bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Hydraulic Forces in Annular Pressure Seals on the Vibrations of Centrifugal Pump Rotors
Authors: Black H. F. 
Published: February 2007

In centrifugal pumps, the annular clearance spaces of the leakage path, i.e. impeller seals and balance piston seals, act as powerful hydrostatic bearings with turbulent flow. In the present discussion, the dynamic forces due to these bearings acting on the rotor are analysed, including the effect of squeeze action, i.e. the effect of velocities of separation or approach of the bearing and journal surfaces. Synchronous forced whirling is analysed in a simple idealization comprising a single mass rotor, including the estimation of amplitudes as well as critical speeds. Large damping forces due to squeeze action are found, in qualitative agreement with experimental work by Marcinkowskij and Karincev (3)†. A simplified treatment of the effects of fluid rotation is included in the analysis of rotor vibrations, leading to an analysis of high speed whip instability onset.
Optimization of Vibration Absorbers: Application to Complex Structures
Authors: Stone B. J. , Andrew C. 
Published: February 2007

This paper describes a method for designing a vibration absorber, incorporating polymer spring/damping elements, for attachment to a complex main system. The point of attachment can be remote from the position(s) of interest in the main system, for which any characteristic of absolute or relative receptance can be considered. Tests on a machine tool show that butyl rubber provides an effective and convenient damper material, even with main systems already possessing a high level of vibration damping, and that the addition of an absorber can effect a considerable improvement in the predicted performance of the machine. The addition of more than one absorber is likely to provide greater improvements.
A Simplified Presentation of Equations for the Thermodynamic Properties of Dichlorodifluoromethane, CCl2F2 (Refrigerant-12)
Authors: Haywood R. W. 
Published: February 2007

The paper commences with a general treatment illustrating the advantages of writing the equation of state of a pure substance in characteristic (canonical or fundamental) form, from which expressions for all other thermodynamic properties can be written down in terms only of the characteristic function and its partial derivatives. In this way, thermodynamic consistency between the equations for the different properties is automatically ensured. The initial difficulties in constructing an equation of state in characteristic form are briefly discussed, and it is shown how the characteristic equation may be built up from an existing p-v-T equation of state and an equation for the specific heat capacity at zero pressure. An existing set of equations for the single-phase region of Refrigerant-12 is transformed in this way into a single characteristic equation of state from which, through given simple expressions, all other thermodynamic properties may be computed. The equation of state is expressed dimensionlessly in reduced co-ordinates so that it may be used with equal facility in any coherent system of units. For the sake of completeness, other existing equations for the saturation pressure and for the saturated liquid have been put into dimensionless form and are given in the paper.
Thermal Conductivity of Steam at Atmospheric Pressure
Authors: Brain T. J. S. 
Published: February 2007

In this paper work carried out by the author to measure the thermal conductivity of steam at atmospheric pressure in the temperature range 100-700°C is reported. This work was undertaken in view of the discrepancies which exist in the experimental data at atmospheric pressure. In particular, the serious differences which exist at the high temperatures between the results of Russian experimenters, who give higher values than those given by American and German workers, needed investigation. Utilizing two concentric cylinder cells an absolute steady state method has been used to measure the thermal conductivity of steam in the temperature range 100-700°C, at atmospheric pressure, with a probable accuracy estimated to be within ± l·5-±2 per cent. The results obtained confirm Russian observations at the higher temperatures and it is hoped that these results will help finally to resolve the inconsistencies in the experimental data. A fresh assessment of all the experimental data is given by the author where arguments in favour of both the lower and higher atmospheric lines are discussed. A new correlation of experimental data has been undertaken and a reduction in the tolerances put on the equation defining the atmospheric line from ±3 per cent in the range 100-400°C and ±4 per cent in the range 400-700°C to ±2 per cent over the complete range 100-700°C is now recommended.
Acoustical Analysis Applied to Internal Combustion Engine Exhaust Systems of Conical Form
Authors: Nassif M. H. 
Published: February 2007

In the following analysis the variation of the charging capacity of a small two-stroke motor-cycle engine is utilized to assess the non-steady flow characteristics of conical exhaust pipes having different length and divergence. The performance of the engine under the most favourable conditions is applied to determine the natural frequency of exhaust ducts fitted with conical portions. The experimental data yielded are compared with theoretical computations based on acoustical treatments and inspection of the results obtained supports the conclusion that the ports behave as a partly, and not as a fully, closed end as commonly accepted.
Overcut, a New Theory for Tip Interference in Internal Gears
Authors: Polder J. W. 
Published: February 2007

For over forty years internal gears were surrounded by obscurity occasioned by the discovery of tip interference where calculation suggested that it would not occur (1)†. The present author developed a new theory for tip interference which gave better insight in the manufacturing process. Internal gears not satisfying rule (12) will be injured by the cutter at a centre distance still too low for involute generating. This injuring phenomenon in an early stage of cutting is called overcut. The overcut has to be neutralized by an increase of the tooth spaces to such an amount that the final generating centre distance is larger than existing theories suggested. When rule (12) is satisfied, then there is no overcut and no tip interference.
Expander Design in the Tube Expanding Process: The Influence of the Number of Rollers
Authors: Sukhawarn P. , Culver L. E. 
Published: February 2007

This paper describes tests which have been made to study the influence of the design of tube expanders on the characteristics of rolled joints. Of the various features of the propulsive type tool, that of the number of rollers was chosen as the point from which to start such an investigation. Three expanders, otherwise identical in all particulars but with three, five, and seven rollers were used and a series of tests were carried out with each tool to varying degrees of expanding. Comparisons are made of the values of push-out load, extrusion of the tube away from the front and back faces of the plate, mean seat pressure and hardness distributions in the tube plates. The results show that, judged on the maximum push-out strength, a three-roller expander makes the best joint, the strength falling as the number of rollers increases but there is no difference in the maximum value of mean seat pressure in joints rolled with the different expanders. The number of rollers also has a marked effect on the extrusion of the tube and on the extent of the plastic zones in the tube plates. Care is therefore necessary in selecting the appropriate criterion for optimum joint strength.
Holography as a Routine Method of Vibration Analysis
Authors: Hockley B. S. , Butters J. N. 
Published: February 2007

The application of holography as a routine method of analysing the vibrations in aero-engine compressor and turbine blades and discs is studied to overcome the disadvantages of the usual sand pattern and piezo-electric crystal contact probe methods. The Stetson-Powell time average fringe hologram technique of vibration analysis is used to investigate the nodal patterns of a 3-in and 6-in compressor blade together with those of a 10-in diameter turbine disc and the disc with a full set of blades. Two real time holographic methods of vibration analysis are also studied. The hologram system and apparatus are simplified to enable the normal methods of clamping the vibrating components to be utilized. A completely self-contained unit that is capable of both taking the hologram and photographing the reconstructed image has been developed. The unit is a box-like structure which is simple to operate and can be used in a normal inspection bay environment for objects up to 2 ft diameter.
Analysis of the Taper-Land Bearing Pad
Authors: Neal P. B. 
Published: February 2007

A computational analysis of hydrodynamically lubricated rectangular taper-land pads is presented. The geometrical parameters in the analysis are width/length ratio, land extent and film ratio. To permit assessment of the influence of variable viscosity, a linear decrease of viscosity along the pad length was provided for. Performance data have been derived for load capacity, friction, lubricant flow rate and operating temperature. Attention is given to the influence of hot lubricant carry-over from one pad to the next in a multi-pad bearing and accordingly two distinctly different situations, namely, isolated pad and compact bearing, are considered. Apart from the practical desirability of a land to carry any load under stationary conditions, it is shown that a short land is beneficial under operating conditions but that a land greater than about 0·3 of pad length is undesirable. An example illustrating the application of the data to bearing performance prediction is given.
Dynamic Stability of a Cantilever Boring Bar with Machined Flats under Regenerative Cutting Conditions
Authors: Parker E. W. 
Published: February 2007

The paper is concerned primarily with the stability of a slender boring bar which can be represented at the tool point by a simple two-degree-of-freedom, mass-spring-damper system. Its purpose is to determine how the vibration behaviour during machining is affected by coupling between modes. The stability behaviour is investigated for machining processes in which the cutting operation is of the regenerative type, when successive passes of the workpiece cause cuts to overlap. Account is taken of variations in certain system parameters, including the effect of workpiece speed, and results derived from practical cutting tests are described. Particular attention is paid to the effect on chatter-free machining performance of variations in the angle of setting of the boring head relative to the two planes of vibration. A theory is developed to apply the basic principles of the coupling mechanism over a wide range of conditions. Predicted changes in chatter characteristics are compared with experimental observations. Certain discrepancies arise between theory and practice, some of which can be resolved by re-assessing the initial assumptions for cutting forces.
Twisting and Bending of Thin-Walled Prismatic Beams of Open Cross-Sectional Profile
Authors: Harrison T. 
Published: February 2007

Previous studies of the behaviour, in generalized co-ordinates, of thin-walled, prismatic beams of open cross-sectional profile have included, explicitly, only the effects of distributed transverse forces, q x and q y, distributed longitudinal forces, q z, and distributed torsional couples, m z. Using the principle of virtual displacements, the work of previous investigators is extended to include, quite generally, the effects of the hitherto neglected distributed couples, m x and m y. The derivation of the differential equation relating to the twisting of an open-section prismatic beam is presented fully whilst those relating to transverse and axial displacements of cross-sections are merely stated. The kinematic and static boundary conditions for a cantilever are also established from the virtual work equations. These show that the free-end shear boundary condition associated with transverse bending which is usually adopted in engineering calculations is inadequate for such a generalized loading system.
Harmonic Wave Analysis of Vibration and Stress in a Longitudinally Reciprocated Bar
Authors: Beddoe B. 
Published: February 2007

The wave equation in one dimension approximately represents the longitudinal motion of a uniform bar that carries regularly spaced equal point masses. Fourier analysis is used to obtain the steady-state solution when the bar is reciprocated from one end. Distributed damping is considered. The more general system of unequal and irregularly spaced point masses on a bar consisting of sections of different mass per unit length is analysed in terms of reflection and transmission coefficients; a wave reflection method and a transfer matrix method are given for the solution of the problem of reciprocation. The limitation of the approximate equation of motion is assessed by examining wave dispersion in the uniform system. Application to ‘traverse bars’ on machines for winding extruded synthetic fibre was the object of the investigation.
Steady Compressible Flow through a Single Row of Radial Holes in the Wall of a Pipeline
Authors: Trengrouse G. H. 
Published: February 2007

Measured values of discharge coefficient for air flow through a single row of radial holes in the wall of a pipeline are reported, together with the values of pipe Mach numbers in the immediate vicinity of the holes. A wide range of pressure and area ratios are considered, the flow through the holes being either into or out of the pipe. It is shown that the effects on the measured values of both the pressure level at discharge from the holes and the air temperature are negligible. The agreement between the pressure change in the pipeline due to the holes, obtained experimentally, and that predicted by simple, one-dimensional flow theories is generally unsatisfactory. However, theoretical predictions of the jet efflux angles based on two-dimensional, incompressible, non-viscous flow arguments are in good agreement with those measured, but discrepancies do arise in the prediction of discharge coefficients.
Effect of Gravity on the Performance of an Impact Damper: Part 2. Stability of Vibrational Modes
Authors: Sadek M. M. , Williams C. J. H. 
Published: February 2007

This paper is c oncerned with the stability of the various modes of vibration of the impact damper system described in Part 1†. Charts are presented showing the ranges of dynamically stable and kinematically viable periodic two-impact-per-cycle motion. The condition of kinematic viability ensures that the trajectory of the free mass remains within the container throughout the motion. It is shown that in general stable, viable, two-impact-per-cycle motion of the system exists under resonant conditions of the main mass and that away from resonance, where any damper is ineffective, this type of motion is generally unstable.
Stability and Step Response of a Hydraulic Servo with Special Reference to Unsymmetrical Oil Volume Conditions
Authors: Martin K. F. 
Published: February 2007

This paper reports a theoretical and experimental evaluation of the stability and response of a hydraulic servomechanism used to position a mass when the oil volumes on the two sides of the jack are substantially different. Application of small perturbation theory to the closed loop system shows that the loop gain for marginal stability is least when the oil volumes are equal and that when these volumes are unequal the response of the system is governed by a fourth order differential equation. Predictions of marginal stability gain and of the step response are in good accord with measurements made on an experimental rig. A system with unequal oil volumes is shown to be inherently more stable and to have a faster but less oscillatory response than when the oil is equally distributed about the jack piston. Coulomb friction is accounted for analytically by a viscous friction energy equivalent. When the response approximates to a damped sinusoid it is shown that it is necessary to base the equivalent upon this response.
Analysis of ‘Boosted Lubrication’ in Human Joints
Authors: Dowson D. , Unsworth A. , Wright V. 
Published: February 2007

The load-bearing human joint is a self-acting dynamically loaded bearing which employs a porous and elastic bearing material (articular cartilage) and a highly non-Newtonian lubricant (synovial fluid). The authors' understanding is that the human joint experiences fluid-film (including elastohydrodynamic), mixed and boundary lubrication in its various operating conditions. It has been recognized that squeeze-film action is capable of providing considerable protection to the cartilage surface once a fluid film is generated (6) (8)§. Furthermore, the possibility of an increasing concentration of hyaluronic acid in synovial fluid during the squeeze-film action due to the porous nature of the cartilage and its surface topography and the known relationship between this concentration and the effective viscosity (7) has led to the concept of ‘boosted lubrication’ as an important feature of joint behaviour (10). A mathematical analysis of the concept of boosted lubrication of human joints is presented in this paper. The predictions of the analysis are shown to be in good agreement with experimental findings (12).
A Study of the Cross Flow Fan
Authors: Porter A. M. , Markland E. 
Published: February 2007

The cross flow fan has developed from the ideas of Mortier in the late 19th century and recently has been used with conspicuous success in small domestic appliances. No satisfactory theory is known, improvements having come from experimental development. The present work is also experimental. A closed-circuit fan test rig was constructed to obtain pressure, volume flow rate and efficiency for fans of various designs. Detailed measurements within the rotors were also obtained by hot-wire traverses. These tests were supplemented by visualization studies in a water test rig. It is found that improved pressure–flow characteristics are obtained by constructing the casing so that the vortex which forms in the fan is allowed to move circumferentially round the rotor as the output is throttled. This preserves a strong vortex and keeps the total pressure approximately constant as the flow is throttled. In many previous designs, which do not allow this kind of displacement, the vortex tends to move towards the centre of the rotor and to diminish in strength, leading sometimes to unstable operation.
Local Heat Transfer Measurements on a Gas Turbine Blade
Authors: Turner A. B. 
Published: February 2007

This paper presents an experimental method for determining the variation of the local heat transfer coefficient around gas turbine blades. The method involves the accurate determination of the distribution of metal surface temperature and the heat transfer coefficient and air coolant temperature in the internal cooling passages of the blade. It is shown that from the solution of Laplace's equation and a numerical differentiation at the blade surface of the resulting two-dimensional temperature field an estimate can be made of the normal temperature gradient in the metal which can be related directly to the local heat transfer coefficient at any point of the blade periphery. The results of experiments on a cascade blade undertaken to demonstrate the method are presented. These results show a clear laminar–turbulent transition on the convex surface of the blade but no transition, as such, is indicated on the concave surface. The magnitude of turbulence in the main stream is shown to have a very marked effect both on the mean level of heat transfer to the blade and on the local variation of the heat transfer coefficient.
Effect of Slenderness Ratio on the Natural Frequencies of Pre-Twisted Cantilever Beams of Uniform Rectangular Cross-Section
Authors: Dawson B. , Ghosh N. G. , Carnegie W. 
Published: February 2007

This paper is concerned with the vibrational characteristics of pre-twisted cantilever beams of uniform rectangular cross-section allowing for shear deformation and rotary inertia. A method of solution of the differential equations of motion allowing for shear deformation and rotary inertia is presented which is an extension of the method introduced by Dawson (1)§ for the solution of the differential equations of motion of pre-twisted beams neglecting shear and rotary inertia effects. The natural frequencies for the first five modes of vibration are obtained for beams of various breadth to depth ratios and lengths ranging from 3 to 20 in and pre-twist angle in the range 0–90°. The results are compared with those obtained by an alternative method (2), where available, and also to experimental results.
Analysis of the Hydraulic Jacking of Journal Bearings
Authors: Horlock J. H. 
Published: February 2007

An analysis is given for the flow in the clearance space between a shaft and its bearing, when the shaft is touching the bearing at its lowest point. Solutions are given for short and long bearings. The predictions of the analysis are compared with published experimental results. While the supply pressure required to lift a shaft off its bearing may be predicted accurately, the estimated flow rate is far less than that measured in experiments.
A Study of the Stability of a Plate-Like Load Towed beneath a Helicopter
Authors: Sheldon D. F. 
Published: February 2007

Recent experience has shown that a plate-like load suspended beneath a helicopter moving in horizontal forward flight has unstable characteristics at both low and high forward speeds. These findings have prompted a theoretical analysis to determine the longitudinal and lateral dynamic stability of a suspended pallet. Only the longitudinal stability is considered here. Although it is strictly a non-linear problem, the usual assumptions have been made to obtain linearized equations of motion. The aerodynamic derivative data required for these equations have been obtained, where possible, for the appropriate ranges of Reynolds and Strouhal number by means of static and dynamic wind tunnel testing. The resulting stability equations (with full aerodynamic derivative information) have been set up and solved, on a digital computer, to give direct indication of a stable or unstable system for a combination of physical parameters. These results have indicated a longitudinal unstable mode for all practical forward speeds. Simultaneously the important stability derivatives were found for this instability and modifications were made subsequently in the suspension system to eliminate the instabilities in the longitudinal sense. Throughout this paper, all metric dimensions are given approximately.
Biaxial Creep Testing
Authors: Wilson I. H. , Duncan J. L. , Johnson W. 
Published: February 2007

A new test for investigating biaxial creep in sheet metal is described. The specimen is a thin circular diaphragm clamped at the edge and deflected by lateral hydrostatic pressure. Stress and strain in the central region of the specimen are determined from measurements of pressure and of extension and curvature at the pole. An analysis of the time-dependent deformation of a circular diaphragm is presented and compared with experiments in which commercial purity aluminium sheet was tested in constant pressure tests at temperatures between 100 and 250°C. The biaxial creep data were compared with the results of uniaxial constant load tests, but no satisfactory correlation could be obtained. The results of constant pressure biaxial tests at different temperatures above 175°C could be correlated using the Zener–Holloman time parameter.