bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stress Distribution in a Wedge for Boundary Conditions Approximating to the Rake-Face Loads on a Metal Cutting Tool
Authors: Thomason P. F. 
Published: February 2007

An analysis of published experimental and theoretical slip-line field results for the metal cutting process suggests that, when the tool and workpiece are of high elastic modulus, a reasonable first approximation to the rake-face loading will consist of uniformly distributed normal and tangential stresses over the contact length. An indication of the form of the stress distribution at the tip of a cutting tool is therefore obtained from an isothermal–elastic solution for a two-dimensional infinite wedge, loaded antisymmetrically by uniform normal and tangential stresses adjacent to the apex. Only a preliminary assessment of the results is made, in relation to cutting tool wear and fracture problems, since a more detailed assessment will await a complete thermoelastic solution to the problem.
Cross Flows in Bounded Three-Dimensional Turbulent Boundary Layers
Authors: Horlock J. H. 
Published: February 2007

A study is made of the flow normal to the mainstream direction (cross flow) that takes place in three-dimensional ‘bounded’ turbulent boundary layers near a wall, i.e. boundary layers restricted by the presence of bounding surfaces normal to that wall. Such boundary layers are present in the flow through rows of blades in a turbo machine. Analytical expressions for the cross-flow velocity profiles are derived for these ‘bounded’ boundary layers and are compared with experimental data.
Transfer-Function Identification Using a Complex Curve-Fitting Technique
Authors: Mannetje J. J. 't 
Published: February 2007

The mathematical analysis and synthesis of linear-dynamic systems, based on experimental test results, often requires that the frequency response of the system be fitted by an algebraic expression. The form in which this expression is usually desired is that of a ratio of two frequency-dependent polynomials. In this paper, a method based upon the minimization of the weighted sum of the squares of the differences between the measured data and the approximating function is presented as a means for the evaluation of the polynomial coefficients of the approximating function. The computer programme used will be discussed and the modifications that improve the accuracy of the calculated coefficients, although the data points may be subject to measurement inaccuracies.
A Reference Stress Approach to Creep Bending of Straight Tubes
Authors: Fairbairn J. 
Published: February 2007

Reference-stress parameters, based on the Norton constitutive equation, are developed for creep bending of circular and elliptical tubes. The parameters are presented in the form of a design chart. The reference stress methods apply also to other simple constitutive equations of the power law, exponential and hyperbolic sine forms, and also to two complex equations describing creep behaviour over the entire range from primary to tertiary. In these equations the functions of stress and time are not separable and reference stress techniques provide a convenient method of evaluating stationary stress distributions and investigating the variation of these stresses with time. Aluminium alloy tubes were creep tested with cyclic uniform bending moments. Creep strains to fracture were measured by an end-rotation method. The creep behaviour of the tubes was well predicted by reference-stress cyclic tensile creep tests.
Separation Cavitation in Lightly Loaded Fluid Film Bearings with Both Surfaces in Motion
Authors: Taylor C. M. 
Published: February 2007

For lightly loaded fluid film bearings in which gaseous cavitation occurs, application of the continuity boundary condition at the liquid-gas interface is not satisfactory. Two alternative boundary conditions have been postulated. The purpose of this paper is to examine the separation boundary condition; in particular, the effect of both bounding surfaces being in motion is studied. This situation might be used as a basis for experimental work designed to select the most appropriate boundary condition for lightly loaded bearings. In Part 2, the boundary condition is used to analyse the cylinder-plane and journal bearing configurations. The theoretical predictions for the operating parameters are examined to see if their magnitudes and/or trends could be used for comparing the available cavitation boundary conditions.
Fluctuating Lift Coefficient for a Circular Cylinder in Cross Flows
Authors: Kacker S. C. , Pennington B. , Hill R. S. 
Published: February 2007

Fluctuating lift forces experienced by cylinders of diameters 1, 1.125, 2, 3 and 4 in, and length-to-diameter ratios ( l/d) of 0.25 to 9 have been measured for Reynolds numbers in the range Re = 104to 2.5 times 105. Fluctuating lift and drag coefficients for the limiting case of l/d ŕ 0 were obtained by integrating measured values of the fluctuating surface pressure at points distributed around a horizontal section of the tube. At lower Reynolds numbers, lift coefficients for cylinders having l/d < 1 were found to agree within the limits of experimental accuracy with the values obtained by surface pressure measurements. However, at the Reynolds number of 105, the lift coefficient for cylinders of l/d = 0 were much higher than the lift coefficients for cylinders of l/d = 1; this clearly demonstrates the incoherence of the flow at Re = 105. A measure of the extent to which vortex shedding is in phase along the length of a tube is obtained as a length scale for the coherence of vortex shedding. This was inferred from the variation of the measured value of the lift coefficient as a function of l/d. Within this length scale there is a high degree of correlation between signals from two points. Direct measurement of the length scale obtained by measuring u' correlations gave a value of the same order of magnitude but some 50 per cent lower than the length scale obtained from the measurements of the lift coefficient.
An Investigation of Laminar Flow in the Rotor Windings of Directly-Cooled Electrical Machines
Authors: Woods J. L. , Morris W. D. 
Published: February 2007

A theoretical and experimental investigation aimed at gaining an insight into the effect of rotation on flow and heat transfer in the cooling channels of rotors for electrical machines. Specifically, the flow geometry considered is that of a circular tube constrained to rotate about an axis parallel to its axis of symmetry, this being the main component in the coolant circuit for the internal cooling of rotor windings. The theoretical work treats the case of laminar flow well removed from entrance effects. The governing conservation equations were solved numerically and solutions are presented for the velocity and temperature fields when the tube wall is uniformly heated. Subsequently, the influence of rotation on heat transfer and flow resistance was derived from these solutions. Comparison of the theoretical prediction with experimental data obtained with air and water demonstrated that the theoretical model is, in general, capable of predicting the effect of rotation.
The Anisotropic Yield, Flow and Creep Behaviour of Pre-Strained En24 Steel
Authors: Shahabi S. N. , Shelton A. 
Published: February 2007

Tests under combinations of tension, torsion and internal pressure have been performed at constant stress ratio on En24 steel, previously annealed, and then subjected to a pre-stress in either axial or circumferential tension or torsion. Post-yield behaviour showed marked room-temperature creep by all strain components in the logarithmic form ε = a In t + c. The initial direction of the incremental plastic strain-ratio vector was markedly different from isotropic behaviour and remained constant in direction with time. Increased loading resulted in a progressive rotation towards the isotropic direction. Anisotropic yield loci were established from the normality rule and from the backward extrapolation of curves of creep coefficient versus stress and stress versus ‘long-time’ strain. The yield locus was translated to the pre-stress point and this local work-hardening was accompanied by softening in both the transverse and reverse directions, i.e. the cross-effect and Bauschinger effect respectively. Yield loci in planes not containing the pre-stress axis showed softening in all directions and under axial tension-internal pressure the cross-effect caused a rotation of the locus. All yield loci were smooth and continuous. Yield criteria derived from the theories of Edelman and Drucker and also Williams and Svensson were in good agreement with experiment over the whole locus. Hill's theory was thought to be more appropriate to material behaviour following large deformations.
Condensation on Rotating Axisymmetric Curved Bodies
Authors: Osei-Bonsu M. A. , Holgate M. J. 
Published: February 2007

Laminar film condensation on an axisymmetric generally curved rotating body is analysed. With the body rotating about a vertical axis, the condensate film drains under the combined action of gravitational and rotational accelerations. An exact integral equation is found for film thickness in terms of body shape, fluid properties, and rotational parameters. This shows the effect of curvature to be important. The theory was tested by experiments with steam condensing on a concave body generated by a 90° circular arc. Comparison of experimental results with predictions from the general theory developed are generally good, especially at high rotational speeds. It is shown that the inclusion of the effect of curvature produces a markedly better prediction than that from an analysis treating the body as a succession of truncated conical elements.
Thermal Stability of Models of Rough Elastohydrodynamic Systems
Authors: Dyson A. 
Published: February 2007

Asperity interactions in the inlet zone of an elastohydrodynamic system may increase the local temperatures in that zone and cause a significant decrease in the minimum thickness of the lubricant film. Theoretical studies of various model systems, in which the direct effect of the roughness of the surfaces on the hydrodynamics has been ignored, show that the systems remain thermally stable under the most realistic assumptions made in the various models. It is therefore unlikely that the mechanism studied is that of scuffing.
Strain/Time Relations Describing Creep
Authors: McCartney L. N. , McLean D. 
Published: February 2007

A new equation describing recovery creep is , where ε is the strain and is the eventual steady creep rate. From one form of the equation, namely , the McVetty-Garofalo, two forms of logarithmic, and Andrade creep equations are obtained with n = 1,2, and 5/2 respectively. From another form, namely , Li's, Akulov's and McLean's equations are obtained. These and other equations which are obtained are thus systematically related to each other. The physical bases of several derivations are also shown to be similarly related. During the deceleration from the initial creep rate to the final rate , there develops not only a balance between the rate of recovery, r, and the strain hardening coefficient, h, so that , but also a decrease in r and an increase in h which prolongs primary creep. This paper shows how to take into account the changes in r and h, and that equations which do so, whether implicitly or explicitly, describe experimental creep strain/time curves quite well. It is thus shown that behind the present bewildering profusion of apparently unrelated equations and physical models describing creep there is a simpler situation, in which the creep equations can be systematically derived in a physically significant manner from a single expression for recovery creep. The simplification achieved is expected to have a pedagogical and a practical value for engineers and metallurgists interested in creep.
A Re-Examination of the Proneness to Derailment of a Railway Wheel-Set
Authors: Gilchrist A. O. , Brickle B. V. 
Published: February 2007

The circumstances giving rise to the incipient derailment of a railway wheel-set under steady-state rolling conditions are re-examined in the light of recent developments in rolling-contact theory. It is found that the problem can be stated in a form which avoids difficulties inherent in most earlier treatments. However, a quantitative solution requires data relating tangential force to creepage and spin in a parameter region previously unexplored. New experimental results are presented which partially correct this lack of data, but more work, both theoretical and experimental, is required. One outcome of the new study is the establishment of the region of applicability of Nadal's classical formula. It shows it to be highly relevant for practical decision-making.
Prediction of Recirculating, Swirling, Turbulent Flow in Rotating Disc Systems
Authors: Gosman A. D. , Lockwood F. C. , Loughhead J. N. 
Published: February 2007

Predictions were made of the swirling, recirculating, turbulent flow between a rotating and a stationary shrouded disc with an axial source flow. A two-dimensional finite-difference procedure was used. Turbulent transport processes were calculated with the aid of a turbulence model involving the solution of two differential equations. Comparison of predicted disc torque with experimental data showed good agreement. Details of the predicted flow between the discs are presented and shown to be plausible; they also highlight the need for detailed hydrodynamic measurements in these types of flows to aid more rigorous testing of the method.
Dynamics of Timoshenko Beams Conveying Fluid
Authors: Paidoussis M. P. , Laithier B. E. 
Published: February 2007

The dynamics of pipes conveying fluid is described by means of the Timoshenko beam theory. The equations of motion are derived and solved ( a) by a finite-difference technique, and ( b) by a variational method. It is shown that the latter is the more efficient method. The eigenfrequencies of the system and its stability characteristics are compared with results obtained previously using the Euler-Bernoulli beam theory, and it is shown that in certain cases (e.g. short pipes) the two sets of results diverge. Experiments indicate that the present theory is more successful in predicting the observed behaviour. Furthermore, the present theory shows that, in some cases, cantilevered pipes may lose stability by buckling, whereas previous theories indicate that the system always loses stability by flutter.
Pressurized Member with Elliptic Median Line: Effect of Radial Thickness Function
Authors: Holland M. 
Published: February 2007

Radial thickness function is represented by the first two terms of an even Fourier series and the unknown coefficient in the function is determined from the constraint: ‘maximum amplitude of stress in the member must be restricted to the minimum value possible’. Using this technique, it is shown that for two members having a ratio of principal axes equal to 2.0, being of equal weight and subjected to the same maximum stress level, the member with varying radial thickness will withstand an applied pressure which is just over forty per cent higher than that carried by the traditional constant-thickness member. Alternatively, for equality in pressure loading and maximum stress level, the ratio of weights for the two members is 0.844, in favour of the variable-thickness member.
Experimental Study of Normal and Shear Characteristics of Machined Surfaces in Contact
Authors: Burdekin M. , Back N. , Cowley A. 
Published: February 2007

The paper is concerned with the experimental investigation of the normal and shear stiffness characteristics of joint interfaces formed from cast-iron surfaces which are subjected to a combination of normal and shear forces. Because of the relatively small deflections, an experimental procedure is adopted which enables a number of interfaces to be considered in series, thereby increasing the resolution of a single measurement and averaging out small topological differences between nominally identical surfaces. The range of parameters investigated covers those which are used in current design practice. The combination of machined surfaces include ground on ground and hand-scraped on ground. These surfaces were subjected to normal pressures up to 9 times 106 Nm-2 and the resulting characteristics are represented in graphical form.
The Effect of Cold-Drawing on the Yield and Flow Behaviour of OFHC Copper under Combined Stress
Authors: Holloway G. , Shelton A. 
Published: February 2007

Tests under combinations of tension, torsion and internal pressure have been performed at constant stress ratio on oxygen-free high-conductivity (OFHC) copper, previously annealed and then subjected to progressive reductions in the plug-drawing process. The influence of cold-drawing was investigated by means of six reductions in area up to 81 per cent and this showed marked changes in the creep behaviour. Logarithmic creep no longer occurred and, in contrast to the annealed material, creep was observed at stresses well below yield when the latter is defined by the backward extrapolation method. The creep rate accelerated rapidly as the yield stress was approached and the creep strain became large compared with the instantaneous strain. Under axial tension—internal pressure, symmetrical yield loci tending progressively towards the Tresca criterion were found for reductions up to 42.4 per cent. Asymmetry developed at the largest reduction and, in general, the normality rule was obeyed in subsequent plastic strain behaviour for all tests. Under axial tension—torsion and internal pressure—torsion, almost identical elliptical yield loci were found for each reduction. These also tended towards the Tresca criterion for reductions up to 42.4 per cent and distortion was only observed at the largest reduction. Again, the normality rule was obeyed. Yield criteria derived from the theory of Edelman and Drucker were in good agreement with experiment over all yield loci. Hill's theory showed good agreement with experiment under tension—torsion, except for the largest reduction, but was inadequate for those axial tension—internal pressure tests not in agreement with the Maxwell–Mises yield criterion.
Design of an Anthropomorphic Manipulator for Industrial Application
Authors: Vukobratović M. , Hristić D. 
Published: February 2007

This paper presents a two-level manipulation concept, featuring minimal configuration for attaining the working point in the working space without obstacles, and the compensating part in the form of a gripper, by means of which the problem of the corresponding orientation is fully solved. An industrial manipulator based on this concept is realized and the results of experimental trials using a microprocessor controller are given.
Drop Coagulation in Cross-Over Pipe Flows of Wet Steam
Authors: Williams J. J. E. , Crane R. I. 
Published: February 2007

A numerical technique is developed for predicting the evolution of drop-size spectra in turbulent, two-phase pipe flows. While relevant to many chemical engineering processes, it is applied here to the crossover pipes of a nuclear wet-steam turbine. Valid expressions for turbulent coagulation rate in the cross-over pipes are available only for drops below about 10 μm diameter in the core flow, and for those exceeding about 20 μm near the pipe wall. Using these expressions, it is found that the rapid formation of large drops in the core allows prediction for only a small fraction of the typical residence time in the pipe, but near the wall the volume median diameter of an initial 20 μm monodispersion can double in 100 ms. Further work is required to validate the technique and extend it to handle the intervening ranges of drop size and turbulence parameters.
Effects of Cathode-Mandrel Surface Irregularities on the Mechanical Properties and Structure of Electroformed Iron Foil
Authors: Crichton W. A. , McGeough J. A. , Thomson J. R. 
Published: February 2007

Iron foil, of thicknesses between 003 and 0.15 mm has been electroformed at a current density of 30 A/dm2 and an electrolyte temperature of 100°C upon cathodes of surface roughness ranging from 0.04 to 4.4 μm Ra. The surface roughnesses of the face of the foil formed adjacent to the cathode, and of that electrode, are similar. The roughness of the reverse anodic face increases with increasing foil thickness, due to the increase in size of the crystal growth sites. The hardness of the cathodic face of the foil is unaffected by either cathode surface roughness or foil thickness. The hardness of the anodic face increases with both increasing cathode surface roughness and decreasing foil thickness, due to corresponding changes in grain size. A slight net decrease in tensile properties with increasing cathode surface roughness is attributed to the greater amount of stress concentration borne by the rougher foils. Young's modulus for the foil is not affected by cathode surface roughness. The electroforming of foil upon a mandrel surface carrying an isolated V-shaped scratch, 0.14 mm deep and 0.28 mm wide, has also been studied by numerical and experimental methods. The cathodic surface of foil is found to adopt the shape of the scratch whilst its upper side becomes level. The effect upon the geometric configuration of the foil depends upon the relationship between current efficiency and current density for the electrolyte, and on the polarisation (overpotential) characteristics at the mandrel surface.
Natural Transition of Boundary Layers—The Effects of Turbulence, Pressure Gradient, and Flow History
Authors: Abu-Ghannam B. J. , Shaw R. 
Published: February 2007

Natural transition of boundary layers is investigated for a flat plate in a low-speed wind tunnel with free-stream turbulence intensities ranging from 0.3 to 5 per cent, and with pressure-gradient histories typical of turbomachinery blades without separation. Empirical relationships are proposed for the prediction of the start and end of transition, as well as the development of the boundary layer during transition. These relations are based on the recent measurements made with a hot-wire anemometer, and augmented, mainly for the start of transition, by results of previously reported research. Finally, these experimental relationships are used in conjunction with well established methods to predict the entire unseparated boundary layer. To utilize the prediction, all that is required is a knowledge of the free-stream turbulence level and the free-stream velocity distribution, which itself can be derived from potential flow theory.
Some Implications of Dundurs' Theorem for Thermoelastic Contact and Crack Problems
Authors: Barber J. R. 
Published: February 2007

It is well known that a simply-connected isotropic elastic body in a state of plane strain and with traction-free boundaries remains free of stress if it is subject to steady-state heat conduction. A recent theorem due to Dundurs shows that in this state the curvature of any initially straight line element is proportional to the heat flux across the line element. A closely related three dimensional result is proved for the sum of the principal curvatures of planes parallel to the faces of an infinite thick plate. These results have certain implications for thermoelastic crack and contact problems. For example: (i) thermal distortion has no effect on the contact pressure distribution at an insulated interface or at an interface between two similar materials, (ii) the thermal stress in a cracked solid depends on the temperature field only through the value of a certain constant related to the average temperature difference across the crack, (iii) steady-state heat flow induces no stresses in an axisymmetric thick plate containing an external crack.