmonic, that is, at nω1/ω ⋍ 0·5, and some simultaneous related changes (in the opposite sense) at the ω1/ω value corresponding to the fundamental component P1, that is, at ω1/ω ⋍ 0·5, the extent of these changes being a function of the amplitude ratio Pn/P1.

The phenomenon is explained in the light of the theory of vibrations, and the analysis is extended to include the case of a variable load on a uniformly rotating journal.
Unsteady-State Heat Transfer to and from Gases in Laminar Flow
Authors: Patten T. D.
Published: October 2007

In this investigation of the problem of unsteady-state heat transfer to and from gas, experiments have been carried out with the flow of air through a passage of circular cross-section. Heat transfer takes place within a single vertical tube, around which is an annular guard space. Because of the magnitude of heat losses at lower values, the investigation is confined to values of Reynolds number between 1,000 and 2,500. Within this range, at moderate temperature differences, the processes of heating and cooling of gases reveal similar heat-transfer properties. When the tube wall-temperature is either constant or has a uniform temperature gradient, it is shown that the Nusselt number is in agreement with that predicted for steady-state heat transfer for the same wall-temperature distribution.

The investigation deals with single-cycle operation referred to as ‘single blow’, in which the supply is either hot or cold, and with cyclic operation as a parallel flow regenerator. Heat-transfer coefficients obtained from the cyclic operation tests are of the same order as those from the single-blow tests.

An analytical expression for the prediction of outlet temperatures, assuming a varying supply inlet-temperature and non-uniform initial wall-temperature, is presented and this is used in the calculation of the single-blow results.
Stress-Relaxation Behaviour of Chromium-Molybdenum and Chromium-Molybdenum-Vanadium Bolting Materials
Authors: Stafford J. A. , Gemmill M. G.
Published: October 2007

The object of this paper is to illustrate by means of a series of tests made on two steels, the essential differences between testing under constant load, constant total strain, and a commonly used ‘weighbar’ method that is intermediate between these two. It shows that the constant strain results do not entirely support the strain-hardening and time-hardening theories suggested by other authors. An empirical relationship, which gives reasonable correlation in the ranges of stress, temperature, and time examined, is given as an aid to analysing the results, but no correlation of this with a theoretical approach has been found, though it is hoped that it will contribute to the eventual solution of this problem.

Suggestions are finally made as to how relaxation data may be used for design purposes with reference particularly to the choice of an initial stress and the value of retightening.
Part I: Development of a Testing Machine
Authors: Davis A. J. , Krok T. V.
Published: October 2007

A machine has been developed for the investigation of sleeve bearings operating in the transition range between full fluid and boundary lubrication. Results of some tests are given.
Recent Developments in the Manufacture of Castings
Authors: Rice J. L. , Ruddle R. W. , Russell P. A.
Published: October 2007

Developments which have taken place in the last decade in foundry practice and in the alloys used to make castings are described. The main emphasis is on the effect of these developments on the soundness, mechanical properties, dimensional accuracy, and the cost of the finished casting, and less on the way the improvements have been brought about.

The topics discussed are: (1) the development of new and established processes; (2) alloy development; (3) inspection; (4) future trends.

The paper is confined to cast iron and non-ferrous alloys; advances in the production of steel castings have not been covered. Many of the techniques referred to, though, are of general applicability.
Test Bed Installations and Engine Test Equipment
Authors: Freeston H. G.
Published: October 2007

As well as meeting the functional needs of the tests required, an installation for testing engines should, also provide a satisfactory environment for operating personnel. Nuisance or disturbance to persons or apparatus in the vicinity must be avoided.

Consideration is given to the requirements of heating, ventilation and acoustic treatment of the test room and the provision of services. The test bed arrangements are dependent on the kind of work to be undertaken.

The test bed equipment required includes dynamometers and instrumentation for the various phenomena to be measured. Many tests can be made without personnel in attendance by the use of automatic operating equipment and recorders, provided safety devices are fitted.

The simulation of service conditions gives rise to interesting problems for the equipment engineer.
Experimental Studies of the Mixing Processes and Flow Configurations in Two-Cycle Engine Scavenging
Authors: Rizk W.
Published: October 2007

The paper describes work carried out at various stages during the period 1944–54 and indicates the need for a new approach in the study of the scavenging process in two-stroke engines. Its main object is to outline various ways of studying the main features of the scavenge flow within the cylinder as distinct from the gas dynamics of the charging process. By using a special photo-electric cell probe in a scale model and determining the change in purity of the stream at any point it was possible to examine the basic characteristics of scavenging flow and consider the process as taking place in broadly three phases. The first of these, entailing the formation and development of the inlet jets, has been studied in a preliminary way with the aid of a colour reacting technique to show the mixing region together with the undiluted core of a jet starting from rest. This has thrown light on the rate of mixing in the initial phases of scavenge flow and has indicated the possibility of achieving higher efficiencies by a reduction in the size of inlet ports and an increase in their number.

An experimental study carried out on a loop-type system has shown that the flow configuration can be substantially different from that usually assumed and that flow instabilities could occur leading to partial short-circuiting of the flow. Photographic records of the flow and the major axis of rotation under various conditions have been obtained and assist in showing qualitatively the effect of altering the angles of entry of the jets. It is further shown that under certain conditions an increase in the inlet air flow could nullify any gains in scavenging efficiency. End-to-end scavenge systems are also discussed, indicating the need for further study of some of the major parameters governing the flow.
The Application of Servo-Mechanism Analysis to Fuel Control Problems
Authors: Lawrence J. O. N. , Powell R. D.
Published: October 2007

The paper gives details of the way in which servo-mechanism techniques have been applied to accessory control problems. The emphasis has been on the correlation of theory with practice and typical results are given from tests on some 15 British gas-turbine engines. For completeness a brief introduction to the basic concepts is first dealt with, then examples are given of linear and non-linear theories applied to typical working systems.

It is pointed out that though the examples refer to hydraulic, mechanical, and thermodynamic processes the ideas may be carried forward into widely differing fields.
Glands for the Entry of Electrical Cables into Pressure Vessels Containing or Surrounded by Conducting Liquids
Authors: Grunwald H. H.
Published: October 2007

It is often required to house electrical apparatus in pressure vessels capable of withstanding considerable pressure, either external or internal, and to make connection with such apparatus. For this purpose, electrical cables containing one or more insulated conductors must be passed through the walls of the vessel. This paper deals with glands forming the entry of such cables into the vessel.

It states the fundamental requirements of cable entry glands and gives a summary of the principles of construction employed. Experimental work is described which led to the development of two designs of gland. The first of these was developed specifically for the entry of submarine telecommunication cables into submerged repeaters containing electronic amplifying equipment, in particular the submerged repeaters used on the British section of the first transatlantic telephone cable system. Both manufacture and testing of these glands are reviewed. The second design dealt with is a simplification of the first, based on the experience gained.

Some special operating conditions encountered are mentioned and the means of meeting the resulting additional requirements are discussed.
The Design and Construction of the Compressor for the 8 ft by 8 ft High-Speed Wind Tunnel at R.A.E. Bedford
Authors: Cheshire L. J. , Evans J. Y. G. , Goodsell W. A. , Wolff P. H. W.
Published: October 2007

The paper, which is in two parts, deals with the steps taken to meet the specified performance and conditions of operation of the compressor for the 8 ft x 8 ft high-speed wind tunnel at Royal Aircraft Establishment (R.A.E.) Bedford.

The essential requirements were that the compressor should deliver a quantity differing not greatly from 50 000 ft3/s over a range of pressure ratio 1.15 to 2.50, an important proviso being that special steps must be taken to achieve high efficiencies in the lower range of pressure ratios.

Part I deals with the reasoning which led to the adoption of the final design solutions, and the supporting experimental work including the manufacture and testing of a 1/7 scale aerodynamic model necessary to establish the performance characteristics of the compressor before deciding the final blade settings. It was decided to build a ten-stage compressor to run at 750 rev/min having a first-stage blade tip diameter of 17 ft with a blade 2 ft 6 in. long. In order to meet the requirement of good efficiency over the whole working range, the compressor was divided into two parts so that under low pressure ratio conditions only the first four stages are in the circuit, the change from 10 stage to 4 stage operation and vice versa taking place in under twenty minutes.

Part II describes the mechanical features and manufacturing processes following from the design decisions given in Part I.
The Mechanical Design of an Experimental Plant-Type Gas Turbine
Authors: Whitehead L. T.
Published: October 2007

Problems of thermal expansion and insulation encountered in the structural design of steam turbines are accentuated in gas turbines owing to their generally higher operating temperature.

This paper describes the construction of a four-stage 8000-b.h.p. gas turbine designed and manufactured at the National Gas Turbine Establishment, and embodying several features offering a solution of these problems.

A tubular rotor reinforced by radial discs is required if material is to be used with economy and, in addition, the rotor must be maintained at a temperature which allows full use of the material properties. Heat should be confined as closely as possible to the gas flow annulus to obtain the maximum output of work from the blading and to avoid undesirable thermal stress in the rotor.

The insulation of the bearings and the provision of some flexibility between these and the shaft to meet the possibility of damage from excessive heat soakage in an emergency is also important.

The methods used to attain the above objectives include rotor discs connected by threaded side-rims of large diameter and cooled by an axial flow of air under the blade roots.

Flexible sleeves are fitted between the shaft journals and the roller-type bearings, to inhibit heat flow and to accommodate differential radial expansion.

The stator casings are treated as gas-carrying ducts, relieved of mounting constraints and bearing alignment duty by being freely mounted on radially disposed pegs and keys giving freedom for thermal expansion in all directions.

Preliminary experiments and rig tests on the bearing mounting sleeves, and on surface treatment to prevent seizure of the screw-thread connections between the rotor discs are described.

More than usual attention is given in the design to methods of facilitating inspection and maintenance, and provision is made for replacing individual rotor blades and bearings without separating rotor and stator.
Behaviour of Thick-Walled Steel Cylinders Subjected to Internal Pressure
Authors: Crossland B. , Bones J. A.
Published: October 2007

In this paper the literature on the strength of thick-walled cylinders subjected to internal pressure is reviewed and equations are given which enable the initial yield pressure, collapse pressure, and ultimate pressure to be calculated from shear stress-strain data. Pressure tests on thick-walled cylinders made from 0.15 per cent carbon steel, 0.3 per cent carbon steel, and Vibrac steel are described, the maximum pressure reached being 42 ton/in2. For 0.15 per cent carbon steel results of tests on cylinders with a ratio of outer to bore diameter of up to 8.05 are given. Numerous tensile and torsion tests have been carried out on these steels and these are fully reported.

For the 0.3 per cent carbon steel which was tested first no measurements were made of initial yield and collapse pressures. The results for the 0.15 per cent carbon steel, however, show good agreement with the calculated values if allowance is made for the influence of shear stress gradient when computing the initial yield pressure. With Vibrac steel the experimental results lie between the two curves computed from the extreme shear stress-strain curves. The experimental pressure-expansion curves at large strains and the ultimate pressures for the three materials all agree very well with the computed values. Values of the ultimate pressures have also been calculated from several empirical equations but they all give considerable errors, though up to a diameter ratio of 4 the mean diameter formula is satisfactory.
The Plastic Flow and Fracture of a ‘Brittle’ Material (Grey Cast Iron) with Particular Reference to the Effect of Fluid Pressure
Authors: Crossland B. , Dearden W. H.
Published: October 2007

This paper describes tests carried out on a ‘brittle’ material in the form of grey cast iron to investigate the criterion of plastic flow and ultimate failure, and in particular torsion tests carried out with superimposed fluid pressures of up to 35 ton/in2.

It is suggested that the results show that the mode of failure is dependent on the volumetric stress acting. For volumetric compressive stresses greater than approximately zero, failure occurs at a critical value of the shear stress, a value which is some function of the volumetric stress. At small or negative values of the volumetric compressive stress failure occurs at a critical value of the maximum tensile stress, a value which may be slightly dependent on the volumetric stress.

The shear stress-strain curve is apparently also related to the volumetric stress, and the shear stress-strain curve deduced from a compression test on the shear-stress hypothesis coincides with that found from a torsion test carried out under a pressure approximately equal to the volumetric stress in the compression test.

In torsion the strain to failure is raised by pressure; the rate of change of strain with pressure being considerably increased when the fluid pressure is sufficient to suppress completely any tensile component of stress. The strain to failure in compression is greater than in the comparable torsion tests, but this may be explained by the weakening effect of the fluid or the rubber protective film when they are forced into incipient cracks.
Graphical Method of Calculating Heat Transfer, Condensation, and Vaporization Rates in Processes Involving Water-Steam-Air Mixtures
Authors: Spalding D. B.
Published: October 2007

The properties of a plot of the isotherms and phase boundaries of water-steam-air mixtures on an enthalpy-composition diagram for constant total pressure are shown to permit graphical constructions enabling surface conditions, heat and mass transfer rates, and equipment size to be deduced for convection, steam-drum and radiant drying plant, cooling-towers, condensers, gas coolers and trickle coolers. A chart for atmospheric pressure calculations is presented, together with data from which charts for other pressures may be simply calculated. The graphical method may also be applied to other systems involving phase changes.
Three-Dimensional Flow in Axial Pumps and Fans
Authors: Mikhail S.
Published: October 2007

This paper describes a research† carried out in the Hydraulics Laboratory of the City and Guilds College, Imperial College, London. Three-dimensional flow in non-free-vortex axial pumps and fans was studied. A rigorous solution of the linearized partial differential equation that describes the flow in non-free-vortex machines was developed. The solution determines the stream surfaces of the mean flow for the case of a thin rotor disc. Two series of machines were tested and the results were used to check the validity of the theoretical analysis.

The practical aspects of the possibility of using non-free-vortex flows in the design of axial machines were also studied.
Strength at Elevated Temperatures of Aluminium and Certain Aluminium Alloys
Authors: Inglis N. P. , Larke Eustace C.
Published: October 2007

The materials examined were a 99.5 per cent aluminium, the 2 1/4 per cent magnesium alloy to B.S. 1476: 1955 NE4, the 3 1/2 per cent magnesium alloy to B.S. 1476: 1955 NE5, a 1 1/4 per cent manganese alloy and the magnesium-silicide alloy to B.S. 1476: 1955 HE30, all being in the form of extruded rod. Excepting for the HE30 alloy, which was fully heat-treated, all tests were carried out with the material in the as-extruded condition.

Short-time data covers a temperature range of 20°-250°C, the stress-rupture curves, which mostly extend up to 10 000 h, relating to temperatures of 100°, 150°, 200°, and 250°C. Creep tests, a number of which were taken into the tertiary stage, have been carried out at 200° and 300°C for the 1 1/4 per cent manganese alloy and temperatures employed for the HE30 alloy were 100°, 150°, and 200°C. Stress-rupture tests still in progress and creep data for the remaining three materials will be reported in an addendum.

Stress-temperature curves are plotted which enable a direct comparison to be made of the effect of temperature on rupture strength for specified amounts of time.

The paper concludes with a fairly detailed report of the effect of time, stress, and temperature on the microstructure and discusses the types of fracture encountered.
Mechanical Marshalling of Railway Wagons in Works Sidings
Authors: Grossmith G. W.
Published: October 2007

The methods employed for the movement of railway wagons in works sidings have changed very little in 50 years, probably because appliances lending themselves to mechanization were not available. Locomotives, capstans, and winches are unsuitable for combination under centralized or automatic control, owing to their need for men on the locomotives and also on the sidings to handle towing ropes and to work the wagon brakes. Free-running gradients have, owing to the greatly varying running characteristics of wagons, been too uncertain to give sufficiently consistent results.

In recent years a number of new appliances for the remote propulsion, braking, and general control of wagon movements have been developed, suitable for employment separately or in combination according to the needs of the problem. The new devices may be broadly classified as mules, track brakes, arresters, traversers, and remotely controlled locomotives.

The development of these devices has made possible, and in fact has brought about, new techniques and simpler systems of sidings layout, with economy in cost and great economy in space occupied. In this paper, these recent developments are first described separately, and examples are then given showing how they can be, and have been, applied in combination under centralized control.

Wagon marshalling as dealt with by this paper means the remote control or automatic control of a succession of wagon movements in works sidings without the need for application of the wagon brakes at any stage. The main railway marshalling yards are excluded from this review as the problems are, in their case, different.
Induction Ramming of Small High-Speed Air Compressor
Authors: Bannister F. K.
Published: October 2007

The paper describes an investigation of the effects of piston-excited pressure waves in the plain induction pipe of a small, high-speed, single-cylinder air compressor. For a range of pipe lengths and diameters, compressor speeds and delivery pressures, the observed compressor throughput and driving torque are compared with those obtained with no intake pipe fitted. Based on classical laws of wave motion but using an experimentally obtained steady-flow characteristic for the inlet valve, a theoretical treatment is developed to describe the pressure pulsations in the inlet port and cylinder and to predict the change in airflow resulting from the fitting of any particular intake pipe. Experimentally recorded indicator diagrams compare satisfactorily with those predicted theoretically and similar agreement is obtained between the experimental and theoretical values of airflow. An 18 per cent increase in airflow is reported.
A Theoretical Analysis of the Response of a Loaded Hydraulic Relay
Authors: Butler R.
Published: October 2007

This paper is divided into four sections dealing with the response (both velocity and displacement) of a loaded hydraulic relay to Part I step function, Part II ramp function, Part III sinusoidal input, and Part IV general input. In Part IV equations of motion are developed for any variation of the input valve and these include a viscous-damping term and first-order contributions due to oil compressibility and leakage past the ram. The relay with feedback linkage is treated and parameter limits are established for normal (cavitation-free) motion. The remaining sections analyse the system in turn for the various inputs by solution of the equations of motion, but with increasing restrictions. In Part II methods are given for extending the case to linear closing of the valve and a delta function input. Valve overlap is briefly introduced in Part III. Cavitation criteria in terms of general non-dimensional parameters are developed in all sections. Many results are presented graphically or in tabular form, the mathematics being reserved for appendices whenever possible.
Experiments on Two-Stroke Engine Exhaust Ports under Steady and Unsteady Flow Conditions
Authors: Benson R. S.
Published: October 2007

A theoretical and experimental study of the discharge from an engine cylinder to atmosphere was made. The objective of the work was to establish suitable data for the design of exhaust ports. Two theoretical methods were used, in the first method the discharge was analysed by the method of characteristics and it was shown that the discharge was by wave action. The second method neglected the particle velocity in the cylinder. Comparison of the latter method with the solution by characteristics showed good agreement over the main part of the discharge and it was possible by that method to develop a simple design formula for the estimation of the port area.

The experimental investigation was carried out on a special machine which simulated in all respects the exhaust-port arrangement of a two-stroke cycle engine. The machine was designed to investigate the effect of port configuration, port timing, cylinder length, engine speed, release pressure, and temperature. By suitably arranging the variables in non- dimensional groups a wide range of engines could be simulated. The flow characteristics of the exhaust ports were examined under both steady and unsteady flow conditions. The following conclusions were drawn: (1) the coefficient of discharge for the exhaust ports increased with cylinder pressure and decreased with increased port area, (2) the coefficient of discharge was lower under dynamic conditions than under steady flow conditions, (3) the dynamic coefficient of discharge decreased with reduction in cylinder length at release, (4) the effect of early port opening was to reduce the blowdown time, (5) the effect of piston movement during discharge was to reduce the effective port area required.
Governing of Compression-Ignition Oil Engines
Authors: Welbourn D. B. , Roberts D. K. , Fuller R. A.
Published: October 2007

In this paper is discussed the application of some of the concepts of modern control theory to the problem of the governing of compression-ignition engines. A physical description of the problem is given, illustrated by measurements made on governors and engines, including some to show the effect of the finite-time intervals between successive firing strokes, and other non-linearities such as Coulomb friction. In Appendix I is discussed the setting up of the equations of motion of mechanical systems, and their solutions using vector methods and the inverse locus to find the stability and also the transient responses of the system. While none of the theory will be novel to control engineers, part of its presentation may be. Some experimental data obtained on medium-size engines are included, together with comments on their use and some details on the investigation of unstable engine-governor systems. A large saving in test-bed time is reported.
Mechanics of Orthogonal Machining
Authors: Palmer W. B. , Oxley P. L. B.
Published: October 2007

In an attempt to overcome the deficiencies of existing theories of cutting, an experimental technique was developed for observing the cutting process during slow orthogonal cutting of mild steel. An attempt to find consistency between the observations and the ideal theory of plasticity failed. Consequently the theory was extended by including the effect of work- hardening and, in spite of the laborious nature of the analysis, it appeared that consistency had been regained. This led to a novel and physically consistent picture of the cutting process, which was taking place during the tests.
Effect of Nuclear Radiation on Engineering Materials
Authors: Cottrell A. H.
Published: October 2007

The importance of radiation damage in materials for use in nuclear power reactors is emphasized and an account is given of various types of radiation damage in such materials. The displacement of atoms by nuclear radiation is briefly discussed and examples are shown of recent electron microscopical photographs of radiation damage in materials. A discussion is given of radiation damage in graphite and the importance of stored energy as a reactor problem. The effect of displaced atoms in producing radiation hardening in metals and radiation embrittlement in structural steels is emphasized and discussed in relation to reactor pressure-vessels. Problems of growth, wrinkling, creep, and inert fission gases in uranium are considered in relation to the life of reactor fuel elements.
Sealing Characteristics of Stuffing-Box Seals for Rotating Shafts
Authors: Denny D. F. , Turnbull D. E.
Published: October 2007

There are two distinct modes of operation of a stuffing-box seal. One mode occurs when the axial pressures produced in the packing by tightening the gland-bush are greater than the sealed fluid pressure and the other when they are less. Under the former conditions the fluid pressure distribution is an exponential function of the packed length and the frictional torque increases rapidly with this quantity. With high fluid pressures, however, the relation between fluid pressure and packed length is no longer exponential and most of the fluid pressure drop occurs over the last 10 per cent of the packed length. In addition very little increase in frictional torque occurs when the packed length is increased.

Theoretical expressions have been derived for pressure distribution and friction torque and good agreement has been obtained between these and experimental results.
Flash Evaporators for the Distillation of Sea-Water
Authors: Frankel A.
Published: October 2007

The thermodynamic principles on which the flash evaporator operates are described and some of the reasons for the recent emergence of this type of distillation plant are explained. It is shown that the performance of a flash evaporator is much less dependent on the number of stages used than is the case for a submerged coil unit. The thermodynamic losses involved in using a finite number of stages, and the effects of other losses which are unavoidable in practice, are described and assessed.

The actual designs of evaporator vessels are described showing means of avoiding interstage piping or ducting despite the use of a large number of stages.

Reference is made to two large-size test rigs built to confirm the basic ideas underlying the development. One was devoted to the exploration of deposition problems and the measurement of heat-transfer data, while the other test rig was used to develop various methods of separating moisture from the vapour produced in the evaporator, and to investigate the flashing-off process. Some of the test results achieved on the rigs are described.
Operation of Rolling-Element Bearings in a Protective Atmosphere
Authors: Cattaneo A. G. , Coit R. A. , Sorem S. S.
Published: October 2007

To operate at high temperatures, up to 1100°F, bearings must be protected against two sources of early failure: formation of red rust by oxygen attack on the surfaces in either rolling or sliding contact, and rapid wear by local seizure (scuffing) of the cage surfaces in sliding contact with other elements. The first function can be filled for all-ferrous bearings by an atmosphere consisting of a mixture of air and an organic vapour which acts as a reducing agent at elevated temperatures. The performance of the second function requires constituents or additives that form anti-scuffing films.

An olefine oxide polymer was found to be a satisfactory reducing agent over the whole temperature range. Conventional extreme pressure (e.p.) additives are effective in preventing scuffing up to about 900°F. Above 900°F the polymer forms an organic film which itself gives some protection against scuffing. Size 206 tool steel bearings have been operated for 100 hours at 1000°F, 10 000 rev/min under considerable radial and axial load; and for 22 hours at 1100° F. With the bearings available thus far, maximum loads are dictated by softening of the metals above 900°F.

These high temperatures create special problems in the design of the test equipment with respect to fits, warping and dimensional changes. The rig and procedures used in this work are described.
Investigation into the Reasons Causing Explosion in Steam Tubes of Bakers' Ovens
Authors: Moorhouse W. E.
Published: October 2007

The number of explosions and failures in steam tubes of ovens remains extremely high, and measures for a reduction of this number are overdue. The lack of safety controls is the main reason for the majority of these accidents, and it is usual, following an explosion, to state that the tube was ‘overheated’. Experimental results or data on metal temperatures on enclosed steam tubes do not appear available, and this paper embodies experimental results in this direction. A great deal of further research is necessary and should be carried out.
Stick-Slip Friction as a Cause of Torsional Vibration in Textile Drafting Rollers
Authors: Catling H.
Published: October 2007

Torsional vibration of long rollers stimulated by stick-slip frictional behaviour constitutes a problem in the drafting of fibrous textile materials. A study of the behaviour of long rollers, including the measurement of the periods of stick and slip during vibration is described. With the object of finding a combination incapable of maintaining stick-slip vibrations the detailed frictional behaviour of a number of bearing materials and lubricants was investigated and a laboratory instrument was made to simulate service conditions and indicate the liability to stick-slip vibration of single bearings. Good correlation was observed between the liability to vibration of single bearings in the tester and the performance of multiple bearing assemblies in service. No completely satisfactory solution has been found, although many combinations have been tried.
Influence of Exhaust Belt Design on the Discharge Process in Two-Stroke Engines
Authors: Benson R. S.
Published: October 2007

The paper describes an investigation of the influence of belt design on the discharge process of a two-stroke cycle engine. Theoretical methods are developed for calculating the pressure changes in the cylinder, exhaust belt and pipe. A comprehensive experimental investigation of ten exhaust-belt configurations is then described. Pressure measurements were taken in the cylinder, belt and pipe. The experiments showed that the pressure was not uniform within the belt and decreased from the belt to the pipe. It was shown that an increase in belt size reduced the restrictive effects of a belt, shortened the blowdown time and increased the pulse amplitude in the exhaust pipe. There was an optimum belt size above which no further improvement was obtained unless the belt profile was altered, at this size the belt could be made within the normal engine dimensional limits. Data are given for designing exhaust ports and belts based on these experiments. The detailed development of the boundary equations for the gas exchange process is given in an appendix.
An Investigation of the Plug Drawing Process
Authors: Blazynski T. Z. , Cole I. M.
Published: October 2007

The object of this work has been to obtain agreement between the existing theory of tube drawing with a plug, and experimental results, and thus to be able to predict the behaviour of the metal when conditions of drawing are altered. As the basis of theoretical study Sachs's approximate theory has been chosen, and mild steel containing 012 per cent carbon has been used as the test material.

The use of the theory requires the knowledge of the true mean yield stress of the metal undergoing plastic deformation, as well as that of the value of the coefficient of friction. The method of establishing those two quantities is discussed in detail. Drawing stresses are calculated and it is shown that close overall agreement exists between theory and practice and that, therefore, the mathematical formulae can be used with confidence. The components of the total work done in drawing a tube are determined and discussed, and the adverse effect of sink on the magnitude of redundant work is indicated.
Maximum Reduction in Cold Strip Rolling
Authors: Avitzur B.
Published: October 2007

An analytical equation is derived for the prediction of maximum reductions possible as dependent on the process variables. The results of this equation are presented in graphical form for a wide range of the process variables. A simple experimental procedure is suggested for the determination of the coefficient of friction.

The process variables are: The roll radius R0, initial t i and final t f strip thickness, material yield limit σ0 at uniaxial tensile test with yield limit σoi at initial thickness and σo f at final exit thickness, front pull stress σxf and back pull stress σxb, the coefficient of friction μ, and the rolling speed U.

The power balance is set for the rolling operation. The powers computed are:

(1) the useful power consumed as internal work of deformation of the strip, called sometimes ‘The homogeneous power’; (2) power consumed by the back pull on the strip; (3) power supplied by the front pull on the strip; (4) power consumed by the friction between the rolls and the strip; and (5) power supplied by the rolls.

From the equation: sum of the powers = 0, a dependence of the process variables one on each other is established. From this dependence the coefficient of friction can be computed at maximum reduction, and this gives a simple procedure for the experimental determination of the average coefficient of friction. With the coefficient of friction, yield limit, dimensions of the strip and roll and the values of the front and back pull known, from a given graph the maximum reduction possible can then be computed or picked.
Pulsation Damping Systems for Large Reciprocating Compressors and Free-Piston Gas Generators
Authors: Wallace F. J.
Published: October 2007

The pulsation problems inherent in installations comprising large and relatively slow speed-reciprocating compressors or engines, both on the induction and delivery side, have been recognized for many years. The problem of pulsating flow has recently become particularly acute with the large-scale introduction of free-piston gas generators which, because of their unique mode of operation and the fact that they are usually installed in groups drawing from a common air manifold and delivering to a common exhaust duct, are particularly sensitive to such pulsations and where a rigorous approach to the problem is imperative. The present paper is concerned exclusively with intake systems which usually consist of two distinct elements, namely the individual damping system for each gas generator and a common ducting system for the entire group of gas generators, from which the individual damping systems draw their air supply. The individual damping systems take the form of one or two large smoothing chambers or damping capacities connected by Venturi-shaped ducts to each other (when two chambers are used) and to the common ducting system, the gas generators drawing air from these smoothing chambers through pipes which may be arranged to give some ram effect with resultant improved volumetric efficiency. The object of the individual damping systems is to ensure that the magnitude of the pulsations reaching the common ducting system is sufficiently low to prevent harmful pulsations which could cause damage to air filters, or even to property in the vicinity, particularly if resonances are excited in the common ducting system.

A typical intake system for an eight gas generator installation is shown in Fig. 1. The paper is concerned solely with the method of analysis applicable to the individual damping systems, not with the external ducting system. The latter should present no difficulties if the individual systems are properly designed. The method of analysis is based on mechanical vibration theory, the governing equations for the damping systems—conveniently referred to as acoustic systems—being identical with those of better known mechanical systems. The equivalent electrical systems are given in an appendix, with a view to facilitating the analysis of damping systems with the aid of analogue computers. The object of the analysis is first to put the design of such damping systems on a sound theoretical basis and secondly to facilitate the calculation of optimum dimensions, given permissible pressure drop and pulsation amplitude outside the system, as well as the form of the suction pulse of the gas generator. The latter is most conveniently represented as a harmonic series using Fourier analysis.

The present paper is based on the author's own experience in this field and, though restricted to purely theoretical considerations to avoid excessive length, the material contained in the paper is confirmed by a substantial body of experimental work.
Autofrettage of Cylinders: Prediction of Pressure/External Expansion Curves and Calculation of Residual Stresses
Authors: Franklin G. J. , Morrison J. L. M.
Published: October 2007

The shear stress-strain relationship for an initially stress-free 2 1/2 per cent nickel-chromium-molybdenum steel under reversed stress has been determined by twisting thin tubes. The effect of a low-temperature heat treatment given to this material after various amounts of overstrain has been similarly determined.

The information so obtained has been used to calculate by methods outlined in Appendixes I and II the behaviour of thick cylinders of the same material when subjected to one or two cycles of internal pressure, with or without an intervening low-temperature heat treatment, and to calculate the stresses throughout the material of these cylinders at any stage in the processes.

Such cylinders have been made and subjected to the treatment described, the pressure and dimensional changes being measured at all stages. They have then been bored out in steps until all the overstrained material has been removed, the corresponding dimensional changes being again measured.

One of the assumptions used in the calculations has an important effect on the values of the residual axial stresses; moreover the axial dimensional changes during the boring-out process are so small that great accuracy cannot be claimed for the values measured. To this extent the results are inconclusive. It is, however, shown that both the dimensional changes and the shear stress distribution (from which the radial and hoop stress distribution can, of course, be deduced) at any stage in the process can be calculated with satisfactory accuracy by the relatively simple approximate methods described.
Teaching of Metallurgy to Engineers
Authors:   Education and Training Group, Ball J. G.
Published: October 2007

The recent history of developments in metallurgy and their impact on teaching are briefly surveyed. The general principles to be followed in designing courses in metallurgy for engineers are discussed and the importance of taking account of the type of engineer and the academic background of the class is stressed. Three types of syllabus are outlined and considered in relation to the various needs of classes of engineers.