bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deformation of Uniformly Loaded Beams Obeying Complex Creep Laws
Authors: Anderson R. G. , Gardner L. R. T. , Hodgkins W. R. 
Published: February 2007

The deformations of uniformly loaded, simply supported beams are derived for a simple creep law of the type where is the secondary creep rate, ρ is the applied stress and n is the creep index. The solution is extended to include a yielding behaviour such that ρ ≥ Y where Y is a yield stress. The deformations are found to be relatively insensitive to the value of n so long as the strain rate is known at a ‘representative stress’ in the beam and the representative stress is less than about 95 per cent of the yield stress. The concept of representative stress is used to estimate useful upper and lower bounds for the deformations of a simply supported beam composed of a material with a complex creep law in which the stress index n is continually increasing with increasing stress. Similar results for cantilevers and clamped beams suggest that the representative stress concept is useful for the solution of many problems involving deformations under complex creep laws or for problems in which a minimum of creep information can be obtained.
Analysis of Turbulent Bearing Films
Authors: Reynolds A. J. 
Published: February 2007

In studying the performance of laminar bearing films one need give little attention to the details of the internal flow. The velocity distribution is so simply related to the pressure gradient that one is able almost immediately to concentrate on the pressure distribution. But for a turbulent film the situation is quite different. No simple laws are known relating the volume flow through the film to the pressure gradient and relative velocity. A thorough study of the motion within turbulent films must be made before their characteristics as bearing films can be assessed. Thus this work falls into two parts. In Part I the basic analysis of two-dimensional turbulent channel flows is given. The application of its results to bearing analysis is treated in Part II.
Transient Response of an Hydraulic Servomechanism Flexibly Connected to An Inertial Load
Authors: Davies R. M. , Lambert T. H. 
Published: February 2007

The transient response of a powerful hydraulic servomechanism, flexibly connected to an inertial load is investigated theoretically and experimentally. The results indicate that a linearized fifth-order transfer function, taking into account inertial load, compressibility, leakage, and structural flexibility and damping, gives a reliable indication of the main characteristics of behaviour of this type of control in such a realistic environment. Extension of the theory to include the effects of the principal non-linearity, Coulomb friction, by simulation on an analogue computer increases the viability of the analysis. It is found that the response is of an oscillatory, biharmonic character; the low-frequency component of which is attributable mainly to effects external to the jack and the high-frequency component to internal effects. Consistently, it is found that the subsidence ratio of the former is sensitive to structural damping and of the latter to Coulomb friction and leakage.
Analysis of the Cup-Drawing Process
Authors: Woo D. M. 
Published: February 2007

An analysis has been developed for the study of the cup-drawing process which includes radial drawing over a die and stretch-forming over a punch. Theoretical results were obtained on a Pegasus computer. The analysis for radial drawing has been limited in this investigation to the case of drawing with a pressure blank-holder although similar analysis can also be made for the case of drawing with a clearance blank-holder. For the brass and mild steel used, the agreement between the theoretical and experimental results is generally satisfactory. In the analysis of stretch-forming over a punch head, two cases were considered: one for a 4-in diameter flat-headed punch with 1-in profile radius and the other for a 2-in diameter spherical-headed punch. The material used was brass. Theoretical strains based on simplified conditions in stretch-forming were obtained and compared with the experimental results. Agreement is good between the theoretical and experimental circumferential strains but the correlation between the thickness strains is unsatisfactory. For possible improvement in the theoretical results, a more exact analysis has been suggested.
Quasi-Theoretical Method for Calculating the Rigidity of Multi-Pass Tube Plates
Authors: Duncan J. P. 
Published: February 2007

Tube plates of heat exchangers often consist of circular elastic plates into which tubes are secured by welding or swaging. The holes in the plate into which the tubes are fixed are arranged in zones within the outer boundary of the plate to suit the nesting of the tubes. Such tube plates are flexed principally by a hydrostatic pressure differential. In this action they function as many-times multiple-connected elastic plates and exact analysis is greatly complicated by the many internal boundaries. Since such boundaries are normally grouped in the form of zones of regularly arrayed, identical and uniformly pitched holes, the notion of ‘equivalent elastic constants’ as discussed in a related paper, reference (6), can be used to describe the average behaviour of such drilled zones. The number of significant internal boundaries can thus be reduced to the number of zones corresponding with the number of nests of tubes, usually two or four. The boundaries of the nests usually possess symmetries about the diameters of the plate. Using this fact together with the notion of equivalent elastic constants a method is developed in both detailed and simplified form for predicting theoretically, through an integral equation, the flexural behaviour of characteristic types of tube plate with encastré and simply supported boundaries. These theoretical methods were tested experimentally on several models whose behaviour was recorded by means of interferometry. Agreement between theory and experiment was established within acceptable limits.
Creep of Metallic Thick-Walled Cylindrical Vessels Subject to Internal and External Pressure and Torque at Elevated Temperatures
Authors: Johnson A. E. , Khan B. 
Published: February 2007

A theoretical analysis has been made of the distribution of stress and strain in metallic thick-walled cylindrical pressure vessels, subject to internal and external pressure., and also to a torque, at elevated temperatures. The analysis deals with the general case where creep strains and elastic strains occurring as a result of the applied pressure and torque are both of significant order. Some practical figures are given.
Shear Plane Theories of Hot and Cold Flat Rolling
Authors: Green J. W. , Sparling L. G. M. , Wallace J. F. 
Published: February 2007

The shear plane theory of hot rolling of thick stock, due to Green and Wallace, is extended to hot and cold flat rolling. Values calculated from the hot rolling theory compared satisfactorily with the theory of Sims and the experimental results of Wallquist. The cold rolling theory is similarly satisfactory in comparison with the experimental results of Ford and it is anticipated that the theory will be more accurate than that of Bland and Ford for small R/h ratios and large reductions. Examples of calculation of load and torque for rolling are given in Appendixes for both Coulomb friction and sticking and shearing at the metal surface and it is shown that both conditions may occur and be taken into account concurrently. A method of determining the total torque is given which is derived from an upper bound to the work done on shear planes which are shown to have the same configuration as that chosen in the analysis of forces.
Use of Upper Bound Solutions for Predicting the Pressure for the Plane Strain Extrusion of Materials
Authors: Halling J. , Mitchell L. A. 
Published: February 2007

An upper bound solution, based on a kinematically admissible velocity field, is proposed for plane-strain symmetrical extrusion through wedge-shaped dies. The pattern chosen consists of a double-triangle arrangement of velocity discontinuities and the solution was optimized using a digital computer programme. Analysis of the results for a full range of die angles, reductions and frictional conditions provides useful predictions relating to the formation of dead zones. Such an analysis is given in detail for a 90° die. The results obtained compare favourably with the predictions of analytical slip-line field solutions in the regions where such solutions are available. The solution is also extended to accommodate the strain-hardening characteristics of the material. These results show that the alternative mean strain hypothesis is prone to errors in the presence of friction. This solution also yields an indication of the nature of the hardness distribution across the extruded product with particular reference to the effects of die geometry and reduction in area.
Effects of Temperature Rise on the Flow of a Viscous Liquid through a Concentric Annulus with an Inner Cylinder Rotating
Authors: Newbery L. A. 
Published: February 2007

An exact solution is presented for the forced flow of a viscous liquid through a concentric annulus in which the fluid temperature is increased and the viscosity decreased by rotation of the inner boundary. Such a solution has not previously appeared in the published literature. Some practical applications are mentioned.
A Finite Element Approach to Plate Vibration Problems
Authors: Dawe D. J. 
Published: February 2007

A method of computing the natural frequencies of vibration of flat plates of arbitrary shape is outlined in which the plate is considered as an assemblage of elements. Both stiffness and inertia matrices are derived for a rectangular isotropic plate element of uniform thickness, and these matrices are used to find the natural frequencies of square plates subject to various boundary conditions. Comparison of finite element frequencies with known exact, experimental and energy solutions shows the method to give good results even for relatively few elements.
Wave Theory of Free Torsional Vibration of Composite Systems of Shafts
Authors: Beddoe B. 
Published: February 2007

This paper gives a general theory of free torsional vibration of systems in which allowance is made for both elasticity and inertia of each component shaft. The governing equation of motion is the elementary wave equation in one dimension and the problem is solved by wave methods that use the concepts of reflection and transmission. Both the frequency equation and the equations of modal shape are derived in terms of defined reflection and transmission coefficients. The theory is illustrated by two examples that include stepped shafts, rigid discs, a light elastic coupling and shafts connected by rigid gears.
Vibration of a Spring-Supported Body
Authors: Grootenhuis P. , Ewins D. J. 
Published: February 2007

The equations of motion for a rigid body supported on four springs are derived for the general case of the centre-of-gravity being anywhere within the body and allowing for the sideways as well as the longitudinal stiffnesses of the springs. This constitutes a six-degrees-of-freedom case with three degrees of asymmetry. Coupling between motions in all directions occurs even when the centre-of-gravity is at the geometric centre with the exception then of vertical oscillations and rotation about the vertical axis. Any number of additional springs can be allowed for by adding terms to the expression for the potential energy stored in the springs. Allowance is made in the expression for kinetic energy for the products of inertia which arise with an offset centre-of-gravity. The real case is simulated for purposes of analysis by replacing the rigid body by a rectangular box with a light framework and all the mass concentrated at the eight corners. The matrix solution is changed into dimensionless parameters and the effect of an offset centre-of-gravity upon the eigenvalues and eigenvectors studied. Only the proportions of the box and the stiffness ratio between sideways to longitudinal stiffness of the springs remain as factors. The numerical example given is for proportions of height to width to length of 3/4/5 and for a stiffness ratio of 5. Small amounts of offset of the centre-of-gravity from the geometric centre do not alter the dynamic behaviour of the system much but displacing the total mass towards either a lower or an upper corner has marked effects. Some of the natural frequencies associated with motion in rotation when the system is symmetric become less than the frequencies connected with motion in translation for the centre-of-gravity being close to a corner connected to a spring. A large region free from any natural frequency arises when the centre-of-gravity is moved towards a corner furthest removed from the plane containing the springs. The asymptotic conditions for the position of the centre-of-gravity are also considered.
Creep Rupture of Ductile Materials under Variable Load
Authors: Singer J. 
Published: February 2007

Hoff derived expressions for the creep rupture time when the creep deformations are governed by the Norton-Bailey law, which yielded results in agreement with experiments for pure aluminium and some aluminium alloys. He later extended the analysis for other creep laws. The author has extended Hoff's analysis for a constant load to a load which varies with time, the material being considered incompressible. Several suitable examples have been considered.
Discharge Coefficients for Incompressible Non-Cavitating Flow through Long Orifices
Authors: Lichtarowicz A. , Duggins R. K. , Markland E. 
Published: February 2007

The results of a number of previous investigations of the discharge characteristics of parallel-bore orifices with length/diameter ratios up to 10 and Reynolds numbers up to about 105are collected and discussed, together with new data which extend to Reynolds number as low as unity. Simple empirical expressions, which fit the data well, are suggested for design purposes.
Thermodynamic Testing of Turbines and Pumps
Authors: Thom A. S. 
Published: February 2007

Hydraulic losses experienced by fluids in passing through machines effectively raise the temperature. The thermodynamic method of testing is basically a way of determining these losses by measuring temperature rise. When pressure change through a machine is measured along with temperature, the enthalpy change is known and the hydraulic efficiency can be evaluated. Knowledge is necessary of certain thermodynamic properties of the liquid which change with pressure and temperature. Heat transfer between the machine and its surroundiings is assumed to be negligible. Apparatus is described for use in several different applications of the method, but principally in the thermometric and null methods. Temperature change has usually been measured by resistance thermometers in various bridge networks. Three types of bridge are discussed, the direct current, the transformer ratio and the hydraulic bridge. Methods of sampling small quantities of the main flow are described for the null method; when the two thermometer pockets are in streams having different velocities, a differential recovery factor has to be applied. Calorimeter design details are given, with a brief review of tests in the U.K. and abroad.
Behaviour of a Cylindrical Shell Subject to Sinusoidal and Shock Couples
Authors: Hedges J. L. , Mills B. 
Published: February 2007

The response of a thin cylindrical shell subject to sinusoidal and shock excitation is predicted using the Rayleigh theory of inextensibility. In the theoretical analysitwo separate cases are considered; in the first the loads are applied at each end of the shell while in the second the loads are applied at one end only. In each case the position of the loads is perfectly general. Experimental verification is provided for the special case of the load and support points being in the horizontal plane through a shell diameter; one end of the shell being supported while the other end is subjected to sinusoidal and shock excitation. The correlation between the experimental and theoretical results indicated that the response of the shell could be predicted from the theory of inextensibility.
Experimental Measurement of the Effect of Heat Flux on Local Heat Transfer Coefficient and Friction Coefficient in an Annulus
Authors: Larkin B. S. 
Published: February 2007

This paper describes a closed-circuit apparatus for the measurement of local heat transfer coefficients from the inner surface and overall friction coefficients for air flowing through an annulus (radius ratio 1.7). Results were obtained for Reynolds numbers from 35 000 to 170 000 for temperature ratios Ti/Tb up to 1.74. A novel type of heater bar was used in order to avoid some of the disadvantages of the more usual designs. The results were very consistent. It was found that the effect of heat flux on the heat transfer coefficient could be eliminated either by the film temperature method using a film temperature coefficient of 0.25 or by including a temperature ratio term ( TiTb)-0.2 in the Nu-Re relationship. Over most of the Reynolds number range the overall friction coefficient did not vary with heat flux.
On the Design of Reinforcement for Openings and Nozzles in thin Spherical Pressure Vessels
Authors: Calladine C. R. 
Published: February 2007

A simple plastic design approach is made to the problem of design of reinforcement for openings in thin spherical pressure vessels. The essence of the approach is to adjust the thickness and shape of the vessel in the vicinity of the opening so that the full limit pressure of the vessel may be carried with relatively little bending action. A novel constant-thickness shallow conical reinforcing pad emerges as a design which satisfies these requirements. The design, which is easily adapted to the reinforcement of nozzles, appears to have several important advantages over conventional designs not only in the plastic range but also in the elastic range, in which stress concentration factors are low. When the internal pressure is steadily increased, the resulting deformation does not effectively alter the ‘conical-spherical’ profile of the vessel, and the action is predominantly ‘membrane’ throughout the elastic, elastic-plastic and plastic ranges. It follows that simple plastic theory gives a good description of the plastic behaviour. This is in sharp contrast with the case of unreinforced nozzles, where plastic bending effects are superseded, as deflections become ‘large’ by membrane effects. Detail of welds, etc., must be designed by conventional procedures.
Effect of Mistuning on the Vibration of Turbo-Machine Blades Induced by Wakes
Authors: Whitehead D. S. 
Published: February 2007

The report gives a theoretical investigation of the effect of blade mistuning on the vibration of the blades induced by wakes in the incident gas flow which rotate relative to the blades in question. An upper limit to the effect of mistuning is found, which shows that the amplitude on one blade may increase by a factor of roughly ½(1 + √ N), where N is the number of blades in the row. This limit is only approached in special and unusual circumstances. In normal circumstances the amplitude will not increase by more than about 20 per cent. It is concluded that blades expected to work under forced vibration conditions should be made as nearly identical as possible. This is in contrast to the situation when flutter may occur, where the effect of mistuning is always favourable.
Design of Turbine Blades Suitable for Supersonic Relative Inlet Velocities and the Investigation of Their Performance in Cascades: Part I-Theory and Design
Authors: Colclough C. D. 
Published: February 2007

Certain applications for turbines require units with a large work output per stage. The whole of the expansion takes place across the nozzles and at inlet to the turbine blades the gas velocity is supersonic. Impulse blading is usually employed with flow turning angles ranging from 90° to 160°. However, advancing steam conditions suggest that the first stages of turbines presently designed with subsonic blading may have to accept increasing heat drops to reduce the steam temperature to the first moving row and to reduce gland losses. Under these conditions blading designed to accept supersonic velocities could be employed. This paper, which deals with blading designed specifically for supersonic flow, is divided into two parts, the first of which outlines the theory and design of the blading. The second part describes tests run on cascades of these blades and discusses the results. In Part I a design method based on inviscid isentropic supersonic vortex flow theory is evolved in which the uniform flow ahead of the blade is transformed into a vortex flow, turned through the required angle and then converted back to uniform flow again at the exit. The blades thus obtained are cusped and a design method has been developed to produce blades with finite leading and trailing edges. Blades designed on this basis were tested in cascade and the results were used to modify the design procedure. The revised design method for non-isentropic conditions incorporating the measured losses and allowable contraction ratio was programmed for a Ferranti Pegasus digital computer and this was used to produce an impulse blade section with a flow turning angle of approximately 137° and capable of accepting an upstream Mach number of 1.285 and a blade inlet Mach number of 1.514.
Pressure Pulsations in Reciprocating Compressor Delivery Systems
Authors: Wallace F. J. 
Published: February 2007

In an earlier paper (1)†, the author discussed the nature of pressure pulsations in suction systems of free-piston gas generators, and in particular various forms of pulsation damping devices. A theoretical approach was based on a simple linear treatment of the system, i.e. (1) regarding all pressure pulsations as small in relation to the mean pressure on which they are superimposed, (2) treating dissipative elements (pipe friction or concentrated restrictions) as having linear pressure drop-velocity relationships about the mean flow condition, and (3) treating all distributed elements as having wave motion in accordance with small wave (2) or acoustic theory (rather than the non-linear finite wave theory (3) (4)). Although the physical conditions in compressor delivery systems are very different from those in gas generator suction systems, a similar theoretical approach, verified by acoustic model tests, has been found both to provide a good insight into the problem, and to give an acceptably accurate quantitative indication of pressure pulsation amplitudes. For this purpose systems have been divided into: (1) lumped impedance systems, (2) distributed impedance systems.