bluuebunny/crossref_metadata_2025 huggingface dataset:
An Analysis of the Plastic Bending of Wide Plate, and the Effect of Stretching on Transverse Residual Stresses
Authors: Alexander J. M.
Published: October 2007

Part I of this analysis is devoted to solving the problem of bending a wide beam of ideally plastic material, under substantially plane strain conditions. A geometric method of solution, in which the stress and strain paths during the deformation are determined in the stress plane, is compared with the well-known analytical solution. Curves are given which will allow the rapid estimation of bending moments and ‘spring-back’ for plates of an aluminium alloy conforming to B.S. 1476:HE 15W†. The system of residual stresses induced is determined and compared with that for a narrow beam.

In Part II the geometric method mentioned above is used to estimate the effectiveness of stretching in reducing residual stresses which are transverse to the direction of stretching. This is a problem of some technological interest in that residual stresses arising from operations such as heat treatment and quenching are usually complex, lying in all directions within the plane of the plate. It is shown that stretching in a direction transverse to the major residual stresses is almost as effective in their reduction as stretching in a parallel direction.
Vibration of Cascade Blades Treated by Actuator Disc Methods
Authors: Whitehead D. S.
Published: October 2007

This paper gives a theoretical method of calculating the aerodynamic forces on vibrating compressor and turbine blades subject to two fundamental limitations. These are, firstly, that the time for the fluid to flow through the cascade must be small compared with the period of the vibration, and secondly, that adjacent blades must vibrate nearly in phase. This enables any kind of two-dimensional steady-flow cascade data to be used. The methods given also allow the vibration forced by fluctuations in the incident flow to be calculated.

The main conclusions are as follows:

(1) Bending vibration of unstalled blades with small mean deflection is always damped. (2) A criterion for bending flutter of unstalled blades with large mean deflection is derived. This is qualitatively supported by experiments carried out by Shioiri and Shibata (1)†. (3) A condition of instability of the flow through stalled cascades of fixed blades is derived, and agrees with previous investigations by Fabri and Siestrunck (2) and Rannie and Marble (3). This also agrees with the results of an experimental investigation by Wood (4). (4) A criterion for the bending flutter of stalled blades is derived, and it is shown that this limit is reached before the instability limit referred to in (3) above. (5) It is found that, except for a particular case of zero stagger cascades, flutter of unstalled blades in torsion will always occur. For this case, however, the first fundamental assumption referred to above is unlikely to be true and more detailed investigation of this case is required.
Development of High-Temperature Strain Gauges
Authors: Bertodo R.
Published: October 2007

This paper is restricted to a review of the work carried out in order to develop a strain gauge capable of operating at temperatures up to 1000°C with an inherent accuracy of ±5 per cent.

A large number of resistance alloys were tested as unbonded long wires at room temperature and, from the results obtained, a small number were selected for further investigation, in the form of gauges, at high temperatures. The effects of factors such as metallurgical changes, geometric shape and long-term exposure on the behaviour of the gauges were investigated. A number of bonding mediums, some commercially available, were examined with particular reference to creep under load, shear strength and resistance to erosion and thermal shock. Finally some preliminary tests in conjunction with the measurement of steady strains at elevated temperatures were undertaken.

It is concluded that the gauge factor is a function of the lattice imperfections of the element wire and, as such, will be temperature-conscious only if the imperfections themselves are affected by temperature variations. In general, any factor affecting the resistivity will affect the sensitivity. The most significant result obtained during the work described is that the gauge factor may be predicted within ±5 per cent at any given temperature, provided certain precautions are observed.

Some typical failures under field conditions are discussed as also are the possibilities of operating for protracted periods under steady stress conditions. More stringent requirements for future applications suggest that the wire gauge will be unsuitable, in view of its low resistance in very small sizes, and a possible alternative is briefly outlined.
Hunting of Water Level in Float-Controlled Deaerators
Authors: Morton A. J.
Published: October 2007

Operating difficulties encountered with a deaerating feed heater during full-scale test-bed trials of a complete prototype main propulsion machinery installation are described, together with the eventual successful remedy. The water level control system of the deaerator is analysed mathematically and a criterion for stable operation established. Comparison of the theoretical and observed behaviour of the deaerator shows reasonable agreement. Practical factors affecting the validity of the theory are examined and suggestions made for improvements in design. Some remarks on common deaerator design practices are made in the light of test-bed experience.

The example of this deaerator is used to illustrate an introduction to more general analytical methods. The need for these in modern steam-plant design work is explained, together with the obstacle to their use imposed by our current ignorance of the kinetic characteristics of common plant items.
A Relation between the Critical Alternating Propagation Stress and Crack Length for Mild Steel
Authors: Frost N. E.
Published: October 2007

Fatigue tests have been carried out on mild steel specimens containing edge cracks of various lengths and the alternating stress just insufficient to cause the cracks to grow obtained. It was found that the relation between this critical alternating stress σ and the crack length l was given by σ3 l = constant. By means of this relation it was possible to correlate a wide variety of hitherto unrelated notch fatigue data.
On Turbulent Lubrication
Authors: Constantinescu V. N.
Published: October 2007

The paper concerns the hydrodynamic turbulent motion in the lubricant layer. Proceeding from the Reynolds equations and introducing the approximations currently used in lubrication problems, owing to the lubricant film thickness, the general motion equations for turbulent lubrication are written.

Using the Prandtl mixing length hypothesis, exact and approximate solutions are obtained for the velocity distribution into the lubricant layer. The results are discussed by pointing out the pressure gradient and the Reynolds number influence on the velocity distributions, as well as the differences with respect to the laminar flow.

In order to obtain simple formulae, the exact dependence of the rate of flow on the pressure gradient into a dimensionless form is replaced by a linear relation, the slope of which depends on the Reynolds number. This approximation allows the obtainment of the pressure differential equation under a simple form. The pressure equation is integrated in case of journal bearings, by assuming a constant or a variable viscosity of the lubricant.

The results are compared to the experimental data obtained by M. I. Smith and D. D. Fuller and the good qualitative agreement is pointed out.
Design and Testing of Large Gas Ducts
Authors: Bowden A. T. , Drumm J. C.
Published: October 2007

The paper outlines some of the problems encountered in the design and testing of the large ducts associated with present-day gas-cooled nuclear reactors. Various ways of providing ductwork with flexibility are analysed and it is shown that a design involving the use of a combination of tied expansion bellows and cascaded corners is the most economic way of meeting the need for high flexibility and low flow pressure loss. The design of large tied expansion bellows is discussed and an account is given of the tests carried out on a prototype of the bellows now being installed in the gas circuits of the Bradwell nuclear power station in Essex. A brief reference is made to the difficulties encountered in the development of large butterfly valves for reactor ductwork and performance figures are quoted for one of the valve designs which eventually proved successful under test.
The Diesel Engine in Association with the Gas Turbine
Authors: Chatterton Ernest
Published: October 2007

On the basis that the future development of the diesel engine is inevitably dependent upon its association with a gas turbine, this paper explores three known methods by which the association between the engine and the gas turbine may be achieved, namely, turbocharging, compounding, and the gas generator.

Potential performances attainable from these three arrangements for both 2-cycle and 4-cycle engines with and without charge cooling are derived by methods which are explained, and it is demonstrated that high specific power outputs become possible at high air-manifold pressures without exceeding established limitations for maximum cylinder pressure, piston temperature, or turbine inlet temperature.

The characteristics and limitations of the three alternative arrangements are compared and the conclusion is drawn that a highly supercharged 2-cycle engine used as a gas generator feeding a power turbine would provide an efficient and versatile power unit.
Development of Some Unconventional Centrifugal Pumps
Authors: Barske U. M.
Published: October 2007

A centrifugal pump of a simplified and unorthodox design has been developed for the immediate satisfaction of special urgent requirements. The experiences gained were encouraging, and this type of pump has been successfully applied to a number of different purposes. Results of tests and recent investigations are given which suggest that some aspects of common centrifugal pump design practice are of lesser importance than are generally considered.

A few more items developed in connection with this pump are described, such as shaft seals especially suitable for high rotational speeds, means to reduce hydraulic friction losses of pump impellers, and a novel pump impeller designed to overcome cavitation difficulties.
Dynamic Loads on the Gears of Electric Traction Motors Passing over a Rail Joint
Authors: Lehel V.
Published: October 2007

The movements of a pair of wheels and axle with and without an electric traction motor passing over a rail joint are investigated. The track is assumed to be resiliently supported and two basic idealized types of joint are considered. In the case of there being a traction motor on the axle, the rotating mass of the armature is regarded as a separate mass resiliently connected to the unsprung masses of the wheels and motor body and the dynamic gear loads are calculated. It is shown that further approximation of actual conditions was possible by a combination of the basic types of rail joint. A concrete example is evaluated and it is seen that the tooth loads are greater with a limited amount of resilience than with an ideally rigid drive, the maximum occurring in the region of the inherent structural resilience of a normal ‘non-resilient’ gear drive. Gear-tooth separation due to dynamic actions is investigated and it is found that the gear loads normally attending such separation are not excessive.
Experimental Analysis of Tandem Mill Control Equations
Authors: Gill H.
Published: October 2007

This work is concerned with an experimental analysis of tandem mill control equations as developed by Hessenberg and Jenkins. A 3-stand model scale mill was used to study the effect on steady state conditions of three different forms of disturbance, namely front tension changes, screw adjustments, and variations in ingoing gauge. The object of the experiments was to investigate the conditions for maximum inherent stability of the mill as a whole unit. The effect of changes in stand rigidity and motor speed regulation are discussed in detail and conclusions drawn regarding the settings for optimum performance when the gauge is controlled by screw movements in the early stands combined with tension variations in the latter.
Formula for ‘Spread’ in Hot Flat Rolling
Authors:   Applied Mechanics Group, Sparling L. G. M.
Published: October 2007

An experimental investigation has been made to compare the elongation and the lateral spreading which occur during hot rolling of rectangular sections (i.e. slab or bar) between plain rolls. The results did not agree with predictions made from existing formulae for ‘spread’, and a new formula is presented which was derived empirically from the results and is of a form logically to be expected from a consideration of the factors likely to affect spread. This formula takes into account the ratio of the width of the stock to the length of the arc of contact during rolling, the ratio of the roll radius to thickness of the stock, the width to thickness ratio of the stock and the draft (or reduction). A modified formula has also been devised to take into account not only the geometrical variables but also changes in rolling temperature, steel composition, roll and bar surface condition, and speed of rolling (strain rate).
Effect of Piston/Bore Clearance in Small Refrigeration Compressors
Authors:   Internal Combustion Engines Group, Smith H. J.
Published: October 2007

This investigation into the effect of piston diametral clearance on the performance of a small refrigeration compressor was made to determine the limiting conditions for satisfactory performance.

Six pistons of standard ringless design were used in the same compressor giving clearances ranging from 00004 to 00041 in. The tests were carried out on a refrigerator with a calorimeter-type evaporator using dichlorodifluoromethane.

Particular attention was given to the effects on volumetric efficiency and specific power consumption. These quantities were plotted against pressure ratio over a wide range of operating conditions and an analysis of the losses involved was made and related to the diametral clearance.

Both volumetric efficiency and specific power were found to vary greatly with the clearance, the former being greatest with the minimum clearance but the latter showing a tendency under some conditions to a minimum value for a diametral clearance of 0.0022 in. Honed cylinders and ground pistons are considered essential for good performance.

It is suggested that in addition to piston leakage, entry heating plays an important part in the reduction of volumetric efficiency.
Vibrations of Pre-Twisted Cantilever Blading: An Additional Effect Due to Torsion
Authors:   Applied Mechanics Group, Carnegie W.
Published: October 2007

The total energy relationships are given for a thin blade vibrating in combined bending-bending-torsion when allowance is made for bending of the longitudinal fibres occurring due to torsion. The Lagrangian function is, thus, obtained and, by use of variational methods, the equations of motion and the boundary conditions are derived. For the special case of a straight blade of uniform cross-section, symmetrical about both principal axes, an expression is deduced for the torsional frequencies which shows agreement with a similar expression obtained previously by a somewhat different approach
Influence of Plain Journal Bearings on the Whirling Action of an Elastic Rotor
Authors:   Lubrication and Wear Group, Morrison D.
Published: October 2007

An analysis is made of the whirling performance of an elastic rotor supported in fluid lubricated journal bearings, taking account of both the displacement and velocity-dependent components of dynamic bearing action. It is shown that two distinct modes of vibration occur corresponding roughly to half-speed whirling, oil whip, etc., and to reduced elastic whirling speed respectively. Typical bearing coefficients are given for short journal bearings. Using these, examples are given illustrating the calculation of the natural frequencies of a rotor running at a fixed speed and the calculation of the response curve of a rotor running through a range of speeds. Experimental evidence confirming these results is given

The inherent stability of an elastic rotor bearing system is also investigated and a chart presented showing the limits of stable operation of an elastic rotor
Some Aspects of the Performance of High-Speed Lightly Loaded Cylindrical Roller Bearings
Authors:   Lubrication and Wear Group, Smith C. F.
Published: October 2007

The paper deals with the wear problems which are sometimes experienced when operating parallel cylindrical roller bearings at high speed, with jet lubrication, in turbine mainshaft bearing practice

Tests show that considerable cage slip often takes place, as reported by previous investigators, the cage and roller assembly travelling at speeds lower than that predicted from the epicyclic relationship

It is concluded that hydrodynamic lubrication normally occurs between the rollers and races when appreciable cage slip takes place. If the radial load on the bearing suddenly increases under these conditions, the hydrodynamic film is not always able entirely to prevent metallic contact and wear of the rollers and races

Further experimental work is required before complete understanding of the problem can be obtained. Tentative recommendations, however, are made for minimizing the incidence of this type of wear in practice
Some Comments on University Teaching of Mechanical Vibration
Authors:   Education and Training Group, Bishop R. E. D.
Published: October 2007

Some comments are made on the teaching of mechanical vibration theory to undergraduates. Reassessment appears to be needed of several topics which are normally taught and certain others demand admittance to a modern syllabus.
Methods of Load Verification of Tension and Compression Testing Machines
Authors:   Applied Mechanics Group, Swindells B. , Debnam R. C.
Published: October 2007

A brief review is given of the early methods used for the load verification of material-testing machines. Demands for greater accuracy led to the development of elastic proving devices, followed by deadweight standards of sufficient accuracy to calibrate these devices. The methods resulting from these developments are also described. The definition of the technical unit of force is given, followed by a consideration of the minimum accuracies required of deadweight standards, proving devices and testing machines verified by proving devices. These considerations of accuracy bear particular reference to the British Standard covering the load verification of testing machines.

A deadweight standard machine and many of the more common types of proving devices are briefly described. General guidance is given of the range of loads covered and the performance which may be expected of the various types of proving devices.
The Rigidity of RIB-Reinforced Cover Plates
Authors:   Applied Mechanics Group, Harvey J. , Duncan J. P.
Published: October 2007

An experimental approach to the problem of rib-reinforced cover plate design is outlined.

Exact tractable methods for calculating the deflections of radially ribbed plates are not available. Outlines of formal mathematical treatment which use several approximations are presented to highlight the theoretical difficulties.

The technique of Fizeau interferometry was employed to study the deflections of a series of laterally loaded ribbed plates of varying proportions. From the results, values of the rigidity of the plates were found together with the best combination of parameters to ensure optimum stiffening with a minimum of localized curvature for plates of fixed total weight.

The nature and character of the localized curvatures developed in an over-stiffened ribbed plate was revealed by photographic records obtained by means of the Salet-Ikeda slope-contouring technique.

It was concluded that, for optimum design on a basis of rigidity of plates of given total weight, 40 per cent of the total weight of a ribbed plate should be in the ribs or webs and 60 per cent in the basic plate or flange. Localized curvature with attendant stress concentrations were found not to be serious under such a degree of stiffening. Frozen stress photoelastic studies have been initiated to elucidate stress distributions in the vicinity of the ribs.
Burst Cartridge Detection in British Gas-Cooled Reactors
Authors:   Nuclear Energy Group, Dent K. H. , Williams D. W.
Published: October 2007

A burst cartridge remaining in a reactor may eventually release such quantities of radioactive fission products into the coolant circuit as to cause a potential health hazard or maintenance difficulty. It is important, therefore, to be able to detect and locate a burst so that the reactor operator can discharge the cartridge concerned. Of all the possible methods, only detection by the released fission products is satisfactory.

Gaseous fission products diffuse through the leak in the can wall against a coolant inflow induced by oxidation of the fuel, and their presence in the coolant has to be detected against an unavoidable background count. The leak size at the threshold of detection can be estimated from the operating conditions, and the manner in which b.c.d. (burst cartridge detection) signals arise from a developing burst merits special study.

To discriminate against the radioactive decay of the coolant gas itself the precipitation system of monitoring is used. From each fuel channel in the reactor a sample of gas is drawn periodically. This is passed through a precipitation chamber where particular fission product nuclides decay to give ionized daughter products which are collected on a charged wire. The wire is moved to a shielded scintillation counter and the fission product nuclides, which undergo a second radioactive transition, are measured to the exclusion of the active nuclides in the coolant which do not. The performance and sensitivity of the system can be calculated and optimized by considering the expression for the count from the wire.

The mechanical design of the equipment varies in detail from station to station. In later designs the mechanical equipment is simpler and easier to maintain, and greater use is being made of automatic processing and presentation of the signal.
Temperatures in Orthogonal Metal Cutting
Authors:   Industrial Administration and Engineering Production Group Applied Mechanics Group, Boothroyd G.
Published: October 2007

The results of a photographic technique for the determination of the complete temperature distribution in the orthogonal metal cutting process are presented; they are found to disagree with previous theoretical predictions. The temperatures along the tool rake face are of particular interest because they are thought to affect the wear of the cutting tool and friction between the chip and tool; it is found that these temperatures have been considerably over-estimated by previous work. By introducing the width of the secondary deformation zone, i.e. the extent of sub-surface deformation due to friction at the tool-chip interface, as a new variable, it is found that more consistent predictions of rake face temperatures can be made. From this work information has been obtained on the shape of the zones of plastic deformation in metal cutting and on the distribution of heat generation within these zones.
Turbine-Blading Development Using a Transonic Variable-Density Cascade Wind Tunnel
Authors: Forster V. T.
Published: October 2007

The thermal development of the modern steam and gas turbine over the past two decades has been greatly assisted by a much better understanding of the fluid behaviour as it passes through the machine. This has been brought about by the increasing amount of aerodynamic research and development being carried out on the many components of these turbines.

This paper concentrates on the fixed and moving-blade elements of the large steam turbine, and describes the design and operation of a transonic variable-density wind tunnel for static cascade testing of turbine blading. The importance of Reynolds number and Mach number is emphasized, and the manner in which these parameters influence the blading losses. The origin of the trailing edge shock waves on blades discharging obliquely, and their effect on performance, is discussed in some detail, drawing on both experimental and theoretical techniques. A large proportion of the flow section of long last 1.p. stages is operating in the supersonic region, and possible future blades may have relative discharge tip Mach numbers approaching 20.
Fourth Paper: The Explosive Expansion of Unrestrained Tubes
Authors: Johnson W. , Doege E. , Travis F. W.
Published: October 2007

The use of a line explosive charge in the expansion of water-filled brass tubes is investigated, both on a small experimental scale and on a large industrial scale. Results are presented showing how the radial velocity of deforming tubes and the distribution of hoop and axial strain in the deformed product are related. Metallurgical and some other aspects of the process are discussed.
A Simple Theory for Pressure Pulses in Exhaust Systems
Authors: Davies P. O. A. L. , Dwyer M. J.
Published: October 2007

A simple method is presented for calculating the strength of pressure pulses transmitted through pipes with area changes or in simple branch systems. The method is based on the assumption of one-dimensional flow, otherwise the exact gas relations are employed. A number of examples of typical practical configurations were investigated both theoretically and experimentally and the results compared. With the exception of one or two cases where three-dimensional effects predominate, the agreement between the theory and the measurements was very satisfactory. The application of the theory to flow problems in internal combustion engines is discussed in some detail.
Free Convective Cooling of Cabinets Containing Heat Dissipating Components
Authors: Noronha R. I.
Published: October 2007

A theory has been developed based on the accepted heat transfer theories of Fishenden, Saunders, Weise and others, together with the results of the author's experiments. From this theory it is possible to evolve a design sheet which can be used to predict ambient temperatures within cabinets for predetermined areas of ventilation. Hence, design curves of temperature, in relation to areas of ventilation, can be obtained for specific cabinets and methods of cooling. From these curves, it should be possible to select the method of ventilation and the optimum cooling area and hence ensure that the maximum tolerable ambient temperature in which the components are required to operate shall not be exceeded.

The effects on the hottest component, when the methods of ventilation are altered, the ventilating area is varied and the main heat source is progressively raised, are studied. The results of these experiments and the comparisons between predicted and observed ambient temperatures are discussed. Recommendations for positioning components within cabinets for maximum cooling effects are made.
Chemical Commissioning at West Thurrock Power Station
Authors: Sherry A. , Gill E. R.
Published: October 2007

The chemical techniques adopted in the pre- and post-commissioning phases at West Thurrock power station are described. Apart from the detailed account of the chemical cleaning operations, types of cleaning processes, acids and strengths, sampling arrangements, circulation rates and method of final inspection are also considered. Mention is made of the desirability of sections of the plant arriving on site in a clean sealed state. The cleaning methods bring about a rapid reduction in boiler water silica so that full load can be achieved quickly.

A new technique, involving nitrogen sealing, to reduce metal pick-up during start-ups has been evolved, whilst the early control of both feed and boiler water conditions is stressed and an optimum hydrazine level determined.
Chatter in Horizontal Milling
Authors: Andrew C.
Published: October 2007

An analytical and experimental investigation into the chatter behaviour of a horizontal milling machine is described in this paper. The experimental results were used to check the basic assumptions involved in the analysis.

The machine structure and the cutting force characteristics of the workpiece material were initially tested separately. The vibration behaviour during machining was then investigated for a range of machining conditions. These included different values of cutter speed, workpiece width, depth of cut and number of cutter teeth, different directions of cutter rotation, and plain and climb milling. The results are presented in the form of stability charts, describing conditions when chatter was present or absent.

Chatter was found to be of the regenerative type, occurring in bands of cutter speed. For all conditions tested, the machining stability defined by the envelope of the chatter bands improved as cutting speed was reduced.

The dependence of the chatter bands on cutter speed, the chatter frequency, and the qualitative changes in the chatter-free machining capacity were predicted successfully at all but low speeds. Quantitatively, the chatter-free machining capacity was predicted to be slightly less than half that found by experiment.

The conventional assumptions for dynamic cutting force characteristics were shown to be in error. More accurate assumptions based on recent fundamental work only partly explained experimental observations, indicating that an additional, and as yet unstudied, dynamic force component exists.
Third Paper: Servo Reliability in the ‘Seacat’ Missile
Authors: Foreman P. F. , Carrington J. E.
Published: October 2007

The ‘Seacat’ missile has been adopted by the Royal Navy as the standard close-range ship-to-air weapon of the 1960's. When the specification was drawn up reliability requirements were nebulous in the extreme, but it was appreciated that with such a missile a ‘high’ reliability had to be achieved in spite of intense pressure to reduce weight, space, and cost to absolute minima, and in spite of some unusual operational requirements.

This paper reviews in retrospect some of the methods adopted both in the servo actuator design and in production procedures to meet these requirements. In addition the systematic reporting of tests carried out in depots of ships enables an assessment to be given of the reliability achieved in service.

It is concluded that, in the mechanical sphere, the cost of a full scale statistical exercise aimed at a prediction of reliability may well be exorbitant, and whilst assurance will be obtained, the contribution to the degrees of reliability may only be marginal. However, the systematic recording and analysis of experience in the field will enable maximum benefit to be derived for future projects.
Some Observations on the Design of Spherical Pressure Vessels with Flush Cylindrical Nozzles
Authors: Leckie F. A. , Payne D. J.
Published: October 2007

In this paper the design of a spherical pressure vessel pierced by a radial cylindrical nozzle is discussed. The nozzles considered end flush with the inside of the vessel. Previous work on stress concentration factors, shakedown factors and limit pressure factors has been drawn together and presented in a compact form convenient for the use of designers. These results have been used to discuss the implications of designing to a certain stress concentration factor and to show that this procedure is very reasonable when a concentration factor of 2.25 is used.
Design and Development of Petro-Forge High Energy-Rate Forming Machines
Authors: Chan L. T. , Bakhtar F. , Tobias S. A.
Published: October 2007

The paper describes the design and development of a new type of high energy-rate forming machine called ‘Petro-Forge’. This differs from other designs in that the energy required for the actuation of the ram is produced by a petrol combustion process. After describing the principle of operation, the design of the prototype machine, as well as its method of operation, is discussed. Extensive tests have been carried out with the aim of optimizing performance and determining the overall capabilities of the system. These results have led to the design of Petro-Forge Mark I, the essential features of which are also presented.
Push-Pull Low Endurance Fatigue of En 25 and En 32B Steels at 20°C and 450°C
Authors: Mackenzie C. T. , Benham P. P.
Published: October 2007

Mild steel (En 32B) and a 2 1/2 Ni-Cr-Mo steel in soft and heat treated conditions were subjected to reversed uniaxial strain cycling at 20°C and 450°C with continuous cycling at 2–10 c/min and also 10 min hold-times. The results are plotted in graphical form from which a number of empirical relationships are derived between plastic strain range, stable stress range, cycles to failure, strain energy, and true fracture ductility and strength. High temperature causes a marked reduction in strength for both materials, which is greater at the lower strain ranges, compared with room temperature cycling. There is little or no effect due to hold-time compared with continuous cycling at room temperature for En 25 (heat treated). There is only a slight reduction in strength at 450°C, but the situation is likely to be worse for longer hold-times.
Design and Development of a Compressed-Air Driven, Counterblow High Energy-Rate Forming Machine
Authors: Marland I. , Organ A. J. , Tobias S. A.
Published: October 2007

As a first stage in the development of a large, double-acting, petrol combustion actuated, high energy-rate forming machine, a compressed-air driven device was designed and constructed. This was intended to be a research vehicle for establishing general design principles, particularly as far as the structural configurations and the method of platen synchronization were concerned. The characteristic design features of this machine are discussed and an appraisal of the design is given.

Experiments were carried out with the aim of (1) determining the net energy output of the machine and (2) finding the maximum platen approach velocity for a range of values of the initial charge pressure. For the determination of the energy output of the machine, calibrated crush-gauges were used, the results being cross-checked by measuring the maximum relative velocity between the platens, and from this and the weight of the moving masses finding the maximum kinetic energy. For the determination of the maximum platen approach velocity, electric velocity transducers were used, the results being checked with the aid of a high-speed ciné camera. The maximum energy output of the machine was found to be 75 000 ft lb, which was attained with a maximum impact velocity of 80 ft/s, as aimed at in the design of the machine. Some typical examples of hot forgings produced with the machine are also presented.
Design of Thermometer Pockets for Steam Mains
Authors: Roughton J. E.
Published: October 2007

A procedure is described for designing thermometer pockets having a good performance in rapidly changing steam conditions. For quick response, the bore diameter and tip wall thickness are minimized while, for safety reasons, the pocket is made conical: a low net error is achieved by choosing dimensions such that the positive and negative errors cancel out. The design theory, which takes account of the effects of fluid temperature gradients (on the assumption of fully developed turbulent flow) is discussed in detail and a practical guide is also given. Although the emphasis is primarily on steam pipes, much of the theory is of interest to the general field of fluid temperature measurement.
Gear Conformity and Load Capacity
Authors: French M. J.
Published: October 2007

A measure, M, of the conformity or closeness of fit of gears is proposed and it is shown that there is a limit on its value; this limit is a function of the material properties and is about 2.5 times the value for involutes for gears of case hardened steel.

It is shown that no very large improvement in M can be had above that obtainable in known non-involute forms, specifically Wildhaber-Novikov gears.
Marine Transport of Liquefied Natural Gas
Authors: Clark L. J.
Published: October 2007

In the past, it has been a matter of concern to many people that natural gas which is available and sometimes flared to waste in desert places of the earth could not be conserved and economically transported as fuel to needy industrial countries.

To make such an operation possible, it is necessary to refrigerate the gas, which consists mainly of methane, to a temperature of — 260°F, under which condition it condenses to a liquid and shrinks to one-six-hundredth of its volume as a free gas. In this form and as a boiling liquid, it can be transported in insulated tanks built into ships specially designed for the purpose. Auto-refrigeration maintains the cargo at its boiling point and heat leakage through the insulation causes a small proportion of the cargo to boil off as gas. Such gas can either be re-liquefied by installing a refrigeration plant on board or be used as fuel in the ship's propulsion machinery.

The lecture describes the research and development work which led up to the full-scale trials in 1959 for the transportation of liquefied natural gas by sea in the Methane Pioneer. This is followed by a resume of the design requirements, building techniques and subsequent operating experience of the first two commercial ships which entered service in 1964 for the regular carriage of liquefied natural gas from Arzew in Algeria to Canvey Island in the Thames.

The design and engineering problems arising in these developments were unusual and varied, and they necessitated close co-ordination in the fields of cryogenics, metallurgy, chemical engineering and naval architecture. Not only were there problems associated with the physical properties of materials and insulants at low temperatures and the large contraction movements and strains induced by temperature change but there were problems of handling a boiling liquid continually releasing gas which, if trapped, could build up dangerous pressures. All these problems had to be faced on the large scale and assessed against the potential hazard of fire and explosion; in addition, they had to be superimposed on the somewhat unpredictable behaviour of a ship at sea whose design criteria were influenced more by experience and empiricism than by basic science.

The unusual and unprecedented nature of the project involving safety of life at sea, and affecting other users of rivers, ports and harbours, meant that from the outset there had to be close liaison and co-operation with Government Departments, Ministries, harbour and river authorities, regulatory bodies and local authorities. The successful conclusion of the project confirms the effectiveness of this co-operation and it affirms how the imagination, perseverance and technical skill of a team of engineers can be harnessed in endeavour and achievement.
Special Steels for High Temperature Service
Authors: Kirkby H. W.
Published: October 2007

In this lecture the author reports on the progress made in the development and application of creep-resisting steels over the last 20 years, with particular reference to research carried out at The Brown-Firth Research Laboratories. The properties of the more established steels are reviewed, along with those of a number of newer steels introduced during this period. These include the 12 per cent chromium variants specially ‘tailor-made’ for aircraft gas turbine discs, two improved austenitic steels and two non-stainless types: a 6 per cent chromium complex steel, and a 2 per cent chromium molybdenum vanadium aluminium nitriding type. Cast austenitic pipe steels are also discussed.

The author describes work being carried out with the object of improving the proof strength of austenitic steels, e.g. warm working and alloying with nitrogen.

Some information is also presented in respect of the creep ductility properties of a number of the steels mentioned in the paper, with special reference to weld heat effects.
Pressure Vessels of High Proof Strength Warm Worked Stainless Steel
Authors: Kemper M. J. , Morley J. I. , McWilliam J. A. , Slater D.
Published: October 2007

In order to establish the necessary data to enable high proof strength austenitic stainless steels to be used for the fabrication of pressure vessels, plates were produced with an increased proof stress obtained by the warm working method. The laboratory investigation then showed that it was practicable to raise the proof strength of this material to twice the normal value for fully softened plate with an improvement in the ultimate tensile strength.

Following this, two similar experimental vessels were manufactured in normal and high proof strength 18% Cr-8% Ni-Ti stabilized steel and these were subjected to hydraulic pressure testing. The vessel tests showed how stainless steel vessels behave under static pressure application at room temperature, and the behaviour of the high proof strength vessel indicated that it would be quite safe at nearly double the design pressure for the fully softened vessel. The strain hardening of stainless steel, fabricating techniques and weld quality have also been investigated and these are reported upon in the paper. Proposals for design stress criteria and stress values are made in relation to an examination of existing pressure vessel codes and the experimental data.
The Use of Steam Ejectors for the Vacuum Degassing of Steel
Authors: Knight J.
Published: October 2007

Steam ejectors have now become the established pumping system for degassing molten steel because of their high gas handling capacities at low pressures. The stream and ladle degassing processes are described including plant required in addition to the ejectors. Theoretical consideration is given to the operation of a steam ejector, and the design requirements for a complete multi-stage plant to operate at less than 1 torr are discussed.

Finally the economies and benefits derived from the processes are outlined and future trends indicated.
Ignition Caused by the Adiabatic Compression of Air in Contact with a Lubricating-Oil-Wetted Surface
Authors: Chase J. D.
Published: October 2007

A pneumatically operated rapid compression machine is used to study the conditions under which ignition will occur when air in contact with a lubricating-oil-wetted surface is adiabatically compressed. The boundaries and violence of explosion are determined from pressure measurements made during and after compression. The specific variables investigated are initial temperature, compression ratio, oil volume, and oil type. The maximum oil temperature and compression ratio investigated are 210°C and 31/1 respectively. Several concentrations of three mineral oils are considered. In order to calculate liquid-vapour equilibrium of the lubricating oils, vapour pressure-weight loss data obtained by a flame ionization method are employed in conjunction with the carbon number distribution analysis of the lubricating oil components. The calculation of oil-air equivalence ratios in the vapour phase leads to the prediction of the effect of oil concentration and of temperature on ignition hazards. The prediction is in good agreement with experimental findings and accounts for the influence of temperature on ignition. For example, it was found that ignition occurs at 120°C for compression ratio of 31/1 but will not take place until the system is heated to 160°C for a compression ratio of 18/1.
Third Paper: Frictional Behaviour of Lubricated Rolling-Contact Elements
Authors: Poon S. Y. , Haines D. J.
Published: October 2007

In this paper a rig is described for the study of force systems between rolling steel surfaces which under Hertzian load form flat circular contact surfaces. The rig is used to explore the behaviour of contacting bodies rolling in the presence of a lubricant and with a small degree of relative slide between the surfaces. Transitions from boundary to partial elastohydrodynamic lubrication and from partial to almost complete elastohydrodynamic lubrication have been observed and the transition from one type of lubrication to the other is marked by changes in the frictional behaviour of the system. These changes in behaviour are related to conductivity readings taken across the contact and it can be shown that the ratio of measured voltage across the contact to the applied voltage is a measure of the frequency at which surface asperities come into contact. Treating the ratio as a cumulative distribution function shows that two distinct populations exist and the point at which transition from one population to the other takes place corresponds to the transition from partial to full lubrication. The role the surface asperities play in relation to the oil-film thickness can clearly be seen in these experiments.
Performance Loss of Modern Steam-Turbine Plant Due to Surface Roughness
Authors: Forster V. T.
Published: October 2007

The serious consequences of blade-path deterioration that may result from boiler carry-over has led to active research into the performance aspects by the Air Flow Laboratory of the English Electric Company at Rugby. This paper reviews some of this work and illustrates the conclusions.

Data are required to determine nozzle and blade efficiencies with various types of surface finish, from polished specimens which can be regarded as hydraulically smooth, to the type of deposit build-up and/or surface pitting which can be experienced after periods of operation at site.

There is a great variety and randomness embraced by the term ‘surface roughness’. In a practical machine the difficulty is not only to obtain an accurate record of the roughened surface, but to assess its effect on the frictional loss. However, very many data have been obtained on the resistance to flow in pipes and along flat plates with varying degress of sand-grain roughness, and the simple theoretical treatment for turbine nozzles and blades explained in the paper makes use of these data. In this way, it has been possible to derive curves showing efficiency correction factors for both Reynolds number and roughness. The enormous variation in Reynolds number through a modern steam turbine makes this a highly important factor.

Experimental work using cascades of typical turbine profiles has also been carried out in the laboratory to try to substantiate the theoretical analysis, various grades of emery paper being used as a yardstick. A fair measure of agreement was obtained, and other workers' results are also available for comparison. The cascade tests of efficiency were also extended to reveal the particular areas on the nozzle convex and concave faces which were more susceptible to performance loss owing to localized roughening.

Finally both a 200-MW and a 500-MW steam turbine have been worked through to arrive at the worsening in heat rate that might be expected for specific sand-grain roughness values applied to all nozzle and blade surfaces. This sort of information assists the turbine manufacturer in deciding the extent of refinement necessary in his manufacturing processes to obtain satisfactory finishes. On the other hand, these ex-works finishes may well deteriorate after only short periods of site running according to evidence from many sources. Evidently increasing collaboration on these matters between manufacturers, the electricity boards, and station operators is necessary.
Theoretical Investigation into the Prevention of Cavitation in Hydraulic Actuators
Authors: Martin H. R. , Lichtarowicz A.
Published: October 2007

Results of theoretical studies into the reduction of cavitation and peak pressure conditions in valve controlled hydraulic actuators when operated under severe inertia loading conditions are presented. The investigation was carried out using an analogue computer on which a simulation was developed to demonstrate both cavitating and non-cavitating conditions. A comparison is made between some techniques for the reduction of cavitating conditions.