bluuebunny/crossref_metadata_2025 huggingface dataset:
A Review of the Interaction of Creep and Fatigue
Authors: Ellison E. G.
Published: February 2007

Many components in supersonic aircraft and modern power plant operate under cyclic conditions at increased temperatures at which creep processes also occur. Solving associated material problems depends, to a major extent, on understanding the various factors influencing behaviour, such as the effect of stress or strain cycling, dwell periods, temperature, notches, environment, multiaxial stress, ductility, and the effect of prior testing on subsequent endurance. The various methods of testing are briefly described and the mode of failure where there is interaction between creep and fatigue is discussed. Methods for predicting deformation and life are also presented. Finally, the review concludes with suggestions for future work.
Fracture in Spherical Pressure Vessels
Authors: Burdekin F. M. , Taylor T. E.
Published: February 2007

The problem of fracture initiation and propagation from long flaws in spherical pressure vessels is considered from both theoretical and experimental viewpoints. Experimental work has been carried out on vessels of 5 ft diameter and 1/2 in thickness with a range of initial slit lengths from 3-24 in to determine the pressure for rupture by shear fracture. Geometrical variations were further examined by tests on two vessels of 26 in diameter and 1/2 in and 1/4 in thick respectively. The vessel tests were instrumented to give detailed behaviour local to the crack tip and to indicate the gross deformations occurring. The results have been analysed and found consistent with the theoretical view that fracture in vessels of ductile materials may be controlled by the occurrence of a limit mechanism. For less ductile materials it is suggested that fracture mechanics approaches should be used, with allowances for plasticity and bulging. The approach enables the prediction of critical crack lengths for unstable fracture in full size service vessels provided the relevant material properties are known.
Hydrodynamic Lubrication of Soft Solids
Authors: Bennett A. , Higginson G. R.
Published: February 2007

A simple pure-sliding experiment, on a cylinder and plane apparatus, is used to examine the benefit to be gained from the use of a thin soft layer on the surface of one of a pair of mating solids. In terms of lubrication and friction, the benefit is considerable.
Rolling Contact Lubrication Using a Maxwell Fluid
Authors: Mitchell D.
Published: February 2007

Pressure distribution curves are obtained for rolling cylinders lubricated by a Maxwell fluid, using a digital computer. Solutions are obtained for a ‘solid-like’ (vorticity neglected) fluid and for a fluid when vorticity is not neglected and these are compared with the Newtonian pressure distribution. A recently proposed upstream boundary condition is used throughout.
Limit Pressures for Cylindrical Shells with Unreinforced Openings of Various Shapes
Authors: Kitching R. , Davis J. K. , Gill S. S.
Published: February 2007

Experimental limit pressures have been determined and compared for cylindrical shells with unreinforced openings of 26 different shapes and sizes. Deformation patterns were also studied.

The shapes included circles (radius r = c), squares (side 2 c), rectangles (longitudinal side 2 c, circumferential side 2 a) and ellipses (longitudinal and circumferential semi-axes c and a respectively).

Specimens of the different shapes but where dimension c was common were found to behave similarly and to have closely related limit pressures. This was predicted for specimens having rectangular and square openings by a lower bound analysis which led to a simple mathematical relationship between limit pressure and the non-dimensional parameter c/√RT, R and T being respectively the radius and thickness of the cylinder.

The results are important in predicting limit pressures for cylinders having openings of shapes corresponding to curves formed by the intersection of the shell by oblique branches.
Measurements of End Thrust on a Model Poppet Exhaust Valve
Authors: Annand W. J. D. , Lanary R. S.
Published: February 2007

End thrust measurements have been made under steady flow conditions on a model poppet exhaust valve supported on air bearings in a straight ‘port’ coaxial with a ‘cylinder’. The tests covered pressure ratios across the valve up to 1·75. They show that the end thrust is approximately equal to the product of the pressure drop and the exposed head area, for lifts up to about 0·15 diameters, and diminishes progressively with increase of lift beyond that value.
Effect of Pressure on the Calibration Characteristics of Hot Film Anemometers
Authors: Al'Omar A. F. , Bakhtar F.
Published: February 2007

It is shown that the heat lost from the sensing element of a hot film anemometer under the condition of no imposed flow is affected by the pressure when the fluid is compressible. A method is proposed for plotting the calibration results in order to make the resulting chart applicable over a wide range of pressures.
Experiments in Plate Cutting by Shaped High Explosive Charges
Authors: Zaid A. I. O. , Hawkyard J. B. , Johnson W.
Published: February 2007

Although axisymmetrical lined cavity shaped charges have received considerable development and analytical treatment in the past, mainly in connection with armour piercing projectiles, relatively little attention appears to have been directed towards the linear system. This finds limited application in the cutting of plates, sections and pipes, in demolition and emergency rescue work for example.

Experiments into the linear cutting system are described in this paper, to investigate the influence of liner and charge geometry. Steel plates up to 2 in thickness are cut, using charge weights up to 50 g per inch of cut. To investigate the theories available for the development of the very high velocity cutting jet and its penetration of the target, experiments are performed on a range of liner and target materials to achieve variations in density and yield strength.
Evaluation of Reference Parameters for Structures Subject to Creep
Authors: Sim R. G.
Published: February 2007

A convenient means of obtaining the reference stress parameters for a structure is given which uses arbitrary dimensionless solutions of the structure's creep behaviour. This is done by developing a simple expression which uses the dimensionless stationary state deformation rates to define the reference stress. To derive the reference stress parameters for the structure only the stationary state solutions for two different values of the stress index are required.
Effect of Axial Velocity Variation in Aerofoil Cascades
Authors: Soundranayagam S.
Published: February 2007

The effect of the variation of axial velocity in the incompressible flow through a cascade of aerofoils is discussed and it is shown that changes take place in the flow angles and in the blade circulation. A method is proposed by which the effect of axial velocity variation on a known two-dimensional flow or alternatively the two-dimensional equivalent of a flow with axial velocity variation can be calculated. The method is very easy to apply. The deviation may increase or decrease depending on the change in blade circulation and the stagger. An increase in apparent deflection through the cascade can be accompanied by a reduction in the blade force. The method would be particularly useful for the interpretation of cascade wind tunnel data and in the design of impeller stages where three-dimensional flows occur.
Synthesis of Crank-Links
Authors: Edwards G. , Webster J. J.
Published: February 2007

Solution procedures, which form part of the synthesis of four-bar linkage coupler point path generators, are shown to be applicable to the simpler problem of synthesizing crank-links with prescribed relationships between the rotation of the crank and the position of the free end of the link.
Estimation of the Fatigue Life of a Thick-Walled Cylinder Subjected to Repeated Internal Pressure
Authors: Haslam G. H.
Published: February 2007

Experimental data available on fatigue crack growth may be described by an equation of the form d a/d N = B(Δ K) m, where d a/d N is the rate of crack growth per stress cycle, Δ K is the range of stress intensity factor, and B and m are material properties.

This relationship has been used to estimate the fatigue crack propagation lives of thick-walled cylinders subjected to repeated internal pressure. By using an approximate value for the stress intensity factor, and considering the high local stresses at the crack due to pressurized oil, close correlation is obtained between the estimated and experimental fatigue lives.

Design curves are obtained, by which the fatigue life of such a cylinder may be estimated from a knowledge of the transverse uniaxial fatigue limit and fracture toughness properties of the cylinder material, as well as the diameter ratio of the cylinder and the repeated pressure.
Pitch Information from Single Flank Tests
Authors: Sharpe J. E. , Smith J. D.
Published: February 2007

Techniques for sampling single flank test results on grating equipment are discussed. The methods of analysis of the resultant pitch errors to separate out the errors of the two gears are given with a suitable computer programme. Master gear pitch errors can be eliminated by this approach, both for single and dual flank checkers.

The theoretical and practical problems of extending the method to complete car gearboxes with two meshes are discussed and suitable solutions given.
Streamline Curvature Analysis of Compressible and High Mach Number Cascade Flows
Authors: Bindon J. P. , Carmichael A. D.
Published: February 2007

A blade to blade design tool for analysing the subsonic, transonic and supersonic flows in axial turbine blades is presented using the streamline curvature method. The work includes a numerical convergence analysis which produced convergence of the digital computer programme for all cases attempted. Computed results are compared with experiment and other theory. Comparisons for turbine type cascades up to Mach 10 show a satisfactory agreement and techniques introduced give improved leading edge results and allow the Kutta–Joukowski condition to be applied at the trailing edge for the accurate determination of the velocity distribution and the cascade deviation. Predictions for convergent-divergent supersonic wind tunnel type nozzles agree closely with experiment and with other theories. Numerical difficulties are found to be more acute for subsonic/supersonic turbine cascades and experimental agreement, while acceptable, is inferior to that obtained for subsonic cascades.
Synthesis of Single-Ratio and Multi-Ratio Epicyclic Gear Trains
Authors: Fitzgeorge D.
Published: February 2007

A class of epicyclic gears based on coaxially mounted plane trains is defined. The class is restricted to those gears in which planetary gears of adjacent trains are coupled.

The type of epicyclic multi-ratio gearbox in which the input and output members are always the same is selected for consideration. The basic kinematics of the planetary member are then reduced to a single equation which is subsequently expressed as a chart, covering all ratio possibilities and directly applicable as the basis of synthesis. The chart is shown to offer an arbitrary means of describing the various forms of gear by a number-and-letter code.

The application of the chart to the synthesis of trains incorporating planetary idlers and multi-ratio trains is explained.
Harmonic Displacement Excitation at a Support
Authors: Bishop R. E. D.
Published: February 2007

The various uses to which receptances may be put in linear vibration theory are well known. For some purposes it would be useful to have the direct receptance at a co-ordinate expressed in terms of parameters of that modified system which is defined when the co-ordinate concerned is locked. The problem has been solved elsewhere (1) in general terms, for an undamped system with n degrees of freedom. The particular case of a simply supported beam is examined here, both for lumped and for continuously distributed parameters.
Determination of Orifice Characteristics of Spool Type Control Valves
Authors: Montgomery J.
Published: February 2007

A method of obtaining the flow characteristics of spool type control valves is outlined.
Slip-Line Field Analysis for Orthogonal Machining Based upon Experimental Flow Fields
Authors: Roth R. N. , Oxley P. L. B.
Published: February 2007

An experimental flow field for slow speed (0·5 in/min) orthogonal (plane strain) machining was analysed using slip-line field techniques. Although the experimental streamlines were not sufficiently accurate to determine a slip-line field directly by calculating the directions of maximum shear strain rate from the velocity gradients, they were found to give sufficient information together with the measured cutting forces for an approximate step-by-step method of constructing a slip-line field. In this way a slip-line field was constructed not only for the plastic zone in which the chip is formed but also for the plastic flow along the tool-chip interface. It is shown that for most of the flow the slip-line field is satisfactory for both stress and velocity.

An interesting feature of the analysis is that at the start of plastic deformation where the work material enters the plastic zone in which the chip is formed the increase in flow stress caused by strain-hardening is appreciable and must be taken into account in analysing the stresses, that is, in the stress equilibrium equations. However, along the tool-chip interface where the material has been severely strained there is little strain hardening and the slip lines in this region are shown to be consistent with the Hencky stress equilibrium equations for a material of constant flow stress.
Fracture of Triangular Plates Due to Contact Explosive Pressure
Authors: Al-Hassani S. T. S. , Johnson W. , Nasim M.
Published: February 2007

Triangular plaster of Paris plates were subjected to contact explosives and photographs of the fracture patterns obtained are presented. The effect of the geometry and the form of loading on the fracture patterns and the length of the spalls are discussed. A simple analysis which employs cylindrical stress wave equations shows that, as a pulse propagates towards the apex, a compressive head and a tensile tail are developed, both becoming larger in magnitude as the pulse approaches the apex. Fracture is produced whenever the tensile stress reaches a magnitude just above the ultimate tensile stress of the plaster; further fractures are also predicted by the analysis. The method of images is used to explain the presence of the longitudinal crack.
A Variational Solution of the 120-Degree Partial Journal Bearing
Authors: Safar Miss Zeinab S. , Szeri A. Z.
Published: February 2007

Reynolds equation reduced to ordinary differential equations by separation of variables. Two resulting equations integrated directly. Third equation and boundary conditions interpreted and solved as an isoperimetric problem.
A Theoretical and Experimental Investigation of a Gas Dynamic Model for a Single Stage Reciprocating Compressor with Intake and Delivery Pipe Systems
Authors: Benson R. S. , Üçer A. Ş.
Published: February 2007

A method is described for simulating a single stage reciprocating compressor. A model is developed which allows for wave action in the intake and delivery systems, and drag and inertia of the valves. It is shown that homentropic theory may be used for the wave action, provided a correction is made for the entropy changes across the valve. The results are given of an experimental investigation in which the pressures in the intake and delivery systems, the cylinder pressures, the mass flow and the valve movement were compared with the predictions using the model. Good agreement was obtained over the wide range of test conditions.
Lubrication of a Two-Layer Porous Journal Bearing
Authors: Cusano C.
Published: February 2007

An analytical solution for the performance characteristics of a two-layer porous bearing, using the short-bearing approximation, is obtained. Results are presented which relate the eccentricity ratio and coefficient of friction as functions of load number for design variables of 0·0001, 0·001, 0·01, and 0·1 and for a ratio of the permeability of the outer layer to the inner layer of 20. A comparison is made between the performance of two-layer and conventional porous bearings.
Characteristics of Inversion Tubes under Axial Loading
Authors: Al-Hassani S. T. S. , Johnson W. , Lowe W. T.
Published: February 2007

A thin wall tube, when axially compressed over a radiused die, either inverts, or buckles or tears. The phenomena associated with the external or internal inversion of tubes of aluminium, copper, mild steel and brass are described and load-tube shortening curves are presented for speeds of compression between 0·05 in/min and 20 in/min; some results for high speed compression using a drop hammer are also described.

Thickness changes during inversion are reported and experiments to establish the effect of die angle and die radius on the inversion load are given.

For the inside-out inversion of tube, a simple theoretical analysis to predict the steady inverting load and the optimum die radius for a strain hardening material is given, the basic assumption being that no change in the wall thickness takes place.
Numerical Solutions of Flow between Rotating Cylinders
Authors: Launder B. E. , Ying W. M.
Published: February 2007

The paper presents solutions of the laminar flow of a Newtonian fluid between cylinders with non-coincident axes, where the core cylinder rotates about its axis. The solutions have been obtained by means of an adapted version of the finite-difference procedure of Gosman et al. (1).

The results show that the inclusion of convective transport terms (which in previous analyses have been neglected or included only approximately) may have an appreciable effect upon the flow field and, in particular, upon the pressure field around cylinders.
An Explanation of Size Effect in Fatigue of Metals
Authors: Findley W. N.
Published: February 2007

Explanation is based on assumption that cyclic slip in the group of neighbouring crystals involved is initiated when the shear stress on the entire active plane reaches a critical value.
Paper 12. A Brief Description of the Hya Large Amplitude Pmm System
Authors: Chislett M. S. , Smitt L. Wagner
Published: February 2007

This paper gives a brief description of the HyA large amplitude horizontal Planar Motion Mechanism system. The mechanical layout and force measurement arrangements are described, and motion generation capabilities are specified.
Paper 16. Measurement of Steering Derivatives on Full-Scale Ship Trials
Authors: Lewison G. R. G.
Published: February 2007

The track of a ship executing manoeuvres may be recorded relative to a floating buoy and analysed to give speed and drift velocity. A new oscillating turn manoeuvre is described. The results of this, together with turning circles and pull-outs, may be used to calculate six linear and two non-linear derivatives in the equations of sway and yaw. A numerical example is given, based upon full-scale trials on a small vessel.
Paper 26. Stability and Control in Waves: A Survey of the Problem
Authors: Conolly J. E.
Published: February 2007

Manoeuvrability in waves is discussed from the point of view of the dangers of broaching-to when a ship is running before the sea. Conditions are assessed under which this may occur, illustrated by documented cases, including the Wahine disaster in 1968. Because of the problems involved in investigating broaching-to by means of free-running model tests, there is an urgent need for reliable mathematical models: however, theories published so far, based on two different simplifications, are shown to have limitations. It is argued that the theory must take account of pitching, surging, rolling and orbital motion of the water particles.
Flow through Moving Cascades of Lifting Lines with Fluctuating Lift
Authors: Hawthorne W. R.
Published: February 2007

The use of generalized functions to analyse the potential, two-dimensional, incompressible flow past singularities representing stationary and moving lifting lines is explained and developed. It is shown that the time mean stagnation pressure change in the flow through a moving cascade with fluctuating lift is normally zero, except when the lift fluctuations are in phase with the motion, so that a stationary system of shed vortices is produced in the downstream flow (the stationary, phased, fluctuating lift case). Then the time mean stagnation pressure is a function of position in the absolute co-ordinate system.

Expressions are obtained for the kinetic energy produced by the vortices shed off a row of blades with fluctuating lift. Idealized losses or drags due to these effects may amount to ½ or 1 per cent of the work or lift effects produced by the cascade.
Improved Convective Heat Transfer in a Fluid with Artificially Modified Turbulence
Authors: Boothroyd R. G. , Haque H.
Published: February 2007

Although a flowing gas loaded with fine particles can give a considerably higher wall heat transfer coefficient compared with the flow of gas alone, earlier studies have shown that this improvement is less than might be realized due to dampening of turbulence near the heat transfer surface by the particles. This paper reports an investigation into off-setting the effect by adding fine fibres to a suspension of 5–40 μm particles in air flowing in tubes of 1, 2 and 3 in diameter. The results indicate that in most situations a fibre-particle suspension is likely to be superior as a coolant compared with a suspension of particles flowing alone.

The purpose of the fibres is (1) to induce a large-scale vortex motion near the pipe wall where normal turbulent fluid mixing is inadequate; (2) to promote controlled residence time of wall-contact of particles of high thermal conductivity and high thermal capacity and (3) to keep heat transfer surfaces clean with the minimum erosion effect.
Deflection Equation for the Buckling of an Elastic Column Subjected to Surface Pressure
Authors: Newland D. E.
Published: February 2007

The deflection equation for the buckling of an initially straight elastic column subjected to external or internal pressure is derived for the case when the pressure and the area of the column may vary along its length. Apparently this equation has not been reported in the literature previously.
Non-Steady Characteristics of a Pneumatic Servo-Valve
Authors: Dent G. , Reynolds A. J.
Published: February 2007

Measurements of the instantaneous flow rates through a pneumatic servo-valve are presented for valve opening frequencies between 0 and 10 Hz. While the correlation of the results is broadly consistent with the hypothesis that the internal flow pattern is independent of frequency, there is some evidence that switching between alternative patterns may occur at some frequencies.
Analysis of Hydrodynamic Journal Bearing with Axes Skew
Authors: Singh D. V. , Sinhasan R. , Singh H. N.
Published: February 2007

A solution of Reynolds equation for journal bearing with axes skew has been proposed which is valid for any extent of positive film. Pressure distribution, Sommerfeld number, and friction coefficient parameter have been obtained for some arbitrarily chosen skew values.
Transmission of a Continuous Square Wave down a Pneumatic Line
Authors: Tyack Susan C. , Hughes T.
Published: February 2007

Using the electrical analogy, a solution for the transmission of a continuous square wave down a pneumatic line has been obtained. The results are compared with experiment and show good agreement.

Using the theoretical results, it is possible to calculate the maximum separation between pneumatic (fluidic) devices that will still ensure satisfactory operation. Typically, it can be shown that at a frequency of 100 Hz, the output from a fluidic OR gate or bistable (see Appendix 1) may be transmitted 8 m and the amplitude of the signal will still be large enough at that point to switch a second OR gate or bistable.
Absolute Viscosity of Air down to Cryogenic Temperatures and up to High Pressures
Authors: Latto B. , Saunders M. W.
Published: February 2007

The absolute viscosity of gaseous air was determined experimentally for the general pressure and temperature range 100–15 000 kPa and 90–400 K respectively, using a series capillary transpiration-type viscometer which has been developed by the authors. The accuracy of the experimental data is believed to be better than ± 1 per cent.

Two general correlating equations, one for atmospheric pressure and the other for medium high pressure (i.e., densities up to 400 kg/m3), have been obtained.
Design and Performance of a Coulomb Shock Isolator
Authors: Caton A. T. , Holmes R.
Published: February 2007

A convenient way of presenting optimum isolator designs and their performance is demonstrated using trade-off diagrams. An isolator embodying a coulomb-friction element and a return spring is described together with test results. These results are compared with theoretical predictions and are found to be satisfactory for design purposes.
Large Deflections of Rectangular Orthotropic Plates under Combined Transverse and In-Plane Loads
Authors: Prabhakara M. K. , Chia C. Y.
Published: February 2007

A theoretical analysis is presented for the problem of simply supported, rectangular, orthotropic plates undergoing large deflections due to the combined action of uniform transverse pressure and compressive in-plane loading. The solution of the von Kármán-type large deflection equations is obtained in the form of double series consisting of appropriate beam functions for the lateral deflection and the stress function. Numerical results are obtained for three types of fibre–reinforced composite plates with different values of aspect ratio. The effect of the material properties on the deflection and stresses is discussed. The results in the case of isotropic plates are in good agreement with the available solutions.
On the Parameters of the Magnetic Forming Process
Authors: Al-Hassani S. T. S. , Duncan J. L. , Johnson W.
Published: February 2007

The present state of forming and of the development of analytical design techniques for the process is reviewed briefly. A comprehensive analysis of the expansion of a tube by means of an internal solenoidal coil is given; this contains new expressions for the circuit parameters and magnetic pressure and takes account of the depth of the coil conductors.

The analytical method is tested by obtaining numerical solutions and comparing these with the results of experiments in which aluminium, copper and steel tubes were formed with various discharge energies and using coils having different conductor dimensions. It is shown that the analytical method gives accurate results and is convenient to use for design purposes to optimize the process.
The Optimal Control of the Temperature Profile within a Heat Conduction System
Authors: Ball D. J. , Hewit J. R.
Published: February 2007

The implementation of an optimal control scheme for an experimental process consisting of a one-dimensional heat conduction system is considered. This is a particular application of distributed parameter theory. A linear mathematical model is assumed and the Green's function found by a least squares estimation technique using the conjugate gradient method. The optimal control is then obtained as the solution of a constrained minimization by an interior penalty method and is applied to the system.
Synthesis of Active Dynamic Controllers for Vibratory Systems
Authors: Porter B. , Bradshaw A.
Published: February 2007

The systematic procedure for the synthesis of active controllers for vibratory systems, presented in a recent paper (2)‡, is extended to embrace the many practically important cases where it is necessary to take account of dynamic effects in the feedback loops. In order to effect this extension, certain new results in modal control theory are developed.
The Influence of Frame Flexibility on the Lateral Stability of Motorcycles
Authors: Sharp R. S.
Published: February 2007

A mathematical model of a rigid-framed motorcycle running freely is extended to include the effects of torsional flexibility between the rear wheel and the frame.
A Fast Response Surface Thermocouple
Authors: Donaldson I. S. , Haslett R. A.
Published: February 2007

A fabrication technique is described for a cheap, robust surface thermocouple having a rise time of the order of 5 μs. Experimental results using the thermocouple are also presented.
Fatigue and Creep Rupture of an Acetal Copolymer
Authors: Crawford R. J. , Benham P. P.
Published: February 2007

Part 1 of this paper describes the uniaxial fatigue testing of injection-moulded cylinders made of acetal copolymer at various frequencies between 0.167 and 10 Hz. The influence of mean stress and cycle control (stress or strain) has also been studied. Two mechanisms of failure were observed: cyclic thermal softening, above certain limits of stress and frequency, and traditional crack propagation fatigue, which was found to be independent of cyclic frequency. Strain cycle control tests were thermally stable and stress range became stable after the initial 1 per cent of the total endurance. Creep rupture tests were also performed.

Part 2 considers the fatigue and creep rupture of tubular specimens containing geometrical stress raisers. These were injection moulded under the following conditions: (a) single-end gated, (b) side gated, (c) double-end gated, (d) ‘rough’ mould and polished mould. Moulding defects such as weld lines, presence of voids and sprue, poor surface finish, etc., are compared for fatigue-strength reduction with machined circumferential notches and transverse holes of known theoretical stress concentration.
The Modelling of Electrohydraulic Control Valves and its Influence on the Design of Electrohydraulic Drives
Authors: de Pennington A. , Mannetje J. J. ‘t , Bell R.
Published: February 2007

The modelling of the control valve is shown to be a factor of prime importance in the design of electrohydraulic systems. The process required to model a commercially available valve is described in detail, with equal attention to the production of the experimental data and the identification of the model parameters. The quality of the decisions made in the construction of a model is shown to be most critically evaluated when derivative feedback loops are employed. A study of a system with negative transient acceleration feedback is included to illustrate the effectiveness of a third-order model. It is demonstrated that the use of a digital computer is essential for this type of system design.
The Evolutionary State Equation of Creep
Authors: Grant C.
Published: February 2007

The state equation of creep deformation is generalized, and evolutionary internal state variables are introduced. These concepts are then used to rationalize several creep theories currently in use. Finally, a simple recovery model of creep deformation is proposed within the framework of the general evolutionary theory. The model exhibits several important characteristics of creep in metals and also illustrates some important features of the theory.
A Theoretical Model for Steady Electroviscous Flow between Parallel Plates
Authors: Arguelles J. , Martin H. R. , Pick R.
Published: February 2007

The idea of using electrosensitive fluid for fluid power control is not new. However, most of the available information is of an experimental nature. This paper presents an attempt to model the behaviour of an insulating fluid containing concentrations of small dielectric particles. Results of this analysis show that the pressure required to push the mixture between parallel plates is proportional to the square of the applied voltage. The model also indicates that the performance of the mixture is dependent on particle size and concentration of solids. Reasonable, good experimental evidence is included to support these conclusions.
On the Measurement of Dynamic Properties of Lubricants under E. H. L. Conditions Using a Disc Machine
Authors: Davies J. M. , Walters K.
Published: February 2007

Johnson and Roberts (1)‡ have recently shown how a simple adaptation of the conventional disc machine can be used to measure the viscoelastic properties of lubricants under conditions of elastohydrodynamic lubrication. The present paper contains a theoretical treatment of the problem and derives operating formulae pertinent to conditions of low, finite and high Deborah number.
The Stress Distribution in a Wedge-Shaped Metal-Cutting Tool for Triangular Distributions of Load on the Rake-Face Contact Length
Authors: Thomason P. F.
Published: February 2007

Solutions for the isothermal stress distribution in a two-dimensional infinite wedge are obtained for negative-gradient triangular distributions of normal and tangential stress, acting over a segment of the wedge surface adjacent to the apex.

The general stress-field equations are obtained in integral form by Tranter's method, which involves the application of the Mellin transform, and these equations are evaluated numerically to give the distributions of radial stress at the surfaces of a x/2 wedge. A superposition method is used to obtain the surface stresses for truncated triangular distributions of boundary loads, and the results are applied to the problem of estimating the surface stresses in a metal-cutting tool.
An Optical Technique for Measuring the Velocity of a Fluid
Authors: Kotas T. J. , Le Fevre E. J.
Published: February 2007

The technique described is based on a refraction phenomenon. Objects observed through a rotating transparent parallel-faced prism have images which move relative to the object. When the objects are small tracer particles suspended in a moving fluid, the velocity of the fluid can be measured by varying the rotational speed of the prism until the component of the image velocity normal to the prism axis is cancelled. The point in space at which the measurement is made is fixed by the intersection of the line of sight of the viewing telescope with a thin transverse beam of light used for illuminating the tracer particles.
A Finite-Difference Approach for Solving the Gas Dynamics in an Engine Exhaust
Authors: Ledger J. D.
Published: February 2007

Finite-difference schemes have been considered for solving the unsteady, compressible gas flow in the exhaust pipe of a turbocharged diesel engine. The most promising scheme, based on centred differencing, was developed to incorporate the boundary conditions applicable to the exhaust problem. Good comparisons were obtained with results for pipe pressure from characteristics programmes at intermediate and final stages of the development. Recommendations are made for reducing the computation time of the centred-difference programme.
A Nonlinear Analysis for One-Way Buckling of a Laterally Loaded Column
Authors: El-Aini Y. M.
Published: February 2007

Recently, the problem of the mechanical buckling of a long beam resting on a frictionless rigid foundation and subjected to a uniform lateral loading was analysed using a linear formulation. The purpose of this paper is to show that the linear analysis is not sufficient for predicting a correct post-buckling response and that a completely nonlinear formulation is needed. The problem is formulated as a variational problem with variable end-points. The resulting nonlinear boundary value problem is solved numerically using the ‘shooting method’. The nonlinear solution indicates the presence of a lower buckling load, before which the only state of equilibrium is the undeformed state.
Fluid Film Damping of Rolling Contact Vibrations
Authors: Dareing D. W. , Johnson K. L.
Published: February 2007

The magnitude of mechanical vibration and noise generated within machinery depends on damping. However, little is understood about how damping is distributed among the various possible damping sources. The results given in this paper isolate and quantify lubrication film damping between rolling discs and show that damping within the lubrication film contributes significantly to the total damping.

A comparison of laboratory measurements with computer calculations shows that lubrication film damping is greatest under conditions of contact separation and thus indicates that fluid film damping is generated primarily by the squeeze film mechanism.
Conical Diffusers with annular injection
Authors: Duggins R. K.
Published: February 2007

An experimental investigation was made of the possible benefits to be gained from injecting a secondary supply of fluid into a wide-angled conical diffuser through an annular slot at the inlet. The diffuser discharged through a parallel tailpipe and attention was focused on the overall pressure recovery in the cone and the tailpipe together, and on the non-uniformity and asymmetry of the flow.

The results showed that annular injection had a very favourable effect on both the pressure recovery and the flow non-uniformity. In addition, the effects of cone angle and slot width were assessed and the optimum rate of injection was established.
Thermal Rectification Due to Distortions Induced by Heat Fluxes across Contacts between Smooth Surfaces
Authors: Jones A. M. , O'Callaghan P. W. , Probert S. D.
Published: February 2007

Predictions have been derived for the distribution of true contact area and the associated constriction resistance for a pressed contact between two surfaces which are flat when isothermal but become bowed in the presence of heat fluxes across the contact. Induced thermal strains of the interfacial surfaces can lead to the preferential passage of heat in one direction across the contact. Experimental measurements of the thermal resistance of a contact between a specimen of En58B stainless steel and one of commercially-pure aluminium corroborate this theory. The study has identified some of the mistakes which can be made unconsciously, and remain unrecognized subsequently, in using standard measuring techniques for the thermal resistance of a pressed contact.
Effect of Plate Buckling on Orifice Meter Accuracy
Authors: Jepson P. , Chipchase R.
Published: February 2007

Experimental and theoretical data are presented on the effect of plate buckling on the flow measurement accuracy of an orifice meter system. Tests were performed on plastically buckled orifice plates in an 8 in (203 mm) metering system using natural gas as the working fluid. The test pipe Reynolds numbers were 0.36 times 106 and 5.2 times 106. A method is also presented to predict the flow metering errors due to plate buckling, which gives good agreement with the experimental results obtained on plastically buckled plates. The theory is extended to cover the flow metering errors caused by the elastic deformation of orifice plates under normal working differential pressures. A formula is presented which relates the metering errors to the applied differential pressure and the mechanical properties of simply supported orifice plates.
The Mechanical Properties of Electrodeposited Iron Foil
Authors: Lai S. H. F. , McGeough J. A.
Published: February 2007

Iron foil, ranging in thickness from 0.05 to 0.16 mm, has been prepared by electrodeposition with an electrolyte solution composed mainly of ferrous chloride. Bright, smooth foil is obtained for current densities of 10 to 30 A/dm2, provided that the electrolyte temperature is above 85°C. Techniques developed to measure the mechanical properties of such a thin material are discussed. Unlike conventionally produced foil, the values of the main mechanical properties of the electrodeposited material, e.g. tensile strength and hardness, increase with decreasing thickness. The properties can also be affected by the main process variables: for instance, the lower the electrolyte temperature, the higher is the tensile strength. These effects are explained in terms of changes in grain size of the foil which are largely influenced by the process variables.
A Study of Tensile Stresses in a Journal-Bearing Oil Film
Authors: Dyer D. , Reason B. R.
Published: February 2007

Tensile stresses of 740 kN/m2 have been observed in the oil film of a steadily loaded journal bearing. A critical eccentricity ratio has been suggested below which, for a particular clearance, a tensile stress may be generated.

An extensive literature survey indicates the sensitivity of the liquid's tensile strength to such factors as gas content, viscosity, particle content and the surface finish at the liquid/bearing material interface.

It is suggested that previously attempted observations of liquid tensile stresses in journal bearings may have been limited by the configuration of the pressure-measuring device.

The possibility of bearing Babbitt damage arising from transient and steady-state liquid tensile stresses is postulated.
A Solution of the Low-Speed Wheel Flutter Instability in Motorcycles
Authors: Roe G. E. , Thorpe T. E.
Published: February 2007

Motorcycles are subject to two dynamic steering instabilities, a low-speed ‘flutter’ at 6–8 Hz. and a high-speed ‘weave’ at 2-3 Hz, both of which are increased by adding a tail load, or by decreasing the rider mass. This paper is concerned with the low-speed instability, and describes work which resulted in the elimination of this potentially dangerous phenomenon from a current large-capacity motorcycle.

The cause was found to be twofold: a fundamental castor instability at the front wheel, coupled to a resonance in the upper section of the main frame.

Recommendations on future frame design are made, and fundamental limitations of the ‘telescopic’ front fork are demonstrated.
Slot-Entry Bearings for Hybrid Hydrodynamic and Hydrostatic Operation
Authors: Rowe W. B. , Koshal D. , Stout K. J.
Published: February 2007

Slot-entry bearings are compared with conventional hydrodynamic bearings and also with recessed hydrostatic bearings. Whereas recessed bearings are not ideal for hybrid operation, improvements in load capacity can be achieved by the use of non-return valves in the supply lines. However, it is shown that a much improved performance may be obtained from slot-entry bearings. Slot-entry bearings have additional advantages of manufacturing simplicity and compactness when compared with other hybrid bearings.

Experimental results for recessed bearings and for slot-entry bearings justify computer solutions at moderate values of eccentricity ratio and speed parameters.
Platen Deceleration as a Mechanism of Noise Production in Impact Forming Machines
Authors: Hodgson D. C.
Published: February 2007

The very rapid deceleration on impact of the platen (tup) in a drop forging machine is shown to be an important source of impulsive noise. An ‘explicit’ finite-difference method is used to calculate the sound pulse radiated by a platen in the form of a solid cylinder undergoing a deceleration given by

where T is the impact time. The results are presented in dimensionless form, enabling the pulse to be calculated for a wide range of platen sizes and impact times.
Large Deflection of Unsymmetric Cross-Ply and Angle-Ply Plates
Authors: Chia C. Y. , Prabhakara M. K.
Published: February 2007

An approximate solution to the von Karman-type large-deflection equations of unsymmetrically laminated, anisotropic, rectangular plates under uniform transverse load is formulated by the perturbation technique. The membrane boundary conditions are the zero normal and shear boundary forces. By expressing the load, force function and transverse deflection in the form of series, the governing equations and boundary conditions are reduced to a series of linear partial differential equations and boundary conditions. In each approximation a solution is assumed in the form of polynomials which satisfy the associated boundary conditions and physical requirements for deflection and and three membrane forces in unsymmetric cross-ply and angle-ply plates. Taking the first three terms in the truncated series, numerical results are graphically presented for the load-deflection relations, bending moments and membrane forces in unsymmetric cross-ply and angle-ply plates with various values of aspect ratio and total number of layers. The present third approximation is in good agreement with the existing solutions for large deflections of isotropic and unsymmetric angle-ply plates having the ratio of central deflection to thickness up to the value of 2.
The Use of Interferometry as an Aid to Studying Flapper-Valve Flow Characteristics
Authors: Tanner L. , Peckham R. G. , Burrows C. R.
Published: February 2007

A technique is described for visualizing the air flow over a surface by means of an oil film. The technique is used in conjunction with experimentally determined flapper-plate pressure profiles to examine the flow characteristics of a flapper-nozzle valve used to control air at 425 kPa (4.25 bar). The oil film shows clearly the points of separation and reattachment of the air boundary layer resulting from shock wave and boundary layer interaction.

Possible applications of the technique are discussed and attention is focused on the use of the oil-film technique in conjunction with interferometry as a tool for the rapid determination of the effects caused by changes in nozzle geometry.
Research Note: Effect of Mistuning on Forced Vibration of Blades with Mechanical Coupling
Authors: Whitehead D. S.
Published: February 2007

It is shown that when there is mechanical coupling between blades through their root fixings, then the maximum factor by which the vibration amplitude can increase due to mistuning is given approximately by 1/2[1 + √( N/2)], where N is the number of blades in the row. This contrasts with the factor of 1/2(1 + √ N), derived in an earlier paper, due to more general aerodynamic coupling. The cases when adjacent blades are excited either in phase or in antiphase are exceptional, and in these cases the earlier analysis applies. These factors can be closely approached when just one blade is mistuned.
The Roles of Skirt Planform and Deflection in Hovercraft Response
Authors: Reynolds A. J. , Brooks B. E.
Published: February 2007

A linearized theory of hovercraft response while moving over regular waves is modified to account for, firstly, a cushion planform other than rectangular and, secondly, deflections of the skirt enclosing the supporting cushion as a result of wave-induced variations in the internal pressures. Consideration is given to the pitching and heaving of a hovercraft whose plenum air chamber is divided into two compartments by a transverse barrier. Detailed calculations are carried out for a cushion planform whose forward part is hexagonal and for a vertically deflecting skirt hemline, but the results are more widely useful in suggesting the general nature of the roles of cushion planform and skirt dynamics. A method of representing the overall effect of skirt deflection is proposed, involving four dimensionless coefficients, and the effect of these coefficients on the dynamic characteristics is investigated.
Free Vibration of Blade Packets
Authors: Thomas J. , Belek H. T.
Published: February 2007

The free-vibration characteristics of shrouded blade packets are studied using the finite-element method. The effects of various weight ratios, flexural rigidity ratios and length ratios between the blades and shrouds on the frequencies of vibration of the blade packet are investigated.

It is shown that the vibration characteristics of a multibladed packet can be predicted with reasonable accuracy from the inference diagram of a two-bladed packet.

The theory developed can be easily adapted for more complex blade packet configurations. The results presented for the frequencies of vibration are compared with experimental results and show good agreement with those of other investigators.
Oil-Film Starvation in Elastohydrodynamic Circular Contacts
Authors: Vakilzadeh A. , Gohar R.
Published: February 2007

A formula for the oil-film thickness in a starved, elastohydrodynamic, circular contact is presented in terms of external parameters. Experiments are described which confirm the theory. Also examined are the oil droplet around the contact region, and the track shape made by the passage of the balls on the races.