Showing papers in "Archive: Journal of Mechanical Engineering Science 1959-1982 (vols 1-23) in 1963"
TL;DR: In this paper, the general instability of a simply supported cylindrical shell under hydrostatic pressure was analyzed by considering the distribution of stiffness of the frames and stringers separately, taking into account their eccentricity.
Abstract: The general instability of a simply supported cylindrical shell under hydrostatic pressure is analysed by considering the ‘distributed stiffness’ of the frames and stringers separately, taking into account their eccentricity. It is shown that frames on the inside of the shell yield general instability loads about 10–15 per cent greater than frames on the outside of the shell. Stringers are much less effective in stiffening a shell under hydrostatic pressure, and the effect of eccentricity is opposite; outside stringers yield critical loads greater than inside stringers.
188 citations
TL;DR: In this paper, the deformations of uniformly loaded, simply supported beams are derived for a simple creep law of the typewhere is the secondary creep rate, ρ is the applied stress and n is the creep index.
Abstract: The deformations of uniformly loaded, simply supported beams are derived for a simple creep law of the typewhere 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 in...
52 citations
TL;DR: The influence of the radial velocity profile upon turbulent heat transfer is discussed in this article, where it is shown that the presence of nearby stationary planes can considerably reduce the heat transfer in a rotating disc.
Abstract: Experimental investigation of laminar heat transfer from an isolated disc is described, account being taken of simultaneous forced and natural convection. It is concluded that results are correlated well byThe influence of the radial velocity profile upon turbulent heat transfer is discussed. Measurements of the flow beyond the edge of a rotating disc are outlined, and it was found that beyond about 40 per cent of the disc radius from the disc edge the flow closely resembles that in Squire's radial jet, but with a whirl component of velocity. Details of the influence of nearby stationary planes upon the flow and heat transfer from a rotating disc are given; it is shown that the presence of such planes can considerably reduce the heat transfer.
45 citations
TL;DR: In this article, various methods of calculating the natural frequencies of flat rectangular cantilever plates are discussed, and it is shown both analytically and experimentally that relatively simple expressions b...
Abstract: Various methods of calculating the natural frequencies of flat rectangular cantilever plates are discussed, and it is shown both analytically and experimentally that relatively simple expressions b...
38 citations
TL;DR: A fairly lightly damped system with widely spaced natural frequen... as mentioned in this paper, which was designed to permit an initial appraisal to be made of methods of resonance testing, is described in detail in this paper.
Abstract: This paper gives details of apparatus which was designed to permit an initial appraisal to be made of methods of resonance testing. A fairly lightly damped system with widely spaced natural frequen...
33 citations
TL;DR: In this article, the forced vibrations of modes consisting of at least one nodal diameter and an arbitrary number of nodal circles are investigated for the case when the position of the exciting force coincides with a...
Abstract: The forced vibrations of modes consisting of at least one nodal diameter and an arbitrary number of nodal circles are investigated. The case when the position of the exciting force coincides with a...
27 citations
TL;DR: In this article, the method of Kryloff and Bogoliuboff was used to investigate the non-linear oscillation of a system incorporating a Hooke's joint, and it was found that the system ultimately executes a limit cycle of oscillation and that, in certain critical speed ranges, the amplitude of this oscillation is large if the system is lightly damped.
Abstract: The method of Kryloff and Bogoliuboff is used to investigate the non-linear oscillation of a system incorporating*** a Hooke's joint. It is found that the system ultimately executes a limit cycle of oscillation and that, in certain critical speed ranges, the amplitude of this oscillation is large if the system is lightly damped.
26 citations
TL;DR: In this paper, the authors derived rational expressions for the discharge characteristics of square-edged cylindrical-tube orifices having axial lengths of the order of one diameter or greater.
Abstract: Rational expressions for the incompressible discharge characteristics of square-edged cylindrical-tube orifices having axial lengths of the order of one diameter or greater are derived by the application of boundary layer theory to a simplified model of the flow mechanism. The theoretical predictions of discharge coefficient value and of cavitation inception in the case of liquids are shown to accord well with available experimental data. The effects of chamfered and radiused entry are discussed. This new analysis is intended as a step towards the goal of establishing the means of deriving optimal orifice designs in the fields of flow measurement, servomechanisms, fuel injection, pneumatic gauging, and in other domains.
24 citations
TL;DR: Experimental methods are described by means of which the equivalent elastic properties of bars and plates perforated on a square, a square-diagonal or a triangular pitch (or otherwise) may be obtai...
Abstract: Experimental methods are described by means of which the equivalent elastic properties of bars and plates perforated on a square, a square-diagonal or a triangular pitch (or otherwise) may be obtai...
22 citations
20 citations
TL;DR: In this article, fatigue tests at zero mean load have been carried out on copper and nickel-chromium alloy steel plate specimens containing two small coplanar edge cracks and it was found that whether or not a crack grew depended on the value of ρ3l, where ρ is the semi-range of the alternating stress and l is the edge-crack length.
Abstract: Fatigue tests at zero mean load have been carried out on copper and nickel-chromium alloy steel plate specimens containing two small coplanar edge cracks. For a wide range of crack lengths it was found that whether or not a crack grew depended on the value of ρ3l, where ρ is the semi-range of the alternating stress and l is the edge-crack length. If ρ3l is greater than C a crack will grow, if ρ3l is less than C a crack will remain dormant. C had a value of 0·6 for copper and of 5·5 for the alloy steel when ρ was in ton/in2and l in inches.
TL;DR: In this paper, an experimental study is described which shows the elementary "peak-amplitude" technique of resonance testing to great disadvantage, on the basis of which the experimentally determined "modal shapes" are completely misleading.
Abstract: An experimental study is described which shows the elementary ‘peak-amplitude’ technique of resonance testing to great disadvantage. On the basis of that method the experimentally determined ‘modal shapes’ are completely misleading. While the Kennedy and Pancu method would produce acceptable modes it would demand a much greater effort. An alternative technique is described which gives excellent results at the cost of much less labour. While the new method appears to have an added advantage over the Kennedy and Pancu method when there is strong coupling between the modes, it may well prove to be less accurate when there are close natural frequencies.
TL;DR: In this article, the authors compared the theoretical analysis for small-angle mitred bends with the results of a test carried out on a mitred joint subjected to an in-plane bending moment.
Abstract: Experimental results are presented for the stresses caused by internal pressure in thin pipes which are mitred and welded together to form a single mitred bend without any type of elliptical insert at the intersection. The frozen-stress photoelastic technique is used, the models being carefully machined and cemented to form a joint free from welding imperfections. The results are compared with the theoretical analysis for small-angle mitred bends, of Green and Emmerson (I)†. An alternative derivation of this theory is given in Appendix I. Good agreement with the theory is shown for small-angle bends for each of the two thicknesses of pipe used. For larger angles of bend, the agreement is less good. The results of a test carried out on a mitred joint subjected to an in-plane bending moment, are included.
TL;DR: A theoretical balancing technique was proposed by Bishop and Gladwell and an experimental investigation of its usefulness is reported in this paper, where the thin shafts which were used clearly showed the importance of initial bend (as opposed to mass unbalance) as a source of forced vibration.
Abstract: A theoretical balancing technique was proposed by Bishop and Gladwell (***2) and an experimental investigation of its usefulness is reported. Experiments conducted on the laboratory scale were believed necessary before full-scale tests on large industrial rotors (such as alternator rotors) could be properly justified. The thin shafts which were used clearly showed the importance of initial bend (as opposed to mass unbalance) as a source of forced vibration. This required some additions to the original theory, and they formed the subject of Part I of this paper (published in the previous issue of this Journal, March 1963, p. 114). Part II contains an account of the actual experiments and of the test apparatus. It is concluded that the theory is fully borne out on the laboratory scale.
TL;DR: In this article, the authors considered the linearized equations and transfer function for a hydraulic servomechanism and showed that the simple first-order equation is inadequate to explain the behaviour of the device as observed experimentally.
Abstract: 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.
TL;DR: In this paper, the results of experimental work on a two-dimensional model of a supersonic parallel diffuser of the type used to achieve some recompression of a high-temperature jet, though in the present tests a relatively low temperature was employed.
Abstract: This paper reports the results of experimental work on a two-dimensional model of a supersonic parallel diffuser of the type used to achieve some recompression of a high-temperature jet, though in the present tests a relatively low temperature was employed. Visual observations were made of the flow patterns developed in the diffuser, together with corresponding measurements of static pressure distributions and local heat transfer rates, for a range of initial total pressures. The effect of varying the area of the diffuser cross-section, for the same upstream generating nozzle, has also been studied. The static pressure recovery across the diffuser is found to reach a maximum at the transition from a normal shock to a multiple oblique shock system of diffusion. Following a peak value near the diffuser entry, the heat transfer, which generally follows the static pressure distribution, fluctuates about relatively low values in the region of the shock patterns, but rises steadily when the flow becomes subsoni...
TL;DR: In this paper, a method of determining the stress distribution in rotating axially symmetrical systems is presented based on the three-dimensional equilibrium equations and is applicable to turbine wheels of appreciable thickness.
Abstract: A method of determining the stress distribution in rotating axially symmetrical systems is presented. The analysis is based on the three-dimensional equilibrium equations and is applicable to turbine wheels of appreciable thickness for which the thin disc (plane-stress) theory gives only approximate results. A convergent numerical solution using two stress functions has been obtained on a digital computer by ‘relaxing’ two governing equations.
TL;DR: In this article, an extension of a previously published investigation into the natural convection process in a liquid metal (4), using circular tubes closed at their lower ends, operating on the thermosyphon principle of heat transfer.
Abstract: This paper reports an extension of a previously published investigation into the natural convection process in a liquid metal (4), using circular tubes closed at their lower ends, operating on the thermosyphon principle of heat transfer. In this work longer tubes were used than previously and two distinct regimes of flow were observed. At low heating rates the non-dimensional heat transfer coefficient was found to be a linear function of the temperature difference, and the fluid at the lower end of the tube appeared to be stagnant, contributing negligibly to the overall heat transfer process.At higher heat transfer rates, the data followed the general trends of the previously observed flows in a liquid metal, although The Heat Transfer Rates Were At Least 17 Per Cent Less Than With Normal Boundary Layer Flow, and More Dependent Upon The Surface Geometry. This Was Due To Interference Between The Heated Boundary Layer and The Core of Cooler Fluid, and This Caused Violent Oscillations In The Temperature of T...
TL;DR: A technique is explained and illustrated whereby the response of one sub-system of a compound system may be extracted from the measured response of the whole.
Abstract: A technique is explained and illustrated whereby the response of one sub-system of a compound system may be extracted from the measured response of the whole. The system examined consists of two sub-systems, a beam and a concentrated mass, linked by a common co-ordinate at the point of excitation. The results obtained from this composite system are then analysed and the data that are required from a resonance test on the beam alone are extracted.
TL;DR: In this paper, an investigation has been made into the energy loss in thin oil films when these were subjected to high-frequency alternating loads and a qualitative theory is given which goes some way towards explaining the experimental results.
Abstract: Damping Properties of Thin Oil Films Subjected to High-Frequency Alternating LoadsAn investigation has been made into the energy loss in thin oil films when these were subjected to high-frequency alternating loads.Experiments were performed on oil films between two parallel plates when one of them was given a sinusoidal motion relative to the other in a direction normal to the plane of the plates. The frequencies used were in the range 400 to 4000 c/sec.The experiments showed that the energy loss is less than would be expected because of cavitation of the oil film and a qualitative theory is given which goes some way towards explaining the experimental results.
TL;DR: In this article, the circumferential and longitudinal residual stresses present in a tube may be found by measurement of changes in curvature after slitting and layer slicing, and analytical expressions are proposed to find the residual stresses.
Abstract: Analytical expressions are proposed, from which the circumferential and longitudinal residual stresses present in a tube may be found by measurement of changes in curvature after slitting and layer...
TL;DR: In this article, the Navier-Stokes equations of viscous flow are solved using matrix methods, and the use of matrix methods enables considerable simplification and savings in both computer storage and time.
Abstract: The equations of viscous flow, the Navier-Stokes equations, are difficult to solve because they are non-linear, multi-variable, partial differential equations. For isothermal two-dimensional flow three equations have to be solved simultaneously, the momentum equation for each direction and the continuity equation. The usual numerical method is to replace the continuous system with the discrete representation at a number of points by the finite difference approximations to these equations, assuming that the solution to the discrete system approximates and converges with increasing point representation to the continuous solution. An iteration process, whereby the non-linear terms provide corrections to the solution of the linear portion of the equations, would tax many digital computers from the viewpoints of both storage and time.The use of matrix methods discussed in this paper enables considerable simplification and savings in both computer storage and time. Further non-linear terms present no difficulty...
TL;DR: In this article, the analysis of two-dimensional turbulent channel flows is given, and the application of its results to bearing analysis is treated in Part II, where a thorough study of the motion within turbulent films must be made before their characteristics as bearing films can be assessed.
Abstract: 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.
TL;DR: In this article, during a program of transition temperature tests on 6-ft wide plates, strain gauge records, showing the strain field in the plates during fracture, were obtained, and an interpretation of what they mean in terms of the behaviour of the metal when fractured was given.
Abstract: During a programme of transition temperature tests on 6-ft wide plates, strain gauge records, showing the strain field in the plates during fracture, were obtained. This report gives a few typical records and an interpretation of what they mean in terms of the behaviour of the metal when fractured. A possible explanation of how the fracture is self-sustained is also included.
TL;DR: In this article, the theory proposed by Yi-Yuan Yu for determining the stiffness of an ungasketed joint is reconsidered and modified to suit the observed behaviour of metal-to-metal joints and of joints where one or more gaskets are included between mating surfaces of the joint assembly.
Abstract: The mechanism by which broad-faced flanged joints retaining a circular plate exert restraint against the flexure of the plate due to pressure differentials is discussed and studied experimentally.The theory proposed by Yi-Yuan Yu for determining the stiffness of an ungasketted joint is reconsidered and modified to suit the observed behaviour of metal-to-metal joints and of joints where one or more gaskets are included between mating surfaces of the joint assembly. Hence, a more exact method for calculating stiffness factors for such joint assemblies is formulated.Experiments were conducted on a particular design of header to tube-plate assembly and the results used to check the validity of the modified theory.
TL;DR: In this article, the vibrations were considered of a gyroscope mounted on a uniform elastic shaft within two rigid gimbals, and the theory was extended to include a more general practical arrangement in which the shaft is non-uniform.
Abstract: This paper is a sequel to a previous work in which the vibrations were considered of a gyroscope mounted on a uniform elastic shaft within two rigid gimbals. The theory has now been extended to include a more general practical arrangement in which the shaft is non-uniform. Experimental results have also been obtained which confirm the general conclusions of the theory.