bluuebunny/crossref_metadata_2025_split huggingface dataset:
Equivalent Elastic Properties of Perforated Bars and Plates
Authors: Duncan J. P. , Upfold R. W. 
Published: February 2007

Experimental methods are described by means of which the equivalent elastic properties of bars and plates perforated on a square, a square-diagonal or a triangular pitch (or otherwise) may be obtained. Bars of rectangular section of steel, gun metal and perpex perforated on a fixed pitch with circular holes to give a wide range in the ratio (pitch/diameter of holes) on square and triangular patterns were tested in flexure and tension. The transverse aeolotropy of such bars and plates was examined and ratios of (equivalent Young's modulus, drilled/true Young's modulus) and equivalent Poisson's ratios were found. The experimental results obtained were compared with theoretical curves of Bailey and Hicks for perforated plate of square and square-diagonal pitch and with Horvay's plane-stress theory for perforated plate of triangular pitch. Results have been presented in graphical form for ready application to the design of heat exchanger tube-plates.
On the Determination of Residual Stresses in Tubes
Authors: Denton A. A. , Alexander J. M. 
Published: February 2007

Analytical expressions are proposed, from which the circumferential and longitudinal residual stresses present in a tube may be found by measurement of changes in curvature after slitting and layer removal. The effect of variation of the tube length, previously thought to be anomalous, is satisfactorily explained by the present analysis. The methods of measuring residual stress which were proposed by Davidenkov, Sachs and Espey, and Treuting and Read, are examined in detail and are shown to be inaccurate in certain circumstances.
Damping Properties of Thin Oil Films Subjected to High-Frequency Alternating Loads
Authors: Hother-Lushington S. , Johnson D. C. 
Published: February 2007

Damping Properties of Thin Oil Films Subjected to High-Frequency Alternating Loads An investigation has been made into the energy loss in thin oil films when these were subjected to high-frequency alternating loads. Experiments were performed on oil films between two parallel plates when one of them was given a sinusoidal motion relative to the other in a direction normal to the plane of the plates. The frequencies used were in the range 400 to 4000 c/sec. The experiments showed that the energy loss is less than would be expected because of cavitation of the oil film and a qualitative theory is given which goes some way towards explaining the experimental results.
Lateral Deflections of Circular Cylinder Walls during Buckling
Authors: Ricardo O. G. , Marreco D. , Csoknyai H. 
Published: February 2007

The lateral deflections of circular cylinders with thin walls were recorded during buckling. Ten pick-up points were chosen along a transverse section of the cylinder, and their deflections recorded simultaneously. The results suggest, within the precision of the measurements made, that buckling starts simultaneously or with a delay not larger than 0·02 sec, in a large region of the transverse section. Sometimes a local buckling wave appears before general collapse, but this wave does not seem to propagate continuously towards the final shape of the buckled surface. It can also be concluded that, at buckling and after 0·01 or 0·02 sec, the wall tends directly to a stable polyhedral configuration, with a well-determined number of sides. No intermediate stage could be detected. These results are interpreted according to previous studies of one of the authors, in such a way that an explanation of the ‘jump’ phenomenon is attempted, without the necessity to pass over Tsien's ‘energy jump’.
Experimental Investigation of Free Convection in a Liquid Metal in Long Tubes
Authors: Bayley F. J. , Czekanskit J. 
Published: February 2007

This paper reports an extension of a previously published investigation into the natural convection process in a liquid metal (4), using circular tubes closed at their lower ends, operating on the thermosyphon principle of heat transfer. In this work longer tubes were used than previously and two distinct regimes of flow were observed. At low heating rates the non-dimensional heat transfer coefficient was found to be a linear function of the temperature difference, and the fluid at the lower end of the tube appeared to be stagnant, contributing negligibly to the overall heat transfer process. At higher heat transfer rates, the data followed the general trends of the previously observed flows in a liquid metal, although The Heat Transfer Rates Were At Least 17 Per Cent Less Than With Normal Boundary Layer Flow, and More Dependent Upon The Surface Geometry. This Was Due To Interference Between The Heated Boundary Layer and The Core of Cooler Fluid, and This Caused Violent Oscillations In The Temperature of The System Which Persisted Throughout The Entire Test Programme.
Studies of Flow and Heat Transfer Associated with a Rotating Disc
Authors: Richardson P. D. , Saunders O. A. 
Published: February 2007

Experimental investigation of laminar heat transfer from an isolated disc is described, account being taken of simultaneous forced and natural convection. It is concluded that results are correlated well by The influence of the radial velocity profile upon turbulent heat transfer is discussed. Measurements of the flow beyond the edge of a rotating disc are outlined, and it was found that beyond about 40 per cent of the disc radius from the disc edge the flow closely resembles that in Squire's radial jet, but with a whirl component of velocity. Details of the influence of nearby stationary planes upon the flow and heat transfer from a rotating disc are given; it is shown that the presence of such planes can considerably reduce the heat transfer.
Fluid Friction and Leakage between a Stationary and Rotating Disc
Authors: Bayley F. J. , Conway L. 
Published: February 2007

This paper describes an investigation of the flow in a narrow gap between a rotating and stationary disc with an arbitrarily imposed radial pressure difference. This system represents the conditions pertaining between the rotors and casings of many fluid machines. The investigation is mainly experimental, for although the equations of motion were derived for the fluid system in question, these were found not to be tractable for the conditions observed. Experimental results are reported from two separate test series. The first test series yielded data on the frictional and pressure forces in the system which were obtained in sufficient detail for use in design calculations for fluid machinery. In the second series the flow between the discs was studied in detail in order to explain the nature and form of the results obtained in the first series of tests.
A Set of Creep Curves from a Single Test using a Tapered Specimen
Authors: Levy J. C. , Bàròdy I. I. 
Published: February 2007

The use of a tapered form of specimen for creep testingi s described. Strains are measured on a series of short gauge lengths, enabling a family of isothermal creep curves at different stresses to be obtained from a single test. The measurement of strain is by the replica method, but other methods are not necessarily excluded. Testing of tapered specimens makes possible a considerable saving in the aggregate time and material necessary to establish a set of creep curves, with little sacrifice of accuracy. Data are presented for the aluminium alloy DTD 5070A, and results from tapered specimens compare favourably with creep curves obtained in conventional tests.
Experimental Investigation into the Effect of the Thermal Boundary Condition on Heat Transfer in the Entrance Region of a Pipe
Authors: Hall W. B. , Khan S. A. 
Published: February 2007

Experimental results are presented for forced convection in the entrance region of a pipe; the results were obtained using both the boundary condition of uniform heat flux and that of uniform temperature. A significant difference which is attributable to the different boundary conditions was observed for Reynolds numbers below about 3 times 104, but at higher Reynolds numbers the difference rapidly diminishes. An approximate numerical solution for the early stages of boundary layer formation on the pipe walls gave similar differences between the two boundary conditions as were observed in the experiment.
Influence of Pipe Friction and Heat Transfer on Pressure Waves in Gases: Effects in a Shock Tube
Authors: Bannister F. K. 
Published: February 2007

Finite-amplitude pressure waves travelling in gases in pipes are subject to the influence of pipe friction and heat transfer to or from the pipe wall. Where the pipe section is moderate or small these factors cause serious departures from the classical laws governing wave motion under frictionless adiabatic conditions. The paper presents a theoretical analysis of the effects of friction and heat transfer, assuming that at any instant and location the frictional force and heat-transfer rate in a pipe element are those for steady flow at the same Reynolds number. Based on the three-directional method of characteristics, a step-by-step procedure is developed for the solution of practical problems involving wave motion in pipes of moderate diameter, for example, in internal-combustion engine exhaust pipes. The procedure is illustrated by application to the wave motion in a simple shock tube of moderate initial pressure ratio. Experiments using such a shock tube confirm the validity of the theoretical treatment.
Analysis of Creep in Cylinders, Spheres and Thin Discs
Authors: Smith E. M. 
Published: February 2007

A method of analysing the creep behaviour of cylinders, spheres and thin discs is described, in which the effects of time variation of the environmental conditions of temperature, pressure, rotational speed and internal heat generation may be accommodated. Deformation is considered as a series of steps each consisting of a short period of steady state creep followed by instantaneous stress readjustment to resatisfy the equations of equilibrium and compatibility. The relationships for stress readjustment can be written down once for all, since they are independent of the type of creep law used and of the length of time interval taken. The simultaneous solution of these relationships is presented in a form suitable for incorporation in computer programmes.
An Analysis of Surface Wave Instability in Grinding
Authors: Gurney J. P. 
Published: February 2007

A graphical method of analysis of surface wave instability in grinding is presented. This form of instability is characterized by uneven wear of the wheel, causing surface waves to form about its circumference. A progressive deterioration in the finish of the work results, together with an increase in the level of vibration. This is a type of self-excited vibration, and is not due to inhomogeneities in the wheel. The factors affecting the number of waves which can build up are discussed. The method of analysis is applied to a cylindrical grinding machine, and the results obtained are compared with those obtained from an experimental investigation.
Small-Amplitude Vibrations of the Four-Bar Linkage Chain
Authors: Gayfer J. R. , Mills B. 
Published: February 2007

Experimental and theoretical work is described dealing with the small-amplitude dynamic characteristics of plane four-bar linkages with prismatical links, one link being fixed in space. The object is to devise methods by which a design can be investigated as a vibrating system, given that it is already kinematically suited to its task. The theoretical work is based on the assumption that only flexural vibrations are important, and uses the method of receptances to establish frequency equations which are then solved numerically to compare with the experimental results. The fundamental natural frequencies of the linkage were studied by free vibration tests and fundamental resonant response curves were obtained under conditions of forcing. The input was a mechanical scotch yoke drive when the links were flexible and an electro-magnetic exciter when the links were rigid. Comparison of experiment and theory shows extremely good agreement for natural frequencies over wide ranges of configuration and acceptable agreement for the forced response curves.
General Performance Indices for the time and Frequency Response for the Free Motion of Linear Discrete Control Systems
Authors: Soliman J. I. , Al-Shaikh A. 
Published: February 2007

A method for evaluating general performance indices for the time and frequency response for the free motion of a linear stationary discrete control system described by the matrix equation is given. A matrix B is formed from the system matrix A. The transpose of the inverse of the matrix B and its powers is then used to evaluate the expressions and where is a quadratic algebraic form, Δ m is the mth forward difference, and r = 0, 1, 2, …. From these expressions performance indices for the time and frequency response were then determined.
Buffeting Excitation of Boiler Tube Vibration
Authors: Owen P. R. 
Published: February 2007

The origin of the vibration generated within an extensive bank of tubes that run transverse to the direction of gas flow through a boiler shell and whose movement is small enough in amplitude to have no perceptible effect on the motion of the gas, is examined on the supposition that, sufficiently deep inside the bank, the flow is essentially turbulent and, except for a general drift through the bank, exhibits no regular feature. Conditions of this kind are thought to be appropriate to certain types of heat exchanger used in nuclear power stations and operating at large Reynolds numbers. The source of vibration, either structural or gaseous, is associated with the randomly fluctuating forces imposed on the tubes by the turbulent eddies, and a simple argument is put forward to account approximately for the length scale of the most energetic of these eddies and consequently the frequency with which they encounter the tubes. It is further argued that the tubes are aerodynamically discriminating in their force response which is thereby narrowed spectrally and confined to the neighbourhood of the frequency corresponding to the energetic eddies. The subsequent structural or acoustic response is even more sharpened spectrally, owing to the small damping inherent in the system. A relation between the dominant frequency of the force fluctuations, the gas velocity and the geometrical arrangement of the tubes, that emerges from the argument, agrees in form with published observations of the sound emission from boilers under resonant conditions. A disposable constant appearing in the relation is also satisfactorily predicted in order of magnitude. The analysis applies to only one possible form of the vibration phenomenon; other forms, aero-elastic and vortex-excited, may appear under suitable conditions dependent upon Reynolds number, structural stiffness and damping.
Machining Forces: Some Effects of Removing a Wavy Surface
Authors: Wallace P. W. , Andrew C. 
Published: February 2007

Previous work has shown that during the removal of a surface waveform oscillating cutting force components arise which may have a phase difference with respect to the oscillating component of undeformed chip thickness; it has also shown that the shear angle is affected by the slopes of the surface waveform. However, no attempt to predict the oscillating force behaviour from the geometry of cutting has been reported. The present work attempts to achieve such a prediction by means of an analysis of the phase and magnitude of the oscillating force components acting in two directions; in the directions of the mean shear plane and of the tool rake face. In the analysis it is assumed that the shear angle oscillates in phase with and proportionally to the surface slope, and that the curvature of the chip varies with the undeformed chip thickness. An experimental technique for cutting with variable undeformed chip thickness is described, together with a method for recording and measuring the oscillating components of force and undeformed chip thickness. Experimental results are presented which show the assumptions made in the analysis to be substantially valid; the predicted oscillating forces are shown to be in adequate agreement with experiment over a range of experimental conditions. It is shown that the oscillation of the shear angle is primarily dependent on the surface slope and that the frictional force behaviour is consistent with the characteristics of the two regions of friction, sticking and sliding, as found in work on cutting with constant undeformed chip thickness.
Design of Turbine Blades Suitable for Supersonic Relative Inlet Velocities and the Investigation of Their Performance in Cascades: Part II-Experiments, Results and Discussion
Authors: Colclough C. D. 
Published: February 2007

This paper describes cascade tests which were initially done to see whether blades designed by conventional methods for subsonic flows would in fact accept supersonic velocities at inlet to the blades but it was found that they would not do so. An analytical method for the design of turbine blades to accept supersonic relative inlet velocities has been presented in Part I (1). A blade section was designed for isentropic flow and from tests run on a cascade of these, values for losses and allowable contraction ratios were obtained which were incorporated in a revised design method. The tests and results obtained from the first supersonic cascade are described and also the results from the modified design which was based on non-isentropic conditions. The supersonic cascades were tested over a range of incidences in a small wind tunnel fitted with interchangeable liners to produce Mach numbers of approximately 1.5 and 1.3, Preliminary tests were also run at subsonic velocities. At design conditions flow-visualization by means of a Schlieren system showed wave formations in the blade passages which corresponded to the theoretical design values thus proving the validity of the design method. At off-design conditions a somewhat unusual shock-wave boundary-layer interaction was observed which appears to be associated with blades of this type. This was analysed by means of total head traverses, static pressure measurements and by the method of characteristics, and the effect which the configuration had on the downstream flow and losses is discussed. Total head traverses were done at the exits from the blade passages and also downstream of the trailing edges and the velocity coefficients were deduced from these values and from static pressure measurements obtained from wall tappings. For the first cascade which had a flow turning angle of 128° the velocity coefficient was approximately 0.95 and for the last cascade which had a turning angle some 9° greater, the value was 0.94. These velocity coefficients are higher than those for subsonic blades at comparative turning angles. With blades designed for supersonic flows by the method outlined in Part I (1) it appears to be possible to turn the flow through large angles such as 140° and to obtain acceptably high efficiencies. Tests in steam turbines indicate that with these blades the maximum efficiency is at least equal to that of a turbine designed for subsonic flow but that the heat drop is some 12 per cent higher.
Observations of the Effect of Creep Relaxation on High-Strain Fatigue
Authors: Edmunds H. G. , White D. J. 
Published: February 2007

Results are presented of high-strain endurance tests on 2‡ per cent chromium, 1 per cent molybdenum steel. As well as continuous cycling at room temperature and 600°C, the tests covered hold times of 30 minutes and 300 minutes at maximum strain at 600°C. For the shorter hold times, strain ranges extended down to less than ±0.1 per cent and for the longer hold times down to ±0.24 per cent. In a few tests an attempt was made to modify the test environment in order to gain an indication whether corrosion effects are likely to be important in such tests. It is argued that, for preliminary design purposes (pending the outcome of comprehensive endurance tests), extrapolation from high strains to low may be dangerous and that it may be preferable to use relatively simple creep data to gain an early indication of likely endurance properties with hold time. Such an interpretation is not inconsistent with the present or previously published data.
Experimental Investigation of the Behaviour beyond the Elastic Limit of Flush Nozzles in Cylindrical Pressure Vessels
Authors: Cottam W. J. , Gill S. S. 
Published: February 2007

Eleven tests have been carried out on mild steel cylindrical pressure vessels with flush nozzles. The cylindrical vessel was 18-in outside diameter x 3/8-in thick and the nozzles covered a range of outside diameters from 2 1/2 in to 6 in and thicknesses from 1/8 in to 3/8 in. The nozzle-vessel weld was in all cases to B.S. 1500, Fig. 32 e. Two plain cylindrical vessels 18-in o.d. x 3/8-in thick were also tested to establish datum curves for the vessels with nozzles. Clock gauges and strain gauges capable of measuring up to 2 per cent strain were used to measure the strain and change of geometry in the vicinity of the nozzle-cylinder intersection. Measurements were also made of the pumped water volume as the pressure was increased. After pressurizing until the main vessel had yielded the instrumentation was removed and all vessels were tested to rupture. The results do not show a well defined plastic limit pressure as normally understood but it has been possible to define from the experiments a series of pressures for each specimen at which consistent patterns of stress, strain and deflection are evident. One of these pressures is chosen to derive an empirical relationship which can be used in formulating a minimum design requirement.
‘Suitable Mean Values’ in One-Dimensional Gas Dynamics
Authors: Livesey J. L. , Hugh T. 
Published: February 2007

The problem of the definition of mean values of flow quantities for use in the application of one-dimensional gas dynamics to non-uniform flows is considered. Previously given methods for this problem are surveyed and are shown to be considerably in error and to have some unsatisfying basis of definition. A more satisfactory basis is suggested, based upon enthalpy flux, and this is shown to be more general and to have a satisfactory thermodynamic basis, particularly in the definition of mean temperature. The significance of the form of definition of mean total pressure in relation to the energy equivalent of the irreversibilities is stressed. ‘Availability or entropy flux’, ‘mass weighted’, ‘area weighted’, ‘mass derived’ and ‘momentum mixed’ definitions of mean total pressure are considered. Data for typical velocity profiles, over a wide range of Mach number, and for all known methods of calculating mean values have been obtained and a graphical summary is presented here. At first glance, the data would seem to indicate that the percentage error in calculating total pressure by the different definitions is small, but this is not so. To assess the errors introduced in estimating the irreversibilities of a length of duct by using mass derived or other definitions of mean total pressure, then the error should be estimated as a percentage of the relative differences of mean total pressure involved. The data list which the authors hope to publish separately and the graphs in this paper enable this to be achieved.