bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Replica Technique for Measuring Static Strains
Authors: Hickson V. M. 
Published: February 2007

A new technique for determining static strains in engineering specimens and structures is described. It is basically a direct-measurement method in that relative displacements of surface scratches are measured; the novel feature of the technique is the recording of scratch patterns by means of accurate replicas taken with the structure in the unloaded and loaded states, or after loading, and their comparison for the measurement of strains. Measurements of relative displacements on a replica pair may be taken to an accuracy of at least one micron by visual microscope techniques; this accuracy permits good determinations of low elastic strains over gauge lengths from 1/2 cm to 1 cm, and measurements of plastic strain over very much shorter gauge lengths. Replication is a quick process, being complete in one minute or less and the replicas have permanence of the order of months. Measurement of the replicas may be carried out under laboratory conditions, remote in distance and time from the test, if that is necessary. The replicas are compensated for temperature within certain limits, permitting successive replicas to be taken over long intervals without correction for variations in the ambient temperature. A description of equipment for application and measurement of replicas is given; some results defining the limitations of the technique are presented, and a discussion on systems of measurement and computation of elastic strains and plastic elongations is included. Examples of application to fields of elastic and plastic strain are quoted.
Effect of Compressibility on the Discharge Coefficient of Orifices and Convergent Nozzles
Authors: Bragg S. L. 
Published: February 2007

It has been known for some time that when a gas flows through an orifice the coefficient of discharge increases as the ratio of the downstream pressure to the upstream pressure is reduced (Stanton (1)).† This increase continues even after the critical (sonic) pressure ratio is passed, since, unless the discharge coefficient of the orifice is already unity, the mean velocity in the plane of the orifice is still subsonic and can be influenced by the downstream pressure. In a paper to this Institution, Jobson (2) suggested a method by which the variation of discharge coefficient with pressure ratio could be calculated. The method was based on the assumption that the velocity pattern at the walls, upstream of the orifice, was independent of flow rate: it yielded results that were in good agreement with experiments on sharp-edge orifices. The assumption breaks down, however, and leads to demonstrably false results, when the discharge coefficient is greater than about 0·65 and the pressure ratio well away from unity, since the upstream velocity pattern is then affected by compressibility. In the present paper, a simple assumption about the flow pattern at the walls enables allowance to be made for this additional compressibility effect. The resulting curves of discharge coefficient against pressure ratio are then correct for a perfect nozzle, with a discharge coefficient of unity, as well as for a Borda mouth-piece, and so might be expected to be reasonable approximations in between these extremes. Experimental results from a variety of sources have been compared with the theoretical predictions. The agreement is good at pressure ratios up to the critical but very few results at really low pressure ratios are available. It should perhaps be emphasized that neither Jobson's nor the present method of analysis enables the discharge coefficient of a particular orifice to be calculated ab initio. Their object is to predict how the discharge coefficient of a particular nozzle, known under one set of flow conditions, will vary under others. It is therefore to be hoped that the curves presented will prove particularly useful for design purposes, and for performance correlations.
Static and Fatigue Testing Machine for Rotor Discs
Authors: Dudley B. R. , Pope J. A. 
Published: February 2007

The need for a static and fatigue testing machine for aircraft rotor discs is shown and a suitable hydraulic loading machine is described. A description is also given of the design and development of a variable delivery pulsator for supplying pressure pulses to the hydraulic loading rig. The experimental technique is explained. Some of the differences between the method of test and operating conditions are discussed and photographs of two types of failure are included.
Dimensionless Kinetic Energy: A New Parameter for Gas Flow in Ducts with Application to Nuclear-Power Reactors
Authors: Patterson J. , Durrands K. J. 
Published: February 2007

The following analysis deals with steady, compressible, uni-directional gas flow in a duct with wall friction and axial heat addition. Adiabatic conditions are assumed at the outside wall, whilst the friction factor is taken as constant along the duct length. Theoretical results have been satisfactorily confirmed, in the case of uniformly distributed heating, by a series of experiments carried out on a steady-flow rig. A consideration of asymmetrical heat distributions leads to the concept of an equivalent concentrated heat source thereby establishing a relationship between heat input and overall pressure drop.
Estimation of Load and Torque in the Hot Rolling Process
Authors: Green J. W. , Wallace J. F. 
Published: February 2007

A shear plane theory of hot rolling is proposed, based on the well-known observation of localized deformation during the rolling process. Equations of simple form in terms of yield stress and geometric functions enable roll load and torque to be readily evaluated with or without tensions. Comparison with the experimental results of Wallquist suggests that the theory gives a more satisfactory indication of the influence of the R/h ratio on load and torque than does the Sims analysis. Equations are presented in four forms: the general case with tensions; the more common case without tensions; simplified equations which are valid for most practical conditions; and graphical functions for use with the Cook and McCrum yield stress data.
Heat Transfer in Channels Having Rough and Smooth Surfaces
Authors: Hall W. B. 
Published: February 2007

The author proposes a method of comparing the heat transfer coefficients in two channels in which (1) the cross-sectional shape is different; (2) there are different proportions of rough and smooth surfaces; (3) there are different proportions of heated and unheated surfaces. In particular the method applies to experimental results for the system in which a roughened, heated cylinder is placed centrally in a smooth unheated pipe. The effective diameter concept is used to allow for changes in shape, and the heat-transfer boundary conditions are modified to make them similar to the fluid-flow boundary conditions before the comparison is made.
Coupled Bending Vibrations of Pretwisted Cantilever Beams
Authors: Slyper H. A. 
Published: February 2007

The author describes a method of determining the vibrations of cantilever beams of non-uniform pretwist and cross-section. The known condition for orthogonality of normal modes for a beam in simple bending in one transverse plane is extended to that of coupled bending-bending modes of vibration in two transverse planes. This condition of orthogonality is then used in the Stodola process to determine the frequencies and modes of vibration for cantilever beams of uniform pretwist and cross-section. In this method the modes of vibration may be coupled or uncoupled. The resonant frequencies of the beam are determined in ascending order of magnitude and the modal patterns deduced without requiring any preliminary knowledge of the vibrational characteristics of the beam. It is considered that this is a considerable advantage on the alternative methods of solution. An analysis of experimental and theoretical results is made for three cantilever beams of uniform rectangular cross-section and angles of pretwist 0, 90·9 and 877° respectively. The frequencies and modal patterns of the first five modes of vibration were obtained experimentally and show good agreement with those calculated from the theory. The computed results for the first five frequencies are then given for a series of cantilever type beams in coupled bending-bending vibrations. The cantilevers considered had angles of pretwist from zero to 180° and were of uniform rectangular cross-section having breadth to depth ratios ranging from unity to 16. The calculated frequencies have been compared with known experimental results and show good agreement. It has also been shown that some of the larger errors may be anticipated for certain critical frequencies.
Screw Extrusion of Plastics
Authors: Weeks D. J. , Allen W. J. 
Published: February 2007

The main object of the work reported here was to find a rational design method for granule-fed single-screw extruders used for plastics processing. The first half of the paper contains a brief review of the literature on extrusion theory. Also the existing theory of Newtonian melt flow is extended to the granule-fed extruder and predictions of the behaviour of granule-fed machines are made. In addition the extruder flow equation for non-Newtonian ‘power law’ fluids is solved. In the second part of the paper are described experiments on polythene extrusion which demonstrate that qualitatively this non-Newtonian polymer behaves as predicted in the first part. An adequate correlation of flow results for the melt zones of the screws used is obtained, using an ‘apparent’ viscosity with a shear rate correction to allow for non-Newtonian behaviour. Outputs can be predicted within about 25 per cent using the design method recommended as a result of the work, but power consumption predictions tend to be low, and further attention must be given to that aspect.
Stresses in Plates with Polygonal Holes
Authors: Ross D. S. 
Published: February 2007

A multiple crack of four arms in an infinite plate in uniform tension is simulated by means of a ‘square’ hole with curved sides. The conformal transformation uses two terms, the decimal coefficient of the second term being determined by a function generator. The stress distribution due to such a discontinuity is obtained theoretically by derived complex potentials, the results being compared with stress values found by photoelasticity. Stress concentration factors are given for other discontinuities in the form of square and triangular holes, and cracks of three arms. Good agreement is shown to exist between theoretical and experimental results.
Investigation of the Response of an Hydraulic Servomechanism with Inertial Load
Authors: Lambert T. H. , Davies R. M. 
Published: February 2007

The linearized equations and transfer function for a hydraulic servomechanism are considered. It is shown that the simple first-order equation is inadequate to explain the behaviour of the device as observed experimentally. The solution of the third-order equation, obtainable by the inclusion of the effects of leakage and compressibility, provides a more accurate description of the behaviour. The theory is extended by means of an analogue computer to include the effects of Coulomb damping and to investigate the behaviour of the system when driven by a harmonic input. It is shown that the stabilizing effects of the Coulomb friction can be simulated by an equivalent viscous friction by increasing the leakage coefficient in the equations. The results of a series of experimental tests are included for comparison.
Plastic-Elastic Strains Observed near Loaded Fillets in Stepped Bars
Authors: Fessler H. , Wilson R. W. 
Published: February 2007

The photoelastic reflection technique has been used to study the strains in 10 different models, made of nickel-chromium-molybdenum steel. The shapes of the models were like very thick channel sections. Equal and opposite thrusts were applied to the inner edges of the (constant thickness) ‘flanges’. Calculated peak stress-measured peak strain curves were very similar for all models, although the elastic stress concentration factors varied from 2·2 to 6·2. The ratio (measured peak strain)/(strain if material were elastic) was approximately 1 at twice yield stress, 1 1/2 at three times yield stress and 2 1/4 at four times yield stress. The strain distribution across a section of the ‘web’ of the channel section is also presented for various loads.
Limit Pressure for a Protruding Cylindrical Nozzle in a Spherical Pressure Vessel
Authors: Dinno K. S. , Gill S. S. 
Published: February 2007

Using the one-moment limited interaction surface, an exact solution verified by obtaining coincident upper and lower bounds has been calculated for the limit pressure for a protruding cylindrical nozzle in a spherical pressure vessel. Using a particular mechanism configuration involving the sphere and the external part of the branch which covers a wide range of the parameters r/R, R/T and t/T, a comprehensive study of the effect of the internal protrusion has been made. Results of the limit pressure for a wide range of parameters are presented.
Response of Single-Pass Heat Exchangers to Disturbances in Flow Rate
Authors: Finlay I. C. , Dalgleish N. 
Published: February 2007

From distributed and lumped parameter models of a single-pass, shell and tube heat exchanger, transfer functions are derived relating the outlet-temperature responses to tube-side flow-rate disturbances. Predicted and measured data are compared over a range of mass flows and of amplitudes of the disturbing, tube-side flow signal. Good agreement is shown between measured responses and responses predicted by sectionally lumped and distributed parameter models for amplitudes of up to ±30 per cent of the mean value. The effects on the dynamic response of a distributed single-pass heat exchanger, of altering such characteristics as tube length, tube and shell-wall capacitance and mass flow rates, are illustrated graphically, and discussed.
Effect of Cold Work on the Thermal Conductivity of Copper
Authors: Williams A. 
Published: February 2007

Measurements were made of the thermal conductivity of each of five samples of copper rod which had been strained to different degrees by cold drawing. The measured thermal conductivity of the most highly strained sample (drawn to 50 per cent reduction of area) was about 11 per cent lower than that of annealed material. The flow of heat through a stationary metal-to-metal joint is inhibited by the reduced conductivities of the plastically deformed surface asperities forming the real contact points within the joint. The complex straining processes involved in the mating of asperities make it difficult to predict quantitatively the overall effect on a joint's conductance, but the reduced thermal conductivities may be partially responsible for the very low joint conductances previously attributed to changes in metal ‘hardness’.
Vibration of Rectangular Plates of Variable Thickness
Authors: Dawe D. J. 
Published: February 2007

In a previous paper the application of the finite element method to plate vibration problems was discussed. It was shown that the method gave good results when applied to the vibration of plates of uniform thickness. The present paper extends the method to include plates of variable thickness. In particular stiffness and inertia matrices are derived for an isotropic rectangular plate element of linearly variable thickness in one co-ordinate direction. These matrices are used to find the natural frequencies and mode shapes of a number of rectangular planform cantilever plates of non-uniform thickness. Experimental results provide a basis for comparison with the finite element results.
Theoretical Analysis of the Unsteady Gas Flow in the Exhaust System of an Engine
Authors: Wright E. H. , Gill K. F. 
Published: February 2007

The problem studied is that of unsteady gas motion in ducts of both constant and slowly varying cross-sectional area with the effects of wall friction and heat transfer taken into account. The values of the specific heats used in the analysis are those applicable to the instantaneous gas temperature at the instant under consideration, i.e. thermal lags are ignored. To solve the unsteady flow equations, a method is developed based on the theory of characteristics and in the application of this method a pure graphical approach is used for convenience. The plotting technique adopted is the ‘field method of solution’ in which it is assumed that a region of continually varying fluid properties can be broken into a large number of small regions for calculation purposes. The fluid properties are assumed uniform throughout each of these small regions and changes in the fluid properties can only occur across the boundaries or characteristics separating the small regions. With a firing engine, temperature discontinuities will be established at the interface of the hot gases being discharged from the cylinder and the cooler residuals from the previous cycle. Owing to the interaction of successive points of the fundamental pressure pulse with those resulting from the reflection of previous points of the fundamental pulse, sonic velocities can be encountered at the diffuser entry section. The formation of a steep front at the diffuser entry section as a result of these rarefaction waves can produce a shock wave. A method of solution for the existence in the flow of such discontinuities as temperature and shock is included. The general conclusions to be drawn are: (1) true application of the irreversible flow theory gives a good solution of the wave patterns occurring in both the cylinder and exhaust pipe of the engine; (2) the air mass flow can be predicted with good accuracy by application of the irreversible flow theory developed; (3) the poor correlation resulting from application of the isentropic flow theory shows caution should be exercised in the use of this simplified theory.
Dynamics of a Gyroscope Having Oblique Gimbal Axes
Authors: Crawley J. , Maunder L. 
Published: February 2007

The effects are considered of obliquity in the suspension axes of a free two-axis gyroscope supported in gimbals. Three principal types of obliquity are considered, namely (1) non-orthogonality of the bearing axes of the outer and inner gimbals, (2) non-orthogonality of the bearing axes of the inner gimbal and the spin axis of the rotor, in a plane Oyz defined by their usual orthogonal directions, and (3) misalignment of the spin axis of the rotor and a principal axis of the inner gimbal, in a direction out of the plane Oyz. Such obliquities or misalignments could occur as a result of manufacturing errors or they might be introduced deliberately in order to obtain particular dynamical characteristics. The free motion of the system is shown to be described by two coupled second-order non-linear equations, which are solved to first and second approximations for the three cases in which misalignment occurs separately. The first approximation determines the nutational vibration and the second the drift rate. Both are shown to be affected by each type of misalignment: the nutation varies in frequency and mode, and the drift rate in magnitude but not in direction. The relations between misalignment of the spin axis and dynamic unbalance of the inner gimbal are also discussed.
Comparison of Unsteady Flow Discharge Coefficients for Sharp-Edged Orifices with Steady Flow Values
Authors: Trengrouse G. H. , Imrie B. W. , Mal D. H. 
Published: February 2007

A simple theory, based on quasi-steady, one-dimensional flow arguments, is presented for the reflection of a compressive wave in air in a pipe when incident upon a coaxial, convergent nozzle situated at the end of the pipe. Preliminary shock-tube experiments using quadrant arc nozzles confirm the validity of the theory, and thus enable it to be used to predict the discharge coefficients of sharp-edged orifices from pressure measurements taken in the pipe in the immediate vicinity of the orifices during further shock-tube experiments. Steady flow discharge coefficients measured experimentally differ from the unsteady flow values by a maximum of 7 per cent.
Aerodynamic Stability of Cylinders of Various Sectional Shapes Spanning an Airstream
Authors: de Bray B. P. G. , Holt D. L. 
Published: February 2007

Flexible or elastically supported cylinders (using the term in its more general sense to include bodies of any constant sectional shape, with a straight line axis) evince tendencies to oscillate when placed across an airstream. If oscillations are constrained to one degree of freedom about an axis parallel to the cylinder axis, stability can be predicted from the steady aerodynamic properties of the sectional shape of the cylinder, but only if the axis is remote and for conditions in which vortex shedding is absent. The best-known example of this is the criterion of den Hartog for pure plunging oscillations. This criterion is readily extended to the case of an axis remote in any direction; but for cases in which the axis is near, so that angular motion becomes appreciable, it is generally considered that non-oscillatory properties do not give a guide to stability. A theory for this case is developed for a thin flat plate, fully stalled, and its results are shown experimentally to be applicable to a range of section shapes, enabling stability to be assessed from simple measurements of the wake under steady conditions.
Experiments on Pipelines and Pipe bends Subjected to Three-Dimensional Loading
Authors: Smith R. T. , Ford Hugh 
Published: February 2007

The flexibility of a full-scale, three-dimensional, two-anchor pipeline has been investigated experimentally by measuring the end reactions resulting from controlled anchor movements. The results are compared with design calculations and show a satisfactory agreement. These tests were supplemented by experiments on individual pipe bends which were subjected to in-plane and out-of-plane bending while measurements were made of the resulting stresses, deflections and cross-sectional distortion. The results compared satisfactorily with calculations especially when these were modified to allow for variations of the flexibility factor.
Heat Transfer and Pressure Drop Measurements in Channels with Whitworth Thread Form Roughness
Authors: Furber B. N. , Cox D. N. 
Published: February 2007

The heat transfer and pressure drop performance of three 4-in nominal bore tubes internally roughened with Whitworth thread forms of 11, 24 and 60 threads per inch (t.p.i.) has been measured with the tubes empty and with a concentrically mounted smooth cylinder of 2·012-in diameter. The tube with the 24-t.p.i. roughness form was also tested with a concentric cylinder of 2·00-in diameter having the same geometric roughness. The measured Stanton number and friction factors of the annuli with the smooth inner walls have been transformed using a method suggested by Hall (1)†, and compared to the empty channel and completely roughened annulus data.
Elastohydrodynamic Lubrication of High Pressure Face Seals
Authors: Hooke C. J. , O'Donoghue J. P. 
Published: February 2007

A previous paper demonstrated that high pressure face seals have an inherent stiffness due to elastic distortions. At that time a simplified treatment of the elastic and thermal problems was presented and agreement between this theory and experimental results was found to be reasonable. Because of the predominant effect of the elastic distortions and their importance in determining the stability of a seal, the authors of this paper have determined a more accurate method of solution of the elastic problem. The results of this theory give closer agreement with the published results obtained experimentally, and demonstrate that the simplified treatment is valid only if the seal has a large face to thickness ratio. Solutions for square-section seals are presented in non-dimensional form, leakage and parting force due to fluid pressure being expressed as ratios of the rigid values. Although only one sealing arrangement is treated the elastic solution can be applied to any body symmetrical about an axis.