bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
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.
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.
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.