bluuebunny/crossref_metadata_2025 huggingface dataset:
First Paper: Sliding Friction between Lubricated Rollers
Authors: Jefferis J. A. , Johnson K. L.
Published: October 2007

The design and development of a power circulating rolling contact disc machine is described. Each disc is mechanically coupled to a separately excited d.c. electrical machine whose armatures are connected electrically. When the discs develop traction, power circulates by one machine acting as a motor and the other as a generator. In this way controlled traction with a stepless variation of sliding speed can be maintained between the rolling discs.

Dawson has shown that the pitting fatigue life of steel discs depends inversely upon the ratio of surface roughness to oil-film thickness. The disc machine has been used to measure the sliding friction between rolling discs under conditions similar to Dawson's fatigue tests. Large variations in surface roughness and film thickness resulted in relatively small changes in friction force. It is concluded that the effect of surface roughness and film thickness upon pitting life cannot be accounted for by changes in the friction force transmitted between the discs.

The insensitivity of the observed friction to variation in the surface roughness of the discs is explained in terms of the shear behaviour of the lubricant film at high contact pressures.
Fatigue Strength of Small Pinned Connections Made from Alloy Steel Fv 520B
Authors: White D. J.
Published: October 2007

Published work on pin-loaded lugs is reviewed, particular attention being given to photoelastically determined stress distributions and to results of fatigue tests for the purpose of identifying those factors that affect fatigue strength.

Fatigue tests have been conducted on lugs of width 1 [Formula: see text] in made from alloy steel FV 520B and loaded by means of a [Formula: see text]-in diameter pin. A systematic investigation was made of pin fit for both clearance and interference and the effect of various treatments was investigated; these included cadmium plating the lug bore and pin, applying the ‘Sulfinuz’ process to the lug and overstraining the lug bore. Two conditions of mean stress were investigated, namely, pulsating or repeated tension and 15 tonf/in2 mean tension.

Strength comparisons are based on the fatigue strength at 108 cycles, for the appropriate mean stress, of untreated lugs with exact-fit pins, these showing the lowest strength of all the lugs tested. It was found that clearance-fit pins and interference-fit pins were beneficial and with the larger values of clearance and interference tested the fatigue strength was almost doubled. Cadmium plating was ineffective while both Sulfinuz treated lugs and lugs with overstrained bores gave strength ratios of at least 1.6. An increase in mean stress from pulsating tension to 15 tonf/in2 mean tension, significantly reduced fatigue strength in most cases.

On the basis of the present experimental results, the design method proposed for lugs with interference-fit pins in Royal Aeronautical Society Data Sheet A.05.02, amended by Engineering Sciences Data No. 67012, may sometimes prove to be unsafe and caution is warranted in interpreting the safe loads predicted.
Simulation of an On-Off Pneumatic Servomechanism
Authors: Burrows C. R. , Webb C. R.
Published: October 2007

This paper describes an analogue computer simulation of an on-off pneumatic servomechanism comprising a polarized relay with dead zone and hysteresis, power relays, and an on-off four-way spool valve supplying air to a cylinder driving an inertia load acted upon by viscous damping and Coulomb friction. The effect of varying the amount of friction and of position, velocity, and acceleration feedback is studied.

The effect of the addition of stabilizing tanks is also considered.
The Prevention of Fretting Fatigue in Aluminium Alloys
Authors: Bowers J. E. , Finch N. J. , Goreham A. R.
Published: October 2007

The fatigue properties of three aluminium alloys, DTD683, L65, and AA2024, were determined in reversed bending, with a mean stress of 10 ton/in2, both with and without fretting.

Stresses are quoted as σ m ± σ a; i.e. a mean tensile stress of σ m with an alternating stress varying from + σ a (tension) to -σ a (compression). In bending tests only one face of the specimen has a tensile mean stress (σ m), the opposite face having a compressive mean stress (-σ m). However, failure always starts from the face having a tensile mean stress and endurance limits are quoted accordingly. The strength reduction due to fretting was greatest for the high strength Al-Zn-Mg alloy, DTD683, which had an endurance limit of 10 ± 10.3 ton/in2 without fretting but only 10 ± 1.6 ton/in2 under standard fretting conditions, i.e., 1/4 in span fretting pads loaded to 2.5 ton/in2 contact pressure. The strength reduction due to fretting was similar over a range of fretting amplitudes and contact pressures.

Fretting will not occur if metallic contact between the mating faces is prevented and tests show that this can be achieved by interposing substances such as graphite, MoS2 or p.t.f.e., in a suitable grease or resinous bonding material, between the mating faces. However, under fatigue loading, greases and resins tended to squeeze out from the contacting faces or break up under the high contact pressures so that they were only effective for a short time. It has been shown that more permanent protection against fretting can be obtained by metal spraying the surface of the specimen, thus preventing direct contact with the fretting pad. Shot peening also produced a significant improvement in fatigue strength under the standard fretting conditions; apparently the sub-surface compressive stresses prevented propagation of the cracks initiated by fretting.
A Stochastic Model for Weibull Failures as an Aid to Forecasting Replacement Requirements
Authors: Hastings N. A. J.
Published: October 2007

The model is concerned with the problem of calculating the expected number of failures from a population in which items as they fail are replaced by new ones.

Analytical methods are available for the failure of the first generation of items and also for the steady state, but many real problems require a solution for the transient state. This model calculates the expected number of failures for the transient state from failure data for the first generation, that failure data being in terms of one or more Weibull distributions. A feature of the model is its ability to handle early life, random and wear-out failures simultaneously. A computer programme for the model is given.
The Development and Production of High Pressure Feed Heaters for Modern Central Power Stations
Authors: Spence J. R. , Ryall M. L. , McConnell A.
Published: October 2007

The paper describes features of large high pressure (H.P.) feed heaters developed and manufactured during recent years. Attention is devoted to heaters with steel tubes.

An outline of important design considerations is given, including reference to the incorporation of integral desuperheating and drain cooling sections.

This is followed by consideration of tubeplates, headers, tubes, and tube welding, from both design and constructional standpoints. Particular reference is made to quality control procedures which have been evolved for heater components and for final assembly. The Foster Wheeler process for butt welding tubes to the tube-plate is described, and details are given of the clean manufacturing conditions under which this process must be carried out in this application to ensure tube weld integrity.

In a final section dealing with current developments, details are given of a new design of heater incorporating a toroidal header. This design permits the full feed flow for a 660 MW set to be passed through a single train of H.P. heaters, without incurring the penalty of excessively large forgings or castings. This arrangement has been found to result in major cost savings compared with twin train heaters with conventional flat tubeplates.
A Performance Investigation into the Elastically Stepped and Shrouded Thrust Bearing
Authors: Hemingway E. W.
Published: October 2007

An experimental investigation is reported in which a stepped and shrouded thrust pad was formed from an initially plane pad face by elastic deflection caused by pressures generated hydrodynamically in the oil film. The pad shape was optimized experimentally and it produced thicker films than a comparable tilting pad bearing but with higher frictional resistance. Pressure and film thickness contours were investigated and plotted. A comparison is made with stepped pad bearing results. This paper is based on sections of a thesis presented in 1966 for the degree of Ph.D., University of London.
Speed and Frictional Effects in Hot Forging
Authors: Jain S. C. , Bramley A. N.
Published: October 2007

Simple compression tests have been made on solid and ring shaped billets at a temperature of 1120°C. The experimental variables were the impact speed of forging, which was varied from 0.07 ft/s to 40 ft/s, and the type of lubricant. The investigation was concerned with the effect of these variables on the friction conditions and the load and energy requirements.
Damage Due to Cavitation and Sub-Cooled Boiling Bubble Collapse
Authors: Hammitt F. G.
Published: October 2007

The possibility of the applicability of spherical symmetry to cavitation and highly sub-cooled bubble collapse is considered in the light of present photographic and theoretical evidence, and it is concluded that such symmetry is unlikely in situations of engineering importance. Rather an asymmetry which generates a high-velocity microjet is a more likely mode of collapse. The present evidence relative to the importance of microjet impact as opposed to the classical spherical shock-wave model for cavitation damage is examined and some new experimental evidence presented. It is concluded that the microjet model is most likely of predominant importance in cavitation damage. Some estimates for the pertinent parameters of such microjets are presented.
High Temperature Testing of Pressure Vessels
Authors: Taylor T. E.
Published: October 2007

Creep rupture tests on three spherical vessels of aluminium killed mild steel have been carried out. The vessels were identical and each contained three unreinforced protruding nozzles. Two of the nozzles, of equal thickness, were attached with low hydrogen and rutile weld metal respectively. A third, thinner, nozzle was welded with low hydrogen electrodes. Two of the vessels were subjected to steady pressure, whilst in the third the pressure was relieved briefly at regular intervals.

In two of the vessels repairs were effected at failure and testing continued for an arbitrary period without further failure. The tests revealed that the life of all the vessels was limited by the integrity of the weld metal. Comprehensive measurements established the patterns of strains on the outside surfaces of the vessels. These strains supported current theoretical concepts.
Turbine Flow Problems of Binary Cycles Employing High Density Fluids
Authors: Horn G. , Norris T. D. , Whybrow J. F. T.
Published: October 2007

High density working fluids such as the fluoro-carbons can be used with advantage at the low temperature end of power generation cycles. Two applications are examined in a gas turbine binary cycle, which offers a compact plant of good efficiency for moderate load factor only, and a steam turbine binary cycle which allows the capacity of single shaft machines to be raised above 1000 MW. The attractions and problems of such cycles are discussed and the factors leading to the selection of a suitable fluid outlined.

The paper seeks principally to illustrate the range of turbine development problems posed by the thermodynamic and other properties of the preferred fluid. Factors influencing the choice of turbine type and detailed blading profile are examined. Preferred designs are evolved and performance estimates made.
Research on the Hydraulic Coupling
Authors: Rolfe G. H.
Published: October 2007

A short account of the origins of the hydraulic coupling is followed by a description of a production model and its method of operation. Tests have been carried out both on a transparent plastic model and on the full-scale production coupling. From the author's experience of the design and application of hydraulic couplings a mathematical analysis is made which uses conventional design formulae and general roto-dynamic theory. Dimensionless parameters and empirical laws are established which are useful in the prediction of design performance, and an examination of fluid friction and shock losses is made. Sample calculations on production couplings using the derived theory show close agreement with actual practice. A short description of a proposed test rig and future lines of experiment is appended.
Bio-Engineering Approach to Stereotactic Surgery of the Brain
Authors: Dawson B. H. , Dervin E. , Heywood O. B.
Published: October 2007

Surgical treatment of Parkinsonism and other diseases affecting the control of movement involves destruction of certain structures deep within the brain substance. Striking relief of many of the more distressing symptoms of these movement disorders follows successful surgery.

Many problems of an engineering nature are encountered by the neurosurgeon when directing instruments towards deeply situated structures in the brain.

Some of the techniques and equipment developed as a result of collaboration between the Neurosurgical Unit at the Salford Royal Hospital and the Mechanical Engineering Department of the University of Salford are described, and in particular the development of a three-dimensional monitoring system for the guidance of the surgical instruments is outlined.
An Opposed Piston Rapid Compression Machine for Preflame Reaction Studies
Authors: Affleck W. S. , Thomas A.
Published: October 2007

Mixtures of fuel and air ignite spontaneously if exposed to sufficiently high temperatures. Such ignition is not an instantaneous event, and there is always a delay of chemical origin between the establishment of the particular conditions of temperature and pressure and the rapid, exothermic chemical reactions that constitute ignition. This delay is of outstanding importance in any fuel application in which spontaneous ignition plays a part. It is determined by the progress of the near-isothermal chemical processes that precede ignition, and these processes therefore merit continued study.

This paper describes the development of an experimental technique which allows these studies to be extended to much higher pressures than those accessible in glass vessels, while retaining many of the advantages of laboratory vessel experiments. This technique is centred on a rapid compression machine of novel design which is used to heat and compress fuel/air mixtures to conditions near those in a knocking engine. After this compression process, which occupies a few milliseconds only, the hot, high pressure charge is held at constant volume while thermochemical, spectroscopic or analytical observations are made.

The principal new developments in the machine are the use of twin opposed pistons for compression with an associated hydraulic synchronizing system and a precisely triggered valve that enables rapid quenching and sampling of the reacting mixture to be made at an appropriate stage of reaction.
Forced Vibration and Chatter in Horizontal Milling: An Investigation Using a Structural Model
Authors: Sutherland I. A. , Andrew C.
Published: October 2007

This paper describes an investigation into the characteristics of, and interaction between, forced vibration and chatter in horizontal milling. The machine tool structure was simulated by a single-degree-of-freedom structural model.

The results show that forced vibration amplitudes: (1) vary with cutter speed in a series of resonance peaks; (2) are similar for plain and climb milling, but vary with orientation between the machining direction and the axis of vibration in a different way for the two processes; (3) increase approximately linearly with feed, except at low feeds; (4) pass through maxima and minima as depth of cut is increased.

The amplitudes and frequencies of chatter are distinct from, and depend on machining conditions differently from, those of forced vibration. Peak chatter amplitudes exceed those of forced vibration, but the latter can, under certain machining conditions, exceed chatter amplitudes. Forced vibration can thus be as much of a limitation as chatter when a good surface finish is required.

It was found that the discontinuous cutting of milling suppresses the onset of chatter relative to that for continuous cutting, for otherwise identical machining conditions. This is the reverse of previous contention.
Second Paper: Design of the First Large United Kingdom Power Producing Refuse Disposal Plant
Authors: Pepé P. D. , Turner G. M.
Published: October 2007

The Refuse Disposal plant being erected at Edmonton for the Greater London Council is the first of its kind to be built in this country. It is designed to handle automatically 1333 tons of crude refuse every 24 hours, untouched by hand. The refuse is used as a fuel to produce steam for the generation of about 30 MW of electric power, the exact amount depending on the throughput and calorific value of the fuel.

A brief description of the plant is followed by the reasons and economic considerations associated with the overall concept. Later a more detailed explanation is given of those aspects of the design which were influenced by problems peculiar to refuse handling and incineration.

The roller type incineration grates and combustion chambers, which are suitable for handling metallic objects as large as bedsteads, are described and their combustion principles explained. The boilers, of which the grates and combustion chambers are an integral part, presented some problems in designing for satisfactory availability of the gas side of heating surfaces and for an economically justifiable life of certain critical parts; these problems are described and reference is made to the somewhat limited large scale experience available at the time of establishing the design. Other parts of the plant are also described where novel in design or application.
The Superposition of Longitudinal Sonic Oscillations on the Wire Drawing Process
Authors: Winsper C. E. , Sansome D. H.
Published: October 2007

Part 1: Characteristics of complete wire drawing apparatus

Part 1 describes the wire drawing machine, instrumentation and oscillatory apparatus designed to establish the effects of applying oscillatory energy to the wire drawing process. A theoretical consideration of the vibration of the equipment is included and compared with experimental data.

Tests were performed on a 3000 lbf bull-block and the oscillatory energy was supplied in a longitudinal mode from a 3000 lbf electro-hydraulic oscillator. Equipment was designed to measure drawing force, drawing torque, amplitude of die and drum oscillation, and drawing speed. Frequencies of die oscillation in the range 0–125 Hz were studied with amplitudes up to 0.070 in peak to peak.

A study of process parameters, such as natural frequency of the system, damping of the bull-block drive, torsional oscillation of the drum, and die assembly inertia, showed that the analysis was in good agreement with experimental data and that it can be used to predict the effect of oscillations on the forces and torques acting during oscillatory wire drawing.

Part 2 presents experimental data obtained from mild steel, hard aluminium, stainless steel and hard copper. Results show that there is no reduction in the peak drawing force and negligible reduction in the coefficient of friction. The results also confirm that oscillatory drawing is a mechanical process of straining and unstraining the drawn wire, and that the reduction in mean force can be determined by a mechanism of force superposition.
Profiles for Low Reynolds Number Flows
Authors: Vasy G. S. , Kastner L. J. , McVeigh J. C.
Published: October 2007

The characteristics of the orifice meter are well known and have been thoroughly explored by a number of investigators over a considerable range of Reynolds numbers, yet the low Reynolds number range—i.e. below ( Re D = 4000, where ( Re) D is the upstream pipe Reynolds number, has received comparatively little attention, although recent work by two of the authors has supplemented the available data substantially. This work concentrates on very accurate measurements with small diameter orifices, but where less exacting standards of metering accuracy, e.g. ±2-2 1/2 per cent, can be allowed, a closer analysis reveals that there is a choice of orifice profiles which can be used successfully.

Consideration is also given to the recommendations of the various standardizing bodies for the allowable tolerances in the diameter of the pipeline in which the orifice meter is situated. These tolerances are often unnecessarily severe and a ‘tolerance number’ depending upon discharge coefficient and the area ratio of orifice to pipe is suggested.
The Influence of Bends on Fluid Transients Propagated in Incompressible Pipe Flow
Authors: Swaffield J. A.
Published: October 2007

The influence of a bend on the fluid transients propagated by a rapid valve closure in a long pipeline is examined by means of a short dimensional analysis and a comprehensive series of experimental tests designed to record the effects of varying in turn: the pipeline diameter to thickness ratio (7.35 to 48), pipe elasticity to fluid bulk modulus ratio (0.27 to 93.6), the restraint applied to the pipeline, the bend radius of curvature to pipe bore ratio (0 to 5), the included angle of the bend (0° to 135°) and the initial flow velocity.

From these tests the influence of a bend is found to be solely dependent on its geometry. Empirical formulae are proposed which express the reflection and transmission of a transient at a bend in terms of the bend radius of curvature to pipe bore ratio and included angle. The formulae are tested by varying both the angle and curvature of a series of bends mounted in turn in a steel pipeline and found to be accurate within the limits of measurement possible.

A method designed to predict the effect of a multiple bend made up of a series of bends the individual reflection and transmission coefficients of which were known or predictable is tested and found to be accurate to within ±7 per cent.
Asymmetrical Lap and Other Non-Linearities in Valve-Controlled Hydraulic Actuators
Authors: Montgomery J. , Lichtarowicz A.
Published: October 2007

The results of a theoretical investigation into the effect of asymmetrical lap on the open-loop performance of valve-controlled hydraulic actuators are presented. The governing differential equations of the system are developed in a non-dimensional form. The effects of supply lap and exhaust lap on actuator peak pressures, ram amplitude and cavitation, as well as the effect of inertia load on actuator peak pressure and output amplitude, are shown. When the open-loop frequency response of the hydraulic servomechanism is attempted experimentally the ram drifts until it hits its stops. In previous theoretical analyses this effect has not been noted. This paper demonstrates that the inclusion of a term ignored in previous work highlights this effect. This same term is shown to give a kind of feedback when the system drives a vertical inertia load.
Realistic Fatigue Testing and Its Significance in Vehicle Component Design
Authors: Booth R. T.
Published: October 2007

Current methods of design and development of motor vehicles tend to be limited by lack of knowledge both of the intensity of loading likely to be encountered in service and the endurance of components subjected to these loads. Conventional constant-amplitude fatigue tests are a vast simplification of the random fluctuations of stress usually found under operating conditions and predictions of service endurance based on the results of these tests will be of uncertain value until the relation between conventional tests and reality has been established.

At the Motor Industry Research Association investigations are now being made into the effects of variable load patterns on fatigue life, and the characteristics of service stresses are being determined. Because of the cost and complexity of testing full-size components, a ten-station electromagnetic fatigue machine has been developed for work on small laboratory specimens. Much of the basic information is being obtained with these specimens, and it is hoped that confirmatory tests will be carried out later on full-size components. On the ten-station machine fatigue tests have been carried out with service load patterns recorded on magnetic tape, and the results have been compared with constant-amplitude, stationary-random, and block-programme load histories. It is hoped that fatigue-test results obtained with this machine will assist in the development of realistic test procedures, and contribute to the knowledge of cumulative damage, thus shedding light on the problems of vehicle-component design.
Mankind and Manufacture
Authors: Galloway D. F.
Published: October 2007

The address is in two parts. The first scans briefly the birth and history of manufacture and its influence on mankind from antiquity to the twentieth century. The second part reviews the present situation and commitments of mankind and the contribution of manufacture towards meeting those commitments.
Second Paper: The Correlation of Cavitating Performance for a Centrifugal Pump Handling Various Liquids
Authors: Chivers T. C.
Published: October 2007

Following a specific model for the behaviour of a centrifugal pump under advanced cavitation conditions a parameter is derived for the correlation of pump performance when handling different liquids. The parameter's development is based on bubble growth theory, assuming that for the cavitation condition being investigated the bubble radius is much greater than that of the initial nucleus. Published data for a 3 per cent loss in pump head are then used to evaluate the parameter, and to compare it with the ‘thermal parameter’ and that suggested by Barenboim. Whilst all three parameters are reasonably successful with Salemann's data, all fail with Spraker's data. The author then argues that since the data are for limited cavitation conditions a strong Reynolds number influence can be expected, and it is shown that the product of this number (with an empirical fractional exponent) and the derived parameter results in good correlation for each pump. It is expected that the magnitude of the exponent will decrease as the degree of cavitation increases.
Active Compensation of Lightly Damped Electrohydraulic Cylinder Drives Using Derivative Signals
Authors: Bell R. , De Pennington A.
Published: October 2007

The dynamic response of a cylinder drive is considerably influenced by the mechanical damping at the load. This paper discusses the use of acceleration and pressure transducer signals to introduce active damping into drives where the load mass is supported on anti-friction bearings, i.e. where the inherent mechanical damping is a minimum. The analysis is based on the use of a linearized model. The significance of the model and the system analysis is substantiated by the results of experiments carried out to assess the merits of these forms of minor loop compensation.
Effect of Vibration on Condensation Heat Transfer to a Horizontal Tube
Authors: Dent J. C.
Published: October 2007

An exploratory study was carried out on the condensation of air-free steam at a pressure slightly above atmospheric, on a horizontal condenser tube vibrating in the plane of the gravitational field. Experiments conducted in the frequency range 20-80 Hz with maximum amplitudes up to 0.17 in, showed that the condensation heat transfer coefficient increased with increasing intensity ( af) of vibration, up to a maximum of about 15 per cent, above the vibration-free value. A perturbation analysis verified the experimental findings. Because of the small observed increases in heat transfer, it can be concluded that tube vibration effects on condensation heat transfer in power plant condensers will be negligible.
Governors with Load Sensing
Authors: Webb C. R. , Janota M. S.
Published: October 2007

Load-sensing governors have become a commercial reality since the 1939-45 war, but their use appears to have been restricted largely to applications where the load is an electrical machine.

The need to reduce transient speed errors in order to maintain constant frequency during large load changes in electricity generation and computer applications is well recognized.

This paper reports on improvements made in the performance of speed governors, by the addition of load sensing, when applied to normally aspirated reciprocating internal combustion engines. Its aim is to stimulate interest amongst engineers seeking improvement in the transient performance of various kinds of governed machinery.

A simple linearized theoretical treatment of the load-sensing control system, which predicts, approximately, the behaviour of a real system, is presented in this paper. Experimental tests, carried out on automotive 4-stroke petrol and diesel engines, indicated that load changes could not occur with absolutely zero temporary droop, and that the test arrangement was more stable at high loads. Comparison of transient performance with and without load sensing showed that the 10 per cent temporary droops, required by B.S. 649 and B.S. 3109, was never achieved without load sensing. With load sensing, an improvement by a factor of 4 was recorded, reducing the temporary droop below the requirements of the specifications.
Effect of Environment and Hold Time on the High Strain Fatigue Endurance of 1/2 Percent Molybdenum Steel
Authors: White D. J.
Published: October 2007

Results are presented of high strain bending fatigue tests on 1/2 per cent molybdenum steel in air and in a vacuum in which the effect of introducing a hold period in the position of maximum strain was investigated. The environment exerts significant effects on high strain fatigue endurance both at room temperature, where the life in a vacuum was twice as great as in air, and at elevated temperature. The considerable reduction in life in continuous cycling in air at 500°C is due almost entirely to oxidation since tests in a vacuum restored the endurance to values comparable with those obtained in a vacuum at room temperature. The introduction of air into a continuous cycling test in vacuum at 500°C reduced endurance by a larger factor than when a 30-minute hold period per cycle was introduced into such a vacuum test. This suggests that under the conditions stated oxidation has a greater influence on fatigue resistance than creep. Significant reductions in endurance were found with hold time but not in continuous cycling when the temperature was raised from 500C to 550°C and this is consistent with the poorer creep rupture strength and ductility at the higher temperature.
Study of Erosion by Solid Particles
Authors: Goodwin J. E. , Sage W. , Tilly G. P.
Published: October 2007

The influences of the impacting velocity and the nature of the particles on the erosion of different materials have been studied using a vacuum whirling arm rig. The most important characteristics of natural sand were found to be the size distribution and percentage of quartz present. For artificial abrasives used in industrial processes, erosion can be related to the hardness and sharpness of the particles. Tests on steel and nylon using quartz indicate that there is a fundamental dependence on particle size whereby comparatively little damage is caused by particles up to ˜ 5 μ but larger sizes cause successively more damage till a saturation condition is reached. This dependence is shown to be most important for the design of filter systems for helicopters and other vehicles whose engines suffer through ingestion of dust. Erosion is found to be dependent on a simple power of velocity. For small particles the exponent is 2.0, but for particles bigger than ˜ 100 μ it is 2.3 for a wide range of conditions. The eroding particles are found to incur a substantial degree of fragmentation which is dependent upon the initial sizes and the velocity of impact. It is suggested that the extent of fragmentation of the particles as well as the properties of the target material are important in determining the erosion behaviour.
Extrusion of Bimetallic Strip from Separate Containers
Authors: Whitlock B. C. , Alexander J. M.
Published: October 2007

Research has been continued into the production of bi-metallic strips by extruding two dissimilar metals from separate containers through a single die. Tin was extruded with lead at room temperature and copper with silver at approximately 750°C. Satisfactory pressure welding was achieved with bond strengths at least equal to the strength of the weaker metal. Within limits, adjusting the speeds of the extrusion rams produced corresponding changes in the relative proportions of the component metals in the extruded strip without impairing the bond strength. Limit analysis techniques and slip-line field solutions were used to estimate extrusion pressures and interfacial stresses.
High Strain Torsion Fatigue of Solid and Tubular Specimens
Authors: Miller K. J. , Chandler D. C.
Published: October 2007

A stress-strain history theory is developed for the entire life of solid cylinders subjected to reversals of torque under low-endurance fatigue conditions. Thin tubes and solid cylinders of a hot rolled mild steel are found to have identical stress range versus strain range relationships. However, fatigue behaviour is dependent on the stress field surrounding the crack initiation zone and hence the geometry of specimens has a most important effect in high strain fatigue processes. Cold drawn mild steel tubes that have an internal to outside diameter ratio in excess of 0.5 have reduced lives because of the absence of the constraining, less highly stressed core.
Teaching of Hydrodynamic Lubrication Using Scaled Models
Authors: Cameron A.
Published: October 2007

It is very helpful when lecturing to have teaching aids which illustrate the principles involved. The design system behind Micheli pad and journal bearing test rigs is described and the machines themselves are illustrated.
A Polarization Interferometer for Density Measurements in Compressible Flow
Authors: Kamutzki B. H. , Griffiths R. T.
Published: October 2007

Polarization interferometry is an optical technique utilizing birefringent devices in conjunction with polarizers to generate interferograms which lend themselves readily to quantitative analysis. The need for two physically distinct light beams as used in the classical Mach-Zehnder interferometer is eliminated, making a much simpler optical arrangement possible. The ease of application of the technique, together with the low cost of the component parts, means that the polarization interferometer can be used to advantage in preference to the classical interferometer in all cases except those where extreme accuracy is the overriding criterion.
Second Paper: An Investigation into the Effects of Pre-Heat Temperature on Ductility in a Warm Heading Process
Authors: Thomason P. F.
Published: October 2007

Two-stage warm heading operations were carried out on a mild steel and three high tensile bolt materials (types 1, 2 and 4 from B.S. 3111:1959) at pre-heat temperatures in the range from ambient up to 600°C. The tests were carried out in the form of a transfer process (approximately 2 seconds delay between stages) and also as an interrupted process (approximately 30 minutes delay between stages). Artificial surface defects of various depths were machined on the heading specimens to aid measurements of the change in ductility with increase in pre-heat temperature. The method consisted of estimating the critical depth of groove which would be just on the point of fracture at the end of a particular heading operation.

The steels tested were found to have low ductility at pre-heat temperatures in the range from 200°C to 300°C; at a pre-heat temperature of 600°C the steels exhibited extremely high ductility. The results suggest that rolled bar of relatively poor surface quality could be warm headed at 600°C without fracturing.

A solid film of colloidal graphite and a high chlorine oil were both found to be satisfactory lubricants at all specimen pre-heat temperatures up to 600°C.
Unsteady Air Flow between Two Discs at Low Velocity
Authors: Garcia C. E.
Published: October 2007

Velocities of air flowing between two discs were measured with a hot-wire anemometer where flow was induced with a steam ejector. Inward and outward flow were found to be unsteady, but outward flow unsteadiness was greater. This is due to the diffusion nature of the flow.

A solution to the cylindrical wave equation was obtained and showed that, within the assumptions of the equation, a steady radial flow field becomes unstable upon passage of a wave due to a step function change of velocity at the boundaries of the flow.

Comparison of a power spectrum of recorded data with one of turbulent air flow in a pipe showed the oscillations to be dissimilar. Unsteady motions seen in other studies of radial flow are also discussed.
Cavity Formation in Valve Controlled Hydraulic Cylinders
Authors: Mccloy D.
Published: October 2007

Solutions are developed of the non-linear equations describing the response of a valve driven hydraulic actuator to step inputs. Compressibility is neglected but cavitation is taken into consideration. It is shown that under certain conditions cavities can exist on both sides of the actuator piston. It is argued that there is no good reason why hydraulic servos should not be operated in a cavitating mode. The effects of cavitation on dynamic response and the possible effects of cavitation damage are discussed.
Stochastic Models for Hydrodynamic Lubrication of Rough Surfaces
Authors: Christensen H.
Published: October 2007

This paper deals with hydrodynamic aspects of rough bearing surfaces. On the basis of stochastic theory two different forms of Reynolds-type equation corresponding to two different types of surface roughnesses are developed.

It is shown that the mathematical form of these equations is similar but not identical to the form of the Reynolds equation governing the behaviour of smooth, deterministic bearing surfaces.

To illustrate the functional effects of surface roughness the influence on the operating characteristics of a plane pad, no side leakage slider bearing is analysed.

It is shown that surface roughness may considerably influence the operating characteristics of bearings and that the direction of the influence depends upon the type of roughness assumed. The effects are not, however, critically dependent upon the detailed form of the distribution function of the roughness heights.
Performance of Inward Radial Flow Turbines under Steady Flow Conditions with Special Reference to High Pressure Ratios and Partial Admission
Authors: Wallace F. J. , Cave P. R. , Miles J.
Published: October 2007

The paper describes an extension of an earlier and very successful one-dimensional analysis by one of the authors (reference (1)) for design and off-design performance evaluation of inward radial flow turbines to include four cases not covered by the earlier analysis: high overall pressure ratios leading to either nozzle or rotor choking; partial admission; variable nozzle angle; allowance for nozzle and rotor loss coefficients (references (2) and (3)). Each of these extensions of the original theory has been programmed in FORTRAN. The full admission results are compared with performance measurements obtained on a C.A.V. type 01 turbine in conjunction with a specially designed high-speed dynamometer for pressure ratios up to 1.6, the analysis being extended to a maximum value of 4.0.

The partial admission results are compared with experimental results reported in reference (4). The variable nozzle angle results are given as an example of the flexibility of the method. Finally, the loss coefficient treatment of Benson (reference (2)) which was based on reference (1) in conjunction with experimental results reported in reference (5), is applied to the full admission tests of the present paper.

The object of the paper is to give a comprehensive account of the power of the one-dimensional treatment as a design tool, with the inference that two-and three-dimensional treatments (references (6)-(9)) are basically more suitable for detailed flow analysis rather than basic design.
Electric Power Production in Italy
Authors: Angelini Arnaldo M.
Published: October 2007

This paper is a survey of power generation and installed capacity in Italy since the beginning of the century to date, with reference to the contribution and relative incidence of the various primary sources exploited. It includes a summary review of the evolution of the main characteristics of hydro plants designed for power generation and regulation, fossil-fired steam power stations, and nuclear power stations, with reference to the structure of the station and to the rating and main features of the generating units. Prospects are discussed and the foreseeable evolution of (a) generating plants in relation to the availability and competitiveness of the primary sources of energy; and (b) hydroelectric plants for power regulation.
Management in the Engineering Disciplines
Authors: Cary Michael
Published: October 2007

The increasing number of specialized disciplines in engineering presents increasing problems to management. In cases of difficulty the manager either has to consult even more specialized experts, or take decisions himself in fields in which he has no particular competence. Good management in practice turns more on judgement of character than on any particular background or course of training. The availability and future development of computers may offer the chance of a breakthrough. By carrying out many processes that now form part of the professional syllabus, the computer could make it possible to cover in a single course groups of subjects now requiring separate courses; professional work would be more broadly based, and increasingly concentrated on value judgements. A much more generalized first degree course and later specialization not on single subjects but on related groups could evolve.
An Analysis of the Control Mechanism Used in Variable-Delivery Hydraulic Pumps
Authors: Green W. L. , Crossley T. R.
Published: October 2007

Variable-delivery high-pressure hydraulic pumps are usually controlled by a small servo actuator fed from the pump-generated pressure. The actuator consists of a three-way valve and differential-area jack or a four-way valve and equal-area jack.

This paper analyses the effect of perturbations of the generated pressure when the pump is part of a system incorporating a relief valve. It is demonstrated that, because the load on the servo jack can be a function of the generated pressure, the ‘closed loop’ formed can be unstable.

In particular, the three-way-valve actuator is shown to be sensitive to perturbations in its supply pressure even when the load is independent of pressure.

Frequency-response diagrams are presented, the assumptions made in the analysis are clearly discussed, and design recommendations are made in the light of the analytical results.
The Teaching of Machine-Tool Technology at University Level
Authors: Koenigsberger F.
Published: October 2007

In this paper the problems of introducing the teaching of a specialized subject into undergraduate courses are discussed with particular reference to the specific features of machine-tool technology. These cover the facts that the machine must be considered as part of an overall manufacturing system, so that the concept of performance differs from that encountered in other types of machinery such as internal-combustion engines, and that technological, economic, and human aspects must also be considered. Comparisons are made between Continental, particularly German, practice and present practice in some British universities. Some typical approaches to the organization of postgraduate full-time courses and short-term specialized courses are given. Finally, a comparison is made between the employment of university trained engineers in the machine-tool manufacturing and using industries in Great Britain and in Germany.
The Dynamic Transfer Characteristics of Reciprocating Engines
Authors: Bowns D. E.
Published: October 2007

The methods of sampled data analysis and small perturbation techniques are used to predict the dynamic characteristics of reciprocating engines. Extensive frequency response tests have been carried out on a compression ignition engine to determine the engine dynamic characteristics and the results agree well with the theoretical predictions. A method of plotting the results is suggested which has the advantage of generality and takes into account engine speed changes and load torque-speed characteristics.

The experimental methods used involve the use of electro-hydraulic systems. These have great advantages for providing the appropriate input and loading conditions.

Whilst the main body of the report is concerned with the theory and testing of compression ignition engines, the methods suggested can be applied equally well to petrol engines.
Pre-Service Component Testing of Steam Power and Process Plant
Authors: Morton A. J.
Published: October 2007

The high performance increasingly required of modern plant leaves smaller margins for error in design and makes the plant more sensitive to unforeseen phenomena. This shows itself in many industries in a high incidence of teething trouble, bringing heavy financial loss to the purchaser and discouraging further innovation.

The remedy is more thorough design and development and, wherever possible, the full-scale on-load prototype testing of complete plant items before delivery, so as to expose and eliminate teething troubles and to provide the designer with an accurate record of the behaviour of the plant. It is in the purchaser's interest to make such testing a requirement of the contract.

Adequate test facilities are at present lacking and can seldom be provided by individual manufacturers. A permanent fully equipped test facility has great advantages compared with ad hoc testing arrangements in various locations, and the paper proposes the establishment of publicly operated testing and development stations to serve various industries. The equipment and procedure of such a station to serve the steam power and allied industries are examined.
The Development of a High-Performance Motor-Cycle Engine
Authors: Blair G. P. , Johnston M. B.
Published: October 2007

The design of medium capacity, high specific output, two-stroke cycle engines is of increasing interest due to the expanding market for motor cycles and leisure vehicles, particularly in the United States. It is felt that there is a growing need to apply modern techniques to this design process, which covers the entire spectrum of mechanical engineering from fluid mechanics to stress mechanics. This paper describes the effective utilization of a high speed digital computer for those calculations connected with the unsteady gas dynamics of flow in the exhaust and transfer systems, the stressing of the connecting rod, the balancing of the crankshaft, the design of the combustion chamber, and the analysis of the porting of other high-performance engines so that an information library is stored. A method of experimentally determining loop-scavenging efficiency is evaluated. Further, a unique method of asymmetrically timing the inlet process of a two-stroke cycle engine is described and its initial development reported. The design of a complete engine, of 250 cm3swept volume, is detailed and its road and test-bed performance characteristics appraised. The engine produces 180 hp/litre as a specific output, at initial testing.