bluuebunny/crossref_metadata_2025_split huggingface dataset:
Base Pressure and Noise Produced by the Abrupt Expansion of Air in a Cylindrical Duct
Authors: Anderson J. S. , Williams T. J. 
Published: February 2007

In the investigation described, the base pressure resulting from the abrupt expansion of an air jet from a circular nozzle into a concentric cylindrical duct or shroud has been measured. Stagnation pressure ratios of the forcing jet to atmospheric of up to six were used with shrouds of various lengths and diameters. As the primary or forcing jet pressure is increased and then decreased, the jet flow attaches and separates from the shroud wall and a hysteresis effect is exhibited by the pressure at the base of the shroud. With an attached flow, the base pressure attains a minimum value which depends mainly on the duct to nozzle area ratio and on the geometry of the nozzle, lower base pressures being obtained with convergent-divergent nozzles. When the jet pressure was increased beyond that required to attain the minimum value of the base pressure, it was observed that the ratio of the forcing jet pressure to base pressure remained constant. Noise measurements of the flow from the nozzle and shroud are presented. The plot of overall noise showed a minimum value of noise at a jet pressure approximately equal to that required to produce the minimum base pressure. As the pressure was increased beyond this value, the noise from the shroud was essentially that of a subsonic jet until the flow at the shroud exit became choked. The excessive overall noise observed at low forcing pressures was due to the emission of powerful discrete tones from an organ-pipe resonance within the ducts.
Plastic Behaviour of Thin Cylindrical Pressure Vessels with Circular Cutouts and Radial Branches
Authors: Calladine C. R. , Goodall I. W. 
Published: February 2007

Pressure tests were performed on four thin cylindrical aluminium vessels with circular cutouts and cover plates, and on two vessels with radial branches. In all cases a fairly well defined ‘limit pressure’ was observed—corresponding to plastic deformation in the vicinity of the cutout or branch—together with a moderate increase in pressure as deformation proceeded, which may be interpreted as a moderately strong ‘geometry-change effect’. The limit pressures observed for vessels with cutouts agree well with a lower-bound analysis which is described in outline. In general the observed limit pressures fit in well with those observed by other workers for vessels of different proportions. Correlation of geometry-change effects is not so simple, but a fairly clear picture of trends emerges from the study. The question of appropriate geometrical parameters for correlation of results is discussed, and a suggestion is made for taking into account any ‘extra’ cross-sectional area at the junction weld.
Transient Thermal Stresses in Elasto-Plastic Discs
Authors: Odenö H. 
Published: February 2007

A thin circular disc of elastic-perfectly plastic material, subjected to an axially symmetric transient temperature distribution, is treated analytically. All material parameters are assumed to be independent of the temperature. Poisson's ratio is taken to be one-half. The Tresca yield condition with associated flow rule is employed. The temperature distribution is that which appears when the outer rim surface of the disc receives a rapid temperature increase and it is solved approximately by the collocation method. The analysis shows that under certain circumstances, plastic deformation will occur in a moving annular region. This region starts to develop at the exterior surface and moves inward, while changing its width. After a certain finite time its width shrinks to zero. Except for a residual constant state of strain, the strain field is then again elastic. An application to the method of separating the ring and the shaft in a shrink-fit is carried out numerically. The residual stresses in the ring are calculated.
Narrow Band Random Fatigue Testing with Amsler Vibrophore Machines
Authors: White D. J. , Lewszuk J. 
Published: February 2007

A description is given of modifications made to Amsler Vibrophore machines to permit narrow band random fatigue tests to be made. In this mode of working, the machine electromagnet is excited by means of a random generator and a complete control loop is effected by connecting the output of the inductive transducer of the machine dynamometer to the automatic output regulator (compressor circuit) of the random generator. The dynamometer was strain-gauged and calibrated to read r.m.s. load. Under compressor circuit control, the stress peaks in a specimen followed the Rayleigh distribution at least up to four times the r.m.s. value. As in constant amplitude sinusoidal loading, these machines are capable of applying mean stress when working in random loading. Some practically occurring stress spectra may be synthesized by applying sequences consisting of a number of stepped r.m.s. loads, each step being applied for a predetermined time.
Fully Developed Heat Transfer to a Gaseous Suspension of Particles Flowing Turbulently in Ducts of Different Size
Authors: Boothroyd R. G. , Haque H. 
Published: February 2007

This paper is a sequel to two earlier studies of friction (I)† and eddy diffusion (2) carried out for the same flow conditions as in the present study of heat transfer. Heat was transferred to an upward flowing suspension of 0-40 μ zinc particles in pipes of 1, 2 and 3 in bore. The solids/gas flow rate was in the range 0 < Ws/ W g< 17 and the pipe Reynolds number in the range 3·5 × 104< Re < 105. It was found that the fractional increase in heat transfer coefficient due to the presence of solids was always less than the increase in the friction factor. Minimum values of both these parameters are often observed in the range 1 < W s/ W q< 2·5. This paper gives further evidence that turbulence is suppressed by the particles, particularly when the duct is small and Re is large; in this case the wall Nusselt number, Nu s, is markedly reduced below the value when gas flows alone. However, when the pipe is large and Re is low, Nu s can be substantially higher than the value for gas alone. In this case the suspension is a superior coolant to the flow of gas alone.
Empirically Determined Model for Polarized Relays
Authors: Barnes R. N. , Burrows C. R. 
Published: February 2007

Theoretical determination of a mathematical model to describe a polarized relay requires knowledge of the relay characteristics, i.e. the inductance, resistance and armature dynamics. Unless the data are supplied by the manufacturer determination of the characteristics is time-consuming and may present problems, especially if the inductance is required at low frequencies. A technique is presented here which overcomes measurement difficulties at low frequency and allows an approximate model to be rapidly determined.
A Heat-Mass Transfer Analogy Applied to Fully Developed Turbulent Flow in an Annulus
Authors: Lewis J. S. 
Published: February 2007

A heat-mass transfer analogy based on the ‘universal’ velocity profile applied to an annulus is compared with analogy values based on similar but more sophisticated expressions for the eddy diffusivity and hence velocity profile. The difference between these analogy values and those of Chilton and Colburn (I)† are noted to be appreciable and to increase with increasing Reynolds number. Heat transfer predictions from mass transfer measurements using ‘universal’ velocity profile type analogies are compared with established results. Friction factor measurements were made and found to be up to 10 per cent higher than the values for flow in a round tube at the corresponding Reynolds number.
Elastohydrodynamic Lubrication of Soft, Highly Deformed Contacts
Authors: Hooke C. J. , O'Donoghue J. P. 
Published: February 2007

Part 1 presents a theoretical solution to the problem of lubrication of soft, highly deformed surfaces. It is argued that with this type of contact the inlet and outlet regions can be separated and analysed independently. This approach leads to a single value of non-dimensional film thickness at the point of maximum contact pressure and to a non-dimensional minimum film thickness dependent on the relationship between the inlet and outlet parameters. In Part 2, these results are applied to the problems of a cylinder sliding on an elastomer lined surface, an elastomer lined journal bearing and a sliding O-ring seal.
Dynamic Analysis of Axially Non-Uniform Thin Cylindrical Shells
Authors: Lakis A. A. , Paidoussis M. P. 
Published: February 2007

Part 1 of this paper presents a new theory for the dynamic and static analysis of axially non-uniform, thin cylindrical shells. It is a hybrid of finite element and classical shell theories: the shell is subdivided into cylindrical finite elements, and the displacements within each (expressed in terms of nodal displacements), i.e., the displacement functions, are obtained using Sanders' equations for thin cylindrical shells in full. Sanders' theory gives zero strains for small rigid-body motions, so that displacement functions based on it satisfy the convergence criteria of the finite-element method. Expressions for the mass, stiffness and stress-resultant matrices are obtained, and the method for constructing the equivalent global matrices is given. This paper is supported by Part 2, where the eigenvalues of a number of shells are calculated and compared with other theories and experiments. In Part 2, the free flexural vibration characteristics of thin cylindrical shells are studied by this new, hybrid finite-element theory, where the displacement functions are determined by solution of the cylindrical thin-shell equations. Uniform shells with simply-supported, clamped and free ends are studied, as well as ring-stiffened shells and shells with thickness discontinuities. The frequencies of vibration are compared with those obtained by other theories and with the experiments of others. Agreement with other theories is good and, in the majority of cases, is even better with the experiments.
The Effect of Centrifugal Stretching in High-Speed, Self-Acting Gas Bearings Operating under Steady-State Conditions
Authors: Sadek K. S. H. , Cole B. N. , Dowson D. 
Published: February 2007

The study reported in this paper arose from an investigation of methods of achieving oil-free compression of refrigerant vapours. One part of the investigation included a feasibility study of a high-speed rotary machine running in self-acting gas bearings lubricated by the refrigerant. In certain designs of very high-speed rotor-bearing arrangements, centrifugal or radial growth of the journal might disturb the shape and magnitude of the nominal clearance space and thus affect the performance characteristics of the bearing. The nature and magnitude of these changes in bearing performance for uniform and for two forms of non-uniform centrifugal growth have been examined theoretically. Typical gas-film pressure distributions are presented together with design charts showing how attitude angle and load carrying capacity vary with speed. Comparisons are made with the performance of bearings having the same eccentricity ratio on the mid-plane, and guidance is given on the calculation of uniform radial growth at high speeds. It is concluded that changes in lubricating film geometry resulting from centrigual stretching might have a significant effect upon the performance of certain high-speed, self-acting gas-lubricated bearings.
A Critical Review of the Theorems of Thermodynamic Availability, with Concise Formulations
Authors: Haywood R. W. 
Published: February 2007

In this review, which includes some new material, the terms ‘availability’ and ‘irreversibility’ are used to denote certain concepts, their alternative use to denote certain physical quantities being avoided. The review commences with careful definition of the physical quantities, concepts and terms involved in the study, before proceeding to the formulation and proof of seven Theorems, three of which are treated in Part 1. The remainder of this part of the paper is devoted to the detailed evaluation of reversible work quantities, dealing specifically with such terms as available energy, free energy, exergy, anergy and essergy. Part 2 (which will appear in the next issue) will be concerned principally with the evaluation of lost work output (or extra work input) due to irreversibility, while a critical, historical review will be presented in an Appendix.
Laminar Heat Transfer in Rotating Eccentric Annuli
Authors: Launder B. E. , Ying W. M. 
Published: February 2007

The paper presents numerical solutions to the problem of laminar heat transfer in eccentric annuli with the inner cylinder rotating. The method of solution is based on the general finite-difference procedure for solving elliptic partial differential equations developed by Gosman et al.(1)‡. The solutions show that, for an eccentricity of 0.5, even modest levels of swirl greatly reduce the large circumferential variation in Nusselt number that is present without swirl. Moreover rotation appears to offer a particularly effective way of increasing the level of heat transfer since, for a Prandtl number of 0.7, the Nusselt number is raised by twice as much as the friction factor.
Theoretical Studies of Tip Clearance and Radial Variation of Blade Loading on the Operation of Ducted Fans and Propellers
Authors: Gibson I. S. 
Published: February 2007

Actuator disc theory and surface singularity techniques are applied to the performance of ducted fans and propellers, with particular reference to the radial clearance between rotor tips and duct inner surface and the radial distribution of rotor-blade loading. Many accounts have been written on ducted propellers but none includes the effects of clearance in any other than an approximate manner, that is, one-dimensional theory. The few studies that have been made of the radial variation in blade loading have been inconclusive and vague, mainly because of the inadequate duct model employed. Here an accurate nonlinear theory is used to represent the duct and centrebody which has already been used successfully in the prediction of ducted propeller performance. Actuator disc theory, which is particularly suitable for combination with blade-element theory, is used to represent the variable-load propeller. Computed performance characteristics compare favourably with experimental results and the present studies enable the designer to fix both tip clearance and radial load distribution to suit the particular application under consideration. The general conclusions confirm and reinforce the limited experimental results available.
The Yield, Flow and Creep Behaviour of Annealed En24 Steel under Combined Stress
Authors: Shahabi S. N. , Shelton A. 
Published: February 2007

Constant stress-ratio tests under combinations of tension, torsion and internal pressure have been performed on annealed En24 steel. The initial yield locus conformed to the Maxwell Mises criterion under tension-internal pressure but lay between the Maxwell-Mises and Tresca criteria under tension-torsion. This implies a small degree of initial anisotropy. Post-yield behaviour showed the plastic strain and strain-rate vectors to be normal to the initial yield locus and to remain so with respect to both time and increasing stress. The work-hardening hypotheses of plasticity theory were unsatisfactory in correlating any of the combined-stress results but equivalence of the strains was established from a consideration of the strain components and the angle between the stress and plastic-strain vectors. This resulted in the graphs of equivalent stress versus equivalent plastic strain in different stress fields being superposable. Room-temperature creep of the logarithmic form ε a In t + c was exhibited by all strain components and correlation of the creep coefficients was established by a method similar to that introduced for plastic strains. This finally led to a complete correlation of the stress-strain-time behaviour of this material under complex stress.
The Second Virial Coefficient of Ordinary Water Substance: A New Correlation
Authors: Le Fevre E. J. , Nightingale M. R. , Rose J. W. 
Published: February 2007

It is shown that the specific second virial coefficient for ordinary water substance, expressed as a function of temperature, is correlated by This correlation, motivated by recent observations from low-pressure steady-flow calorimetry from 20°C to 140°C, also covers older tabulated values of the second virial coefficient extending to 800°C. The Boyle temperature is found to be 1498 K. B2 = a1 f1 + a2 f2 + a3 f3 where f1 = 1/(1 + T/α), f2 = (1 - e-β/ T)5/2( T/β)1/2eβ/ T, f3 = β/ T, α = 10000 K, β = 1500 K, a1 = 0.0015 m3/kg, a2 = −0.000942 m3/kg and a3 = −0.0004882 m3/kg.
The Dynamic Behaviour of Passively Compensated, Hydrostatic Journal Bearings with Various Numbers of Recesses
Authors: Davies P. B. 
Published: February 2007

A previously established small-perturbation analysis is developed to express the unsteady-state continuity-of-flow equation for an isolated recess in a passively compensated, multirecess, hydrostatic journal bearing in terms of generalized co-ordinates. The concise form of this equation enables motion of the shaft about the concentric position to be described by equations which are derived in closed form for bearings with orifice, capillary or constant flow compensation and any number of recesses. These equations of motion, and hence the expressions for the receptances which describe the response of a bearing to external excitation, are shown to be of exactly the same form for all bearings of the type considered. Furthermore, the damping ratio and natural frequency in any particular case are determined by a single dynamic constant which is shown to be equal to a linear combination of circular functions and a limited number of coefficients which may be found explicitly by routine use of signal flow graphs. The results of the analysis, which is exact within the stated assumptions, are compared with those of other workers and the steady-state solution of the equations of motion is shown to give an expression for static stiffness which is useful for design purposes. Numerical values of the dynamic constant for bearings with between 3 and 20 recesses are given graphically.
The Plastic Behaviour of Annealed OFHC Copper
Authors: Holloway G. , Shelton A. 
Published: February 2007

The effect of progressive deformation in the plug-drawing process on the initial yield and subsequent plastic flow behaviour of oxygen-free high-conductivity (OFHC) copper has been investigated. This paper relates to the behaviour of the annealed material under combinations of tension, torsion and internal pressure, prior to cold-drawing. All loads were applied under constant stress ratio, and the initial yield points were obtained by utilizing the backward extrapolation of curves of stress versus strain and creep coefficient versus stress. The Maxwell-Mises criterion described the experimental yield locus obtained under biaxial tension but not the two tension-torsion loci. The difference is attributed to a small initial anisotropy. In post-yield behaviour, the plastic strain and strain-rate vectors were normal to the initial yield locus and remained so under increased loading. The work-hardening hypotheses of plasticity theory failed to correlate any of the combined-stress results but equivalence of the strains was established by a consideration of the coaxial stress-strain path. This method resulted in a complete correlation of the stress-strain relationship for all loading paths in all stress fields. Primary creep of the logarithmic form ε=a In t + C was exhibited by all plastic strain components, and a correlation of the creep coefficients was established on the same basis as that used for plastic strains. Finally, a complete correlation of the stress-strain-time behaviour of this material at room temperature was established.
The Elastohydrodynamic Performance of Low-Friction, Zero-Leakage Metal Seals
Authors: Ruskell L. E. C. 
Published: February 2007

Part 1 discusses the requirements for the satisfactory operation of a reciprocating metal rod seal for a hydraulic actuator. Elastohydrodynamic theory is used to predict seal performance, and results indicate that with a suitable geometry good lubrication is possible in both stroking directions of the jack rod, even when the fluid flow is against the sealed pressure. In Part 2, an experimental study of the lubrication of these seals is described. They exhibited low friction and zero net leakage, and measurements of oil film shape are presented which illustrate why this is so.
On the Effect of Bearing Clearances in the Dynamic Analysis of Planar Mechanisms
Authors: Bahgat B. M. , Osman M. O. M. , Sankar T. S. 
Published: February 2007

A systematic procedure for the dynamic analysis of planar mechanisms with multiple clearances is presented. Each link of the mechanism is considered as a rigid member, and contact modes are detected by iteration according to the inequalities of input torque and pin forces. The method is useful for predicting the number and frequency of contacts and separations occurring in the mechanism-joints for one complete cycle of the input crank. A four-bar mechanism is used to illustrate the procedure. Results show that there are significant changes in accelerations, torque and pin forces as compared with the case without clearances. Minimal changes have been detected in displacement and velocity relationships. The model presented in the paper provides a design method for investigating torque requirements, pin forces and separation occurrences in high-speed machines with clearance.
Some Effects of Heat-Treatment upon the Mechanical Properties of Electroformed Iron-Nickel Alloy Foil
Authors: Lai S. H. F. , McGeough J. A. 
Published: February 2007

Contributions intended for publication as Research Notes should preferably be limited in length to 1000 words and two illustrations, and should be addressed to the Manuscript Section, The Institution of Mechanical Engineers, I Birdcage Walk, Westminster, London SW1H 9JJ The problem of hydrogen embrittlement, which adversely affects the quality and mechanical properties of electroformed iron-nickel alloy foil, is considered. Heat-treatment, such as annealing, can reduce these effects of hydrogen embrittlement. The electroformed metal can also be converted to alloy steel by carburizing; and by other heat-treatments, such as hardening and tempering, a range of mechanical properties for the foil can be achieved.