bluuebunny/crossref_metadata_2025 huggingface dataset:
Modes at Rest and Their Stability in Coupled Non-Linear Systems
Authors: Henry R. F. , Tobias S. A.
Published: February 2007

This paper deals with the stability of modes at rest in free, undamped non-linear two-degree-of-freedom systems governed by equations of motion of the form

The conditions necessary for the existence of motion in a single mode are discussed and a criterion for stability of the mode at rest established. The theory is compared with results of tests made on an experimental model. The effect of viscous damping on stability is also examined. The results obtained are applicable to current practical problems in the field of vibration isolation and suppression.
Elastic Solution in the Limit Analysis of Shells of Revolution with Special Reference to Expansion Bellows
Authors: Marçal P. V. , Turner C. E.
Published: February 2007

The elastic solution is used to calculate lower and upper bounds for symmetrically loaded shells of revolution. In order to obtain the upper bound, a number of circumscribed yield surfaces are used to introduce a flow mechanism. The results obtained are compared with experimental and other limit analysis results.
Preparation of Steam Tables with the Aid of a Digital Computer
Authors: Bain R. W.
Published: February 2007

This paper describes the use of a digital computer in deriving an empirical equation of state for steam, based on experimental data on its pressure-volume-temperature properties. A table of specific volume at round values of pressure and temperature, derived from this equation, is given. This table is preliminary and further work is going on to extend and improve it.
Energy Dissipation at Spherical Surfaces in Contact Transmitting Oscillating Forces
Authors: Johnson K. L.
Published: February 2007

In a previous experimental investigation the author has shown that two spherical surfaces pressed together and subject to an oscillating tangential force, however small, exhibit microscopic interfacial slip which leads to energy dissipation and surface damage in the manner predicted theoretically by Mindlin. The analysis has been extended by Mindlin and Deresiewicz to include the effect of an oscillating force whose line of action lies at an oblique angle to the surface of contact. They show that the angle of obliquity of the oscillating force has a predominant effect on the energy dissipated at the contact and that no slip or dissipation would be expected if the line of action of the force lies within the cone of friction for the two surfaces.

These conclusions have been the subject of the experimental investigation reported in this paper. The theoretical predictions are supported by the observations on almost all counts. Such discrepancies as occur are shown to be due to the inadequacy of the theoretical assumption of a constant coefficient of friction to describe accurately the actual behaviour of metallic surfaces in contact which are undergoing oscillating interfacial slip and fretting whose amplitude varies throughout the contact area.
Thermal Stresses in Tubular Heat-Exchanger Fins
Authors: Cole B. N. , Coulthard L. M. F.
Published: February 2007

In the paper the authors discuss a unified treatment of thermal stresses arising in spiral fin geometries ranging from straight axial fins to annular disc fins. Temperature is assumed to vary with radius only; and if necessary a variation of fin thickness with radius can be accommodated. Specimen calculations suggest that, for a given fin height and overall temperature difference, induced stresses are much lower for a spiral fin of helix angle about 30 to 60° than for either an axial or discord fin. A byproduct of the analysis is a method of estimating the inertia stresses arising in certain types of helical rotor.
Initiation of Boiler Scale Formation
Authors: Freeborn J. , Lewis D.
Published: February 2007

This paper describes part of a programme of fundamental study of scale formation. The work described here is concerned with the initiation of scale formation at a heating surface where boiling is taking place. The crystalline ring formations first observed by Partridge (I) with calcium sulphate solution were seen using a range of other solutions under various flow conditions. A variety of other formations based on Partridge's rings were also observed. The theory advanced by Partridge that these deposits are due to evaporation at the triple interface of steam bubble, heating surface and solution was in general confirmed. A dynamic mechanism is proposed to explain these formations.
Experimental Investigation of Turbulent Heat Transfer in the Entrance Region of a Circular Conduit
Authors: Mills A. F.
Published: February 2007

The local heat transfer characteristics for air flowing turbulently in the entrance region of a circular duct have been determined experimentally over a flow Reynolds number range of 10 000 to 110 000. A wall-boundary heating condition of uniform heat flux was imposed. The entrance configurations investigated included a long calming section, bellmouth, orifice plate arrangements and various entries of practical significance—elbow, T-piece, etc. A correlation of heat transfer under fully developed conditions is included together with a discussion of the effects of fluid property variation in an axial direction. Entrance-region heat transfer data are presented in the form of local heat transfer film coefficients and as the dimensionless ratio , this quantity being defined in such a manner as to eliminate the effects of fluid property variation in an axial direction. Data for average heat transfer over tubes of lengths from 1/4 diameter to 320 diameters are presented in the form of the ratio . In the case of the long calming section the results are compared with the results of previous investigations, both experimental and theoretical, the agreement being satisfactory. The use of thermal entrance lengths is discussed and the values obtained are compared with previously accepted values. The heat transfer characteristics obtained with the bellmouth yielded interesting information pertaining to the position and nature of the transition from a laminar to a turbulent boundary layer.
Synchronous Whirl of a Vertical Shaft Having Clearance in One Bearing
Authors: Johnson D. C.
Published: February 2007

If a vertical undamped shaft has one clearance bearing, the other bearings having zero clearance and all being in line, then there are two possible regimes of synchronous whirl which can hold, namely:

that in which the shaft does not touch the clearance bearing, that in which the shaft touches the clearance bearing continuously, the point of contact running round the bearing at the shaft speed.

It is shown that in some speed ranges regime (1) holds and in others (2). There are also speed ranges in which either regime is possible.

When damping is allowed for, these results are not greatly modified. The whirling behaviour of the shaft differs however from that of a shaft with zero bearing clearance in several ways. In particular the critical speeds are lower, and also there is a more abrupt drop in the whirl amplitude curve above the critical speeds.

The behaviour of the shaft when it is accelerated through a critical can differ from that when it is decelerated.
Measurement of the Drag on Spheres Moving through Gaseous Fluidized Beds
Authors: Daniels T. C.
Published: February 2007

Certain substances float on the surfaces of gaseous fluidized beds and others sink. This phenomenon has industrial applications in separation by creaming and sedimentation. To help the development of these applications the author measured the drag on metallic spheres falling through various fluidized beds of glass beads and certain granular powders. The meta***llic spheres were attached to a nylon thread which passed over a pulley system. Different balance weights were attached to the other end of the thread to produce different uniform velocities of fall. The friction of the system and the buoyancy of the immersed metallic spheres were predetermined. The drag on the sphere was then the only unknown. It was found that the drag is a function of three dimensionless groups, namely Reynolds number, Froude number and the ratio of the diameter of the metallic spheres to the mean diameter of the glass beads or powders forming the fluidized beds.

For spheres above a certain diameter deviation occurred in the measurement of the drag owing to wall effect.
Elasto-Hydrodynamic Lubrication: A Survey of Isothermal Solutions
Authors: Dowson D. , Higginson G. R. , Whitaker A. V.
Published: February 2007

Recent work by the authors and others on the lubrication of elastic rollers is briefly reviewed. The full effects of speed over a wide range and of lubricant compressibility are presented for the first time. Speed is shown to be the most important variable in the problem. Compressibility has little effect on the film thickness, but it may alter the pressure distribution appreciably.
Torsional Waves in Uniform Rods of non-Circular Section
Authors: Barr A. D. S.
Published: February 2007

A differential equation for the torsional vibration of a uniform rod of non-circular section is derived which takes into account the longitudinal stress and inertia which arise from the warping of the cross-section. The boundary conditions relevant to the problem are also obtained. Curves showing the dispersion of torsional waves in rods of rectangular section as predicted by this theory are given and a comparison is made with the results of more simple torsion theories which either neglect the longitudinal stress and inertia effects or which take account of only one or other of them. Experimental resonance tests on rods of rectangular section for various side ratios are used as a basis of comparison with the theory for relatively long wavelengths and good agreement is found.
Matrix Techniques for Determination of Fundamental Mode Shape and Frequency Parameter of Torsional Oscillations in Engines
Authors: Gupta K. N.
Published: February 2007

Matrix techniques for the solution of natural frequencies of a torsional system are proposed for their simplicity and easy manipulation. The tedious calculations in obtaining a dynamic matrix are alleviated by evolving a general expression for dynamic matrix for fundamental mode of a multi-degrees of freedom straight torsional system.

Further, the dynamic matrices for engine systems having four to eight cylinders with equal moments of inertia per cylinder line and equal shaft stiffnesses between the cylinder centres are deduced from a general expression. They are iterated upon five times to obtain expressions for the fundamental frequency parameter, which are further used to obtain the relative amplitudes and the frequency parameter of different engine systems. The results obtained by five times iteration are in close agreement with the exact values.
Velocity Profile Development in Axial-Flow Compressors
Authors: Railly J. W. , Howard J. H. G.
Published: February 2007

A theory for the development of the axial and peripheral velocity profiles in the early stages of an axial-flow compressor is presented. The theory assumes the existence of a stall-zone in the corner formed by the convex surface of each blade and the annulus wall. The extent along each blade of this stall-zone is assumed to be related to the theoretical annulus boundary layer thickness; equations are derived for predicting its growth through the blade roots and tips. The conditions at the blade ends are determined from the theory of a two-dimensional stalled cascade and the outlet angle variation is determined by momentum mixing. Actuator disc theory is then used to find the resulting flow. The predictions of this method are compared both with experimental results obtained from a three-stage compressor and with the predictions of secondary flow theory in which both loss and blade row entry velocity profile are taken from experiment. Somewhat better agreement between the stall-zone theory and experiment is found and to make the theory useful for designers the determination of a single parameter from experiment is indicated.
Modes and Frequencies of Shafts Coupled by Straight Spur Gears
Authors: Johnson D. C.
Published: February 2007

A pair of shafts, connected by gears, forms a mechanical system having a number of modes of vibration. Each mode involves a combination of torsion and flexure of the shafts and of bending of the meshing gear teeth. A method of finding these modes, together with their corresponding natural frequencies, is described and illustrated by a numerical example. Such modes can be set into resonance by, amongst other things, the oscillating forces which arise in the tooth meshing process.
Tensile Instability in Thin-Walled Tubes
Authors: Mellor P. B.
Published: February 2007

An analytical solution giving conditions at instability of a thin-walled tube subjected to internal pressure and independent axial load is presented. An attempt is made to explain the physical reasons for the occurrence of an instability.

The analysis shows that a given material has greatest ductility when the ratio of the hoop stress to axial stress has the value one half. The material has least ductility when it is in the form of a closed-ended tube subjected to internal pressure.

The terms ‘tensile strength’ and ‘percentage elongation’ are discussed within the framework of the present investigation.
Calculation of Rolling Load and Torque in the Hot Planetary Rolling Mill
Authors: Sparling L. G. M.
Published: February 2007

This paper presents a completely new approach to the mechanics of the Sendzimir hot planetary rolling mill. Previous work on this subject, by R. Tovini, included determinations for the distribution of the advance of the strip, the draft, the rolling load, the torque and the horizontal backthrust for the whole range of positions which the planetary rolls made, whilst contacting the hot metal. The new approach differs vastly from that of Tovini, the main four differences being as follows.

First, whereas the method of Tovini is based upon the forward displacement of surface metal, as a ripple, along the surface of a rigid core which extends in the central portion of the metal for the full length of the working arc, the new approach assumes that the plastic zones between the planetary rolls extend from each roll to the centre of the material. The effect of this assumption is that the local deformation due to a pair of planetary rolls can be considered as an extension which is effectively uniform throughout the thickness of the strip which is instantaneously between the planetary rolls.

Secondly, the method used by Tovini is one of successive approximations to obtain values for the advance of the strip, whereas the new method finds a close approximation for the advance of the strip by direct analysis.

Thirdly, Tovini neglects the friction hill in roll load and torque calculations and uses the mean strain rate for the equivalent simple roll in order to calculate the mean yield stress, whereas the new method defines and uses both local and overall mean strain rates, these being necessary to obtain a realistic value for the resistance to deformation.

Fourthly, in Part 1 of Tovini's paper, intermittent advance of the strip was assumed, whereas in the present method uniform entry speed is assumed and it is then shown how the results for any distribution of entry speed can be obtained by superposition. (In Part 2 of Tovini's paper continuous advance of the slab is briefly considered but, the process is not analysed in detail.)

Appendix I shows a method of tabular calculation, which gives results for the distribution of roll separating force, torque and backthrust for the whole range of angular positions during which a pair of planetary rolls contact the strip or slab. From these results the back-up roll separating force, the horizontal backthrust and the horsepower for the process can be derived.
Experimental Study of the Flexibility of a Full-Scale Two-Dimensional Steam Pipeline
Authors: Smith R. T. , Ford Hugh
Published: February 2007

This paper describes tests made to check the reliability of the calculation methods used to predict the flexibility, forces, and stresses in a typical pipework system.

A test rig set up in the laboratory has been used to carry out tests on a full-scale pipeline of 6 1/2-in. nominal bore pipe for 450 lb/in2 working pressure and 750°F steam temperature with two right-angle bends. Tests at room temperature have been made with controlled anchor movements corresponding to those which would occur on cold pull-up, thermal expansion, or pure bending, all without internal pressure. In addition tests have been made with internal pressure only, and with internal pressure combined with controlled anchor movements. Further tests were carried out by heating the pipeline and measuring the increase of the forces at the restrained anchors, but no strain measurements were made at high temperatures.

The results show that the calculation methods are sufficiently reliable for predicting the forces and stresses in such a pipeline, having regard to the allowable tolerances on pipe dimensions.
Investigation of the Behaviour of a Four-Stand Tandem Mill, Using an Electronic Analogue
Authors: Sekulic M. R. , Alexander J. M.
Published: February 2007

A study is made of systems based on screw-setting and tension control, and the behaviour of a four-stand tandem mill when subjected to small disturbances from the steady state is investigated by using an electronic simulator.

Screw-setting control and control of tension through control of roll speed are the practical variables which can be used in the automation of a tandem mill and a possible closed loop system of control is discussed.
Vortex Excited Vibration of a Heat Exchanger Tube Row
Authors: Livesey J. L. , Dye R. C. F.
Published: February 2007

The results are presented of an experimental investigation into the possible modes of gas-excited vibration of a single row of tubes in a heat exchanger at typical practical spacings. The vibrations discussed are vortex excited and, for damping which permits large amplitudes, occur at values of the Strouhal number 0·26 < ND/V < 0·89. The critical range of ND/V is affected by both Reynolds number and spacing. Four distinct modes of vibration are found, all consisting of motion principally transverse to the flow direction.

Preliminary studies of pairs of tubes, at varying spacing, indicate similarly large ranges of the parameter ND/V in which vibration will occur at typical practical spacings.

The types of vibration described are distinct from, and should not be confused with, either the acoustically coupled type or the equally important modes, in which the motion is principally streamwise, occurring at much lower values of ND/V.
Stiffness of Broad-Faced Gasketted Flanged Joints
Authors: Kenny B. , Moore G. G. , Duncan J. P.
Published: February 2007

The mechanism by which broad-faced flanged joints retaining a circular plate exert restraint against the flexure of the plate due to pressure differentials is discussed and studied experimentally.

The theory proposed by Yi-Yuan Yu for determining the stiffness of an ungasketted joint is reconsidered and modified to suit the observed behaviour of metal-to-metal joints and of joints where one or more gaskets are included between mating surfaces of the joint assembly. Hence, a more exact method for calculating stiffness factors for such joint assemblies is formulated.

Experiments were conducted on a particular design of header to tube-plate assembly and the results used to check the validity of the modified theory.
Effect of Eccentricity of Stiffeners on the General Instability of Stiffened Cylindrical Shells under Hydrostatic Pressure
Authors: Baruch M. , Singer J.
Published: February 2007

The general instability of a simply supported cylindrical shell under hydrostatic pressure is analysed by considering the ‘distributed stiffness’ of the frames and stringers separately, taking into account their eccentricity. It is shown that frames on the inside of the shell yield general instability loads about 10–15 per cent greater than frames on the outside of the shell. Stringers are much less effective in stiffening a shell under hydrostatic pressure, and the effect of eccentricity is opposite; outside stringers yield critical loads greater than inside stringers.
Equivalent Elastic Properties of Perforated Bars and Plates
Authors: Duncan J. P. , Upfold R. W.
Published: February 2007

Experimental methods are described by means of which the equivalent elastic properties of bars and plates perforated on a square, a square-diagonal or a triangular pitch (or otherwise) may be obtained.

Bars of rectangular section of steel, gun metal and perpex perforated on a fixed pitch with circular holes to give a wide range in the ratio (pitch/diameter of holes) on square and triangular patterns were tested in flexure and tension. The transverse aeolotropy of such bars and plates was examined and ratios of (equivalent Young's modulus, drilled/true Young's modulus) and equivalent Poisson's ratios were found.

The experimental results obtained were compared with theoretical curves of Bailey and Hicks for perforated plate of square and square-diagonal pitch and with Horvay's plane-stress theory for perforated plate of triangular pitch.

Results have been presented in graphical form for ready application to the design of heat exchanger tube-plates.
On the Determination of Residual Stresses in Tubes
Authors: Denton A. A. , Alexander J. M.
Published: February 2007

Analytical expressions are proposed, from which the circumferential and longitudinal residual stresses present in a tube may be found by measurement of changes in curvature after slitting and layer removal. The effect of variation of the tube length, previously thought to be anomalous, is satisfactorily explained by the present analysis.

The methods of measuring residual stress which were proposed by Davidenkov, Sachs and Espey, and Treuting and Read, are examined in detail and are shown to be inaccurate in certain circumstances.
Damping Properties of Thin Oil Films Subjected to High-Frequency Alternating Loads
Authors: Hother-Lushington S. , Johnson D. C.
Published: February 2007

Damping Properties of Thin Oil Films Subjected to High-Frequency Alternating Loads

An investigation has been made into the energy loss in thin oil films when these were subjected to high-frequency alternating loads.

Experiments were performed on oil films between two parallel plates when one of them was given a sinusoidal motion relative to the other in a direction normal to the plane of the plates. The frequencies used were in the range 400 to 4000 c/sec.

The experiments showed that the energy loss is less than would be expected because of cavitation of the oil film and a qualitative theory is given which goes some way towards explaining the experimental results.
Non-Linear Torsional Oscillation of a System Incorporating a Hooke's Joint
Authors: Porter B. , Gregory R. W.
Published: February 2007

The method of Kryloff and Bogoliuboff is used to investigate the non-linear oscillation of a system incorporating*** a Hooke's joint. It is found that the system ultimately executes a limit cycle of oscillation and that, in certain critical speed ranges, the amplitude of this oscillation is large if the system is lightly damped.
Vibration of a Free Gyroscope on a Non-Uniform Elastic Shaft
Authors: Wippell A. P. R. , Maunder L.
Published: February 2007

This paper is a sequel to a previous work in which the vibrations were considered of a gyroscope mounted on a uniform elastic shaft within two rigid gimbals. The theory has now been extended to include a more general practical arrangement in which the shaft is non-uniform. Experimental results have also been obtained which confirm the general conclusions of the theory.
Lateral Deflections of Circular Cylinder Walls during Buckling
Authors: Ricardo O. G. , Marreco D. , Csoknyai H.
Published: February 2007

The lateral deflections of circular cylinders with thin walls were recorded during buckling. Ten pick-up points were chosen along a transverse section of the cylinder, and their deflections recorded simultaneously.

The results suggest, within the precision of the measurements made, that buckling starts simultaneously or with a delay not larger than 0·02 sec, in a large region of the transverse section. Sometimes a local buckling wave appears before general collapse, but this wave does not seem to propagate continuously towards the final shape of the buckled surface.

It can also be concluded that, at buckling and after 0·01 or 0·02 sec, the wall tends directly to a stable polyhedral configuration, with a well-determined number of sides. No intermediate stage could be detected.

These results are interpreted according to previous studies of one of the authors, in such a way that an explanation of the ‘jump’ phenomenon is attempted, without the necessity to pass over Tsien's ‘energy jump’.
Experimental Investigation of Free Convection in a Liquid Metal in Long Tubes
Authors: Bayley F. J. , Czekanskit J.
Published: February 2007

This paper reports an extension of a previously published investigation into the natural convection process in a liquid metal (4), using circular tubes closed at their lower ends, operating on the thermosyphon principle of heat transfer. In this work longer tubes were used than previously and two distinct regimes of flow were observed. At low heating rates the non-dimensional heat transfer coefficient was found to be a linear function of the temperature difference, and the fluid at the lower end of the tube appeared to be stagnant, contributing negligibly to the overall heat transfer process.

At higher heat transfer rates, the data followed the general trends of the previously observed flows in a liquid metal, although The Heat Transfer Rates Were At Least 17 Per Cent Less Than With Normal Boundary Layer Flow, and More Dependent Upon The Surface Geometry. This Was Due To Interference Between The Heated Boundary Layer and The Core of Cooler Fluid, and This Caused Violent Oscillations In The Temperature of The System Which Persisted Throughout The Entire Test Programme.
Elastic Stresses in Single Mitred Bends
Authors: Owen B. S. , Emmerson W. C.
Published: February 2007

Experimental results are presented for the stresses caused by internal pressure in thin pipes which are mitred and welded together to form a single mitred bend without any type of elliptical insert at the intersection. The frozen-stress photoelastic technique is used, the models being carefully machined and cemented to form a joint free from welding imperfections. The results are compared with the theoretical analysis for small-angle mitred bends, of Green and Emmerson (I)†. An alternative derivation of this theory is given in Appendix I. Good agreement with the theory is shown for small-angle bends for each of the two thicknesses of pipe used. For larger angles of bend, the agreement is less good. The results of a test carried out on a mitred joint subjected to an in-plane bending moment, are included.
Studies of Flow and Heat Transfer Associated with a Rotating Disc
Authors: Richardson P. D. , Saunders O. A.
Published: February 2007

Experimental investigation of laminar heat transfer from an isolated disc is described, account being taken of simultaneous forced and natural convection. It is concluded that results are correlated well by

The influence of the radial velocity profile upon turbulent heat transfer is discussed. Measurements of the flow beyond the edge of a rotating disc are outlined, and it was found that beyond about 40 per cent of the disc radius from the disc edge the flow closely resembles that in Squire's radial jet, but with a whirl component of velocity. Details of the influence of nearby stationary planes upon the flow and heat transfer from a rotating disc are given; it is shown that the presence of such planes can considerably reduce the heat transfer.
A Critical Introduction to Some Industrial Resonance Testing Techniques
Authors: Pendered J. W. , Bishop R. E. D.
Published: February 2007

This paper gives details of apparatus which was designed to permit an initial appraisal to be made of methods of resonance testing. A fairly lightly damped system with widely spaced natural frequencies was used. The ‘peak-amplitude’ technique of testing gave excellent and consistent results, though a simple alternative (and apparently novel) approach was superior in one respect, namely for the measurement of resonant frequencies. The Kennedy and Pancu method also gave good results but required more effort. A recently-suggested method of estimating damping was not found to be satisfactory or as good as the standard methods for the uncomplicated system under test. The simplest dynamical systems, then, appear to demand only the simplest of the techniques in current use in industry.
Stresses in Internal Combustion Engine Poppet Valves
Authors: Fessler H. , Ollerton E.
Published: February 2007

The stresses induced by the firing pressure and the spring force have been determined by the frozen-stress photoelastic technique for two shapes of valve. The results are compared with stresses calculated for flat circular plates of varying thickness. Because the calculated stresses were greater than the measured stresses, this simple method of calculation is described. Curves are presented to assist in rapid calculation of these stresses for any shape of valve.
Frequency Response of Linear Counterflow Heat Exchangers
Authors: Thomasson R. K.
Published: February 2007

Expressions for the frequency response of linear counterflow heat exchangers are derived in non-dimensional terms. Calculated responses for a number of cases are presented in the form of complex plots. The effect of sinusoidal variation of inlet temperature is to set up two systems of temperature waves, one travelling in the direction of the primary-side flow, the other in the direction of the secondary-side flow. The attenuation and velocity of these wave systems is a function of the forcing frequency. Interference between these systems leads to some rather unusual frequency response loci. The examples are typical of sodium-sodium heat exchangers used in fast-reactor power plants, but the formulae developed are suitable for more general use.
Effect of Yield on the Interference between a Pin and a Plate
Authors: Lambert T. H. , Snell C.
Published: February 2007

The optically sensitive coating technique is used to determine the post-elastic behaviour of a large plate with an interference fit pin. An aluminium alloy exhibiting a small degree of work-hardening was chosen and this is thought to be similar in behaviour to a lightly cold-worked mild steel. Theoretical analysis of an idealized material indicates that work-hardening has a significant effect on the spread of plastic regions.
Flow of a Fluid in an Axially Rotating Pipe
Authors: White A.
Published: February 2007

This paper presents the results of a preliminary experimental investigation into the flow of a fluid in an axially rotating pipe. It has been shown that the flow is stabilized when the pipe is rotated about its axis. At values of Reynolds number corresponding to turbulent flow in a stationary pipe it has been shown that the flow resistance is considerably reduced when the pipe is rotated, and at high rotational speeds reductions in pressure loss up to as much as 40 per cent were observed. Flow visualization experiments have shown that radial migration of fluid particles from the core of the fluid towards the pipe wall are diminished, and thus the rate of energy dissipation is reduced.
Lateral Vibration of Shafts Having Radial Symmetry and Appreciable Gyro-Action
Authors: Black H. F.
Published: February 2007

Research into existing work on gyroscopic action in the lateral vibration of radially symmetric shaft systems shows room for further work on practical methods of predicting natural whirl frequencies and shapes. The author of this paper seeks to explore the extent to which principal co-ordinate analysis is applicable. Within the limits of this applicability, approximation formulae and iterative processes are developed for the prediction of all critical lateral vibration or whirling conditions.
Effect of Plastic Deformation on the Strain Distribution around Cracks in Sheet Materials
Authors: Dixon J. R. , Strannigan J. S.
Published: February 2007

The strain distributions around fatigue cracks in nine different sheet materials have been obtained using a photoelastic surface-coating technique. It was found that the strains in the local plastic region around the tip of the crack were higher than predicted by elastic theory. For the materials tested, except mild steel, the elastic-plastic maximum shear-strain γ distribution around a crack in a wide sheet could be estimated during loading from the expression , where E is the modulus of elasticity, Es the secant modulus corresponding to γ, and γ0 the elastic solution for the maximum shear strain.
A New Determination of the Kinematic Viscosity of Steam at Supercritical Pressures and Temperatures
Authors: Ray A. K.
Published: February 2007

This paper records new measurements of the kinematic viscosity of steam at pressures from 300 kgf/cm2 to 800 kgf/cm2 and at temperatures from 380°C to 700°C. A viscometer of a type developed from that of Rankine (1)† has been used to obtain these measurements which may be considered as complementary to results already reported by Kjelland-Fosterud (2) and Whitelaw (3) with a similar type of apparatus. Consequently, only essential differences in the apparatus used by the author are outlined here. The author, in the paper, reviews the present position with respect to viscosity determinations at supercritical conditions in the light of the recent International Conference on the Properties of Steam, at which it has been agreed to draw up a first skeleton table of viscosity values with tolerances.
Heat Transfer from a Rotating Tube with Controlled Fluid Flow
Authors: Pattenden R. F.
Published: February 2007

The effect of rotating a tube on its axis while separate fluids flow inside and out, these fluids being discouraged from following the rotation of the tube, has been studied both from the standpoint of heat transfer and in order to ascertain the flow pattern associated with this heat transfer. Very high heat-transfer coefficients can be obtained in this way indicating that highly turbulent flow is achieved, possibly in conjunction with Taylor vortices. The heat transfer is affected far more by tube rotation than by changes in axial flow rate, and thus rotational speed is the controlling factor. Methods of measuring the temperature of the rotating tube a to fairly high degree of accuracy formed a considerable part of the experimental work.
Fluid Friction and Leakage between a Stationary and Rotating Disc
Authors: Bayley F. J. , Conway L.
Published: February 2007

This paper describes an investigation of the flow in a narrow gap between a rotating and stationary disc with an arbitrarily imposed radial pressure difference. This system represents the conditions pertaining between the rotors and casings of many fluid machines.

The investigation is mainly experimental, for although the equations of motion were derived for the fluid system in question, these were found not to be tractable for the conditions observed. Experimental results are reported from two separate test series. The first test series yielded data on the frictional and pressure forces in the system which were obtained in sufficient detail for use in design calculations for fluid machinery. In the second series the flow between the discs was studied in detail in order to explain the nature and form of the results obtained in the first series of tests.
Cyclic Stress Required to Propagate Edge Cracks in Eight Materials
Authors: Frost N. E. , Greenan A. F.
Published: February 2007

Fatigue tests have been carried out at zero mean load on plate specimens, of eight materials, containing two opposite small co-planar edge cracks. The results confirmed that whether or not a crack would grow was governed by the parameter ρ3*** l where ρ is the semi-range of the nominal alternating stress and l is the edge-crack length. If ρ3 l > C a crack would grow; if ρ3 l < C a crack would remain dormant. The value of C was determined for each material.
Influence of Cross-Section Distortion on the Bending Vibration of Thin-Walled Beams of H Section
Authors: Barr A. D. S. , Duthie T.
Published: February 2007

Approximate differential equations describing the bending vibration of beams of thin-walled H section, in which the distortion of the cross-section in its own plane is taken into account, are derived from Hamilton's principle using an assumed form for the cross-section deformation. Only the simplest of the cross-sectional deformation configurations which will couple with ordinary bending is considered. The variation with wavelength of the two spectra of frequencies which result from this coupling of the bending and cross-sectional motions is shown for several section geometries. Theoretical curves show reasonable agreement with experimental results from free beams.
A Set of Creep Curves from a Single Test using a Tapered Specimen
Authors: Levy J. C. , Bàròdy I. I.
Published: February 2007

The use of a tapered form of specimen for creep testingi s described. Strains are measured on a series of short gauge lengths, enabling a family of isothermal creep curves at different stresses to be obtained from a single test. The measurement of strain is by the replica method, but other methods are not necessarily excluded.

Testing of tapered specimens makes possible a considerable saving in the aggregate time and material necessary to establish a set of creep curves, with little sacrifice of accuracy. Data are presented for the aluminium alloy DTD 5070A, and results from tapered specimens compare favourably with creep curves obtained in conventional tests.
Experimental Investigation into the Effect of the Thermal Boundary Condition on Heat Transfer in the Entrance Region of a Pipe
Authors: Hall W. B. , Khan S. A.
Published: February 2007

Experimental results are presented for forced convection in the entrance region of a pipe; the results were obtained using both the boundary condition of uniform heat flux and that of uniform temperature. A significant difference which is attributable to the different boundary conditions was observed for Reynolds numbers below about 3 times 104, but at higher Reynolds numbers the difference rapidly diminishes.

An approximate numerical solution for the early stages of boundary layer formation on the pipe walls gave similar differences between the two boundary conditions as were observed in the experiment.
Continuous Automatic Balancing of Rotating Systems
Authors: Vande Vegte J.
Published: February 2007

An automatic balancing system with continuous operation is proposed, based on the use of correction masses which are continuously adjustable relative to the rotating system. A feedback control system positions these masses so as to counterbalance the inherent system unbalance. This application of feedback control principles reduces the dependence upon accuracy of calibration. A major advantage is that systems with time-varying unbalance conditions, due to wear or foreign material, can be rebalanced without interrupting operation. The application to single-mass and multiple-mass systems will be discussed, including the special considerations necessitated by operation near critical speeds.
Buckling of Double Bellows Expansion Joints under Internal Pressure
Authors: Newland D. E.
Published: February 2007

Corrugated bellows expansion joints may buckle under internal pressure in the same way as an elastic strut may buckle under an axial load. This paper is concerned with the analysis of this phenomenon for the ‘universal expansion joint’ which incorporates two bellows joined by a length of rigid pipe. The principal conclusion is that, by providing a correctly designed supporting structure, the critical buckling pressure can be increased to up to four times its value for the same system with no supports.
Influence of Pipe Friction and Heat Transfer on Pressure Waves in Gases: Effects in a Shock Tube
Authors: Bannister F. K.
Published: February 2007

Finite-amplitude pressure waves travelling in gases in pipes are subject to the influence of pipe friction and heat transfer to or from the pipe wall. Where the pipe section is moderate or small these factors cause serious departures from the classical laws governing wave motion under frictionless adiabatic conditions.

The paper presents a theoretical analysis of the effects of friction and heat transfer, assuming that at any instant and location the frictional force and heat-transfer rate in a pipe element are those for steady flow at the same Reynolds number. Based on the three-directional method of characteristics, a step-by-step procedure is developed for the solution of practical problems involving wave motion in pipes of moderate diameter, for example, in internal-combustion engine exhaust pipes.

The procedure is illustrated by application to the wave motion in a simple shock tube of moderate initial pressure ratio. Experiments using such a shock tube confirm the validity of the theoretical treatment.
Effect of Large Hydrostatic Pressures on the Torsional Fatigue Strength of two Steels
Authors: Burns D. J. , Parry J. S. C.
Published: February 2007

This paper describes tests in which two alloy steels were subjected to reversed torsion at atmospheric or high ambient pressure. It is shown that if the specimens are protected, superimposed fluid pressures increase the fatigue limits of both steels. For instance a pressure of 25 ton/in2 raises the nominal fatigue limit of a 2 1/2 per cent nickel-chromiummolybdenum (En 25) steel by about 46 per cent. It is concluded tentatively that a superimposed hydrostatic pressure improves fatigue strength by introducing a compressive stress on planes of maximum alternating shear stress.
Dynamic Stress Concentrations at Circular Holes in Struts
Authors: Dally J. W. , Halbleib W. F.
Published: February 2007

Dynamic stress concentrations were determined for a strut with a centrally located hole by employing photoelastic measurements. Single spark photography together with controlled repeated loadings on Columbia resin CR-39 models was utilized to obtain the dynamic fringe pattern. In general, it was found that the dynamic stress concentrations differed significantly from the static stress concentrations. The difference depended upon the geometry of the model and the location at the boundary of the hole.
Model Correlations for Investigating Creep Deformation and Stress Relaxation in Structures
Authors: Frederick C. O.
Published: February 2007

This paper establishes a range of possible creep model correlations based on uniaxial constant stress creep data and variable stress creep laws. It is shown that the model behaves as an analogue which can be used to solve the differential equations governing the deformation of the prototype. The most general correlations hold for time-hardening materials where creep data can be flitted by a stress index. The least general correlations hold for strain-hardening materials whose data can only be fitted to a function of stress. Elastic strains and variable loads are included in the analysis.
Analysis of Creep in Cylinders, Spheres and Thin Discs
Authors: Smith E. M.
Published: February 2007

A method of analysing the creep behaviour of cylinders, spheres and thin discs is described, in which the effects of time variation of the environmental conditions of temperature, pressure, rotational speed and internal heat generation may be accommodated.

Deformation is considered as a series of steps each consisting of a short period of steady state creep followed by instantaneous stress readjustment to resatisfy the equations of equilibrium and compatibility. The relationships for stress readjustment can be written down once for all, since they are independent of the type of creep law used and of the length of time interval taken. The simultaneous solution of these relationships is presented in a form suitable for incorporation in computer programmes.
Effect of Sound on Heat Transfer from a Horizontal Circular Cylinder at Large Wavelengths
Authors: Lee B. H. , Richardson P. D.
Published: February 2007

The practical relevance of investigations of the effect of oscillations on convective heat transfer is discussed. Some experiments on overall heat transfer from a horizontal heated circular cylinder in a transverse, horizontal standing sound field are reported. Observations of local effects of sound on boundary layer thickness and heat transfer are described, and a correlation of heat transfer spanning all sound intensities is suggested in the light of these observations. The correlation is fitted well by the data, and thus provides adducive evidence for the explanation of the phenomena observed.
Cumulative Fatigue Damage under a Symmetrical-Sawtooth Loading Programme
Authors: Marsh K. J.
Published: February 2007

A description is given of a modified rotating-bending fatigue machine which enables specimens to be submitted to repeated stress cycles modulated by a symmetrical-sawtooth wave, i.e. to a triangular stress block. Results are given of tests on plain and sharply notched mild-steel specimens and are discussed with reference to some existing concepts of fatigue damage accumulation. It is shown that, for mild steel, a hypothesis which neglects stress cycles having an amplitude of less than the fatigue limit of the material gives an optimistic prediction of specimen life but that to neglect cycles of amplitude less than 80 per cent of the fatigue limit gives results which agree closely with experiment.
Machining Forces: Some Effects of Tool Vibration
Authors: Wallace P. W. , Andrew C.
Published: February 2007

When tool vibration occurs during machining both the undeformed chip thickness and the cutting forces have oscillating components. An examination of previous work reveals that both the relative phases and amplitudes of the oscillating forces and the oscillating undeformed chip thickness can be affected appreciably by changes in frequency. The explanations for this behaviour which have been put forward are not entirely consistent with previous experimental evidence. In the present work an analysis of the thrust forces occurring during tool vibration is proposed. The analysis is based on the assumption that there are two components to the oscillating thrust force: (1) a component proportional to, and in phase with, the oscillations in undeformed chip thickness and (2) a component, caused by contact between a small area of the tool flank and the freshly cut work surface, which leads the oscillation in undeformed chip thickness by 90°. Experimental results are presented which validate the assumptions made in the analysis. On applying the analysis to present and past experimental results, there is good agreement between theory and experiment when cutting at sufficient speed to prevent the formation of a substantial built-up edge: when cutting within the built-up edge speed range the theoretical predictions are less satisfactory, though still qualitatively correct. The results also show that changes in undeformed chip thickness have a smaller effect on the tool forces under vibratory conditions than under steady conditions.
An Analysis of Surface Wave Instability in Grinding
Authors: Gurney J. P.
Published: February 2007

A graphical method of analysis of surface wave instability in grinding is presented. This form of instability is characterized by uneven wear of the wheel, causing surface waves to form about its circumference. A progressive deterioration in the finish of the work results, together with an increase in the level of vibration. This is a type of self-excited vibration, and is not due to inhomogeneities in the wheel.

The factors affecting the number of waves which can build up are discussed. The method of analysis is applied to a cylindrical grinding machine, and the results obtained are compared with those obtained from an experimental investigation.