bluuebunny/crossref_metadata_2025 huggingface dataset:
A Simple Method of Obtaining Creep Rates of a Thick-Walled Cylinder under Internal Pressure
Authors: Fairbairn J. , Mackie W. W.
Published: February 2007

Cylinder creep rates are determined from the results of a single creep test in uniaxial tension. The method is supported by limited experimental data.
Choice of a Computing Procedure for Digital Computer Synthesis of Reciprocating Engine Cycles
Authors: Annand W. J. D.
Published: February 2007

Synthesis of reciprocating engine cycles requires stepwise calculation of the charge state from point to point round the cycle. Calculation can proceed either by numerical integration of the differential form of the first law of thermodynamics, or by iterative solution of an explicit non-linear equation for one state parameter at the end of a step (embodying, of course, approximations to the integrated heat and mass transfers during the step). Evidence is presented that the iterative method is superior to integration by a fourth-order Runge-Kutta procedure.
Vibration of Box-Type Structures with Flexible Joints between Constituent Plates
Authors: Dickinson S. M.
Published: February 2007

In a recent paper by Dickinson and Warburton (1), an analytical method of determining natural frequencies and mode shapes of box-type structures having rigid joints between constituent plates was given. Practical box-type structures may well include joints having some flexibility, and it is the purpose of this Note to indicate how the earlier analysis can be modified to apply to such structures and to show the effect of joint flexibility on the natural frequencies of a particular structure.
Electronic Analogue Computer Study of Non-Linear Effects in a Class of Hydraulic Servomechanisms
Authors: Panjaby J.
Published: February 2007

An electronic analogue is first described, of a system comprising a prime mover controlled by a non-linear flyweight governor using a non-linear hydraulic jack/valve servomechanism as a power amplifier to operate the prime mover energy supply control valve.

The governor non-linearity is due to static and Coulomb friction.

When dimensionless equations of motion are used for the various components in the system, the analogue is representative of a type of control system often encountered in mechanical engineering.

It is shown that the presence of static friction in the governor, of magnitude greater than the Coulomb friction, has a de-stabilizing eifect and limit cycling of the system in the autonomous and non-autonomous conditions, caused by governor friction, is examined.
A Theory on the Mechanics of Axisymmetric Extrusion through Conical Dies
Authors: Lambert E. R. , Kobayashi Shiro
Published: February 2007

For axisymmetric extrusion through conical dies, an admissible velocity field without discontinuities was obtained by superposition of basic flow patterns. Based on this velocity field, the upper bound to the average forming pressure and the detailed mechanics were calculated for the extrusion of a rod with a semi-cone angle of 45° and a reduction of 75 per cent in area.

Three different friction conditions along the die were considered and their influence on the deformation characteristics was discussed. Flow lines, velocity components, grid distortion, strain-rate components, effective strain rate, effective strain, and stress components were plotted. A comparison of the present results with those obtained experimentally (visioplasticity) shows good agreement.
Numerical Solutions of the Navier-Stokes Equations for Axisymmetric Flows
Authors: Strawbridge D. R. , Hooper G. T. J.
Published: February 2007

A numerical method is presented for the solution of the time dependent Navier-Stokes equations for the axisymmetric flow of an incompressible viscous fluid. The method is applied to the problems of Taylor-vortex flow about an enclosed rotating cylinder and between infinite concentric cylinders, and to the analysis of the flow through a labyrinth seal. The torque calculations, which show favourable agreement with experiment, and the resulting flow patterns are presented graphically.
Radiation-Damage Stresses in the Graphite of Power-Producing Nuclear Reactors
Authors: Head J. L. , Sockalingam K. C.
Published: February 2007

When graphite is irradiated by fast neutrons, damage to the crystal structure causes changes of the graphite dimensions. In the graphite blocks comprising the core of a nuclear reactor, there are differential dimensional changes, thus stresses are developed, analogous to thermal stresses in a body in which there are spatial variations of temperature.

The stresses are partially relaxed by an irradiation-induced creep of the graphite. In this paper the authors present a method of predicting the stresses which makes allowance for the relaxation by irradiation creep.
Metal Fibre Reinforced Thermoplastics and the Role of Adhesion Efficiency
Authors: Pakdemirli E. , Williams J. G.
Published: February 2007

An analysis of composites for any fibre orientation and an adhesion efficiency between the fibre and the matrix is given. The special cases of unidirectional, crossed and random reinforcement are evaluated. The manufacture and testing of some metal-thermoplastic composites are described. The moduli achieved are then compared with the theoretical predictions and the form of the dependence of the adhesion efficiency on fibre modulus/matrix modulus ratio, aspect ratio of fibres, time and loading history is discussed. The relative performance is compared on a basis of stiffness per unit weight.
Zero (Or Low) Torsional Stiffness Couplings
Authors: Chapman C. W.
Published: February 2007

In many rotating systems shaft couplings of low torsional stiffness may bring dangerous one node critical speeds below the operating speed range. However, even soft couplings on multi-mass systems may allow higher node criticals to remain in the operating range. If two sections of a system be coupled by a coupling of zero stiffness torsional impulses cannot be transmitted from one section to the other, thus eliminating criticals.

Coupling stiffness must be related to the torque transmitted, and experiments indicate that a stiffness/torque ratio below about 4 is almost as effective as zero stiffness.
Pressure Due to Inertia in a Journal Bearing
Authors: Akers A.
Published: February 2007

A method has been suggested whereby the increment in pressure due to inertia of the rotating fluid film at the periphery of a journal bearing can be estimated theoretically. The value of this increment, obtained from the experimental results by simple subtraction, agrees to within 15 per cent of the theory. The subtraction also leads to pressure distributions which agree well with isoviscous theory.
Cage and Roller Slip in High-Speed Roller Bearings
Authors: Boness R. J.
Published: February 2007

This paper describes the start of an investigation into the factors affecting cage and roller slip in high-speed roller bearings. Cage and roller speeds, for different radial clearances, are measured over a range of steady radial loads and shaft speeds, using several lubricants. These results are analysed and compared with existing theoretical evidence. To improve the correlation between theory and practice further theoretical results of cage and roller motion are obtained for bearing conditions relevant to the regime where the fluid pro-perties are pressure dependent. The theoretical extent of cage and roller slip shows only a fair agreement with the experimental findings. However, the load below which cage slip will occur is much more accurately forecast.
Dynamic Viscosity of Compressed Water to 10 Kilobar and Steam to 1500°C
Authors: Bruges E. A. , Gibson M. R.
Published: February 2007

Equations specifying the dynamic viscosity of compressed water and steam are presented. In the temperature range 0-100cC the location of the inversion locus (mu) is defined for the first time with some precision. The low pressure steam results are re-correlated and a higher inversion temperature is indicated than that previously accepted. From 100 to 600°C values of viscosity are derived up to 3·5 kilobar and between 600 and 1500°C up to 1 kilobar. All the original observations in the gaseous phase have been corrected to a consistent set of densities and deviation plots for all the new correlations are given.

Although the equations give values within the tolerances of the International Skeleton Table it is clear that the range and tolerances of the latter could with some advantage be revised to give twice the existing temperature range and over 10 times the existing pressure range at low temperatures. A list of the observations used and their deviations from the correlating equations is available as a separate publication.
Approximate Analysis of the Large Deflection Elastic Behaviour of Clamped, Uniformly Loaded, Rectangular Plates
Authors: Hooke R.
Published: February 2007

An approximate analysis of the large deflection elastic behaviour of clamped, uniformly loaded, rectangular plates is carried out using a perturbation method. The solutions obtained are presented in a general form which allows the behaviour of a plate having any particular value of aspect ratio to be predicted. The predictions of the present solutions are compared with those of existing solutions where these are available.
Deadbeat Performance of Error-Sampled Feedback Time-Delayed Control Systems
Authors: Kevorkian A. K. , Soliman J. I.
Published: February 2007

In this paper the minimal overshoot and settling time of error-sampled feedback time-delayed control systems was carried out by incorporating a digital controller in the forward path of the control loop. Using the state-transition method the controller was designed by applying the variable-gain approach. The effect of parameter variation on the compensated response is also studied.
Large Deflections of Rectangular Plates Subjected to Uniform Lateral Pressure and Compressive Edge Loading
Authors: Brown J. C. , Harvey J. M.
Published: February 2007

A theoretical analysis is presented for the problem of flat rectangular plates undergoing large deflections due to the action of a uniform lateral pressure or combinations of uniform lateral pressure and compressive edge loading. The governing partial differential equations are replaced by their finite difference equivalents and the resulting difference equations solved by over-relaxation using an I.C.T. 1905 computer.

The results for plates subjected to lateral loads only are in good agreement with the few existing solutions. For plates subjected to lateral loads and combinations of lateral and edge loading, the results show good agreement with the results of an experimental programme carried out at the University of Strathclyde.
Shakedown Loads for Pressure Vessels of Strain Hardening Materials
Authors: Taylor T. E.
Published: February 2007

A power law, well known in creep analysis, embodies a family of curves which express the stress-strain relations for a family of materials ranging from linear elastic to rigid perfectly plastic. A linearization of the relationship between stress concentration factor and the reciprocal of strain hardening exponent for geometrically similar pressure vessels made of materials within the family has enabled a view of shakedown in vessels of strain hardening materials to be formulated. The absence of discontinuities in the power law, except at the rigid plastic end point, results in shakedown loads dependent on strain hardening exponent and previous loading history.
Effect of Hardness and Tensile Mean Stress on Fatigue Crack Growth in Beryllium Copper
Authors: Pook L. P.
Published: February 2007

Some fatigue crack growth data have been obtained for age-hardened beryllium copper. The fatigue crack growth rate was found to be very dependent on the hardness and tensile mean stress. This dependence is believed to be associated with the intense residual stresses surrounding Preston-Guinier zones.
Vibration of a Symmetric Tuning-Fork
Authors: Boocock D. , Maunder L.
Published: February 2007

The paper records an investigation of the vibration of a symmetric tuning-fork, with particular reference to the effects of the fork mounting. The relation between flexural vibration of the tines and longitudinal vibration of the fork as a whole is analysed in terms of the coupling induced by unbalanced inertia forces directed parallel to the axis of the stem. It is shown theoretically and confirmed experimentally that longitudinal oscillations can occur at fork frequency and twice fork frequency, and that the fundamental frequency of the fork is affected by the mounting characteristics if there is primary longitudinal unbalance. A method is described whereby the primary component of longitudinal unbalance may be eliminated.
Use of Large Plastic Beads to Follow Slow Flow of Water in a 7 Ft Diameter Vessel
Authors: Thew M. T. , Smith G. J.
Published: February 2007

To measure water velocities of the order of a few inches per minute in a 7 ft diameter vessel, half-inch diameter plastic beads were ballasted to be neutrally buoyant and after release at various points, photographed at intervals. Mismatching the coefficients of expansion of the plastic and water proved an unexpectedly serious problem, as did tiny air bubbles and solid particles adhering to the beads.
Vortex Shedding Frequencies of the Flow through Two-Row Banks of Tubes
Authors: Borges A. R. J.
Published: February 2007

This paper deals with the problem of vortex shedding from parallel rows of circular cylinders of equal diameter set normal to an airstream.

A single row of cylinders is first discussed. The experimental results show that when the lateral spacing between the axes of two adjacent cylinders is less than two diameters the flow downstream of the row does not exhibit any obvious single dominant frequency of vortex shedding.

The flow set up by two rows of cylinders is next considered for both tandem and staggered arrangements of the cylinders. The sets of measured values reported are complete in the sense that they cover the whole range of spacings for which a dominant frequency of vortex shedding could be measured.

The Reynolds numbers of these tests correspond to the high subscritical range for a cylinder in isolation.
Effect of Upstream Velocity Profiles on Turbine Flowmeter Registration
Authors: Jepson P. , Bean P. G.
Published: February 2007

A theoretical model is derived which shows that flow measurement errors of up to 5 per cent can result if turbine flowmeters are subjected to changes in upstream velocity profiles. This theory is then used to show how proper meter design can considerably reduce these errors. Experiments in a 50·8 mm (2 inch) diameter pipe, with water as the working fluid, were made to confirm the model and the suggested design improvements. The test results show good correlation with theory.
Damping Inserts in Vibrating Structures
Authors: Wolfe C. J. , Woods C. J. , Andrew C.
Published: February 2007

A method is presented for the prediction of the response of a vibrating system after the introduction of a damping insert between two distinct co-ordinates of the system, and procedures are given for the optimization of such inserts. The method can be extended to predict the effect of breaking the system and introducing a damping insert into the break, and may utilize the experimentally measured characteristics of both the original system and the damping insert.

Butyl rubber inserts are found to reduce vibration amplitudes of models of typical engineering structures by as much as a factor of 4.
Methods of Using a Vibratory System to Measure Small Rates of Turn
Authors: Linnett J. A.
Published: February 2007

The equations of motion for a vibratory two-degrees-of-freedom spring mass system subjected to rotation about an axis perpendicular to its plane of vibration are considered, taking into account the various couplings that may be present. The rate of turn can be measured by three alternative methods, two of which involve an exciting force in the sensing direction in addition to the one vibrating the system. The shape of the phase angle against angular velocity curve is shown to be independent of damping, enabling the transient performance to be improved without affecting the sensitivity of the device.

Experimental work shows good agreement with the developed theory.
Influence of Asperity Deformation Mode on Gas Leakage between Contacting Surfaces
Authors: Mitchell L. A. , Rowe M. D.
Published: February 2007

The gas flow between two surfaces in contact is affected by the way in which the surface asperities are deformed by the contact load. The plastic deformation of wedge-shaped model asperities, supported on rigid bases, is examined. Full account is taken of the effect of displaced material on the deformation pressure and on the rate of fluid leakage between the contacting surfaces. Characteristics of deformation pressure versus compression are plotted for a range of wedge asperity angles, assuming two-dimensional deformation and non-hardening material, and from these are derived expressions for fluid leakage between the contacting surfaces. It is shown that a critical contact pressure exists for a given seal contact load at which the leakage rate has a maximum value. This contact pressure may be avoided by either increasing or decreasing the seal length.
Steady-State Motion of Railway Vehicles on Curved Track
Authors: Boocock D.
Published: February 2007

A simplified linear theory of steady-state curve traversing is developed for bogie and two-axled vehicles. The approach is based on providing guidance by creep forces in conjunction with wheel conicity, so that flange contact is normally avoided. It is shown that this approach is realistic for a wide range of vehicle and track parameters. However, steering by creep forces is limited by the onset of wheel slip. Representative experimental results for a two-axled vehicle are presented.
Experimental Investigation of the Energy Separation in Vortex Tubes
Authors: Bruun H. H.
Published: February 2007

Measurements of the state and the velocity distribution of air in a counterflow vortex tube have been undertaken. In order to determine the axial variation of the flow quantities, measurements were carried out in several cross-sections.

The experimental results show that the velocity is predominantly tangential. A comparison of the order of magnitude of the radial and axial convection terms in the equations of motion and energy shows that these terms are of equal importance.

The energy equation in terms of the total temperature is used as a basis for discussing the influence of turbulence in the flow on the separation of energy in the vortex tube.
Ultraharmonic Resonance of a System with an Asymmetrical Restoring Force Characteristic
Authors: Carnegie W. , Reif Z. F.
Published: February 2007

The ultraharmonic resonance of order 2, excited by a centrifugal type disturbing force, is investigated for a single-degree-of-freedom system with a Duffing restoring force characteristic. The effect of gravity is taken into account. The resulting asymmetry of the restoring force is expressed in terms of the static deflection parameter. The Ritz averaging method is used for the theoretical analysis and the results are verified by means of an analogue computer.
Creep and Wear Due to Microslip in Conforming Rolling Contacts
Authors: Hailing J. , Al-Qishtaini M. A.
Published: February 2007

The paper presents experimental results for the creep and wear due to microslip under dry rolling contact conditions. Creep results show good correlation with the strip theory predictions for conforming geometric contacts. The wear effects of increasing the tangential traction on plane rolling contacts are explained using an incremental wear law related to the square of both the local pressure and the local slip velocity. Various degrees of geometric conformity are examined and support the theoretical arguments for the minimum wear conditions associated with any particular loading in terms of a prescribed geometric conformity.
Regimes of Elastohydrodynamic Lubrication
Authors: Johnson K. L.
Published: February 2007

The different regimes of behaviour in the elastohydrodynamic lubrication of rollers are displayed on a chart whose rectangular co-ordinates express the influence of elasticity of the solids and variation of viscosity of the lubricant with pressure respectively. At small values of these co-ordinates, i.e. at a very light load, the behaviour is effectively rigidisoviscous. At high loads the relative importance of elastic deformation and variable viscosity is shown to depend upon a single parameter suggested by Archard. Approximate boundaries for the various regimes are suggested. Using the computer solutions which are available, the variations in film thickness and pressure distribution in the different regimes are examined.
Fatigue and Cyclic Thermal Softening of Thermoplastics
Authors: Constable I. , Williams J. G. , Burns D. J.
Published: February 2007

Thermoplastic components subjected to cyclic loading may distort because of localized rises in temperature and/or fracture because of incremental (fatigue) crack propagation from microscopic cracks or defects produced during the manufacturing process or by service conditions.

The object of the present paper is to show quantitatively how the first mode of failure, which is referred to as cyclic thermal softening, can be related to loss compliance, specimen geometry and the frequency and magnitude of the cyclic load. The results of cyclic bending tests on polymethylmethacrylate (p.m.m.a.) and Polyvinylchloride (p.v.c.) beams of rectangular and circular cross-section are analysed. For the service conditions considered the p.m.m.a. specimens showed both failure modes whereas the p.v.c. specimens failed as a result of incremental (fatigue) crack propagation.
Selective Withdrawal of Stratified Fluids through Vertical Intakes
Authors: Barnard B. J. S. , Northridge R.
Published: February 2007

The withdrawal of stably stratified fluids through a vertical intake terminating inside one layer is considered. A theoretical limit is obtained for the withdrawal rate at which nearby layers are entrained in the presence of interfacial waves. Experiments are described using circular and rectangular intakes which are in reasonable agreement with the theory.
Dynamics of Tubular Cantilevers Conveying Fluid
Authors: Paidoussis M. P.
Published: February 2007

In Part 1 a general theory is presented to account for the small, free, lateral motions of a vertical, uniform, tubular cantilever conveying fluid, with the free end being either below the clamped one (‘hanging’ cantilever) or above it (‘standing’ cantilever). Gravity forces are not considered to be negligible.

It is shown that, when the velocity of the fluid exceeds a certain value, the cantilever in all cases becomes subject to oscillatory instability. In the case of hanging cantilevers buckling instability does not occur. Standing cantilevers, on the other hand, may buckle under their own weight; it is shown that in some cases flow (within a certain range of flow velocities) may render stable a system which would buckle in the absence of flow.

Extensive complex frequency calculations were conducted to illuminate the dynamical behaviour of the system with increasing flow. The conditions of stability have also been extensively calculated and stability maps constructed. It is shown that dissipative forces may have either a stabilizing or a destabilizing effect on the system, partly depending on the magnitude of these forces themselves.

The experiments described in Part 2 were designed to illustrate the dynamical behaviour of vertical tubular cantilevers conveying fluid. The experiments were conducted with rubber tubes conveying either water or air. The tubes were either hanging down or standing upright.

It was observed that for sufficiently high flow velocities both hanging and standing cantilevers become subject to oscillatory instability. It was also observed that standing cantilevers which would buckle under their own weight in the absence of flow, in some cases are rendered stable by flow within a certain range of flow velocities. Qualitative and quantitative agreement between theory and experiment was satisfactorily good.
Theoretical Analysis of Externally Pressurized Air Journal Bearing
Authors: Majumdar B. C.
Published: February 2007

A theoretical investigation is made to predict the performance of an externally pressurized air journal bearing having several pressure sources. The pressure distribution, which leads to the determination of load-carrying capacity and flow requirement, is obtained by solving Reynolds equation numerically. The load and flow, expressed in non-dimensional parameters, are presented for different bearing design parameters (dimensionless). The results predicted by this method are compared with others' experimental data.
Absolute Viscosity of CCl2F2 and CHCl2F
Authors: Latto B. , Al-Saloum A. J.
Published: February 2007

The absolute viscosity at atmospheric pressure was determined experimentally for the vapour phase of two halogenated hydrocarbon compounds, refrigerants R12 (CCl2F2) and R22 (CHCl2F) in the general temperature range −39·7° to 91·8°C.

The maximum error of the data is believed to be ±3 per cent. Comparison with previous secondary measurements on the same compounds reveals that the maximum deviation of previous measurements are +5 per cent and −6 per cent for R12 and R22, respectively, over the common temperature range.

The data obtained in this work and by others were correlated using third and fourth degree polynomials, a power function of the absolute temperature, and a collision theory approach, which yielded values for the reduced dipole energy, the velocity collision diameter, and the maximum energy of attraction for the molecules. Comparison of the data with that predicted by simple kinetic theory has been made.
A Six Component Dynamometer
Authors: Smith J. D. , Welbourn D. B.
Published: February 2007

The design of an extremely simple, cheap, six component dynamometer is described. It was originally designed for use on gear cutting machinery but is now used for many other purposes. The characteristics have been estimated and the test results are as expected. Its versatility is such that different versions can measure from ounces to hundreds of tons, and it supersedes all other designs for the majority of machining force measurements.
Stability of Multirecess Hydrostatic Journal Bearings
Authors: Davies P. B. , Leonard R.
Published: February 2007

An analysis which predicts that multirecess hydrostatic journal bearings exhibit dynamic instability at and above a certain speed of shaft rotation is summarized. This instability is characterized by the centre of the shaft exercising vibrations in a closed orbit of high eccentricity at a frequency equal to one half of the critical shaft speed. Futhermore, this frequency corresponds to the natural frequency of the system at zero eccentricity in the absence of shaft rotation. An expression for the critical speed of an orifice compensated bearing with four recesses is given and an experimental verification of these predictions is presented.
Influence of Film Inlet Conditions on the Performance of Fluid Film Bearings
Authors: Neal P. B.
Published: February 2007

In fluid film bearings it is difficult to ensure that lubricant which has once traversed the length of the film is not immediately reintroduced at the entry end of the film. The ability of cooler feed oil to be drawn into the film is controlled by the viscosity of the hot carryover oil adhering to the runner or journal surface. A modified Reynolds equation is derived which incorporates a variation of viscosity through the thickness of the film. Application of this modified equation to the case of a square taper-film pad shows that variation of viscosity through the film thickness at film entry can have a very significant effect upon the operating conditions of a bearing.
An Elasto-Plasto-Hydrodynamic Lubrication Analysis of the Plane Strain Drawing Process
Authors: Bloor Susan M. , Dowson D. , Parsons B.
Published: February 2007

In recent years there has been an accumulation of evidence of hydrodynamic lubrication in various metal forming processes. In the present paper the possibility of hydrodynamic action in the plane strain drawing process is explored in a theoretical analysis which takes account of the variation of lubricant viscosity with pressure and temperature and elastic and plastic deformation of the strip. The generation of heat within the lubricant is considered and linear heat flow in the rigid die is considered in the thermal analysis.

In previous theoretical studies a rigid-plastic model has been adopted for the worked material, but in this analysis the influence of elastic deformation in the entry zone and elastic recovery at outlet is examined. The procedure applies the methods of elastohydrodynamic lubrication analysis to a situation in which the elastic distortion is followed by plastic flow. The term elasto-plasto-hydrodynamic lubrication is introduced to describe this situation.

Results of the analysis are presented in the form of pressure and temperature distributions and film profiles. It is shown that hydrodynamic films of significant proportions can be developed under some conditions.
Communication on the Invalid Use of an Isentropic Expansion Index for Wet Steam
Authors: Ryley D. J.
Published: February 2007

Steam expanding within the nominal mixed phase (liquid-vapour) region invariably supersaturates whatever its initial condition. The use of the Zeuner equation γ = 1·035 + x1/10, based upon equilibrium expansion, is therefore invalid and should be discontinued.
Dynamic Viscosity of Water at Temperatures below 0°C
Authors: Bruges E. A. , Gibson M. R.
Published: February 2007

The probable behaviour of the viscosity of compressed liquid water in the vicinity of the solid-liquid boundary has been derived by extrapolation of an existing equation.
Effect of Gravity on the Performance of an Impact Damper: Part 1. Steady-State Motion
Authors: Sadek M. M. , Mills B.
Published: February 2007

This paper, which examines the effect of gravity on the performance of an impact der, extends a previous paper (I)‡ concerned with the horizontal system. The analysis is in two parts: Part 1 which concerns itself with the calculation of all the theoretically possible steady-state motions with two impacts of the free mass, one at each end of its container, per cycle of the main mass; and Part 2§ which examines the dynamic stability and kinematic viability of the various steady-state solutions obtained in Part 1.

The impact damper consists of a small mass free to move within a rigid container attached to the main vibrating system. Vibration suppression is achieved through energy dissipation during impacts and through cancellation of the effect of the external exciting force by the cyclical reaction of the free mass on the main system.

The analysis shows that, in general, several different steady-state motions are theoretically possible for a given exciting frequency and that the effect of gravity on the motion of the system is to reduce the frequency range of two-impact-per-cycle motion. It is also shown that under the practically important condition of resonance the motion consists of two impacts of the free mass per cycle of the main mass. Outside the resonant condition, where the motion of the main mass is weak, the free mass may impact more or less than twice per cycle. This condition is not studied.
Articulated Models of Cantilevers Conveying Fluid: The Study of a Paradox
Authors: Paidoussis M. P. , Deksnis E. B.
Published: February 2007

A general theory is presented for the dynamics of nth-degree-of-freedom articulated (lumped flexibility) models of cantilevers conveying fluid, of which the two-degree-of-freedom model of a column subjected to follower forces (first investigated by Ziegler) is a particular case. The ability of the articulated system to predict the dynamical behaviour of the continuous system modelled is investigated, and in particular the paradox that, whereas the continuous system is subject to only oscillatory instability (at sufficiently high flow), the model is generally subject to both oscillatory and buckling instabilities, and sometimes only to the latter. Complex frequency calculations show that buckling is associated with the higher modes of the articulated system, which, irrespective of the number of degrees of freedom, do not model well the corresponding modes of the continuous system. The critical flow velocities for buckling and oscillatory instabilities are calculated extensively, the latter showing good convergence to the corresponding values of the continuous system. The theory is supported by a set of experiments. Agreement between theory and experiment is satisfactorily good.
Laboratory Scale Experiments into Cavity and Crater Formation by High Explosive Charges
Authors: Lynch J. , Hawkyard J. B. , Johnson W.
Published: February 2007

A Plasticine block is used to represent a semi-infinite solid, for the investigation of camouflet and crater formation by high explosive charges. The Plasticine model is 90 cm diameter and 60 cm deep and the explosive charges vary between about 0·1 g and 0·8 g, producing cavities and craters in the region of 2 cm to 5 cm radius. The shapes of the craters and cavities and the final surface contours are measured and compared with theoretical forms determined from a simple theory. Comparison is also made with the results of large scale nuclear and high explosive operations.
An Experimental Investigation of the Natural Convection of a Heat Generating Fluid within a Closed Vertical Cylinder
Authors: Murgatroyd W. , Watson A.
Published: February 2007

Experimental results are presented of the velocity and temperature distributions within a heat-generating fluid contained in a vertical closed cylinder, for the case in which the outer surface of the cylinder wall is maintained at a uniform temperature. Previous experimental data are compared and an earlier theoretical model for a different thermal boundary condition is reinterpreted for the present case.
Instability of an Elastically Supported Beam under a Travelling Inertia Load
Authors: Newland D. E.
Published: February 2007

It is shown that an unstable bending wave may be excited in an elastically supported beam by a travelling inertia load. Since the occurrence of this dynamic instability reduces the axial buckling load of the beam, the result is relevant to present studies of the temperature buckling of continuous welded railway track.
Velocity Distribution in Turbulent Flow
Authors: Allan W. K.
Published: February 2007

A general equation for the velocity distribution in steady, incompressible, two-dimensional, turbulent flow is constructed by correction of the logarithmic velocity profile for the independent effects of pressure gradients and of surface roughness. Predicted characteristics of pipe flows, flat plate flows, and diffusing flows over smooth surfaces are found to be in good agreement with empirical data at high Reynolds numbers. Pipe flow data are used to evaluate surface roughness effects, and hence to describe flat plate flows and diffusing flows over rough surfaces.
Prediction of Wall-Jet and Wall-Wake Flows
Authors: Kacker S. C. , Whitelaw J. H.
Published: February 2007

An existing numerical procedure for solving the steady, two-dimensional, constant property form of the Navier–Stokes equations, has been used to obtain predictions of mean and fluctuating properties downstream of a two-dimensional wall jet. The Prandtl–Kolmogorov model of turbulence, with a simple empirical expression for the length scale, is shown to permit satisfactory predictions over a wide range of flow situations. These flow situations are relevant to the design of film-cooling slots.
An Aid to Practical Sheet Metal Forming
Authors: Pearce R. , Woodthorpe J.
Published: February 2007

Until recently, no analytical technique was available for the study of failure in complex sheet metal pressing. However, if the maximum ( e1) and minimum ( e2) principal surface strains at failure on sheet metal pressing are measured, a plot of e1 against e2 results in a so-called forming limit diagram. FLD can be constructed in the laboratory and used as an aid to die try-out, production failures and metal specification.
Some Non-Linear Effects in the Vibration of a Four-Bar Linkage
Authors: Gayfer J. R. , Mills B.
Published: February 2007

The non-linear effects which are examined are those arising from the changes of linkage geometry during the course of the motion. The fundamental frequency of a linkage with rigid members controlled by discrete, linear torsion springs is analysed and solutions offered in terms of phase plane and energy methods, together with an approximate closed solution in the form of a harmonic series with terms in sin (2 n + 1)ω t and cos 2 nω t. Experimental results are presented for free and forced motions which, with one exception, agree well with the theoretical predictions of the energy and series solutions.

In Appendix 1 a (velocity)2 term appearing in the series solution is shown to be a conservative, soft spring effect arising from apparently variable inertia.
Experimental Investigation into the Effects of Indenting a Cylindrical Shell by a Load Applied through a Rigid Boss
Authors: Morris A. J.
Published: February 2007

A series of tests has been performed on thin unpressurized cylinders loaded by two equal and opposite forces applied across a diameter. Special emphasis was laid on elucidating the response of the specimens to large displacements in order to check the possible appearance of any snapping action.

Tests were performed on cylinders both with and without edge constraints and the experimental procedure was devised in order to isolate, as far as possible, the effects of plastic strains.

No actual strains were measured and the results presented all correlate the variation of displacements with variations in the applied loads.
Fatigue Crack Propagation in Polymethylmethacrylate; the Effect of the Mean Value of Stress Intensity Factor
Authors: Arad S. , Radon J. C. , Culver L. E.
Published: February 2007

Polymeric components often contain structural defects which give rise to regions of internal stress concentration. As the engineering application of these materials expands, the need to understand their behaviour under various loading conditions becomes more necessary.

This paper reports the results of part of a programme of research undertaken to study fatigue crack propagation phenomena in thermoplastics.

A fracture mechanics approach is used and the effects of the mean stress intensity factor, Km, and the range of stress intensity factor, ΔK, on crack propagation phenomena in polymethylmethacrylate are studied.

Based on the experimental data available, a relationship of the following form, between the cyclic crack growth rate d(2 a)/d N and the tensile loading levels, has been proposed d(2 a)/d N = β( Kmax2 – Kmin2) n

where Kmax and Kmin are the maximum and minimum values of the stress intensity factor in each loading cycle. In tests at room temperature (21°C), in air, at a loading frequency of 5 Hz, n was found to be equal to 2·5; log β equalled —12·37.
The Energy Required for High-Speed Shearing of Steel
Authors: Stock T. A. C. , Wingrove A. L.
Published: February 2007

Some results are presented relating to the effects of shearing velocity on the energy required for shearing of both high and low carbon steels. Analyses of these results suggest an explanation of some of the apparently contradictory findings of other workers. The results obtained may be explained in terms of the relative imbalance between plastic softening due to adiabatic heating and increase in flow stress due to strain and strain rate.
Graphical Interpretation of the Levy-Mises Relations
Authors: Agnew P. W.
Published: February 2007

This note describes a simple graphical method of calculating the principal stress differences corresponding to a given sequence of deformations.
Theoretical and Practical Aspects of the Application of Resonant Combustion Chambers in Gas Turbines
Authors: Muller J. L.
Published: February 2007

This paper discusses theoretical and experimental work carried out to determine the feasibility of a pressure-gain combustion system for gas turbines.

Fundamental principles involved in the design of resonant combustors are considered and potential improvements in gas turbine performance are calculated by means of a piston-cylinder analogy. The results indicate that significant improvements in overall thermal efficiency and specific power output can be expected at relatively low pressure ratios but that these improvements become less effective at higher pressure ratios due to the influence of increased compressor delivery temperatures.

The results of experimental work on a multiple combustor configuration show that the theoretical performance appears to be attainable and that, subject to further development work, resonant combustion chambers could be utilized to improve gas turbine performance.
A Proposal for Improving the Performance of a Two-Axle Rail-Guided Vehicle
Authors: Benington C. K. , Greenhorn J. W. R.
Published: February 2007

In a recent paper (I)‡ it was shown how the dynamic behaviour of a conventional, single, elastically restrained railway wheelset could be improved by replacing the rigid torsional coupling between the wheels with a coupling which had variable viscous characteristics. The consequences of fitting these damper-coupled wheelsets to a two-axle vehicle are now examined theoretically. Analysis of the simplest mathematical model reveals that the basic obstacles to correspondingly improved behaviour of the complete vehicle are very similar to those which confront the suspension designer of a conventional vehicle, and yield, in principle, to the same approach that has been adopted in relation to these vehicles elsewhere. As a result, the improvement in dynamic performance obtained with the single damper-coupled wheelset may apply equally to a two-axle vehicle which has these wheelsets.
The Ultracentrifuge Separation of Heavy Isotopes
Authors: Theyse F. H.
Published: February 2007

The fundamental equations describing the physical principles that underly the ultra-centrifuge isotope separation process are outlined leading to a description of the engineering problems encountered in their realization.
Transient Effects in the Lubrication of Hertzian Contacts
Authors: Vichard J. P.
Published: February 2007

Analysis of the lubrication of mechanisms such as gears, roller bearings and cams shows that their contacts involve a squeeze effect when they operate. The classical approach, however, is to limit investigations to steady state conditions. The aim of our work is to estimate the validity of this hypothesis. First, we shall examine the behaviour of contacts with rigid surfaces and we shall compare the results with the Martin theory. The straightforwardness of the derivation of the Reynolds equation allows us to study the effect thoroughly. The squeeze effect contributes to damp down the variations of the external parameters, such as load or speed. Secondly, this result is confirmed in elasto-hydrodynamic theory. In this case the exact calculation is too complicated and we have used the Grubin's approximation. Finally, an experimental study will confirm the theoretical results and will show a phenomenon which has a thermal origin.
The Behaviour of Nucleation Fogs within the Nozzle Boundary Layer in the Wet Steam Turbine
Authors: Ryley D. J.
Published: February 2007

At low pressures the boundary layer within a turbine blade passage carrying a nucleation fog is very sparsely populated with droplets and its hydrodynamic behaviour is not materially influenced by their presence.

The rate of energy dissipation within the boundary layer is only sufficient to evaporate a very small fraction of the total liquid entrained in the layer; nevertheless, superheat due to temperature recovery is almost completely suppressed by this evaporation.

Thermal coagulation is active within the layer and gradient coagulation is very significant when the droplets are large. Any valid theory of deposition by diffusion must recognize this fact. Calculations were made for the concave surface of a typical low pressure turbine blade and boundary layer properties of interest are displayed.
Experimental Investigation of Non-Linear Coupled Vibrations in Elastic Columns Excited at High Frequencies
Authors: Ramsey H. , Johnson D. , Hazell C. R.
Published: February 2007

Contributions intended for publication as Research Notes should be limited in length to 1000 words and two illustrations, and should be addressed to the Editor of Proceedings at the Institution Headquarters in London.

Coupling of flexual and longitudinal vibration modes has been observed experimentally in a slender column of rectangular cross-section subjected to periodic axial loading at frequencies up to 10 kHz; the fundamental longitudinal frequency of the specimen is 8·7 kHz. Resonance in the coupled flexural–longitudinal modes was observed when the frequency of axial excitation was 1, ½, and ⅓ times the fundamental longitudinal frequency. Strain levels at resonance in the coupled modes were comparable to strain levels in the purely flexural modes which were excited when the frequency of axial excitation corresponded to a flexural mode.
Unsteady Flow through a Four-Way Branch in the Exhaust System of a Multi-Cylinder Engine
Authors: Daneshyar H. , Pearson R. D.
Published: February 2007

This paper is concerned with the investigation of unsteady flow through a four-way branch, with particular reference to its application to flow in the exhaust system of a multi-cylinder engine. The only methods of solution hitherto available are for unsteady flow through a three-way branch. The potentially most accurate theory of those reported takes pressure and entropy changes at the junction into account, but cannot be used in practice since the iterative processes employed in this method often become divergent (I)‡. A convergent method of solution has therefore been developed and is utilized to study the unsteady flow through a four-way branch, making the usual assumption of quasi-steady flow at the junction.

A general computer programme for multi-cylinder engines combining the programmes for the cylinder boundary, for the nozzle boundary, for unsteady flow in the pipes, and the present method for branched systems has been developed (in Algol code) to compute the flow variables (pressure, velocity, and temperature) in the exhaust system and cylinders. The temperature variations which can arise in an engine are fully taken into account.

Experimental data are presented for both steady and unsteady flow conditions. The steady data have been used to supply the pressure coefficients needed for full computation in the non-steady flow case. Simpler theories involving assumed pressure coefficients are also employed in shorter programmes which yield acceptable results of lower accuracy. Consequently, it appears that prediction can now be made to sufficient accuracy, in the range of pressure amplitudes and Mach numbers investigated, without the need for comprehensive steady flow testing.
Receptances of Lumped-Parameter Systems Containing Discrete Damping Sources
Authors: Hammill W. J. , Andrew C.
Published: February 2007

This paper describes a combined eigenvalue and frequency response method for predicting the vibration characteristics, and particularly the receptances, of a system containing discrete sources of damping. This system typifies heavily damped engineering structures, like those of machine tools, and represents structures which have had damping introduced in the form of inserts. A simple model structure was used to demonstrate the application of the method.
An Exact Solution to the Variation in Force along Rotating Springs
Authors: Gillespie S. J.
Published: February 2007

An exact solution to end reactions of a close coiled helical spring rotating about an axis perpendicular to that of the spring is shown. The solution allows for the general case of a spring initially offset longitudinally to the centre of rotation but restrained against bowing.

The solution requires knowledge of spring dimensions and free and installed length.