bluuebunny/crossref_metadata_2025_split huggingface dataset:
Speed Characteristics of Hooke's Joint Transmissions
Authors: Maunder L. , Burdess J. S. 
Published: February 2007

A transmission consisting of three non-collinear shafts connected in sequence by two Hooke's joints is described. Each shaft has a specified moment of inertia, and power is transmitted from one end of the system to the other. Elastic and other deformations are neglected. A single differential equation governing the motion is derived, and is solved approximately by a method of small perturbations. The solution shows that at a constant mean speed the system will experience speed fluctuations which are complex functions of its dynamic parameters, including inertia and torque characteristics, as well as the more familiar kinematic parameters such as angularities of the joints. Special cases relating to constant speed conditions at chosen points in the system are assessed, and the effects of the significant parameters are illustrated numerically for a single-joint arrangement.
Creep Analysis of Smooth Curved Pipes under in-plane Bending
Authors: Spence J. 
Published: February 2007

Theoretical analyses are presented for the behaviour of a smooth circular cross-section thin-walled curved pipe of constant thickness when loaded by in-plane bending moments under isothermal creep conditions. Twin energy analyses, designated type 1 and type 2 respectively, are used in conjunction with an n-power stationary creep constitutive relationship. Approximate solutions are obtained by direct minimization techniques on a computer. Deformation results and stress-concentration factors relevant to the stationary condition based on straight-pipe values are reported for all practical geometries of pipe bends. The influence of the results on design and matters of total deformation and stress redistribution are briefly mentioned.
Some Results in the Erosion of Prestressed Materials due to Water-Jet Impact
Authors: Vickers G. W. , Johnson W. 
Published: February 2007

Two methods are described of applying uniaxial and biaxial tensile and compressive stresses to specimens subject to the erosive action of repetitive water jets which have speeds in the range 30–220 m/s. The influence which prestress has on erosion is examined in a ductile material, α-brass, and in a brittle material, Perspex. The behaviour of these materials contrasts sharply due to their different fracture modes. Also the values of prestress to impact stress ratio and the type of stress applied, are shown to have a bearing on results.
Torsional Stiffness of a Thin-Walled Beam Braced by Pinned or Rigidly Fixed Transverse Diaphragms
Authors: Harrison T. , Siddall J. M. 
Published: February 2007

The torsional stiffness of a thin-walled beam of open cross-sectional profile braced by evenly spaced transverse diaphragms is studied. Diaphragms rigidly fixed or attached by frictionless pins are treated and it is seen that, in either case, the only effect is to modify the St Venant torsional constant for the thin-walled beam. The theoretical work is supported by experimental evidence from two braced perspex channels which simulate the two assumed methods of attaching the diaphragms. Good agreement is demonstrated.
Cage Slip in Roller Bearings
Authors: O'Brien K. T. , Taylor C. M. 
Published: February 2007

The occurrence of cage and roller slip in lubricated roller bearings has been observed under adverse conditions of high speed and low load. Whilst slip is not normally a problem in roller bearings, in certain applications, for example the bearings supporting gas-turbine shafts, it can pose difficult design problems. For such conditions, bearing distress may occur due to increased wear and heat generation. A reduction of slip may be effected by the use of out-of-round races causing a preloading of some of the rolling elements; this, however, entails a corresponding reduction in fatigue life. Work described in this paper supplements the small amount of existing experimental evidence available concerning slip in rolling-element bearings. As well as a consideration of the effects of load and speed on slip, particular attention is paid to the quantity of lubricant supplied and the degree of misalignment present and the influence of these parameters on slip. Experimental results show a considerable divergence from previous results obtained using a similar bearing.
The Application of a Finite Element Method to the Evaluation of oil Whirl Characteristics
Authors: Shelly P. , Ettles C. 
Published: February 2007

A method using finite elements for the whirl analysis of plain bearings is outlined. The special properties of an exponentially shaped element are linked to a parabolic type of approximation for the axial pressure profile. The method is developed and applied to the prediction of whirl paths of a heavy rotor operating both in the horizontal and vertical modes. Several locus paths are presented to show the separate and combined effects of rotor unbalance and unidirectional loading over a range of rotational speeds.
The Effectiveness of the Impact Damper with a Spring-Supported Auxiliary Mass
Authors: Thomas M. D. , Sadek M. M. 
Published: February 2007

This paper examines the effect of a spring-supported impact mass on the performance of an impact damper. This technique was developed after it was found that gravity detracts from the performance of a normal impact damper. The springs are used to support the impact mass at the mid point of its stroke so that the effect of gravity is negated. The analysis presented in this paper is based on the assumption that the motion of the impact mass is stable and that there are two impacts in each cycle. The assumption that the impacts are equi-spaced is not made, and it is shown that such behaviour occurs very rarely in the resonant region. Theoretical predictions are verified experimentally, and the analysis is then used to develop design charts for the impact damper at various damping ratios, mass ratios and gap ratios. It is shown that the spring is detrimental to the performance of the damper if gravity is not present, but that the performance under gravity is improved to that of the device without gravity. It is shown that very light supporting springs make the accuracy required in centring the impact mass too high, so that the performance in practice increases with spring stiffness. The performance of the device at natural frequency ratios greater than 0.5 is not studied.
The Effect of Silencers of the Helmholtz-Resonator Type on Pressure Waves of Finite Amplitude: Single Pressure Pulses
Authors: Trengrouse G. H. 
Published: February 2007

The attenuation of large-amplitude waves effected by silencers of the so-called Helmholtz-resonator type is envisaged as being due to the finite efflux of gas through the holes of the silencer with resulting partial reflection, and hence reduced transmission, of the incident wave. Quasi-steady, one-dimensional flow arguments are used to predict the attenuation, the flow conditions being assumed reversible and adiabatic, that is, isentropic. This latter assumption is avoided in an alternative method by assuming a knowledge of the relationship between pipe Mach numbers and the pressure difference in the pipe across the holes. Indicator diagrams resulting from single pulse experiments are, in general, in good agreement with those predicted.
Reference Stress for Structures Obeying the Prandtl and Dorn Creep Laws
Authors: Johnsson A. 
Published: February 2007

The extraction of a reference stress for a given structure from an arbitrary two-parameter creep law is demonstrated. The technique is applied to a two-bar structure and a beam section subjected to pure bending. The material is assumed to follow creep laws of the form and . Resulting errors in deformation rate are compared for the different creep laws and with results obtained from a Norton law.
Transient Thermal Stresses in the Quarter-Plane and their Relation to the Thermal-Cracking of Cutting Tools
Authors: Thomason P. F. 
Published: February 2007

The transient thermal stresses in an insulated quarter-plane, subject to an instantaneous heat source on a segment of the surface, are determined with the aid of the Green's function for a two-dimensional infinite space. Numerical results for the transient thermal stresses at the surfaces of the quarter-plane are superimposed on previous isothermal results for cutting-load stresses in a π/2 wedge, to provide a model for a metal-cutting tool in the transient stages of a cutting process. The results are related to the problem of the thermal-cracking of cutting tools, and mechanisms of crack nucleation and propagation are proposed for both ceramic and cemented-carbide tools.
Oil Film Thickness in Lightly-Loaded Roller Bearings
Authors: Bahadoran H. , Gohar R. 
Published: February 2007

The effects of speed, load and roller geometry on the oil film thickness and shape in a complete roller bearing are demonstrated experimentally by means of optical interferometry. At quite moderate roller speeds, increase of film thickness becomes inhibited. This effect is attributed to a truncated inlet meniscus, a similar condition having been observed elsewhere with a ball-and-plate machine and with a model of a tapered-roller thrust bearing.
Buckling under External Pressure of Cylinders with Toriconical or Pierced Torispherical Ends: A Comparison of Experiment with Theory
Authors: Aylward R. W. , Galletly G. D. , Moffat D. G. 
Published: February 2007

Experimental buckling pressures are given for some thin cylindrical shells closed by two types of end closure. These were (a) unpierced toriconical shells and (b) torispherical shells penetrated by axisymmetric flush cylindrical nozzles. The loading investigated was uniform external pressure and all the shell combinations were machined and stress-relieved. The theoretical elastic buckling pressures corresponding to the above models were calculated using a digital computer program known as BOSOR 3, which is based on the variational finite-difference technique. This program calculates, for perfect elastic segmented shells of revolution, the asymmetric (i.e. with circumferential waves) bifurcation buckling pressures and also the large-deflection axisymmetric collapse pressure. In the asymmetric elastic case, both linear and non-linear pre-buckling stress resultants may be utilized. For the five cylinders with toriconical end closures, the buckling failures were always elastic and the agreement between theory and experiment was good. For the six cylinders with pierced torispherical ends, failure was by asymmetric buckling, in the n = 1 mode. For most of these cases there were significant discrepancies between the experimental results and the predictions of elastic buckling theory. However, better agreement between theory and experiment was obtained when a more recent version of the BOSOR program, which considers elastic/plastic effects, was utilized. Two limited comparisons, which should be of interest to designers, are also given. One comparison deals with the buckling resistance of a cylinder with either a toriconical or a torispherical head; the other considers the effect on the experimental buckling pressure of a cylinder/torisphere combination of piercing the torispherical head.
Flutter of Conservative Systems of Pipes Conveying Incompressible Fluid
Authors: Paidoussis M. P. 
Published: February 2007

An examination of the dynamics of beam-like motions of pipes conveying fluid, with both ends clamped, is presented by means of beam theory and, in the case of thin-walled pipes, by thin-shell theory. Both theories predict that the system loses stability by divergence at sufficiently high flow velocity, and that at higher flow velocity the system is subject to coupled-mode flutter; between the two instabilities there is sometimes a region where the system is completely stable. The critical flow velocities obtained by beam theory and by shell theory are compared, and it is shown that the former coverage towards the latter as the length of the pipe increases. Finally, the existence of coupled-mode flutter in gyroscopic conservative systems, such as the one investigated here, is briefly discussed.
Simple Approximate Treatments of Certain Incompressible Duct Flow Problems Involving Separation
Authors: Matthew G. D. 
Published: February 2007

Many examples of abrupt conduit change, for example, sudden or gradual contractions, mitre bends etc., have been treated by free-streamline, potential flow theory in conjunction with the classical Borda result for sudden expansion loss. These analyses have provided results which show moderate but rarely close agreement with experimental evidence. Here a fresh and simpler look is taken at such problems, on the basis of radical simplifying assumptions about the flow geometry and pressure distribution. It is demonstrated that direct application of the linear momentum equation, in association, where appropriate, with the Bernoulli equation, can yield results for head loss and contraction coefficients which are in consistently good agreement with experimental data (especially as far as head loss is concerned). It is shown in passing that these simplified arguments can even be used to provide a satisfactory approximation to the profile of a contracting jet, suggesting wider applications of the method in more complex geometrical situations. The analysis is advanced in a teaching context to illustrate the power of momentum and energy methods in providing immediately useful solutions to certain problems involving abrupt change.
Influence of Mean Stress Intensity on Fatigue Crack Growth in an Aluminium Alloy
Authors: Branco C. M. , Radon J. C. , Culver L. E. 
Published: February 2007

The effects of the mean stress-intensity factor, Km, and the range of the stress intensity, Δ K, on crack propagation phenomena in the Al-alloy RR 58 have been studied using contoured double-cantilever beam specimens providing a constant stress-intensity factor for all crack lengths. Based on the experimental data available, a relationship of the following form, between the cyclic crack growth rate, d a/d N, and the tensile loading levels, has been proposed: where Δ K = ( Kmax - Kmin); Kmax, Kmin and Km are the maximum, minimum and mean values of the stress-intensity factor; Δ Kth is the threshold value of Δ K for crack propagation; K1C is the critical fracture toughness in plane strain conditions; A and α arc constants. In tests at room temperature (21 °C) in laboratory air and at a loading frequency of 0.15 Hz, it was found that Δ Kth decreased with increasing values of K m, α was equal to 1.36 and A equalled 3.16 times 10-5(in/cycle).
Generalized Reynolds Equation for Stochastic Lubrication and its Application
Authors: Christensen H. , Shukla J. B. , Kumar S. 
Published: February 2007

By using the theory of a stochastic process, a generalized form of Reynolds equation applicable to rough bearings is derived by assuming the fluxes to be represented by power series of a stochastic film-thickness function. In the case of a step slider bearing, it is shown that load capacity and friction force increase but that coefficient of friction decreases as roughness parameter increases. Similar results are true in the case of a hydrostatic bearing. Further, in this case, good agreement between this theory and the sinusoidal approach is illustrated by suitably choosing the roughness parameter.
A Pseudo Three-Dimensional Analysis of Flows in Vaneless Diffusers for Mixed-Flow Compressors
Authors: Wallace F. J. , Atkey R. , Whitfield A. 
Published: February 2007

A solution is given of the equations of motion for inviscid flow with axial symmetry in mixed-flow diffusers of any given geometry. The associated computer programmes have been applied, together with similar programmes for the impeller based on streamline-normal solutions, to predict streamline, velocity and pressure distributions in a variety of vaneless diffusers as follows: (i) radial-flow impeller with radial diffuser; (ii) mixed-flow impeller with pure conical diffuser and (iii) mixed-flow impeller with curved diffusers. The first of these is shown to give essentially stable flow, the second extremely unstable flow and the third conditionally stable flow provided that a suitable combination of initial contraction and hub/shroud profile is adopted.
On the Equations Governing the Free and Forced Vibrations of a General Non-Conservative System
Authors: Wahed I. F. A. , Bishop R. E. D. 
Published: February 2007

An expression is derived for the steady forced response of a system governed by the equation in which A, B and C are real but not symmetric. The theory is effectively an adaptation and exploration of previous work by Woodcock (1)‡. His studies were published in the ‘Hamiltonian’ form, while in the present paper the Lagrange approach is used.
Compressor-Diffuser Interaction with Circumferential Flow Distortion
Authors: Greitzer E. M. , Griswol H. R. 
Published: February 2007

An analytical and experimental study of axial compressor-diffuser interaction in circumferentially non-uniform flow is reported. An analysis of non-axisymmetric flow in an annular diffuser is presented, based on an inviscid rotational core flow plus the use of a diffuser effective area ratio to account for boundary layer blockage. The analysis is applied to the prediction of the diffuser flow field associated with the presence of a circumferential total pressure distortion. It is found that large static pressure non-uniformities can exist at the inlet of diffusers that are short compared with their mean circumferences, as is usually the case in turbomachinery applications. The analysis is coupled to an asymmetric compressor flow field prediction to provide a method for calculating the effect of an exit diffuser on compressor performance with distortion. It is shown that the velocity defect seen by the compressor can be substantially increased by the presence of the diffuser. The experiments were directed at assessing the method used to predict the flow in the diffuser. Measurements were carried out of the inlet static pressure distortion associated with a circumferentially non-uniform total pressure distribution. The results are found to be in good agreement with the theoretical predictions.
The Distortion and Buckling of Long Viscoelastic Cylinders in Pure Bending
Authors: Croll S. G. 
Published: February 2007

The behaviour in pure bending of moderately thick polypropylene cylinders is examined. The distortion into an oval cross-section is measured as the bulging and flattening displacements. The bending radius at buckling is also determined. When compared with an existing theory for thin-walled Hookean cylinders both the distortion and buckling are found to be functions of a single reduced parameter involving the tube dimensions and the bending curvature, as predicted. However, the amount of distortion and the buckling radius are both less than the theoretical values. These discrepancies are explained by the mechanical nonlinearity of polypropylene.
A Qualitative Evaluation of Phenomenological Creep Rupture Theories
Authors: Westlund R. 
Published: February 2007

Predictions of the creep rupture lifetime under constant uniaxial tensile load according to various theories are compared. Both purely ductile and purely brittle rupture mechanisms are included as well as some recently proposed combined mechanisms of failure. One of these latter mechanisms is shown to yield results which describe quite well the dependence of the creep rupture lifetime on load in the entire region from instantaneous, usually rather ductile, rupture at high loads to long delayed, usually rather brittle, creep rupture at smaller loads.
On the Pressure Distribution between Stock and Rolls in Ring Rolling
Authors: Mamalis A. G. , Johnson W. , Hawkyard J. B. 
Published: February 2007

The technique of incorporating pin-type pressure transducers into the rolls and accurate measurements of the normal pressure are reported for various rolling parameters when rolling plain and profiled rings. Experiments have been carried out using tellurium lead at room temperature to obtain quantitative information about pressure distribution relevant to hot rolling, i.e. when frictional effects are pronounced. The results indicate that, in contrast to conventional strip rolling, the normal pressure distribution in ring rolling shows an early peak soon after the entry plane.
A Study of the Lubrication and Dynamics of Geometrically Perfect, Lightly Loaded, Cylindrical Roller Bearings with Particular Reference to Shaft Loci
Authors: Markho P. H. , Dowson D. 
Published: February 2007

The principal objective of this paper is to ascertain and quantify the cyclic movement of the centre of a shaft in a geometrically perfect, lubricated, cylindrical roller bearing exhibiting initial clearance and subjected to a light and steady load. The movement may be important in relation to the accuracy of location of shafts in roller bearings, and it is shown that a detailed consideration of the rolling element assembly predicts some interesting effects. The study also covers more conventional features of bearing performance such as lubricant film thickness and coefficient of friction, and shows the effect of squeeze to be negligible under steady bearing loads.
A Technique for Accelerating Block Load Fatigue Programmes
Authors: Power E. M. 
Published: February 2007

Recent improvements in cycle counting methods have increased the value of the block load programme as a method of simulating the fatigue damage caused by random service loading. It has already been observed that some of the lower load levels in certain block programmes make insignificant contributions to the total fatigue damage, and that the elimination of such levels can provide a very valuable method of accelerating tests. This paper presents further evidence in support of this observation, and proposes an analytical method by which the damage significance of each block may be predicted, thus enabling a rapid selection of those levels which may be safely omitted.
In-Plane Torsion Testing of Sheet Metal
Authors: Sowerby R. , Tomita Y. , Duncan J. L. 
Published: February 2007

In this paper, the ‘in-plane’ torsion testing of sheet metal is examined. The test itself was first proposed by Marciniak in order to ascertain the work hardening behaviour and fracture strain of sheet metals. In the original work, the analysis was based on the assumption that the material was rigid-work hardening. The present work attempts a more rigorous solution, assuming the material to be elastic-work hardening. A finite-element approximation is employed to calculate the stress and strain distribution across the sheet metal annulus at various stages in the deformation process. A comparison is made between the results from the finite-element method and those based on a rigid-work hardening material. For certain annulus geometries, excellent agreement is obtained between both sets of results.
Waterhammer in Non-Rigid Pipes: Precursor Waves and Mechanical Damping
Authors: Williams D. J. 
Published: February 2007

When a pipe can move, waterhammer effects are altered by the existence of precursor waves, i.e. longitudinal elastic strain waves in the pipe walls, modified by the presence of the fluid. Theory and experiment show that precursor waves cannot be ignored, if the effect of longitudinal strain is to be considered; conventional waterhammer theory is thus unsatisfactory. Flexural waves may also occur. It was found experimentally that pipe motion caused mechanical damping of the waterhammer–greater than the viscous damping. Viscoelastic piping also gave rise to strong mechanical damping, even without pipe motion.