bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Slip-Line Field Solution for Machining with Discontinuous Chips
Authors: Ho W. S. , Brewer R. C. 
Published: October 2007

The importance of establishing a realistic model of the title problem is stressed, and this is achieved by studying the process experimentally using ciné photography. Development of the discontinuous chip was traced carefully during the whole cycle of its formation and disposal, particular attention being paid to the extent and history of the plastic zone, and subsequent fracture and crack propagation. It was interesting to observe that for the material considered, namely low carbon steel, the surfaces of the crack and chip were all sensibly straight, and cutting of the next chip began before separation of the one under consideration. It is suggested that discontinuous chip machining could perhaps be used as a method of evaluating strain rate dependencies in fracture mechanics in the same way that continuous chip machining offers possibilities for deriving stress-strain curves at high rates of strain.
Fracture Behaviour of Two Creep-Resistant Materials Subjected to Cyclic Loading at Elevated Temperature
Authors: Tilly G. P. 
Published: October 2007

An alloy steel and a nickel-chromium alloy are shown to exhibit similar fatigue behaviour over a wide range of temperatures. Endurances tended to be time-dependent at elevated temperatures, and repeated-tension cycles were found to be more damaging than push-pull but less damaging than static-tension (creep). The behaviour was reversed at room temperature where failures tended to be cycle-dependent (number of cycles to failure independent of applied frequency) and creep loading was least damaging. Rupture data for repeated-tension tests at approximately 10 c/min were analysed by a creep technique. For a wide range of temperature, the expressions fitted the experimental points encouragingly closely and the technique appears to be a useful method of describing this type of data. Tests at room temperature having more than 104 cycles to failure were premature with respect to the analysed family of curves and this was attributed to failure occurring by a predominantly cycle-dependent mechanism. Fractures at higher stresses exhibited a ductile appearance attributed to a different fracture mechanism. Time-dependent behaviour was enhanced by increase in the peak tensile stress, tensile mean stress, and temperature, or by decrease in cyclic frequency.
Two Papers on Engine Cooling First Paper: The Cooling of Diesel Engines by Water under Pressure
Authors: Gratzmuller J. , Davies S. J. 
Published: October 2007

Water cooling in diesel engines is studied, with particular reference to the application of these engines in locomotives of high power. In this context, problems relating to weight, volume and radiator design become progressively more difficult to solve with the tendency towards increased unit powers. In the solution considered the water in the cooling system is put under a high static pressure, which makes it possible to raise the water temperatures above the usual levels. Resulting from this, the formation of steam bubbles is reduced or eliminated, ‘cavitation corrosion’ is reduced considerably, and cavitation in the water pump is prevented. Water consumption is markedly reduced. Standard equipment for locomotives is described. Cooling the supercharge air and the lubricating oil at relatively low temperatures is compatible with cooling the engine at a high temperature if two cooling circuits are used, with their radiators placed in series in the cooling air current. The case of cooling engines of high supercharge is examined; in these, the heat taken from the admission air and from the lubricating oil exceeds that taken from the engine. Future designs of heating and cooling systems for engines with very high supercharge are proposed.
Third Paper: Elastohydrodynamic Lubrication of O-Ring Seals
Authors: Hooke C. J. , Lines D. J. , O'Donoghue J. P. 
Published: October 2007

The paper presents a theoretical solution to the ideal problem of an O-ring seal constructed of an isotropic elastic material moving at a constant axial velocity along a cylinder. By means of a standard solution for the elastic distortion of a circular section, and the inverse hydrodynamic theory proposed by Dowson and Higginson, compatible solutions for the hydrodynamic pressure and film shape between the seal and cylinder walls are obtained. It is shown that with a typical seal section taken from British Standard, with standard groove dimensions and ‘nip’, the sealing pressure, which is defined as the difference between the maximum pressure under the seal contact and the sealed pressure, remains independent of the sealed pressure. The net leakage past the seal, which is the difference between the fluid flow across the seal when it is ‘pumping’ against the pressure and that when the seal is ‘motoring’ or moving with the pressure, is shown to increase with sealed pressure. The results are presented in non-dimensional form to generalize their application.
Second Paper: The Practical Applications of Theoretical Studies to the Tilting Pad Gas Bearing
Authors: Corniglion J. 
Published: October 2007

In order to exploit the well-known advantages of gas bearings, it is necessary to be able to optimize each individual design. The non-linearity of the basic Reynolds equation makes this difficult. The application of numerical methods is tedious and expensive. Analytical solution can be obtained by making certain basic assumptions and linearizing the equation. An interesting way to linearize the Reynolds equation is the ph solution found by Ausman on his work on plain journal bearings. An extension of this method has been done by Pitts, for tilting pad bearings. The aim of this paper is to compare the analytical solution with the experimental results, and so ascertain the validity of the hypothesis. During the experiments the influence on the shape and thickness of the gas film of the parameters (load, speed, bearing size, clearance and pivot location) has been studied. It is shown how a choice of pad may be made to fulfil a certain requirement.
Passive Temperature Control System for An Aerospace Instrument
Authors: Walker G. , Wolf Ludwig 
Published: October 2007

In aerospace instruments, the problem of temperature control can become severe because convettive cooling cannot be used; heat must be transferred by radiative means alone. Systems are exposed to a rigorous thermal environment and there are strict limitations on the power, weight and volumes available. A surprisingly high degree of temperature control can be accomplished, however, by the use of a passive system of spectrally selective surfaces. In this paper, one approach to the design of passive temperature control systems is discussed by detailed reference to an instrument intended for use on the lunar surface.
First Paper: Plant Aspects of Turbine Generator Foundations
Authors: Flint I. J. 
Published: October 2007

The paper begins with a description of the various types of turbine generator foundations that have been installed and those that are intended for use in the near future. Then follows a section detailing the requisite characteristics of machine foundations and the factors that must be considered in order to obtain satisfactory operation. As the foundations support rotating machinery, the subject of vibration is discussed, including fundamental equations and their practical applications to the problem of calculating frequencies in the structures. Among the many factors that have to be considered when selecting the type of foundation are the size of machine and the station arrangement. The various factors are presented with comments. Important characteristics relating to the material properties and to the erection and behaviour of steel and concrete foundations are described. The topic of alignment is considered, including methods of maintaining machine alignment relative to the foundation structure. The causes of foundation distortion and the resulting effect on the alignment of the machine are summarized and some reference is made to precompensation in anticipation of misalignment developing.
New Technique for Shear Zone Thickness Determination in Orthogonal Metal Cutting
Authors: Clack V. W. , Brewer R. C. 
Published: October 2007

The extent of the transition zone separating the uncut metal and fully formed chip in orthogonal cutting is examined. Earlier work in this field consisted of studying the magnified grain arrangement in the uncut metal and the chip, the width of the transition zone being measured at selected points. The new method attempts a more positive assessment of the extent of the transition zone by the use of micro-hardness explorations along a series of generators running parallel to the sides of the chip, and passing through the shear zone into the workpiece. The transition zone and adjacent metal are thus covered with a network of indentations pitched a few thousandths of an inch apart. As the variation in the size of the indentations is a measure of the work-hardening of the metal, it follows that, once the average hardness values of the uncut metal and the fully formed chip have been established, the transition zone is, in principle, defined by the location of those hardness values which lie between the average hardness values accepted for (1) the uncut metal and (2) the fully formed chip. In order to find the width of the zone through which a definite increase in hardness occurs, four different methods have been investigated and the results are included. One of the methods gave satisfactory results on all the samples tested.
Influence of Free Surface Environment on the Shear Zone in Metal Cutting
Authors: Barlow P. L. 
Published: October 2007

It has previously been suggested that the reduction in cutting forces obtained by the presence of fluids such as CCl4 on the backface or free surface of the forming chip was due to diffusion of the fluid into the body of the chip in the region of the shear zone. In the present work, experiments with carbon tetrachloride tagged with carbon-14 and with carbon tetrachloride tagged with chlorine-36 were performed with the object of assessing the extent of diffusion of lubricants into the chip when present on the free surface only. The results obtained disprove former hypotheses and suggest that the reduced cutting force is due solely to chemical reaction at the surface of the chip. Confirmation of the sensitivity of the surface of the deforming shear zone to change in surface condition was obtained by removing metal from this region by an electropolishing technique during slow speed cutting. By varying the electropolishing conditions increased or decreased cutting forces could be obtained. It is proposed that the result both of chemical reaction at the surface and of surface removal is to reduce the strain-hardening rate of the metal undergoing shear by reducing the surface barrier to the flow of dislocations out of the metal. The association of the surface reaction of carbon tetrachloride with a change in the strain-hardening characteristics of the metal in the shear zone leads to a classification of the backface phenomenon as a Rehbinder effect and enables this effect to be more closely defined than was hitherto possible. Evidence is also presented which indicates that the backface effect does not contribute to the reduction in cutting forces during rakeface lubrication and is therefore unimportant in practice where flood lubrication of the cutting region invariably occurs.
Influence of Engine Inertia Forces on Minimum Film Thickness in Con-Rod Big-End Bearings
Authors: Martin F. A. , Booker J. F. 
Published: October 2007

In the design of dynamically loaded bearings, the journal eccentricity will vary in magnitude and direction throughout the loading cycle. One of the designer's interests is in the trends of maximum eccentricity ratio and the corresponding oil film thickness for various bearing and engine conditions. From experience with journal eccentricity predictions for big-end bearings it has been found that the eccentricity ratio in the bearing due to the peak firing load seldom exceeds that due to the inertia load alone (although this load is smaller). Therefore, as an approximation, it is thought justifiable to neglect the gas forces. The maximum eccentricity ratio for numerous inertia load cycles was computed based on the numerical mobility method of solution (1)†; because of its simplicity and as only trends were required, the short bearing solution was used. The results of this study applied to big-end bearings show how the reciprocating and rotating masses affect the maximum eccentricity ratio. Also the effect of the ratio of crank radius to con-rod length is investigated, as is the effect of change in bearing clearance. A useful general-purpose graph is presented which will enable the designer to estimate comparative values of minimum oil film thickness over a practical range of bearing operating conditions. It is emphasized that the value of oil film thickness by itself may not be very helpful if used in absolute terms, as its correctness will depend on the assumptions made. The general results will, however, be useful if used as a comparator, and should give some guidance on how to improve the performance of connecting-rod big-end bearings.
Nominated Lecture: Performance and Operation of Spark-Ignited Gas Engines
Authors: Land Malcolm L. 
Published: October 2007

The author discusses the application of spark-ignited gas engines to such services as gas transmission, gas gathering and chemical processing with integral angle engine-compressors as well as directly coupled units. The author also treats such performance aspects of two-and four-stroke cycle spark-ignited gas engines as: fuel consumption, cyclic dispersion in combustion, accommodation of ambient temperature variation, load variation and altitude. There is an extended discussion of pulse and constant pressure turbocharger characteristics and their influence on engine performance. Important hardware considerations are given, such as design of valves and valve inserts, cylinder heads and pistons.
Acoustic Isolation of Fans in Ducts
Authors: Roberts A. W. , Luxton R. E. 
Published: October 2007

A method of reducing the sound power radiated downstream from axial flow fans is described and investigated. The normal parallel duct fan housing is replaced by a contoured arrangement. With one type of contour and the use of porous absorbent material the reduction in the downstream overall sound power level is 5 dB, that is, the total sound power is reduced by a factor of three. The attenuation is effective in this case over the full audio frequency range but is largest at frequencies above about 1000 c/s. The total pressure losses in each of the several contoured fan housings investigated are practically identical with those in the usual parallel housing and the fan absorbs no significant additional power. Although commercially available duct noise reduction devices may give higher attenuations than those obtained by the contouring method they usually do so at the expense of quite high total pressure losses. For example, the fan used in this investigation gives a total pressure rise of about 1.4 in water gauge and one commercial type of duct noise attenuator, suitable for use with this fan, introduces a total pressure loss of 0.25 in water gauge. Two basic types of fan housing are investigated. One housing has contoured sections upstream and downstream of the fan rotor and the other is a composite arrangement with the normal parallel duct intake and a contoured downstream section. The effect of the presence of absorber on the performance of these basic types is determined. The acoustic performance of each type of fan housing duct is compared by the use of an ‘in duct’ method of sound pressure measurement. It is stressed that the design of low noise fan/duct systems is economically feasible provided sufficient effort is exerted to find a satisfactory compromise between the required aerodynamic and acoustic performances.
Theories and Experiments on Tube Sinking through Conical Dies
Authors: Moore G. G. , Wallace J. F. 
Published: October 2007

Earlier theories of tube sinking through conical dies have been considered and the factors important in the calculation of stresses and strains have been determined. Using these theories drawing stresses have been calculated for a particular stress-strain curve by assuming an exponential strain hardening characteristic. These drawing stresses are essentially ‘lower bounds’ but comparative ‘upper bounds’ have been obtained using velocity field techniques; Coulomb friction has been included. Thickness strains for a smooth die and a non-strain hardening material have been computed. Experimental data has been obtained using conical dies under normal industrial conditions and comparisons made with theory. In addition, the problems encountered in the inlet and exit of the die are discussed. It is suggested that drawing stresses and thickness strains determined for conical dies can be applied to other die profiles when the die inlet semi-angle does not exceed 15°.
Fire-Resistant Fluids for General Hydraulic and Steam Turbine Systems
Authors: Wilson A. C. M. 
Published: October 2007

Major items of C.E.G.B. power plant are now being designed to operate at high steam temperatures and hydraulic pressures. In consequence, the risk of fires due to leaking petroleum lubricants is increasing. Suitable fire-resistant (f.r.) fluids are therefore desirable. Some of these have, however, given rise to difficulties in service due to changes in their physical and chemical properties. The physical properties of non-aqueous synthetic f.r. fluids (i.e. phosphate esters and chlorinated diphenyls) have been surveyed, and their chemical stability and anti-corrosion properties determined. Whilst the physical properties of the phosphate esters are better than those of the chlorinated diphenyls the chemical stability and corrosion properties are much worse.
First Paper: Extrusion of Aluminium and Copper
Authors: Austin E. R. , Davies R. , Bakhtar F. 
Published: October 2007

This paper describes the results of cold backward extrusion tests on aluminium and copper specimens, using test rigs in which impact velocities up to 300 ft/s could be obtained. The maximum energy available was 10 000 ft lbf, but for the work described here, 6000 ft lbf were adequate for the extrusion of billets of 1-in diameter, 1.5-in long. Comparison was made with extrusion at very low speed, and the effect of impact velocity on extrusion pressure and mean work of deformation assessed. For aluminium, reductions of area of between 44 and 86 per cent were examined. Surprisingly little variation in deformation energy over the speed range was noted, but the optimum impact speed appeared to be in the region of 50-80 ft/s. In the case of copper, where impact speeds up to 240 ft/s were investigated, the optimum impact velocity was about 60 ft/s. A limited series of tests in combined forward and backward extrusion was also carried out in both materials. It was found that both reduction in area and impact velocity had a marked effect on the relative proportions of metal extruded in the two directions. Mention is also made of metallurgical examination into the effect of high-speed working on the properties of extruded metals.
Calculation of Flow through Cascades of Blades Having Relative Motion and the Generation of Alternating Pressures and Forces Due to Interaction Effects
Authors: Parker R. 
Published: October 2007

A method is given for calculating the incompressible flow of a perfect fluid through multiple cascades of blades with one or more cascades moving relative to the frame of reference. Finite differences are used and the stream function evaluated by relaxation. From this velocities and pressures are calculated throughout the field for a sequence of relative blade positions allowing the spatial and time variations to be obtained. The method is applied to an i.g.v.-rotor combination with three values of axial spacing. The results show that the mechanism of blade row interaction is that the i.g.v. prevents accelerations of the fluid in the direction normal to the i.g.v. camber line which would occur if the i.g.v. were not present. The resultant pressure differences across the i.g.v. are the primary source of alternating forces and provide sources of discrete frequency noise at typical blade row axial spacings. The present investigation is confined to the near field and estimation of noise radiation is beyond its scope; however, if the analysis is used to design blades producing the minimum fluctuating pressures, relatively low noise radiation should result.
Research on Solid Lubricants for Use within Gas-Cooled Power Reactors
Authors: Parry A. A. , Mitchell L. A. 
Published: October 2007

The gas-cooled power reactors operated by the C.E.G.B. are refuelled on-load. Thus there are a number of devices which operate in the coolant, and solid lubricants offer an attractive solution to the lubrication problems encountered. These problems are discussed, and the characteristics of suitable lubricants are elucidated. The main requirement is that of long lifetime at constant (but not necessarily extremely low) friction. Present solutions to some of the problems are described, and their limitations are pointed out. A brief review of some possible solid lubricants is given, with an indication of the temperature ranges within which they are usable. Results of friction and endurance tests on sprayed films of unbonded molybdenum disulphide, tungsten disulphide and graphite are presented for tests at 200 and 400°C. At 400°C tungsten disulphide was the most promising lubricant, whereas molybdenum disulphide was best at 200°C. In general, lifetimes of sprayed films showed a wide scatter. Preliminary experiments on some hot-pressed composite materials containing a metallic (nickel) matrix and a lubricant powder (tungsten diselenide or calcium fluoride) are described. None of the formulations tested was fully satisfactory at 100°C or 400°C when both wear rate and friction were considered. However, all proved superior to plain nickel when rubbed against stainless steel. The important factors in the method of application of solid lubricants are not understood. It is clear that much more basic research is needed, and the directions this might take are discussed.
Second Paper: Hydraulic Lock with Single-Land Pistons
Authors: Dransfield P. 
Published: October 2007

Experiments are described in which the break-out force associated with hydraulic lock on single-land pistons is measured. The test pistons used were of 0.5-in diameter × 1 in long, with diametral clearances in their bores in the range 2-20 × 10-4 in. The pistons were subjected to axial pressure drops in the range 0-5000 lbf/in2. The finish of the pistons and bores was closely controlled as regards surface finish, roundness and parallelism. It was found in all cases that a relatively small inherent lateral force acted on the pistons. The lateral force-pressure profile was found to increase linearly with clearance. Beyond a particular pressure for each clearance used, the lateral force necessary to generate hydraulic lock disappeared. Leakage flow rates were measured and used to help assess the attitude of a test piston in its bore. An hypothesis is given which explains the presence of hydraulic lock with single-land piston configurations. The hypothesis relates the hydraulic couple due to small residual tilts of pistons in their bores, and the mechanical friction in the reaction bearing required to support the piston against axial pressure forces. Experiments designed to test the hypothesis give positive support to it.