bluuebunny/crossref_metadata_2025 huggingface dataset:
Research Note: End Closure in Elastohydrodynamic Line Contact
Authors: Bahadoran H. , Gohar R.
Published: February 2007

An approximate theory gives the shapes of the surfaces at the end of an elastohydrodynamic line contact. There is good agreement with experiment.
Research Note: A Method for Assessing the Maximum Temperature of Exhaust Valves in Internal Combustion Engines
Authors: Tomlinson G. R. , Leonard R. , Henshall S. H.
Published: February 2007

The concept of mean cycle temperature has been used, by Seale and Taylor (1)§, to calculate heat transfer in pistons and liners of internal combustion engines. However, this technique cannot be used for exhaust valves because the valve temperature exceeds the gas mean cycle temperature. In this work it is shown that a ‘mean temperature’, based solely upon radiation considerations, yields a simple method for assessing the maximum temperature of exhaust valves and that the results obtained from engine tests are in close agreement with those predicted. The engine used in the investigation was a Mirrlees Blackstone K Major four-stroke diesel engine of 380 mm bore, operating with a b.m.e.p. of 1660 kN/m2at 600 rev/min.
Theoretical and Experimental Investigations of a Short 360° Journal Bearing in the Transition Superlaminar Regime
Authors: Black H. F. , Walton M. H.
Published: February 2007

An empirical treatment is used to derive effective viscosity constants governing pressure-induced flows in Taylor Vortex regimes. The theory of static and linearized dynamic behaviour of a short journal is developed, including an approximate representation of fluid inertia effects. Theory is compared with experimental results of duty parameters, attitude loci and dynamic forcing due to rotation of an eccentric journal.
A Nonlinear Theory for a Hovercraft Moving over Regular Waves
Authors: Reynolds A. J.
Published: February 2007

The equations governing the heaving and pitching of a hovercraft supported on two interconnected plenum compartments are integrated numerically to find the response as the craft passes over sinusoidal waves whose crests are normal to the direction of motion. When the flexible skirt around the plenum chambers comes into contact with the wave profile, it is assumed to collapse against the unyielding surface of the water. The scheme of integration is explained, and predictions of accelerations experienced on the craft are compared with those from a linearized theory developed earlier. For the range of wave heights considered, the accelerations indicated by the nonlinear theory are normally higher than those of the linear theory; save near pitching resonance, the two predictions differ by less than fifty per cent. For small wave heights, the ultimate response retains significant elements linked to the natural frequencies of pitch and heave.
Finite Elastic Deflections of a Centrally Loaded Bar Supported by Two Pivoted Symmetrical End-Links
Authors: Gorski W.
Published: February 2007

The paper presents a comprehensive analysis of finite elastic deflections, under static conditions, of a light, inextensible, centrally loaded bar supported by two pivoted symmetrical end-links. The analysis is based on the exact Bernoulli-Euler equation of flexure. The characteristic equation of the system is derived and the expressions for the compatible values of the central force and the various components of deflection are obtained in dimensionless parametric form in terms of elliptic integrals and functions.
Research Note: Limit Loads of Cylindrical Shells under Band Pressures
Authors: Haydl H. M. , Sherbourne A. N.
Published: February 2007

The purpose of this brief note is to point out that a numerical approach to the limit analysis of discontinuously-loaded cylindrical shells is simple and appears to be useful for designers and engineers. In particular, we illustrate the numerical method by solving the title problem.
Research Note: Pressure Drop during Steam/Water Flow through Orifices
Authors: Chisholm D. , Rooney D. H.
Published: February 2007

A method of predicting the pressure drop during steam/water flow through orifices is presented, which extends an existing procedure to give improved agreement with experiment at conditions of low dryness fraction.
Secondary Flow in Cascades: The Effect of Axial Velocity Ratio
Authors: Marsh H.
Published: February 2007

By considering the flow through a many-bladed cascade, a simple theory is developed for the effect of a change in axial velocity on the secondary flow at exit from a cascade. An expression is derived for the difference in the time taken for fluid particles to travel over the two surfaces of the blade and this is used, along with Kelvin's circulation theorem for incompressible flow, to obtain an equation for the distributed secondary vorticity. It is shown that for the row of inlet guide vanes tested by Gregory-Smith (1)†, the change of axial velocity across the blade row has a significant effect on the secondary vorticity.
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.
A Numerical Simulation of Finite-Width Thrust Bearings, Taking into Account Viscosity Variation with Temperature and Pressure
Authors: Tieu A. K.
Published: February 2007

A variational principle for a thin-film incompressible flow with viscous dissipation has already been formulated as the basis of a finite-element analysis and applied to solve the oil-film energy equation for the case of infinitely wide thrust bearings (1)†. Here, the finite-element method is extended to a three-dimensional oil film, the pressure and temperature distributions of which agree very well with those obtained from other theoretical and experimental work. Allowance for various factors affecting thrust-pad performance, such as hot oil carry-over, rotor surface temperature and pad radial tilting, in the non-isoviscous bearing analysis has been shown to improve the agreement between numerical simulation and experiment.
An Improved Holzer Procedure for Torsional Vibration Analysis
Authors: Dawson B. , Davies M.
Published: February 2007

An automatic, root-searching, extended Holzer method is described that is guaranteed to determine all the natural frequencies of a system with the exception of those values lying within prescribed tolerance bandwidth limits. The method is described and illustrated by the determination of the natural frequencies of an eight-rotor free-free torsional vibration system.
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.
An Experimental Study of Multiple Jets Directed Normally to a Cross-Flow
Authors: Sterland P. R. , Hollingsworth M. A.
Published: February 2007

Experiments were conducted to study the flow of air jets from a row of identical orifices equally spaced across the floor of a duct which carried an initially uniform airstream. As the pitch of the jets was increased the rate of decay of the jet velocity increased steadily and the penetration of the jets, after initially decreasing, passed through a minimum at a pitch of about four orifice diameters and then increased. This minimum penetration was much less than that of a single jet. Circulation occurred in the lee of the jets when their pitch was less than about three orifice diameters, if the jet-to-cross-stream momentum ratio was high enough. The amount of circulation increased as the jet pitch was reduced and as the momentum ratio was increased.
Nonconvergence in the Computation of Turbomachinery Performance
Authors: Okiishi T. H. , Pullen C. R.
Published: February 2007

Some examples are described of premature nonconvergence and resulting loss of solution of an iterative computer-based procedure for predicting the off-design performance data of an axial-flow pump. Caution in interpreting nonconvergence in similar procedures is suggested. A brief description is given of how the axisymmetric, constant density, steady, adiabatic, locally inviscid blade-element flow model subject to the simple radial-equilibrium condition is used as the basis of the present computation procedure with losses and deviation angles based on correlations of numerous pump rotor data. The base velocity estimation procedures, as well as the loss and deviation angle calculation methods used, are shown to have significant influence on solution convergence. While the examples described are specific, it is believed that the related conclusions are generally applicable to turbomachine flows involving large blade-row exit axial velocity gradients and/or near-zero local axial velocities.
Conditions for the Neutralization of Excitation by the Teeth in Epicyclic Gearing
Authors: Seager D. L.
Published: February 2007

Excitation of vibration by the teeth in a simple epicyclic gear system is considered, and it is shown that some of the potentially troublesome harmonic components can be neutralized by suitable choice of tooth numbers. In particular, the tooth frequency components acting on the central members are found to be neutralized if the number of teeth on the sun divided by the number of planets ( ZS/n) ≠ integer and ( ZS ± 1)/ n ≠ integer, provided that one of the central members is fixed. The practicability of satisfying the conditions and factors which tend to reduce their effectiveness are discussed.
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 Resistance of a Closed-Ended, Annular, Air-Filled Cavity: Inclination and Eccentricity Dependence
Authors: Sadhu D. , Probert S. D. , Medwell J. , Syed D.
Published: February 2007

The steady-state rate of heat flow from a cylinder of uniform temperature (≤ 185°C) to a surrounding, concentric, water-cooled pipe has been measured experimentally. For such a closed-ended annular-cavity configuration with 23 ≤ h ≤ 40 and 1.8 times 103 < Ra < 105, where h is the aspect ratio and Ra the Rayleigh number, the heat flux exhibited a maximum at an inclination of 17 ± 2° to the horizontal. The vertical system was the maximum insulation configuration. Eccentric displacement of one vertical cylinder relative to the other, for a fixed temperature difference between the vertical cylinders, always led to an increase in the rate of heat transfer, but for eccentricities up to 0.3 the changes were negligible. The rate of heat flow for the horizontal assembly increased as the axis of the inner cylinder was eccentrically displaced vertically downwards relative to that of the outer cylinder.
On the Modification of Subsystems in Structural Dynamics
Authors: Mahalingam S. , Bishop R. E. D.
Published: February 2007

Suppose that it is required to find what effects some local modification would have on the vibration characteristics of a structure if a portion is to be replaced. It is shown how, in theory at least, the modified characteristics can be found from a knowledge of those relating to the whole of the original structure and those relating only to the unit which is to be inserted.
Fluid Flow in Perforated Pipes
Authors: Bailey B. J.
Published: February 2007

Values of the discharge coefficient for air flow through single holes in a pipe wall, and for the angle of efflux are reported. The variation of static pressure along tubular polyethylene air ducts with a maximum length-to-diameter ratio of 250 containing pairs of diametrically opposed holes has been measured. This information was used with data on friction loss to determine values for the coefficient of static pressure regain. It was possible to predict variations in static pressure and air discharge along uniformly perforated ducts which were in good agreement with those observed experimentally.
Research Note: Average Friction Coefficients in Gears
Authors: Rao A. C.
Published: February 2007

Variation in sliding velocity—both in magnitude and direction—during a meshing cycle, the load distribution among the pairs of teeth, and the accuracy with which teeth are cut are some of the factors that make the mathematical analysis of friction in gear teeth extremely difficult. Of these, sliding velocity, which is responsible for the formation of an oil film between the teeth, plays an important role, and any attempt to determine the friction coefficients must take account of changes in sliding velocity. In this note an expression has been developed, considering the variation in sliding velocity, for power loss in terms of the coefficient of friction and gear parameters. The experimental results are compared with those obtained by other methods.
Research Note: A General Method of Structural Analysis for Marine Structures and Vehicles
Authors: Bishop R. E. D. , Price W. G.
Published: February 2007

It is shown that an analytical approach which has recently been formulated for the structural dynamics of ships is not dependent on the prismatic shape of a hull. Nor does it require the structure to be free of the sea-bed. On the contrary, the approach suggests a practical technique for stress-analysing marine vehicles and structures of all types—that is, insofar as linear theory is adequate.
Creep of Thick-Walled Orthotropic Cylinders Subject to Combined Internal and External Pressures
Authors: Arya V. K. , Bhatnagar N. S.
Published: February 2007

A creep analysis of a thick-walled anisotropic cylinder subject to combined internal and external pressures is presented. The elastic strains are also taken into account. By considering the creep rate as a function of stress multiplied by a function of time (time-hardening law), the fundamental equations for the creep of an orthotropic cylinder are obtained. These equations are solved for the particular case of planar anisotropy. A numerical example pertaining to the case of internal pressure is given and the results obtained for the anisotropic case are compared with those for the isotropic case.
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.
Use of the J Contour Integral in Elastic-Plastic Fracture Studies by Finite-Element Methods
Authors: Sumpter J. D. G. , Turner C. E.
Published: February 2007

In Part 1, a brief summary of the justification and advantages of the use of the J contour integral in elastic-plastic finite-element analysis is given. A more detailed appraisal is then made of its interpretation as an energy balance concept in the presence of irreversible plastic deformation. Numerical illustration of the points made is provided by an elastic-plastic finite-element analysis on a series of monotonically loaded centre-cracked plates of different 2 a/W ratios. With incremental plasticity it is concluded that although an energy balance interpretation can be assigned to J, it is not a release rate of energy available to propagate a fracture. In Part 2, the role of J as a crack-tip characterizing parameter is examined with the help of elastic-plastic finite-element analysis. The evidence indicates that a given value of J does not ensure a unique crack-tip environment for different cracked-body geometries. It may, however, characterize the crack tip adequately for some engineering purposes and, in particular, may be used to model the fracture behaviour of a large-scale test using a smaller but geometrically similar specimen, for a given degree of through thickness constraint.
A Flow Calorimeter Suitable for Use up to 100 Megapascals and 400°C
Authors: Bruges E. A.
Published: February 2007

Preliminary test results are given for a flow calorimeter, made of stainless steel, suitable for use in closed-circuit calorimetry up to 100 MPa and 400 C.
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.
Measurement of the Elastic Moduli of Structural Adhesives by a Resonant Bar Technique
Authors: Adams R. D. , Coppendale J.
Published: February 2007

A method of measuring the dynamic torsion and Young's moduli of a thin film of adhesive is described. The accuracy of the technique and its suitability for structural adhesives is discussed. Values of modulus obtained using this method are compared with values obtained from static and dynamic tests on bulk specimens of three epoxy adhesives.
Pressure Distribution, Roll Force and Torque in Cold Ring Rolling
Authors: Mamalis A. G. , Johnson W. , Hawkyard J. B.
Published: February 2007

Normal pressure distribution, roll force and torque are measured accurately when rolling plain and profiled rings by using the pin-type pressure-transducer technique. A simple theoretical model, based on the plane strain slip-line field solution for the indentation of a block by opposed flat indenters, is developed to provide an estimate of roll force and torque for profiled rings. The driving torque is also predicted by deriving the resultant force and the lever arm. Examination of the results indicates that, in contrast to conventional strip rolling, the normal pressure distribution in ring rolling shows an early peak soon after the entry plane and that conventional friction-hill theory appears inapplicable. Recognizing the appreciable differences in geometry in the roll gap and elsewhere, flat rolling analysis seems generally inappropriate to ring rolling.
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.
Research Note: Hysteresis Loss in Ball and Roller Bearings
Authors: Chu P. S. Y.
Published: February 2007

Hysteresis losses in ball and roller bearings are derived through simple integration from expressions of velocity and hysteresis in the balls and rollers.
Research Note: Reduction in Relaxation Oscillation (Stick-Slip) Amplitudes by Normal Excitation
Authors: Hunt J. B.
Published: February 2007

When a slider-slideway system was excited by vibratory forces applied normally to the contact surface, it was found that at low sliding speeds the amplitude of stick-slip oscillation could be reduced to a negligible value. By exciting at one of the structural resonant frequencies of the system, the maximum value of the vibratory forces required was only a small percentage of the slideway load. The value of the coefficient of friction between the two surfaces was not reduced.
Analysis for Improved Design of an Oil Cushion
Authors: Satter M. A.
Published: February 2007

An oil cushion that has been reported earlier by the author (1−2)†is further investigated to establish its optimum performance characteristics. In particular, the effects of clearance between the piston and cylinder, the oil escape area and different types of input force on the dynamic behaviour of the oil cushion are studied. A singularity that occurred in a previous study (2) has now been successfully eliminated. A simple but accurate numerical solution to the second-order nonlinear equation of motion is also presented.
The Damping Characteristics of Vibration Isolators Used in Gas Turbines
Authors: Holmes R.
Published: February 2007

The linear and nonlinear damping performance of a common type of gas-turbine vibration isolator, consisting of a squeeze-film journal bearing in parallel with a linear retainer spring, is computed and used to prescribe limits to the use of linear damping coefficients.
The Failure of Double-Skinned, Composite, Circular Cylindrical Shells under External Pressure
Authors: Montague P.
Published: February 2007

In addition to the tests previously reported (1)†, ten further double-skinned composite shells of imperfect geometry were collapsed under external pressure. This paper seeks to relate the performance of the shells to their theoretical strength and stability failure pressures. One of the conclusions is that this type of shell can be confidently designed to withstand pressures equal to or, if required, greater than the pressure required to cause yielding of the steel membranes in the circumferential direction.
Thermoelastic Analysis of a Finite Orthotropic Slab
Authors: Aköz A. Y. , Tauchert T. R.
Published: February 2007

Stationary two-dimensional temperature and stress distributions are examined for an orthotropic elastic body having a rectangular boundary. Temperature fields are determined for situations in which one edge of the rectangle experiences an arbitrary variation of temperature, heat flow or convection, while each of the remaining edges is either insulated or maintained at the initial temperature. Displacement potentials are then used to find the thermal stresses for those cases in which the temperature remains constant over two opposite ends of the rectangle. As an illustrative example, the temperature and stresses resulting from a uniform temperature rise over a portion of one edge of the rectangle are computed; numerical results are given for a fibre-reinforced composite material.
On the Lubricating Action of Molten Polymers in Single-Screw Extruders
Authors: Carlile D. R. , Fenner R. T.
Published: February 2007

An experimental investigation of metallic contact between the screws and barrels of extruders processing polymeric materials is described. Above a critical shear stress of the order of 105 N/m2, contact is obtained between screw flight and barrel under all operating conditions. This critical value is similar in magnitude to that associated with the onset of melt fracture in capillary flow. It is therefore suggested that slip in, or near, the clearance reduces or eliminates polymer hydrodynamic lubrication of the screw. Below the critical shear stress, the hydrodynamic lubrication associated with a continuous film is capable of supporting substantial lateral loads applied to the screw.
On a Problem in the Dynamics of Looped Cables
Authors: Parbery R. D.
Published: February 2007

The paper describes a problem in the dynamics of cables. Equations of motion are derived for a cable suspended by its ends which are subjected to prescribed vertical movement. A number of approximate solutions of the quasistatic type are investigated and numerical examples are calculated to show the effect of the acceleration and velocity of the end points.
Slope Measurement in Surface Texture Analysis
Authors: Chetwynd D. G.
Published: February 2007

This paper examines the use of some differential formulae in the context of surface texture profile analysis. After a theoretical analysis, their behaviour on real profiles was studied. It is shown that simple models of real profiles are adequate to predict the observed behaviour and so allow a judgement to be made on the accuracies of the formulae under real conditions.
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.
A Procedure for Force-Balancing Planar Linkages Using Counterweights
Authors: Oldham K. , Walker M. J.
Published: February 2007

This paper presents a procedure for obtaining the conditions for a full force-balance of a planar linkage. It includes a check on whether a full force-balance is possible where the presence of prismatic joints or links that cannot be counter-weighted for some reason may preclude this. The procedure automatically uses the minimum number of counterweights and keeps the added inertia low. An example demonstrates the advantages of the procedure over those methods that require the derivation of the kinematic equations of motion for the linkage.
Squeeze Films between Two Rough Rectangular Plates
Authors: Prakash J. , Christensen H.
Published: February 2007

The paper describes a theoretical analysis of the effects of various types of surface roughness on the response of a squeeze film between two rectangular plates of finite dimensions. Unlike other finite bearing geometries, it is possible to obtain analytical solutions for various bearing characteristics, thus facilitating a more comprehensive parameter study than has hitherto been feasible. It is shown that the nominal geometry has a profound effect on the system.
The Dynamics of an Imperfect, Multigimbal, Hooke's-Joint Gyroscope
Authors: Burdess J. S. , Fox C. H. J.
Published: February 2007

The paper examines the effect of damping and mistuning on the performance of a dynamically-tuned, multigimbal, Hooke's-joint gyroscope. The dynamic stability of the gyro is considered and rotor damping is shown to be a source of instability at rotor speeds in excess of the tuning speed. Using an approximate solution to the governing equations of motion, it is shown that the instrument's capacity to measure either rate of turn or total angular displacement is limited by the degree of mistuning and the damping conditions. The response of the tuned instrument to harmonic inputs at twice rotor frequency is examined and the conditions for a 2ω drift-free gyro are derived.
The Role of Subatmospheric Film Pressures in the Vibration Performance of Squeeze-Film Bearings
Authors: Humes B. , Holmes R.
Published: February 2007

A theoretical model of the squeeze-film bearing unassisted by a retainer spring is developed, based on experimental information revealing the ability of the squeeze-film to sustain appreciable subatmospheric pressure.
Dynamic Stiffness and Damping Coefficients of Aerostatic, Porous, Journal Bearings
Authors: Rao N. S. , Majumdar B. C.
Published: February 2007

A periodic (displacement) disturbance is imposed on an aerostatic, porous, journal bearing of finite length under steady-state conditions. The dynamic pressure distribution is obtained by a pressure perturbation analysis of Reynolds equation and a modified flow continuity equation in a porous medium. Dynamic stiffness and damping coefficients for different operating conditions are calculated numerically, using a digital computer, and presented in the form of design charts.
Performance of Composite, Flat-Belt-Drive Materials under Simulated Power Transmission
Authors: Palmer R. S. J. , Jarvis J. L.
Published: February 2007

A method of simulating a flat belt drive under power-transmission conditions is given. Stress-strain data are obtained using a photoelastic coating technique. Tension-strain equations are evaluated using a computer program based on Forsythe's method of orthogonal polynomials. An indication of how the data may be used to arrive at the operating tensions of an actual belt drive is given.
Statistical Analysis of a Rough-Surface Model
Authors: Demkin N. B. , Berkovich I.I. , Kourova M. S.
Published: February 2007

The ‘stereometrical’ characteristics of the rough surface layers of engineering components, which are necessary for the calculation of rough-surface contact parameters, are often identified with the ‘planimetrical’ ones obtained from single profiles. In this paper, a relationship is obtained between these characteristics. Asperities are modelled by segments of spheres of equal radius and arbitrary height.
A Thin-Film Probe for the Measurement of a Three-Dimensional Velocity Vector
Authors: Aggarwal J. K. , Bellhouse B. J.
Published: February 2007

A new hot-film probe intended for the measurement of velocity, in magnitude and direction, in three-dimensional water flow is described. Using boundary layer theory, the response of the probe to steady velocity is derived and is found to agree closely with calibrations. The probe has proved to be robust and durable; it produced reliable and repeatable calibrations when towed in a water tank. The method of data acquisition and the technique used for computing the velocity vector are reported.
Large-Deformation Response of Deep Circular Arches to Radial Magnetomotive Forces
Authors: Al-Hassani S. T. S. , Hashmi M. S. J.
Published: February 2007

Circular-arch specimens were produced from aluminium rings. By using suitable rigid inserts in a ring, only a small portion of it was allowed to deform freely. The rings were subjected to uniformly-distributed, radially-inward-directed impulsive forces. The forces were generated by a high-energy electrical discharge through a single-turn coil which surrounded the ring. The induced currents in the ring were high enough to engender large, transient, radially-directed magnetomotive forces which caused gross plastic deformation. The elastic–plastic response of the arches was predicted by using a finite-difference numerical technique to solve the equations of motion. The analysis allows for circumferential and shear forces, as well as large changes in geometry. It also incorporates strain-hardening, but it ignores the influence of rotary inertia. High-speed photographs were used to record the transient shape of the collapsing arches. These were found to be in good agreement with the predicted profiles.
The Starved Lubrication of Piston Rings in a Diesel Engine
Authors: Moore S. L. , Hamilton G. M.
Published: February 2007

Miniature pressure and film thickness transducers mounted in the cylinder liner of a diesel engine have been used to study the lubrication of piston rings. The method of using the gauges to determine oil starvation in the inlet of the rings is described and results from a working engine are presented. Calculations for both starved and fully flooded rings have been carried out and are compared with the measured results.
Servovalve-Controlled Pneumatic Suspensions
Authors: Esmailzadeh E.
Published: February 2007

A linear analytical model of a ground-vehicle suspension system employing a pneumatic isolator and a three-way servovalve is developed. Damping is provided by connecting the pneumatic spring to a constant-volume surge tank through capillary resistances. Non-dimensional dynamic equations for the valve-controlled, self-damped, pneumatic isolator are derived and the effects of various feedback and feedforward controls on the performance of the closed-loop system are pointed out. Experiments are conducted to verify the validity of the assumptions made in deriving the absolute and relative displacement transmissibilities and the vehicle model is simulated on an analogue computer. It is shown that a servovalve-controlled pneumatic suspension system not only considerably reduces the body transmissibility at very low frequencies, but is also capable of very good isolation throughout the broad frequency range.
A Calculation Procedure for Three-Dimensional, Time-Dependent, Inviscid, Compressible Flow through Turbomachine Blades of any Geometry
Authors: Bosman C. , Highton J.
Published: February 2007

A method for calculating three-dimensional, time-dependent, inviscid, subsonic flow is presented. Application is made to flow through the rotor of a small radial inflow turbine and comparison with conventional through-flow calculations and experimental results is made. The nature of the strong secondary flow in this rotor indicates the probable inadequacy of the two-dimensional calculations which is confirmed by the comparison.
The Isothermal Stirling Cycle with Arbitrary Equation of State
Authors: Organ A. J.
Published: February 2007

The isothermal analysis of the practical Stirling cycle is generalized so as to be applicable to all working fluids for which an equation of state may be written v s = v s( p, t), given that v s (specific volume) has a unique value for specified p, t. The treatment is exemplified by reference to a refrigerating machine operating near the critical point of its working fluid. The results suggest that caution may be necessary in the selection of operating pressures when certain gases are used as working fluids in reversed Stirling-cycle machines.
Low Reynolds-Number Flow in the Vicinity of Axisymmetric Constrictions
Authors: Vlachos N. S. , Whitelaw J. H.
Published: February 2007

Numerical solutions of the two-dimensional, Navier-Stokes equations are presented for boundary conditions corresponding to the laminar flow of Newtonian and non-Newtonian fluids in a round tube with axisymmetric constrictions. The influence of Reynolds number, blockage diameter ratio and length on the velocity components, streamlines, local shear stress and pressure drop are quantified and, in the case of the first two, shown to be large. The non-Newtonian stress-strain relationship corresponds to that for blood flowing in venules and results in an increased recirculation length and larger regions of high shear stress.
Oblique Perforation of Targets by Small Armour-Piercing Projectiles
Authors: Woodward R. L. , Baldwin N. J.
Published: February 2007

In order to simplify the analysis of results, most investigations of oblique impact have restricted the range of target properties so that only one failure mode is obtained. The present work attempts to show the influence of failure mode on oblique impact by using targets having a wide range of strengths. Experiments are described in which the critical angle to defeat 0.30-calibre APM2 projectiles at two impact velocities and two target thicknesses is obtained for steel targets ranging in hardness from 270 to 735 HV. The data are used to investigate the effect of oblique impact on areal density, and it is found that softer targets (less than about 450 HV) give greater improvement in areal density with angling. The mode of target failure is related to the penetration resistance/hardness relationship. It is found that the angling of targets raises the hardness at which adiabatic shear begins to cause a reduction in penetration resistance in steels with hardness, from about 350 HV to around 430 HV. This effect appears to be associated with the changing geometry of penetration, due to the dynamics of oblique impact suppressing the onset of a concentrated shear.
Pressure Transients Generated during the Rapid Braking of Asymmetric Hydraulic Actuators
Authors: Martin H. A. , McCloy D.
Published: February 2007

This paper presents a theoretical and experimental study of the pressure variations that arise when a moving inertia load, driven by a hydraulic actuator, is braked by returning the closed-centre spool control valve to its mid-position. There are two predominant nonlinearities—the occurrence of cavitation in the hydraulic oil and the relationship between load position and hydraulic stiffness. A mathematical model is derived and solutions are obtained by three methods. The first is a digital simulation on a mini-computer, the second uses phase plane, and the third uses the techniques of small perturbations to linearize the problem. For typical values of the parameters, the linearized analysis is shown to yield results in good agreement with the computer solution. When the valve is moved rapidly from an open to a closed position, large pressure peaks and cavitation can occur. This has been verified experimentally with good agreement between predicted and observed pressure peaks. Thus the maximum pressure generated can be conservatively estimated using the straightforward linear expressions.
The Dynamics of a Ligament-Suspended North-Seeking Gyroscope
Authors: Fox C. H. J. , Maunder L.
Published: February 2007

The dynamical characteristics of a North-seeking gyroscope are ivestigated. Five modes of free vibration are predicted. The response to harmonic horizontal disturbances of the point of suspension contains resonances associated with the natural fequencies that are predictable from first-order linear vibration theory. A higher order approximate solution shows that significant second-order effects occur in the form of ultra-harmonic resonances and a steady-state error in indicated North. Experimental confirmation of the theoretical predictions is reported.
Some Comments on the Stress Concentration and Shakedown Factors for Spherical Pressure Vessels with Flush Radial Cylindrical Nozzles
Authors: Robinson M.
Published: February 2007

Some previous theoretical shakedown pressures for a cylinder—sphere vessel under internal pressure are, for a certain range of parameters, shown to be too high. The error can be traced to an underestimate of the stress concentration factor owing to the use of the centreline thin-shell theory and the neglect of cylinder stresses. It is shown that much more theoretical and experimental work needs to be done to establish reliable shakedown pressures for a comprehensive range of parameters. A simple design proposal is suggested which should meanwhile prove adequate.
An Experimental Method for the Determination of Journal-Bearing Stability Parameters. Part 2: Experiment
Authors: Simmons J. E. L.
Published: February 2007

The design of a flexibly mounted journal-bearing apparatus is described, and it is shown how the experimental results may be used to generate stability charts for design. For reasons of simplicity in demonstrating the basic principles, this work has been carried out using a plain circular air bearing. The underlying theory, however, is common to all journal-bearing systems, and it is intended to extend the experimental method to liquid-lubricated bearings and non-circular profiles. In addition to the stability data which have been obtained, the apparatus has enabled a detailed study of the phenomenon of whirl cessation.
The Numerical Solution of Choked and Supercritical Ideal Gas Flow through Orifices and Convergent Conical Nozzles
Authors: Alder G. M.
Published: February 2007

The paper describes the numerical solution of the equations of compressible flow through axisymmetric convergent nozzles. The class of supercritical flows is considered, in which the gas velocities in the jet downstream from the throat are supersonic. The subsonic region of the flowfield is solved in the hodograph plane by a finite-difference method. The supersonic region is solved in the physical plane by the method of characteristics. The stream function distribution on the sonic line is adjusted iteratively to match the boundary conditions at the lip and free streamline. Discharge coefficients are evaluated and truncation errors in the results are considered.